- Email: [email protected]
Efficacy and safety of monophasic and biphasic waveform shocks using a braided endocardial defibrillation lead system
Sager et al
American
27. Mirowski M. The automatic implantable cardioverterdefibrillator: an overview. J Am Co11 Cardiol 1985;6: 461-6. 28. Kelly PA, Cannom DS, Garan H, Mirabal GS, Harthorne JW, Hurvitz RJ, Vlahakes GJ, Jacobs ML, Ilvento JP, Buckley MJ, Ruskin JN. The automatic implantable cardioverter-defibrillator: efficacy, complications and survival in patients with
December 1990 Heart Journal
malignant ventricular arrhythmias. J Am Co11 Cardiol 1988; 11:1278-86. 29. Echt DS, Armstrong K, Schmidt P, Oyer P, Stinson E, Winkle RA. Clinical experience, complications, and survival in 70 patients with the automatic implantable cardioverter/defibrillator. Circulation 1985;71:289-96.
Efficacy and safety of monophasic and biphasic waveform shocks using a braided endocardial defibrillation lead system Endocardial lead systems for implantable cardioverter-defibrillators utilize large (12F) rigid catheters with spring defibrillation electrodes, and lead system failure has been observed during long-term implant. We evaluated a novel flexible 8F braided electrode catheter for pacing and defibrillation in canine experiments. Active fixation and pacing were accomplished using a screw-in distal electrode, and defibrillation pulses were delivered through a braided electrode. Two braided electrode catheters were positioned in the right ventricular apex (6 cm*) and in the superior vena cava-right atrial junction (5 cm*), respectively. An elliptical 13 cm* surface area patch electrode was positioned along the left lateral cardiac border. Ventricular fibrillation (VF) was induced and monophasic and asymmetric biphasic shocks (leading voltages 260 to 1000 V) were delivered via dual and triple electrode conflgurations in each animal using a prospective randomized crossover study design. Mean right ventricular pacing threshold was 0.5 & 0.2 mA, with a mean electrogram amplitude of 11.1 + 2.8 mV during sinus rhythm prior to fibrillation and defibrillation. Two hundred seven VF inductions (mean 30 + 4 per animal) were analyzed. The mean defibrillatton threshold could be reduced to 8.0 + 3.2 joules with biphasic shocks from 12.9 ? 5.1 joules obtained for monophasic shocks using a dual electrode system (jr < 0.004). Mean shock leading voltage was correspondingly reduced to 488 + 100 V from 691 + 154 V (p < 0.0006). The mean defibrillation threshold could be reduced to 10.7 + 3.4 joules with biphasic shocks from 14.8 f 4.9 joules for monophasic shocks using a triple electrode system (right ventriclej-]/patch and right atrium[+]; p < 0.02). Mean shock leading voltage was correspondingly reduced to 543 f 101 V from 717 + 114 V (p < 0.003). Pacing thresholds were unchanged after defibrillation (p > 0.05). We conclude that successful pacing and defibrillation is feasible with a small-caliber braided electrode catheter. Percutaneous insertion of one or two catheters permits use with dual and triple electrode configurations. Asymmetric biphasic waveform pulses reduce endocardial defibrillation threshold with this catheter electrode system. (AM HEART J 1990;120:1342.)
Sanjeev Saksena, MD, Steven E. Scott, BS, Peter R. Accorti, MS, Birinder K. Boveja, BS, Debra Abels, BS, and Frank J. Callaghan, Newark and Passaic, N.J., and Miami, Fla.
From the Division of Cardiology, UMDNJ-New Newark; The Eastern Heart Institute, Passaic; Systems, Inc., Miami.
Jersey Medical and Telectronics
Received
July
for publication
Feb.
12, 1990;
Reprint requests: Sanjeev Saksena, Boulevard, Passaic, NJ 07055. 4/l/24132
1342
MD,
accepted
The Eastern
School, Pacing
1. 1990. Heart
Institute.
350
MSEE.
Implantable cardioverter-defibrillators are being increasingly employed for the treatment of patients with life-threatening ventricular tachyarrhythmias. Endocardial lead systems have been proposed for use in conjunction with such devices.’ Unfortunately, the efficacy of prototype lead systems was limited for
Volume Number
120 6, Part
1
termination of both ventricular tachycardia (VT) and ventricular fibrillation (VF).2* 3 Recently, we have developed a triple electrode configuration permitting bidirectional shocks for clinical application4 and have demonstrated its clinical efficacy in converting both VT and VF.5-7 One clinical investigation was performed using a large (12F) tripolar electrode catheter with two defibrillation electrodes and one tip-sensing electrode used in conjunction with a submuscular patch electrode.3 Catheter electrode performance was characterized by poor maneuverability as well as by late conductor fracture, resulting in inappropriate shock delivery and even documented sudden death in selected patients.7 In an effort to improve the performance of endocardial defibrillation lead systems, we have developed a new braided endocardial defibrillation lead system (Telectronics Pacing Systems, Inc., Miami, Fla.). Furthermore, we have evaluated the efficacy of bidirectional and unidirectional shocks using monophasic and biphasic shock energy waveforms in an effort to reduce defibrillation energy requirements for the endocardial technique. In this report we summarize our initial evaluation of the efficacy and safety of this electrode system. METHODS Seven conditioned adult male mongrel dogs with weights ranging from 35 to 50 pounds were used. The dogs were anaesthetized using intravenous pentobarbitol sodium and were placed on a Harvard respirator (Harvard Apparatus Inc., S. Natick, Mass.) after intubation. Surface electrocardiogram electrodes were attached to the limbs and electrocardiographic monitoring was performed on a physiologic recorder. Hard copy recordings of the electrocardiograms were obtained on an eight-channel chart recorder. Arterial blood pressure recordings were obtained and cutaneous electrodes were used for external rescue defibrillation. Electrode system and technique. The braided endocardial defibrillation lead system employs two bipolar 8F electrode catheters. There is an electrically isolated active fixation screw-in helix with a porous annular pacing electrode. A defibrillation electrode of 5 or 6 cm length with electrode surface areas of 5 or 6 cm2 is placed proximal to the tip electrode. Using fluoroscopic guidance, a 6 cm2 braided endocardial defibrillation lead was introduced through the jugular vein and was positioned in the right ventricular apex. A 5 cm2 braided endocardial defibrillation lead was positioned in the superior vena cava. These leads were used in conjunction with a patch electrode (surface area of 13 cm2) positioned in a subcutaneous location on the left lateral thorax along the left cardiac border. Energy delivery modes. Two defibrillation shock energy waveforms were studied. The monophasic waveform utilized a truncated exponential voltage pulse of 5 msec du-
Braided
endocardiul
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lead system
