Tetsuo Mizutani

Hyperreactivity of coronary arterial smooth muscles in response to ergonovine from rabbits with hereditary hyperlipidemia.

This study was undertaken to examine the response to ergonovine, an agent used to provoke spastic constriction of large epicardial coronary arteries, to elucidate the, responsible underlying mechanism, and to determine the impact of endogenous hyperlipidemia on contractile properties of isolated vessels from different beds. The isolated arteries from both control and Watanabe hereditary hyperlipidemic rabbits (WHHL rabbits) were suspended for recording isometric force in oxygenated Krebs buffer and exposed to agonists and antagonists. In athero- sclerotic aortas from WHHL rabbits, the concentration-response relations for ergonovine and serotonin exhibited a marked leftward shift with significantly depressed constrictor threshold concentration and lowered one-half maximally effective concentration values. In coronary arteries with no atherosclerotic lesions detectable macroscopically from WHHL rabbits, the concentration- response relations showed a leftward shift for ergonovine but not for serotonin. Coronary contraction evoked by ergonovine was remarkably inhibited by 0.1μm cyproheptadine and 0.3 μM methysergide, serotonergic antagonists, in both groups. α-Adrenergic blockade with 0.1 JZMprazosin was effective in inhibiting ergonovine-induced contraction of aortas from control rabbits, but not that of atherosclerotic ones. The constrictor response to ergonovine of atherosclerotic aortas was inhibited by cyproheptadine. The responsiveness to ergonovine of both carotid and femoral arteries from WHHL rabbits with no sclerotic lesions, which was suppressed by prazosin was not different from that of control rabbits. In contrast, the concentration-response relations for phenylephrine in the four different types of arteries did not differ appreciably between the two groups, and the constrictor responses to 20 ITIM KG were virtually identical. Thus, aortas and coronary arteries exposed to endogenous hyperlipidemia appear to be hyperreactive to ergonovine mediated by a serotonergic mechanism.

Aorto-bronchial fistula after implantation of a self-expanding bronchial stent in a patient with aortic dissection.

We report a case of aorto-bronchial fistula after implantation of a self-expanding stent into the left main bronchus compressed by a dissected descending aorta. A 66-year-old female, who underwent Stanford type-B aortic dissection two years previously, was admitted to our hospital for the treatment of a newly developed false lumen that originated from the ascending aorta and extended to the aortic bifurcation. She was unable to be weaned from the respirator after the graft replacement of the ascending aorta. Fiberoptic bronchoscopic examination revealed complete obstruction of the left main bronchus by extrinsic compression. A self-expanding nitinol stent was implanted in the left main bronchus five days after the operation. Her respiratory condition improved remarkably, allowing her to be successfully weaned from the respirator. Her clinical course was uneventful until she suddenly died from massive hemoptysis 20 days after stent implantation. A communication of 5 mm in diameter between the dissected descending aorta and the left main bronchus was seen at autopsy. Permanent application of a self-expanding nitinol stent to relieve extrinsic compression of a left main bronchus by a dissected descending aorta is not recommended because pressure necrosis might lead to fatal aorto-bronchial fistula.

Relationship between epicardial and intramyocardial ST-segment voltage and myocardial blood flow during graded coronary constriction in the dog

SummaryThis study was undertaken to examine the relationship between electrographic ST-elevation and regional myocardial blood flow during graded coronary constriction.Electrograms from the epicardial surface, outer and inner layers of the myocardium were recorded. Regional blood flow to the outer and inner layers of the myocardium was measured by means of a heat-clearance method. With the application of a coronary constriction, myocardial blood flow to the inner layer began to decrease with a 75% coronary constriction, while flow to the outer layer was maintained at near normal up to least an 80% coronary constriction.Non-linear squares curve of between ST-elevation and the decrease in myocardial flow resulted in y=18.80 exp−0.06x−0.02 in the outer layer and, y=9.22 exp−0.02x−1.54 in the inner layer. Also the non-linear squares curve of between epicardial St-elevation and the decrease in myocardial flow resulted in y=50.91 exp−0.11x+0.04 in the inner layer and y=10.29 exp−0.07 x+0.03 in the outer layer. The standard deviations of the coefficients of the latter two equations were higher than those of the former two equations. The higher values indicated larger variations of the parameter coefficients and data points.These results clearly demonstrated that a regional intramyocardial electrogram more closely reflects local ischemia than does an epicardial electrogram.ZusammenfassungDiese Untersuchung wurde durchgeführt, um, die Beziehung zwischen ST-Hebung und regionaler Myokarddurchblutung während zunehmender Verengung einer Koronararterie zu untersuchen. Dabei wurden Elektrogramme von der epikardialen Oberfläche und den äußeren und inneren Schichten des Myokards aufgezeichnet. Die regionale Myokarddurchblutung in den äußeren und inneren Schichten des Myokardiums wurde mit Hilfe der Wärme-Clearance-Methode gemessen. Nach Konstriktion der Koronarien begann die Myokarddurchblutung in den inneren Schichten bei einer Verengung > 75% abzunehmen, während die Durchblutung in den äußeren Schichten bis 80% Verengung nahezu normal blieb.Non linear squares curve zwischen ST-Hebung und Abnahme in der regionalen Myokarddurchblutung ergab y=18.80 exp−0.06x−0.02 in der äußeren Schicht und y=9.22 exp−0.02 x−1.54 in der inneren Schicht. Auch non-linear squares curve zwischen ST-Hebung der epikardialen Ableitung und der Abnahme in regionale Myokarddurchblutung ergab y=10.29 exp−0.07 x+0.03 in der äußeren Schicht und y=50.91 exp−0.11 x+0.04 in der inneren Schicht. Die Standardabweichungen der Koeffizienten der vorletzten zwei equations waren höher als die der früheren zwei equations.Diese Ergebnisse zeigen, daß regionale intramyokardiale Elektrogramme eine lokale Ischämie besser repräsentieren als epikardiale Ableitung.

