[Clinical experience of coronary artery bypass grafting using surgical microscope].

Since 1991, we have attempted to use a surgical microscope for 62 coronary bypass anastomoses. Four kinds of microscopes were used under high magnification (6 to 8x). The suturing thread length was 5-10 cm to make anastomosis and handling of the needle easier. It was concluded that a surgical microscope could be best used for anastomosis of an internal thoracic artery graft with the left anterior descending coronary artery. Excellent graft patency and improvement of the quality of anastomosis were confirmed.

[Comparison of long-term clinical results of the three models of the Björk-Shiley valve prosthesis and the Omnicarbon valve prosthesis].

A multi-institutional cooperative study, that was a comparison of long-term results of the replacement of the four models of the oblique disc valve prosthesis which had been implanted on aortic and mitral position alone or double from December 1976 to September 1992 in the eight national hospitals in Japan was performed. Seven hundred and thirty-four patients and 765 prostheses that consisted of 582 patients and 610 prostheses of the Björk-Shiley (BS) valve, including 326 patients of the Spherical disc (SP) valve (49 aortic, 259 mitral, and 18 double aortic-mitral), 103 patients of the Convexoconcave disc (CC) valve (45, 51, 7) and 153 patients of the Monostrut (MS) valve (101, 49, 3), and of 152 patients (71, 78, 3) and 155 prostheses of the Omnicarbon (OC) valve were compared with their mortality and morbidity in every valve position respectively according to the approval by STS-guideline. The MS valve and the OC valve showed 0% to 11.3% of operative mortality, 0.3%/py to 1.8%/py of valve related mortality, 85.5% +/- 5.6% to 98.4% +/- 1.6% of actuarial survival rate at 10 years, and 58.5% +/- 6.4% to 82.7% +/- 5.7% of actuarial free rate of all mortality and morbidity at 10 years in every valve position. Structural deteriorations occurred in two patients of the CC valve in the mitral position only, and its rate of all valve positions showed 0.04%/py. Significant differences were seen in actuarial survival rate at 10 years after aortic valve replacement, and in operative mortality rate, improved degree of NYHA class, structural deterioration rate and actuarial free rate of all mortality and morbidity after mitral valve replacement between the group of the MS and OC valve and the group of the SP and CC valve. Therefore the MS valve or the OC valve should be selected to implant rather than the SP valve or the CC valve, and the patient who had been implanted with the CC valve should be treated considering valve position, valve position, valve size, age and activity of the patient and the manufactured date of the prosthesis.

Rate-dependent threshold changes during atrial pacing: clinical and experimental studies.

In 36 patients undergoing a permanent right atrial pacing for the treatment of sick sinus syndrome and/or atrioventricular block, the stimulation threshold was determined at a wide range of pacing rates (60 to 120 beats/min) 7 to 10 days after the lead implantation. Twenty-nine (80%) of these cases showed rate-dependent threshold changes, with significantly lower thresholds at higher than lower pacing rates (e.g., 2.91 +/- 1.01 mA at 70 beats/min and 2.32 +/- 0.75 mA at 120 beats/min, P less than 0.01). Thus, with a fixed, smaller current strength, the stimuli often failed to capture the right atrium at lower rates, but caused a 1:1 capture at higher rates. In an echocardiographic study in another series of eight patients, the end-diastolic diameter of the left atrium was decreased from 3.2 +/- 0.9 to 2.7 +/- 0.8 cm (P less than 0.01) when the pacing rate was increased from 60-70 beats/min to 100-120 beats/min. In experiments using two anesthetized, open-chest dogs, a rapid withdrawal of 500 mL of arterial blood reduced the right atrial dimension. This was accompanied by an increased amplitude of the right atrial endocardial electrogram, and the initially subthreshold stimuli became effective in capturing the atria. It was concluded that (1) rate-dependent threshold changes were commonly observed in the early stage of atrial pacing, and (2) fluctuations in the electrode contact with the endocardium appeared responsible for such threshold changes.

[Surgical treatment of a case of arrhythmogenic right ventricular dysplasia with local myocardial resections].

