Echocardiographic Assessment of Left Ventricular Outflow Width in the Selection of Mitral Valve Prosthesis

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Abstract
The effect of digitalis in patients with sinoatrial node dysfunction was studied. Atrial pacing studies were performed while His bundle electrograms were recorded in fourteen patients with sinus bradyeardia, syncope, or related symptoms. Measurements were repeated after 0.01 mg/kg ouabain, followed in some by 1 mg atropine. Ouabain produced a significant shortening of sinoatrial recovery time, but no significant change in heart rate. Atropine normalized sinoatrial recovery times in most patients. This study demonstrates that digitalis causes an increase in automaticity in the sick sinus syndrome as reflected by a shortened sinoatrial recovery time. The efficacy of contemplated therapeutic agents in sick sinus syndrome can be evaluated by rapid atrial pacing. When clinically indicated, digitalis may be used for congestive heart failure or tachyarrhythmias in the sick sinus syndrome in the absence of significant A-V conduction disease.