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opinions and hypotheses Biventricular Cardiac Pacing* Promising New Therapy for Congestive Heart Failure S. Serge Barold, MD (CHEST 2000; 118:1819 –1821) Abbreviations: CHF ⫽ congestive heart failure; LV ⫽ left ventricle; NYHA ⫽ New York Heart Association; RV ⫽ right ventricle ual-site or multisite ventricular pacing has reD cently emerged as a possible new modality for 1 the treatment of patients with dilated cardiomyopathy and congestive heart failure (CHF) associated with major intraventricular and interventricular conduction disorders. Multisite ventricular pacing or resynchronization reduces the degree of electromechanical asynchrony by altering the pathways of spontaneous depolarization. Modified activation is translated into potentially beneficial long-term hemodynamic1,2 and antiarrhythmic effects.3,4 In 1994, Cazeau et al5 from France reported the remarkable benefit of biventricular pacing in a patient with drug-refractory CHF, dilated cardiomyopathy, and left bundle-branch block (QRS ⫽ 200 ms). The left ventricle (LV) and right ventricle (RV) were paced simultaneously to achieve a more physiologic depolarization sequence. Cazeau et al5 demonstrated in a preoperative study that the benefit of biventricular pacing was in part due to improved atrioventricular synchrony and in part to ventricular resynchronization. Follow-up observations showed a sustained improvement that depended on correct function of the LV lead. Since this report, a substantial number of short-term studies have shown that biventricular pacing improves hemodynamics in CHF patients with severe left ventricular systolic dysfunction and major left-sided intraventricular conduction disorders.6 –10 A longer spontaneous QRS complex may be predictive of a greater positive response to pacing.9,11 In some patients, single-site pacing from the LV provides better hemodynamics than simultaneous biventricular pacing.6,9 *From the Electrophysiology Institute, Broward General Hospital, Ft. Lauderdale, FL. Correspondence to: S. Serge Barold, MD, 6237 NW 21st Court, Boca Raton, FL 33496; e-mail: [email protected] Intraventricular and interventricular conduction delays cause an inefficient dyssynchronous pattern of left ventricular activation with segments contracting at different times. Consequently, there is a shorter diastole and/or overlapping systole/diastole and aggravation of functional mitral regurgitation. The rationale of biventricular pacing is to improve the sequence of electrical activation (resynchronization) and create a more coordinated and efficient left ventricular contraction.5,12–14 Resynchronization may also reduce functional mitral regurgitation.15 Patients with chronic atrial fibrillation may also benefit.16 –18 In this instance, continual biventricular pacing often requires radiofrequency ablation of the AV junction to ensure control of ventricular depolarization by the pacemaker.19 Only 20 to 30% of class III or class IV CHF patients have conduction disorders (QRS ⬎ 140 ms) that make them potential candidates for long-term biventricular pacing.19,20 More refined and sensitive markers of left ventricular dyssynchrony than the simple ECG need to be investigated to extend the benefit of biventricular pacing to other CHF patients in the absence of an obvious left-sided intraventricular conduction disorder or even in the presence of right bundle-branch block. Presentations on biventricular pacing for the treatment of CHF dominated the 21st annual meeting of the North American Society of Pacing and Electrophysiology in Washington, DC, in May 2000, where the preliminary results of the first randomized trial of this therapy were reported.21 The Multisite Stimulation in Cardiomyopathy Trial is a randomized crossover singleblind study of biventricular pacing in CHF patients with stable sinus rhythm and a major intraventricular conduction disorder. Biventricular pacing was activated for 3 months and turned off for 3 months. The study, involving 63 patients (left ventricular ejection fraction, 22 ⫾ 8%), revealed statistically significant improvements in the 6-min walking distance, New York Heart Association (NYHA) class, and quality-of-life score, and a reduction in hospitalizations.22 Observational longterm results of biventricular pacing in patients with CHEST / 118 / 6 / DECEMBER, 2000 Downloaded From: http://publications.chestnet.org/pdfaccess.ashx?url=/data/journals/chest/21955/ on 05/08/2017 