Comparison of Muscle Sympathetic Activity in Ischemic and Nonischemic Heart Failure

Abstract Background The magnitude of sympathetic activation in chronic heart failure is assumed to be independent of its cause. However, because a higher sympathetic component of heart rate variability (HRV) in patients with ischemic cardiomyopathy (ICM) has been reported, we hypothesized that patie...

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Bibliographic Details
Published in:	Journal of cardiac failure 2007-08, Vol.13 (6), p.470-475
Main Authors:	Notarius, Catherine F., PhD, Spaak, Jonas, MD, PhD, Morris, Beverley L., RN, Floras, John S., MD, DPhil
Format:	Article
Language:	eng
Subjects:	Cardiovascular Electric Stimulation Etiology Exercise Tolerance - physiology Female Gated Blood-Pool Imaging Heart Failure - diagnosis Heart Failure - etiology Heart Failure - physiopathology Heart Rate - physiology Humans Left ventricular systolic dysfunction Male Medicin och hälsovetenskap Microelectrodes Microneurography Middle Aged Muscle Contraction - physiology Muscle, Skeletal - innervation Muscle, Skeletal - metabolism Muscle, Skeletal - physiopathology Myocardial Ischemia - diagnosis Myocardial Ischemia - physiopathology Oxygen Consumption Peak exercise capacity Peroneal Nerve - physiopathology Severity of Illness Index Spirometry Stroke Volume - physiology Sympathetic Fibers, Postganglionic - physiopathology Ventricular Dysfunction, Left - diagnosis Ventricular Dysfunction, Left - physiopathology
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Summary:	Abstract Background The magnitude of sympathetic activation in chronic heart failure is assumed to be independent of its cause. However, because a higher sympathetic component of heart rate variability (HRV) in patients with ischemic cardiomyopathy (ICM) has been reported, we hypothesized that patients with ICM would have a higher resting muscle sympathetic nerve activity (MSNA) than patients with nonischemic dilated cardiomyopathy (DCM). Methods and Results Resting MSNA was assessed by microneurography and HRV concurrently by coarse-graining spectral analysis in 30 treated normotensive patients with chronic heart failure (12 with ICM and 18 with DCM), matched for age and left ventricular ejection fraction, and 23 healthy normal control subjects, matched for age and blood pressure. Peak oxygen uptake was determined during graded cycling (17 W/min) to maximum effort. MSNA was significantly different between groups ( P < .001; ICM 60 ± 3; DCM 47 ± 3; control subjects 35 ± 3 bursts/min). Compared with control subjects, the total spectral power and the high-frequency component of HRV were lower in both ICM and DCM groups, but fractal and low-frequency power were lower only in the ICM group ( P < .05). Peak oxygen uptake (milliliters per kilogram of body weight per minute) was significantly less in the ICM group than in the DCM group ( P = .04) and lower in both groups than in the control subjects ( P < .001). Conclusions These observations suggest an additional ischemic stimulus to sympathetic activation in heart failure, which may impair exercise capacity reflexively.
ISSN:	1071-9164 1532-8414 1532-8414