| Popis: |
Although there is theoretical and indirect evidence to suggest that patients with severe congestive heart failure may have desensitization of myocardial beta-adrenergic responsiveness, there is little direct evidence in patients. The purpose of this study was to determine whether myocardial beta-adrenergic inotropic responsiveness is reduced in patients with severe congestive heart failure and markedly elevated plasma norepinephrine levels. To assess myocardial beta-adrenergic inotropic responsiveness, the beta-adrenergic agonist dobutamine was infused directly into the left main coronary artery, and the change in +dP/dt was measured as an index of change in inotropic state. Eight patients with severe New York Heart Association functional Class III and IV congestive heart failure were compared with 4 patients without significant congestive heart failure. The increase in +dP/dt at an intracoronary dobutamine infusion rate of 25 micrograms/min in patients with severe congestive heart failure was significantly less than in the patients without heart failure (heart failure, 33 +/- 8%; no heart failure, 69 +/- 12%; p less than 0.05). Although the maximum intracoronary dobutamine infusion rate was substantially higher in patients with heart failure (94 +/- 25 micrograms/min) compared with patients without heart failure (38 +/- 7 micrograms/min), the increase in +dP/dt at maximum infusion rates was also significantly less in patients with heart failure (heart failure, 52 +/- 8%; no heart failure, 93 +/- 24%; p less than 0.05). Plasma norepinephrine concentration was normal in the 4 patients without heart failure and was markedly elevated (range, 307-3,967 ng/l) in the patients with severe heart failure.(ABSTRACT TRUNCATED AT 250 WORDS) |
