CLINICAL PROGRESS Paroxysmal Atrial Tachycardia with Block

THE digitalis drugs can produce nearly everv form of disturbed heart rhythmi. Thus far elinical attention has been directed to the venitricular effects. Digitalis-induced ventricular arrhythmias are therefore clearly catalogued and are recognized as of potentially grave signifieance. Recent studies indicate that certaiin atrial disorders are also imaniifestations of serious digitalis poisoning.1 Trhe prototype of these atrial arrhythmias is paroxysmal atrial tachyeardia with advanieed degrees of atrioventricular (A-V) block (referred to as PAT with block). This has been regarded as a hybrid disorder of rhythm exhibiting features of both atrial flutter and atrial tachyeardia. As in atrial flutter A-V block occurs either spontaneously or as a result of vagal stimulation. As in atrial tachyeardia the ectopic rate ranges from 150 to 250 per minute (fig. 1). A review of the literature suggests that PAT with block is anl unusual disorder of uncertain etiology. Somne of the leading cardiologists of our era have reported either isolated examples or small series of cases.2-10 The general view has been that PAT with block