Comparative assessment of right, left, and biventricular pacing in patients with permanent atrial fibrillation

Fusion beat in patients with heart failure treated with left ventricular pacing: may ECG morphology relate to mechanical synchrony? A pilot study

BACKGROUND

Electrical fusion between left ventricular pacing and spontaneous right ventricular activation is considered the key to resynchronisation in sinus rhythm patients treated with single-site left ventricular pacing.

AIM

Use of QRS morphology to optimize device programming in patients with heart failure (HF), sinus rhythm (SR), left bundle branch block (LBBB), treated with single-site left ventricular pacing.

METHODS AND RESULTS

We defined the "fusion band" (FB) as the range of AV intervals within which surface ECG showed an intermediate morphology between the native LBBB and the fully paced right bundle branch block patterns.Twenty-four patients were enrolled. Echo-derived parameters were collected in the FB and compared with the basal LBBB condition. Velocity time integral and ejection time did not improve significantly. Diastolic filling time, ejection fraction and myocardial performance index showed a statistically significant improvement in the FB. Interventricular delay and mitral regurgitation progressively and significantly decreased as AV delay shortened in the FB. The tissue Doppler asynchrony index (Ts-SD-12-ejection) showed a non significant decreasing trend in the FB. The indications provided by the tested parameters were mostly concordant in that part of the FB corresponding to the shortest AV intervals.

CONCLUSION

Using ECG criteria based on the FB may constitute an attractive option for a safe, simple and rapid optimization of resynchronization therapy in patients with HF, SR and LBBB.

Biventricular Upgrading in Patients with Conventional Pacing System and Congestive Heart Failure:Results and Response Predictors

BACKGROUND

There are few studies on cardiac resynchronization therapy (CRT) in heart failure (HF) patients with preexisting right ventricular (RV) pacing. The purpose of this study was to determine the efficacy of CRT upgrading in RV-paced patients and the predictivity of electromechanical dyssynchrony parameters (EDP) evaluated by standard echocardiography (ECHO) and tissue Doppler imaging (TDI).

METHODS

Thirty-eight consecutive patients with HF [New York Heart Association (NYHA) class III or IV, LVEF < 35%], prior continuous RV pacing, and absence of atrial fibrillation were enrolled in the presence of a paced QRS > or = 150 ms and evaluated by ECHO and TDI. A responder was defined as a patient with a favorable change in NYHA class and neither HF hospitalization nor death, plus an absolute increase of LVEF > or = 10 units.

RESULTS

At six-months follow-up, the whole study population had significant improvement in symptoms, systolic function, and QRS duration (P < 0.001); 32 (84%) patients had a favorable clinical outcome, 25 (66%) were considered responders according to the previous definition. Postimplant QRS was similarly reduced in both responders and nonresponders, whereas EDP had a significant improvement only in responders (P < 0.05). Using EDP, 23 (79%) patients were responders compared with 2 (22%) patients without mechanical dyssynchrony (P = 0.002).

CONCLUSIONS

In HF patients with previous RV pacing, CRT is effective to improve clinical, functional outcome, and LV performance and to reduce electromechanical dyssynchrony in a large proportion of patients. Dyssynchrony evaluated by standard and TDI ECHO can be useful for CRT selection of paced patients.

Early Detection of Regional Myocardial Dysfunction in Paced Children With Congenital Complete Atrioventricular Block

BACKGROUND

Right ventricular apical pacing leads to global left ventricular dysfunction. Assessment of regional myocardial function may allow for earlier detection of pacing-induced myocardial remodeling. The aim of this study was to evaluate regional myocardial function in paced children with congenital complete atrioventricular block (CCAVB).

METHODS

We investigated regional myocardial function using strain echocardiography and tissue velocity imaging in 10 paced children with CCAVB and in 14 age-matched healthy children. Echocardiograms of the paced children were obtained during intrinsic junctional rhythm.

RESULTS

All patients had normal biventricular size and global function. The time from R wave to peak regional strain rate and the time from R wave to peak regional myocardial tissue velocity were measured in nine segments. The differences between maximum and minimum values were used as a measure of contraction delay (dSR and dTV). Study group patients had significantly higher dSR and dTV values compared to the control group. Mean peak strain rates and peak tissue velocities obtained from same segments were significantly decreased in the study group compared to the control group. Regional dysfunction was more prominent in the areas of ventricular pacing. No significant correlation is found between the duration of pacing (2.5-18 years) and dSR, dTV, mean peak strain rates, or mean peak tissue velocities.

