Nuevas indicaciones para marcapaseo

 Abstract

New indications have recently appeared for cardiac pacing with haemodynamic and antiarrhythmic objectives without any symptomatic bradycardia. The best documented indication, though relatively rare, is stimulation of obstructive hypertrophic cardiomyopathy; initially reserved for cases with favorable results of an acute haemodynamic test, it is now used in other cases without this criterion; hypertrophic cardiomyopathy without permanent obstruction, atrial fibrillation or left bundle branch block. The improvement observed during follow-up is always greater as a real remodeling of the myocardium seems to occur with ventricular dilatation and/or septal thinning. However, the position of the atrial, and above all, of the ventricular pacing catheters is critical as is regulation of the pacemaker which should allow complete ventricular capture with an AV delay allowing good filling. The follow-up of these patients must therefore be regular and the effects on longevity are unknown. DDD pacing has also been proposed in dilated cardiomyopathy. The results are contradictory and only very selected cases with left bundle branch block and long PR interval seem justified with, again, optimisation of the pacing sites with high septal or biventricular stimulation. Recurrent atrial tachycardia, special algorithms preventing extrasystoles have been tried with variable results. In cases with inter-atrial block, atrial resynchronisation by bi-atrial stimulation has been assessed with promising results but many technical problems remain unsolved.*1

Abstract

In view of the large number of inappropriate shocks observed in patients with implanted defibrillators, improved detection of ventricular arrhythmias has become a major objective. The addition of an atrial catheter has been proposed to improve discrimination between ventricular and non-ventricular arrhythmias. Besides this function, the additional catheter could be used for DDD pacing without risk of interaction between the pacemaker and defibrillator. The authors report their initial experience in 16 patients implanted with a DDD pacemaker. The indication was resuscitated sudden death (N = 5) or ventricular tachycardia (N = 11). The choice of a DDD defibrillator was justified by a bradycardia (N = 9), haemodynamic factors (N = 4) or supraventricular tachycardia (N = 3). The devices used were the Defender 9001 (ELA Medical SA, France, N = 3), the Ventak AV 1810 and the Ventak AV II DR 1821 (Guidant/CPI, Inc. USA, N = 11 and N = 2 respectively). There were three immediate complications. After 2 to 29 months' follow-up, 5 patients had received appropriate treatment by their devices. Five patients had inappropriate shocks : one patient received a shock triggered by electrical interference, two others had no active sensing algorithme when the shocks were delivered, and the other two had an activated algorithme with 1/1 conduction of a supraventricular arrhythmia. No recurrences were recorded after reprogramming the device. DDD or VDD pacing was permanent in 9 patients and intermittent in 3 others. Seven patients had dilated cardiomyopathy and severe cardiac failure and were clinically improved by dual chamber pacing. In many patients, candidates for a defibrillator, this new generation of devices has improved specificity of arrhythmia detection and cardiac pacing without risk of interaction. The authors propose a classification of the indications for a DDD defibrillator.*2

Abstract

T he Dual Chamber and VVI Implantable Defibrillator (DAVID) trial randomized 506 patients and tested the hypothesis that the dual-chamber pacing mode would produce improved hemodynamics and would in turn reduce congestive heart failure, heart failure hospitalizations, heart failure deaths, atrial fibrillation, strokes, ventricular arrhythmias, and total mortality compared to backup ventricular pacing in patients indicated for implantable defibrillator therapy. Patients had either primary prevention indications (47%) or secondary prevention indications (53%) for implantable defibrillator therapy but had no indications for bradycardia pacemaker support. All the patients had moderate to severe left ventricular dysfunction with a left ventricular ejection fraction of 40% or less (mean = 27%) and were consistently treated with angiotensin converting enzyme inhibitors or angiotensin II receptor blockers (86%) and beta adrenergic blocking agents (85%). The primary combined endpoint of hospitalization for congestive heart failure or death was paradoxically increased and statistically significant ( p = 0.03) at one year in the patients paced in the dual chamber mode (22.6%) compared to patients randomized to ventricular backup pacing (13.3%). Both heart failure hospitalization and mortality contributed outcome. Another perspective would consider this a randomized controlled study of presence or absence of pacemaker therapy in patients with left ventricular dysfunction and indications for implantable defibrillator therapy. Ventricular backup pacing produced less than 3% ventricular and no atrial pacing, while dual chamber pacing produced approximately 60% atrial and ventricular paced heart beats. The poor outcome in the dual chamber paced group correlated with the percentage of right ventricular pacing and suggests that right ventricular pacing caused ventricular dyssynchrony. The poor outcome associated with right ventricular pacing compared to intrinsic activation in the control group of the DAVID trial is reminiscent of the poor outcome associated with prolonged intraventricular conduction activation in the control groups compared to biventricular pacing in the intervention groups of the cardiac resynchronization trials. The direct conclusion from these results are that patients with indications for implantable defibrillators and no indication for pacing should not be paced in the dual chamber pacing mode. It is not appropriate to conclude that only single chamber implantable defibrillators should be implanted. There are other potential advantages to having an implanted atrial lead including improved secondary outcomes. However the DAVID trial results suggest that the dual chamber paced mode was not associated with improved quality of life or decreased frequency of hospitalization, inappropriate shocks from the defibrillator or atrial fibrillation. The more important question is what is the optimal pacing mode in these patients? The AAIR mode is under investigation in the DAVID II study in an attempt to identify a pacing mode that preserves atrio-ventricular synchrony, normal atrio-ventricular timing, prevents bradycardia and also prevents right ventricular stimulation. Caution should be taken to not directly apply these results to patients with either an indication for pacemaker therapy or to patients with an indication for cardiac resynchronization therapy since patients from neither population were included. However, considering the large magnitude of the deleterious effects associated with dual chamber pacing in the DAVID trial future studies should explore the possibility that left ventricular stimulation may be the only pacing mode capable of preventing bradycardia without increasing death and congestive heart failure.*3

