Simulated left ventricular aneurysm and aneurysm repair in swine. Patch reconstruction of left ventricular aneurysm may be superior to linear closure, but this hypothesis has not been tested experimentally. Accordingly, six anesthetized domestic pigs were instrumented to measure regional left ventricular wall thickening, stroke volume, systolic left ventricular pressure, and myocardial oxygen consumption. With total bypass and cardioplegia, a 6 by 8 cm Dacron patch was inserted into the anteroapical left ventricle. Simulations were as follows: left ventricular aneurysm, patch open; patch reconstruction, 50% patch plication; standard repair, ventriculotomy edges approximated. Global function, from stroke work (stroke volume x integral of left ventricular pressure)-left ventricular end-diastolic pressure curves, was depressed in all three simulations compared with control. A tendency for stroke work to be greater for standard repair than for left ventricular aneurysm and patch reconstruction at higher preloads was not statistically significant. Mechanical efficiency, from stroke work/myocardial oxygen consumption (joules per milliliter oxygen per beat), was 2.43 +/- 0.52 (mean +/- standard error of the mean) (control), 2.22 +/- 0.94 (standard repair), 1.27 +/- 0.39 (patch reconstruction), and 1.09 +/- 0.37 (left ventricular aneurysm) (no significant differences). Regional work was calculated as regional left ventricular wall thickening x integral of left ventricular pressure. The slope of the regional work-end-diastolic wall thickness relation decreased in the posterior wall 14.0 +/- 2.9 (control) versus 8.4 +/- 2.0 (left ventricular aneurysm), 6.9 +/- 1.4 (patch reconstruction), and 7.4 +/- 1.4 (standard repair) (p less than 0.05). In the anterior wall, contractility did not change significantly (7.4 +/- 1.2, control; 7.8 +/- 2.7, left ventricular aneurysm; 5.0 +/- 0.4, patch reconstruction; and 5.3 +/- 0.4, standard repair). Decreased end-diastolic wall thinning anteriorly suggested tethering. These results in the normal left ventricle suggest that patch ventriculoplasty is of no greater benefit than linear repair. Either repair may impede function of adjacent myocardium through restriction of regional diastolic lengthening. 