Atypical Fast-Slow Atrioventricular Nodal Reentrant Tachycardia Incorporating a "Superior" Slow Pathway: A Distinct Supraventricular Tachyarrhythmia.

BACKGROUND: The existence of an atypical fast-slow (F/S) atrioventricular nodal reentrant tachycardia (AVNRT) including a superior (sup) pathway with slow conductive properties and an atrial exit near the His bundle has not been confirmed. METHODS AND RESULTS: We studied 6 women and 2 men (age, 74 ± 7 years) with sup-F/S-AVNRT who underwent successful radiofrequency ablation near the His bundle. Programmed ventricular stimulation induced retrograde conduction over a superior SP with an earliest atrial activation near the His bundle, a mean shortest spike-atrial interval of 378 ± 119 milliseconds, and decremental properties in all patients. sup-F/S-AVNRT was characterized by a long-RP interval; a retrograde atrial activation sequence during tachycardia identical to that over a sup-SP during ventricular pacing; ventriculoatrial dissociation during ventricular overdrive pacing of the tachycardia in 5 patients or atrioventricular block occurring during tachycardia in 3 patients, excluding atrioventricular reentrant tachycardia; termination of the tachycardia by ATP; and a V-A-V activation sequence immediately after ventricular induction or entrainment of the tachycardia, including dual atrial responses in 2 patients. Elimination or modification of retrograde conduction over the sup-SP by ablation near the right perinodal region or from the noncoronary cusp of Valsalva eliminated and confirmed the diagnosis of AVNRT in 4 patients each. CONCLUSIONS: sup-F/S-AVNRT is a distinct supraventricular tachycardia, incorporating an SP located above the Koch triangle as the retrograde limb, that can be eliminated by radiofrequency ablation.

KCNE3 T4A as the genetic basis of Brugada-pattern electrocardiogram.

BACKGROUND: Brugada syndrome (BrS) is genetically heterogeneous. In Japanese BrS patients, except for SCN5A and KCNE5, mutations in the responsible genes have not yet been identified, and therefore the genetic heterogeneity remains poorly elucidated. METHODS AND RESULTS: Forty consecutive patients with Brugada-pattern electrocardiogram (ECG) underwent comprehensive genetic analysis of BrS-causing genes including SCN5A, SCN1B, SCN3B, CACNA1C, CACNB2, KCNE3 and KCNE5. Besides identifying 8 SCN5A mutations in the present cohort, a KCNE3 T4A mutation was found in a 55-year-old male patient who had experienced several episodes of syncope. A head-up tilt test during passive tilt provoked both hypotension and bradycardia, followed by syncope. He was therefore diagnosed with neurally mediated syncope (NMS). To characterize the functional consequence of the mutant, electrophysiological experiments using whole-cell patch-clamp methods and computer simulations using human right ventricular wall model were carried out. It was found that KCNE3 T4A increased I(to) recapitulated by heterologously coexpressing Kv4.3+KChIP2b+KCNE3-wild type or KCNE3-T4A in CHO cells. CONCLUSIONS: A KCNE3 T4A mutation was identified in a Japanese patient presenting Brugada-pattern ECG and NMS. Its functional consequence was the gain of function of I(to), which could underlie the pathogenesis of Brugada-pattern ECG. The data provide novel insights into the genetic basis of Japanese BrS.

Compound and digenic heterozygosity in desmosome genes as a cause of arrhythmogenic right ventricular cardiomyopathy in Japanese patients.

BACKGROUND: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a hereditary disorder mostly caused by desmosome gene mutations. Recent comprehensive desmosome mutation analyses of Caucasian ARVC patients have revealed the presence of not only a single heterozygous mutation, but also compound and digenic heterozygosity. However, the genetic basis of Japanese ARVC remains poorly elucidated. METHODS AND RESULTS: The subjects were 7 definite and 1 possible ARVC probands (6 males, 16-76 years of age), and their family members. Genetic screening for major ARVC-causing genes (junction plakoglobin, desmoplakin, plakophilin-2 (PKP2), desmoglein-2 (DSG2), and desmocollin-2) was performed. We identified 3 cases of compound heterozygosities (Case 1: DSG2 S194L and DSG2 R292C; Case 2: PKP2 2489+1G>A and PKP2 D812N; Case 3: PKP2 M565R and PKP2 D812N) and 1 of digenic heterozygosity (Case 4: PKP2 1728_1729insGATG and DSG2 R292C) among the definite ARVC patients. All family members we investigated have remained asymptomatic. They carried, if any, only a single variant, indicating that the probands carry in trans compound heterozygosity. These results suggest that each of these variants alone may not be sufficient and second variants may be required to manifest overt ARVC in Japanese patients. CONCLUSIONS: Our comprehensive genetic analysis of desmosome genes identified 3 cases of compound heterozygosities in trans and 1 of digenic heterozygosity among 7 definite Japanese ARVC patients, providing novel insights into the genetic basis of Japanese ARVC.

A case of atrial tachycardia originating from pulmonary vein invaded by lung cancer.

A 59-year-old man during chemotherapy for squamous cell carcinoma of the lung, underwent catheter ablation of drug-refractory atrial tachycardia. Pulmonary venography and chest computed tomography revealed presence of stenotic, carcinomatous lesion of the left superior pulmonary vein. Excellent pace map and elimination of inducibility of atrial tachyarrhythmias after left pulmonary isolation suggested that the atrial tachycardia originated from the metastatic region.