1343
ration delivered from a 60 rF capacitor in an external defibrillation unit. The asymmetric biphasic waveform consisted of a positive truncated exponential voltage pulse of 5 msec duration followed by a 1 msec delay and a subsequent negative truncated voltage pulse of 5 msec duration whose initial leading voltage magnitude was 50% of the positive pulse. Each pulse was delivered from a 60 PF capacitor and from the external defibrillation unit. Two defibrillation lead configurations were evaluated. In the bidirectional configuration, the negative (cathodal) electrode is the endocardial defibrillation lead located in the right ventricular apex and two positive (anodal) electrodes are used, consisting of the endocardial defibrillation lead in the superior vena cava cross-connected with the subcutaneous patch electrode. In the unidirectional configuration, the endocardial defibrillation lead in the right ventricular apex is still used as the cathodal electrode and a single anodal electrode consisting of the subcutaneous patch electrode is used. Thus in the bidirectional configuration dual current pathways are established, whereas in the unidirectional configuration a single current pathway is established. These pathways have been previously described.4p 6 Endocardial defibrillation threshold testing. Defibrillation thresholds were obtained for the following experimental configurations: (1) monophasic waveform-unidirectional lead configuration; (2) monophasic waveformbidirectional lead configuration; (3) asymmetric biphasic waveform-unidirectional lead configuration; (4) asymmetric biphasic waveform-bidirectional lead configuration. The animals were induced into VF using a 60 Hz signal. Initial defibrillation was attempted using an arbitrary starting voltage of 600 V based on prior studies. If the initial shock was a success/failure, the shock voltage used in subsequent arrhythmia inductions would be decreasedlincreased by 20% until failure/success was obtained. The lowest successful shock voltage achieving successful defibrillation was determined. Two or more additional arrhythmia inductions were then performed in order to achieve three consecutive successful VF terminations; this voltage was then considered the defibrillation threshold. Pacing and sensing evaluation. Unipolar pacing thresholds from the right ventricular endocardial defibrillation lead as well as R wave amplitude were analyzed in six animals. Pacing thresholds were obtained using 1 msec constant pulse, and unipolar R wave amplitude was averaged over 10 beats. Arterial blood pressure was monitored continuously during the experiment and during each VF induction and defibrillation. Study design and analysis. For adequate comparison of all four electrode configurations and shock energy modes, the sequence of application of each configuration was randomized using a prospective controlled crossover study design. This permitted equivalent testing of each electrode configuration in the total group of experiments. At the end of each experiment, the animal was sacrificed and the heart was removed for pathologic examination. The right atrium and right ventricle were exposed with the leads in place so
1344
Saksena et al.
American
December 1990 Heart Journal
0 0
I 0
3
!
Cl-CONTROL
MIB
M/u
ABiB
AS/U
1. Endocardial ventricular electrogram amplitude (R wave) in the baselinestate and after endocardial defibrillation shockswith different configurations. There is a significant reduction in R wave amplitude with monophasicbidirectional shocksthat is small but statistically significant. The other configurations did not showa significant change.In all instancesthe R wave amplitude wasmore than adequatefor routine sensing.Values are representedas mean + 1 standard deviation. M, Monophasic; B, bidirectional; AB, asymmetric biphasic; U, unidirectional. Fig.
that lead placement or any noticeable endocardialand epirhythm was 11.1 cardial damage could be clearly observed. Defibrillation rectional shocks, threshold was obtained using the three consecutivesuccess ished to a mean methodsasdefinedabove.Statistical analysiswasperformed After monophasic usinga two-tailed paired-differenceStudent’s t test. RESULTS
Fluoroscopic guidance permitted successful positioning of the leads in all the animals evaluated. The patch electrode was placed subcutaneously in all animals. Unipolar endocardial ventricular pacing was accomplished using the braided endocardial defibrillation lead applying constant current pulses of 1 msec duration. The mean right ventricular endocardial pacing threshold before defibrillation threshold testing was 0.5 & 0.2 mA. After defibrillation threshold testing with monophasic bidirectional shocks, mean right ventricular pacing threshold was 0.6 +- 0.1 mA (p > 0.05), and after monophasic unidirectional shocks it was 0.6 * 0.1 mA (p > 0.05). After asymmetric biphasic shocks delivered with the bidirectional configuration, the mean bipolar pacing threshold was 0.6 f 0.1 mA (p > 0.05). After asymmetric biphasic shocks using the unidirectional current pathway, the pacing threshold was 0.7 +- 0.2 mA (p > 0.05). Electrogram amplitudes are shown in Fig. 1. The mean right ventricular unipolar electrogram amplitude (R wave) in the control state during sinus
* 2.8 mV. After monophasic bidithe amplitude of the R wave diminvalue of 6.8 + 2.8 mV (p < 0.05). unidirectional shocks, the mean R wave amplitude was 9.1 -t 3.7 mV (p > 0.05). After asymmetric biphasic shocks using a bidirectional configuration, the mean R wave amplitude was 7.7 f 3.6 mV (p > 0.05). After asymmetric biphasic shocks using a unidirectional configuration, the mean R wave amplitude was 10.8 f 3.4 mV (p > 0.05). Defibrillation thresholds obtained using the four different shock and electrode configurations are shown in Fig. 2. The mean defibrillation threshold in the study group using monophasic shocks and a unidirectional configuration was 12.94 t- 5.08 joules, with a mean shock leading voltage of 691 ? 154 V. With asymmetric biphasic shocks using a unidirectional electrode configuration, the mean defibrillation energy threshold declined to 8.02 of: 3.20 joules (p = 0.0026 compared with monophasic values), with a mean shock leading votage of 488 * 100 V. The mean defibrillation threshold using monophasic shocks and a bidirectional electrode configuration was 14.77 f 4.94joules,withameanshockleadingvoltage of 717 & 114 V. Endocardial defibrillation threshold declined to 10.70 * 3.35 joules using asymmetric biphasic energy waveforms in the same bidirectional
Volume Number
120 6, Part
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1
20
endocardial
defibrillation
lead systen
1345
-
si 2 4, 15tP 10 -
5-
M/B
AB/B
wu
ABIU
2. Defibrillation threshold energiesasobtained by the three consecutivesuccessmethods(in Joules). Individual data points are shownand actual delivered energy was measured.DFT, Defibrillation threshold; other abbreviations as in legend to Fig. 1.
