Effects of acute incremental volume overload on cardiac chamber size, function, and the pulmonary circulation: Analysis by digital intravenous angiography

Abstract

To assess the effects of acute incremental volume overload on cardiac size, function, and the pulmonary circulation, we studied six anesthetized dogs using intravenous digital angiography. Aortocaval (AC) fistulas were placed in four dogs, and fistulas in both a carotid and iliac artery were placed in two dogs. Data were obtained at four points: (1) control stage; (2) partial shunt (PS, where either AC partially open or iliac fistula was open and carotid fistula was closed); (3) full shunt (FS, AC shunt open or both iliac and carotid shunts open); and (4) control stage 2. Little change in heart rate (HR) or arterial pressure occurred. With FS, both mean pulmonary artery and wedge pressures increased ( p < 0.05); however, systemic and pulmonary vascular resistances declined. Cardiac output rose (1.54 ± 0.42 L/min at control) to 2.44 ± 0.84 L/min at PC ( p < 0.05 vs control) and to 3.13 ± 0.89 L/min at full shunt ( p < 0.01 vs control). Both left (0.40 ± 0.09 to 0.55 ± 0.10 to 0.66 ± 0.10, p < 0.05 and p < 0.01 vs control, respectively) and right (0.34 ± 0.10 to 0.40 ± 0.10 to 0.51 ± 0.09, the latter p < 0.01 vs control) ventricular ejection fractions rose, as did left (30.7 ± 13 ml to 35.1 ± 13 ml to 37.8 ± 13 ml, the latter p < 0.05 vs control) and right (37.4 ± 6.1 ml to 44.2 ± 16.6 ml to 51.4 ± 17 ml, the latter p < 0.01 vs control) ventricular end-diastolic volumes. Atrial volume (determined at ventricular end-systole) also increased (9.4 ± 3.6 ml to 11 ± 3.5 ml to 12.9 ± 4.3 ml, the latter p < 0.05 vs control). These increases in cardiac function and size occurred in association with a shortening of pulmonary transit time (5.4 ± 0.8 to 3.5 ± 0.7 seconds to 2.9 ± 0.5 seconds, the latter two p < 0.05 and p < 0.01 vs control, respectively), with no significant change in pulmonary blood volume. We conclude that acute volume overload produces cardiac chamber dilatation, along with increases in systolic function. Both pulmonary and systemic vascular resistance declined, and the transit time in the pulmonary circulation shortened. Digital intravenous ventriculography is a useful technique for the analysis of the central circulation during acute hemodynamic manipulations.