Cardiac and peripheral autonomic control in restrictive cardiomyopathy

Abstract

Aims: Autonomic dysfunction determines the advance of dilated cardiomyopathy (DCM) and is related to poor outcomes. However, this autonomic imbalance is unknown in patients with restrictive cardiomyopathy (RCM) even though they have similar symptoms and poor quality of life as DCM patients have. The aim of this study was to evaluate if autonomic and neurovascular controls were altered in RCM patients.

Methods and results: Fifteen RCM patients, 10 DCM patients, and 10 healthy subjects were evaluated. Heart rate and blood pressure (BP) were recorded. Peripheral sympathetic activity [muscle sympathetic nerve activity (MSNA)] by microneurography and cardiac sympathetic activity by power spectrum analysis of heart rate variability. Spontaneous baroreflex sensitivity (BRS) was evaluated by the sequence method and forearm blood flow by venous occlusion plethysmography. Both cardiomyopathy groups had higher MSNA frequency (P < 0.001) and MSNA incidence (P < 0.001), higher cardiac sympathovagal balance (P < 0.02), reduced BRS for increase (P = 0.002) and for decrease in BP (P = 0.002), and lower forearm blood flow (P < 0.001) compared with healthy subjects. We found an inverse correlation between BRS for increase and decrease in BP and peripheral sympathetic activity (r = -0.609, P = 0.001 and r = -0.648, P < 0.001, respectively) and between BRS for increase and decrease in BP and cardiac sympathetic activity (r = -0.503, P = 0.03 and r = -0.487, P = 0.04, respectively).

Conclusions: The RCM patients had cardiac and peripheral autonomic dysfunctions associated with peripheral vasoconstriction. Nonetheless, the presence of normal ejection fraction underestimates the evolution of the disease and makes clinical treatment difficult. These alterations could lead to a similar cardiovascular risk as that observed in DCM patients.

Keywords: Baroreflex control; Dilated cardiomyopathy; Heart failure; Neurovascular control; Restrictive cardiomyopathy; Sympathetic activity.

Figure 1

Muscle sympathetic nerve activity (MSNA). (A) The restrictive cardiomyopathy (RCM) and dilated cardiomyopathy (DCM) patients had increased MSNA in burst frequency compared with HS (P < 0.001). (B) The RCM and DCM patients had increased MSNA in burst incidence (P < 0.001) compared with healthy subjects (HS). Note that there were no significant differences between the two groups with cardiomyopathies. One‐way ANOVA was used in all comparisons.

Figure 2

Cardiac autonomic evaluation. (A) Cardiac parasympathetic activity [high‐frequency (HF) normalized units (n.u.), P = 0.005]. (B) Cardiac sympathetic activity [low‐frequency (LF) n.u., P = 0.005]. (C) Cardiac sympathovagal balance [sympathovagal balance (LF/HF), P = 0.02]. Note that restrictive cardiomyopathy (RCM) and dilated cardiomyopathy (DCM) had lower HF n.u., higher LF n.u., and higher LF/HF compared with healthy subjects (HS). For the analysis of cardiac autonomic evaluation, five RCM patients were excluded because of atrial fibrillation. One‐way ANOVA and Kruskal–Wallis test were used in all comparisons.

Figure 3

Spontaneous baroreflex sensitivity (BRS). (A) The BRS for increase in blood pressure (P = 0.003), (B) BRS for decrease in blood pressure (P = 0.004), and (C) sequences of BRS (P = 0.001). Note that restrictive cardiomyopathy (RCM) and dilated cardiomyopathy (DCM) had lower spontaneous BRS and fewer sequences of BRS compared with healthy subjects (HS). One‐way ANOVA was used in all comparisons. BRS+, BRS for increase in blood pressure; BRS−, BRS for decrease in blood pressure.

Figure 4

Forearm blood flow (FBF) and forearm vascular conductance (FVC). (A) The restrictive cardiomyopathy (RCM) and dilated cardiomyopathy (DCM) patients had decreased FBF compared with HS (P < 0.001). Note that there were no significant differences between the two groups with cardiomyopathies. (B) The RCM and DCM patients had decreased forearm vascular conductance (FVC) compared with healthy subjects (HS) (P < 0.001). There were no significant differences between RCM and DCM. One‐way ANOVA was used in all comparisons.