Sympathetic contribution to the cardiac response to stress in hypertension.

Studies of cardiac performance in hypertension have often been restricted to cardiac output determinations, although the latter alone are inadequate for that purpose. To define the range of cardiac performance in hypertension, the response of left ventricular filling pressure to increased workload (static exercise) was determined in 39 subjects--eight normotensive (NT) volunteers, seven patients with borderline hypertension (BLH), and 24 essential hypertensives (EH), of age-matched groups. A rise of mean pulmonary wedge pressure (PWP) by 5 mm Hg or more during maximum handgrip (HG) was considered "abnormal" for a workload (SBP x HR x 10(-3)) increase of greater than or equal to 25%. All NT subjects and all patients with BLH as well as 16 of the 24 EH (EH-I) showed normal cardiac performance by this definition. In contrast, PWP increased greater than or equal to 5 mm Hg during HG in eight patients with EH (EH-II). The calculated increase in cardiac workload was not significantly different among the four groups (+5, 5.8, 5.4 and 5.5 respectively). Beta blockade (propranolol, 10 mg i.v.) slowed heart rate in all subjects and reduced SBP x HR product in all groups both at rest and during HG. Responses of PWP to HG were widely divergent in the different patients. However, as a group those patients with "impaired cardiac performance" before propranolol (EH-II) had a greater reduction in performance following propranolol than EH-I or NT. This study suggests that adrenergic support of cardiac performance might be important in some hypertensive patients with no evidence of heart failure.