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

Does biventricular pacing improve hemodynamics in children undergoing routine congenital heart surgery?

Biventricular (BiV) pacing or cardiac resynchronization therapy (CRT) is an established therapy for heart failure in adults. In children, cardiac dyssynchrony occurs most commonly following repair of congenital heart disease (CHD) where multisite pacing has been shown to improve both hemodynamics and ventricular function. Determining which patient types would specifically benefit has not yet been established. A prospective, repeated measures design was undertaken to evaluate BiV pacing in a cohort of children undergoing biventricular repair for correction of their CHD. Hemodynamics, arterial blood gas, electrocardiographic (ECG), and echocardiographic data were collected. Pacing protocol was undertaken prior to the patient's extubation with 20 min of conventional right ventricular (RV) or BiV pacing, preceded and followed by 10 min of recovery time. Multivariate statistics were used to analyze the data with p values <0.05 considered significant. Twenty-five (14 female) patients underwent surgery at a median (range) age of 5.2 (0.1-37.4) months with no early mortality. The Risk-adjusted classification for Congenital Heart Surgery (RACHS) scores were 2 in 14 patients, 3 in eight patients, and 4 in three patients. None had pre-existing arrhythmias, dyssynchrony, or required pacing pre-operatively. No patient required implantation of a permanent pacemaker post-operatively. The median cardio-pulmonary bypass time was 96 (55-236) min. RV and BiV pacing did not improve cardiac index from baseline (3.23 vs. 3.42 vs. 3.39 L/min/m2; p > 0.05). The QRS duration was not changed with pacing (100 vs. 80 vs. 80 ms; p > 0.05). On echocardiography, the time-to-peak velocity difference between the septal and posterior walls (synchrony) during pacing was similar to baseline and was also not statistically significant. BiV pacing did not improve cardiac output when compared to intrinsic sinus rhythm or RV pacing in this cohort of patients. Our study has shown that BiV pacing is not indicated in children who have undergone routine BiV congenital heart surgery. Further prospective studies are needed to assess the role of multisite pacing in children with ventricular dyssynchrony such as those with single ventricles, those undergoing reoperation or those with high RACHS scores.

[Cardiac resynchronization therapy for heart failure - from experimental pacing to evidence-based therapy]

Within the last decade, cardiac resynchronization therapy (CRT) has become an evidence-based cornerstone for a subset of patients with chronic heart failure. For those, who suffer from ischemic or non-ischemic cardiomyopathies at NYHA III or IV, have sinus rhythm, a left bundle branch block and a left ventricular ejection fraction below 35%, CRT has evolved as an important treatment option with promising results. Numerous studies have shown that in these patients pacemaker-mediated correction of intra- and interventicular conduction disturbances can improve not only clinical symptoms, exercise tolerance and the frequency of hospitalizations, but even more important the overall mortality. These clinical results are due to several functional aspects. In the failing heart characteristic intra- and interventricular alterations in electrical conduction result in mechanical asynchrony that leads to an abnormal contraction of the left ventricle with delayed activation of the lateral wall, a paradoxical septal movement, a reduced diastolic filling and a mitral regurgitation due to dyssynchrony of papillary muscle activation. It is conceivable that these functional changes have fatal consequences for the failing heart. AV-optimized left- or biventricular stimulation by modern pacemakers can correct the pathological dyssynchrony, thereby improving cardiac function and clinical outcome in these patients. Although tremendous progress in cardiac resynchronization therapy has been made during the last decade, a couple of questions still need to be resolved. Critical issues are the identification of patients, who will predictably benefit from CRT, the value of CRT-pacemakers versus CRT-ICDs, and the usefullness of CRT in patients with atrial fibrillation.

Atrioventricular delay optimization by doppler-derived left ventricular dP/dt improves 6-month outcome of resynchronized patients

BACKGROUND

Atrioventricular (AV) interval optimization, ensuring the best filling and the abolishment of presystolic mitral regurgitation, is crucial for the efficacy of cardiac resynchronization therapy (CRT). The methods proposed to optimize AV delay have many limitations. The maximum left ventricular pressure derivative (LV dP/dt)--an index of cardiac performance--could provide a clue for AV optimization. DP/dt can be calculated by the Doppler curve of mitral regurgitation jet and it is related to micromanometer-derived dP/dt.