1819 dilated cardiomyopathy and CHF, either idiopathic or due to coronary artery disease, are also encouraging.1,2,12,19,23–27 A major ongoing prospective, nonrandomized, multicenter study of ventricular resynchronization2 is being conducted in patients with NYHA class III/IV drug-refractory CHF, left ventricular dysfunction (left ventricular ejection fraction ⱕ 35%), left ventricular end-diastolic diameter ⱖ 60 mm, and a ventricular conduction delay QRS ⱖ 150 ms. A long PR interval is not a prerequisite. The 12-month results in survivors of an initial group of 103 patients suggest that the benefits of ventricular resynchronization are sustained through 12 months with a statistically significant reduction of the NYHA class, and improvement in the 6-min hall walk distance and the quality-of-life score. A French pilot study1 of biventricular pacing initiated between March 1995 and December 1997 included 53 patients (68% in class IV NYHA) with severe drug-refractory CHF (mean left ventricular ejection fraction, 19.8% ⫾ 6.6; coronary artery disease in 57%; mean QRS duration, 191 ⫾ 36 ms; and permanent atrial fibrillation in 42%). During a mean follow-up period of 15.7 ⫾ 10.8 months, the mean NYHA class decreased from 3.7 ⫾ 0.5 at the time of implantation to 2.3 ⫾ 0.5 at 1 month (p ⬍ 0.001) and remained stable (2.5 ⫾ 0.70) until the end of the follow-up period. The high and early mortality rate after biventricular pacing seems to reflect primarily the severity of heart disease rather than the deleterious long-term effect of pacing because this modality has been tried largely in very sick CHF patients refractory to drug therapy. Consequently, there may be a role for a combined biventricular pacemaker and defibrillator because sudden cardiac death accounts for 30 to 50% of the deaths in class IV patients.3,4,19,28 –31 Longer follow-up and other controlled studies will be required to determine the role and safety of biventricular pacing in the treatment of CHF and its impact on survival. Meaningful comparison of results will require standardization of patient groups, drug therapy, and the different noninvasive and invasive follow-up procedures presently used by investigators. At this time, long-term biventricular pacing is still considered investigational in the United States. So far, biventricular pacing has been accomplished with somewhat modified conventional hardware.19,32 The critical left ventricular pacing site for optimal hemodynamics varies from patient to patient.33–34 The apex may not necessarily be the best site in the RV. Significant shortening of the QRS complex by biventricular pacing may be a marker of a favorable longterm clinical response.25 The LV is often paced from one of the tributaries of the coronary veins over the epicardial surface of the LV.32,35 After a learning curve, access can be achieved in up to 90% and is limited by variability in venous anatomy.2,36 Left ventricular pacing can also be done with a limited thoracotomy, a procedure generally considered undesirable in highrisk patients. A few patients have received two pacemakers synchronized to fire simultaneously in each ventricle.37 The placement of permanent endocardial LV leads by transseptal puncture is feasible, but it is highly investigational because of the risk of catastrophic embolic complications, even with anticoagulants.38 – 40 Multisite or left ventricular pacing is a promising new therapeutic modality with great potential because of the very large and growing number of patients with CHF. The ultimate success of the ambitious efforts to resynchronize cardiac activity in CHF will depend on defining its real benefit in a variety of circumstances by rigorous scientific evaluation and the development of new technology or further refinement of existing technology.41 For example, adjusted RV-LV stimulation delay—rather than simultaneous activation—may enhance the hemodynamic response.42 Based on short-term data, it is possible that in some patients, long-term singlesite left ventricular pacing may be hemodynamically superior to biventricular pacing, probably because right ventricular pacing may activate a substantial portion of the LV, thereby interfering with the resynchronization process provided by left ventricular pacing alone. This would have an enormous impact on the methodology of pacing. References 1 Leclercq C, Cazeau S, Alonso C, et al. Multisite biventricular pacing in advanced heart failure: current status of the French