Objective Chest pain is a common finding in patients with hypertrophic cardiom yopathy and can be observed in 40%to 50%of all patients. However, the pathogen esis of these ischemia-like symptoms is still unclear. Methods Twenty-two pati ents with hypertrophic cardiomyopathy and 15 controls underwent positron emissio n tomography for evaluation of regional myocardial perfusion and coronary flow r eserve (hyperemic/baseline myocardial blood flow). Myocardial perfusion (mL/min/ g) was measured using <<13N>>ammonia at rest and during hyperemia with dipyridamol e (0.56 mg/kg intravenously). Regional coronary flow reserve was assessed in 3 p lanes (apical, midventricular, basal) in 4 regions (septal, anterior, lateral, i nferior). Patients were divided into 2 groups: group 1 consisted of 11 patients treated with surgical myectomy (age 56 ±10 years) and group 2 consisted of 11 p atients treated medically (age 53 ±13 years). Results Mean global coronary flow reserve was 3.87 ±0.92 in controls but 2.31 ±0.40 in operated (P < .001 vs co ntrols) and 1.76 ±0.58 in medically treated patients (P < .001 vs controls, P < .05 vs operated). Similarly, septal coronary flow reserve was 4.19 ±1.22 in co ntrols but significantly reduced in operated patients (2.26±0.48, P < .001 vs c ontrols) and in medically treated patients (1.76 ±0.58; P < .001 vs controls). However, septal flow reserve was significantly higher in operated patients than in patients with medically treated hypertrophic cardiomyopathy (+37%, P < .05) , mainly due to a reduced resting myocardial perfusion. Conclusions Global and r egional myocardial perfusion is reduced in patients with hypertrophic cardiomyop athy. However, myectomy may have a beneficial effect on septal perfusion and flo w reserve. Thus, ischemia seems to play an important role in the symptomatology and pathophysiology of hypertrophic cardiomyopathy. Objective Chest pain is a common finding in patients with hypertrophic cardiom yopathy and can be observed in 40% to 50% of all patients. However, the pathogen esis of these ischemia-like symptoms is still unclear. Methods Twenty-two pati ents with hypertrophic cardiomyopathy and 15 controls underwent positron emissio n tomography for evaluation of regional myocardial perfusion and coronary flow r eserve (hyperemic / baseline myocardial blood flow). Myocardial perfusion (mL / min / g) was measured using << 13N >> ammonia at rest and During the period of hyperemia with dipyridamol e (0.56 mg / kg intravenously). Regional coronary flow reserve was assessed in 3 p lanes (apical, midventricular, basal) in 4 regions (septal, anterior, lateral, i nferior). Patients were divided into 2 groups Results group 1 consisted of 11 patients treated with surgical myectomy (age 56 ± 10 years) and group 2 consisted of 11 p patients treated medically (age 53 ± 13 years). Results Mean global coronary flow reserve was 3.87 ± 0.92 in contro ls but 2.31 ± 0.40 in operated (P <.001 vs co ntrols) and 1.76 ± 0.58 in medically treated patients (P <.001 vs controls, P <.05 vs operated). Similarly, septal coronary flow reserve was 4.19 ± 1.22 in co ntrols but significantly reduced in operated patients (2.26 ± 0.48, P <.001 vs c controls) and in medically treated patients (1.76 ± 0.58; P <.001 vs controls). However, septal flow reserve was significantly higher in operated Patients than in patients with medically treated hypertrophic cardiomyopathy (+ 37%, P <.05), mainly due to a reduced resting myocardial perfusion. Conclusions Global and r egional myocardial perfusion is reduced in patients with hypertrophic cardiomyopthy. However, myectomy may have a beneficial effect on septal perfusion and flo w reserve. Thus, latency seems to play an important role in the symptomatology and pathophysiology of hypertrophic cardiomyopathy.