AIM

The aim of this study was to assess whether optimal AV delay, defined as the highest noninvasive dP/dt, may provide clinical and functional benefits in CRT patients.

METHODS

Of 41 consecutive patients, 23 echo Doppler recordings were obtained at AV delays of 60, 80, 100, 120, 140, 160, 180 ms (Group I). Three patients were discarded because of suboptimal Doppler signal. In 15 patients an empiric AV delay of 120 ms was chosen (Group II). Both groups were programmed to atriosynchronous pacing mode and synchronous VV stimulation.

RESULTS

In Group I optimal AV delay was 60 ms in one patient, 80 ms in 6, 100 in 6, 120 in 8, 140 in 2. At 6 months follow-up, Group I showed a significantly lower NYHA class (2.1 +/- 0.1 vs 3 +/- 0.2 P < 0.01) and higher LV ejection fraction (LVEF): 32.1 + 1 versus 27.5 +/- 1.6% (P < 0.05) as compared to Group II.

CONCLUSIONS

Doppler-derived dP/dt for AV delay optimization determines better functional class and LVEF at 6 months follow-up relative to an empiric AV delay program.

Role of resynchronisation therapy and implantable cardioverter defibrillators in heart failure

The worldwide prevalence of heart failure is increasing in part because of an aging population. In the developed world, heart failure affects 1%-2% of the general population, accounting for 5% of adult hospital admissions. There is now convincing evidence supporting the beneficial effects of cardiac resynchronisation therapy for the treatment of heart failure. Numerous observational studies, as well as a series of randomised controlled trials, have shown the safety, efficacy, and long term benefits for patients with chronic systolic heart failure who have broad QRS complexes and refractory symptoms despite optimal medical therapy. These studies have consistently found statistically significant improvements in quality of life, New York Heart Association functional class, exercise tolerance, and left ventricular reverse remodelling. Recent evidence suggests that the benefit may at least in part be because of a reduction in mechanical dysynchrony.

Antiinflammatory Effects of Cardiac Resynchronization Therapy in Patients with Chronic Heart Failure

BACKGROUND

Cardiac resynchronization therapy (CRT) pacing has been proposed as an additional treatment to medical therapy to improve heart failure patients with left ventricular asynchrony. The aim of this study was to evaluate the influence of CRT treatment on proinflammatory cytokines in patients with heart failure.

METHODS

Twenty patients, with a mean age 64 +/- 2 years, with severe chronic heart failure NYHA class II-IV (mean ejection fraction 25 +/- 2%), were included in the study. Patients were treated with CRT pacing, after failure of optimal therapy. Blood samples were taken at baseline, 3 months after pacing therapy, and after a subsequent 3-month period of no pacing for the assessment of proinflammatory cytokines TNF-alpha and its receptors (sTNFR-I, sTNFR-II), IL-6, adhesion molecules sICAM-1 and sVCAM-1, and the apoptotic indices sFas and sFas-Ligand.

RESULTS

Levels of TNF-alpha, sTNFR-I, and sTNFR-II were reduced at the end of 3 months of CRT therapy and further reduced at the end of the no pacing period (P < 0.05, compared to baseline). Levels of IL-6 also declined after 3 months of CRT pacing (from 8.9 +/- 2.5 pg/mL to 4.7 +/- 1.3 pg/mL, P < 0.05) and this was maintained during the no pacing period (3.9 +/- 1.1 pg/mL P < 0.05 compared to baseline). The adhesion molecule sICAM-1 levels also reduced (from 265 +/- 17 ng/mL to 235 +/- 12, P < 0.05) after 3 months of CRT pacing and remained unchanged at the end of the no pacing period (219 +/- 12 ng/mL, P < 0.05 compared to baseline values).

CONCLUSION

Major proinflammatory cytokines and the adhesion molecule sICAM-1 are reduced with CRT therapy and this effect is maintained for at least 3 months after discontinuation of pacing.

