Multisite Pacing Research Articles

Pace prevention of atrial fibrillation: what can we expect from new algorithms?

Since the observation that antibradycardia pacing may prevent vagal-mediated parosysmal atrial fibrillation, several approaches have been undertaken to establish pace-prevention of atrial fibrillation as a therapeutic option in such patients. Multisite pacing strategies like biatrial, bifocal right atrial or septal pacing are in first line so-called substrate-modulators of atrial fibrillation that try to compensate for inter- and intraatrial conduction disturbances. Preventive pacing algorithms, which can be used with a conventional atrial lead position, are designed to suppress premature atrial contractions and salvos as a known trigger of atrial fibrillation. Pace conditioning: This algorithm adjusts the rate just above the intrinsic sinus rate with the aim to overdrive and pace the atrium for at least 95% of the time. Premature atrial contraction suppression: When a spontaneous atrial event is classified as a premature atrial contraction, the pacing rate is increased to 15 min-1 above the physiological rate and kept stable for a certain period. Post-premature atrial contraction response: This algorithm is designed to prevent arrhythmogenic pauses after premature atrial contractions by controlling the atrial rate only in the two beats after each premature atrial contraction. Post-exercise response: The post-exercise pacing rate is adjusted to both the level and the duration of exercise in order to prevent too step of a rate drop at the onset of the recovery phase. These four preventive pacing algorithms are currently investigated in the AFtherapy study. The results of this and other prospective pacing studies will not only clarify the relevance and effectiveness of pacing for prevention of atrial fibrillation but will also enlarge our knowledge about the induction mechanisms of atrial fibrillation in patients.

Multisite atrial pacing: an option for atrial fibrillation prevention? preliminary results of the Dutch dual-site right atrial pacing for prevention of atrial fibrillation study

Multisite pacing is a novel concept for the prevention of recurrent drug-refractory atrial fibrillation (AF). Two different pacing methods have been described, biatrial pacing and dual-site right atrial stimulation. The use of multisite pacing as preventive therapy for recurrences of atrial fibrillation is still under investigation. We conducted a prospective, randomized, crossover study in patients with recurrent drug-refractory AF without or with minimal structural heart disease. After implantation of a DDD pacemaker, patients were randomized to either dual-site pacing first (Group I) or single-site (high right atrium) pacing first (Group II) and, after 6 months of treatment, the device was reprogrammed to the other pacing mode. Preliminary results of 13 patients in each group are presented. Clinical characteristics of patients in both groups with respect to age, sex, left atrial dimension, left ventricular function, and New York Heart Association (NYHA) functional class were comparable. Pacing therapy was combined with antiarrhythmic drug treatment. After completion of the study protocol, the arrhythmia-free interval was not remarkably different in either group. However, the endpoint free interval (i.e., the need for electrical cardioversion because of recurrent AF lasting >24 hours, was less during dual-site pacing in Group II. Within 6 months, 43 patients enrolled in this study will have completed the protocol.

Echocardiographic evidence of hemodynamic and clinical improvement in patients paced for heart failure

Dilated cardiomyopathy is frequently associated with electrical conduction disturbances. Development of left bundle-branch block with discoordinated ventricular contraction pattern further contributes to impaired hemodynamic performance. Biventricular pacing has evolved as a new treatment option for patients with dilated cardiomyopathy and conduction disturbances. The “electrical” approach aims to normalize the disturbed contraction pattern, thereby improving hemodynamic function by simultaneous stimulation at different ventricular sites. Acute hemodynamic improvement with biventricular pacing has been demonstrated in patients with depressed left ventricular function and delayed intraventricular conduction. Due to the variations in optimal pacing site and atrioventricular delay, individual optimization to achieve optimal hemodynamic benefit is necessary. Echocardiography has the potential to provide hemodynamic data by Doppler techniques and combine these with geometric information about ventricular volumes, ejection fraction, and contraction patterns. This article focuses on the use of echocardiographic techniques for noninvasive optimization in cardiac pacing and presents preliminary experience from the initial trials on multisite pacing in heart failure.