Pilot Study [abstract]. Pacing Clin Electrophysiol 1999; 22: 733 2 Gras D, Ritter P, Lazarus A, et al. Long-term outcome of advanced heart failure patients with cardiac resynchronization therapy [abstract]. Pacing Clin Electrophysiol 2000; 23:658 3 Daubert JC, Mabo P, Gras D, et al. Dual-site ventricular pacing for prevention of ventricular tachycardia in patients with intraventricular conduction block [abstract]. Eur J Cardiac Pacing Electrophysiol 1996; 6:134 4 Ramaswamy K, Zagrodsky JD, Page RL, et al. Biventricular pacing decreases the inducibility of sustained monomorphic ventricular tachycardia [abstract]. Pacing Clin Electrophysiol 2000; 23:748 5 Cazeau S, Ritter P, Bakdach S, et al. Four chamber pacing in dilated cardiomyopathy. Pacing Clin Electrophysiol 1994; 17:1974 –1979 6 Blanc JJ, Etienne Y, Gilard M, et al. Evaluation of different ventricular pacing sites in patients with severe heart failure: results of an acute hemodynamic study. Circulation 1997; 96:3273–3277 7 Auricchio A, Stellbrink C, Block M, et al. Effect of pacing chamber and atrioventricular delay on acute systolic function of paced patients with congestive heart failure: the Pacing Therapies for Congestive Heart Failure Study Group. The Guidant Congestive Heart Failure Research Group. Circulation 1999; 99:2993–3001 1820 Downloaded From: http://publications.chestnet.org/pdfaccess.ashx?url=/data/journals/chest/21955/ on 05/08/2017 Editorials 8 Leclercq C, Cazeau S, Le Breton H, et al. Acute hemodynamic effects of biventricular pacing in patients with endstage heart failure. J Am Coll Cardiol 1998; 32:1825–1831 9 Kass DA, Chen HC, Curry C, et al. Improved left ventricular mechanics from acute VDD pacing in patients with dilated cardiomyopathy and ventricular conduction delay. Circulation 1999; 99:1567–1573 10 Saxon LA, Kerwin WF, Cahalan MK, et al. Acute effects of intraoperative multisite ventricular pacing on left ventricular function and activation/contraction sequence in patients with depressed ventricular function. J Cardiovasc Electrophysiol 1998; 9:13–27 11 Kadhiresan V, Vogt J, Auricchio A, et al. Sensitivity and specificity of QRS duration to predict acute benefit in heart failure patients with cardiac resynchronization [abstract]. Pacing Clin Electrophysiol 2000; 23:555 12 Kerwin WF, Botnivick EH, O’Connell JW, et al. Ventricular contraction abnormalities in dilated cardiomyopathy: effect of biventricular pacing to correct interventricular dyssynchrony. J Am Coll Cardiol 2000; 35:1221–1227 13 Varma C, Callaghan PO, New C, et al. Does acute multisite pacing for heart failure improve ventricular coordination [abstract]? Circulation 1999; 100(suppl I):I-514 14 Liu l, Tockman B, Belalcazar A, et al. Heart failure therapies improve left ventricular electromechanical coordination in a canine model of left bundle branch block [abstract]. Circulation 1999; 100(suppl I):I-122 15 Etienne Y, Valls-Bertault V, Mansourati J, et al. Permanent left ventricular-based pacing improves mitral regurgitation in patients with severe congestive heart failure [abstract]. Pacing Clin Electrophysiol 2000; 23:596 16 Etienne Y, Mansourati J, Gilard M, et al. Evaluation of left ventricular based pacing in patients with congestive heart failure and atrial fibrillation. Am J Cardiol 1999; 83:1138 –1140 17 Leclercq C, Alonso C, Victor F, et al. Long-term results of permanent biventricular pacing in patients with advanced heart failure: comparison of patients with stable sinus rhythm and chronic atrial fibrillation [abstract]. Pacing Clin Electrophysiol 2000; 23:635 18 Leclercq C, Victor F, Alonso C, et al. Comparative effects of permanent biventricular pacing for refractory heart failure in patients with stable sinus rhythm or chronic atrial fibrillation. Am J Cardiol 2000; 85:1154 –1156 19 Daubert JC, Leclercq C, Alonso C, et al. Long-term experience with biventricular pacing in refractory heart failure. In: Ovsyshcher IE, ed. Cardiac arrhythmias and device therapy: results and perspectives for the new century, Armonk, NY: Futura, 2000; 385–392 20 Saxon LA, Boehmer JP, Hummel J, et al. Biventricular pacing in patients with congestive heart failure: two prospective randomized trials. Am J Cardiol 1999; 83:120D–123D 21 Abstracts for the 21st annual meeting the North American Society of Pacing and Electrophysiology, Washington DC. Pacing Clin Electrophysiol 2000; 23:553– 801 22 Daubert C. Preliminary results of the MUSTIC trial of biventricular pacing for congestive