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Surgical technique and results
J
THORAC CARDIOVASC SURG 1989;98: 1030-6
Transannular cryoablation of ventricular tachycardia Surgical technique and results Intraoperative mapping and cryoablation of ventricular tachycardia was achieved without ventriculotomy in seven patients, who are a subgroup of the 80 patients undergoing map-directed ablation of ventricular tachycardia over a 9-year period. There were four male and three female patients. Their mean age was 53.6 ± 24.1 years. Coronary artery disease was present in five patients, and two patients had idiopathic ventricular tachycardia. The mean preoperative ejection fraction was 42.4% ± 13.6%. The mean number of ventricular tachycardia morphologies was 1.7 (range 1 to 3). Epicardial mapping was obtained intraoperatively in all seven patients and endocardial data in five of seven patients (71.4%). There were no hospital deaths and no early or late spontaneous recurrence of clinical monomorphic ventricular tachycardia. Nonclinical monomorphic ventricular tachycardia was inducible in two patients postoperatively and both were treated with procainamide. Death occurred late after operation in two patients: One death was related to recurrent nonclinical VT at 8 months and one at 3 months was due to carcinoma of the stomach. These results suggest that the transannular approach is feasible in selected cases, especially when computerized mapping systems with endocardial balloon electrode arrays can be used.
Gerald M. Lawrie, MD,a Antonio Pacifico, MDb (by invitation), and Raj R. Kaushik, MDa (by invitation), Houston, Texas
Most patients with drug-refractory sustained ventricular tachycardia (VT) have advanced coronary disease or dilated cardiomyopathy and are seriously ill. Nonsurgical methods of ablation for which significant clinical experience has been reported are transvenous direct-current electroshock and radiofrequency Iulguration.l-? The results of these techniques have been discouraging, with hospital mortality rates of 6.7% to 11.6% and drug-free cure rates of only 18% to 56%. Therefore direct ablative surgery, guided by preoperative and intraoperative electrophysiologic mapping, remains an important form of therapy. A drug-free cure rate of VT can be achieved in about 90% of patients.v' but a risk of perioperative mortality of 12% to 15% of patients and VT recurrence rate
From the Departments of Surgerya and Medicine (Cardiology)," Baylor College of Medicine and The Methodist Hospital. Houston. Texas. Read at the Sixty-ninth Annual Meetingof The American Association for Thoracic Surgery, Boston, Mass.. May 8-10, 1989. Address for reprints: Gerald M. Lawrie. MD. 6535 Fannin, A900, Houston, TX 77030
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of 10% to 25% is still present." Because perioperative low cardiac output is the most common cause of death after ablative operations, avoidance of ventriculotomy except where indicated for treatment of aneurysmal segments would seem a logical goal. The purpose of this study was to report our experience with intraoperative mapping and surgical ablation of VT without ventriculotomy. Methods Patient characteristics. Between April 1980 and February 1989, 80 patients underwent direct surgical ablation of symptomatic drug-refractory sustained ventricular tachycardia. In 73 patients intraoperative electrophysiologic mapping of the endocardium or ablation of VT, or both, was associated with a ventriculotomy. In the other seven patients, the operations were performed through one or more valve anuli without ventriculotomy. There were four men and three women. The mean age was 53.6 ± 24.1 years. Coronary artery disease was present in five of the seven patients and two patients had idiopathic VT. The mean preoperative ejection fraction was 42.4% ± 13.6%. The mean number of VT morphologies was 1.7 (range I to 3). Electrophysiologic evaluation. All patients underwent preoperative electrophysiologic studies. The details of these techniques have been reported previously.' Surgical technique. All operations were performed during total cardiopulmonary bypass with bicaval cannulation. Intra-
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Transannular cryoablation of VT
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operative mapping was performed during normothermic bypass. Anesthesia was induced and maintained with intravenous narcotic agents in an effort to avoid the antiarrhythmic effects of inhalational agents. Recent experimental data have supported the importance of these clinical observations.P Both epicardial and endocardial mapping of all morphologically distinct tachycardias was attempted. In our initial experience this was performed with sequential positioning of hand-held bipolar electrodes. When the preoperative studies suggested early right ventricular activation, the right ventricular endocardium was also mapped through the tricuspid valve. Multiple sites were recorded on an intraoperative mapping grid. The distance between each site was I to 1.5 em. In the four most recent patients, a custom computerized mapping system was used to record up to 120 epicardial bipolar electrograms from a sock electrode array and up to 120 endocardial bipolar electrograms from a balloon electrode array. In regard to the specific techniques for transannular balloon endocardial mapping, the balloon electrode array was placed through a right atriotomy for right ventricular endocardial mapping with the heart beating. For left ventricular endocardial mapping the aorta was crossclamped and proximal aortic root perfusion begun with a single 12F cannula connected to a cardiopulmonary bypass coronary perfusion system. Flow rates were adjusted to maintain a mean aortic root pressure of70 mm Hg. The balloon electrode array was then inserted through the mitral valve anulus and inflated with warm saline to a mean pressure of 40 mm Hg. Two methods of localization of the balloon within the ventricle have been used. The first relies on measurements based on the fixed dimensions of our balloon electrode array. Because the plastic strips used are inextensible, the interelectrode distance between bipolar pairs in the long axis is always 1.0 cm. Thus the position on the endocardium of any given electrode pair can be measured on the endocardium from either the apex of the ventricle or the mitral or tricuspid anulus. The long axis of the balloon is mounted on a rigid stylet to which the apex and base of the balloon is attached. This enables the distal tip of the balloon to be palpated at the apex of the left ventricle and the coaxial position of the balloon and ventricle to be established. Because the electrodes are arranged as strips, the radial alignment of the balloon in relation to the septum and the anterior, lateral, and inferior walls can be determined, after insertion, at the mitral or tricuspid anulus by noting the position of the strips in relation to standard anatomic landmarks, in particular the plane of the interventricular septum and the commissures of the mitral or tricuspid valves. Furthermore, inflation of the balloon with a noncompressible liquid such as saline enables the distance between strips to be measured at a given volume of inflation. The second method consists of placing one or more pairs of deep intramyocardial pacing wires inserted through the epicardiurs near to the sites of earliest endocardial activation as detected by the balloon array and recording a map during ventricular bipolar pacing. Our experimental data in a series of eight dog experiments have confirmed the accuracy of this technique (unpublished data). Important technical points include deep intramyocardial placement of the wires, a short distance between them «5 mrn), and pacing at the lowest possible threshold voltage. With use of these precautions, good localization of the pacing wire site on the endocardial balloon is obtainable. This technique is facilitated by the almost instanta-
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neous availability of the mapping data from the computer. Mapping is conducted in sinus rhythm and VT. At present the sinus rhythm maps are obtained for research purposes only and have not been used for clinical localization. After completion of mapping in sinus rhythm and VT, the coronary perfusion was discontinued. Cold potassium cardioplegic solution was infused into the aortic root and topical hypothermia was induced. Multiple cryothermic lesions were created by meansofa Valley Lab cryoprobe (Valley Lab, Inc., Boulder Colo.) cooled to - 74 0 C by liquid nitrous oxide and applied for 2 minutes for each lesion. As we! have previously reported, an attempt was made to ablate all tissue within the 0 msec isochrone because the VT may not necessarily arise at the precise site of earliest breakthrough depicted by endocardial mapping. Where indicated, coronary bypass grafts were constructed. The atria were then closed and the operation completed. No attempt was made to reinduce VT in the operating room. All patients underwent postoperative electrophysiologic studies during which VT induction was attempted. The study protocol was the same as that which induced the preoperative arrhythmia but included one additional extrastimulus. Epicardial stimulation was performed from the right ventricular apex at two drive cycle lengths (600 and 400 rnsec), and three or more extrastimuli as well as burst pacing also were used.
