Subpectoral implantation of cardioverter-defibrillator combined with a nonepicardial lead system: Preliminary experience with a novel approach

amyloidosis in the study by Siqueira-Filho et al4 and in 7% of patients in the necropsy study of cardiac amyloidosis by Roberts and Waller.7 A number of studies have examined technetium-99m pyrophosphate myocardial scintigraphy in cardiac amyloidosis. Uptake of isotope into amyloid material allows its detection within the myocardium, although this method is not accurate when uptake is 10w.~ Although the sensitivity of this method was reported to be excellent by Wizenberg et al,2 other investigators have found it to be less sensitive than echocardi0graphy.l In all work published to date, however, assessment of technetium99m pyrophosphate uptake was semiquantitative, using the scale proposed by Parkey et al* and Falk et al’ based on visual assessment of myocardial uptake compared with costal and sternal uptake 3 hours after radionuclide injection. This method is subjective and there is no absolute threshold beyond which the diagnosis of cardiac amyloidosis may be made or refuted with adequate safety. For this reason, we have assessed a quantitative method for analyzing myocardial scintigraphy that produces reliable discrimination between patients with and without cardiac amyloidosis. We observed that in patients with cardiac amyloidosis, myocardial lixation of technetium-99m pyrophosphate occurs early, as early as a few minutes, and then masks blood intraventricular activity. The best contrast is obtained at 20 minutes when bone uptake of the isotope is still low and thoracic background noise is more uniform, resulting in a better subtraction. The cardiac activity can then be indexed on the liver mean activity which is uniform at 20 minutes, when the region of interest is drawn far from the ribs and renal activities. We assume that this represents nonspecific vascular activity. In the small number of patients reported here, scintigraphy uptake index discriminated completely between the 2 groups of patients. If this result is contirmed on a larger patient group it would indicate that technetium-99m pyrophosphate scintigraphy may be as reliable a noninvasive method for the diagnosis of cardiac amyloidosis as echo-Doppler techniques. However, these lindings can only be applied to the patient group studied, i.e., patients with amyloid polyneuropathy, and cannot be extrapolated to other

forms of cardiac amyloidosis. Although the scintigraphy uptake index may be useful in the diagnosis of cardiac amyloidosis, it does not correlate with echocardiography. It is diIIicult to produce formal quantification of the degree of amyloid inftltration without myocardial biopsy. Although a number of investigators1,3 have found a relation between echocardiographic thickness of the interventricular septum and intensity of myocardial uptake of technetium-99m pyrophosphate, our study failed to demonstrate adequate correlation between myocardial thickness measured by echocardiography, and the scintigraphy uptake index. This is not surprising since the 2 investigations probably assessdifferent phenomena: anatomic in one case, metabolic in the other. Finally, technetium-99m pyrophosphate myocardial scintigraphy could be valuable as a noninvasive technique to follow the progression of the disease in patients with cardiac amyloidosis. In conclusion, quantilication of technetium-99m pyrophosphate myocardial scintigraphy combined with early films (20 minutes) appears to be a reliable method of conlirming the echocardiographic diagnosis of cardiac amyloidosis in patients with amyloid polyneuropathy.

1. Falk RH, Lee VW, Rubinow A, Hood WB, Cohen AS. Sensitivity of Tecbnetium-99m-pyrophosphate scintigraphy in diagnosing cardiac amyloidosis. Am J Cardid 1983;51:826-830. 2. Wizenberg TA, Muz J, Solm YH, Samlowski W, Weissler AM. Value of positive myocaxdial technetium-99.pyrophosphate scintigraphy in the noninvasive diagnosis of cardiac amyloidosis. Am Heart I 1982; 103:468473. 3. Eriksson P, Backman C, Bjerle P, Eriksson A, Holm S, Olofsson BO. Non-invasive assessment of the presence and severity of cardiac amyloidosis. A study in familial amyloidosis with polynewopatby by cross sectional echocardiography and technetium-99m-pyrophosphate scintigraphy. Br Heart J 1984;52:321-326. 4. Siqueira-Filho AG, Cunha CL, Tajik AJ, Seward JB, Schattenberg ‘IT, Giuliani ER. M-mode and hvo dimensional echocardiograph? features in cardiac amyloidais. Circulation 1981;63:188-196. 5. Falk RH, PI&n JF. De&w T, Schick EC, Boinav P. Rubinow A. Skinner M. Cohen AS. Sensitivity and specificity of the echccardiogmphic features of card& amyloidosis. Am .I Cardiol 1987;59:4181122. 6. Goris ML, Daspit SG, MC Laughlin P, Kriss I. Interpolative background subtraction. .I Nucl Med 1976;11:7&747. 7. Roberts WC. Waller BF. Cardiac amvloidosis causing cardiac d&unction: analysis of 54 necropsy patients. Am J Car&l 1983;52:13?-146. ’ 6. Parkey RW, Bonte FJ, Meyer SL, Atkins JM, Cuny GL, Stokley EM, Willerson JT. A new method for radionuclide imaging of acute myocxdial infarction in humans. Circulation 1974;50:540-546.

