Management of Ventricular Tachycardia Not Related To Myocardial Ischemia

Configuration of unipolar atrial electrograms during electrically induced atrial fibrillation in humans

BACKGROUND

During atrial fibrillation (AF), the atrium is activated by multiple wavelets that continuously change in size and direction. The aim of this study was to correlate the temporal variation in AF electrogram configuration with the varying spatial patterns of activation.

METHODS AND RESULTS

In a group of 25 Wolff-Parkinson-White patients undergoing cardiac surgery, the free wall of the right atrium was mapped (244 points) during electrically induced AF. The unipolar electrograms recorded during 4 seconds of AF were classified into four categories: (1) single deflections, (2) short-double potentials, (3) long-double potentials, and (4) fragmented potentials. The proportion of these four types of electrograms during AF was as follows: singles, 77 +/- 12%; short-doubles, 7 +/- 3%; long-doubles, 10 +/- 7%; and fragmented, 6 +/- 4%. Electrogram morphology was an indicator for rapid uniform conduction (single potentials; positive predictive value [PPV] of 0.96), collision (short-double potentials; PPV of 0.33), conduction block (long-double potentials; PPV of 0.84), and pivoting points or slow conduction (fragmented potentials; PPV of 0.87). In type I, II, and III AF, the proportion of long-double potentials was 4 +/- 2%, 12 +/- 3%, and 18 +/- 7% (P < .05); the proportion of fragmented complexes was 2 +/- 2%, 6 +/- 3%, and 10 +/- 4% (P < .05), respectively. During electrically induced and self-terminating episodes of AF, no preferential anatomic sites for double or fragmented potentials were found in the right atrium.

CONCLUSIONS

The morphology of single unipolar electrograms during AF reflects the occurrence of various specific patterns of conduction. This might be used to differentiate between different types of AF and to identify regions with structural conduction disturbances involved in perpetuation of chronic AF.

Treatment of presumed arrhythmogenic right ventricular dysplasia in an adolescent

Familial arrhythmogenic right ventricular dysplasia is a rare cardiomyopathy that is usually diagnosed on postmortem examination or on presentation with progressive congestive heart failure. We present a patient in whom an automatic implantable cardioverter-defibrillator was inserted prophylactically. A review of the condition and possible therapies is included.

Characterization of double potentials during ventricular tachycardia. Studies during transient entrainment

BACKGROUND

Double potentials have been recorded during reentrant tachycardias in animal models. Although they have also been recorded during ventricular tachycardia in humans, their meaning is uncertain.

METHODS AND RESULTS

We used transient entrainment as a method to help further understand the meaning of double potentials recorded during ventricular tachycardia in humans. Three patients with ventricular tachycardia (cycle lengths, 500, 450, and 290 msec) were studied. During transient entrainment of ventricular tachycardia (pacing cycle length, 470-260 msec), both double potential deflections were captured at the pacing cycle length. One deflection was captured with a short activation time, and the other deflection was captured with a long activation time. During ventricular pacing, the deflections were associated by the long rather than the short interdeflection interval. At termination of pacing, each double potential deflection was associated with separate but sequential QRS complexes, and each deflection maintained the same electrogram morphology at relatively "slow" overdrive pacing rates. The short interdeflection interval shortened further with faster pacing rates (to less than the ventricular refractory period), making it unlikely that both deflections of the double potential represent active depolarization of the same tissue. In two patients, at a critically rapid pacing rate, one of the double potential deflections changed morphology abruptly, associated with a shortened stimulus-to-double potential time interval (from 520 to 110 msec and from 530 to 240 msec, respectively), indicating a change in the direction of activation that caused that deflection. Interruption of ventricular tachycardia was associated with disappearance of the double potentials at the same recording site. The double potentials did not immediately bracket an area of slow conduction.

CONCLUSIONS

These data suggest that double potentials recorded only during ventricular tachycardia represent activation wave fronts on either side of an area of block within a reentrant circuit. Thus, double potentials recorded during ventricular tachycardia in these patients do not appear to represent slow conduction per se but rather appear to represent an area of block at the center of a reentrant circuit around which the reentrant wave front circulates.

Electrophysiologic assessment of antiarrhythmic drug efficacy for ventricular tachyarrhythmias associated with dilated cardiomyopathy

To determine the benefit of serial electrophysiologic drug testing in patients with ventricular tachyarrhythmias related to dilated cardiomyopathy, programmed ventricular stimulation was performed in 38 patients. In the baseline study, sustained ventricular tachycardia (VT) was induced in 18 patients, ventricular fibrillation in 7 and nonsustained VT in 13. The patients underwent a total of 84 trials of drug therapy (mean 2.3 +/- 1.4 trials/patient). Complete success (induction of fewer than 6 repetitive responses) was recorded in 19 trials and partial success (induction of at least 6 but no more than 15 repetitive responses) in 7. Potential proarrhythmic effects were observed in 9 trials. Overall, at least 1 successful regimen was identified for 20 patients (53%). During a mean follow-up of 21 +/- 13 months, there were no arrhythmia recurrences or episodes of sudden death among patients discharged with a drug regimen determined to be effective by serial drug testing. In comparison, among patients taking regimens that failed to prevent arrhythmia induction, there were 3 arrhythmia recurrences and 2 sudden deaths (p less than 0.05). Serial electrophysiologic drug testing provides an effective method of identifying successful medical therapy for patients with ventricular arrhythmia related to dilated cardiomyopathy.