THE IMPORTANCE of paroxysmal atrial tachycardia with latent block in the early diagnosis of digitalis toxicity has not been sufficiently emphasized. The arrhythmia is identified by an alteration in P-wave contour and increase in rate, but differs from paroxysmal atrial tachycardia with overt block in that the P-R interval is normal and atrioventricular (AV) block is induced only by carotid sinus pressure. This arrhythmia was originally described by Lown and Levine.1,p 87 Two cases illustrating this problem are presented below.
Report of Cases
—A 47-year-old white man was admitted to the Boston City Hospital on Dec 7, 1964, with abdominal pain. One year previously, a pelvic exenteration with sigmoid colostomy and ileal loop bladder had been done for carcinoma of the rectum. There was no previous history of cardiac illness.Physical examination revealed signs of peritonitis and intestinal obstruction. The electrocardiogram was within normal limits aside from