Subpectoral Implantation of CardioverterDefibrillator Combined with a Nonepicardial Lead System: Preliminary Experience with a Novel Approach John H. Ip, MD, Davendra Mehta, MD, PhD, Elena Pe, RN, Jorge L. Camuiias, MD, and J. Anthony Gomes, MD he use of an implantable cardioverter-defibrillator T (ICD) has been accepted as standard therapy in patients resuscitated from sudden cardiac arrest and with symptomatic recurrent ventricular arrhythmias refractoFrom the Section of sion of Cardiology, diothoracic Surgery, New York 10029. manuscript received

Electrophysiology and Electrocardiography, DiviDepxtment of Medicine and Department of CarBox 10.54, Mount Sinai Medical Center, New York, Manuscript received January 27, 1993; revised and accepted May 21, 1993.

ry to conventional an&rhythmic agents.1,2 Many surgical approaches to implantation of the ICD sensing and defibrillation leads have been used including median stemotomy anterolateral thoracotomy and subcostal and subxiphoid approach.3 Although the incidence of major complications with these techniques is not high, potential complications such as pneumothorax, pleural effusion, pericardial effusion and cardiac temponade have been described. Additionally, a postoperative hospital stay of 5 to 8 days is usually required. Implantation of BRIEF REPORTS 857

TABLE I Clinical Features of Patients, Parameters Defibrillator and Length of Hospital Stay Underlying Patient Number

Heart Disease

1 2 3 4 5 6 7 8 9 10 11

CAD CAD CAD CAD CAD CAD CAD CAD CAD CAD CAD IDC IDC IDC IDC

12 13 14 15

at implantation

of Cardioverter-

1

EF

(%I

Nonfatal Cardiac Arrest

VT

25 25 15 35 28 25 25 15 17 20 25 40 17 25 35

+ 0 0 + 0 0 + 0 0 0 + 0 0 0 0

0 + + 0 + + 0 + + + 0 + + + +

R-Wave Amplitude (mV) 15 7 15 15

10 10 15 25 15 15 10 15 15

10 10

Test Shocks (no.)

DFT (J)

<8 <15 < 10 >20 >20 <12 <20 <12 <8 <15 <15 <8 <12
< 10

3 4 8

11 10 6 9 6 6 5 5 3 6 4 6

Hospital Stay (days) 4 7 4 4 4 3 4 3 3 3 4 3 3 4 3

CAD = coronary attery disease; DFT = defibrillation threshold: EF = left ventricular ejection fraction; IDC = idiopathic dilated cardiomyopathy; VT = ventricular tachycardia. I

the ICD without the use of thoracotomy would decrease the potential mortality, the length of hospital stay, and the overall cost of the therapy.4 Implantation of the ICD using various endocardial lead and subcutaneous and submuscular patch systems without thoracotomy have been reported by several investigators.5,6 The current major limitation regarding these non-thoracotomy systems is a relatively high defibrillation threshold. Currently, approximately 2.5 to 35% of patients have no success with these systems and require epicardial or thoracotomy approaches. In this report, we describe the result of a non-thoracotomy system using a Food and Drug Administration (FDA)-approved transvenous spring coil electrode in 15 patients. The study protocol was approved by the Institutional Review Board and informed consent for the study was obtained in all patients. F$een consecutive patients (mean age 59 f 12 years) who were candidates for ICD implantation were included in the study (Table

FlGUGE ing the

858

1. Chest position

rediogreph (posteroan&erior of the lead, petch (arrow)

[/eft] and lateral and the device.

