Hiroshi Katsume

Estimation of right ventricular volume with two dimensional echocardiography.

Abstract To evaluate the applicability of two dimensional echocardiography to right ventricular volume determination, a study was made of 33 consecutive patients separated into three groups (control, right ventricular volume overload and right ventricular pressure overload). Biplane two dimensional echocardiograms that were perpendicular to each other were obtained from the apical approach. The echocardiographic right ventricular volume, calculated by applying Simpsons rule, was considered to be right ventricular body volume without right ventricular outflow tract volume. The echocardiographic dimensions of the right ventricular long, short and maximal short axes were also measured in each view. These volumes and dimensions were compared with both the angiographic right ventricular body volumes calculated by applying Simpsons rule and with the values in each group. Correlation between the echocardiographic and the angiographic right ventricular body volumes (r = 0.94 at end-diastole, r = 0.84 at end-systole) was good and much better than that between echocardiographic right ventricular dimensions and angiographic right ventricular body volumes. Echocardiographic calculation of right ventricular body volume was useful in distinguishing the control group from the group with right ventricular volume overload (p The correlation between the echocardiographic dimensions of the right ventricular long axis and angiographic right ventricular volumes was poor, whereas that between the echocardiographic dimensions of the right ventricular short or maximal short axis and the angiographic right ventricular volumes was fairly good. It was therefore suspected that during right ventricular enlargement, the increase in size is more extensive in the direction of the short than in the direction of the long axis. It is concluded that estimation of right ventricular volume and morphology with two dimensional echocardiography may be of value in clinical practice.

Prolonged atrial activity due to delayed conduction in the atrium of patients with paroxysmal atrial fibrillation

SummaryWe investigated the relationship between the duration of electrical atrial activity and intra-atrial conduction time to determine whether the prolonged atrial activity was due to delayed conduction in the human atrium. The study included 15 patients with paroxysmal atrial fibrillation (PAF) and 15 control patients. The duration of atrial electrical activity was measured by selecting a minimum electrographic amplitude of 50µV. In patients with PAF, the duration of atrial activity was prolonged in proportion to the delay of interatrial conduction time from the high right atrium to the coronary sinus as the coupling interval of premature extrastimuli was decreased. Both the fragmented atrial activity zone and the interatrial conduction delay zone were wider in patients with PAF than in control patients. It is concluded that assessment of the duration of atrial activity with a minimum amplitude of 50µV is useful in evaluating human atrial vulnerability since it reflects the atrial conduction delay in patients with PAF.

A case of left ventricular aneurysm of uncertain etiology presenting as ventricular tachycardia

A case of a 59-year-old Asian male with several episodes of syncope and palpitation is reported. Electrophysiologic study disclosed that sustained ventricular tachycardia was induced by programmed electrical stimulation at the right ventricular apex. The electrogram in the left ventricular aneurysm showed delayed activities and the fastest depolarization. Entrainment was observed by faster pacing. Left ventriculography showed a large aneurysm and normal coronary arteries. Congenital left ventricular aneurysm is the most likely clinical diagnosis given the lack of past history of chest pain, myocarditis, cardiomyopathy, etc. Congenital aneurysm which presents as ventricular tachycardia is very rare, and has never been reported in an Asian. Medical management has thus far been successful.

Electrophysiological effects of bethanidine sulfate on guinea-pig papillary muscle

Bethanidine, a chemical analog of bretylium, increased the plateau phase of the action potential of guinea-pig papillary muscle in 2.7 mM K+ Tyrode solution without changing other electrophysiological parameters. In 25 mM K+ Tyrode solution, the amplitude, duration and Vmax of the Ca2+-dependent action potential were increased in a dose-dependent manner by bethanidine. It is speculated that the mechanism of antiarrhythmic effect of bethanidine might be due to the prolongation of action potential by an increase of the slow inward current.