Fig.
configuration 0, = 0.0196 compared with monophasic pulses), with a mean shock leading voltage of 542 & 101 V. There was no significant difference in mean defibrillationthreshold using a bidirectional or unidirectional shock configuration with monophasic energy waveforms. In this study, there was also a significant reduction in defibrillation threshold using an asymmetric biphasic waveform with a unidirectional pathway compared with the monophasic waveform with a bidirectional pathway (p = 0.0005). There was also a significant reduction in mean defibrillation threshold using asymmetric biphasic shock waveforms with the bidirectional electrode configuration compared with a monophasic energy waveform with a unidirectional pathway (p = 0.039). Pathologic findings. Gross pathologic findings were largely localized to the site of the catheter electrode. The junction of the superior vena cava and right atrium did not show any significant abnormalities. There was focal hemorrhage and necrosis at the site of lead insertion in the right ventricle. The epicardial surface was usually normal but extension to this area was observed in one animal. There was focal hemorrhage noted in the right atrioventricular valve leaflet adjacent to the lead entrance into the right ventricle in one animal. DISCUSSION
Transvenous defibrillation lead systems have been studied since the early developmental period of implantable defibrillation devices.l, * Initial evaluation
of a transvenous dual electrode catheter demonstrated unreliable VF termination and high defibrillation thresho1ds.l Subsequently, low-energy cardioversion of sustained VT with endocardial shocks was noted in selected patients8 Evaluation in a prospective controlled clinical trial elicited limited efficacy.2 Efficacy of low-energy endocardial cardioversion was determined by tachycardia rate and absolute shock energy. Rapid VT and VF could not be terminated reliably, even at high shock energies. Electrophysiologic effects of these shocks included slowing and interruption of conduction in the slowly conducting limb of the tachycardia circuit as well as modification of the refractoriness in these tissues9 In an effort to obtain wider electrophysiologic effects, we reported use of a triple electrode system employing a Medtronic 6880 tripolar catheter (Medtronic Inc., Minneapolis, Minn.) and thoracic patch electrodes permitting dual current pathways in man47 lo Reduction in cardioversion thresholds and successful endocardial defibrillation have been possible with this approach.4y 5 This electrode system employs a single right ventricular cathode and dual anodes in the superior vena cava and the left lateral thoracic region. In a recent clinical report with a subsequent catheter electrode,7 9 of 10 patients had successful endocardial defibrillation with a mean defibrillation energy threshold of 18 +- 5 joules. Previous clinical studies employed truncated exponential monophasic shock energy waveforms for endocardial cardioversion and defibrillation.7 Exper-
1346
Saksena et al.
imental evidence suggests that asymmetric biphasic shock energy waveforms reduce defibrillation energy thresholds for transthoracic and epicardial electrode systems.“, l2 Studies on the cellular electrophysiologic basis for this observation have suggested that the period of cell membrane dysfunction and electrical arrest induced by high-energy shocks is abbreviated by biphasic waveforms.13 This shock waveform may restore membrane function and integrity. One recent clinical studyI has, however, suggested that reduction in defibrillation energy requirements by biphasic shocks is most frequently observed in patients with low monophasic shock energy requirements for epicardial defibrillation, This would limit the usefulness of this approach to a selected subgroup of patients when it was applied using epicardial lead systems. This study evaluated the value of biphasic shocks when applied through endocardial lead systems. Application of biphasic shocks through this new endocardial lead system was evaluated for two different lead configurations. The braided endocardial lead system permits dual-chamber sensing, pacing, and variable current pathways for defibrillation shocks. This pacing and defibrillation endocardial lead is significantly smaller in diameter, with greater flexibility and maneuverability for endocardial placement. It is similar in many respects to current dualchamber endocardial pacing lead systems. Endocardial lead placement is accomplished using conventional dual-chamber pacemaker implantation techniques. l5 In conjunction with a subcutaneous left thoracic patch electrode, this triple electrode system permits use of a variety of single or dual current pathways. 4, 5 It also permits bipolar endocardial pacing and sensing, thus avoiding the chronic pacing threshold and sensing electrogram changes observed with epicardial systems. l6 Endocardial shock delivery did not significantly alter pacing thresholds, as has been observed in other lead systems.17t I8 Sensing R wave amplitude did show a trend to a small decrease after endocardial defibrillation. In this study, asymmetric biphasic shocks reduced endocardial defibrillation energy requirements when compared with monophasic shocks for one single and one dual current pathway. The mean reduction in endocardial defibrillation threshold was 38% for unidirectional shocks and 28 % for bidirectional shocks (p < 0.05). The study suggests that in canine experiments endocardial defibrillation thresholds can be reduced for the two energy pathways studied using this lead system. Clearly, this cannot be extrapolated to other current pathways, energy delivery patterns employing multiple or sequential shocks,
American
December 1990 Heart Journal
or other electrode systems. A single current pathway was more advantageous in this study despite a smaller electrode surface area (19 cm2 versus 24 cm2), suggesting that surface area may be only one of several important variables. Due to significant differences between canine and human thoracic anatomy, clinical evaluation of this lead system with biphasic and monophasic shocks will be necessary to establish the value of biphasic endocardial shocks. Should similar observations be obtained, this will permit wider application of endocardial leads and a significant reduction in pulse generator size. This may avoid the current need for abdominal implantation sites. Conventional insertion techniques used for permanent pacing lead systems can be employed. We expect that the braided endocardial defibrillation lead system will help establish the principle of generic pacing and defibrillation lead for clinical application. The authors Ellen Wendler
acknowledge the valuable assistance in the preparation of the manuscript.
of Mrs.
