QT Interval Revisited —Not Just the Matter of “Interval,” but “Dynamics, Variability and Morphology” Matter!—

Recently, the effects of QT interval prolongation have received more attention among clinicians, industry, and official regulatory agencies. Some have advocated the total elimination or discontinuing development of drugs which prolong the QT interval. In this review, we will give a brief overview of the pathophysiology and the dynamic variability and morphology of the QT interval. From the view point of arrhythmogenesis, QT interval prolongation with increased heterogeneity of ventricular repolarization is critical. The problem is how to detect such an abnormal repolarization. To detect heterogeneity, a new index should be developed and validated, and it must incorporate QT variability and morphology of the T wave. The heart rate correction of the QT interval is also an important issue, and disclosing conflict-corrected QT intervals depend on the formulae used. Not just QT interval prolongation is important; what also matters is the heterogeneity of ventricular repolarization

Manifestation of ST-Segment Elevation in Right Precordial Leads during Ischemia at a Right Ventricular Outflow Tract Area in a Patient with Brugada Syndrome

A 35-year-old man experienced chest pain and a subsequent syncope attack at during the night. Ventricular fibrillation (VF) was documented, which was successfully defibrillated. The ST-segment of his 12-lead electrocardiogram (ECG) showed day-by-day variation, sometimes showing spontaneous coved-type elevation in V1 and V2. He was diagnosed as having Brugada syndrome, and an implantable cardioverter defibrillator was implanted. A coronary angiography was performed. During the procedure, the catheter was selectively inserted to the right ventricular (RV) branch of the right coronary artery (RCA) whereupon the ST-segment in V1 and V2 elevated rapidly, manifesting a coved-type Brugada ECG. The main RCA angiogram revealed the conus branch running to the RV outflow tract area, indicating that the ST-segment elevation was due to ischemia of the RV outflow tract area by transient occlusion of conus branch. The findings indicate that some patients with Brugada syndrome are specifically sensitive to ischemia in the RV outflow tract area, leading to manifestation of the ST-segment elevation in precordial ECG leads