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Biomedical subjects

T Iwa

Publications and source records attributed to T Iwa.

349 records · Page 20Linked to original sources
PubMedDate not supplied

A muscle powered cardiac assist device for right ventricular support: total assist or partial assist?

A muscle powered cardiac assist device (MCAD) for right ventricular support requires optimized diastolic filling to obtain full stroke and acceptable fluid dynamics. A valved and spring-assembled skeletal muscle ventricle (SMV) was designed as a prototype MCAD, regardless of fluid dynamics. The present study addresses the optimal bypass method for right ventricular support, and predicts the future design for an implantable MCAD. Latissimus dorsi muscle (LDM) of 11 dogs were conditioned electrically for a one year maximum, and transformed into fatigue-resistant muscles (Type I fibers). Superior and inferior vena cavae were anastomosed using one arm of a Y-shaped vascular graft, as an inflow conduit, and the outflow conduit was placed on the main pulmonary artery. SMV was wrapped with transformed LDM and the bypass method was varied by SVC and/or IVC ligation. SMV demonstrated sufficient right ventricular support on total bypass (70% compared with control output), and the maximum pump off-to-on flow ratio (200%) was obtained. Maximum SMV power output was 0.27 X 10(6) erg, which was equivalent to that of canine right ventricle. Right atrial-to-pulmonary artery bypass was also constructed by using SMV in another 14 dogs, and also showed that total bypass was preferable for optimal SMV diastolic filling. In conclusion, specific requirements for a future MCAD include a subsystem assembly such as a spring, magnet, or alternative auxiliary muscle pump assembly for MCAD filling, and total bypass with optimized fluid dynamics and anatomic fitting.

Animals↗
PubMedDate not supplied

Surgical treatment of Wolff-Parkinson-White syndrome combined with variant angina pectoris.

Seven patients with coexistent Wolff-Parkinson-White (WPW) syndrome and variant angina pectoris underwent surgical interruption of an accessory atrioventricular conduction pathway. In two of these patients, perioperative coronary artery spasm occurred. One patient had a perioperative myocardial infarction and the other patient treated successfully had no infarction. Nitroglycerin and nifedipine were administered during and following operation in the other 5 patients without perioperative coronary artery spasm. No adverse effect was observed in the intraoperative electrophysiological study. Combined therapy of intravenous nitroglycerin administration and sublingual nifedipine administration are useful in the perioperative management of patients with coexistent WPW syndrome and variant angina pectoris.

Adult↗
PubMedDate not supplied

Surgical treatment for myocardial bridge using intraoperative echocardiography. A report of two cases.

Two cases of symptomatic myocardial bridging of the left anterior descending coronary artery (LAD) requiring surgery for relief of exertional angina are reported. High-frequency intraoperative echocardiography was used for imaging of the intramyocardial coronary artery lesions before and after supraarterial myotomy performed under cardiopulmonary bypass. The constricting band of the myocardial bridge could be clearly demonstrated. Supraarterial myotomy was successfully carried out in each patient. We conclude that intraoperative echocardiography for detecting myocardial bridge is a useful tool for supraarterial myotomy.

Adult↗
PubMedDate not supplied

Improved surgical treatment of tricuspid insufficiency in combined valvular diseases.

Tricuspid insufficiency is not infrequent in combined valvular diseases. We used Carpentier's De Vega's or Bex's annuloplasty with our own modification in combined tricuspid insufficiency and found the results much more satisfactory compared with previous methods. Of 152 patients with acquired valvular disease, 24 with combined valvular disease underwent one of these procedures. During the same period, three tricuspid valve replacements, using a glutaraldehyde-treated xenograft, were performed in patients with severly damaged tricuspid valves. Simultaneous procedures for other valves were open mitral commissurotomy in 14, mitral valve replacement in 9 and aortic and mitral valve replacement in 4 patients. Despite the seriousness of their preoperative condition, 25 of 27 patients survived, resulting in a mortality rate of 7.4%. We believe that these annuloplasty methods represent a remarkable progress in the treatment of tricuspid valve insufficiency in combined valvular diseases.

Adult↗