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I). Eleven patients had symptomatic sustained ventricular tachycardia, 4 had aborted sudden cardiac death. Eleven patients had coronary artery disease and 4 had idiopathic dilated cardiomyopathy. The mean left ventricular ejection fraction was 25 + 7%. All patients underwent electrophysiologic study before ICD implantation using standard protocol. Thirteen patients had inducible sustained ventricular tachycardia (deBned as sustained when lasting >30 seconds, or associated with hemodynamic compromise). All patients were deemed suitable candidates for ICD on the basis of history, clinical presentations and electrophysiologic findings. The lead system consisted of FDA-approved transvenous leads and defibrillator patch. An 8Fr bipolartined passive fixation endocardial electrode (Cardiac

of a patient

OCTOBER 1,1993

with

cardioverterdefibrillator

demonstret-

Pacemakers Inc., Minneapolis, Minnesota [CPI], B-10) was positioned at the right ventricular apex for rate sensing. An IlFr spring coil electrode (CPI, C-10) was positioned at the superior vena cava and the right atrium (Figure 1). Both leads were inserted by the cutdown through the branches of the left axillary vein identtjied in the delto-pectoral grove or directly into the left axillary vein. A large patch (CPI, Minneapolis, L6l7) was placed submuscularly at the anterolateral chest wall near the cardiac apex through a submammary incision (Figure I). Acceptable rate-sensing amplitude was 25 mV All patients underwent X3 separate dejibrillation attempts at 120 J. Repositioning of the submuscular patch or “patch mapping” andlor the superior vena cava lead was attempted in patients with initial unsuccessful defibrillation attempts before deciding to abandon the approach. If a satisfactory threshold was not obtainable after repositioning, the chest was entered through an intercostal incision at the level of the fifrh or sixth intercostal space using the same skin incision. The large patch was placed epipericardially and sutured to the epicardium. The pericardium was not opened. The ICD (CPI Ventak P, model 1600) was placed in a submuscular pectoral (Figure 1) pocket. The submammar-y incision that was made for positioning of the large patch served as the ICD pocket. The rate-sensing lead and superior vena cava lead were tunneled to the pocket. These leads were Jirmly anchored to the pectoralis major with nonabsorbable sutures. Details of the surgical technique are in publication elsewhere.’ The endocardial lead sensing was 7 to 15 mV (mean 13 + 3). The pacing thresholds were 0.2 to 1.5 mV (mean 1 .O rt 0.5) at 0.5 ms pulse duration. Thirteen patients (85%) had a satisfactory defibrillation threshold of ~20 J (mean 11.9 rt 2.8 J). Three patients had thresholds of ~8 J and 12 patients has threshold of ~15 J. Patients 4 and 5 had a defibrillation threshold >20 J and thus they underwent limited lateral thoracotomy and insertion of the epicardial patch with retainment of the spring electrode in the right atrium. The subsequent dej?brillation thresholds using this epicardial system were determined to be <20 J. The average number of test shocks required per patient was 6.2 (Table I). All patients tolerated the implantation procedure without dificulty. No perioperative complications occurred. All patients except 1 were discharged in <5 days (mean hospital stay 3.6 + 1.1). Patient 2 had a relatively prolonged course for management of congestive heart failure. Postoperative follow-up at 4 weeks was done in all patients. Subsequent follow-up visits were done every 2 months with interrogation of the device and assessment of the capacitor charge time. Patients were spectjically questioned about any problems related to the pocket or its location, symptoms of palpitations, syncope or ICD discharges. These were investigated further when appropriate. Six patients experienced ICD discharges. Four patients had documented ventricular tachycardia and subsequent ICD shocks. Two patients experienced presyncopal episodes accompanied by device discharges presumed to be secondary to recurrent ventricular tachycardia. All patients were followed closely for I to 6 months (mean duration 3.4)

