The Journal of Thoracic and Cardiovascular Surgery, Vol 83, 850-856, Copyright © 1982 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Encircling endocardial ventriculotomy for refractory ischemic ventricular tachycardia. II. Effects on regional myocardial blood flow
RM Ungerleider, WL Holman, TE Stanley 3d, GK Lofland, JM Williams, PK Smith, G Quick and JL Cox
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. This study examines
the effect of EEV on local myocardial blood flow 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
at 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/gm/min. Subendocardial flows ranged from 0.80 +/- 0.07 to 0.91 +/- 0.09
ml/gm/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/gm/min, while flow to the subendocardium of the normal regions of the
same hearts actually increased to 1.21 +/- 0.23 ml/gm/min. Similar changes
occurred at subepicardial levels, with flow at the center of the EEV
falling to 0.66 +/- 0.10 ml/gm/min despite a tendency for normal
subepicardial flow to increase to 1.78 +/- 0.24 ml/gm/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 data from this study show
that the EEV decreased 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.
