Muscle metaboreflex is capable of inducing substantial enhancement in cardiac performance, stroke volume (SV), and cardiac output (CO) (1,2). This study was designed to determine the hemodynamic effect of acute vasodilatation induced by sublingual isosorbide-dinitrate administration during the metaboreflex elicited by post-exercise muscle ischemia (PEMI). We hypothesized that in this setting, because of the heart rate (HR) elevation induced by systemic vascular resistance (SVR) reduction, the blood pressure (BP) and the SV response was blunted compared with the standard PEMI. Ten healthy subjects were enrolled. Their hemodynamic response was assessed by means of impedance cardiography during the PEMI, the recovery from a control dynamic exercise (CER), the metaboreflex after isosorbide administration (IS). During PEMI test a BP increment took place in comparison with the CER and the IS test mainly due to an SV-induced CO increase. During the IS test there was a blunted BP response compared to both the PEMI and the CER test due to SVR decrement. Finally, IS induced tachycardia which was responsible for a reduced capacity to elevate SV. These results suggest that in response to the muscle metaboreflex activation a complex modulation of the chronotropic status of the heart, cardiac performance, and systemic vascular resistance takes place.

1) Crisafulli et al. Am. J. Physiol. (Heart Circ. Physiol.) 2006

2) Crisafulli et al. Exp. Physiol. 2008.