To the Editor.— We read with interest the article entitled, "Refractory Supraventricular Arrhythmias in the Elderly: Treatment with Permanent Demand Pacing and Cardiac Drugs" (215:589-594, 1971). In their synopsis-abstract, Beller et al indicated that "recurrent episodes of bradycardia and asystole have been totally eliminated and supraventricular tachycardia has not recurred as long as the patients have continued their medication." It is absolutely impossible to make a statement of this nature without utilizing dynamic electrocardiography (Holter) as an objective method for evaluating the presence or absence of atrial or ventricular arrhythmias or both. The standard resting ECG only records between 60 and 100 cardiac cycles, whereas a ten-hour dynamic ECG may record as many as 50,000 to 60,000 cardiac cycles. We have performed over 1,700 ten-hour dynamic ECGs and have detected numerous episodes of intermittent pacemaker malfunction which had not been detected by ordinary clinical means since the patients were usually