heart failure. Presented at: 21st annual meeting of the North American Society of Pacing and Electrophysiology; May 2000; Washington, DC 23 Leclercq C, Alonso C, Mabo P, et al. Comparison of the effects of cardiac resynchronization in patients with advanced heart failure of either ischemic or non-ischemic origin [abstract]. Pacing Clin Electrophysiol 2000; 23:659 24 Bakker PF, Meijburg H, De Jonge N, et al. Beneficial effects of biventricular pacing in congestive heart failure [abstract]. Pacing Clin Electrophysiol 1994; 17:820 25 Alonso C, Leclercq C, Victor F, et al. Electrocardiographic predictive factors of long-term clinical improvement with 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 multisite biventricular pacing in advanced heart failure. Am J Cardiol 1999; 84:1417–1421 Tang ASL, Green M, Gras D, et al. Cardiac resynchronization: multicenter implant experience with atrio-biventricular pacing [abstract]. Pacing Clin Electrophysiol 1999; 22:701 Sack S, Auricchio A, Kadhiresan V, et al. Long-term improvement with ventricular resynchronization therapy in heart failure patients: does etiology of heart failure matter [abstract]? Pacing Clin Electrophysiol 2000; 23:555 Walker S, Levy T, Rex S, et al. Preliminary results with the simultaneous use of implantable cardioverter defibrillators and permanent biventricular pacemakers: implications for device interaction and development. Pacing Clin Electrophysiol 2000; 23:365–372 Higgins S, Yong P, Scheck D, et al, for the Ventak CHF Investigators. Biventricular pacing may diminish ICD shocks [abstract]. Pacing Clin Electrophysiol 1999; 22:848 Stellbrink C, Auricchio A, Diem B, et al. Potential benefit of biventricular pacing in patients with congestive heart failure and ventricular tachyarrhythmia. Am J Cardiol 1999; 83: 143D–150D Leclercq C, Alonso C, Pavin D, et al. Mortality in patients treated with permanent biventricular pacing for advanced heart failure: a 5 year single center experience [abstract]. Pacing Clin Electrophysiol 2000; 23:610 Daubert JC, Leclercq C, Pavin D, et al. Pacing therapy in congestive heart failure: present status and new perspectives. In: Barold SS, Mugica J, eds. Recent advances in cardiac pacing: goals for the 21st century. Armonk, NY: Futura, 1998; 51– 80 Gras D, Mabo P, Bucknall C, et al. Does lead placement affect outcome of cardiac resynchronization in heart failure patients? Results from the InSync trial [abstract]. Pacing Clin Electrophysiol 2000; 23:580 Auricchio A, Butter C, Stellbrink C, et al. Effect of left ventricular stimulation site on the systolic function of heart failure patients during ventricular resynchronization therapy [abstract]. Pacing Clin Electrophysiol 2000; 23:589 Daubert JC, Ritter P, Le Breton H, et al. Permanent left ventricular pacing with transvenous leads inserted into the coronary veins. Pacing Clin Electrophysiol 1998; 21:239 –245 Ritter P, Gras D, Daubert C, on behalf of the MUSTIC Group. Implant success rate of the transvenous left ventricular lead in the MUSTIC trial [abstract]. Pacing Clin Electrophysiol 2000; 23:580 Auricchio A, Stellbrink C, Sack S, et al. The Pacing Therapies for Congestive Heart Failure (PATH-CHF) Study: rationale, design, and endpoints of a prospective randomized multicenter study. Am J Cardiol 1999; 83:130D–135D Jaı̈s P, Douard H, Shah D, et al. Endocardial biventricular pacing. Pacing Clin Electrophysiol 1998; 21:2128 –2131 Leclercq F, Hager FX, Marcia JC, et al. Left ventricular lead insertion using a modified transseptal catheterization technique: a totally endocardial approach for permanent biventricular pacing in end-stage heart failure. Pacing Clin Electrophysiol 1999; 22:1570 –1575 Leclercq F, Kassnasrallah S, Macia JC, et al. Transcranial Doppler detection of microemboli during endocardial biventricular pacing in end-stage heart failure [abstract]. J Am Coll Cardiol 2000; 35(suppl A):141A Walker S, Levy TM, Coats AJ, et al. Biventricular pacing in congestive cardiac failure: current experience and future directions. The Imperial College Cardiac Electrophysiology Group. Eur Heart J 2000; 21:884 – 889 Butter C, Auricchio A, Stellbrink C, et al. Non-simultaneous biventricular stimulation: a new paradigm of ventricular resynchronization therapy for heart failure patients [abstract]. Pacing Clin Electrophysiol 2000; 23:589 CHEST / 118 / 6 / DECEMBER, 2000 Downloaded From: http://publications.chestnet.org/pdfaccess.ashx?url=/data/journals/chest/21955/ on 05/08/2017 1821