Results
Preoperative electrophysiologic studies were performed on all seven patients. All preoperative clinical tachycardias were inducible in the electrophysiology laboratory and were mapped in six patients. One patient (patient 7, Table I) underwent electrophysiologic study, but, after induction of VT, severe angina pectoris and hemodynamic instability prevented mapping. She was taken to the operating room without mapping data being obtained during VT. Some intraoperative mapping in sinus rhythm or VT, or both, was achieved in all patients. Three of the patients had point-to-point mapping of the right ventricular endocardium through the tricuspid valve. One patient had recordings from the left ventricle by a needle electrode, introduced intramurally at the site localized by computerized epicardial mapping, to localize the depth of a focus on the anterior aspect of the basal left ventricle (patient 6, Table I). Four patients had epicardial mapping with the sock electrode array. Endocardial recordings also were obtained with the balloon array. Overall, epicardial and endocardial mapping data were obtained in VT intraoperatively for five of the seven patients. The patient whose condition could not be mapped preoperativley (patient 7) underwent an ablation procedure guided by the results of epicardial mapping of VT only because VT was not inducible during balloon endocardial mapping. A spontaneous nonclinical VT subsequently developed in the postoperative period.
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Lawrie, Pacifico, Kaushik
Table I. Clinical data and surgical techniques for the seven patients who had transannular cryoablation
Patient No.
Age
Sex
64
F
47
M
15
M
4
64
M
5
80
M
6
29
F
7
72
F
2
No. ofVT clinical monomorphic morphologies
EF Pathology
(%)
CAD
50
CAD
30
Idiopathic
65
2
CAD
25
3
CAD
47
Idiopathic
45
CAD
35
2
2
Sites of earliest activation in VT J. Basal RV close to tricuspid valve J. Basal RV septum (clinical) 2. Basal LV septum (nonclinical) J. Basal RV septum
J. Mid-lateral wall LV (clinical): also had polymorphic VT (nonclinical) 1-3. Posterior LV. inferior papillary muscle
I. Basal LV. anterior wall I. Mid-lateral wall LV 2. Basal inferior wall RV
Sites of cryoablation
Anulus used
Other procedures
Inferior wall RV
Tricuspid
CABx3
Posterior basal RV septum (VT NO.2 not trca ted)
Tricuspid
CABx2
Basal RV septum: crista supraventricularis Lateral wall LV
Tricuspid
Excision crista supraventricularis
Mitral
CABx2
Posterior wall LV: inferior papillary muscle Basal LV. anterior wall Lateral wall LV: basal inferior RV
Mitral
MVR: CABx2
Aortic
Mitral
CABx3
EF. Ejection fraction: CAD. coronary artery disease: R V. right ventricle: CAB: coronary artery bypass: LV. left ventricle.
There were no perioperative deaths. At postoperative electrophysiologic studies the one patient (patient 7) with no preoperative or intraoperative endocardial mapping data had inducible nonclinical VT. However, this VT, previously drug refractory, postoperatively became noninducible with procainamide therapy. Another patient (patient 4), who preoperatively had monomorphic and polymorphic VT, had noninducibility of the monomorphic VT but persistent inducible polymorphic VT. This polymorphic VT was made noninducible by procainamide. Another patient (patient 2) had both a right ventricular clinical VT and a left ventricular nonclinical VT
induced preoperatively. He had been operated on early in our experience (October 1984) when nonclinical VT detected preoperatively at the electrophysiologic study was not treated surgically and thus the site of the nonclinical VT on the left side of the septum was not ablated. The clinical VT was noninducible but the nonclinical VT was still inducible postoperatively, became a clinical problem several months later, and necessitated amiodarone therapy. He died of congestive heart failure and a recurrent episode of the nonclinical VT 8 months after operation. Thus the clinical monomorphic VT was cured in all seven patients (100%). Of the seven patients, two were
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discharged from the hospital receiving procainamide for suppression of monomorphic VT, a drug which preoperatively was ineffective. Two patients have died late after operation: one of carcinoma of the stomach (patient 5) 3 months postoperatively and the other of nonclinical VT, myocardial infarction, and congestive heart failure (patient 2) 8 months postoperatively.
Discussion Intraoperative epicardial mapping by means of a sock electrode array and computerized data analysis is a wellestalished technique.v" Sock electrode arrays provide excellent data regarding epicardial activation sequences. .However, because of problems with unpredictable propagation of depolarization through diseased myocardium, endocardial activation sequence data are also
required.v !?
Intraoperative recording of endocardial electrograms has been more difficult. In the early experience in most centers, mapping of the left ventricular endocardium was performed with a hand-held probe inserted through a left ventriculotomy, either anteroapical or inferior.3.11-13 Mapping of the right ventricle without ventriculotomy has always been simpler because of the ease of visualization of the right ventricular cavity through the tricuspid valve and the lack of risk of air embolism. Access to the ventricular septum and right ventricular free wall through the tricuspid valve for intraoperative mapping and VT ablation was used by us in patient 1 in January 1984 to confirm the site of a VT mapped preoperatively to the right side of the basal septum. A hand-held bipolar probe was used. The development of a computerized mapping system has enabled a balloon array with electrodes mounted on plastic strips to be used for both right-sided and left-sided endocardial mapping. Point-to-point mapping is still useful on the right side to locate the site of the His bundle and obtain detailed information before ablation of high septal lesions to avoid heart block. We had considered endocardial mapping by hand through the mitral anulus not to be feasible. Earlier reports of experience with left ventricular mapping by balloon arrays had confirmed their effectiveness. DeBakker and associates!" in 1983 reported experience with 32 patients in whom a balloon array with 32 electrodes was inserted through left ventriculotomy incisions. Fann and colleaguesl- subsequently demonstrated in dogs good correlation between the site of pace mapping and data from a balloon array. Harris," Downar,'? Mickleborough, 18 and their associates, were the first to report the successful clinical use of transatrial transannular balloon insertion.
