Evolution of epicardial R wave voltage following experimental coronary artery occlusion: effects of hyaluronidase

The goals of this investigation were: 1) to examine the pattern of evolution of epicardial R wave voltage during the 24 h after experimental coronary artery occlusion; and 2) to determine whether hyaluronidase, an agent shown previously to reduce myocardial ischaemic injury, alters this evolution. Coronary artery occlusion was performed in 36 dogs. In the control dogs, the average R wave voltage (R) recorded over the ischaemic myocardium increased by 7.6 +/- 0.8 mV (P less than 0.001) from before to 15 min after coronary artery occlusion, then gradually returned to baseline over the ensuing 4 h. Subsequently, R wave voltage continued to fall, and 24 h after occlusion, R was 17.8 +/- 1.8 mV (P less than 0.001) less than before occlusion. In the hyaluronidase-treated dogs (500 NF units . kg-1), R recorded over the ischaemic myocardium increased similarly to the controls before hyaluronidase administration. However, in contrast to the control dogs, the administration of hyaluronidase 20 min after occlusion caused R to return to baseline over the ensuing 40 min and 24 h after occlusion, the treated animals lost significantly less R wave voltage than the controls (P less than 0.001).