Reentrant ventricular arrhythmias in the late myocardial infarction period. Interruption of reentrant circuits by cryothermal techniques.

Abstract

Both sustained and nonsustained ventricular tachycardias were reproducibly induced in dogs 3 to 5 days after ligation of the left anterior descending coronary artery. Isochronal maps of ventricular activation were constructed from close bipolar electrograms recorded from the entire epicardial surface and selected intramural sites by a computerized multiplexing technique. The electrophysiologic data were correlated with the anatomic characteristics of the infarction. The induced tachycardias were due to reentrant activation in the surviving epicardial layer overlying the infarction. Cooling or cryoablation was applied to localized epicardial sites along the reentrant circuit to reversibly or permanently interrupt reentrant activation. The reentrant circuit could be consistently interrupted when cooling or cryoablation was applied to the distal part of the common reentrant wave front proximal to the site of earliest reactivation. Localized cooling of the site of earliest reactivation usually failed to interrupt reentry because the common reentrant wave front reactivated other sites close to the original reactivation site. Before interruption of reentry, cooling resulted in characteristic changes in conduction of the reentrant wave front. The study (1) fulfills Mines' criteria that circus movement reentry is the mechanism of the induced rhythms in this canine experimental model and (2) identifies the critical site along the reentrant circuit at which cryothermal ablation (or surgical interruption) of reentrant activation could be successfully accomplished.Circulation 68, No. 3, 644-656, 1983. WE HAVE SHOWN that ventricular arrhythmias induced by programmed stimulation in dogs 1 to 5 days after infarction are due to reentrant circuits located in the surviving, although electrophysiologically abnormal, thin epicardial layer overlying the infarction. 1 2 These electrophysiologic-anatomic correlative studies provide strong evidence for circus movement reentry. However, to establish the mechanism as reentrant, the reentrant circuit should be interrupted at one point to produce termination of reentrant activation.3 The present study was conducted to fulfill Mines' criteria for proving the presence of circulating excitation and to identify the critical site along the reentrant circuit at which interruption of reentrant activation could be successfully accomplished. For MethodsIn 18 mongrel dogs weighing 15 to 20 kg the left anterior descending coronary artery was ligated just distal to the anterior septal branch. Details of the surgical technique have been described.4 The dogs were reanesthetized with sodium pentobarbital (30 mg/kg iv) 3 to 5 days after coronary artery ligation and received supplemental doses as required. Each animal was ventilated with room air through an endotracheal tube with a Harvard positive pressure pump, and in each a jugular vein was cannulated for the administration of fluids. Electrocardiographic lead II and femoral blood pressure were continuously monitored on an Electronics for...

Characteristics and identification of sites of chagasic ventricular tachycardia by endocardial mapping

“…Later, El-Sherif et al 26 showed that SVT could be consistently interrupted after slowness and blockade of the conduction, when cryoablation was performed in the distal part of the common via of the circuit proximal to the site of the earliest activity. This showed the need to identify an ideal site in the reentrant circuit in order to achieve effectiveness of the ablation procedure.…”

Treatment of ventricular tachycardia by transcatheter radiofrequency ablation in patients with ischemic heart disease.

“…Most of the models of reentry postulate the presence of a zone of unidirectional block and slow conduction, and participation of such pathways in VT mechanism has been convincingly demonstrated in animal models of experimental myocardial infarction.22-24 Experimental data suggest that proximal segments of such pathways are the optimal sites for successful ablation. 22 The hallmark of such pathways in VT of ischemic heart disease is believed to be the low-amplitude, isolated, middiastolic to early diastolic signals recorded during VT, which can be reset or entrained simultaneously with VT in the clinical electrophysiological laboratory.13'6-'8 Such recording sites have been described as effective catheter ablation sites in previous reports.13 "16"17 In our series, the middiastolic potentials could be recorded in the majority, and their presence at the ablation site predicted VT interruption during RF current application but did not guarantee long-term success. Thus, the presence of the middiastolic potentials may be necessary but not sufficient for durable effect, and additional criteria may have to be met for long-term success of RF ablation.…”

Programmed electrical stimulation at potential ventricular reentry circuit sites. Comparison of observations in humans with predictions from computer simulations.

“…We considered only two reentry circuit configurations: the figure-eight type of circuit that has been well characterized in animal models6, [21][22][23][24] 25 However, the existence of such areas in human myocardial scars is speculative at present. We also assumed that the figure-eight reentry circuit was located in the border of a myocardial scar with one loop of the circuit (the loop from sites 1-3 in Figure 1) relatively protected from the surrounding myocardium by the arcs of block and the common central pathway of slow conduction.…”