Reduction of myocardial infarct size: comparison between left atrial and left ventricular bypass.

A controlled study was undertaken to quantitate and compare the effect of left ventricular bypass (LVB) and left atrial bypass (LAB on left ventricular infarct volume (LVIV). After baseline studies, the left anterior descending coronary artery in each of 30 mongrel dogs was ligated 1-1.5 cm from its origin. After baseline ischemic studies, control dogs (group 1--10 dogs), LAB dogs (group 2--10 dogs), and LVB dogs (group 3--10 dogs) were monitored for four hours. Final infarct size was determined by the nitroblue tetrazolium staining technique. Heart rate, mean arterial pressure, and total systemic flow (TSF) showed no significant difference between control and left heart bypass groups. In group 1, the LVIV was 27.7 +/- 6.5 g/100 g left ventricle (LV). In group 2, left heart bypass (LHB) flow was 90 +/- 4% of TSF. The pressure time index (PTI) was 2845 +/- 52 mm Hg-sec/min. The PTI demonstrated no significant difference from cntrols. In group 2, LVIV was 22.5 +/- 6.0 g/100 g LV. LVIV was reduced 18.8% from controls (p less than 0.08). In group 2, LHB was complete. Left ventricular decompression (group 3) resulted in a PTI of 328 +/- 76 mm Hg-sec/min. The PTI was significantly different (p less than 0.001) from groups 1 and 2. The LVIV was 12.6 +/- 5.1 g/100 g LV. LVIV was reduced 54.5% from controls (p less than 0.001) and 44.0% from group 2 (p less than 0.001). These results suggest that LVB may be useful, not only in supporting the circulation in the patient with myocardial infarct and cardiogenic shock, but also in limiting infarct size.