A 39-year-old man who was diagnosed as ARVD (arrhythmogenic right ventricular dysplasia) with nonischemic sustained ventricular tachycardia (VT) was successfully treated by surgical resection of two parts of the right ventricular free wall, one was the site of earliest excitation during induced VT and the other was an area where delayed potentials were detected during sinus rhythm. A surface mapping was made by means of a computer guided system. A preoperative study of endocardial mapping and a programmed electrical stimulation test were an useful adjunct for surgical management of ARVD. After surgery VT could not be induced by triple extrastimuli and up to now there has been no recurrence of VT more than 2 years after surgery without medication.

Prevention of coronary spasms during aorto-coronary (A-C) bypass surgery for variant angina and effort angina with ST-elevation.

Aorto-coronary (A-C) bypass surgery was carried out in 15 cases of Prinzmetal's angina and effort angina with ST-elevation, commonly ascribed to coronary vasospasms. A-C bypass surgery is usually indicated for vasospastic angina when there are significant organic lesions of the coronary arteries. Fifty mg of verapamil was added to the priming solution for cardiopulmonary bypass, and A-C bypass surgery was successfully performed without the occurrence of perioperative coronary spasms even though severe episodes of spasm had been documented before surgery. However, four cases of vasospastic angina not receiving verapamil developed coronary spasms during or after A-C bypass surgery. It was concluded that administration of verapamil, a potent calcium entry blocking agent, is effective in preventing perioperative coronary vasospasms. Patency of the saphenous vein grafts bypassing the spasm-related coronary arteries was satisfactory.

Development of glassy carbon electrode (Dead Sea scroll) for low energy cardiac pacing.

We have developed a new type of glassy carbon electrode whose smooth surface with scattered craters reduces its polarization voltage. It has both excellent antithrombogenicity and slight tissue reaction. The energy threshold curve was the lowest when compared to the Siemens (411S, 412S) and the Solin (S-100) electrodes.

Experimental comparison of the efficacy of various agents on the enhancement of myocardial protection.

Experimental studies were carried out to compare the efficacy of various agents such as calcium antagonists, phosphodiesterase inhibitors, adrenocorticosteroids, coenzyme Q10 (CoQ10), insulin, beta-blocking agent and reduced glutathion (GSH) on the enhancement of myocardial protection. Eighty-five isolated rabbit hearts were subjected to 2 hours of cardioplegic arrest, and maximum developed tension, heart rate, coronary blood flow and coronary arteriovenous oxygen difference following reperfusion were compared between groups pretreated with different agents. The greatest value of maximum developed tension was obtained in the verapamil-treated group (0.2-0.5 mg/kg), followed by dilazep (1 mg/kg), pentoxifylline (30 mg/kg) and CoQ10 (10 mg/kg) treated groups. The time required for the recoveries of spontaneous beating (normal sinus rhythm) on reperfusion was shortest (44 +/- 8 sec) in the group treated with a cardioplegic solution containing a low concentration of betamethasone (0.03-0.05 mg/ml), but the so-called stone hearts and cardiac arrhythmias were most frequently seen in this group. On the contrary, in the group pretreated with calcium antagonists, the time required for the restoration of sinus rhythm was much longer (88-180 sec). Hence, the shortest recovery time was not necessarily associated with a better recovery of myocardial function.

Surgical correction of double outlet left ventricle associated with hypoplastic right ventricle: direct anastomosis of right atrial appendage and pulmonary artery.

This reports concerns a 9 years old boy, who had situs solitus and atrioventricular concordance with double outlet left ventricle, pulmonary stenosis, tricuspid stenosis, ventricular septal defect, secundum atrial septal defects and hypoplastic right ventricle. Previous Blalock-Taussig shunt was created at the age of 11 months. Total correction consisted of closure of atrial septal defect and tricuspid valve orifice, and direct anastomosis of right atrial appendage to pulmonary trunk. Though atrial pacing was required for the immediate post operative period, the patient regained sinus rhythm 3 days after operation. He is doing well at present, one year after the operation.