Transannular cryoablation of VT
1a3 3
Our own clinical experience with balloon endocardial mapping for VT ablation began in January 1987 with an 80-electrode balloon array that was subsequently expanded to 120 electrode pairs. This has been used successfully in 16 patients. A total of 17 patients with VT have undergone computer-assisted mapping of the epicardium or endocardium, or both. Transannular mapping is advantageous because, as pointed out by Harris," Downar, 17 Mickleborough, J 8 and their group, inducibility of the VT and the activation sequences of the VT are not disturbed by a ventriculotomy. Insertion of the balloon through the atrioventricular valve also allows the long axis of the balloon to be aligned with the long axis of the ventricle more readily than through an eccentrically placed ventriculotomy. This is an especially important consideration when the inferior wall of the ventricle is the site of interest. Insertion of a balloon array through an inferior ventriculotomy is not feasible. Although our experience with ablation of VT in both anterior and inferior locations has been good,' intraoperative mapping of inferior sites by hand through an inferior ventriculotomy was more difficult.'? In these patients the transannular approach to mapping and cryoablation of the inferior wall may actually be easier and more reliable. Precise localization of the position of the endocardial electrode array in relation to the endocardium within the ventricle is important. de Bakker I 4 used a prominent bar on the balloon, which could be palpated. Mickleborough and colleagues (personal communication) have used direct current applied to some balloon electrodes to make endocardial burn marks. We tried this method in dogs, but burn marks were found to chordae tendineae in some experiments. We evaluated intraoperative epicardial echocardiography in the laboratory and found it unsatisfactory. Mickleborough's group also has determined the position of the electrode arrays by ventriculotomy with the balloon in place followed by direct visualization of the earliest electrode pair. We have used their method when ventriculotomy is needed and found it a useful adjunct. Despite use of all the techniques described, very precise localization of the position of individual electrode pairs in the intact ventricle is still not easy. Experience with transmural plunge electrodes for recording endocardial data has been reported.v-'' This technique was used in our series instead of a balloon to perform confirmatory mapping in patient 6, in whom transaortic cryoablation of the anterior left ventricular wall was performed. Intraoperative ablation of arrhythmogenic tissue can be achieved by excision,' endocardial resection, II cryoablation,21-24 laser fulguration.P-" laser thermocoagu-
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Lawrie, Pacifico, Kaushik
lation,27.28 or direct-current electroshock administered through balloon electrodes (BESA).29 Because access to the right ventricle is good through the tricuspid valve, excision, endocardial resection, or laser techniques are feasible. The tricuspid valve is relatively inconspicuous and easily retracted. On the other hand, access to the left ventricle is complicated by its posterolateral location in the pericardium and the presence of two large mitral valve leaflets. The fact that two large papillary muscles are attached to chordae shared by both leaflets further complicates exposure. Thus for transannular ablation of left-sided foci we have used cryothermia only. Cryothermia can be applied to the ventricular endocardium through valve leaflets or chordae without functional impairment of valve function.'? A right-angle cryoprobe has facilitated septal cryoablation. Epicardial cryolesions can be applied at the site of pace-localization of the balloon electrodes nearest to areas of earliest activation. Palpation of these lesions within the left ventricle can then assist in localization of the endocardial sites to be ablated. So that lesion size will be adequate, cryothermia is used only after cold cardioplegic arrest of the heart 21.24 and the lesions are applied at -74 C for 2 minutes. Mapping and surgical treatment through the mitral anulus on a beating heart pose a risk of systemic air embolism. To eliminate this risk, we have used aortic root perfusion with warm blood after aortic crossclamping to maintain myocardial perfusion. Root perfusion rates of 200 to 300 mljmin at a pressure of 70 mm Hg maintain normal electrograms, and VT can be induced and mapped with safety. We now routinely use the transannular approach in all cases for endocardial mapping. We 31 also always perform right-sided VT ablation by this route. On the left side we use it for ablation when a ventriculotomy is not required to treat localized left ventricular aneurysms. At present we have limited the use of transannular ablation to patients in whom the VT appears to be arising from a single region. When mapping has demonstrated multiple disparate sites, our preference is to perform a more extensive ablative procedure that usually involves the use of endocardial resection. This policy may be modified as experience with this technique increases. In summary, the transannular route provides ideal conditions to achieve computerized balloon electrode mapping of the ventricular endocardium. Cryoablation of VT also can be achieved by this route. Its use also avoids ventriculotomy, which may in some cases have a detrimental effect on the ability to map or on ventricular 0
function"
Thoracic and Cardiovascular Surgery
REFERENCES 1. Evans GT Jr, Scheinman MM, Zipes DP. et al. The percutaneous cardiac mapping and ablation registry: final summary of results. PACE 1988; II (Pt I): 1621-26. 2. Fontaine G, Tonet JL, Frank R, Rougier I. Clinical experience with fulguration and antiarrhythmic therapy for the treatment of ventricular tachycardia: long-term follow-up of 43 patients. Chest 1989;95:785-97. 3. Krafchek J, Lawrie GM, Roberts R. Magro SA, Wyndham CRe. Surgical ablation of ventricular tachycardia: improved results with a map-directed regional approach. Circulation 1986;73:1239-47. 4. Cox JL Patient selection criteria and results of surgery for refractory ischemic ventricular tachycardia. Circulation 1989;80(Pt 2):1163-77. 5. Hunt G B, Ross DL: Comparison of effects of three anesthetic agents on induction of ventricular tachycardia in a canine model of myocardial infarction. Circulation 1988; 78:221-6. . 6. Gallagher JJ, Kasell JH. Cox JL, Smith WM, Ideker RE. Smith WM. Techniques of intraoperative electrophysiologic mapping. Am J Cardiol 1982;49:221-40. 7. Downar E, Parson ID, Mickleborough LL. Cameron DA. Yao LC, Waxman MB. On-line epicardial mapping of intraoperative ventricular arrhythmias: initiaL clinical experience. J Am Coli Cardiol 1984;4:703-14. 8. Worley SJ, Ideker RE, Mastrototaro J, et al. A new sock electrode for recording epicardial activation from the human heart: one size fits all. PACE 1987;IO(Pt 1):21-31. 9. Spielman SR, Michelson EL, Horowitz LN, Spear JF, Moore EN. The limitations of epicardial mapping as a guide to the surgical therapy of ventricular tachycardia. Circulation 1978;57:666-70. 10. Boineau JP, Cox JL, Rationale for a direct surgical approach to control ventricular arrhythmias. Am J Cardiol 1982;49:381-96. I I. Horowitz LN, Harken AH, Kastor JA, Josephson ME. Ventricular resection guided by epicardial and echocardial mapping for treatment of recurrent ventricular tachycardia. N Engl J Med 1980;302:589-93. 12. Josephson ME, Harken AH, Horowitz LN. Long-term results of endocardial resection for sustained ventricular tachycardia in coronary disease patients. Am Heart J 1982;104:51-7. J 3. Mason JW. Stinson EB. Winkle RA. et al. Surgery for ventricular tachycardia: efficacy of left ventricular aneurysm resection compared with operation guided by electrical activation mapping. Circulation 1982;65:114855. 14. deBakker JMT, Janse MJ, Van Capelle FJL. Durrer D. Endocardial mapping by simultaneous recording of endocardial electrograms during cardiac surgery for ventricular aneurysm. J Am Coli Cardiol 1983;2:947-53. 15. Fann JI, Loeb JM, LoCicero J III, Frederiksen JW, Moran JM, Michaelis LL. Endocardial activation mapping and endocardial pace-mapping using a balloon apparatus. Am J Cardiol 1985;55: 1076-83.
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16. Harris L, Downar E, Mickleborough L, Shaikh N, Parson I. Activation sequence of ventricular tachycardia: endocardial and epicardial mapping studies in the human ventricle. J Am Coli Cardiol 1987;10:1040-7. 17. Downar E, Harris L, Mickleborough LL, Shaikh N, Parson 10. Endocardial mapping of ventricular tachycardia in the intact human ventricle: evidence for reentrant mechanisms. J Am Coli Cardiol 1988; II :783-9 1. 18. Mickleborough LL, Harris L, Downar E, Parson I,GrayG. A new intraoperative approach for endocardial mapping of ventricular tachycardia. J THORAC CARDIOY ASC SURG 1988;95:271-80. 19. Miller JM, Kienzle MG, Harken AH, Josephson ME. Subendocardial resection for ventricular tachycardia: predictors of surgical success. Circulation 1984;70:624-31. 20. Cox JL. Intraoperative computerized mapping techniques. Do they help us to treat our patients better surgically? In: Brugada P, Wellens HJJ,eds. Cardiac arrhythmias. Where to go from here? Mount Kisko, New York: Futura, 1987: 613-37. 21. Caceres J, Werner P, Jazayeri M, Akhtar M, Tchou P. Efficacy of cryosurgery alone for refractory monomorphic sustained ventricular tachycardia due to inferior wall infarction. J Am Coli Cardiol 1988:11:1254-9. 22. Markovitz LJ, Frame LH, Josephson ME, Hargrove we III. Cardiac cryolesions: factors affecting their size and a means of monitoring their formation. Ann Thorac Surg 1988;46:531-5. 23. Hunt GB, Chard RB, Johnson DC, Ross DL. Comparison of early and late dimensions and arrhythmogenicity of cryolesions in the normothermic canine heart. J THORAC CARDIOYASC SURG 1989;97:313-8. 24. Caceres J, Akhtar M, Werner P, et al. Cryoablation of refractory sustained ventricular tachycardia due to coronary artery disease. Am J Cardiol 1989;63:296-300. 25. Ciccone J, Saksena S, Pantopoulos D. Comparative efficacy of continuous and pulsed argon laser ablation of human diseased ventricle. PACE 1986;9:697-704. 26. Saksena S, Hussain M, Gielchinsky I, Gadhoke A, Pantopoulos D. Intraoperative mapping-guided argon laser ablation of malignant ventricular tachycardia. Am J Cardiol 1987;59:78-83. 27. Selle JG, Svenson RH, Sealy WC, et al. Successful clinical laser ablation of ventricular tachycardia: a promising new therapeutic method. Ann Thorac Surg 1986;42:380-4. 28. Gallagher JJ, Selle JG, Svenson RH, et al. Surgical treatment of arrhythmias. Am J Cardiol 1988;61:27A-44A. 29-, MickJeborough LL, Wilson GJ, Harris L, Tashiro T, Parson I, Gray G. Balloon electric shock ablation: effects on ventricular structure, function, and electrophysiology. J THORAC CARDIOYASC SURG 1989;97: 135-46. 30. Guiraudon G M, Guiraudon CM, McLellan DG, MacDonald JL. Mitral valve function after cryoablation of the posterior papillary muscle in the dog. Ann Thorac Surg 1989;47:872-6. 31. Lawrie G M, Pacifico A, Kaushik R. Results of direct sur-
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gical ablation of ventricular tachycardia not due to chemic heart disease. Ann Surg 1989;209:713-27.