Ina
REFERENCES
1. Mirowski M, Mower MM, Gott VL. Brawley RK. Feasibility and effectiveness of low energy catheter defibrillation in man. Circulation 1973;47:79-85. 2. Ciccone JM, Saksena S, Shah Y, Pantopoulos D. A prospective, randomized study of the clinical efficacy and safety of transvenous cardioversion for ventricular tachycardia termination. Circulation 1985;71:571-8. 3. Saksena S, An H. Clinical efficacy of dual electrode systems for endocardial cardioversion of ventricular tachycardia: a prospective randomized crossover trial. AM HEART J 1990;119:1522. 4 Saksena S, Calvo RA, Pantopoulos D, Gadhoke A, Rothbart ST. A prospective evaluation of single and dual current pathways for transvenous cardioversion in rapid ventricular tachycardia. PACE 1987;10:1130-41. 5. Saksena S, Parsonnet V. Implantation of a cardioverterl defibrillator without thoracotomy using a triple electrode system. JAMA 1988;259:69-72. 6. Lindsay BD, Saksena S, Rothbart ST, Wasty N, Pantopoulos D. Prospective evaluation of a sequential pacing and high-energy bidirectional shock algorithm for transvenous cardioversion in patients with ventricular tachvcardia. Circulation 1987;76:601-9. 7. Saksena S, Tullo NG, Krol RB, Mauro AM. Initial clinical experience with endocardial defibrillation usina an imnlantable cardioverter/defibrillator with a triple electrode systkm. Arch Intern Med 1989;149:2333-9. 8. Zipes DP, Jackman WM, Heger JJ, Chilson DA, Browne KF, Naccarelli GV, Rahilly GT, Prystowsky EN. Clinical transvenous cardioversion of recurrent life-threatening tachyarrhythmias: low energy synchronized cardioversion of ventricular tachycardia and termination of ventricular fibrillation in patients using a catheter electrode. AM HEART J 1982; 103:789-
94. 9. Saksena S, Pantopoulos D, Hussain SM, Gielchinsky I. Mechanisms of ventricular tachycardia termination and acceleration during transvenous cardioversion as determined by cardiac mapping in man. AM HEART J 1987;113:1495-506. 10. Saksena S, Calvo RA, Pantopoulos D, Gordon S, Gadhoke A. Simultaneous shocks for ventricular tachycardia cardiover-
Volume Number
11.
12.
13.
14.
15.
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1
sion: effect of electrode position on efficacy [Abstract]. Clin Res 1986:34:341A. Schuder JC, Gold JH, Stoeckle M, McDaniel WC, Cheung KN. Transthoracic ventricular defibrillation in the 100 ka calf with symmetrical one-cycle bidirectional rectangular wave stimuli. IEEE Trans Biomed Eng 1983;30:415-22. Tane AS. Yabe S. Wharton JM. Dolker M. Smith WM. Ideker RE. Ventricular defibrillation using biphasic wavefor’&- the importance of phasic duration. J Am Co11Cardiol1989,13:20714. Jones JL, Jones RE. Decreased defibrillator-induced dysfunction with biphasic rectangular waveforms. Am J Physiol 1984;247:H792-6. Winkle RA, Mead RH, Ruder MA, Gandiani V, Buch WS, Pless B. Sweenev M. Schmidt P. Imuroved low enerev defibrillation efficacy in man with the use of biphasic tru;cated exponential waveform. AM HEART J 1989;117:122-7. Holmes DR, Holmes DR Jr. Pacemaker implantation tech-
niques. In: Saksena S, Goldschlager N, eds. Electrical therapy for cardiac arrhythmias. Philadelphia: WB Saunders Co, 1990:173-90. 16. Timmis GC. The electrobiology and engineering of pacemaker leads. In: Saksena S, Goldschlager N, eds. Electrical therapy for cardiac arrhythmias. Philidelphia: WB Saunders Co, 1990:35-90. 17. Van Vleet JF, Tacker WA Jr, Bourland JD, Kallok MJ, Schollmeyer MP. Cardiac damage in dogs with chronically implanted automatic defibrillator electrode catheters and given four episodes of multiple shocks. AM HEART J 1983; 106:300-7. 18.
Waspe LE, Kim SG, Matos JA, Fisher JD. Role of a catheter lead system for transvenous countershock and pacing during electrophysiologic tests: an assessment of the usefulness of catheter shocks for terminating ventricular tachyarrhythmias. Am J Cardiol 1983;52:477-84.
The role of ,&blockade therapy for ventricular tachycardia induced with isoproterenol: A prospective analysis lsoproterenol is sometimes required for ventricular tachycardia (VT) induction. However, the role of Pblockade for treatment of such VT has not been critically assessed. The use of B-blockade was evaluated prospectively in 14 consecutive patients who required isoproterenol 2.4 + 1.3 (? S. D.) pg/min to induce sustained monomorphic VT (>30 seconds, or requiring termination due to hemodynamic collapse) after a negative baseline study. The VT mechanisms were enhanced automaticity (group A, six patients), triggered automaticity (group B, three patients), and reentry (group C, five patients). Groups A and B had serial intravenous electropharmacologic tests with propranolol alone (0.2 mg/kg), verapamil alone (0.15 mg/kg), and propranolol plus verapamil, and group C had serial tests with propranolol alone, procainamide or quinidine (class la drug) alone, and propranolol plus a class la drug until VT could no longer be induced. All six patients in group A responded to propranolol alone. In group B, one patient responded to verapamil alone, and two patients responded to propranolol plus verapamll. In group C, three patients responded to propranolol alone, one patient responded to a class la drug alone, and one patient responded to propranolol plus a class la drug. During a follow-up of 7 to 37 (17.9 -t 10.7) (-tS. D.) months, VT has not recurred in any patient. Three patients treated initially with propranolol alone have required substitution of amiodarone due to refractory congestive heart failure. In patients requiring isoproterenol for VT induction, @blockade alone appears to be effective in preventing reinduction of VT caused by enhanced automaticity. A heterogeneous response occurs when the VT mechanisms are triggered automaticity or reentry. (AM HEART J 1990;120:1347.)
Lorenzo A. DiCarlo,
Jr., MD, Frank Susser, DO, and Stuart A. Winston,
DO.
Ann Arbor, Mich.