and no complications related to the procedure have been reported. The use of the ICD has dramatically improved the survival rate of patients with malignant sustained ventricular arrhythmias and patients who survived episodes of sudden cardiac death.1,2 A major limitation of the most frequently used system is the need for thoracotomy. The use of a nonepicardial lead system will substantially improve general acceptance, limit potential complications, and reduce overall cost. Several transvenous non-thoracotomy systems have been used with some success. McGowan et al* compared the use of various Endotak spring-patch conligurations in 10 patients. The epicardial system consisted of a 12Fr tripolar endocat-dial catheter for rate and morphology sensing as well as shock delivery. The tripolar catheter consisted of a proximal and a distal spring electrode. These spring electrodes and the subcutaneous patch could serve in many different combinations as cathode and anode. In their study, the lowest defibrillation threshold was achieved with the use of the distal spring electrode as cathode and the proximal spring and the patch as anode. Still, approximately 25 to 35% of the patients using these nonepicardial systems had unacceptable high-defibrillation threshold and required epicardial alternatives. A totally transvenous system without the use of subcutaneous patches has also been tried.6,7 The system involved electrodes positioned in the coronary sinus, superior vena cava and right ventricular apex. Although this system appeared to be attractive, only 60 to 65% of patients achieved the defibrillation threshold requirement. The components of the lead system used in this study are all approved by the FDA. The patch was positioned submuscularly and served as one of the electrode terminals, and a single superior vena cava transvenous spring electrode served as the other. The right ventricular lead was for rate-sensing purpose only. The system has excellent defibrillation threshold. Three patients required 43 J for defibrillation and all patients except patient 7 had thresholds of 45 J. This allows the use of lower energy first shock of the ICD and may potentially decrease patient discomfort at the time of unit discharge and prolong battery life. There are 2 possible explanations for the excellent energy threshold. First, patch mapping was performed in all patients to locate the optimal patch location with the lowest defibrillation threshold. The position of the “ideal” submuscular patch location varies in different patients and may reflect the containment of the largest amount of myocardial tissue between the patch and the spring electrode. Second, submuscular placement of the patch eliminated a substantial amount of tissue between the myocardium and the patch, and thereby may have decreased the total energy impedance. The efficacy of biphasic shock waveforms with non-thoracotomy systems is currently being investigated. It is likely that the use of biphasic shocks with our system will provide a higher success rate and lower defibrillation thresholds. Implantation of the ICD generator in the subpectoral region has been described recently in a case report9 In all our patients, placement of the generator in this locaBRIEF REPORTS 859

tion was well tolerated during follow-up evaluation. No limitation of the shoulder or upper arm movement was reported and no pulse generator migration occurred. In addition, the incisional wounds were generally smaller than those for implantation in the abdominal region and may theoretically decrease the incidence of infection. Future generations of ICD design incorporate the generator as one of the electrode terminals to serve as a cathode or an anode, and this will necessitate the placement of the generator in the thoracic region. In addition, the size of future generators is expected to be smaller and thus, as in the case of permanent pacemakers, pectoral implantation of ICD is likely to increase. Fewer perioperative complications were generally reported in the non-thoracotomy lead systems compared with epicardial systems.4 We found no signilicant perioperative complications. All patients who received the nonepicardial system were ambulatory by the first postoperative day and all were discharged by day 5, except patient 2 whose hospitalization was prolonged because of preexisting congestive heart failure. All patients were followed in our institution and developed no complication. Nonepicardial implantation of the ICD using a FDA-approved patch positioned submuscularly and a FDA-approved spring coil electrode appears to be feasible. Excellent defibrillation thresholds were achieved in

860

THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 72

13 of 15 patients (87%) in this study. Relatively easy transition to an epicardial system can be done with a small lateral thoracotorq if necessary. Positioning of the generator subpectorally can improve appearance and comfort. However, long-term efficacy of the current approach needs to be evaluated.

1. Akhtar M, Avitall B, Jazayeri M, Tchou P, Troup P, Sra J, Axtell K. Role of implantable cardioverter-defibtilator therapy in the management of high-risk patient. Circulation 1992;85(suppl 1):1-l 131-1-l 140. 2. Saksena S, Camm J. Implantable defibrillators for prevention of sudden death: technology at a medical and economic crossroad. Circulation 1992;85:231&2322. 3. Frank G, Lowers D. Implantable cardiowter defibrillators: surgical con!;i.derations. PACE 1992;15:631-636. 4. Saksena S. Endow&J lead systems for implantable cardioverter-defibrillators: uncextain progress beyond base camp. PACE 1992;15:123-1215. 5. Block M, Hammel D, Isbmch F, Borggrefe M, Wietholt D, Hachenberg TD, Scheld HH, Breithardt G. Results and realistic expectations with transvenous lead system. PACE 1992;15:665-671. 6. Hauser R, Mower R, Mitchell M, Nisam S. Current status of the Vent& PRX pulse generator and Endotak non-thoracotomy lead system. PACE 1992;671678. 7. Camufunas .I, Mehta D, Ip J, Pe E, Games JA. Total pectoral implantation: technique for implantation of implantable ca~dioverter defibrillator with tnnsvenous leads. PACE 1993; in press. 6. McGowan R, Maloney J, Wilkoff B, Simmons T, Khoury D, McAlister H, Morant V, Caste1 L. Automatic implantable caxlioverterdefibrillator implantation without thoracotomy using an endocaxlial and submuscular patch system. J Am Co11 Cardiol 1991;17:415421. 9. Hammel D, Block M, Borggrefe M, Konertz W, Breithardt G, Scheld HH. Implantation of a cardioverter-defibrillator in the subpectoral region combined with a non-thoracotomy lead system. PACE 1992;15:367-368.

OCTOBER 1, 1993