The Journal of Thoracic and Cardiovascular Surgery, Vol 71, 195-206, Copyright © 1976 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Functional reductions in left ventricular volume. Minimum chamber size consonant with effective hemodynamic performance
AJ Liedtke, HC Hughes and R Zelis
A heart model in dogs was developed to evaluate quantitatively the extent
to which left ventricular chamber size could be reduced and yet retain
residual mechanical function to perform adequately as a pump. In 9 animals
placed on right heart bypass perfusion to control systemic flows; left
ventricular performance was estimated from high-fidelity left ventricular
pressure and aortic flowmeter recordings and from lateral plane left
ventricular angiograms. Studies were made during unrestricted left
ventricular filling at varying cardiac outputs and with inflation of a
balloon in the left ventricular cavity at a physiological cardiac output.
As compared with control data (cardiac output 1.4 L. per minute), balloon
inflation to 18.7 ml. caused an increase in total left ventricular
end-diastolic volume (from 35.4 to 44.3 ml., p less than 0.001) and left
atrial pressure (from 7.8 to 21.2 mm. Hg; p less than 0.001); it also
caused a reduction in left ventricular stroke work (from 12.5 to 8.1
Gm.-M., P LESS THAN 0.005) ANd max. dp/dt (from 2,487 to 1,320 mm. Hg per
second, p less than 0.05). Importantly, left ventricular stroke volume was
unchanged. When compared with preload augmentation (with the balloon
deflated), the magnitude of depression of cardiac performance caused by
balloon inflation was more fully appreciated (left ventricular stroke work,
max. dp/dt, and ejection fraction reduced 69, 61, and 45 per cent,
respectively). Even so, with appropriate compensations, principally by the
Frank-Starling mechanism, up to 42 per cent of the left ventricular cavity
volume could be functionally eliminated with retention of adequate
mechanical performance. Such data may have implications regarding the
extent of resections possible in patients undergoing surgery for left
ventricular aneurysm.
