Dual Chamber Rate Responsive Pacing Research Articles

Relation of Ventricular Tachycardia/Fibrillation to Beta-Blocker Dose Maximization Guided by Pacing Mode Analysis in Nonpacemaker-Dependent Patients With Implantable Cardioverter–Defibrillator

We hypothesized that uptitration of β blockade and adjustment of pacing parameters to achieve a prevalence of single chamber atrial inhibited rate-responsive (AAIR) pacing in patients with dual-chamber implantable cardioverter--defibrillators (ICDs) would result in maximization of β-blocker dosage and thus decrease appropriate ICD therapies. We included patients with ischemic or dilated cardiomyopathy and implanted ICDs without contraindications to β blockers and atrioventricular conduction disturbances. Two 6-month periods were compared: clinically guided phase (pacing function set at back-up dual-chamber rate-responsive pacing mode at a lower rate of about 40 beats/min) and pacing-guided phase, during which β-blocker dosage was titrated with a target of achieving >90% AAIR pacing (lower rate 60 beats/min). Sixty-one patients (64.2 ± 8.3 years old) were included. During the pacing-guided phase the target of ≥90% AAIR pacing was achieved in 80.3% of patients. Mean metoprolol dose during the clinically guided phase was 96.7 ± 29.4 versus 127.0 ± 39.6 mg/day in the pacing-guided phase (p <0.001). Appropriate ICD therapies were recorded in 35 patients (57.4%) during the clinically guided phase versus 20 (32.8%) during the pacing-guided phase (p <0.001; 1.15 and 0.48 appropriate ICD therapies per patient, respectively, p <0.001). In multivariate analysis, AAIR pacing and β-blocker dose were inversely related to appropriate ICD therapies. In conclusion, a pacing-guided approach for maximizing β-blocker doses guided by maximizing AAIR pacing in patients with ICDs may be beneficial compared to the conventional strategy. This pacing-guided approach led to higher daily β-blocker doses, which were correlated to fewer appropriate ICD therapies.

Use of Implantable cardioverter-defibrillators

The implantable cardioverter-defibrillator (ICD) is the most effective treatment for patients with life-threatening ventricular tachycardia or ventricular fibrillation not due to reversible causes. The American College of Cardiology/American Heart Association class I and IIa indications for an ICD are discussed. Patients with ICDs who need pacing should be treated with biventricular pacing, not with dual-chamber rate-responsive pacing, at a rate of 70/min. Patients with ICDs should be treated with β-blockers, statins and angiotensin-converting enzyme inhibitors or angiotensin receptor blockers.

Implantable Cardioverter-Defibrillators

The automatic implantable cardioverter-defibrillator (AICD) is the most effective treatment for patients with life-threatening ventricular tachycardia or ventricular fibrillation. The American College of Cardiology/American Heart Association class I, IIa, and III indications for an AICD are discussed. Patients with AICDs should be treated with biventricular pacing, not with dual-chamber rate-responsive pacing at a rate of 70/minute. Patients with AICDs should be treated with beta blockers, statins, and angiotensin-converting enzyme inhibitors or angiotensin receptor blockers.

The DAVID (Dual Chamber and VVI Implantable Defibrillator) II Trial

The purpose of this study was to determine whether atrial pacing is a safe alternative to minimal (backup-only) ventricular pacing in defibrillator recipients with impaired ventricular function. The DAVID (Dual Chamber and VVI Implantable Defibrillator) trial demonstrated that dual chamber rate responsive pacing as compared with ventricular backup-only pacing worsens the combined end point of mortality and heart failure hospitalization. Although altered ventricular activation from right ventricular pacing was presumed to be the likely cause for these maladaptive effects, this supposition is unproven. In all, 600 patients with impaired ventricular function from 29 North American sites, who required an implanted defibrillator for primary or secondary prevention, with no clinical indication for pacing, were randomly assigned to atrial pacing (at 70 beats/min) versus minimal ventricular pacing (at 40 beats/min) and followed up for a mean of 2.7 years. There were no significant differences between pacing arms in patients' baseline characteristics, use of heart failure medications, and combined primary end point of time to death or heart failure hospitalization during follow-up, with an overall incidence of 11.1%, 16.9%, and 24.6% at 1, 2, and 3 years, respectively. Similarly, the incidence of atrial fibrillation, syncope, appropriate or inappropriate shocks, and quality of life measures did not significantly differ between treatment groups. The effect of atrial pacing on event-free survival and quality of life was not substantially worse than, and was likely equivalent to, backup-only ventricular pacing. Atrial pacing may be considered a "safe alternative" when pacing is desired in defibrillator recipients, but affords no clear advantage or disadvantage over a ventricular pacing mode that minimizes pacing altogether. (Dual Chamber and VVI Implantable Defibrillator [DAVID] Trial II; NCT00187187).

