The Journal of Thoracic and Cardiovascular Surgery, Vol 87, 862-869, Copyright © 1984 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Hemodynamic effect of isoprenaline and dobutamine immediately after correction of tetralogy of Fallot. Relative importance of inotropic and chronotropic action in supporting cardiac output
C Jaccard, M Berner, JC Rouge, I Oberhansli and B Friedli
In order to compare the effect of isoprenaline and dobutamine immediately
after correction of tetralogy of Fallot, 12 randomly selected patients were
studied postoperatively. Left ventricular end- diastolic volume, measured
preoperatively by means of left ventricular angiograms in eight patients,
was decreased to a mean value of 58.6 +/- 5.5 ml/m2 (mean +/- standard
error of the mean). Postoperatively, cardiac output was measured by
thermodilution before, during, and after infusion of increasing doses of
isoprenaline (0.05, 0.1, and 0.2 micrograms/kg/min) and dobutamine (2.5, 5,
and 10 micrograms/kg/min) successively given in each patient.
Simultaneously, central venous, left atrial, pulmonary arterial, and
systemic arterial pressures were recorded. Cardiac index increased
significantly in response to all three doses of isoprenaline. Dobutamine
produced only a small increase which was not statistically significant.
Stroke volume index did not vary significantly with either drug.
Consequently, cardiac index was directly related to heart rate. Preload of
the left ventricle as well as afterload was significantly reduced (p less
than 0.01 and p less than 0.05, respectively) by isoprenaline but not by
dobutamine. An increase in left ventricular work index per minute was found
with both drugs; however, only with isoprenaline was the increased work
accompanied by a significant increase in cardiac index. We conclude that
patients with tetralogy of Fallot usually have a small left ventricle
which, immediately after correction, reacts to catecholamines by only an
insignificant increase in stroke volume index. Consequently, isoprenaline
is more effective than dobutamine in raising cardiac index due to the
increase in heart rate. Moreover, it decreases systemic vascular
resistances and obviates the need for administration of a vasodilator.