From the Cardiac Electrophysiology Laboratory, St. Joseph Mercy Hospital of the Catherine McAuley Health Center, and the School of Medicine, University of Michigan. Received for publication May 21, 1990; accepted July 9, 1990. Reprint requests: Lorenzo A. DiCarlo, MD, Reichert Health R-3003, P.O. Box 994. Ann Arbor, MI 48106. 4/l/24130
Building,
Patients with recurrent, sustained monomorphic ventricular tachycardia (VT) sometimes require intravenous administration of ,&agonists such as isoproterenol for initiation of ventricular tachycardia in the cardiac electrophysiology laboratory.lv6 Traditionally, selection of appropriate antiarrhythmic 1347
American
27. Mirowski M. The automatic implantable cardioverterdefibrillator: an overview. J Am Co11 Cardiol 1985;6: 461-6. 28. Kelly PA, Cannom DS, Garan H, Mirabal GS, Harthorne JW, Hurvitz RJ, Vlahakes GJ, Jacobs ML, Ilvento JP, Buckley MJ, Ruskin JN. The automatic implantable cardioverter-defibrillator: efficacy, complications and survival in patients with
December 1990 Heart Journal
malignant ventricular arrhythmias. J Am Co11 Cardiol 1988; 11:1278-86. 29. Echt DS, Armstrong K, Schmidt P, Oyer P, Stinson E, Winkle RA. Clinical experience, complications, and survival in 70 patients with the automatic implantable cardioverter/defibrillator. Circulation 1985;71:289-96.
Efficacy and safety of monophasic and biphasic waveform shocks using a braided endocardial defibrillation lead system Endocardial lead systems for implantable cardioverter-defibrillators utilize large (12F) rigid catheters with spring defibrillation electrodes, and lead system failure has been observed during long-term implant. We evaluated a novel flexible 8F braided electrode catheter for pacing and defibrillation in canine experiments. Active fixation and pacing were accomplished using a screw-in distal electrode, and defibrillation pulses were delivered through a braided electrode. Two braided electrode catheters were positioned in the right ventricular apex (6 cm*) and in the superior vena cava-right atrial junction (5 cm*), respectively. An elliptical 13 cm* surface area patch electrode was positioned along the left lateral cardiac border. Ventricular fibrillation (VF) was induced and monophasic and asymmetric biphasic shocks (leading voltages 260 to 1000 V) were delivered via dual and triple electrode conflgurations in each animal using a prospective randomized crossover study design. Mean right ventricular pacing threshold was 0.5 & 0.2 mA, with a mean electrogram amplitude of 11.1 + 2.8 mV during sinus rhythm prior to fibrillation and defibrillation. Two hundred seven VF inductions (mean 30 + 4 per animal) were analyzed. The mean defibrillatton threshold could be reduced to 8.0 + 3.2 joules with biphasic shocks from 12.9 ? 5.1 joules obtained for monophasic shocks using a dual electrode system (jr < 0.004). Mean shock leading voltage was correspondingly reduced to 488 + 100 V from 691 + 154 V (p < 0.0006). The mean defibrillation threshold could be reduced to 10.7 + 3.4 joules with biphasic shocks from 14.8 f 4.9 joules for monophasic shocks using a triple electrode system (right ventriclej-]/patch and right atrium[+]; p < 0.02). Mean shock leading voltage was correspondingly reduced to 543 f 101 V from 717 + 114 V (p < 0.003). Pacing thresholds were unchanged after defibrillation (p > 0.05). We conclude that successful pacing and defibrillation is feasible with a small-caliber braided electrode catheter. Percutaneous insertion of one or two catheters permits use with dual and triple electrode configurations. Asymmetric biphasic waveform pulses reduce endocardial defibrillation threshold with this catheter electrode system. (AM HEART J 1990;120:1342.)
Sanjeev Saksena, MD, Steven E. Scott, BS, Peter R. Accorti, MS, Birinder K. Boveja, BS, Debra Abels, BS, and Frank J. Callaghan, Newark and Passaic, N.J., and Miami, Fla.
From the Division of Cardiology, UMDNJ-New Newark; The Eastern Heart Institute, Passaic; Systems, Inc., Miami.
Jersey Medical and Telectronics
Received
July
for publication
Feb.
12, 1990;
Reprint requests: Sanjeev Saksena, Boulevard, Passaic, NJ 07055. 4/l/24132
1342
MD,
accepted
The Eastern
School, Pacing
1. 1990. Heart
Institute.
350
MSEE.
Implantable cardioverter-defibrillators are being increasingly employed for the treatment of patients with life-threatening ventricular tachyarrhythmias. Endocardial lead systems have been proposed for use in conjunction with such devices.’ Unfortunately, the efficacy of prototype lead systems was limited for
Volume Number
120 6, Part
1
termination of both ventricular tachycardia (VT) and ventricular fibrillation (VF).2* 3 Recently, we have developed a triple electrode configuration permitting bidirectional shocks for clinical application4 and have demonstrated its clinical efficacy in converting both VT and VF.5-7 One clinical investigation was performed using a large (12F) tripolar electrode catheter with two defibrillation electrodes and one tip-sensing electrode used in conjunction with a submuscular patch electrode.3 Catheter electrode performance was characterized by poor maneuverability as well as by late conductor fracture, resulting in inappropriate shock delivery and even documented sudden death in selected patients.7 In an effort to improve the performance of endocardial defibrillation lead systems, we have developed a new braided endocardial defibrillation lead system (Telectronics Pacing Systems, Inc., Miami, Fla.). Furthermore, we have evaluated the efficacy of bidirectional and unidirectional shocks using monophasic and biphasic shock energy waveforms in an effort to reduce defibrillation energy requirements for the endocardial technique. In this report we summarize our initial evaluation of the efficacy and safety of this electrode system. METHODS Seven conditioned adult male mongrel dogs with weights ranging from 35 to 50 pounds were used. The dogs were anaesthetized using intravenous pentobarbitol sodium and were placed on a Harvard respirator (Harvard Apparatus Inc., S. Natick, Mass.) after intubation. Surface electrocardiogram electrodes were attached to the limbs and electrocardiographic monitoring was performed on a physiologic recorder. Hard copy recordings of the electrocardiograms were obtained on an eight-channel chart recorder. Arterial blood pressure recordings were obtained and cutaneous electrodes were used for external rescue defibrillation. Electrode system and technique. The braided endocardial defibrillation lead system employs two bipolar 8F electrode catheters. There is an electrically isolated active fixation screw-in helix with a porous annular pacing electrode. A defibrillation electrode of 5 or 6 cm length with electrode surface areas of 5 or 6 cm2 is placed proximal to the tip electrode. Using fluoroscopic guidance, a 6 cm2 braided endocardial defibrillation lead was introduced through the jugular vein and was positioned in the right ventricular apex. A 5 cm2 braided endocardial defibrillation lead was positioned in the superior vena cava. These leads were used in conjunction with a patch electrode (surface area of 13 cm2) positioned in a subcutaneous location on the left lateral thorax along the left cardiac border. Energy delivery modes. Two defibrillation shock energy waveforms were studied. The monophasic waveform utilized a truncated exponential voltage pulse of 5 msec du-
