Minimizing right ventricular pacing

Sinus Node Dysfunction

Sinus node dysfunction (SND) is a multifaceted disorder most prevalent in older individuals, but may also occur at an earlier age. In most cases, the SND diagnosis is ultimately established by documenting its ECG manifestations. EPS has limited utility. The treatment strategy is largely dictated by symptoms and ECG manifestations. Not infrequently, both bradycardia and tachycardia coexist in the same patients, along with other diseases common in the elderly (e.g., hypertension, coronary artery disease), thereby complicating treatment strategy. Prevention of the adverse consequences of both bradyarrhythmia and tachyarrhythmia is important to reduce susceptibility to syncope, falls, and thromboembolic complications.

Sinus Node Dysfunction

Sinus node dysfunction (SND) is a multifaceted disorder most prevalent in older individuals, but may also occur at an earlier age. In most cases, the SND diagnosis is ultimately established by documenting its ECG manifestations. EPS has limited utility. The treatment strategy is largely dictated by symptoms and ECG manifestations. Not infrequently, both bradycardia and tachycardia coexist in the same patients, along with other diseases common in the elderly (e.g., hypertension, coronary artery disease), thereby complicating treatment strategy. Prevention of the adverse consequences of both bradyarrhythmia and tachyarrhythmia is important to reduce susceptibility to syncope, falls, and thromboembolic complications.

Long-term mortality outcomes according to the frequency of right ventricular pacing in veterans

Background. Right ventricular pacing (RVP) has been associated with adverse outcomes, including heart failure and death. Minimizing RVP has been proposed as a therapeutic goal for a variety of pacing devices and indications. Objective. Quantify survival according to frequency of RVP in veterans with pacemakers. Methods. We analyzed electrograms from transtelephonic monitoring of veterans implanted with pacemakers between 1995 and 2005 followed by the Eastern Pacemaker Surveillance Center. We compared all cause mortality and time to death between patients with less than 20% and more than 80% RVP. Results. Analysis was limited to the 7198 patients with at least six trans-telephonic monitoring records (mean = 21). Average follow-up was 5.3 years. Average age at pacemaker implant was significantly lower among veterans with <20% RVP (67 years versus 72 years; P < .0001). An equal proportion of deaths during follow-up were noted for each group: 126/565 patients (22%) with <20% RVP and 1113/4968 patients (22%) with >80% RVP. However, average post-implant survival was 4.3 years with <20% RVP versus 4.7 years with >80% RVP (P < .0001). Conclusions. Greater frequency (>80%) of RVP was not associated with higher mortality in this population of veterans. Those veterans utilizing <20% RVP had a shortened adjusted survival rate (P = .0016).

Simulation of AV hysteresis pacing using an integrated dual chamber heart and pacer model

Long term right ventricular apical pacing has been known to have adverse effects in cardiac function. The AV hysteresis (AVH) is a feature existing in many dual-chamber cardiac pacemakers that aims to minimize the right ventricular pacing, but its clinical efficacy remains inconclusive due to conflicting evidence from different studies. We have recently developed a novel integrated dual-chamber heart and pacer (IDHP) model, which can simulate various interactions between intrinsic heart activity and extrinsic cardiac pacing. In this study, we use the IDHP model to simulate various atrio-ventricular (AV) conduction pathologies, and to investigate the effects of an AVH algorithm on reducing right ventricular pacing. Our results show that the efficacy of AVH is dependent on the underlying cardiac conditions. While it can preserve intrinsic conduction during minor or moderate first degree AV block, its efficacy is reduced at higher degree AV block conditions. This pilot study further supports using the IDHP model to design and evaluate more advanced pacemaker algorithms for therapeutic interventions.

Pacemaker-induced mitral regurgitation as a cause of refractory congestive heart failure during pacing therapy in a patient with hypertrophic obstructive cardiomyopathy

This report describes a woman with hypertrophic obstructive cardiomyopathy in whom initial hemodynamic improvement by dual chamber (DDD) pacing with short atrioventricular delay was excellent, but severe mitral regurgitation developed during the subsequent follow-up period, resulting in refractory congestive heart failure. There were two possible explanations for the origin of the complicating mitral regurgitation in this patient: pacing-induced semiclosure of the mitral valve, or left ventricular asynchrony caused by right ventricular pacing. Heart failure in patients with hypertrophic obstructive cardiomyopathy who undergo placement of a DDD pacemaker to improve not only mitral regurgitation but also heart failure symptoms can be associated with systolic mitral regurgitation as the cause of failure in DDD pacing therapy.

Selective site ventricular pacing

PURPOSE OF REVIEW

The traditional site for ventricular pacing, the right ventricular apex, produces an abnormal pattern of ventricular depolarization and there is growing evidence that pacing from this site is associated with adverse functional and structural changes in the left ventricle. This is manifest clinically as an increased morbidity and mortality. These observations have fuelled interest in pacing at sites alternative to the right ventricular apex. In this article, we review the evidence for selective site pacing, focusing mainly on the right ventricular outflow tract.

RECENT FINDINGS

Data are conflicting on the acute and medium-term effects of right ventricular outflow tract pacing. Although a recent meta-analysis has suggested acute benefit from pacing at this site, the data are confounded by poor definition of the outflow tract and the non-randomized nature of most trials. There is a need for standardization of nomenclature and better definition of non-apical sites. Long-term data on chronic pacing are limited, with two studies showing equivalency between apical and outflow tract pacing. In another two studies, right ventricular outflow tract pacing was associated with improved ejection fraction.

SUMMARY

Selective site pacing holds promise in attempting to reduce the problems associated with chronic ventricular pacing. Large, prospective, randomized control trials are needed.