Analysis of alteration of blood pressure response to exercise through baroreflex.

BACKGROUND: The baroreflex has been reported to play an important role in hemodynamic regulation during exercise. Therefore, impairment of baroreflex function can induce an abnormal response of systolic blood pressure (SBP) to exercise, including exercise-induced hypertension. To clarify whether baroreflex function alters SBP response, we examined the relationship of baroreflex sensitivity (BRS) with SBP response to exercise. METHODS: In 22 subjects without cardiac dysfunction, BRS (ms/mmHg) was measured by the phenylephrine method, and a treadmill exercise test was administered according to Bruce's protocol. RESULTS: 1) The chronotropic response to exercise was higher in the normal BRS group than in the reduced BRS group (p<0.01). The SBP at the initial phase of exercise (1 min after the start of exercise) showed a smaller increase in the normal BRS group than in the reduced BRS group (p<0.01). During the initial phase of exercise, BRS had negative correlation with the SBP increment from rest (r=-0.408, p<0.05). During submaximal exercise (6 min after the start of exercise), a positive correlation between BRS and SBP response (r=0.422, p<0.05) was shown. 2) Subjects were divided into 2 groups: 12 subjects with normal BRS (> or =5 ms/mmHg) and 10 subjects with reduced BRS (<5 ms/mmHg). During the initial exercise phase, the negative correlation between BRS and SBP response was stronger in the normal BRS group (r=-0.398) than in the reduced BRS group (r= -0.126). During submaximal exercise, BRS had a positive correlation with BP response to exercise in subjects with normal BRS (r=0.462). CONCLUSION: Preserved baroreflex function is thought to be related to the pressor response to submaximal exercise, although the baroreflex is thought to be associated with the stabilization of blood pressure change during the initial exercise phase. These findings suggest that exercise-induced hypertension develops through the baroreflex mechanism.

[Detection of myocardial ischemia by analysis of the shape of exercise-induced ST elevation in infarct-related leads].

OBJECTIVES: Possible mechanisms of exercise-induced ST elevation in infarct-related leads include ventricular dyskinesis, and myocardial ischemia in the infarct region. Detection of ischemia in viable myocardium in the infarct region is important to determine the therapeutic strategy. This study evaluated whether the analysis of the shape of exercise-induced ST elevation(convex or concave type) is useful to detect myocardial ischemia in the infarct region. METHODS: Ninety-eight patients (78 males, 20 females, mean age 59 +/- 10 years) with prior Q wave myocardial infarction underwent the treadmill exercise test. Patients were divided into three groups according to the exercise-induced ST changes: No ST-E group, 27 patients without ST changes; Concave ST-E group, 52 patients with concave type ST elevation; Convex ST-E group, 19 patients with convex type ST elevation. Coronary arteriography was evaluated in all patients. Dobutamine stress echocardiography was performed in 38 patients, including 28 patients in the Concave ST-E group and 10 patients in the Convex ST-E group. Biphasic or worsening response on dobutamine stress echocardiography was defined as ischemic response. RESULTS: Coronary arteriography revealed significant stenosis of the infarct-related artery in 30% of the No ST-E group, 47% in the Convex ST-E and 86% in the Concave ST-E groups (p < 0.05). Dobutamine stress echocardiography revealed myocardial ischemia in the infarct region in 30% in the Convex ST-E group and 75% in the Concave ST-E group(p < 0.05). CONCLUSIONS: The Concave ST-E group had a higher incidence of stenosis of the infarct-related artery and myocardial ischemia in the infarct region. Analysis of the shape of exercise-induced ST elevation in infarct-related leads is useful for the detection of ischemia of viable myocardium.