LOW VENTRICULAR PERFORMANCE AND HIGH-RESISTANCE IN ESTABLISHED HYPERTENSION IN ADULTS

Objective: To investigate the relationship between left ventricular pe rformance and sympathetic nervous activity. Design: We studied the alp ha- and beta-adrenergic responsiveness of the subjects and assessed th eir left ventricular performance. Methods: Fifty-four adult establishe d hypertensive patients, all with apparent left ventricular hypertroph y, and 36 age-matched normotensive controls were studied. Thirty-four of the hypertensive patients were within the +/- 2SD confidence area o f fractional shortening/end-systolic stress relation of the normotensi ve controls and are denoted subgroup A; 19 patients were below the low er limit and are denoted subgroup B. Isoproterenol and neosynephrine i njection tests were used to assess beta- and alpha-adrenergic responsi veness, respectively. Intravenous infusion tests using regitine and is oproterenol were performed in 16 patients to assess the effects of sym patho-adrenergic responsiveness on changes in left ventricular perform ance. Results: Afterload and left ventricular mass were similar in the two subgroups. Left ventricular performance and beta-adrenergic respo nsiveness in subgroup A were comparable with the corresponding levels in the normotensives, whereas in subgroup B both were markedly decreas ed. The regitine infusion test induced a fall of 25% in peripheral res istance from baseline, but no significant improvement in left ventricu lar performance. In contrast, isoproterenol infusion test resulted in striking improvements: left ventricular performance increased by 60%, afterload decreased by 48% and peripheral resistance fell by 50% from baseline. Conclusion: The diminished ventricular performance and high resistance observed in adult established hypertension may be due to sy nergic effects of significantly reduced beta-adrenergic responsiveness coupled with enhanced alpha-adrenergic responsiveness.