Left Ventricular Ejection Fraction and Prevalence of New Left Ventricular Wall Motion Abnormality at Long-Term Follow-Up in Patients With Automatic Implantable Cardioverter-Defibrillators Treated With Dual-Chamber Rate-Responsive Pacing at a Rate of 70/minute Versus Backup Ventricular Pacing at a Rate of 40/minute

Baseline and long-term follow-up 2-dimensional echocardiograms were obtained in 160 patients with automatic implantable cardioverter-defibrillators without indications for antibradycardia pacing, who had backup ventricular pacing at a rate of 40/minute (VVI-40) or dual-chamber rate-responsive pacing at a rate of 70/minute (DDDR-70). At 37 months of follow-up for 80 patients treated with VVI-40 and 23 months of follow-up for 80 patients treated with DDDR-70, the mean left ventricular ejection fraction was 36 +/- 8% at baseline and 36 +/- 8% at follow-up and 36 +/- 7% at baseline and 30 +/- 7% at follow-up (p <0.01), respectively. At follow-up, the left ventricular ejection fraction was decreased >7% in 25 of 80 patients (31%)treated with DDDR-70 and in 9 of 80 patients (11%) treated with VVI-40 (p <0.01). A new left ventricular wall motion abnormality developed in 23 of 80 patients (29%) treated with DDDR-70 and in 11 of 80 patients (14%) treated with VVI-40 (p <0.025).

Patients, Mean Age 70 Years, With Automatic Implantable Cardioverter-Defibrillators Treated With Dual-Chamber Rate Responsive Pacing (DDDR-70) Have a Higher Mortality Than Patients With Backup Ventricular Pacing (VVI-40) at 3.7-Year Follow-Up

One study showed in 506 patients with automatic implantable cardioverter-defibrillators (AICDs) that the mortality at 1-year follow-up was 6.5% with ventricular backup pacing at 40/minute (VVI-40) versus 10.1% in patients with dual-chamber rate responsive pacing at 70/minute (DDDR-70). We performed a retrospective study to determine all-cause mortality in all patients at a university hospital who had AICDs without indications for antibradycardia pacing. Of 535 patients, mean age 70 +/- 12 years, 271 patients had backup ventricular pacing with a VVI-40, and 264 patients had dual-chamber rate responsive pacing with a DDDR-70. At 3.7-year mean follow-up, all-cause mortality was 19% (50 of 264 patients) in patients with DDDR-70 pacing versus 11% (29 of 271 patients) with VVI-40 pacing (p < .01). Because of the increased mortality, increased cost, and complexity for dual-chamber rate responsive pacing in patients with AICDs, concomitant DDDR pacing at a rate of 70/minute in patients without an indication for antibradycardia pacing is not warranted.