CONCLUSION

Pacing leads to regional myocardial dysfunction that can be detected with strain echocardiography and tissue velocity imaging during intrinsic junctional rhythm in children with CCAVB. Pacing-induced regional myocardial remodeling does not seem to progress with long-term right ventricular pacing in children with CCAVB.

Resynchronization therapy in the context of atrial fibrillation: Benefits and limitations

Atrial fibrillation (AF) and heart failure often coexist and are believed to directly predispose to each other. Cardiac resynchronization does not prevent or increase the induction of AF. However, new onset of AF does not seem to diminish the beneficial effects of CRT on symptoms, cardiac function and, more importantly, all-cause mortality if appropriate ventricular rate control by beta-blockers and digoxin is being achieved. While a pharmacological approach to control ventricular rate may be sufficient in most patients with paroxysmal AF or AF of shorter duration in those with permanent AF ablation strategies may be necessary. Observational studies and one randomized trial indicate a potential benefit of CRT in heart failure patients with chronic AF; particularly, biventricular pacing was superior compared to conventional right-univentricular stimulation. However, recent results suggest that even relatively high percentage biventricular capture may be inadequate, and that the benefits of CRT may only be extended to chronic AF patients with previous AV junctional ablation. Well designed and powered clinical trials are required before pacemaker dependency is created in large numbers of heart failure patients.

Atrioventricular junction ablation combined with either right ventricular pacing or cardiac resynchronization therapy for atrial fibrillation: The need for large-scale randomized trials

BACKGROUND

Nonrandomized studies suggest that atrioventricular (AV) junction ablation and pacemaker implantation may improve quality of life, ejection fraction, and exercise tolerance in patients with symptomatic drug-refractory atrial fibrillation.

OBJECTIVE

The purpose of this study was to determine whether recent randomized trials support the use of AV junction ablation in combination with conventional right ventricular pacemaker therapy or cardiac resynchronization therapy (CRT) in atrial fibrillation.

METHODS

Meta-analysis of randomized trials comparing AV junction ablation vs drugs or CRT vs right ventricular pacing for atrial fibrillation.

RESULTS

Six randomized trials with 323 patients compared AV junction ablation vs pharmacologic therapy. The majority of these trials did not individually report a statistically significant improvement in survival, stroke, hospitalization, functional class, atrial fibrillation-associated symptoms, left ventricular ejection fraction, exercise capacity, healthcare costs, or quality of life. Overall, all-cause mortality was 3.5% for AV junction ablation patients and 3.3% for controls (relative risk 1.18, 99% confidence interval 0.26-5.22). Three randomized trials with 347 patients compared CRT vs right ventricular pacing in atrial fibrillation. These trials did not individually report a statistically significant improvement in survival, stroke, hospitalization, exercise capacity, or healthcare costs. CRT was associated with a statistically significant improvement in ejection fraction in two of the three trials. Overall, CRT was associated with a trend toward reduced all-cause mortality relative to controls (relative risk 0.51, 99% confidence interval 0.22-1.16). All-cause mortality was 7.1% for CRT patients and 14% for controls.

CONCLUSION

Limited randomized trial data have been published regarding AV junction ablation in combination with conventional pacemaker therapy or CRT for atrial fibrillation. Large-scale randomized trials are needed to assess the efficacy of these therapies.

Right ventricular pacing can induce ventricular dyssynchrony in patients with atrial fibrillation after atrioventricular node ablation

OBJECTIVES

This study was designed to assess the effects of long-term right ventricular (RV) pacing on left ventricular (LV) dyssynchrony, LV function, and heart failure symptoms.

BACKGROUND

Atrioventricular (AV) node ablation and subsequent long-term RV pacing is a well-established treatment option in patients with atrial fibrillation (AF).

METHODS

In 55 patients with drug-refractory AF, AV node ablation and implantation of a pacemaker was performed. At baseline and after a mean of 3.8 +/- 1.7 years, LV dyssynchrony (by M-mode echocardiography and tissue Doppler imaging), LV function, and volumes and functional status were assessed.

