Based on similarity of electrocardiographic features, bidirectional ventricular 
tachycardia has been considered a variant of long QT syndrome. Genes causing 
long QT syndrome were used as candidate genes in 4 patients with bidirectional 
ventricular tachycardia. In 2 patients, we identified a common low penetrance 
HERG allele (R1047L) with an intermediate biophysical phenotype.