Divergent effects of intravenous dobutamine and nitroprusside on left atrial contribution to ventricular filling in dogs with chronic heart failure.
The left atrial (LA) contribution to left ventricular (LV) filling is often attenuated in patients with heart failure. It remains uncertain, however, whether therapy with positive inotropic agents or vasodilators improves or further impairs this maladaptation. In the present study, the effects of intravenous dobutamine and nitroprusside on the LA contribution to LV filling was examined in seven dogs with chronic heart failure produced by multiple sequential intracoronary microembolizations. Pulsed Doppler echocardiography was used to measure mitral inflow velocity before and after an intravenous infusion of dobutamine (4 micrograms/kg/min) and an intravenous infusion of nitroprusside (3 micrograms/kg/min). The percent LA contribution to LV filling was calculated as the ratio of the time-velocity integral of the LA component of mitral inflow velocity (Ai) to the time-velocity integral of total diastolic inflow velocity (Ti) times 100. Dobutamine increased LV filling pressure, LV end-diastolic wall stress, LV end-diastolic stiffness, and Ei, but had no effect on Ai or the percent LA contribution to filling (14% +/- 3% vs 12% +/- 2%) (p < 0.34). In contrast, nitroprusside decreased LV filling pressure, LV end-diastolic wall stress, and end-diastolic stiffness, and increased Ei, Ai, and the percent LA contribution to LV filling (12% +/- 2% vs 17% +/- 2%) (p < 0.01). The results indicate that dobutamine and nitroprusside have divergent effects on the LA contribution to LV filling. In dogs with chronic heart failure, dobutamine appears to impair LA contribution to the LV filling by augmenting LA workload, whereas nitroprusside appears to elicit greater LA contribution to LV filling by reducing the LA workload.
Kono
T
T
Department of Medicine, Henry Ford Heart and Vascular Institute, Detroit, MI.
Sabbah
H N
HN
Rosman
H
H
Shimoyama
H
H
Alam
M
M
Goldstein
S
S
D000818:Animals; D002908:Chronic Disease; D017023:Coronary Angiography; D003971:Diastole; D004280:Dobutamine / Q000494:pharmacology* / Q000627:therapeutic use; D004285:Dogs; D015150:Echocardiography, Doppler; D006325:Heart Atria / Q000187:drug effects*; D006333:Heart Failure / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000503:physiopathology; D006439:Hemodynamics / Q000187:drug effects; D007262:Infusions, Intravenous; D009599:Nitroprusside / Q000494:pharmacology* / Q000627:therapeutic use; D016277:Ventricular Function, Left / Q000187:drug effects*
D009599:Nitroprusside; D004280:Dobutamine