Mechanism of action of hyaluronidase in decreasing myocardial ischemia post coronary occlusion in the isolated perfused rabbit heart

The influence of hyaluronidase (H) on subacute experimental myocardial ischemia was studied in isolated perfused rabbit hearts. Changes in ischemic area were assessed by epicardial nicotinamide adenine dinucleotide (NADH) fluorescence photography, an intrinsic high-resolution display of myocardial ischemia. Computerized determination of ischemic area was made from standardized photographs. Hyaluronidase was begun 20 minutes after coronary artery occlusion at 4 units/ml perfusate. NADH fluorophotographs were taken at 10-minute intervals up to 60 minutes of ischemia. Coronary sinus oxygen tension (P csO 2), myocardial oxygen consumption (MV̇O 2), and coronary flow were determined. After 70 minutes, the hearts were perfused with rhodamine solution to identify areas of myocardial perfusion. In 13 H-treated hearts 54.3% ± 3.7% (mean ± SEM) of the nonperfused area (rhodamine stained) was ischemic (NADH fluorescent). In 14 untreated hearts 79.8% ± 3.2% of the nonperfused area was ischemic ( p < 0.0001) and the ischemic areas were uniform. The distance between perfused and ischemic tissue was 952 ± 78 μm in the H hearts and 504 ± 35 μm in the untreated hearts ( p < 0.0001). In the H treated hearts P csO 2 increased to 155% of the post-ligation control while it decreased to 79% in the untreated hearts ( p < 0.0001). MV̇O 2 decreased in the H-treated hearts to 62%; the untreated hearts had no further change. In the H-treated hearts, coronary flow increased to 146% of the post-ligation control while it fell to 91% in the untreated group ( p < 0.0001). We conclude that H increases coronary flow while decreasing MV̇O 2 during subacute ischemia. In H-treated hearts, significant amounts of myocardium remain normoxic within the nonperfused areas, and may potentially be salvaged after prolonged myocardial ischemia.