Braided
endocardiul
defibrillation
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ration delivered from a 60 rF capacitor in an external defibrillation unit. The asymmetric biphasic waveform consisted of a positive truncated exponential voltage pulse of 5 msec duration followed by a 1 msec delay and a subsequent negative truncated voltage pulse of 5 msec duration whose initial leading voltage magnitude was 50% of the positive pulse. Each pulse was delivered from a 60 PF capacitor and from the external defibrillation unit. Two defibrillation lead configurations were evaluated. In the bidirectional configuration, the negative (cathodal) electrode is the endocardial defibrillation lead located in the right ventricular apex and two positive (anodal) electrodes are used, consisting of the endocardial defibrillation lead in the superior vena cava cross-connected with the subcutaneous patch electrode. In the unidirectional configuration, the endocardial defibrillation lead in the right ventricular apex is still used as the cathodal electrode and a single anodal electrode consisting of the subcutaneous patch electrode is used. Thus in the bidirectional configuration dual current pathways are established, whereas in the unidirectional configuration a single current pathway is established. These pathways have been previously described.4p 6 Endocardial defibrillation threshold testing. Defibrillation thresholds were obtained for the following experimental configurations: (1) monophasic waveform-unidirectional lead configuration; (2) monophasic waveformbidirectional lead configuration; (3) asymmetric biphasic waveform-unidirectional lead configuration; (4) asymmetric biphasic waveform-bidirectional lead configuration. The animals were induced into VF using a 60 Hz signal. Initial defibrillation was attempted using an arbitrary starting voltage of 600 V based on prior studies. If the initial shock was a success/failure, the shock voltage used in subsequent arrhythmia inductions would be decreasedlincreased by 20% until failure/success was obtained. The lowest successful shock voltage achieving successful defibrillation was determined. Two or more additional arrhythmia inductions were then performed in order to achieve three consecutive successful VF terminations; this voltage was then considered the defibrillation threshold. Pacing and sensing evaluation. Unipolar pacing thresholds from the right ventricular endocardial defibrillation lead as well as R wave amplitude were analyzed in six animals. Pacing thresholds were obtained using 1 msec constant pulse, and unipolar R wave amplitude was averaged over 10 beats. Arterial blood pressure was monitored continuously during the experiment and during each VF induction and defibrillation. Study design and analysis. For adequate comparison of all four electrode configurations and shock energy modes, the sequence of application of each configuration was randomized using a prospective controlled crossover study design. This permitted equivalent testing of each electrode configuration in the total group of experiments. At the end of each experiment, the animal was sacrificed and the heart was removed for pathologic examination. The right atrium and right ventricle were exposed with the leads in place so
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0 0
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1. Endocardial ventricular electrogram amplitude (R wave) in the baselinestate and after endocardial defibrillation shockswith different configurations. There is a significant reduction in R wave amplitude with monophasicbidirectional shocksthat is small but statistically significant. The other configurations did not showa significant change.In all instancesthe R wave amplitude wasmore than adequatefor routine sensing.Values are representedas mean + 1 standard deviation. M, Monophasic; B, bidirectional; AB, asymmetric biphasic; U, unidirectional. Fig.
that lead placement or any noticeable endocardialand epirhythm was 11.1 cardial damage could be clearly observed. Defibrillation rectional shocks, threshold was obtained using the three consecutivesuccess ished to a mean methodsasdefinedabove.Statistical analysiswasperformed After monophasic usinga two-tailed paired-differenceStudent’s t test. RESULTS
Fluoroscopic guidance permitted successful positioning of the leads in all the animals evaluated. The patch electrode was placed subcutaneously in all animals. Unipolar endocardial ventricular pacing was accomplished using the braided endocardial defibrillation lead applying constant current pulses of 1 msec duration. The mean right ventricular endocardial pacing threshold before defibrillation threshold testing was 0.5 & 0.2 mA. After defibrillation threshold testing with monophasic bidirectional shocks, mean right ventricular pacing threshold was 0.6 +- 0.1 mA (p > 0.05), and after monophasic unidirectional shocks it was 0.6 * 0.1 mA (p > 0.05). After asymmetric biphasic shocks delivered with the bidirectional configuration, the mean bipolar pacing threshold was 0.6 f 0.1 mA (p > 0.05). After asymmetric biphasic shocks using the unidirectional current pathway, the pacing threshold was 0.7 +- 0.2 mA (p > 0.05). Electrogram amplitudes are shown in Fig. 1. The mean right ventricular unipolar electrogram amplitude (R wave) in the control state during sinus
* 2.8 mV. After monophasic bidithe amplitude of the R wave diminvalue of 6.8 + 2.8 mV (p < 0.05). unidirectional shocks, the mean R wave amplitude was 9.1 -t 3.7 mV (p > 0.05). After asymmetric biphasic shocks using a bidirectional configuration, the mean R wave amplitude was 7.7 f 3.6 mV (p > 0.05). After asymmetric biphasic shocks using a unidirectional configuration, the mean R wave amplitude was 10.8 f 3.4 mV (p > 0.05). Defibrillation thresholds obtained using the four different shock and electrode configurations are shown in Fig. 2. The mean defibrillation threshold in the study group using monophasic shocks and a unidirectional configuration was 12.94 t- 5.08 joules, with a mean shock leading voltage of 691 ? 154 V. With asymmetric biphasic shocks using a unidirectional electrode configuration, the mean defibrillation energy threshold declined to 8.02 of: 3.20 joules (p = 0.0026 compared with monophasic values), with a mean shock leading votage of 488 * 100 V. The mean defibrillation threshold using monophasic shocks and a bidirectional electrode configuration was 14.77 f 4.94joules,withameanshockleadingvoltage of 717 & 114 V. Endocardial defibrillation threshold declined to 10.70 * 3.35 joules using asymmetric biphasic energy waveforms in the same bidirectional
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2. Defibrillation threshold energiesasobtained by the three consecutivesuccessmethods(in Joules). Individual data points are shownand actual delivered energy was measured.DFT, Defibrillation threshold; other abbreviations as in legend to Fig. 1.
