Encircling endocardial ventriculotomy for refractory ischemic ventricular tachycardia. II. Effects on regional myocardial blood flow

Ungerleider, R.M.; Holman, W.L.; Stanley, T.E.; Lofland, G.K.; Williams, J.M.; Smith, P.K.; Quick, G.; Cox, J.L.

Journal of Thoracic and Cardiovascular Surgery 83(6): 850-856


ISSN/ISBN: 0022-5223
PMID: 7087511
Accession: 005355662

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Previous experimental studies of the encircling endocardial ventriculotomy (EEV) have shown a significant alteration of normal local electrical activity within the encompassed region. Although this procedure may result in isolation of ventricular arrhythmias, the data are more suggestive of a less specific effect on regional myocardial blood flow. The effects of the EEV on local myocardial blood flow was examined using the radioactive tracer microsphere technique in 10 dogs. Flows were determined before and after an EEV with the animals on cardiopulmonary bypass at controlled perfusion pressures, temperatures and heart rates. Blood flow was studied as subepicardial and subendocardial levels inside, outside and bordering the EEV. Prior to performance of the EEV, subepicardial blood flow in the left ventricular myocardium ranged from 0.81 .+-. 0.07 to 0.89 .+-. 0.08 ml/g per min. Subendocardial flows ranged from 0.80 .+-. 0.07 to 0.91 .+-. 0.09 ml/g per min. There was no significant difference between any of the flows across each respective layer of myocardium. Following the EEV procedure, blood flow to the subendocardium within the EEV fell to 0.33 .+-. 0.07 ml/g per min, while flow to the subendocardium of the normal regions of the same hearts actually increased to 1.21 .+-. 0.23 ml/g per min. Similar changes occurred at subepicardial levels, with flow at the center of the EEV falling to 0.66 .+-. 0.10 ml/g per min despite a tendency for normal subepicardial flow to increase to 1.78 .+-. 0.24 ml/g per min. Superimposed ischemia to the EEV-encompassed myocardium, created by occlusion of the distal left anterior descending coronary artery (LAD), accentuated this abnormality by demonstrating that the region continues to receive some flow from epicardially based coronary vessels. The EEV decreases regional blood flow to the encompassed myocardium and suggests that myocardial ischemia may be responsible for ablation of the delicate re-entrant mechanisms that sustain ventricular tachyarrhythmias.