IS-
Discussion Dr. Gerard Guiraudon (London, Ontario. Canada). I concur with the authors in recommending cardiac mapping and surgical electrophysiologic intervention on the intact ventricle in patients without associated coronary artery disease or in patients with ischemic heart disease not associated with discrete fibrotic scar. In our laboratory, we have found that (I) endocardial cryoablation through the mitral valve orifice is feasible; (2) extensive cryoablation of the posterior papillary muscle is not associated with mitral valve regurgitation; and (3) extensive transmural cryoablation of the left ventricular apex is not associated with aneurysmal scar or left ventricular dysfunction. In our clinical practice, we have used endocardial cryoablation combined with epicardial cryoablation in six patients with ventricular arrhythmia not associated with coronary artery disease. Since the pioneering work of the Amsterdam school with deBakker, Janse, and their colleagues, as well as many other groups, endocardial mapping is feasible on the intact ventricle through either the mitral or the aortic valve orifice. As early as 1982, we were fortunate to map the intact heart, in patients, using the Amsterdam balloon. The potential advantages of this approach should be (1) intraoperative mapping of all clinical and nonclinical arrhythmias; (2) improved surgical efficacy; and (3) decreased surgical risk. A larger clinical experience is required to document these hypotheses, although current results encourage each of us to use such an approach whenever possible. Dr. Lawrie, which patients with coronary artery disease seem the ideal candidate? What is your policy for patients with intracavitary thrombus? Which patients would be considered for sequential endocardial cryoablation on the beating heart using a similar technique? Dr. Lawrie. Thank you for your kind remarks. Regarding patient selection, I believe that, with more experience with the anatomy and development of some other cryoprobes, cryoablation will be feasible in all patients in whom a ventriculotomy is not required for therapeutic reasons. The two main reasons at the moment that I see for making a ventriculotomy are (1) to take care of an aneurysm that is of significant size in terms of the patient's cardiac function and (2) to deal with multiple disparate foci, that is, several different areas around the ventricle. This condition occurs particularly in patients with ischemic heart disease. Endocardial resection is a quick and simple way of dealing with that, and I think it is still easier to do endocardial resection through the ventriculotomy. We have not tried transannular endocardial resection yet. In regard to the clot problem, we have taken the precaution of doing the left-sided mapping with the aorta crossclamped. We are thus not unduly concerned about dislodging clot with the balloon, and it is possible to inspect the interior of the apex of the left ventricle through the mitral valve. I think we have the flexibility there to make a decision intraoperatively either to continue the operation through the anulus or go to a ventriculotomy. Regarding sequential normothermic cryoablation, our earlier
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Lawrie, Pacifico. Kaushik
experience with one or two patients who had a failure after normothermic cryoablation led us to routinely perform cryoablation only on the arrested cooled myocardium. We have not used the technique of sequential endocardial ablation. I think the work of Gallagher and Dr. Selle and his group on thermocoagulation is interesting. We are watching that work with great interest because if that technique proves to be as effective as cryoablation, then certainly that would be possible to perform on a warm beating heart. Dr. Jay G. Selle (Charlotte. NiC]. Our experience would agree with Dr. Lawrie's in that our operative mortality primarily involves the patients with diffuse severe ventricular impairment, that is, preoperative ejection fractions of less than 25% and no distinct left ventricular aneurysm. Survival in this group will possibly benefit by avoiding a ventriculotomy, although probably at the expense oflimiting endocardial exposure. In the occasional case requiring ablation of the right side of the septum, we will certainly use Dr. Lawrie's right-sided transannular approach. We have additionally noted a significantly higher morbidity and mortality resulting from pulmonary insufficiency in patients who have been on prolonged amiodarone therapy before the operation. Have you noted this problem of postoperative pulmonary insufficiency due to preoperative amiodarone therapy? Dr. Lawrie. Yes, we have. We have been looking at our amiodarone data in considerable detail. We found that there is a very serious risk of mortality in patients who have been on longterm, moderately high-dose amiodarone within 60 days of operation who have an ejection fraction below 35%. They are the group that seem to be at greatest risk. Of the patients who died, several of them died with low cardiac ouptut and severe adult respiratory distress syndrome. The data from Birmingham, Alabama, also support the view that amiodarone is a serious risk to these patients if they are receiving a significant dosage in the preoperative period. Dr. Selle. Ventricular mapping before the computer was inadequate. It was difficult if not impossible to mentally assimilate the data necessary to understand the wave fronts of reentry activity so eloquently and rapidly displayed by computer. However, I believe there is still an important role for the oldfashioned single hand-held probe technique of data acquisition and that both methods, the hand-held probe and the computer, are necessary in most cases. Spatial resolution of mapped sites can be much more precise with the hand-held probe than is possible with the computer array of multiple electrodes that are usually positioned I em or
The Journal of Thoracic and Cardiovascular Surgery
more apart. This precise spatial resolution is necessary, at least in our hands, to be able to truly localize the area of myocardium responsible for the initiation of each form of VT, for example, to determine whether that area of substrate is endocardial, intramural, or epicardial in depth. We have encountered epicardial VT in 10 of 43 patients, almost 25% of our cases. Furthermore, nine of these 10 patients had inferior infarcts without ventricular aneurysms. This is a subgroup in whom the rate of failure is high when conventional endocardial ablative procedures are used alone. I have two interrelated questions: Do you use the computer mapping system exclusively or do you agree that there is still a role for the hand-held probe method for precise data acquisition? Have you encountered examples of epicardial VT? Dr. Lawrie. Yes, we certainly have. This is why we gave up epicardial mapping with a hand-held probe, because the time required led to very long pump times and in our analyses we found that was a significant risk for mortality. With the computer it really adds nothing to the operation to do complete epicardial mapping in sinus rhythm and VT. We have actually had a number of patients with early epicardial breakthrough, and those data led us in a couple of our patients, both with inferior foci, to perform their entireVT operation as an epicardial operation. I think the concept that all VT arises from the endocardium is inaccurate and that we should continue to look at epicardial and endocardial mapping. I think it is extremely important to have both the hand-held probe and the computer available if for no other reason than that these computers are still basically homemade complex devices. So far we haven't had a problem, but one never knows when they are not going to work properly. I think the degree of accuracy is going to increase. It is correct that at the moment there is a I em electrode distance. However, our philosophy has been, even with the hand-held probes, to ablate all the area within the zero isochrone; even with precise mapping, we still have difficulty in working out whether the breakthrough, which is what we are recording on the endocardium, is in fact the site of origin or whether, as deBakker and others have shown, we are looking at a point where something has propogated over a distance of I to 3 em and then broken through the endocardium. Our next step is to double the electrode density of our endocardial balloon. We're hopeful that that will get us closer. Then finally we will use a plate with 50 or 60 points on it to try to get some information on these mechanisms. But I think it is very important to have facility with both techniques.
