Abnormal blood-pressure response to exercise and oxygen consumption in patients with hypertrophic cardiomyopathy

Background Abnormal blood-pressure response during exercise occurs in about one third of patients with hypertrophic cardiomyopathy (HCM), and it has been associated with a high risk of sudden cardiac death. We assessed the hemodynamics of exercise in HCM patients with abnormal blood-pressure response by using ambulatory radionuclide monitoring (VEST) of left-ventricular (LV) function, and exercise tolerance by oxygen consumption. Methods Twenty-two HCM patients uderwent treadmill exercise during VEST monitoring. A cardiopulmonary exercise test was performed a few days after. The VEST data were averaged for 1 minute. Stroke volume, cardiac output, and systemic vascular resistance were expressed as percent of baseline. Exercise tolerance was assessed as maximal oxygen consumption. Results In eight HCM patients (36%) with an abnormal blood-pressure response, endsystolic volume increased more (52%±21% vs 31%±28%, P=.012), and the ejection fraction (−31%±17% vs−14%±22%, P=.029) and stroke volume (−21%±21% vs 3%±28%, P=.026) fell more, than in patients with normal response. Cardiac output increased less in the former patients (49%±44% vs 94%±44%, P=.012). Systemic vascular resistance decreased similarly, irrespective of blood-pressure response (−28%±26% vs −34%±26%. P=N.S.). Percent of maximal predicted oxygen consumption was lower in HCM patients with an abnormal blood-pressure response (63%±11% vs 78%±15%, P=.025). Conclusions In HCM patients, abnormal blood-pressure response was associated with exercise-induced LV systolic dysfunction and impairment in oxygen consumption. This may cause hemodynamic instability, associated with a high risk of sudden cardiac death.