Abstract

We compared 2 studies of implantable cardiac defibrillators (ICDs) to determine the effects of device mode on outcomes. The Antiarrhythmics Versus Implantable Defibrillators (AVID) trial (1993 to 1997) demonstrated improved survival with the ICD compared with antiarrhythmic drug therapy. The Dual-chamber And VVI Implantable Defibrillator (DAVID) trial (2000 to 2002) showed that VVI pacing at 40 beats/min in patients with ICDs reduced the combined end point of death and hospitalization for congestive heart failure compared with DDDR pacing at 70 beats/min. Patients in the AVID trial (631 of 1,016) and the DAVID trial (221 of 506) meeting common inclusion and all exclusion criteria were studied. The major end points were the time to death, and the composite end point of time to death or hospitalization for congestive heart failure. Patients in the AVID and DAVID trials were similar, but more AVID patients had coronary artery disease (p = 0.04), history of myocardial infarction (p = 0.005), and previous ventricular arrhythmias (p = 0.03). DAVID patients underwent more previous revascularization procedures (coronary artery bypass surgery, p = 0.03; percutaneous coronary intervention, p = 0.001), and were more often taking beta-blocking drugs at hospital discharge (p <0.001). The backup VVI ICD groups in both studies had similar outcomes (p = 0.4), even when corrected for the previous demographic differences. The time-to- composite end point was similar in AVID patients treated with antiarrhythmic drugs and DAVID patients treated with DDDR ICDs (p = 0.6). Despite improved pharmacologic therapy and revascularization, outcomes have not improved with backup VVI pacing ICDs. If DDDR ICDs had been used in the AVID trial, benefit from ICDs for patients with serious ventricular arrhythmias could have been missed.*4

Abstract

Context: Implantable cardioverter defibrillator (ICD) therapy with backup ventricular pacing increases survival in patients with life-threatening ventricular arrhythmias. Most currently implanted ICD devices provide dual-chamber pacing therapy. The most common comorbid cause for mortality in this population is congestive heart failure.

Objective: To determine the efficacy of dual-chamber pacing compared with backup ventricular pacing in patients with standard indications for ICD implantation but without indications for antibradycardia pacing.

Design: The Dual Chamber and VVI Implantable Defibrillator (DAVID) Trial, a single-blind, parallel-group, randomized clinical trial.

Setting and participants: A total of 506 patients with indications for ICD therapy were enrolled between October 2000 and September 2002 at 37 US centers. All patients had a left ventricular ejection fraction (LVEF) of 40% or less, no indication for antibradycardia pacemaker therapy, and no persistent atrial arrhythmias.

Interventions: All patients had an ICD with dual-chamber, rate-responsive pacing capability implanted. Patients were randomly assigned to have the ICDs programmed to ventricular backup pacing at 40/min (VVI-40; n = 256) or dual-chamber rate-responsive pacing at 70/min (DDDR-70; n = 250). Maximal tolerated medical therapy for left ventricular dysfunction, including angiotensin-converting enzyme inhibitors and beta-blockers, was prescribed to all patients.

Main outcome measure: Composite end point of time to death or first hospitalization for congestive heart failure.

Results: One-year survival free of the composite end point was 83.9% for patients treated with VVI-40 compared with 73.3% for patients treated with DDDR-70 (relative hazard, 1.61; 95% confidence interval [CI], 1.06-2.44). The components of the composite end point, mortality of 6.5% for VVI-40 vs 10.1% for DDDR-70 (relative hazard, 1.61; 95% CI, 0.84-3.09) and hospitalization for congestive heart failure of 13.3% for VVI-40 vs 22.6% for DDDR-70 (relative hazard, 1.54; 95% CI, 0.97-2.46), also trended in favor of VVI-40 programming.

Conclusion: For patients with standard indications for ICD therapy, no indication for cardiac pacing, and an LVEF of 40% or less, dual-chamber pacing offers no clinical advantage over ventricular backup pacing and may be detrimental by increasing the combined end point of death or hospitalization for heart failure.*5

*1New indications for cardiac pacing

[Article in French]

J M Davy et al. Arch Mal Coeur Vaiss. 1995 Dec

*2Dual-chamber implantable automatic defibrillators. Experiences apropos of 16 cases]

[Article in French]

P Le Franc et al. Arch Mal Coeur Vaiss. 1998 Jun.

*3The Dual Chamber and VVI Implantable Defibrillator (DAVID) Trial: rationale, design, results, clinical implications and lessons for future trials

Bruce L Wilkoff et al. Card Electrophysiol Rev. 2003 Dec.

*4A comparison of the AVID and DAVID trials of implantable defibrillators.

Arjun Sharma et al. Am J Cardiol. 2005.

*5Dual-chamber pacing or ventricular backup pacing in patients with an implantable defibrillator: the Dual Chamber and VVI Implantable Defibrillator (DAVID) Trial

Bruce L Wilkoff et al. JAMA. 2002.