Biventricular pacing-induced acute response in baroreflex sensitivity has predictive value for midterm response to cardiac resynchronization therapy

A Novel and Simple Exercise Test Parameter to Assess Responsiveness to Cardiac Resynchronization Therapy

This study assessed the value of heart rate recovery index (HRRI), a new parameter of an exercise test, as the predictor of response to cardiac resynchronization therapy (CRT). Methods: Consecutive patients receiving a CRT device were followed up after implantation and every 6 months. An effort test (ET) was quantified by minimum heart rate/maximum heart rate, as well as acceleration and deceleration times. HRRI was calculated as the ratio between acceleration and deceleration time (AT/DT) and compared to outcome. We used logistic regression to assess the predictive value of HRRI for responders and non-responders to CRT. The area under the curve (AUC) was computed to distinguish between positive and negative outcomes. Results: A total of 109 patients (74 men, mean age 63.3 ± 9.8 years) were analyzed; permanent long-term fusion CRT pacing was possible in 65 patients. Patients were assigned to two groups: responders and non-responders (98/11 patients). During a mean follow-up of 36 months, 545 ETs were performed. HRRI was significantly higher in responders versus non-responders (3.16 ± 2 vs. 1.4 ± 0.5, p < 0.001). The optimal cutoff value for HRRI as a predictor of CRT response was 1.51 (area under the receiver operating characteristic (ROC) curve = 0.844). Responders had significant left-ventricular (LV) reverse remodeling (LV end-diastolic volume = 240 ± 90 mL vs. 217 ± 89 mL, p < 0.001) and higher LV ejection fraction (26 ± 5.8% vs. 35 ± 8.7%, p < 0.001). Conclusions: HRRI computation during routine ET is useful for the evaluation of responsiveness to CRT.

The arterial baroreflex effectiveness index in risk stratification of chronic heart failure patients who are candidates for cardiac resynchronization therapy

INTRODUCTION

Baroreflex function is an independent marker of prognosis in heart failure (HF). However, little is known about its relation to response to cardiac resynchronization therapy (CRT). The aim of this study is to assess arterial baroreflex function in HF patients who are candidates for CRT.

METHODS

The study population consisted of 25 patients with indication for CRT, aged 65±10 years, NYHA functional class ≥III in 52%, QRS width 159±15 ms, left ventricular ejection fraction (LVEF) 29±5%, left ventricular end-systolic volume (LVESV) 150±48 ml, B-type natriuretic peptide (BNP) 357±270 pg/ml, and peak oxygen consumption (peak VO2) 18.4±5.0 ml/kg/min. An orthostatic tilt test was performed to assess the baroreflex effectiveness index (BEI) by the sequence method. This group was compared with 15 age-matched healthy individuals.

RESULTS

HF patients showed a significantly depressed BEI during tilt (31±12% vs. 49±18%, p=0.001). A lower BEI was associated with higher BNP (p=0.038), lower peak VO2 (p=0.048), and higher LVESV (p=0.031). By applying a cut-off value of 25% for BEI, two clusters of patients were identified: lower risk cluster (BEI >25%) QRS 153 ms, LVESV 129 ml, BNP 146 pg/ml, peak VO2 19.0 ml/kg/min; and higher risk cluster (IEB ≤25%) QRS 167 ms, LVESV 189 ml, BNP 590 pg/ml, peak VO2 16.2 ml/kg/min.

CONCLUSIONS

Candidates for CRT show depressed arterial baroreflex function. Lower BEI was observed in high-risk HF patients. Baroreflex function correlated closely with other clinical HF parameters. Therefore, BEI may improve risk stratification in HF patients undergoing CRT.

Clinical value of baroreflex sensitivity

The arterial baroreflex is an important determinant of the neural regulation of the cardiovascular system. It has been recognised that baroreflex-mediated sympathoexcitation contributes to the development and progression of many cardiovascular disorders. Accordingly, the quantitative estimation of the arterial baroreceptor-heart rate reflex (baroreflex sensitivity, BRS), has been regarded as a synthetic index of neural regulation at the sinus atrial node. The evaluation of BRS has been shown to provide clinical and prognostic information in a variety of cardiovascular diseases, including myocardial infarction and heart failure that are reviewed in the present article.

Heart rate recovery: a practical clinical indicator of abnormal cardiac autonomic function

The autonomic nervous system (ANS) and cardiovascular function are intricately and closely related. One of the most frequently used diagnostic and prognostic tools for evaluating cardiovascular function is the exercise stress test. Exercise is associated with increased sympathetic and decreased parasympathetic activity and the period of recovery after maximum exercise is characterized by a combination of sympathetic withdrawal and parasympathetic reactivation, which are the two main arms of the ANS. Heart rate recovery after graded exercise is one of the commonly used techniques that reflects autonomic activity and predicts cardiovascular events and mortality, not only in cardiovascular system disorders, but also in various systemic disorders. In this article, the definition, applications and protocols of heart rate recovery and its value in various diseases, in addition to exercise physiology, the ANS and their relationship, will be discussed.

Cardiac resynchronization therapy improves exercise heart rate recovery in patients with heart failure

AIMS

Heart rate (HR) recovery (HRR), defined as the rate of decline in the HR immediately following the cessation of exercise, is influenced by autonomic function. Heart rate recovery in heart failure (HF) has been shown to correlate with severity of HF. Cardiac resynchronization therapy (CRT) improves cardiac autonomic functions in HF. We aimed to evaluate the effects of CRT on cardiac autonomic function assessed by HRR.

METHODS AND RESULTS

Forty-eight patients [62.3 ± 10.7 years; 37 men; left ventricular (LV) ejection fraction 24.8 ± 4.1%] with HF were enrolled. A treadmill exercise testing was conducted in all patients by using a modified Naughton protocol before and 6 months after CRT. Heart rate recovery indices were calculated by subtracting first, second, and third minute HR from the maximal HR and designated as HRR1, HRR2, and HRR3, respectively. Standard echocardiography was performed before and 6 months after CRT. Left ventricular reverse remodelling (LVRM) was quantified as the percentage of decline in the LV end-systolic volume after CRT. Mean HRR1 (13.0 ± 5.9 vs. 17.9 ± 8.9 b.p.m., P = 0.001), HRR2 (20.5 ± 9.3 vs. 23.8 ± 11.3 b.p.m., P = 0.001), and HRR3 (25.7 ± 11.1 vs. 29.2 ± 12.0 b.p.m., P = 0.001) values improved 6 months after CRT. Pearson's analyses revealed a good positive correlation between LVRM and ΔHRR1 (r = 0.642, P = 0.001) and a moderate correlation between reduction LVRM and ΔHRR2 (r = 0.591, P = 0.033) and ΔHRR3 (r = 0.436, P = 0.001).

CONCLUSION

Cardiac resynchronization therapy favourably alters the cardiac autonomic functions. Heart rate recovery indices improved after CRT and the degree of improvement in HRR indices correlated with LVRM.