THORAC CARDIOVASC SURG 1989;98: 1030-6
Transannular cryoablation of ventricular tachycardia Surgical technique and results Intraoperative mapping and cryoablation of ventricular tachycardia was achieved without ventriculotomy in seven patients, who are a subgroup of the 80 patients undergoing map-directed ablation of ventricular tachycardia over a 9-year period. There were four male and three female patients. Their mean age was 53.6 ± 24.1 years. Coronary artery disease was present in five patients, and two patients had idiopathic ventricular tachycardia. The mean preoperative ejection fraction was 42.4% ± 13.6%. The mean number of ventricular tachycardia morphologies was 1.7 (range 1 to 3). Epicardial mapping was obtained intraoperatively in all seven patients and endocardial data in five of seven patients (71.4%). There were no hospital deaths and no early or late spontaneous recurrence of clinical monomorphic ventricular tachycardia. Nonclinical monomorphic ventricular tachycardia was inducible in two patients postoperatively and both were treated with procainamide. Death occurred late after operation in two patients: One death was related to recurrent nonclinical VT at 8 months and one at 3 months was due to carcinoma of the stomach. These results suggest that the transannular approach is feasible in selected cases, especially when computerized mapping systems with endocardial balloon electrode arrays can be used.
Gerald M. Lawrie, MD,a Antonio Pacifico, MDb (by invitation), and Raj R. Kaushik, MDa (by invitation), Houston, Texas
Most patients with drug-refractory sustained ventricular tachycardia (VT) have advanced coronary disease or dilated cardiomyopathy and are seriously ill. Nonsurgical methods of ablation for which significant clinical experience has been reported are transvenous direct-current electroshock and radiofrequency Iulguration.l-? The results of these techniques have been discouraging, with hospital mortality rates of 6.7% to 11.6% and drug-free cure rates of only 18% to 56%. Therefore direct ablative surgery, guided by preoperative and intraoperative electrophysiologic mapping, remains an important form of therapy. A drug-free cure rate of VT can be achieved in about 90% of patients.v' but a risk of perioperative mortality of 12% to 15% of patients and VT recurrence rate
From the Departments of Surgerya and Medicine (Cardiology)," Baylor College of Medicine and The Methodist Hospital. Houston. Texas. Read at the Sixty-ninth Annual Meetingof The American Association for Thoracic Surgery, Boston, Mass.. May 8-10, 1989. Address for reprints: Gerald M. Lawrie. MD. 6535 Fannin, A900, Houston, TX 77030
12/6/16332
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of 10% to 25% is still present." Because perioperative low cardiac output is the most common cause of death after ablative operations, avoidance of ventriculotomy except where indicated for treatment of aneurysmal segments would seem a logical goal. The purpose of this study was to report our experience with intraoperative mapping and surgical ablation of VT without ventriculotomy. Methods Patient characteristics. Between April 1980 and February 1989, 80 patients underwent direct surgical ablation of symptomatic drug-refractory sustained ventricular tachycardia. In 73 patients intraoperative electrophysiologic mapping of the endocardium or ablation of VT, or both, was associated with a ventriculotomy. In the other seven patients, the operations were performed through one or more valve anuli without ventriculotomy. There were four men and three women. The mean age was 53.6 ± 24.1 years. Coronary artery disease was present in five of the seven patients and two patients had idiopathic VT. The mean preoperative ejection fraction was 42.4% ± 13.6%. The mean number of VT morphologies was 1.7 (range I to 3). Electrophysiologic evaluation. All patients underwent preoperative electrophysiologic studies. The details of these techniques have been reported previously.' Surgical technique. All operations were performed during total cardiopulmonary bypass with bicaval cannulation. Intra-
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Transannular cryoablation of VT
December 1989
operative mapping was performed during normothermic bypass. Anesthesia was induced and maintained with intravenous narcotic agents in an effort to avoid the antiarrhythmic effects of inhalational agents. Recent experimental data have supported the importance of these clinical observations.P Both epicardial and endocardial mapping of all morphologically distinct tachycardias was attempted. In our initial experience this was performed with sequential positioning of hand-held bipolar electrodes. When the preoperative studies suggested early right ventricular activation, the right ventricular endocardium was also mapped through the tricuspid valve. Multiple sites were recorded on an intraoperative mapping grid. The distance between each site was I to 1.5 em. In the four most recent patients, a custom computerized mapping system was used to record up to 120 epicardial bipolar electrograms from a sock electrode array and up to 120 endocardial bipolar electrograms from a balloon electrode array. In regard to the specific techniques for transannular balloon endocardial mapping, the balloon electrode array was placed through a right atriotomy for right ventricular endocardial mapping with the heart beating. For left ventricular endocardial mapping the aorta was crossclamped and proximal aortic root perfusion begun with a single 12F cannula connected to a cardiopulmonary bypass coronary perfusion system. Flow rates were adjusted to maintain a mean aortic root pressure of70 mm Hg. The balloon electrode array was then inserted through the mitral valve anulus and inflated with warm saline to a mean pressure of 40 mm Hg. Two methods of localization of the balloon within the ventricle have been used. The first relies on measurements based on the fixed dimensions of our balloon electrode array. Because the plastic strips used are inextensible, the interelectrode distance between bipolar pairs in the long axis is always 1.0 cm. Thus the position on the endocardium of any given electrode pair can be measured on the endocardium from either the apex of the ventricle or the mitral or tricuspid anulus. The long axis of the balloon is mounted on a rigid stylet to which the apex and base of the balloon is attached. This enables the distal tip of the balloon to be palpated at the apex of the left ventricle and the coaxial position of the balloon and ventricle to be established. Because the electrodes are arranged as strips, the radial alignment of the balloon in relation to the septum and the anterior, lateral, and inferior walls can be determined, after insertion, at the mitral or tricuspid anulus by noting the position of the strips in relation to standard anatomic landmarks, in particular the plane of the interventricular septum and the commissures of the mitral or tricuspid valves. Furthermore, inflation of the balloon with a noncompressible liquid such as saline enables the distance between strips to be measured at a given volume of inflation. The second method consists of placing one or more pairs of deep intramyocardial pacing wires inserted through the epicardiurs near to the sites of earliest endocardial activation as detected by the balloon array and recording a map during ventricular bipolar pacing. Our experimental data in a series of eight dog experiments have confirmed the accuracy of this technique (unpublished data). Important technical points include deep intramyocardial placement of the wires, a short distance between them «5 mrn), and pacing at the lowest possible threshold voltage. With use of these precautions, good localization of the pacing wire site on the endocardial balloon is obtainable. This technique is facilitated by the almost instanta-
10 3 1
neous availability of the mapping data from the computer. Mapping is conducted in sinus rhythm and VT. At present the sinus rhythm maps are obtained for research purposes only and have not been used for clinical localization. After completion of mapping in sinus rhythm and VT, the coronary perfusion was discontinued. Cold potassium cardioplegic solution was infused into the aortic root and topical hypothermia was induced. Multiple cryothermic lesions were created by meansofa Valley Lab cryoprobe (Valley Lab, Inc., Boulder Colo.) cooled to - 74 0 C by liquid nitrous oxide and applied for 2 minutes for each lesion. As we! have previously reported, an attempt was made to ablate all tissue within the 0 msec isochrone because the VT may not necessarily arise at the precise site of earliest breakthrough depicted by endocardial mapping. Where indicated, coronary bypass grafts were constructed. The atria were then closed and the operation completed. No attempt was made to reinduce VT in the operating room. All patients underwent postoperative electrophysiologic studies during which VT induction was attempted. The study protocol was the same as that which induced the preoperative arrhythmia but included one additional extrastimulus. Epicardial stimulation was performed from the right ventricular apex at two drive cycle lengths (600 and 400 rnsec), and three or more extrastimuli as well as burst pacing also were used.