Fig.
configuration 0, = 0.0196 compared with monophasic pulses), with a mean shock leading voltage of 542 & 101 V. There was no significant difference in mean defibrillationthreshold using a bidirectional or unidirectional shock configuration with monophasic energy waveforms. In this study, there was also a significant reduction in defibrillation threshold using an asymmetric biphasic waveform with a unidirectional pathway compared with the monophasic waveform with a bidirectional pathway (p = 0.0005). There was also a significant reduction in mean defibrillation threshold using asymmetric biphasic shock waveforms with the bidirectional electrode configuration compared with a monophasic energy waveform with a unidirectional pathway (p = 0.039). Pathologic findings. Gross pathologic findings were largely localized to the site of the catheter electrode. The junction of the superior vena cava and right atrium did not show any significant abnormalities. There was focal hemorrhage and necrosis at the site of lead insertion in the right ventricle. The epicardial surface was usually normal but extension to this area was observed in one animal. There was focal hemorrhage noted in the right atrioventricular valve leaflet adjacent to the lead entrance into the right ventricle in one animal. DISCUSSION
Transvenous defibrillation lead systems have been studied since the early developmental period of implantable defibrillation devices.l, * Initial evaluation
of a transvenous dual electrode catheter demonstrated unreliable VF termination and high defibrillation thresho1ds.l Subsequently, low-energy cardioversion of sustained VT with endocardial shocks was noted in selected patients8 Evaluation in a prospective controlled clinical trial elicited limited efficacy.2 Efficacy of low-energy endocardial cardioversion was determined by tachycardia rate and absolute shock energy. Rapid VT and VF could not be terminated reliably, even at high shock energies. Electrophysiologic effects of these shocks included slowing and interruption of conduction in the slowly conducting limb of the tachycardia circuit as well as modification of the refractoriness in these tissues9 In an effort to obtain wider electrophysiologic effects, we reported use of a triple electrode system employing a Medtronic 6880 tripolar catheter (Medtronic Inc., Minneapolis, Minn.) and thoracic patch electrodes permitting dual current pathways in man47 lo Reduction in cardioversion thresholds and successful endocardial defibrillation have been possible with this approach.4y 5 This electrode system employs a single right ventricular cathode and dual anodes in the superior vena cava and the left lateral thoracic region. In a recent clinical report with a subsequent catheter electrode,7 9 of 10 patients had successful endocardial defibrillation with a mean defibrillation energy threshold of 18 +- 5 joules. Previous clinical studies employed truncated exponential monophasic shock energy waveforms for endocardial cardioversion and defibrillation.7 Exper-
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imental evidence suggests that asymmetric biphasic shock energy waveforms reduce defibrillation energy thresholds for transthoracic and epicardial electrode systems.“, l2 Studies on the cellular electrophysiologic basis for this observation have suggested that the period of cell membrane dysfunction and electrical arrest induced by high-energy shocks is abbreviated by biphasic waveforms.13 This shock waveform may restore membrane function and integrity. One recent clinical studyI has, however, suggested that reduction in defibrillation energy requirements by biphasic shocks is most frequently observed in patients with low monophasic shock energy requirements for epicardial defibrillation, This would limit the usefulness of this approach to a selected subgroup of patients when it was applied using epicardial lead systems. This study evaluated the value of biphasic shocks when applied through endocardial lead systems. Application of biphasic shocks through this new endocardial lead system was evaluated for two different lead configurations. The braided endocardial lead system permits dual-chamber sensing, pacing, and variable current pathways for defibrillation shocks. This pacing and defibrillation endocardial lead is significantly smaller in diameter, with greater flexibility and maneuverability for endocardial placement. It is similar in many respects to current dualchamber endocardial pacing lead systems. Endocardial lead placement is accomplished using conventional dual-chamber pacemaker implantation techniques. l5 In conjunction with a subcutaneous left thoracic patch electrode, this triple electrode system permits use of a variety of single or dual current pathways. 4, 5 It also permits bipolar endocardial pacing and sensing, thus avoiding the chronic pacing threshold and sensing electrogram changes observed with epicardial systems. l6 Endocardial shock delivery did not significantly alter pacing thresholds, as has been observed in other lead systems.17t I8 Sensing R wave amplitude did show a trend to a small decrease after endocardial defibrillation. In this study, asymmetric biphasic shocks reduced endocardial defibrillation energy requirements when compared with monophasic shocks for one single and one dual current pathway. The mean reduction in endocardial defibrillation threshold was 38% for unidirectional shocks and 28 % for bidirectional shocks (p < 0.05). The study suggests that in canine experiments endocardial defibrillation thresholds can be reduced for the two energy pathways studied using this lead system. Clearly, this cannot be extrapolated to other current pathways, energy delivery patterns employing multiple or sequential shocks,
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or other electrode systems. A single current pathway was more advantageous in this study despite a smaller electrode surface area (19 cm2 versus 24 cm2), suggesting that surface area may be only one of several important variables. Due to significant differences between canine and human thoracic anatomy, clinical evaluation of this lead system with biphasic and monophasic shocks will be necessary to establish the value of biphasic endocardial shocks. Should similar observations be obtained, this will permit wider application of endocardial leads and a significant reduction in pulse generator size. This may avoid the current need for abdominal implantation sites. Conventional insertion techniques used for permanent pacing lead systems can be employed. We expect that the braided endocardial defibrillation lead system will help establish the principle of generic pacing and defibrillation lead for clinical application. The authors Ellen Wendler
acknowledge the valuable assistance in the preparation of the manuscript.
of Mrs.
