The syndrome of normal electrocardiograms, accessory pathways and paroxysmal tachycardias

Tachycardias may be associated with the pre-excitation syndrome, a short PR interval or a prolonged QT interval. This report describes seven patients whose electrocardiograms (ECGs) did not reveal any of the above-named conditions. All of the patients presented with syncopal episodes, and the history of palpitations was elicited in five of the patients. His bundle electrogram studies in all of the patients showed an essentially unchanged AH interval with atrial pacing rates up to 180 beats/min. This can only be explained by a total bypass of the AV node. Two of the patients were also paced from the ventricle, and an unchanged pacing stimulus to A wave interval was observed. This signifies in these patients a functioning bypass pathway in the retrograde direction as well. Thus it would appear that pre-excitation cannot by eliminated as a diagnostic possibility even if the ECG is normal.

Hemodynamic effects of steroids in cardiac disease

The hemodynamic effects of intravenous methylprednisolone were documented by right heart catheterization in seven patients with an acute uncomplicated transmural myocardial infarction 1 to 9 days after the onset of symptoms. Intracardiac pressures, brachial artery pressure, and cardiac output were determined before and 1 hour after the termination of the methylprednisolone infusion. Two grams of methylprednisolone were infused over a 20 minute period. The brachial pressure rose from a mean of 82 to 90 mm. Hq (N.S.). The brachial artery mean pressure fell in the one patient with a 1-day-old infarction, and it rose in the six patients with an older infarction, from 83 to 94 mm. Hg (p less than 0.01). As the brachial artery pressure rose in one patient, chest pain and marked ST-segment elevation occurred which were relieved by nitroglycerin. This experience promoted us to terminate the steroid study. There was a nonsignificant increase in the cardiac index and wedge pressure. The raise in the brachial artery pressure with an infarction older than 1 day was an unexpected finding, since steroids are presumed to be vasodilating agents.

The effect of nitroglycerin on atrioventricular conduction in man

His bundle electrograms were performed on 10 patients with organic heart disease. Six patients had had a recent myocardial infarction. Recordings were made at various rates utilizing right atrial pacing. Nitroglycerin, 1/150 gr, was administered to all 10 subjects, and the P-A, A-H, H-Q and H-S intervals were determined before, and immediately after the disappearance of the sublingually administered nitroglycerin. A significant decrease in the A-H interval occurred with negligible effects on the P-A, H-Q and H-S intervals. At the atrial pacing rate of 100/min, the average A-H interval fell from the control value of 152 msec to 129 msec after the administration of nitroglycerin (p less than 0.02); at the pacing rate of 130/min, the A-H interval decreased from 194 to 133 msec (p less 0.05). Second degree heart block occurred at higher pacing rates in six patients after nitroglycerin administration as compared to the control value. The average postsuppression sinoatrial recovery time control value of 1,083 msec decreased to 906 msec after nitroglycerin administration (p less than 0.01). These findings demonstrate that nitroglycerin can improve conduction through the A-V node.