Tadashi Isomura

Surgical Ventricular Restoration for Ischemic Cardiomyopathy with Functional Mitral Regurgitation

Ischemic cardiomyopathy (ICM) is defined as diffuse akinesis of the ventricle after myocardial ischemia1). A subset of patients with ICM develop progressive heart failure as a consequence of adverse left ventricular (LV) remodeling, leading to a depressed ejection fraction, a dilated LV, a large akinetic region of the myocardium, an abnormal globular shape to the ventricular chamber, and functional mitral regurgitation (MR)2-5). Although a dilated LV with poor cardiac function is a risk by itself, coexisting functional MR worsens the prognosis of ICM6,7). Thus, for patients with ICM and functional MR, it is very important to repair the geometric changes of LV remodeling and to decrease the extent of functional MR. For patients with ICM, surgical ventricular restoration (SVR) is an established treatment to reduce ventricular size and restore the elliptical shape of the LV8-12). Anatomical restoration by SVR may decrease the severity of MR, through various mechanisms, including reduction of ventricular dimensions, lowering of end systolic volumes, and restoration of blood flow to the ischemic region of the mitral subvalvular apparatus13,14). However, concomitant procedures for the mitral valve are required for further reduction of functional MR. In this chapter, our therapeutic strategy for patients with ICM is demonstrated, and we describe the details of the surgical techniques of SVR and mitral valve surgery.

Reoperation for calcified aortic homograft after aortic root replacement

Background: We report three cases undergoing reoperation with previous aortic homograft implantation due to structural valve deterioration. Case: For two cases with severe calcified aortic wall of the homograft and dehiscence of the aortic root, aortic root replacement was indicated. For the last case with less calcified aortic wall, aortic valve replacement was indicated via the aortotomy on the homograft, which required patch plasty for the defect of the stiff aortic wall. Conclusion: The distribution and extent of calcification of the aortic homograft would be the most important factor to determine operative procedures, contributing to successful outcomes.

Technical Modifications for Patients with Aortic Stenosis and Calcified Ascending Aorta During Aortic Valve Replacement

Aortic stenosis (AS) is the most prevalent valvular heart disease in developed countries1). Aortic valves deteriorate due to degenerative processes, and calcification is the most frequent cause of AS. Clinical factors related to aortic valve calcification are similar to those for atherosclerosis, and the prevalence of calcified aortic valves increases with age2). As a consequence, AS is associated with a high risk of cardiovascular morbidity and mortality in the elderly3). To achieve longer life expectancy, aortic valve replacement (AVR) is recommended as a definitive treatment for calcified aortic valves4,5). Although the operative mortality of isolated AVR is low, the surgical risk is increased in elderly patients due to concomitant procedures and/or comorbidities associated with advanced age6). Thus, it is very important to plan a careful strategy for co-existing atherosclerotic lesions, especially in the ascending aorta. Atherosclerotic change in the ascending aorta is one of the potential causes of postoperative stroke, which results in higher morbidity and mortality7,8). Most embolic events are associated with manipulation of the ascending aorta such as the clamping of the ascending aorta or the release of aortic crossclamping9). To reduce embolic complications, surgical treatments have changed, and there are several techniques, including AVR during hypothermic circulatory arrest (HCA)10-12), complete thromboendarterectomy during HCA13), endarterectomy or ascending aorta replacement during HCA14), endoaortic balloon occlusion15), and apicoaortic conduit16). Despite aggressive attempts to deal with the calcified ascending aorta, surgical outcomes such as the stroke rate, morbidity, and mortality have remained unsatisfactory. This paper describes our surgical strategy for patients with AS associated with a diseased calcified ascending aorta. Furthermore, meticulous techniques for atherosclerotic lesions designed to avoid perioperative morbidity are described in detail.

Method of ranking of heart valve characteristics at mitral position based on statistical model analysis

The purpose of this study was to explore a valve selection criterion based on the impact force generated at valve closure, and to test a statistical mathematical model for comparing valve performance. The impact force generated at valve closure in the mitral position was measured continuously, using a load cell mounted in the left atrial section of a mock circulatory system. Eight clinical valves were tested. The data obtained from the in vitro test were subjected to multiregression analysis, to enable systematic comparison of the impact forces of these valves. Further-more, class I quantification, theory was applied to construct the statistical mathematical model. As a result, the following interaction effect was observed in the statistical model. (1) The impact force generated at valve closure had a lower value in valves of smaller diameter. (2) The ranking of 29-mm-diameter valves by impact force was different for the flow region. Under the physiological flow condition of 4–61/min, high impact forces were generated in all valves, in the order Björk-Shiley monostrut, ATS, St. Jude medical, CarboMedics. We consider that low impact force at valve closure is desirable, upon consideration of the influence on the annulus tissue at valve replacement. From these findings, the results of the multiregression analysis provide indications for choosing the optimal value for patients with severe mitral insufficiency (MI).