Abstract
<h3>To the Editor:—</h3> In the communication, "Electrical Pacemakers and Ventricular Arrhythmias" (<i>JAMA</i><b>190</b>:775 [Nov 23] 1964) the optimum rate of heart pacing by implanted pacemakers is discussed, and the suggestion is made that more rapid fixed rates than those originally recommended may be advisable. All of the discussion, however, concerns fixed-rate pacing, and no mention is made of variable-rate pacemakers such as the Cordis implantable pacers. These are triggered by the atrial impulses so that they are under autonomic control at rates above 52 per minute, and there is a built-in safety factor of automatic fixed-rate pacing if the atrial stimulus becomes inadequate or goes below 52 per minute. The patient is also protected against too rapid rates by a self-induced 2:1 or greater block in the pacer if the atrial impulses speed up. This appears to be a more physiological arrangement than that provided by fixed pacers at
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