The exercise response in idiopathic dilated cardiomyopathy

Abstract

Summary:In order to more clearly define the exercise response of idiopathic dilated cardiomyopathy (IDC), 20 patients in this study with strictly defined IDC were evaluated with radionuclide ventriculography and invasive hemodynamic monitoring. Severe cardiovascular impairment was present at rest, and peak supine exercise produced progressive left ventricular (LV) dilatation in both diastole and systole (meanf SEM from 172 f 14 to 212f22 ml/m2 at end-diastole and from 137f14 to 170 f 22 d / m 2 at end-systole; both p < 0.03). There were marked increases in LV and right ventricular filling pressure (from 17 f 2 to 36 f 3 mmHg and from 7 f 2 to 15 f 2 mmHg, respectively; both p <O.OOOl) and increased pulmonary artery pressure. Mean LV ejection fraction did not change significantly with exercise (22f2 to 23f3%; p>O.8), but individual patients demonstrated substantial variability. Cardiac output rose less than in normals and increases were brought about primarily by subnormal heart rate increases. High resting and exercise systemic and pulmonary vascular resistance were indicative of limited vasodilator reserve. Despite marked hemodynamic abnormalities, 10 of the 20 subjects had well preserved exercise capacity ( 2 12 min exercise duration). These patients as a group had significantly lower resting heart rate and higher exercise cardiac output and lower exercise systemic vascular resistance. However, they did not differ from the other patients with respect to resting LV function. Thus, the exercise response in IDC has specific characteristics that distinguish it from normal and from the exercise response of other causes of LV dysfunction. An interesting subset of patients with IDC has well preserved exercise capacity associated with greater chronotropic and vasodilator reserve. This finding suggests less sympathetic activation in these subjects.

Exercise physiology with a left ventricular assist device: Analysis of heart-pump interaction with a computational simulator

“…This is in agreement with [3,16,17,18,22], although other works have shown the possibility of hypotension phenomena in HF subjects during exercise with reduced peripheral blood flow [23,24]. …”

“…Such a trend was also observed by [16] although in the upright position [22] the increase in end-diastolic volume is limited. Probably the hydrostatic pressure plays an important role on venous return so that different results could be observed weather the patient is cycling in upright or supine position.…”

“…Ras and Rap in HF were calculated averaging data from [3,16,17,18]. For HF+VAD Ras was calculated considering data from [3,5,13], Rap averaging data from [3,5].…”

“…From a physiological point of view, Pset represents the equilibrium value and it was characterized in the simulator at rest condition: for HF we averaged the mean systemic pressure at rest taken from [3,16,17,18], for HF+VAD we averaged the data of [3,5,13]. During exercise Pset automatically increases due to the “baroreflex resetting phenomenon” that progressively shifts the baroreflex control towards higher pressure levels.…”

“…Concerning the pulmonary vasculature, the hemodynamic data of HF patients show a slight decrease of Rap from rest to exercise (from 0.183 to 0.151 mmHg·s/cm 3 ) [3,16,17,18]. We therefore decided not to implement any hypoxic vasoconstriction mechanism for the pulmonary vasculature.…”