Masaki Oguma

Effect of diltiazem on coronary blood flow distribution in dog heart under ischemia

Effect of intracoronary infusion of diltiazem (1 μg/min) on regional myocardial blood flow (RMBF) was studied using 15-μm radioactive microspheres in 11 excised cross-circulated canine left ventricles. With total coronary blood flow (CBF) and heart rate (HR) held constant, regional ischemia was induced by ligating the left anterior descending coronary artery (LAD). Diltiazem at the dose used had no effects on ventricular Emax before and after LAD ligation. RMBF expressed by the counts divided by the counts averaged in ail segments in each layer significantly (p < 0.05) increased under diltiazem only in the low-flow region that had <50% RMBF before diltiazem; from 21% (±12%) to 35% (± 18%) in the epicardial, from 22% (± 12%) to 32% (±18%) in the midwall, and from 24% (±10%) to 31% (±12%) in the endocardial layers. We conclude that the beneficial effect of diltiazem on the ischemie heart involves a direct action on the coronary vascular system and does not necessarily depend on the concomitant changes in hemodynamics.

Quadricuspid aortic valve illustrated by 64-slice multidetector computed tomography: Surgical treatment of a rare cause of severe aortic regurgitation

The quadricuspid aortic valve (QAV) is a rare congenital malformation that usually presents with aortic regurgitation (AR). The first case was reported in 1862. Most cases were diagnosed at the time of surgery or postmortem examination. With advances in imaging techniques, more cases have been diagnosed before surgery. We describe a 59-year-old man whose QAV had not been noted until the current admission. Transthoracic echocardiography revealed dilation of the left ventricle, severe AR, and suspected QAV. The QAV was confirmed by transesophageal echocardiography and 64-slice multidetector computed tomography. This case was a QAV with three equal cusps and one smaller cusp (type B in Hurwitz and Roberts classification). Because the cardiac catheterization and aortography showed severe AR and a QAV, the patient underwent elective surgery. The surgery consisted of replacing the QAV by a mechanical prosthesis. There were no post-operative complications. The patient revealed no symptoms in the post-operative 7 months.

Transcatheter coil embolization of coronary artery fistulas

Congenital coronary artery fistulas (CAFs), which have been known since 1865, are rare congenital cardiac abnormalities. Most of the CAFs are discovered incidentally during coronary angiography. We described our experience with successful transcatheter coil embolization of CAFs in an adult, leading to improvement of symptoms. The patient had chest pain or dyspnea on exertion. The CAFs originated from the left anterior descending coronary artery and the circumflex artery. They all drained into the pulmonary trunk. The coils were implanted through a microcatheter, which was passed through a 7F guiding catheter. The coils were used to occlude the CAFs completely. The procedures were uncomplicated. Patients chest pain or dyspnea resolved after the procedures. Although the patient had small residual flow at the CAFs from the circumflex artery at follow-up coronary angiography, the patient was asymptomatic. Therefore, we considered the coil embolization to be successful. Transcatheter closure of CAFs with coil is a valid option, and can be regarded as an acceptable alternative to surgery nowadays.

Segmental diastolic narrowing of epicardial coronary arteries in aortic regurgitation. Phase analysis by quantitative angiography of coronary artery diameter change during cardiac cycles

SummaryA new finding of a segmental narrowing of the left anterior descending coronary artery in diastole (diastolic narrowing: DN) was reported. DN was found in 6 out of 45 patients (13.3%, 5 males, 1 female) with chronic aortic regurgitation (AR). It is likely that aortic regurgitation was more severe in terms of the history of heart failure, regurgitant fraction, left ventricular end-diastolic volume index and pressure, and aortic diastolic pressure in the patients with DN compared with those without DN. The phasic change of DN in cardiac cycles was analyzed by quantitative angiography, and indicated that DN commences at a point in mid-diastole when coronary vascular driving pressure (the instantaneous aortic and LV pressure difference) becomes abnormally reduced, reaches its maximum at end-diastole, and gradually recovers as aortic pressure increases during systole. In two patients, DN was no longer evident after valve replacement. We concluded that DN, a new coronary arteriographic finding, reflects the integrated severity of AR.

Hyperkinetic contraction of a nonischemic segment of ischemic left ventricle in anesthetized dogs

SummaryRegional myocardial function during acute coronary artery occlusion was studied with ultrasonic dimension gauges in 20 open-chest anesthetized dogs. Two pairs of ultrasonic crystals were implanted in the left ventricular free wall near the epicardium in an ischemic segment and in a control nonischemic segment, and the segment length (SL) and maximum velocity of systolic shortening (max dL/dt) were measured. In six dogs, the wall thickness (WT) was measured simultaneously in the same regions with sonomicrometry. Left ventricular pressure (LVP), aortic pressure (AoP), and plasma norepinephrine concentration in the coronary sinus (NECS) were also measured. The heart rate was kept constant (180 beats/min) with atrial pacing. The left anterior descending coronary artery was occluded at its distal portion without propranolol in 12 dogs (group 1) and 30 min after propranolol in eight dogs (group 2). In the ischemic region, coronary artery occlusion resulted in an increase in end-diastolic SL (50% at 3 min after occlusion in group 1,P<0.005), and a decrease in max dL/dt in systole (36% at 5 min after occlusion in group 1,P<0.02). In the nonischemic region, end-diastolic SL did not change significantly, but an increase in max dL/dt (29% at 10 min after occlusion in group 1,P<0.005) was observed in systole. Under propranolol (group 2), the results were similar to those of group 1. There were no significant changes in LVP, AoP, and NECS during occlusion. We conclude that: (1) SL and WT in the same region present a mirror image, suggesting that WT is a useful index for evaluating regional myocardial function; (2) after coronary artery occlusion, while the ischemic region showed hypokinesis, the nonischemic region presented significant hyperkinesis without an increase in preload (end-diastolic SL) or a decrease in ventricular afterload (AoP); and (3) since these results did not change significantly after propranolol and were not accompanied by an increase in NECS, the hyperkinesis in the nonischemic region does not seem to be related toβ-adrenergic receptors and is not due to the Frank-Starling mechanism.