Long-term effects of biatrial synchronous pacing to prevent drug-refractory atrial tachyarrhythmia: a nine-year experience.

Results of previous studies suggest that atrial resynchronization by multisite atrial pacing may contribute to prevention of recurrences in patients with drug-refractory atrial tachyarrhythmias and significant intra-atrial conduction delay. To verify this hypothesis, a prospective noncontrolled study of 86 patients (mean age 66 +/- 10 years) was conducted in a single center between January 1989 and February 1998. Inclusion criteria were P wave duration > or = 120 msec with interatrial conduction time > or = 100 msec, and history of multiple recurrences of atrial tachyarrhythmias (mean 7 +/- 4.8 episodes) evolving in a persistent mode for at least 6 months despite optimized drug treatment (mean 2.7 +/- 1.8 drugs/patient). Patients were chronically implanted with a pacing system that ensured permanent biatrial pacing using two atrial leads, one placed in the high right atrium and the other one into the mid or the distal part of the coronary sinus. P wave duration decreased from a mean value of 187 +/- 29 msec before implant to 106 +/- 14 msec (P < 0.0001) under biatrial pacing. After a 33-month mean follow-up (range 6 to 109), 55 patients (64%) remained in sinus rhythm, including 28 patients (32.6%) without any documented recurrence and 27 patients with one or more recurrences in a paroxysmal or in a persistent form. In these 55 patients, drug treatment was significantly reduced in relation to the preimplantation period (1.4 +/- 0.6 vs 1.7 +/- 0.5 drugs/patient; P = 0.011). The other 31 patients went into chronic atrial arrhythmia after a mean period of 26 months. The only predictive factor of positive response was a spontaneous P wave duration < 160 msec at baseline. The results are consistent with a preventive effect of permanent biatrial pacing on recurrent and drug-refractory atrial arrhythmias associated with intra-atrial conduction delay.

Should the split format in the third position of the pacemaker code be resurrected?

It is possible to characterize some of the sensing functions of new multisite pacing systems by resurrecting the split format in the third position of the standard pacemaker code. This approach permits accurate representation of the horizontal and vertical triggering functions of multisite dual-chamber pacemakers without creating a new code.

Multisite Pacing for Heart Failure: Is Improved Ventricular Coordination the Mechanism of Benefit?

Multisite Pacing for Heart Failure: Is Improved Ventricular Coordination the Mechanism of Benefit?

The acute effects of biatrial pacing on atrial depolarization and repolarization.

Permanent biatrial and/or multisite atrial pacing may prevent atrial fibrillation (AF), but the effects on atrial electrophysiology remain incompletely understood. Acute biatrial pacing was studied in 20 patients with and 28 without (controls) a history of atrial fibrillation and/or flutter. Twelve-lead electrocardiograms were recorded during pacing from the high right atrium (RA), from the distal coronary sinus (LA), and biatrial pacing. P wave duration was measured in each lead and the difference between maximum and minimum P duration was termed P wave dispersion. Effective refractory periods (ERPs) were measured during each pacing mode. The dispersion of P wave duration was 35 +/- 14 ms in controls and 40 +/- 29 ms in AF patients (P = 0.17). Compared to RA pacing, LA pacing shortened P duration in controls (127 +/- 18 to 107 +/- 16 ms, P < 0.05) and biatrial pacing markedly shortened P duration in controls (127 +/- 18 to 93 +/- 14 ms, P < 0.05) and AF patients (114 +/- 43 to 97 +/- 21 ms, P < 0.05). P wave dispersion was unaffected. In controls, the LA ERP was longer than the RA ERP. This phenomenon was not present in AF patients, whose LA ERP was shorter than that of controls. Biatrial pacing had no effect on atrial ERPs or the dispersion of atrial refractoriness. In conclusion, acute biatrial pacing does not affect atrial repolarization but it does cause a marked shortening of global biatrial depolarization. Distal coronary sinus pacing produces a shorter P wave than RA pacing. There is substantial dispersion in the surface P wave of the electrocardiogram, the significance of which awaits further study.