Ina
REFERENCES
1. Mirowski M, Mower MM, Gott VL. Brawley RK. Feasibility and effectiveness of low energy catheter defibrillation in man. Circulation 1973;47:79-85. 2. Ciccone JM, Saksena S, Shah Y, Pantopoulos D. A prospective, randomized study of the clinical efficacy and safety of transvenous cardioversion for ventricular tachycardia termination. Circulation 1985;71:571-8. 3. Saksena S, An H. Clinical efficacy of dual electrode systems for endocardial cardioversion of ventricular tachycardia: a prospective randomized crossover trial. AM HEART J 1990;119:1522. 4 Saksena S, Calvo RA, Pantopoulos D, Gadhoke A, Rothbart ST. A prospective evaluation of single and dual current pathways for transvenous cardioversion in rapid ventricular tachycardia. PACE 1987;10:1130-41. 5. Saksena S, Parsonnet V. Implantation of a cardioverterl defibrillator without thoracotomy using a triple electrode system. JAMA 1988;259:69-72. 6. Lindsay BD, Saksena S, Rothbart ST, Wasty N, Pantopoulos D. Prospective evaluation of a sequential pacing and high-energy bidirectional shock algorithm for transvenous cardioversion in patients with ventricular tachvcardia. Circulation 1987;76:601-9. 7. Saksena S, Tullo NG, Krol RB, Mauro AM. Initial clinical experience with endocardial defibrillation usina an imnlantable cardioverter/defibrillator with a triple electrode systkm. Arch Intern Med 1989;149:2333-9. 8. Zipes DP, Jackman WM, Heger JJ, Chilson DA, Browne KF, Naccarelli GV, Rahilly GT, Prystowsky EN. Clinical transvenous cardioversion of recurrent life-threatening tachyarrhythmias: low energy synchronized cardioversion of ventricular tachycardia and termination of ventricular fibrillation in patients using a catheter electrode. AM HEART J 1982; 103:789-
94. 9. Saksena S, Pantopoulos D, Hussain SM, Gielchinsky I. Mechanisms of ventricular tachycardia termination and acceleration during transvenous cardioversion as determined by cardiac mapping in man. AM HEART J 1987;113:1495-506. 10. Saksena S, Calvo RA, Pantopoulos D, Gordon S, Gadhoke A. Simultaneous shocks for ventricular tachycardia cardiover-
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sion: effect of electrode position on efficacy [Abstract]. Clin Res 1986:34:341A. Schuder JC, Gold JH, Stoeckle M, McDaniel WC, Cheung KN. Transthoracic ventricular defibrillation in the 100 ka calf with symmetrical one-cycle bidirectional rectangular wave stimuli. IEEE Trans Biomed Eng 1983;30:415-22. Tane AS. Yabe S. Wharton JM. Dolker M. Smith WM. Ideker RE. Ventricular defibrillation using biphasic wavefor’&- the importance of phasic duration. J Am Co11Cardiol1989,13:20714. Jones JL, Jones RE. Decreased defibrillator-induced dysfunction with biphasic rectangular waveforms. Am J Physiol 1984;247:H792-6. Winkle RA, Mead RH, Ruder MA, Gandiani V, Buch WS, Pless B. Sweenev M. Schmidt P. Imuroved low enerev defibrillation efficacy in man with the use of biphasic tru;cated exponential waveform. AM HEART J 1989;117:122-7. Holmes DR, Holmes DR Jr. Pacemaker implantation tech-
niques. In: Saksena S, Goldschlager N, eds. Electrical therapy for cardiac arrhythmias. Philadelphia: WB Saunders Co, 1990:173-90. 16. Timmis GC. The electrobiology and engineering of pacemaker leads. In: Saksena S, Goldschlager N, eds. Electrical therapy for cardiac arrhythmias. Philidelphia: WB Saunders Co, 1990:35-90. 17. Van Vleet JF, Tacker WA Jr, Bourland JD, Kallok MJ, Schollmeyer MP. Cardiac damage in dogs with chronically implanted automatic defibrillator electrode catheters and given four episodes of multiple shocks. AM HEART J 1983; 106:300-7. 18.
Waspe LE, Kim SG, Matos JA, Fisher JD. Role of a catheter lead system for transvenous countershock and pacing during electrophysiologic tests: an assessment of the usefulness of catheter shocks for terminating ventricular tachyarrhythmias. Am J Cardiol 1983;52:477-84.
The role of ,&blockade therapy for ventricular tachycardia induced with isoproterenol: A prospective analysis lsoproterenol is sometimes required for ventricular tachycardia (VT) induction. However, the role of Pblockade for treatment of such VT has not been critically assessed. The use of B-blockade was evaluated prospectively in 14 consecutive patients who required isoproterenol 2.4 + 1.3 (? S. D.) pg/min to induce sustained monomorphic VT (>30 seconds, or requiring termination due to hemodynamic collapse) after a negative baseline study. The VT mechanisms were enhanced automaticity (group A, six patients), triggered automaticity (group B, three patients), and reentry (group C, five patients). Groups A and B had serial intravenous electropharmacologic tests with propranolol alone (0.2 mg/kg), verapamil alone (0.15 mg/kg), and propranolol plus verapamil, and group C had serial tests with propranolol alone, procainamide or quinidine (class la drug) alone, and propranolol plus a class la drug until VT could no longer be induced. All six patients in group A responded to propranolol alone. In group B, one patient responded to verapamil alone, and two patients responded to propranolol plus verapamll. In group C, three patients responded to propranolol alone, one patient responded to a class la drug alone, and one patient responded to propranolol plus a class la drug. During a follow-up of 7 to 37 (17.9 -t 10.7) (-tS. D.) months, VT has not recurred in any patient. Three patients treated initially with propranolol alone have required substitution of amiodarone due to refractory congestive heart failure. In patients requiring isoproterenol for VT induction, @blockade alone appears to be effective in preventing reinduction of VT caused by enhanced automaticity. A heterogeneous response occurs when the VT mechanisms are triggered automaticity or reentry. (AM HEART J 1990;120:1347.)
Lorenzo A. DiCarlo,
Jr., MD, Frank Susser, DO, and Stuart A. Winston,
DO.
Ann Arbor, Mich.
From the Cardiac Electrophysiology Laboratory, St. Joseph Mercy Hospital of the Catherine McAuley Health Center, and the School of Medicine, University of Michigan. Received for publication May 21, 1990; accepted July 9, 1990. Reprint requests: Lorenzo A. DiCarlo, MD, Reichert Health R-3003, P.O. Box 994. Ann Arbor, MI 48106. 4/l/24130
Building,
Patients with recurrent, sustained monomorphic ventricular tachycardia (VT) sometimes require intravenous administration of ,&agonists such as isoproterenol for initiation of ventricular tachycardia in the cardiac electrophysiology laboratory.lv6 Traditionally, selection of appropriate antiarrhythmic 1347