Right ventricle pacing site selection in children

Purpose of study to evaluate the advantage of the interventricular right ventricle (RV) pacing on the RV apex pacing in children with permanent pacemakers. Methods used 112 children (59 males (52.6%)) at the age of 15 to 192 month (mean age 99.6 ± 68.6 month) underwent the pacemaker implantation from 2001 to 2004. 58 children (51.8%) have a postoperative atrio-ventricular block, 54 children (48.2%) have a congenital atrio-ventricular block. 48 patients (42.8%) were paced in VVI mode. 23 patients (20.5%) were paced in VVIR mode. 41 (36.6%) were paced in dual–chamber rate-responsive pacing mode. In 42 patients (37.5%) the ventricle lead was posizioned in right ventricle and screwed in the upper or middle part of the interventricular septum. In the rest of patients (70(62.5%)) ventricular lead was implanted in the RV apex. Results QRS duration was significantly shorter (p>0.05) in patient with interventricular septum pacing system (0.89+0.03 mc) vs. RV apex pacing system (0.14+0.04 mc). There was no paradoxal motion of the interventricular septum. Futhermore in these patients was no signs of the congestive heart failure in long follow-up period. The engection fraction was significantly high (55,8 +10,8 % vs. 34,17+5,3 %) in this group of patients. Conclusion The upper part of the interventricular septum is apreferable site for the permanent right ventricular pacing in children.

Technologic advances in implantable cardioverter defibrillators.

Multiple technologic advances in the implantable cardioverter defibrillator (ICD) have resulted in smaller size, easier implantation, and improved detection, therapy, and stored diagnostic information. Advanced dual-chamber ICDs are currently available that allow dual-chamber rate-responsive pacing with mode switching, enhanced detection algorithms, antitachycardia pacing, low-energy cardioversion, high-energy shocks, and extensive diagnostics. Based on improvements in lead systems and improved energy waveforms, almost all devices are being implanted with nonthoracotomy leads in the pectoralis area. The results of recent clinical trials have expanded indications for the ICD for primary and secondary prevention of sudden cardiac death. With advances in capacitor and battery technology coupled with improved lead systems and waveform resulting in lower defibrillation thresholds, it is likely that lower-output, smaller devices will be developed. In the future, ICDs may have expanded indications and may incorporate physiologic sensors to access hemodynamic significance of arrhythmias and algorithms for prediction and prevention of cardiac arrhythmias.

Paroxysmal atrial fibrillation and high degree AV block: use of single-lead VDDR pacing with mode switching.

Dual chamber rate responsive pacing incorporating a mode switching option is increasingly used in patients with chronic paroxysmal atrial fibrillation and high degree AV block. Single-lead VDDR pacemakers have rarely used for this indication. The purpose of this study was to determine their reliability of atrial sensing during atrial fibrillation, the percentage of atrial synchronous ventricular pacing, and the behavior of the sinus rate outside the phases of atrial fibrillation. We studied ten patients with a single-lead VDDR pacemaker implanted for this indication. Follow-up visits were performed at predischarge and after 1, 3, 6, 12, 18, and 24 months. During the mean follow-up period of 18.9 +/- 6.9 months, the atrial sensing thresholds in sinus rhythm remained stable. Atrial synchronous ventricular stimulation was achieved in 68.7 +/- 31.2% (median 82.5%) of the whole follow-up time. All patients showed an adequate atrial rate response during sinus rhythm. Atrial fibrillation was detected by the pacemakers in 24.0 +/- 29.8% of time. In 3 of 10 patients the duration of atrial fibrillation showed a steady increase from visit to visit. The sensed amplitudes of atrial fibrillation ranged from 0.1-1.0 mV. A programmed atrial sensitivity of 0.1 mV was necessary to achieve complete sensing of atrial fibrillation. None of the patients experienced tachycardias with optimized pacemaker programming. Single-lead VDDR pacing incorporating a mode-switching option is useful in patients with high degree AV block and paroxysmal atrial fibrillation, since it provides atrial synchronous ventricular pacing in more than two-thirds of follow-up time. In a subgroup of patients, a progressive increase of the time during atrial fibrillation was demonstrated. A reliable detection of paroxysmal atrial fibrillation requires the programming of the atrial sensitivity to its most sensitive value.

Dual chamber rate responsive pacing to allow sotalol therapy for ventricular tachycardia.

