Senichi Tanaka

Reduced baroreceptor sensitivity in borderline hypertension.

The sensitivity of the baroreceptor reflex in nine patients with borderline hypertension (mean age 19.1 plus or minus 0.2 years) was compared to that in six normal subjects of comparable age (mean 18.8 plus or minus 0.3 years) and that in 14 patients with established hypertension (mean age 48.3 plus or minus 3.1 years). The sensitivity of the baroreceptor reflex was assessed by determining the slope of the regression line relating the rise of systolic pressure to the prolongation of the R-R Interval during the transient rise of arterial pressure induced by an intravenous injection of phenylephrine. The average baroreceptor slope in nine patients with borderline hypertension was 9.1 plus or minus 0.8 msec/mm Hg, which was significantly less than that in six normal subjects (16.0 plus or minus 2.0; P smaller than 0.01), but was greater than that in 14 patients with established hypertension (4.9 plus or minus 0.7; P smaller than 0.01). The significant negative correlation was found as the baroreceptor slope was related to the mean arterial pressure in patients with borderline hypertension and normal subjects, all of whom were 20 years old or less. Attenuation of the baroreceptor sensitivity may influence the maintenance of raised arterial pressure in borderline hypertension.

Increased exercise tolerance after oral diltiazem, a calcium antagonist, in angina pectoris

Effects of diltiazem, a recently introduced calcium antagonist, on exercise performance were studied in nine coronary disease patients with effort angina. The duration of exercise before the onset of angina and the time to the onset of ischemic ST depression 2 hours after 90 mg of oral diltiazem were compared with those 2 hours after oral placebo and a few minutes after 0.3 mg of sublingual nitroglycerin. Diltiazem prolonged the duration of exercise in all nine patients (average 2.5 minutes, p less than 0.001) and delayed the onset of ischemic ST depression (average 2.4 minutes, p less than 0.001). The increment of the duration of exercise and the time to the onset of ischemic ST depression following 90 mg of oral diltiazem were almost equivalent to that following sublingual nitroglycerin. These results in fixed coronary atherosclerosis indicate the clinical antianginal efficacy of diltiazem which persists for at least 2 hours after oral administration.

Left atrial ball thrombus diagnosed by two-dimensional echocardiography

The diagnosis of the ball thrombus in the left atrium has been very difficult by conventional clinical techniques. In the present case, two-dimensional echocardiography successfully demonstrated a spherical tumor moving in unpredictable directions in the left atrium. M-mode echocardiography did not clearly identify the tumor because of the limited visual width and spatial orientation of the technique; however, simultaneous recordings of the M-mode echocardiogram with phonocardiogram, carotid pulse wave, and electrocardiogram provided some diagnostic clues to the occlusive left atrial tumor. In the absence mitral valve occlusion by the tumor, a logarithmic correlation between the ejection time and the preceding R-R interval, and a negative lines correlation between Q to the first sound interval and the preceding R-R interval were found. In the beat following the appearance of the tumor in the mitral orifice, the sudden shortening of the ejection time and the prolongation of Q to the first sound interval were noted. Both of these findings are indirect evidence of decreased left ventricular filling associated with an elevated left atrial pressure resulting from the sudden mitral orifice obstruction by the tumor. Detailed analysis of the data obtained by the conventional noninvasive techniques could provide critical clues for the diagnosis of the occlusive left atrial tumor.

Baroreflex sensitivity in patients with Takayasu's aortitis.

Takayasus aortitis is an arterial inflammatory disease of arteries of unknown etiology. Fainting is a common symptom and has been attributed to hypersensitivity of the baroreflex. We studied baroreflex sensitivity in 11 patients with Takayasus aortitis and compared it with that of eight control subjects of comparable age. Baroreflex sensitivity was assessed by determining the slope of a regression line relating the rise of systolic arterial pressure to the prolongation of the R-R interval of the electrocardiogram during a transient rise of arterial pressure induced by an intravenous injection of phenylephrine. The average baroreflex slope of patients with Takayasus arteritis (4.0 ± 0.8 msec/mm Hg) was signiffcantdy less than that of control subjects (10.7 ± 0.8 msec/mm Hg, P < 0.001). Reduced baroreflex sensitivity in patients with Takayasus aortitis may be due to the hardening of the arteries where baroreceptors lie, or to hypertension and/or cardiac disease which was present in most of the patients included in the study. Patients with Takayasus aortitis who complained of fainting also showed the reduced baroreflex sensitivity. This indicates that fainting in this disease is not likely to be caused by the hyperreactivity of the baroreceptors as is commonly postulated.

Early closure of the tricuspid valve in a case of Ebstein's anomaly with type B Wolff-Parkinson-White Syndrome.

Echocardiographic studies of a 19-year-old female with Ebsteins anomaly and type B Wolff- Parkinson-White syndrome showed an earlier closure of the anterior tricuspid leaflet (ATL) than of the anterior mitral leaflet (AML), contrary to the previous reports. The interval between the closure of the ATL and the AML was 20 msec and 30 msec, respectively, before and after administation of edrophonium chloride. However, closure of the AML preceded that of the ATL after administration of atropine sulfate and during supraventricular tachycardia by 10 msec and 60 msec, respectively, concomitant with the shortening of the duration of the QRS complex. We conclude that early closure of the ATL may depend on preexcitation of the right ventricle.