RESULTS

After long-term RV pacing, 27 patients (49%) had developed LV dyssynchrony. Concomitantly, these patients worsened in heart failure symptoms (New York Heart Association functional class increased from 1.8 +/- 0.6 to 2.2 +/- 0.7, p < 0.05), with a decrease in LV ejection fraction (from 48 +/- 7% to 43 +/- 7%, p < 0.05) and an increase in LV end-diastolic volume (from 116 +/- 39 ml to 130 +/- 52 ml, p < 0.05). Conversely, patients without LV dyssynchrony did not deteriorate in heart failure symptoms, LV function, or LV volumes.

CONCLUSIONS

Long-term RV pacing can induce LV dyssynchrony in almost 50% of patients treated with AV node ablation for chronic AF. The development of LV dyssynchrony was associated with deterioration in heart failure symptoms, systolic LV function, and LV dilatation.

The deleterious consequences of right ventricular apical pacing: time to seek alternate site pacing

BACKGROUND

The purpose of this article is to critically review the data accumulated to date from studies evaluating the hemodynamic and clinical effects of right ventricular apical pacing during conventional permanent cardiac pacing. The data from studies comparing the effects of right ventricular apical pacing and alternate site ventricular pacing are also reviewed.

METHODS

We conducted a MEDLINE and journal search of English-language reports published in the last decade and searched relevant papers.

RESULTS

Although intraventricular conduction delay in the form of left bundle branch block (LBBB) has traditionally been viewed as an electrophysiologic abnormality, it has now become abundantly clear that it has profound hemodynamic effects due to ventricular dyssynchrony, especially in patients with heart failure. These deleterious effects can be significantly ameliorated by cardiac resynchronization therapy effected by biventricular or left ventricular pacing. However, not only is spontaneous LBBB harmful, but the iatrogenic variety produced by right ventricular apical pacing in patients with permanent pacemakers may be equally deleterious. In this review new evidence from recent studies is presented, which strongly suggests a harmful effect of our long-standing practice of producing an iatrogenic LBBB by conventional right ventricular apical pacing in patients receiving permanent pacemakers. This emerging strong new evidence about the adverse hemodynamic and clinical effects of right ventricular apical pacing would dictate a reassessment of our traditional approach to permanent cardiac pacing and direct our attention to alternate sites of pacing, such as the left ventricle and/or the right ventricular outflow tract or septum, if not for all patients, at least for those with left ventricular dysfunction. Indeed, current convincing data on alternate site ventricular pacing are encouraging and this approach should be actively pursued and further investigated in future studies.

CONCLUSIONS

Not only is spontaneous permanent LBBB harmful to our patients, but the iatrogenic variety produced by right ventricular apical pacing during conventional permanent pacing may also be deleterious to some patients. The compelling evidence presented herein cannot be ignored; it may dictate a change of attitude toward right ventricular apical pacing directing our attention to alternate sites of ventricular pacing and avoidance of the right ventricular apex.

Left bundle branch block as a risk factor for progression to heart failure

The prevalence of conduction disturbances, particularly left bundle branch block (LBBB), is strongly correlated with age and with the presence of cardiovascular disease. LBBB has been reported to affect approximately 25% of the heart failure (HF) population and it is likely that the deleterious role of such conduction disorders in the progression to HF has been underestimated. The purpose of this article is to review the data from the literature indicating that LBBB may have a causative role, mediated through the resulting intra-ventricular asynchrony, in the deterioration of cardiac function and the development of cardiac remodelling and HF. It also aims to address the potential for future clinical therapies for this conduction disorder.

Cardiac resynchronization therapy in patients with systolic left ventricular dysfunction and symptoms of mild heart failure secondary to ischemic or nonischemic cardiomyopathy

Cardiac resynchronization therapy (CRT) is beneficial in selected patients with moderate to severe heart failure (New York Heart Association [NYHA] classes III to IV). Patients with mildly symptomatic heart failure (NYHA class II) are currently not eligible for CRT and the potential beneficial effects in these patients have not been well studied. Fifty consecutive patients in NYHA class II heart failure and 50 consecutive patients in NYHA classes III to IV (control group) were prospectively included. All patients had left ventricular (LV) ejection fraction<or=35% and QRS duration>120 ms. The effects of CRT in NYHA class II patients were compared with the results obtained in both groups. The severity of baseline LV dyssynchrony (assessed with color-coded tissue Doppler imaging) was comparable between patients in NYHA class II versus those in NYHA classes III to IV (83+/-49 vs 96+/-51 ms, p=NS); resynchronization was achieved in all patients. NYHA class II patients showed a significant improvement in LV ejection fraction (from 25+/-7% to 33+/-10%, p<0.001) and reduction in LV end-systolic volume (from 168+/-55 to 132+/-51 ml, p<0.001) after CRT, similar to patients in NYHA classes III to IV. In addition, only 8% of NYHA class II patients had progression of heart failure symptoms. In conclusion, CRT had comparable effects in patients in NYHA class II and in NYHA classes III to IV heart failure in terms of LV resynchronization, improvement in LV ejection fraction, and LV reverse remodeling.

