The goal of this investigation was to determine whether increases in R wave voltage shortly after coronary artery occlusion can be used to assess the severity of myocardial ischemic injury. Accordingly, the left anterior descending coronary artery was occluded in 16 open-chest, anesthetized dogs. Epicardial electrograms were recorded from 8-12 sites on the anterior surface of the left ventricle before and 15 minutes after coronary artery occlusion. Regional myocardial blood flow was determined 15 minutes after occlusion (RMBF15min) by the microsphere technique. After 24 hours, the dogs were sacrificed, the hearts excised, and 6-8 transmural specimens obtained for determination of RMBF15min and creatine kinase activity (CK24h). In all dogs, the increase in R wave voltage from before to 15 min after occlusion (ΔR15min) correlated well with RMBF15min [ΔR15min (mV)=17.0-0.2 RMBF (% normal): n=79 specimens from 16 dogs, r=-0.79]. Twenty minutes after coronary artery occlusion, the dogs were randomized to untreated and hyaluronidase-treated groups. To establish the predictive value of ΔR15min on myocardial necrosis, the relationship between ΔR15min in the ischemic sites and CK24h was evaluated in the untreated group (8 dogs). It was: [CK24h (IU/mg prot) = 19.3-0.54 ΔR15min (mV); n=30 specimens from 8 dogs, r=-0.75]. In the hyaluronidase-treated group (which received 500 N.F. units/kg intravenously as a bolus 20 min after occlusion) the same degree of increase in R wave voltage 15 minutes after occlusion (and, therefore, prior to hyaluronidase administration) resulted in less CK depression 24 hours later (p<0.01). Thus, the increase in R wave voltage from before to 15 minutes after coronary artery occlusion correlated well with RMBF at the same time and predicted accurately necrosis 24 hours later. Moreover, these early changes in R wave voltage may be used to assess the effect of interventions purported to limit infarct size.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine