Resting heart rate and heart rate reserve in advanced heart failure have distinct pathophysiologic correlates and prognostic impact: a prospective pilot study.

OBJECTIVES: The purpose of this study was to compare the prognostic impact of clinical and biomarker correlates of resting heart rate (HR) and chronotropic incompetence in heart failure (HF) patients. BACKGROUND: The mechanisms and underlying pathophysiological influences of HR abnormalities in HF are incompletely understood. METHODS: In a prospective pilot study, 81 patients with advanced systolic HF (97% were receiving beta-blockers) and 25 age-, sex-, and body-size matched healthy controls underwent maximal cardiopulmonary exercise testing with sampling of neurohormones and biomarkers. RESULTS: Two-thirds of HF patients met criteria for chronotropic incompetence. Resting HR and HR reserve (HRR, a measure of chronotropic response) were not correlated with each other and were associated with distinct biomarker profiles. Resting HR correlated with increased myocardial stress (B-type natriuretic peptide [BNP]: r = 0.26; pro-A-type natriuretic peptide: r = 0.24; N-terminal-proBNP: r = 0.32) and inflammation (leukocyte count: r = 0.28; high-sensitivity C-reactive protein assay: r = 0.25). In contrast, HRR correlated with the neurohumoral response to HF (copeptin: r = -0.33; norepinephrine: r = -0.29) but not with myocyte stress or injury reflected by natriuretic peptides or hs-troponin I. Patients in the lowest chronotropic incompetence quartile (HRR ≤0.38) displayed more advanced HF, reduced exercise capacity, ventilatory inefficiency, and poorer quality of life. Over a median follow-up of 17 months, the combined endpoint of death or urgent transplant/assist device implantation occurred more frequently in patients with higher resting HR (>67 beats/min) or lower HRR, with both markers providing additive prognostic information. CONCLUSIONS: Increased resting HR and chronotropic incompetence may reflect different pathophysiological processes, provide incremental prognostic information, and represent distinct therapeutic targets.

The relationship between right ventricular pacing voltage and QRS complex duration.

Compared to the natural electrical activation of the myocardium through the His-Purkinje system, right ventricular pacing is associated with prolonged QRS complex duration, thereby impeding the synchronicity of contractions. In left ventricular pacing, a higher pacing voltage decreases the QRS complex duration. The aim of our study was to describe the relation between the right ventricular pacing voltage and the QRS complex duration. Fourteen patients (73.6 +/- 7.6 years) with AV block and implanted pacemakers were paced at a frequency of 100 bpm with various pacing voltages. A signal-averaged QRS vector length was calculated at each degree of pacing voltage. The changes in the QRS complex duration were measured as a relative shift of the terminal region of the vectorcardiographic QRS complex (end-shift) and its most prominent peak (peak-shift) using the cross-correlation method. The nonlinear relationship between stimulation voltage and QRS duration was observed with the highest impact of stimulation voltage changes near the threshold value. The fourfold increase in the stimulation voltage above the threshold caused QRS complex shortening by 3.7 +/- 2.1 ms (range 0.19-7.76 ms). Similar peak- and end-shift responses to altered stimulation energy demonstrated that the acceleration of depolarization occurred in the initial portion of the QRS complex. Older electrodes exhibited smaller and more linear changes in the QRS complex duration.

Assessment of left ventricular function in non-dilated and dilated hearts: comparison of contrast-enhanced 2-dimensional echocardiography with multi-detector row CT angiography.

OBJECTIVE: Multidetector-row CT (MDCT) and contrast-enhanced echocardiography (CEE) are being increasingly used for assessment of left ventricular (LV) function. Excellent spatial and contrast resolution of MDCT allows this evaluation along with coronary angiography. CEE improves the accuracy of 2D echocardiography. Data on side-by-side comparison of both techniques for assessment of LV size and function in subjects with a non-dilated or dilated left ventricle are limited. METHODS AND RESULTS: Our study population included 64 patients. Group I included 31 patients with an implanted pacemaker who had a non-dilated left ventricle with preserved systolic function. Group II comprised 33 patients with dilated cardiomyopathy and severe systolic LV dysfunction. LV end-diastolic and end-systolic volumes (LVEDV, LVESV) and ejection fraction (LVEF) were assessed using both CEE and short-axis MDCT. The results obtained by both techniques were compared by linear regression and Bland-Altman analysis. Additionally, intra- and interobserver reproducibility was assessed. Both CEE and MDCT measurements highly correlated (r = 0.61-0.94). However, CEE significantly underestimated LVEDV and LVESV, and this bias was higher with enlarged LV volumes. LVEF was overestimated by CEE in both groups with a higher bias in the group with preserved systolic function. Both intra- and interobserver reproducibility was significantly better for MDCT, the worst reproducibility was observed for CEE in group I. CONCLUSION: Despite a high correlation between MDCT and CEE measurements, CEE provides consistently lower volumes and higher LVEF. This suggests that both methods are not completely interchangeable. Reproducibility of CEE is inferior to reproducibility of MDCT, especially in non-dilated left ventricles with preserved function.

Surgical ablation of post-infarction ventricular tachycardia guided by mapping in sinus rhythm: long term results.

OBJECTIVE: Some patients after myocardial infarction have an increased risk of malignant ventricular tachyarrhythmias (VTA) or sudden cardiac death. The aim of the study was to evaluate long-term results of surgical ablation of an arrhythmogenic substrate guided by simplified intraoperative mapping of pathological ventricular electrograms during sinus rhythm. METHODS: The study population consisted of 77 patients (9 women; mean age 62.4+/-8.5 years) with previous Q-wave myocardial infarction and at least one documented episode of sustained VT/VF more than one month after the last infarction. The left ventricular ejection fraction was 31.3+/-8.8%. All but eight patients had clinical indication for concomitant coronary artery bypass surgery. All underwent preoperative electrophysiologic study. Intraoperative epicardial and endocardial mapping during sinus rhythm was performed using a multielectrode with 16 bipolar electrodes in combination with a multichannel recording system. Myocardial regions revealing fractionated, low amplitude signals lasting > or =130 ms were surgically excised or cryoablated. All surviving patients were restudied within one to two weeks after surgery using identical programmed electrical stimulation protocol. RESULTS: Five (6.5%) patients died in the perioperative (30-days) period. In the remaining cohort, inducibility of any sustained VTA after surgical procedure was observed in 21 subjects (29.2%). An implantable cardioverter-defibrillator (ICD) was implanted in these patients. Recurrence of sustained VTA was documented during follow-up period in two patients who were noninducible after the surgery (at the month 10 and 22, respectively), and both received ICD as well. No patient died of sudden cardiac death. In 14 ICD patients, no significant VTA was documented during the mean follow-up of 37.3+/-23.2 months. Altogether, 61 from the 72 patients surviving the surgery (84.7%) remained free of spontaneous recurrences of VTA during the follow-up. CONCLUSIONS: Surgical ablation of an arrhythmogenic substrate guided by simplified intraoperative mapping in normothermic heart during sinus rhythm appears to be both safe and efficacious procedure that prevents recurrences of VTA in a substantial proportion of patients.