Cardiac resynchronisation therapy in heart failure: Current status

Cardiac resynchronization in heart failure already has a history of 12 years. However, the major advances have been the result of large multi center trials dating from 2001. In all these trials patients with a LVEF < or = 35% were included, and a QRS above 120 msec. Follow up was from 3-36 months. The majority of these trials showed a positive effect in reduction of composite and points of death or hospitalization for major cardiovascular events. Many of these trials also showed a diminution of left ventricular and systolic diameter or volume. Even in NYHA class II patients an improvement was seen. Some unanswered questions still remain as regards the agreement on electrical or electromechanical dyssynchrony criteria. There is a number of patients with "wide" QRS who do not improve and conversely a number of patients with a narrow QRS who witness improvement. The benefit in patients with atrial fibrillation also remains unanswered. Finally the value of this modality in patients with mild heart failure or asymptomatic left ventricular systolic dysfunction, NYHA class I-II remains to be determined in large on going trials. Another question is whether biventricular or left ventricular patient is preferable. Finally whether biventricular patient should be complemented by a defibrillator insertion is being currently studied. Cardiac resynchronization therapy along or in combination with an ICD improves symptoms, reduces major morbidity and mortality in patients with a left ventricular EF<35%, ventricular dilatation and a QRS > or = 120 msec in NYHA class III-IV. Further indications are currently being examined.

Biventricular versus conventional right ventricular stimulation for patients with standard pacing indication and left ventricular dysfunction: the Homburg Biventricular Pacing Evaluation (HOBIPACE)

OBJECTIVES

The Homburg Biventricular Pacing Evaluation (HOBIPACE) is the first randomized controlled study that compares the biventricular (BV) pacing approach with conventional right ventricular (RV) pacing in patients with left ventricular (LV) dysfunction and a standard indication for antibradycardia pacing in the ventricle.

BACKGROUND

In patients with LV dysfunction and atrioventricular block, conventional RV pacing may yield a detrimental effect on LV function.

METHODS

Thirty patients with standard indication for permanent ventricular pacing and LV dysfunction defined by an LV end-diastolic diameter > or =60 mm and an ejection fraction < or =40% were included. Using a prospective, randomized crossover design, three months of RV pacing were compared with three months of BV pacing with regard to LV function, N-terminal pro-B-type natriuretic peptide (NT-proBNP) serum concentration, exercise capacity, and quality of life.

RESULTS

When compared with RV pacing, BV stimulation reduced LV end-diastolic (-9.0%, p = 0.022) and end-systolic volumes (-16.9%, p < 0.001), NT-proBNP level (-31.0%, p < 0.002), and the Minnesota Living with Heart Failure score (-18.9%, p = 0.01). Left ventricular ejection fraction (+22.1%), peak oxygen consumption (+12.0%), oxygen uptake at the ventilatory threshold (+12.5%), and peak circulatory power (+21.0%) were higher (p < 0.0002) with BV pacing. The benefit of BV over RV pacing was similar for patients with (n = 9) and without (n = 21) atrial fibrillation. Right ventricular function was not affected by BV pacing.

CONCLUSIONS

In patients with LV dysfunction who need permanent ventricular pacing support, BV stimulation is superior to conventional RV pacing with regard to LV function, quality of life, and maximal as well as submaximal exercise capacity.