Time course of left ventricular volumes in severe congestive heart failure patients treated by optimized AV sequential left ventricular pacing alone--a 3-dimensional echocardiographic study

BACKGROUND

This study evaluates the acute and chronic resynchronizing effects of AV sequential left ventricular (LV) pacing on LV function in patients with impaired cardiac function and conduction disorders by 3-dimensional transesophageal echocardiography.

METHODS AND RESULTS

Twenty-nine patients with congestive heart failure, with LV ejection fraction (LVEF) < or = 30%, QRS duration > or = 120 milliseconds, and New York Heart Association Class II to IV, were implanted with a cardiac resynchronization device using an LV lead only, according to the invasively determined hemodynamic optimal pacing site and AV delay. Patients underwent 3-dimensional transesophageal echocardiography before randomization to treatment (baseline) and at 12-month follow-up (resynchronization--12 months). Three-dimensional volumes were acquired on resynchronization and during intermittent switch-off at intrinsic depolarization. The values of stroke volume were 43.2 +/- 13.3 (intrinsic-baseline), 51.7 +/- 17.4 (intrinsic--12 months), 57.2 +/- 15.6 (resynchronization-baseline), and 64.6 +/- 18.9 (resynchronization--12 months). Analysis of variance demonstrated a significant effect of resynchronization at different periods (P < .001) and a significant time effect (P < .05) for stroke volume. Similar results were observed with ejection fraction (LVEF). No effect was observed with LV end-diastolic volume, whereas a therapy effect with no time effect was observed with LV end-systolic volume.

CONCLUSIONS

A significant acute increase of LV stroke volume and LVEF was found by resynchronization by LV pacing alone. A continuous improvement of LV stroke volume and LVEF occurred with time of follow-up (reverse remodeling). The initial therapeutic effect persisted during 12-month follow-up independently of time of follow-up and QRS width. No significant decrease of LV end-diastolic size during chronic resynchronization was detected in contrast to previous studies with resynchronization by biventricular pacing.

A Fast and Simple Echocardiographic Method of Determination of the Optimal Atrioventricular Delay in Patients After Biventricular Stimulation

The optimization of atrioventricular (AV) delay is known to significantly contribute to maximum cardiac performance. The aim of this study was to validate a new, fast, and simple echocardiographic method of identifying the AV delay that provides the maximum cardiac output (CO). Right heart catheterization and Doppler echocardiography of transmitral filling were performed simultaneously in 18 patients with heart failure and at least minimum functional mitral regurgitation treated with atrial synchronized biventricular pacing. CO derived from catheterization and Doppler filling parameters were measured at the predicted optimal AV delay (oAVD), the short AV delay (oAVD - 50 ms), and the long AV delay (oAVD + 28 ms on average/range, +10 ms to +50 ms) during a constant heart rate. The AV delay was regarded as optimal if the end of atrial contraction (represented by the end of A wave of transmitral filling) coincided with the beginning of ventricular contraction (heralded by the onset of the systolic component of mitral regurgitation). Prediction of the optimal AV delay included the following steps: (1) The maximum AV delay at which full ventricular capture is still preserved was found under electrocardiographic control. (2) This value, decreased by 5 to 10 ms, was designated as "the testing long AV delay," and the time interval from the end of the A wave to the onset of the systolic component of mitral regurgitation (time t1) was measured at this setting. (3) oAVD was simply calculated as "the testing long AV delay"- time t1. The CO measured at the oAVD (4.5 +/- 0.7 1. min-1) significantly exceeded those at the short AV delay (4.3 +/- 0.7 1. min-1, P < 0.01) and the long AV delay (4.4 +/- 0.8 1. min-1, P < 0.01), respectively. The method correctly determined the maximum CO in 78% of the patients. In conclusion, Doppler echocardiography enables very rapid and accurate optimization of AV synchrony in patients after the implantation of a biventricular pacemaker.

How many patients with dilated cardiomyopathy may potentially benefit from cardiac resynchronization therapy?

