title: Effect of certain antiadrenergic agents on systolic time intervals in essential hypertension.
abstract: Systolic time intervals, including preejection period (PEP) and left ventricular ejection time (LVET), were studied in patients with permanent essential hypertension before and after intra-venous administration of propranolol 0.2 mg/kg (11 patients), clonidine 0.002 mg/kg (10 patients) and methyldopa 2 mg/kg (12 patients). With propranolol, diastolic blood pressure was unchanged and the heart rate decreased, whilst PEP and LVET were significantly prolonged (P less than 0.001). Clonidine caused a fall in blood pressure (P less than 0.001), heart rate was slightly reduced, PEP was prolonged (P less than 0.001) and there was a significant decrease in LVET at 5 min. With methyldopa, no significant effect was observed after intravenous injection, but 7 days oral administration produced the identical effect as clonidine. These observations suggest that certain antihypertensive drugs may impair left ventricular performance and depress myocardial contractility.
mesh_terms: D000328:Adult; D003000:Clonidine / Q000494:pharmacology; D004562:Electrocardiography; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D008750:Methyldopa / Q000494:pharmacology; D008875:Middle Aged; D011433:Propranolol / Q000494:pharmacology; D013565:Sympatholytics / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D013565:Sympatholytics; D008750:Methyldopa; D011433:Propranolol; D003000:Clonidine