Results
Preoperative electrophysiologic studies were performed on all seven patients. All preoperative clinical tachycardias were inducible in the electrophysiology laboratory and were mapped in six patients. One patient (patient 7, Table I) underwent electrophysiologic study, but, after induction of VT, severe angina pectoris and hemodynamic instability prevented mapping. She was taken to the operating room without mapping data being obtained during VT. Some intraoperative mapping in sinus rhythm or VT, or both, was achieved in all patients. Three of the patients had point-to-point mapping of the right ventricular endocardium through the tricuspid valve. One patient had recordings from the left ventricle by a needle electrode, introduced intramurally at the site localized by computerized epicardial mapping, to localize the depth of a focus on the anterior aspect of the basal left ventricle (patient 6, Table I). Four patients had epicardial mapping with the sock electrode array. Endocardial recordings also were obtained with the balloon array. Overall, epicardial and endocardial mapping data were obtained in VT intraoperatively for five of the seven patients. The patient whose condition could not be mapped preoperativley (patient 7) underwent an ablation procedure guided by the results of epicardial mapping of VT only because VT was not inducible during balloon endocardial mapping. A spontaneous nonclinical VT subsequently developed in the postoperative period.
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Lawrie, Pacifico, Kaushik
Table I. Clinical data and surgical techniques for the seven patients who had transannular cryoablation
Patient No.
Age
Sex
64
F
47
M
15
M
4
64
M
5
80
M
6
29
F
7
72
F
2
No. ofVT clinical monomorphic morphologies
EF Pathology
(%)
CAD
50
CAD
30
Idiopathic
65
2
CAD
25
3
CAD
47
Idiopathic
45
CAD
35
2
2
Sites of earliest activation in VT J. Basal RV close to tricuspid valve J. Basal RV septum (clinical) 2. Basal LV septum (nonclinical) J. Basal RV septum
J. Mid-lateral wall LV (clinical): also had polymorphic VT (nonclinical) 1-3. Posterior LV. inferior papillary muscle
I. Basal LV. anterior wall I. Mid-lateral wall LV 2. Basal inferior wall RV
Sites of cryoablation
Anulus used
Other procedures
Inferior wall RV
Tricuspid
CABx3
Posterior basal RV septum (VT NO.2 not trca ted)
Tricuspid
CABx2
Basal RV septum: crista supraventricularis Lateral wall LV
Tricuspid
Excision crista supraventricularis
Mitral
CABx2
Posterior wall LV: inferior papillary muscle Basal LV. anterior wall Lateral wall LV: basal inferior RV
Mitral
MVR: CABx2
Aortic
Mitral
CABx3
EF. Ejection fraction: CAD. coronary artery disease: R V. right ventricle: CAB: coronary artery bypass: LV. left ventricle.
There were no perioperative deaths. At postoperative electrophysiologic studies the one patient (patient 7) with no preoperative or intraoperative endocardial mapping data had inducible nonclinical VT. However, this VT, previously drug refractory, postoperatively became noninducible with procainamide therapy. Another patient (patient 4), who preoperatively had monomorphic and polymorphic VT, had noninducibility of the monomorphic VT but persistent inducible polymorphic VT. This polymorphic VT was made noninducible by procainamide. Another patient (patient 2) had both a right ventricular clinical VT and a left ventricular nonclinical VT
induced preoperatively. He had been operated on early in our experience (October 1984) when nonclinical VT detected preoperatively at the electrophysiologic study was not treated surgically and thus the site of the nonclinical VT on the left side of the septum was not ablated. The clinical VT was noninducible but the nonclinical VT was still inducible postoperatively, became a clinical problem several months later, and necessitated amiodarone therapy. He died of congestive heart failure and a recurrent episode of the nonclinical VT 8 months after operation. Thus the clinical monomorphic VT was cured in all seven patients (100%). Of the seven patients, two were
Volume 98 Number 6 December 1989
discharged from the hospital receiving procainamide for suppression of monomorphic VT, a drug which preoperatively was ineffective. Two patients have died late after operation: one of carcinoma of the stomach (patient 5) 3 months postoperatively and the other of nonclinical VT, myocardial infarction, and congestive heart failure (patient 2) 8 months postoperatively.
Discussion Intraoperative epicardial mapping by means of a sock electrode array and computerized data analysis is a wellestalished technique.v" Sock electrode arrays provide excellent data regarding epicardial activation sequences. .However, because of problems with unpredictable propagation of depolarization through diseased myocardium, endocardial activation sequence data are also
required.v !?
Intraoperative recording of endocardial electrograms has been more difficult. In the early experience in most centers, mapping of the left ventricular endocardium was performed with a hand-held probe inserted through a left ventriculotomy, either anteroapical or inferior.3.11-13 Mapping of the right ventricle without ventriculotomy has always been simpler because of the ease of visualization of the right ventricular cavity through the tricuspid valve and the lack of risk of air embolism. Access to the ventricular septum and right ventricular free wall through the tricuspid valve for intraoperative mapping and VT ablation was used by us in patient 1 in January 1984 to confirm the site of a VT mapped preoperatively to the right side of the basal septum. A hand-held bipolar probe was used. The development of a computerized mapping system has enabled a balloon array with electrodes mounted on plastic strips to be used for both right-sided and left-sided endocardial mapping. Point-to-point mapping is still useful on the right side to locate the site of the His bundle and obtain detailed information before ablation of high septal lesions to avoid heart block. We had considered endocardial mapping by hand through the mitral anulus not to be feasible. Earlier reports of experience with left ventricular mapping by balloon arrays had confirmed their effectiveness. DeBakker and associates!" in 1983 reported experience with 32 patients in whom a balloon array with 32 electrodes was inserted through left ventriculotomy incisions. Fann and colleaguesl- subsequently demonstrated in dogs good correlation between the site of pace mapping and data from a balloon array. Harris," Downar,'? Mickleborough, 18 and their associates, were the first to report the successful clinical use of transatrial transannular balloon insertion.
