Exercise-induced abnormal blood pressure responses are related to subendocardial ischemia in hypertrophic cardiomyopathy

Objectives. We examined by thallium-201 scintigraphy whether exercise-induced abnormal blood pressure response (BPR) is related to myocardial ischemia.

Background. Hemodynamic instabilities during exercise in patients with hypertrophic cardiomyopathy (HCM) are considered to be caused by abnormal reflex control of vascular resistance.

Methods. In 105 patients with HCM, exercise thallium scintigraphy was performed by means of a multistage, symptom-limited bicycle ergometer exercise test.

Results. Eighty-eight patients had normal BPR (≥25 mm Hg from baseline to peak exercise), and 17 had abnormal BPR (<25 mm Hg). Clinical characteristics including age, the prevalence of obstruction, New York Heart Association functional class and echocardiographic measurements were similar between the two groups. Left ventricular end-diastolic pressure was significantly higher in patients with abnormal BPR than in those with normal BPR (18 ± 8 vs. 14 ± 5 mm Hg, p < 0.05). Exercise-induced perfusion abnormalities including fixed and reversible perfusion defects, and left ventricular cavity dilatation (LVCD) were identified in 72 (69%) of 105 study patients. Left ventricular cavity dilatation indicates subendocardial hypoperfusion and is a marker of diffuse subendocardial ischemia. The prevalence of fixed or reversible perfusion defects was similar between the two groups. Patients with abnormal BPR had the higher prevalence of LVCD as compared to those with normal BPR (47.1 vs. 10%, p < 0.0002). Multiple logistic regression analysis revealed that LVCD was independently associated with abnormal BPR (odds ratio 3.76, 95% confidence interval 1.61 to 8.76).

Conclusions. Exercise-induced abnormal BPRs in patients with HCM are related to subendocardial ischemia during exercise.