925-42 Augmented Plasma Norepinephrine and Blood Pressure Responses to Submaximal Exercise with Impaired Chronotropic Response in Patients with Hypertrophic Cardiomyopathy

Background It is reported that there maya link between abnormal catecholamine metabolism and hyperthropic cardiomyopathy (HCM). However, there are controversies about plasma catecholamine levels in patients with HCM. Studies were limited about serial measurements in plasma catecholamine during exercise. This study determined if cardiovascular and plasma catecholamine responses to exercise were altered in HCM. Methods 17 patients with HCM (15 male, 2 female, mean age: 54 ± 2) and 17 age-sex matched controls were evaluated by submaximal treadmill exercise test using Bruce protocol. Plasma norepinephrine (NE) and epinephrine (E) were measured at rest, at the end of each stage during exercise and immediately after exercise. Results Exercise duration was shorter in HCM (Control vs HCM: 11.2 ± 0.6 vs 8.7 ± 0.6 min, p l 0.01). Mean blood pressure were higher at stage I (100 ± 10 vs 109 ± 3mmHg, p l 0.05) and at stage II (101 ± 3 vs 112 ± 3 mmHg, p l 0.01) in HCM. Resting NE levels (151 ± 15 vs 168 ± 23 pg/ml, n.s.) were not different. but NE at stage I (253 ± 25 vs 400 ± 57 pg/ml, p l 0.05) and at stage II (314 ± 31 vs 550 ± 89 pg/ml, p l 0.05) were significantly higher in HCM. Peak NE levels (534 ± 52 vs 724 ± 102 pg/ml, n.s.) were insignificantly higher in HCM. Heart rate response was similar in both groups, but the ratio of the increment in heart rate divided by the increment in NEat stage I (0.47 ± 0.09 vs 0.17 ± 0.03, p l 0.01) and at stage II (0.37 ± 0.05 vs 0.20 ± 0.04, P l 0.05) were significantly less in HCM. There were no difference in E responses during exercise in both groups. Conclusion Patients with HCM had augmented plasma NE levels during submaximal treadmill exercise test with higher blood pressure response compared to controls. In addition, chronotropic sympathetic responsiveness was impaired in patients with HCM.