Forearm blood-flow responses to isoproterenol were markedly attenuated in normotensive blacks, indicating a blunting of vasodilatation mediated by beta 2-adrenergic receptors. Sympathetic activity in the forearm was greater in blacks than in whites, but isoproterenol-stimulated presynaptic beta 2-adrenergic responses (which facilitated norepinephrine release) did not differ significantly between blacks and whites. Our findings suggest that the mechanisms responsible for blunted vasodilatation in response to the administration of isoproterenol may contribute to enhanced vascular reactivity in blacks and may play a part in the pathogenesis of hypertension in blacks.

Impaired beta adrenoceptor-mediated vasodilation associated with enhanced sympathetic activity has been reported in established hypertension. We examined whether altered beta adrenoceptor-mediated vasodilation occurs early in the disease process, when structural vascular changes are likely to be less marked, by measurement of forearm blood flow by strain gauge plethysmography after the intraarterial administration of increasing doses of a beta receptor agonist, isoproterenol, in eight subjects with borderline hypertension (BHT) and 13 normotensive (NT) controls. To determine the role of sympathetic activation in the regulation of responsiveness, we measured local sympathetic activity in the forearm by a radioisotope dilution technique. Vasodilation in response to isoproterenol, measured either as changes in forearm blood flow or forearm vascular resistance, was impaired in the BHT group so that flow at the highest dose of isoproterenol (400 ng/min) increased less (15.2±1.5 ml/ 100 ml per min) than in the NT group (24.4±2.4 ml/100 ml per minute) (P < 0.001). Although, systemic norepinephrine spillover was significantly greater in BHT, the difference in blood flow response to isoproterenol was not accounted for by increased local sympathetic activity since forearm norepinephrine spillover at baseline (BHT 1.0±0.4 ng/min vs. NT 0.64±0.13 ng/min) and after the administration of isoproterenol 60 ng/min (BHT 5.2±1.4 ng/min vs. NT 6.0±1.5 ng/min) and 400 ng/min (BHT 13.5±2.9 ng/ min vs. NT 16.5±2.7 ng/min) did not differ between the two groups. We therefore conclude that vasodilation in response to isoproterenol is impaired in subjects with BHT and that this impairment is not explained by locally increased basal, or stimulated, sympathetic activity. (J. Clin. Invest. 1995. 96:579-585.)

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As ventricular-assist devices (VADs) are increasingly employed in heart failure management, a leading cause of mortality, new literature is consistently published on less-invasive implantation techniques. Although early perioperative outcomes have been shown to be favorable with minimally invasive left thoracotomy (LT) approaches compared with conventional sternotomy (CS), studies comparing long-term outcomes are lacking. We set out to evaluate long-term follow up between LT and CS approach. In a single center, retrospective review, data on patients with similar demographic profiles were collected. HeartWare (HVAD) implantation was performed by either CS or LT. Analysis was performed on perioperative adverse outcomes, and 6 month postoperative adverse events. Primary objectives of the study included comparative outcomes of morbidity and mortality between both groups at 180 days postimplantation. Eighty-one (n = 81) bridge to transplant (BTT) patients underwent CS or LT HVAD implantation. Perioperative transfusion (p = 0.04) favored the LT cohort compared with CS, with a median of 6 units and 8 units transfused for each group, respectively. No survival difference was observed between both groups at 6 months postimplantation (p = 0.52). Clinical outcomes at an average of 6 month follow up showed no difference in adverse events, including common postoperative VAD complications such as infection and right heart failure. Miniaturization of LVAD size and improvement in technology has allowed expansion of interest in alternative surgical approaches for HVAD implantation. For BTT patients, no difference in early outcome was observed 6 months after implantation using a left LT versus CS technique.