Very low calorie diets and pre-fasting prolonged QT interval. A hidden potential danger.

The association of torsade de pointes and a prolonged electrocardiographic QT interval is well described. A prolonged QT interval may be congenital or acquired in several ways--by the use of anti-arrhythmic agents exemplified by quinidine, by the presence of hypocalcaemia or hypokalaemia, by the use of psychotropic drugs, and by the presence of intrinsic cardiac disease or bradycardias. Possibly less well appreciated is the potential for drastic weight loss to prolong the QT interval, as the present case report illustrates. A young woman weighing 244 pounds lost 24 pounds in two weeks with a consequent prolongation of QTc interval from pre-diet value of 0.57 seconds to 0.72 seconds at admission, when severely symptomatic paroxysms of torsade de pointes were recorded. Successful therapy with lignocaine and prompt re-feeding suppressed the arrhythmia and, three days later, the QTc was reduced to almost its pre-diet state. A (UK) DHSS report offers guidelines in the use of very low calorie diets. This case suggests that a pre-diet electrocardiogram should be carefully assessed for QT prolongation before initiation of dieting to achieve serious weight loss.