Mechanisms of left ventricular walls resynchronization during multisite ventricular pacing: Direct effects on the variations of the regional electromechanical delays and wall motion velocities

Mechanisms of left ventricular walls resynchronization during multisite ventricular pacing: Direct effects on the variations of the regional electromechanical delays and wall motion velocities

Hemodynamic assessment of multisite ventricular pacing by peak endocardial acceleration and echocardiography in patients with end‐stage heart failure

Hemodynamic assessment of multisite ventricular pacing by peak endocardial acceleration and echocardiography in patients with end‐stage heart failure

The Acute Effects of Transvenous Biventricular Pacing in a Patient With Congestive Heart Failure

The management of congestive heart failure remains an issue of great interest. Encouraging data emerged over the last 2 years supporting the use of multisite pacing in patients with severe congestive heart failure and intraventricular conduction delay. We present a case of acute biventricular pacing in a 81-year old man with dilated cardiomyopathy and symptomatic congestive heart failure. This novel form of pacemaker treatment resulted in a rapid hemodynamic and clinical improvement.

Multisite pacing for prevention of atrial tachyarrhythmias: potential mechanisms

OBJECTIVESTo determine the effects of single-, dual-, triple- and quadruple-site atrial pacing on atrial activation and refractoriness in normal canine hearts.BACKGROUNDMultisite pacing has been suggested to be superior to single-site pacing for prevention of atrial tachyarrhythmias. However, the underlying electrophysiological mechanisms are undetermined at the moment, as is the rationale for the selection of pacing locations and the number of pacing sites.METHODSIn 13 normal beagle dogs, an epicardial multielectrode (128 bipoles) and a multiplexer mapping system were used to reconstruct epicardial atrial activation patterns obtained during simultaneous stimulation from up to four electrodes located in the high and low right and left atrium, respectively. For all pacing modes (single-, dual-, triple- and quadruple-site pacing), total activation times and local effective refractory periods at eight randomly selected sites as well as local recovery intervals were determined. In a subgroup of five dogs, total epicardial activation times were also obtained during single-site septal stimulation (septal group).RESULTSActivation times and local recovery intervals were minimized by triple-site stimulation, whereas a fourth site did not produce further shortening. Septal stimulation produced epicardial activation times comparable to quadruple-site stimulation. Local refractory periods and their dispersion always remained unaffected. Functional conduction blocks apparent during single-site were found to resolve during multisite stimulation.CONCLUSIONSMultisite pacing can prevent functional conduction blocks by multidirectional excitation and a reduction in total activation time. Triple-site and, possibly, septal pacing modes are expected to be most efficient because both minimize total activation times and maximize the multidirectionality of excitation. In spite of unaffected local refractory periods, the shortening of local recovery intervals might homogenize atrial repolarization and, thus, contribute to the preventive effects of multisite pacing.

Experimental study of the effects of multi-site sequential ventricular pacing on the prophylaxis of ventricular fibrillation.

Previous studies report a significant prophylactic effect on the occurrence of atrial fibrillation by simultaneous multi-site atrial pacing. We investigated the effects of multi-site sequential ventricular pacing (MSVP), which may be preferable to simultaneous multi-site pacing in terms of the prophylaxis of the occurrence of ventricular fibrillation (VF). Needle electrodes were inserted at ten different epicardial sites on both ventricles for MSVP in 12 adult beagle dogs. Four premature ventricular extrastimuli (PVE) were introduced to provoke VF reproducibly from a separate electrode in the left ventricle. The 4 PVE were applied to try to provoke VF during MSVP in a comparable fashion to the activation sequence during sinus rhythm. We compared the prophylactic effects of MSVP on the inducibility of VF by changing the number of stimulation sites to either 1, 3, 5, or 10 epicardial sites. We performed a total of 363 trials of induction and suppression of VF. The occurrence rates of VF by the 4 PVE for the various number of epicardial stimulation sites of MSVP, i.e., at 1, 3, 5, and 10 sites, were 0.8263, 0.4286, 0.4450, and 0.2857, respectively (p < 0.05). There was a significant prophylactic effect of MSVP on the inducibility of VF, and this effect became stronger as the number of MSVP sites was increased from 3 to 10. The hemodynamic state was relatively stable during MSVP. MSVP seems to be a promising method with which to reduce the occurrence of VF, and a larger number of stimulation sites would be more effective in terms of the prophylaxis of VF.

