[Patients with structural heart disease, syncope of unknown etiology and inducible ventricular arrhythmias treated with implantable defibrillators]

[Epicardial mapping of reentrant activation during ventricular fibrillation. An experimental study]

INTRODUCTION AND OBJECTIVES

High-resolution epicardial mapping was used in an experimental model to analyze reentrant activation during ventricular fibrillation.

METHODS

In 30 isolated Langendorff-perfused rabbit hearts, recordings were made of ventricular fibrillation activity using an epicardial multiple electrode. In the activation maps with reentrant activation patterns, determinations were made of the number of consecutive rotations, the maximum length of the central core, the area encompassed by the core and two electrodes surrounding it, and the cycle defined by reentrant activation.

RESULTS

Most of the activation maps analyzed showed complex patterns with two or more wave fronts that either collided or remained separated by functional block lines (514 maps, 86%). In 112 maps (19%) activation patterns compatible with epicardial breakthrough of the depolarization process were observed. Reentrant activity was recorded in 42 maps (7%) - the maximum number of consecutive rotations being 3 (mean = 1.3 +/- 0.5). The maximum length of the central core ranged from 3 to 7 mm (mean = 5 +/- 1 mm), while the area encompassed by the central core plus two electrodes surrounding it ranged from 35 to 55 mm2 (mean = 45 +/- 6 mm2). The reentrant cycle length (mean = 47 +/- 8 ms) showed a linear relation to the maximum length of the central core reentry (cycle = 4.52 x length + 24.6; r = 0.7; p < 0.0001).

CONCLUSIONS

a) Epicardial mapping allowed the identification of reentrant activation patterns during ventricular fibrillation in the experimental model used; b) the reentrant activity detected is infrequent and unstable, and c) a linear relation exists between the duration of the cycles defined by reentrant activity and the maximum length of central core reentry.

Arrhythmia recurrence in patients with a healed myocardial infarction who received an implantable defibrillator: analysis according to the clinical presentation

OBJECTIVES

The purpose of this study was to analyze the type of arrhythmia recurrence, based on stored electrograms, in patients with a healed myocardial infarction (MI) who received an implantable defibrillator.

BACKGROUND

Previous studies suggest that patients presenting with cardiac arrest (CA) tend to recur as ventricular fibrillation (VF), whereas those suffering sustained monomorphic ventricular tachycardia (SMVT) tend to recur as SMVT. However, these data have not been confirmed in a homogeneous population of patients with MI.

METHODS

A total of 88 patients was divided into three groups according to their clinical presentation: SMVT (n = 57), CA (n = 16) or syncope (n = 15).

RESULTS

There were no significant differences in clinical characteristics among groups. In the electrophysiologic study SMVT was induced in 93%, 94% and 80% of patients, respectively (p = NS). During the follow-up period, 52% of patients presented a total of 671 episodes of ventricular arrhythmia treated by the defibrillator. All recurrences were as SMVT except for one VF. There were 610 episodes of SMVT treated with antitachycardia pacing, with an effectiveness of 96%. A total of 61 episodes was treated initially with cardioversion. No differences in the probability of recurrence were observed among groups, although the statistical power was low (50%).

CONCLUSIONS

In patients with an old infarction and malignant ventricular arrhythmias, the majority of recurrences are due to SMVT independently of the clinical presentation (SMVT, CA or syncope) or the induced arrhythmia at the electrophysiologic study. The programming of an antitachycardia zone seems to be appropriate also for patients who present with CA or syncope.