Biomedical subjects

Yu Shomura

Publications and source records attributed to Yu Shomura.

5 recordsLinked to original sources

PubMed2005

Aortic root dynamics are asymmetric.

BACKGROUND AND AIM OF THE STUDY: The presence of conformational changes in the aortic root during the cardiac cycle is well known, but precise information on time-related changes at each level of the root is lacking. METHODS: High-resolution, 3D sonomicrometry (200 Hz) was applied in an acute sheep model. Twelve crystals were implanted in eight sheep at each base (n = 3), commissure (n = 3), sinotubular junction (n = 3) and ascending aorta (n = 3). Under stable hemodynamic conditions, geometric changes of the perimeter of each sinus of Valsalva, sinus height, and twist and root tilt angles were time-related to left ventricluar (LV) and aortic pressures. RESULTS: Expansion of the perimeter of the three sinuses of Valsalva was homogeneous, but in significantly different proportions (p < 0.001): the right sinus expanded (+32.4 +/- 2.4%) more than the left (+29.3 +/- 3.2%), and more than the non-coronary (NC) sinus (+25.8 +/- 1.7%). A similar pattern was found for aortic root height: right greater than left, and left greater than NC sinus (p < 0.001). This asymmetry resulted in changes of the root's twist and tilt angles. Although the twist deformation was consistent for each sheep, no general pattern was found. The aortic root tilt angle (between the basal plane and the commissural plane) was 16.3 +/- 1.5 degrees at end-diastole (angle oriented posteriorly and to the left). During systole, it was reduced by 6.6 +/- 0.5 degrees, aligning the LV outflow tract with the ascending aorta. This tilt angle returned to its original value after valve closure. CONCLUSION: Aortic root expansion is asymmetric, generating precise changes in its tilt angle. During systole, tilt angle reduction resulted in a straight cylinder that probably facilitates ejection; during diastole, the tilt angle increased, probably reducing leaflet stress. These findings should impact upon surgical procedures and the design of new prostheses.

Animals↗

PubMed2004

[Chordal cutting for the treatment of ischemic mitral regurgitation: two case reports].

The surgical treatment for ischemic mitral regurgitation remains controversal. Ring annuloplasty results in recurrent mitral regurgitation in some cases. Strut chordal cutting is a new surgical procedure in addition to ring annuloplasty for ischemic mitral regurgitation. Two patients (63-year-old woman, 53-year-old man) with severe ischemic mitral regurgitation were treated with this procedure. The patients had congestive heart failure due to mitral regurgitation, associated with inferior myocardial infarction. Regurgitant fraction of mitral regurgitation was 70% and 52% before surgery. Mitral leaflet tethering caused by apical displacement of the papillary muscle was observed. Mitral valve repair was performed by ring annuloplasty and chordal cutting. Intraoperative echocardiography showed that chordal cutting improved the configuration of the anterior leaflet, resulting in good mitral valve coaptation without regurgitation.

Cardiac Surgical Procedures↗

PubMed2003

Late results of mitral valve repair for mitral regurgitation.

OBJECTIVE: This study was undertaken to evaluate the long-term results of mitral valve repair for mitral regurgitation. METHODS: Between 1991 and 2000, 301 patients with mitral regurgitation underwent mitral valve repair. There were 167 men and 134 women whose mean age was 56 +/- 14 years. The patients were comprised of 7 patients in Carpentier's type I, 277 patients in type II, and 17 patients in type III. Chordal replacement with expanded polytetrafluoroethylene sutures had been prospectively applied to repair the anterior mitral leaflet prolapse. Ring annuloplasty was performed in 230 patients (76%). The follow-up was complete and mean follow-up was 67 +/- 33 months, for a cumulative follow-up of 1,624 patient-years. RESULTS: There were 5 hospital deaths and 11 late deaths (2 cardiac and 9 noncardiac). All survivors except those with stroke were in the New York Heart Association (NYHA) functional class I or II. At 10 years, the actuarial survival was 90 +/- 3%, the freedom from embolism was 86 +/- 4%, the freedom from reoperation was 96 +/- 2%, and the freedom from valve-related events was 77 +/- 4%. At 10 years, the freedom from reoperation in the patients with anterior leaflet prolapse was 90 +/- 5%. CONCLUSIONS: Mitral valve repair is feasible in most patients with mitral regurgitation and is associated with low mortality and low rates of valve related events. Chordal replacement with expanded polytetrafluoroethylene sutures is effective, safe, and durable at long-term follow-up for patients with anterior leaflet prolapse.

Adolescent↗

PubMed2002

Dynamic balance of the aortomitral junction.

OBJECTIVE: The aortic and mitral valves have been studied in isolation, as if their functions were independent. We hypothesized that both valves work in synchrony on the basis of the shared myocardial pump and orifice. METHODS: Six sonometric crystals (7 sheep) were placed in both trigones, the midpoint of the anterior and posterior anulus, and the lateral extremities of the posterior anulus. In a separate series of animals, 3 crystals (8 sheep) were implanted in the aortic annular base of the right, left, and noncoronary sinuses of Valsalva. In an acute, open-chest model, under stable hemodynamic conditions, geometric changes were time related to simultaneous left ventricular and aortic pressures. RESULTS: From mid-diastole to end-systole, the mitral anulus area contracted by -16.1% +/- 1.9% (mean +/- SEM), whereas the aortic base area expanded by +29.8% +/- 3.3% during systole. The mitral anulus deformation was heterogeneous. In systole, the anterior mitral anulus expanded (intertrigonal distance, +11.5% +/- 2.3%) and the posterior mitral anulus contracted (distance between lateral extremities of the posterior anulus, -12.1% +/- 1.5%). The intertrigonal distance corresponded to the base of the left and noncoronary sinus of Valsalva, which expanded similarly during systole (+12.9% +/- 2.0%). The anteroposterior diameter of the mitral anulus was reduced twice that of the transverse diameter. This disparity of reduction can be explained by the posterior displacement of the intertrigonal area corresponding to the systolic aortic root expansion. CONCLUSIONS: Mitral anulus deformation is closely related to aortic root dynamics. During systole, the posterior movement of the aortic curtain allows for aortic root expansion, probably to maximize ejection, whereas during diastole, aortic root reduction participates in mitral anulus dilatation. These findings should affect mitral and aortic surgical approaches.

Animals↗

PubMedDate not supplied

Dissecting aneurysm of the superior mesenteric artery successfully treated by endovascular stent-graft placement.

Spontaneous and isolated dissecting aneurysm of the superior mesenteric artery is a rare event that has been successfully treated by surgery in several reported cases. To our knowledge, we present the first case of a patient with spontaneous and isolated dissecting aneurysm of the superior mesenteric artery that was successfully treated by endovascular stent-graft placement.

Aortic Dissection↗