The clinical and electrocardiographic Marburg Cardiomyopathy database was analyzed to identify potential candidates for cardiac resynchronization therapy (CRT) with biventricular or left ventricular pacing among 566 patients with dilated cardiomyopathy (DCM). All of the following restrictive selection criteria were fulfilled by 38 patients (7%): NYHA functional class > or = 3 (n = 193, 34%), left ventricular ejection fraction (LVEF) < 30% (n = 238, 42%), sinus rhythm (n = 437, 77%), left bundle branch block (LBBB, n = 142, 25%), and QRS duration > or = 150 ms (n = 136, 24%). In 78 of the 566 patients (14%) all of the following less restrictive selection criteria were fulfilled: NYHA functional class > or = 3 (n = 193, 34%), LVEF < 35% in presence of any underlying rhythm (n = 326, 58%), QRS duration > or = 120 ms with right or left bundle branch block (n = 223, 39%). Thus, between 7% and 14% of patients with DCM were candidates for CRT depending on the application of strict versus less restrictive selection criteria.

Temporary and permanent biventricular pacing via left ventricular epicardial leads implanted during primary cardiac surgery

OBJECTIVES

Biventricular pacing (BVP) is a new strategy for treating patients with severe congestive heart failure (CHF) and intraventricular conduction delay, but its full potential and technicalities of BVP require further evaluation. We evaluated BVP benefits in 4 patients in whom we implanted a left ventricular lead during primary cardiac surgery.

METHODS

Four CHF patients treated surgically between October 2000 and August 2001 underwent, at primary surgery, the implantation of leads in the right atrium, right ventricle, and left ventricle (LV) for postsurgical BVP. All patients had severe LV dysfunction and dilatation with intraventricular conduction delay. Surgeries involved CABG alone (n = 1), CABG + Dor's operation (n = 2), and tricuspid valve replacement + Maze procedure (n = 1). BVP was begun immediately after surgery in all 4 patients. Hemodynamic variables with BVP were compared to those without BVP for each patient, and the utility and technical aspects of implantation were evaluated.

RESULTS

BVP increased mean systemic blood pressure by 11% and mean LV stroke work index by 19% in the acute postsurgery period, and reduced mitral regurgitation. Two of the patients were implanted with a generator for permanent BVP, one at 1 month and the other at 6 months after surgery. The threshold of the LV epicardial lead of these 2 patients was below 2 V during follow-up, and BVP was successful.

CONCLUSIONS

Temporary BVP during the short-term after cardiac surgery improved cardiac function and decreased mitral regurgitation in all 4 of our patients. Epicardial lead implantation may thus be a useful option during surgical treatment of patients with CHF and intraventricular conduction delay if long-term permanent BVP is indicated.

Biventricular pacing in a patient with severe congestive heart failure

We report a case of dilated cardiomyopathy with severe congestive heart failure (ejection fraction: 19%) and complete left bundle branch block (QRS duration: 240 ms) 13 years after aortic valve replacement. Permanent biventricular pacing was implanted by inserting a left ventricular lead thorough a small left thoracotomy following intravenous insertion of right atrial and ventricular endocardial leads. Biventricular pacing increased hemodynamic parameters such as blood pressure, cardiac output and decreased mitral regurgitation. Symptoms and exercise tolerance improved dramatically. Left ventricular epicardial lead insertion via a small thoracotomy is thus useful in selected patients.

Current status and future expectations for multisite pacing in heart failure

The number of patients with congestive heart failure (CHF) has achieved astonishing proportions. It is a debilitating and usually lethal condition, aside from being responsible for an enormous proportion of health care expenditures. Advances in medical therapy have not been sufficient to significantly improve prognosis, and heart transplantation can only benefit a minority of patients. Biventricular pacing has emerged as a promising form of therapy for patients with severe, medical refractory CHF with ventricular conduction defects. However, there are many technical issues to be solved, and better methods of selecting patients who respond favorably to this form of therapy are yet to be developed. This article reviews the rationale, delivery modes, and available data supporting multisite cardiac pacing as an alternative form of therapy for the failing heart.