Ventricular remodeling during long-term right ventricular pacing following His bundle ablation

To investigate ventricular remodeling during long-term right ventricular (RV) pacing after His bundle ablation (HBA) in patients with atrial arrhythmias, a retrospective analysis was performed on echocardiographic data from 45 patients (mean age 57 +/- 11 years) with atrial arrhythmias who underwent HBA and pacemaker implantation (HBA-PI) to control ventricular rate. Echocardiography was performed 1 year before HBA-PI, and up to 7 +/- 2 years of follow-up was conducted. An inverse linear relation was found between the relative increase of left ventricular (LV) end-diastolic diameter (EDD) during long-term RV pacing and LVEDD before HBA-PI (r = -0.61, p<0.001). Patients were divided into 2 groups: those with LVEDDs smaller than the mean LVEDD of 50 mm (group I, 46 +/- 2 mm, n = 28) and those with LVEDDs >50 mm (group II, 56 +/- 4 mm, n = 17). Before HBA-PI, patients in group I had significantly smaller LV weights (167 +/- 44 vs 238 +/- 56 g) and LV end-systolic diameters (30 +/- 2 vs 42 +/- 7 mm) and higher LV ejection fractions (64 +/- 5% vs 49+/- 12%) than those in group II. In group I, long-term RV pacing increased LVEDD, LV end-systolic diameter, LV weight, and left atrial diameter; increased mitral regurgitation; and decreased the LV ejection fraction and LV fractional shortening. No significant changes were observed during long-term RV pacing in group II. In conclusion, long-term RV pacing after HBA adversely affects LV structure and function in patients with initially normal LV dimensions and function.

[Indication for cardiac resynchronization therapy: Consensus 2005]

The indication for cardiac resynchronization therapy (CRT) using biventricular pacing or ICD systems has to be highly differentiated to optimize the proportion of patients who derive significant symptomatic benefit from this therapy, on the one hand, and to avoid this invasive treatment in patients with a low probability of clinical success of CRT, on the other hand. As a consensus in 2005, it can be put forward that there is sufficient evidence for an indication for CRT from clinical studies for the following characteristics: 1) Heart failure in NYHA functional class III or IV (if cardiac recompensation to class III is at least temporarily successful), 2) left ventricular ejection fraction < or =35%, 3) QRS duration >130 ms, particularly if left bundle branch block is present, 4) sinus rhythm. In addition, available data also suggest an indication for CRT in patients with atrial fibrillation if the other criteria listed above are met. The indication for CRT is unclear in patients with other intraventricular conduction delay (particularly right bundle branch block) while patients with left bundle branch block and a QRS duration of 120-130 ms seem to benefit if echocardiographic criteria demonstrate ventricular dyssynchrony. Since a multiplicity of echocardiographic criteria of ventricular dyssynchrony exists which is neither standardized nor evaluated in large-scale randomized trials, ventricular dyssynchrony on echocardiography alone cannot be regarded as an established indication for CRT without a QRS complex > or =120 ms. Similarly, whether heart failure in functional state NYHA II should be regarded as a CRT indication is currently being investigated in the randomized RAFT and MADIT-CRT trials.

Controversies in pacing: Indications and programming

This article reviews controversies in cardiac pacing in four areas: methods to prevent unnecessary right ventricular pacing and optimal ventricular pacing sites in the bradycardia population, pacing for prevention of atrial fibrillation (AF), a novel pacing technique for the treatment of heart failure, and pacing for the treatment of sleep apnea. Frequent right ventricular pacing has been reported to increase the incidence of AF and congestive heart failure. However, many patients with pacemakers for bradycardia have intrinsic atrioventricular conduction most of the time. Optimal programming of pacemakers and new algorithms designed to reduce unnecessary ventricular pacing are discussed. Pacing algorithms for prevention of AF have generally been shown to be ineffective. Atrial antitachycardia pacing has been shown to reduce the burden of atrial tachyarrhythmias in selected patients. Cardiac contractility modulation has recently been reported to be a promising new approach to the treatment of heart failure. Some pacing techniques may be effective in the treatment of sleep apnea but larger, long-term clinical trials are required to demonstrate a significant clinical benefit.

[Peculiarities in the follow up of resynchronization therapy]

While resynchronization therapy (CRT) is based on conventional pacemaker- and ICD technology, its main intention is to minimize inter- and intraventricular asynergy and to establish optimal AV timing if sinus rhythm is preserved. The focus of this contribution is a series of conditions which jeopardize the therapeutic goal of CRT and should be recognized and hopefully corrected during follow up of CRT systems. These scenarios include uncertainties about left ventricular capture, double sensing in the ventricles, inhibition of the ventricular output (and loss of resynchronization), atrial and ventricular tachycardia and rate adaptation. Technical issues of following rhythm management devices are only discussed in the context of CRT requirements.