In order to allow the use of sotalol to control ventricular tachycardia (VT), dual chamber rate responsive (DDDR) pacemakers were implanted in ten patients aged 6 to 73 years (mean 50 years). Nine presented with monomorphic VT (seven inducible at baseline electrophysiological study [EPS]) and one with syncope (monomorphic VT at EPS). On sotalol, VT was initiated in only one. This patient received sotalol in the absence of an effective alternative agent. The mean dose was 468 +/- 269 mg/day. Indications for pacing were symptomatic sotalol induced bradycardia (7), sinus node dysfunction (1), postoperative complete heart block (1), and infra-His block at baseline EPS (1). At least five of these patients would have been candidates for an implantable cardioverter defibrillator had sotalol required discontinuation. Initially, nine patients were paced in DDDR mode and one, with normal AV conduction on sotalol, in AAIR. One patient was unable to tolerate sotalol despite pacing. One patient died suddenly after 35 months of symptom-free follow-up. There was a significant improvement in symptomatic status (P = 0.03) after pacing among the other eight patients with no recurrence of VT. The implantation of a DDDR pacemaker may be indicated in selected patients with serious cardiac arrhythmias. With such a device programmed to an appropriate mode, sotalol can be used successfully where otherwise contraindicated by bradycardia or preexisting conduction disease. For some patients this may obviate the expense, inconvenience, and attendant risks of implantable cardioverter defibrillator implantation.

Pacing in Atrial Arrhythmias

The history of pacing to control the atrial arrhythmias of sinoatrial node disease (SND) is reviewed and is demonstrated to have become more physiological in recent years. The importance of atrial stimulation is emphasized especially in the context of the natural history of SND. The role of single and dual chamber rate responsive pacing for correction of chronotropic incompetence is outlined and guidelines are proposed for the management of the different types of SND presentation.

Physiological Benefits of a Pacemaker with Dual Chamber Pacing at Low Heart Rates and Single Chamber Rate Responsive Pacing During Exercise

Dual chamber rate responsive pacing may be an ideal mode but may result in high current drain and premature battery depletion. To minimize battery drain during exercise, this study compared a combination pacing mode of DDD and ventricular rate responsive pacing (VVIR). Nine patients were studied who had complete heart block, sinus rhythm, DDD pacemakers, and a reduced mean left ventricular ejection fraction of 44%. Patients were exercised in DDD, VVIR, and a combination of DDD at low heart rates and VVIR at mean heart rates over 89 bpm. Blood pressure, heart rate, exercise duration, work rate, oxygen uptake, anaerobic threshold, and oxygen pulse were measured. There was no difference in symptoms or in mean cardiopulmonary function indices including exercise duration 10.7, 10.3, 10.3 minutes; heart rate 127, 133, 136 bpm; oxygen uptake 1.4, 1.5, 1.5 L/minute; or anaerobic threshold 5.6, 5.5, 5.7 minutes (p greater than 0.05) in any mode. A pacemaker that provides atrioventricular synchrony at low heart rates with ventricular rate responsiveness at high heart rates may be an alternative mode for some patients.

Rate-responsive pacing: clinical experience.

Single chamber, rate-responsive pacing is emerging as a new modality in cardiac pacing and in the near future, dual chamber rate-responsive pacing may be the optimal solution for most pacemaker patients. In this report we describe our short- and long-term clinical experience with two different rate-responsive pacemakers: the RS4, an asynchronous atrial sensing ventricular pacemaker, and the TX-pacemaker, which senses the evoked QT after a ventricular paced beat, as an indicator of metabolic demand. Both systems use a single ventricular lead. Nine patients received RS4 and 10 patients received TX units. All of these patients had AV block and good ventricular function except for three patients with sinus node disease in the TX group. Between 1 and 3 months after implantation, a 24-hour Holter monitoring was performed, during which two maximal symptom-limited treadmill exercise tests (Bruce protocol) were conducted in VVI (70 bpm) and rate-responsive modes, in a random fashion. The mean follow-up was 25 months in RS4 group and 10 months in TX group. Significant improvements in patient exercise tolerance were found in the rate-responsive mode (9.0 vs. 6.6 METs in VVI) with similar results in both groups (RS4 and TX) despite higher ventricular pacing rates in the TX group (121 bpm vs. 102 bpm in RS4). An autolimited rate-responsive pacemaker-mediated tachycardia, induced by retrograde ventriculo-atrial conduction, was observed in a patient with an RS4.(ABSTRACT TRUNCATED AT 250 WORDS)