Preliminary assessment of very low calorie diets by conventional and signal-averaged electrocardiography.

Fatalities accompanying the use of very low calorie diets have been attributed to cardiac arrhythmias, which may have been associated with myocardial catabolism and hypokalemia. Delayed activation of damaged regions of myocardium may result in low amplitude potentials late in the QRS complex which have been associated with sustained ventricular tachycardia. We used the techniques of routine electrocardiography, signal averaging of the surface electrocardiogram and ambulatory electrocardiographic (Holter) monitoring to evaluate a group of 11 obese men (116 +/- 14 kg) who consumed a potassium-supplemented 660 kcal/day (2763 kJ/day) milk-based liquid diet for 95 +/- 14 days. Electrocardiographic measurements were made before beginning the diet, during the final week on the diet, and after refeeding. Corrected QT interval, QRS voltage and duration, absence of signal-averaged late potentials and ventricular ectopy during 24 h Holter monitoring during the diet and refeeding did not differ from baseline determinations at any point in the obese subjects. In this study, which involved only 11 subjects, neither standard electrocardiographic techniques nor a newer signal-averaging technique revealed any electrocardiographic changes from the diet. A very large population would have to be studied to evaluate the usefulness of these techniques in predicting myocardial damage serious enough to cause arrhythmias. Until such studies are available, the safety of such diets remains unknown.