We have described a new mutation in the desmoplakin gene that causes familial ARVD. These findings suggest that desmosomal proteins play an important role in the integrity and function of the myocardium. Dysfunction of these proteins can lead to the development of cardiomyopathies and arrhythmias.

The diagnosis and cure of paroxysmal supraventricular tachycardia or the Wolff-Parkinson-White syndrome during a single electrophysiologic test are feasible and practical and have a favorable risk-benefit ratio. This abbreviated therapeutic approach may eliminate the need for serial electropharmacologic testing, long-term drug therapy, antitachycardia pacemakers, and surgical ablation.

Ten consecutive patients with recurrent episodes of symptomatic, idiopathic, sustained monomorphic ventricular tachycardia (VT) originating in the right ventricle underwent an attempt at catheter ablation of the ventricular tachycardia. There were seven women and three men, with a mean age of 39±14 years (±SD). None of the patients had any evidence of structural heart disease. The VT had a left bundle branch block configuration and an inferior axis in each patient, and the mean cycle length was 313±75 msec. Based on the methods of induction of the VT and the response of the VT to verapamil, the VT mechanism was presumed to be reentry in six patients, triggered activity in three patients, and catecholamine-sensitive automaticity in one patient. Sites for ablation were guided by pace mapping, and an appropriate target site was identified in the right ventricular outflow tract in each patient. From one to three shocks of 100-360 J (mean total, 336±+195 J) were delivered from a defibrillator between the tip of the ablation catheter (cathode) and a patch electrode on the anterior chest (anode). An electrophysiology test 7-9 days after ablation demonstrated that VT was still inducible in only one patient, who was treated with amiodarone. One other patient had a recurrence of VT 3 weeks after ablation and was treated with verapamil. Eight of 10 patients were not treated with antiarrhythmic medications and have had no episodes of symptomatic VT during 15-68 months of follow-up (mean follow-up, 33-+-18 months). There were no acute or long-term complications. In conclusion, long-term success in preventing VT is achievable safely and in a high percentage of patients who have idiopathic right VT originating in the right ventricle. (Circulation 1990;82:2093-2099 Several studies have demonstrated that catheter ablation of ventricular tachycardia (VT) with electric shocks may be effective in preventing recurrences of VT.1-7 The majority of patients who have been the subjects of these studies have had structural heart disease; in most cases, the VT originated in the left ventricle. Among patients in whom VT originated in the right ventricle, the majority have had arrhythmogenic right ventricular dysplasia.1,2,5 Therefore, very little information has been available on the results of catheter ablation of idiopathic VT originating in the right ventricle.8The purpose of this study was to describe the long-term results of catheter ablation of idiopathic right VT in 10 patients who were followed for 15 months to 5.5 years after ablation.

Limited prospective data are available regarding the influence of pacemaker leads on tricuspid valve function. To examine the true incidence of these complications, 35 patients were prospectively examined by two-dimensional and Doppler echocardiography before and after implantation of either a permanent pacemaker or an automatic implantable cardioverter-defibrillator. Of the 35 patients imaged preoperatively, the amount of tricuspid regurgitation (TR) was judged as normal or trivial in 15 (43%), mild in 10 (29%), moderate in 8 (23%), and severe in 2 (6%). Following electrode implantation, TR was noted to be normal or trivial in 13 (38%), mild in 15 (48%), moderate in 6 (17%) and severe in 1 (3%). We conclude that implantation of permanent right ventricular electrodes is not usually associated with an acute worsening of tricuspid regurgitation in most patients.

Fifteen consecutive patients with drug-refractory, recurrent, sustained, monomorphic ventricular tachycardia and a history of remote myocardial infarction underwent catheter ablation of ventricular tachycardia. Shocks of 100 to 300 J were delivered to sites at which pacing during ventricular tachycardia resulted in concealed entrainment, in which the ventricular tachycardia accelerated to the pacing rate, there was a long stimulus to QRS interval and there was no change in the configuration of the QRS complex during pacing at several rates compared with the configuration during ventricular tachycardia, thus identifying a zone of slow conduction in the reentrant circuit. Concealed entrainment was demonstrated in nine (60%) of 15 patients, and the stimulus to QRS intervals were 90 to 400 ms. At sites of concealed entrainment, the endocardial activation time relative to the QRS complex during ventricular tachycardia ranged from -125 to +50 ms, the timing of the local electrogram relative to the QRS complex was the same during entrainment as during ventricular tachycardia and the pace map during sinus rhythm was discordant with that of the ventricular tachycardia in seven patients. In the six patients in whom a site of concealed entrainment could not be identified, the target site for ablation was selected on the basis of identification of an isolated mid-diastolic potential, activation mapping and pace mapping. The mean (+/- SD) cumulative number of joules delivered to the target site was 306 +/- 140. A successful long-term clinical outcome was achieved in 9 of the 15 patients (mean follow-up 20 +/- 7 months). The clinical success rate was the same whether the target site was selected on the basis of concealed entrainment (five of nine, 56%) or on the basis of the other mapping techniques (four of six, 67%). In conclusion, the responses to pacing suggest that sites at which there is concealed entrainment may be located within a zone of slow conduction in the ventricular tachycardia reentry circuit, although not necessarily in an area critical for the maintenance of reentry. The long-term clinical efficacy of catheter ablation targeted to sites of concealed entrainment is about 60%, similar to the results achieved when conventional mapping techniques are used.