Electrophysiologic assessment in selecting patients for multisite atrial pacing.

Electrophysiologic mechanisms of atrial fibrillation (AF) initiation are being actively studied. Multisite atrial pacing has shown, in acute studies, significant potential for prevention of AF. Dual site pacing reduces of intra and inter-atrial conduction time, atrial refractoriness dispersion, and to a limited extent atrial premature beats which modify the atrial remodelling induced by AF. Recently, two clinical trials have shown long term efficacy of multisite atrial pacing. At 3 years of follow-up, 56% of patients are free of AF recurrence with dual site right atrial pacing. Rhythm control was achieved in 86 of patients. Similar results are observed with biatrial resynchronization. In both studies, primary indication for multisite atrial pacing was AF prevention in more than 50% of patients. Selection of patients based solely on long P wave duration and prolonged interatrial conduction is not necessary as clinical outcome and comparable. These patients are comparable to patients who did not have these characteristics. Ongoing multicenter trials will likely definitively answer this question. However, preexcitation of diseased atrial regions or site of ectopic activity previously selected by high density atrial mapping or suppression of inducible AF may offer an interesting future development of multisite atrial pacing.

Atrial fibrillation after cardiac operation: risks, mechanisms, and treatment

Atrial fibrillation (AF) is a common complication of cardiac operations that leads to increased risk for thromboembolism and excessive health care resource utilization. Advanced age, previous AF, and valvular heart operations are the most consistently identified risk factors for this arrhythmia. Dispersion of repolarization leading to reentry is believed to be the mechanism of postoperative AF, but many questions regarding the pathophysiology of AF remain unanswered. Treatment is aimed at controlling heart rate, preventing thromboembolic events, and conversion to sinus rhythm. Multiple investigations have examined methods of preventing postoperative AF, but the only firm conclusions that can be drawn is to avoid β-blocker withdrawal after operation and to consider β-blocker therapy for other patients who may tolerate these drugs. Preliminary investigations showing sotalol and amiodarone to be effective in preventing postoperative AF are encouraging, but early data have been limited to selective patient populations and have not adequately evaluated safety. Newer class III antiarrhythmic drugs under development may have a role in the treatment of postoperative AF, but the risk of drug-induced polymorphic ventricular tachycardia must be considered. Nonpharmacologic interventions under consideration for the treatment of AF in the nonsurgical setting, such as automatic atrial cardioversion devices and multisite atrial pacing, may eventually have a role for selected cardiac surgical patients.

Lessons learnt from multisite pacing for AF management-technical challenges.

Lessons learnt from multisite pacing for AF management-technical challenges.

Developing clinical indication for multisite pacing.

The artificial activation of the heart modifies the mechanics of contraction and relaxation. While only little basic research has been addressed to this question, clinical observations showed that for hypertrophic as well as dilated cardiomyopathies appropriate pacing techniques can be useful. Pacing can influence the activation sequence. The spread out from a single site is slow, and so hypercontractility deminshed. With the use of multiple electrodes, two atrial and/or two ventricular, conduction delays in the atria or ventricles can be eliminated. Synchronisation of the cardiac activation has an anti-arrhythmic and positiv inotropic effect. This may lead to new indications for pacemakers or better to be named cardiac synchronisers.

