No abstract

No abstract

Long QT syndrome is a congenital disorder that presents with a defective cardiac ion channel and is either associated with prolonged action potential or, more commonly, known as an acquired form in which "torsades de pointes" type arrhythmias specifically occur after secondary causes. We report a case of a novel HERG mutation (A490T) that caused a bradycardia-associated form of long QT syndrome. A 27-year-old woman exhibited recurrent syncope due to torsades de pointes associated with a disturbance of the cardiac conduction system. By using polymerase chain reaction and single strand conformational polymorphism analyses, we identified a heterozygous single nucleotide substitution of HERG (G to A at nt 1468). This mutational change was not present in 140 Japanese control individuals. Electrophysiological assays for the A490T mutant HERG channel were conducted in the heterologous expression system with COS7 cells. The mutant channel was found to reconstitute functional channel currents, suggesting the homomeric mutant channel was functional. The mutation did not change the properties of the activation gate and inward rectification, however the current density of this mutant channel was small compared with that of wild type HERG. Taken together, this mutant may cause subtle changes in HERG channel functions (I(Kr)) in vivo. In this case, genetic background and unexpected bradycardia may have contributed to the development of long QT syndrome.

A 51‐year‐old male with dextrocardia and situs inversus underwent catheter ablation for paroxysmal atrial fibrillation. Because the procedure through the trans‐septal approach was impossible due to the inferior vena cava continuity with azygos vein, we performed pulmonary vein isolation using magnetic navigation system through the retrograde trans‐aortic approach. Superior and inferior left‐sided and superior right‐sided pulmonary veins could be isolated which was confirmed by the ablation catheter. The patient was free from atrial fibrillation episode at the 12 months follow‐up except only one palpitation episode lasting nearly 12 hours at 9 months after the ablation.