Transannular cryoablation of VT
1a3 3
Our own clinical experience with balloon endocardial mapping for VT ablation began in January 1987 with an 80-electrode balloon array that was subsequently expanded to 120 electrode pairs. This has been used successfully in 16 patients. A total of 17 patients with VT have undergone computer-assisted mapping of the epicardium or endocardium, or both. Transannular mapping is advantageous because, as pointed out by Harris," Downar, 17 Mickleborough, J 8 and their group, inducibility of the VT and the activation sequences of the VT are not disturbed by a ventriculotomy. Insertion of the balloon through the atrioventricular valve also allows the long axis of the balloon to be aligned with the long axis of the ventricle more readily than through an eccentrically placed ventriculotomy. This is an especially important consideration when the inferior wall of the ventricle is the site of interest. Insertion of a balloon array through an inferior ventriculotomy is not feasible. Although our experience with ablation of VT in both anterior and inferior locations has been good,' intraoperative mapping of inferior sites by hand through an inferior ventriculotomy was more difficult.'? In these patients the transannular approach to mapping and cryoablation of the inferior wall may actually be easier and more reliable. Precise localization of the position of the endocardial electrode array in relation to the endocardium within the ventricle is important. de Bakker I 4 used a prominent bar on the balloon, which could be palpated. Mickleborough and colleagues (personal communication) have used direct current applied to some balloon electrodes to make endocardial burn marks. We tried this method in dogs, but burn marks were found to chordae tendineae in some experiments. We evaluated intraoperative epicardial echocardiography in the laboratory and found it unsatisfactory. Mickleborough's group also has determined the position of the electrode arrays by ventriculotomy with the balloon in place followed by direct visualization of the earliest electrode pair. We have used their method when ventriculotomy is needed and found it a useful adjunct. Despite use of all the techniques described, very precise localization of the position of individual electrode pairs in the intact ventricle is still not easy. Experience with transmural plunge electrodes for recording endocardial data has been reported.v-'' This technique was used in our series instead of a balloon to perform confirmatory mapping in patient 6, in whom transaortic cryoablation of the anterior left ventricular wall was performed. Intraoperative ablation of arrhythmogenic tissue can be achieved by excision,' endocardial resection, II cryoablation,21-24 laser fulguration.P-" laser thermocoagu-
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Lawrie, Pacifico, Kaushik
lation,27.28 or direct-current electroshock administered through balloon electrodes (BESA).29 Because access to the right ventricle is good through the tricuspid valve, excision, endocardial resection, or laser techniques are feasible. The tricuspid valve is relatively inconspicuous and easily retracted. On the other hand, access to the left ventricle is complicated by its posterolateral location in the pericardium and the presence of two large mitral valve leaflets. The fact that two large papillary muscles are attached to chordae shared by both leaflets further complicates exposure. Thus for transannular ablation of left-sided foci we have used cryothermia only. Cryothermia can be applied to the ventricular endocardium through valve leaflets or chordae without functional impairment of valve function.'? A right-angle cryoprobe has facilitated septal cryoablation. Epicardial cryolesions can be applied at the site of pace-localization of the balloon electrodes nearest to areas of earliest activation. Palpation of these lesions within the left ventricle can then assist in localization of the endocardial sites to be ablated. So that lesion size will be adequate, cryothermia is used only after cold cardioplegic arrest of the heart 21.24 and the lesions are applied at -74 C for 2 minutes. Mapping and surgical treatment through the mitral anulus on a beating heart pose a risk of systemic air embolism. To eliminate this risk, we have used aortic root perfusion with warm blood after aortic crossclamping to maintain myocardial perfusion. Root perfusion rates of 200 to 300 mljmin at a pressure of 70 mm Hg maintain normal electrograms, and VT can be induced and mapped with safety. We now routinely use the transannular approach in all cases for endocardial mapping. We 31 also always perform right-sided VT ablation by this route. On the left side we use it for ablation when a ventriculotomy is not required to treat localized left ventricular aneurysms. At present we have limited the use of transannular ablation to patients in whom the VT appears to be arising from a single region. When mapping has demonstrated multiple disparate sites, our preference is to perform a more extensive ablative procedure that usually involves the use of endocardial resection. This policy may be modified as experience with this technique increases. In summary, the transannular route provides ideal conditions to achieve computerized balloon electrode mapping of the ventricular endocardium. Cryoablation of VT also can be achieved by this route. Its use also avoids ventriculotomy, which may in some cases have a detrimental effect on the ability to map or on ventricular 0
function"
Thoracic and Cardiovascular Surgery
REFERENCES 1. Evans GT Jr, Scheinman MM, Zipes DP. et al. The percutaneous cardiac mapping and ablation registry: final summary of results. PACE 1988; II (Pt I): 1621-26. 2. Fontaine G, Tonet JL, Frank R, Rougier I. Clinical experience with fulguration and antiarrhythmic therapy for the treatment of ventricular tachycardia: long-term follow-up of 43 patients. Chest 1989;95:785-97. 3. Krafchek J, Lawrie GM, Roberts R. Magro SA, Wyndham CRe. Surgical ablation of ventricular tachycardia: improved results with a map-directed regional approach. Circulation 1986;73:1239-47. 4. Cox JL Patient selection criteria and results of surgery for refractory ischemic ventricular tachycardia. Circulation 1989;80(Pt 2):1163-77. 5. Hunt G B, Ross DL: Comparison of effects of three anesthetic agents on induction of ventricular tachycardia in a canine model of myocardial infarction. Circulation 1988; 78:221-6. . 6. Gallagher JJ, Kasell JH. Cox JL, Smith WM, Ideker RE. Smith WM. Techniques of intraoperative electrophysiologic mapping. Am J Cardiol 1982;49:221-40. 7. Downar E, Parson ID, Mickleborough LL. Cameron DA. Yao LC, Waxman MB. On-line epicardial mapping of intraoperative ventricular arrhythmias: initiaL clinical experience. J Am Coli Cardiol 1984;4:703-14. 8. Worley SJ, Ideker RE, Mastrototaro J, et al. A new sock electrode for recording epicardial activation from the human heart: one size fits all. PACE 1987;IO(Pt 1):21-31. 9. Spielman SR, Michelson EL, Horowitz LN, Spear JF, Moore EN. The limitations of epicardial mapping as a guide to the surgical therapy of ventricular tachycardia. Circulation 1978;57:666-70. 10. Boineau JP, Cox JL, Rationale for a direct surgical approach to control ventricular arrhythmias. Am J Cardiol 1982;49:381-96. I I. Horowitz LN, Harken AH, Kastor JA, Josephson ME. Ventricular resection guided by epicardial and echocardial mapping for treatment of recurrent ventricular tachycardia. N Engl J Med 1980;302:589-93. 12. Josephson ME, Harken AH, Horowitz LN. Long-term results of endocardial resection for sustained ventricular tachycardia in coronary disease patients. Am Heart J 1982;104:51-7. J 3. Mason JW. Stinson EB. Winkle RA. et al. Surgery for ventricular tachycardia: efficacy of left ventricular aneurysm resection compared with operation guided by electrical activation mapping. Circulation 1982;65:114855. 14. deBakker JMT, Janse MJ, Van Capelle FJL. Durrer D. Endocardial mapping by simultaneous recording of endocardial electrograms during cardiac surgery for ventricular aneurysm. J Am Coli Cardiol 1983;2:947-53. 15. Fann JI, Loeb JM, LoCicero J III, Frederiksen JW, Moran JM, Michaelis LL. Endocardial activation mapping and endocardial pace-mapping using a balloon apparatus. Am J Cardiol 1985;55: 1076-83.
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16. Harris L, Downar E, Mickleborough L, Shaikh N, Parson I. Activation sequence of ventricular tachycardia: endocardial and epicardial mapping studies in the human ventricle. J Am Coli Cardiol 1987;10:1040-7. 17. Downar E, Harris L, Mickleborough LL, Shaikh N, Parson 10. Endocardial mapping of ventricular tachycardia in the intact human ventricle: evidence for reentrant mechanisms. J Am Coli Cardiol 1988; II :783-9 1. 18. Mickleborough LL, Harris L, Downar E, Parson I,GrayG. A new intraoperative approach for endocardial mapping of ventricular tachycardia. J THORAC CARDIOY ASC SURG 1988;95:271-80. 19. Miller JM, Kienzle MG, Harken AH, Josephson ME. Subendocardial resection for ventricular tachycardia: predictors of surgical success. Circulation 1984;70:624-31. 20. Cox JL. Intraoperative computerized mapping techniques. Do they help us to treat our patients better surgically? In: Brugada P, Wellens HJJ,eds. Cardiac arrhythmias. Where to go from here? Mount Kisko, New York: Futura, 1987: 613-37. 21. Caceres J, Werner P, Jazayeri M, Akhtar M, Tchou P. Efficacy of cryosurgery alone for refractory monomorphic sustained ventricular tachycardia due to inferior wall infarction. J Am Coli Cardiol 1988:11:1254-9. 22. Markovitz LJ, Frame LH, Josephson ME, Hargrove we III. Cardiac cryolesions: factors affecting their size and a means of monitoring their formation. Ann Thorac Surg 1988;46:531-5. 23. Hunt GB, Chard RB, Johnson DC, Ross DL. Comparison of early and late dimensions and arrhythmogenicity of cryolesions in the normothermic canine heart. J THORAC CARDIOYASC SURG 1989;97:313-8. 24. Caceres J, Akhtar M, Werner P, et al. Cryoablation of refractory sustained ventricular tachycardia due to coronary artery disease. Am J Cardiol 1989;63:296-300. 25. Ciccone J, Saksena S, Pantopoulos D. Comparative efficacy of continuous and pulsed argon laser ablation of human diseased ventricle. PACE 1986;9:697-704. 26. Saksena S, Hussain M, Gielchinsky I, Gadhoke A, Pantopoulos D. Intraoperative mapping-guided argon laser ablation of malignant ventricular tachycardia. Am J Cardiol 1987;59:78-83. 27. Selle JG, Svenson RH, Sealy WC, et al. Successful clinical laser ablation of ventricular tachycardia: a promising new therapeutic method. Ann Thorac Surg 1986;42:380-4. 28. Gallagher JJ, Selle JG, Svenson RH, et al. Surgical treatment of arrhythmias. Am J Cardiol 1988;61:27A-44A. 29-, MickJeborough LL, Wilson GJ, Harris L, Tashiro T, Parson I, Gray G. Balloon electric shock ablation: effects on ventricular structure, function, and electrophysiology. J THORAC CARDIOYASC SURG 1989;97: 135-46. 30. Guiraudon G M, Guiraudon CM, McLellan DG, MacDonald JL. Mitral valve function after cryoablation of the posterior papillary muscle in the dog. Ann Thorac Surg 1989;47:872-6. 31. Lawrie G M, Pacifico A, Kaushik R. Results of direct sur-
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gical ablation of ventricular tachycardia not due to chemic heart disease. Ann Surg 1989;209:713-27.