Electrocardiographic predictive factors of long-term clinical improvement with multisite biventricular pacing in advanced heart failure

Biventricular pacing has recently been proposed for treating patients with drug refractory heart failure and intraventricular conduction delay. The purpose is to restore ventricular relaxation and contraction sequences as homogeneously as possible. The aim of this study was to determine if some factors could predict the long-term clinical effectiveness of that new treatment. This study included 26 patients, aged 66 ± 7 years, with drug refractory heart failure and wide QRS. Patients were implanted with a biventricular pacemaker. The left ventricle was paced through a coronary sinus tributary. New York Heart Association functional class, exercise tolerance, and left ventricular (LV) ejection fraction were collected at baseline and after pacemaker implantation. Patients were divided into 2 groups: group I = responders; group II = nonresponders. QRS duration and axis at baseline and during biventricular pacing, interventricular conduction time, and LV and right ventricular lead positions were compared between the 2 groups. Group I patients (n = 19) had a mean reduction of 1.3 in functional class and an increase in peak oxygen consumption rate by a mean of 50%. The only parameter that differed between the 2 groups was the QRS duration during biventricular pacing, with a significantly shorter value in group I than in group II (154 ± 17 vs 177 ± 26 ms; p = 0.016). Thus, a positive response to biventricular pacing is correlated with the quality of electrical resynchronization. The optimal positions of the right and LV leads would be those that could induce the greatest shortening of QRS duration.

Hemodynamic effects of multisite ventricular pacing in dogs at short atrioventricular delay

The effects of VDD pacing on hemodynarnics can be best studied at a short atrioventricnlar (SAVD) since it avoids fusion with the intrinsic wave generated at the atrium. Although studies have been done to test right ventricular apex (RVA) pacing with short AV delay, little is known about pacing at different sites in the left ventricle (LV) with a normal conduction system. Our aim was to compare the hemodynarnic effects of different activation sequences with SAVD pacing in a normal conduction system.

Multisite or alternate site pacing for the prevention of atrial fibrillation

The role of permanent pacing in preventing atrial fibrillation in patients at risk for this arrhythmia is a relatively new concept. Existing retrospective studies support the superiority of atrial-based pacing over ventricular stimulation with respect to lowering the incidence of atrial fibrillation. Constant rate overdrive pacing has been shown to reverse abnormalities in conduction or refractoriness that are dependent on bradycardia and suppress atrial ectopic complexes. Multisite (biatrial and dual right atrial) pacing is a promising concept. The antiarrhythmic mechanism is not well understood, but atrial resynchronization and reduction of site-dependent conduction delay of atrial premature complexes may be relevant. The cardiology community awaits additional data from prospective trials that are currently underway.

Acute hemodynamic effects of biventricular DDD pacing in patients with end-stage heart failure.

The aim of this study was to assess the potential acute benefit of multisite cardiac pacing with optimized atrioventricular synchrony and simultaneous biventricular pacing in patients with drug-refractory congestive heart failure (CHF). Prognosis and quality of life in severe CHF are poor. Various nonpharmacological therapies have been evaluated but are restricted in their effectiveness and applications. In the early 1990s, dual chamber pacing (DDD) pacing was proposed as primary treatment of refractory CHF but results were controversial. Recently, tests to evaluate the effect of simultaneous pacing of both ventricles have elicited a significant improvement of cardiac performance. Acute hemodynamic study was conducted in 18 patients with severe CHF (New York Heart Association class III and IV) and major intraventricular conduction block (IVCB) (QRS duration = 170+/-37 ms). Using a Swan-Ganz catheter, pulmonary artery pressure, pulmonary capillary wedge pressure (PCWP) and cardiac index (CI) were measured in different pacing configurations: atrial pacing (AAI) mode, used as reference, single-site right ventricular DDD pacing and biventricular pacing with the right ventricular lead placed either at the apex or at the outflow tract. The CI was significantly increased by biventricular pacing in comparison with AAI or right ventricular (RV). DDD pacing (2.7+/-0.7 vs. 2+/-0.5 and 2.4+/-0.6 l/min/m2, p < 0.001). The PCWP also decreased significantly during biventricular pacing, compared with AAI (22+/-8 vs. 27+/-9 mm Hg; p < 0.001). This acute hemodynamic study demonstrated that biventricular DDD pacing may significantly improve cardiac performance in patients with IVCB and with severe heart failure, in comparison with intrinsic conduction and single-site RV DDD pacing.