Acute functional consequences of left ventriculotomy

Background. Left ventriculotomies are sometimes used during intracardiac congenital defect repair. Acute changes in left ventricular function after longitudinal or apical ventriculotomy were assessed using dynamic pressure-dimensional data. Methods. Ultrasonic dimension transducers along the major, minor, and septal free wall axes and micromanometers were placed in 24 piglets. Pressure-volume data were collected during caval occlusions at baseline and 60 minutes after warm cardiopulmonary bypass alone or with longitudinal ventriculotomy or apical left ventriculotomy. Hemodynamics, contractility, and contraction geometry were analyzed. Results. Cardipulmonary bypass caused decreased compliance in all groups, with equally decreased preload and cardiac output. Heart rate increased, but ventriculotomy led to a significantly greater increase. Longitudinal ventriculotomy produced a greater loss of stroke volume and ejection fraction than apical ventriculotomy. Contractility assessed by the preload recruitable stroke work relationship showed no difference between groups; however, all groups showed a slight increase in unit myocardial power at 60 minutes. Axis fractional shortening revealed that the septal freewall is responsible for 50% of stroke volume and that this axis is significantly impaired after longitudinal ventriculotomy. Conclusion. Apical left ventriculotomy impairs the less important major axis only and is predicted to be better tolerated.