New application of a bipolar Nd:YAG handpiece in laser cardiac surgery

A bipolar Nd-YAG laser (1.064 micrometer) handpiece was experimentally examined for a venous dissection without scissors and sutures and clinically introduced for the vein graft harvesting in coronary artery bypass grafting (CABG). Experimental study: One hundred and thirty-five segments of the mongrel dog veins were employed. Nd-YAG laser was irradiated on the vein held by the bipolar Nd-YAG handpiece at the power of 5, 9, 13, and 17 watts, and success defined as a complete vein citing without bleeding at the laser-applied sites were gained in all except three; 97.8% of success rate. Laser exposure time for cutting the vein decreased in order to an increase of the applied laser power, and the veins of bigger diameter needed more longer exposure time in the group of the same laser power. An average exposure time was 4.4 seconds for the veins of 1 mm diameter at 13 watts. In histological examination, a vascular lumen at the cutting site was diminished and covered with a degenerated vascular wall, and bleeding was not seen in all specimen. Clinical study: In 18 cases of CABG the bipolar Nd-YAG handpiece was applied to cut the branches of the great saphenous vein without scissors and sutures. Forty-two grafts harvested by this handpiece were used for aortocoronary bypass grating. All were survived and the angiographic examination demonstrated a 90% of graft patency at an average period of 3.5 years after the operation. Laser-induced morphological change such as aneurysmal formation or graft stenosis was not recognized.

Myocardial laser coagulation for free wall rupture following acute infarction.

A 73-year-old woman was diagnosed with ventricular free wall rupture following acute myocardial infarction. The lesion was repaired with laser coagulation, fibrinogen-thrombin glue application, and patch reinforcement. Five years after surgery, the patient was in New York Heart Association class I.

A Case Report of Papillary Fibroelastoma of the Aortic Valve.

乳頭状弾性線維腫は原発性心臓腫瘍のうち3番目に多いとされているが, 全心臓腫瘍中8%で, 頻度的には非常に希である. 今回われわれは大動脈弁より発生した乳頭状弾性線維腫の1手術例を経験した. 症例は51歳の女性で検診にて心電図異常を指摘されて当院を受診し, 心エコー検査にて大動脈弁の右冠尖に有茎性腫瘍を認め, 大動脈弁腫瘍と診断された. 腫瘍はゼリー状であり, 大動脈弁の接合状態は良好で機能不全をきたしていなかったので, 腫瘍のみを切除した. 病理組織学的には乳頭状弾性線維腫と診断された.

Right ventricular function during left ventricular assistance evaluated by two-dimensional echocardiography

Right ventricular (RV) function during left heart bypass (LHB) using centrifugal blood pumps was studied in 20 mongrel dogs, which were divided into normal and failing heart groups. RV function was evaluated hemodynamically and by a 2D echocardiography method. Incremental changes in LHB flow ratio from control, 25%, 50%, 75% to the maximum of 85%–100% resulted in decrements of the interventricular septum (IVS) segmental shortening fraction (SSF) from 54%±12%, 43%±5%,42% ±2%, 35%±7% to 1%, respectively. When the LHB ratio was increased from 75% to the maximum level, significant reduction in the RV ejection fraction and a completely depressed left ventricle (LV) were observed. The cross-sectional echo image also revealed profoundly depressed SSF of the IVS and of the nearby RV wall. The LV decompression with the maximum LHB seemed to decrease the contraction capability of the LV wall, including the IVS subsequently causing reduction of the RV wall. This finding was more pronounced in the failing heart group. The excessive LHB for a prolonged duration not only reduces the RV wall contraction capability but may lead to right heart failure.