A Steam Pop Detected by Intracardiac Echocardiography During Catheter Ablation of the Left Ventricular Papillary Muscle.

A 60-year-old female with premature ventricular contractions (PVCs) originating from the bottom of the posteromedial papillary muscle of the left ventricle underwent radiofrequency catheter ablation (RFCA) using an irrigated-tip catheter. During ablation of the PVCs, a loud steam pop was observed. Intracardiac echocardiography (ICE) revealed a growing, hyperechogenic intramyocardial microbubble formation around the catheter tip. The formation disappeared slowly and completely, leaving an endocardial laceration without pericardial effusion. ICE imaging is valuable during a difficult RFCA procedure, because ICE reveals the exact anatomical position of the catheter and thus allows rapid evaluation of the occurrence of steam popping and any possible subsequent complication.

Quantitative analysis of PKP2 and neighbouring genes in a patient with arrhythmogenic right ventricular cardiomyopathy caused by heterozygous PKP2 deletion.

AIMS: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a disease mainly caused by desmosome gene mutations. The genetic culprit, however, remains elusive in ∼50% of ARVC patients. One of the reasons for missing genetic abnormalities is the difficulty in detecting large deletions/duplications, which are called as copy number variation (CNV) by the Sanger sequencing method. This study aimed to identify CNVs in PKP2 and a part of other desmosome genes in ARVC patients. METHODS AND RESULTS: The study cohort consisted of 71 ARVC probands who were diagnosed as definite or borderline cases based on 2010 Task Force Criteria. Among them, 32 (45%) carried at least one mutation in desmosome genes detected by the Sanger method. Using the multiplex ligation-dependent probe amplification method, we identified a male proband (1.4%) with a complete deletion of all PKP2 coding exons. He was 31 years old and showed exercise-induced sustained ventricular tachycardia with superior axis and left bundle-branch block pattern. His cardiac magnetic resonance imaging and computed tomography showed right ventricular dilatation and reduced ejection fraction. His 12-lead electrocardiogram showed T-wave inversion in V1-V3, and late potentials were positive, indicating definite ARVC. To confirm the precise location of the deletion, we performed relative quantitative PCR. We found complete deletion of both SYT10 and ALG10 located in 3' of PKP2; the total deletion size was at least 1.23 Mb. CONCLUSION: Screening for CNVs in desmosome genes is useful to identify the genetic basis of disease in clinically suspected ARVC patients.

The effects of pure potassium channel blocker nifekalant and sodium channel blocker mexiletine on malignant ventricular tachyarrhythmias.

BACKGROUND: Patients with repetitive ventricular tachyarrhythmias - so-called electrical storm - frequently require antiarrhythmic drugs. Amiodarone is widely used for the treatment of electrical storm but is ineffective in some patients. Therefore, we investigated the efficacy of stepwise administration of nifekalant, a pure potassium channel blocker, and mexiletine for electrical storm. METHODS: This study included 44 patients with repetitive ventricular tachyarrhythmias who received stepwise therapy with nifekalant and mexiletine for electrical storm. Nifekalant was initially administered, and mexiletine was subsequently added if nifekalant failed to control ventricular tachyarrhythmias. RESULTS: Nifekalant completely suppressed recurrences of ventricular arrhythmias in 28 patients (64%), including 6 patients in whom oral amiodarone failed to control arrhythmias. In 9 of 16 patients in whom nifekalant was partially effective but failed to suppress ventricular arrhythmias, mexiletine was added. The addition of mexiletine prevented recurrences of ventricular tachyarrhythmias in 5 of these 9 patients (56%). There was no death associated with electrical storm. In total, the stepwise treatment with nifekalant and mexiletine was effective in preventing ventricular tachyarrhythmias in 33 of 44 patients (75%). There was no difference in cycle length of the ventricular tachycardia, QRS interval, QT interval, or left ventricular ejection fraction between patients who responded to antiarrhythmic drugs and those who did not. During follow-up, 8 patients had repetitive ventricular tachyarrhythmia recurrences, and the stepwise treatment was effective in 6 of these 8 patients (75%). CONCLUSIONS: The stepwise treatment with nifekalant and mexiletine was highly effective in the suppression of electrical storm.