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Induced electrophysiological isolation of the myocardium prevents ventricular fibrillation
S D Moulopoulos1, D A Sideris, S T Toumanidis
1Department of Clinical Therapeutics, Medical School of Athens University, Greece.
Study Objective:
to investigate whether an encircling procedure without ventriculotomy, not involving the endocardium, may have a protective effect against ventricular fibrillation (VF), by achieving a physiological rather than anatomic entrenchment.
Design:
the occurrence of VF was tested by DC application within an area entrenched by a circular "dotted" line formed by LASER (Nd-Yag) point by point applications. The result was compared with that from similar DC applications before the successful LASER entrenchment or beyond the restricted area.
Subjects:
16 anaesthetized mongrel dogs, weights 14-20 kg were used.
Measurements And Results:
VF occurred 13/118 times by applying DC within the entrenched area and 86/114 times by applying the current outside this area or before the intervention (P less than 0.0005). The pacing threshold was significantly (P less than 0.001) increased within the circumscribed area (4.625 +/- 5.335 vs 0.859 +/- 0.947 mA). The maximal rate at which the ventricles could be driven by pacing at double threshold intensity was not significantly altered by the encircling procedure. Histological examination showed crater-like epicardial destruction with necrosis, loss of myocardial striation, haemorrhage, and polymorphonuclear infiltration, extending about 0.5 cm from the necrotic tissue. The subendocardial area was spared showing only hyperaemia, while the endocardium was intact.
Conclusions:
Encircling a small area by LASER point by point applications prevents the occurrence of VF when DC is applied within the restricted area, while permitting the conduction of paced beats. The size of the encircled area necessary to this effect is of importance, possibly reflecting the critical mass needed for the occurrence and maintenance of VF.