IS-
Discussion Dr. Gerard Guiraudon (London, Ontario. Canada). I concur with the authors in recommending cardiac mapping and surgical electrophysiologic intervention on the intact ventricle in patients without associated coronary artery disease or in patients with ischemic heart disease not associated with discrete fibrotic scar. In our laboratory, we have found that (I) endocardial cryoablation through the mitral valve orifice is feasible; (2) extensive cryoablation of the posterior papillary muscle is not associated with mitral valve regurgitation; and (3) extensive transmural cryoablation of the left ventricular apex is not associated with aneurysmal scar or left ventricular dysfunction. In our clinical practice, we have used endocardial cryoablation combined with epicardial cryoablation in six patients with ventricular arrhythmia not associated with coronary artery disease. Since the pioneering work of the Amsterdam school with deBakker, Janse, and their colleagues, as well as many other groups, endocardial mapping is feasible on the intact ventricle through either the mitral or the aortic valve orifice. As early as 1982, we were fortunate to map the intact heart, in patients, using the Amsterdam balloon. The potential advantages of this approach should be (1) intraoperative mapping of all clinical and nonclinical arrhythmias; (2) improved surgical efficacy; and (3) decreased surgical risk. A larger clinical experience is required to document these hypotheses, although current results encourage each of us to use such an approach whenever possible. Dr. Lawrie, which patients with coronary artery disease seem the ideal candidate? What is your policy for patients with intracavitary thrombus? Which patients would be considered for sequential endocardial cryoablation on the beating heart using a similar technique? Dr. Lawrie. Thank you for your kind remarks. Regarding patient selection, I believe that, with more experience with the anatomy and development of some other cryoprobes, cryoablation will be feasible in all patients in whom a ventriculotomy is not required for therapeutic reasons. The two main reasons at the moment that I see for making a ventriculotomy are (1) to take care of an aneurysm that is of significant size in terms of the patient's cardiac function and (2) to deal with multiple disparate foci, that is, several different areas around the ventricle. This condition occurs particularly in patients with ischemic heart disease. Endocardial resection is a quick and simple way of dealing with that, and I think it is still easier to do endocardial resection through the ventriculotomy. We have not tried transannular endocardial resection yet. In regard to the clot problem, we have taken the precaution of doing the left-sided mapping with the aorta crossclamped. We are thus not unduly concerned about dislodging clot with the balloon, and it is possible to inspect the interior of the apex of the left ventricle through the mitral valve. I think we have the flexibility there to make a decision intraoperatively either to continue the operation through the anulus or go to a ventriculotomy. Regarding sequential normothermic cryoablation, our earlier
10 36
Lawrie, Pacifico. Kaushik
experience with one or two patients who had a failure after normothermic cryoablation led us to routinely perform cryoablation only on the arrested cooled myocardium. We have not used the technique of sequential endocardial ablation. I think the work of Gallagher and Dr. Selle and his group on thermocoagulation is interesting. We are watching that work with great interest because if that technique proves to be as effective as cryoablation, then certainly that would be possible to perform on a warm beating heart. Dr. Jay G. Selle (Charlotte. NiC]. Our experience would agree with Dr. Lawrie's in that our operative mortality primarily involves the patients with diffuse severe ventricular impairment, that is, preoperative ejection fractions of less than 25% and no distinct left ventricular aneurysm. Survival in this group will possibly benefit by avoiding a ventriculotomy, although probably at the expense oflimiting endocardial exposure. In the occasional case requiring ablation of the right side of the septum, we will certainly use Dr. Lawrie's right-sided transannular approach. We have additionally noted a significantly higher morbidity and mortality resulting from pulmonary insufficiency in patients who have been on prolonged amiodarone therapy before the operation. Have you noted this problem of postoperative pulmonary insufficiency due to preoperative amiodarone therapy? Dr. Lawrie. Yes, we have. We have been looking at our amiodarone data in considerable detail. We found that there is a very serious risk of mortality in patients who have been on longterm, moderately high-dose amiodarone within 60 days of operation who have an ejection fraction below 35%. They are the group that seem to be at greatest risk. Of the patients who died, several of them died with low cardiac ouptut and severe adult respiratory distress syndrome. The data from Birmingham, Alabama, also support the view that amiodarone is a serious risk to these patients if they are receiving a significant dosage in the preoperative period. Dr. Selle. Ventricular mapping before the computer was inadequate. It was difficult if not impossible to mentally assimilate the data necessary to understand the wave fronts of reentry activity so eloquently and rapidly displayed by computer. However, I believe there is still an important role for the oldfashioned single hand-held probe technique of data acquisition and that both methods, the hand-held probe and the computer, are necessary in most cases. Spatial resolution of mapped sites can be much more precise with the hand-held probe than is possible with the computer array of multiple electrodes that are usually positioned I em or
The Journal of Thoracic and Cardiovascular Surgery
more apart. This precise spatial resolution is necessary, at least in our hands, to be able to truly localize the area of myocardium responsible for the initiation of each form of VT, for example, to determine whether that area of substrate is endocardial, intramural, or epicardial in depth. We have encountered epicardial VT in 10 of 43 patients, almost 25% of our cases. Furthermore, nine of these 10 patients had inferior infarcts without ventricular aneurysms. This is a subgroup in whom the rate of failure is high when conventional endocardial ablative procedures are used alone. I have two interrelated questions: Do you use the computer mapping system exclusively or do you agree that there is still a role for the hand-held probe method for precise data acquisition? Have you encountered examples of epicardial VT? Dr. Lawrie. Yes, we certainly have. This is why we gave up epicardial mapping with a hand-held probe, because the time required led to very long pump times and in our analyses we found that was a significant risk for mortality. With the computer it really adds nothing to the operation to do complete epicardial mapping in sinus rhythm and VT. We have actually had a number of patients with early epicardial breakthrough, and those data led us in a couple of our patients, both with inferior foci, to perform their entireVT operation as an epicardial operation. I think the concept that all VT arises from the endocardium is inaccurate and that we should continue to look at epicardial and endocardial mapping. I think it is extremely important to have both the hand-held probe and the computer available if for no other reason than that these computers are still basically homemade complex devices. So far we haven't had a problem, but one never knows when they are not going to work properly. I think the degree of accuracy is going to increase. It is correct that at the moment there is a I em electrode distance. However, our philosophy has been, even with the hand-held probes, to ablate all the area within the zero isochrone; even with precise mapping, we still have difficulty in working out whether the breakthrough, which is what we are recording on the endocardium, is in fact the site of origin or whether, as deBakker and others have shown, we are looking at a point where something has propogated over a distance of I to 3 em and then broken through the endocardium. Our next step is to double the electrode density of our endocardial balloon. We're hopeful that that will get us closer. Then finally we will use a plate with 50 or 60 points on it to try to get some information on these mechanisms. But I think it is very important to have facility with both techniques.