Computer-generated three-dimensional animation of the mitral valve

First finite element model of the left ventricle with mitral valve: insights into ischemic mitral regurgitation

BACKGROUND

Left ventricular remodeling after posterobasal myocardial infarction can lead to ischemic mitral regurgitation. This occurs as a consequence of leaflet tethering due to posterior papillary muscle displacement.

METHODS

A finite element model of the left ventricle, mitral apparatus, and chordae tendineae was created from magnetic resonance images from a sheep that developed moderate mitral regurgitation after posterobasal myocardial infarction. Each region of the model was characterized by a specific constitutive law that captured the material response when subjected to physiologic pressure loading.

RESULTS

The model simulation produced a gap between the posterior and anterior leaflets, just above the infarcted posterior papillary muscle, which is indicative of mitral regurgitation. When the stiffness of the infarct region was reduced, this caused the wall to distend and the gap area between the leaflets to increase by 33%. Additionally, the stress in the leaflets increased around the chordal connection points near the gap.

CONCLUSIONS

The methodology outlined in this work will allow a finite element model of both the left ventricle and mitral valve to be generated using noninvasive techniques.

Initial results of posterior leaflet extension for severe type IIIb ischemic mitral regurgitation

BACKGROUND

Management of severe ischemic mitral regurgitation remains difficult with disappointing early and intermediate-term surgical results of valve repair.

METHODS AND RESULTS

Forty-four patients with severe (4+) Carpentier type IIIb ischemic mitral regurgitation underwent mitral valve repair, with or without surgical revascularization, by posterior leaflet extension with a patch of bovine pericardium and a remodeling annuloplasty. Serial echocardiography was performed preoperatively, intraoperatively, and postoperatively to assess mitral valve competence. The postoperative functional status of patients was assessed. The average Parsonnet score was 38+/-13. Thirty-day mortality was 11%, and late mortality was 14%. Mean follow-up was 38 months. The actuarial freedom from moderate or severe recurrent mitral regurgitation was 90% at 2 years, whereas 90% of patients were in New York Heart Association class I at 2 years.

CONCLUSIONS

Posterior leaflet extension with annuloplasty of the mitral valve for severe type IIIb ischemic regurgitation is a safe, effective method that provides good early and intermediate-term competence of the mitral valve and therefore good functional status.

Simulation in plastic surgery training and education: the path forward

SUMMARY

Computer-based training simulators have been used extensively, most notably in flight simulation. Over the past 20 years, surgical simulators have been developed, initially for training of minimally invasive surgery and more recently for open surgical simulation. The key effort in today's surgical simulation field is to develop metrics to evaluate how well the skills learned in a simulator translate to improvement in real surgical skills, execution of procedures, and team cooperation in the operating room. The American College of Surgeons has begun implementing a phased approach to introduce simulation in training and education for general surgery. The authors believe that a similar training plan should be mandated for plastic surgery, to take advantage of the use of computers, virtual reality, and simulation in the training of plastic surgery residents and to explore the value of this technology for continuing medical education and maintenance of certification. This article gives a brief background and history of surgical simulation and its technology, followed by a detailed description of the three phases of the American College of Surgeons' plan and how the authors propose that each phase be implemented, with modifications as applicable for trainees in plastic surgery.

Effects of acute ischemic mitral regurgitation on three-dimensional mitral leaflet edge geometry

BACKGROUND

Improved quantitative understanding of in vivo leaflet geometry in ischemic mitral regurgitation (IMR) is needed to improve reparative techniques, yet few data are available due to current imaging limitations. Using marker technology we tested the hypotheses that IMR (1) occurs chiefly during early systole; (2) affects primarily the valve region contiguous with the myocardial ischemic insult; and (3) results in systolic leaflet edge restriction.

METHODS

Eleven sheep had radiopaque markers sutured as five opposing pairs along the anterior (A(1)-E(1)) and posterior (A(2)-E(2)) mitral leaflet free edges from the anterior commissure (A(1)-A(2)) to the posterior commissure (E(1)-E(2)). Immediately postoperatively, biplane videofluoroscopy was used to obtain 4D marker coordinates before and during acute proximal left circumflex artery occlusion. Regional mitral orifice area (MOA) was calculated in the anterior (Ant-MOA), middle (Mid-MOA), and posterior (Post-MOA) mitral orifice segments during early systole (EarlyS), mid systole (MidS), and end systole (EndS). MOA was normalized to zero (minimum orifice opening) at baseline EndS. Tenting height was the distance of the midpoint of paired markers to the mitral annular plane at EndS.

RESULTS

Acute ischemia increased echocardiographic MR grade (0.5+/-0.3 vs 2.3+/-0.7, p<0.01) and MOA in all regions at EarlyS, MidS, and EndS: Ant-MOA (7+/-10 vs 22+/-19 mm(2), 1+/-2 vs 18+/-16 mm(2), 0 vs 17+/-15 mm(2)); Mid-MOA (9+/-13 vs 25+/-17 mm(2), 3+/-6 vs 21+/-19 mm(2), 0 vs 25+/-17 mm(2)); and Post-MOA (8+/-10 vs 25+/-16, 2+/-4 vs 22+/-13 mm(2), 0 vs 23+/-13 mm(2)), all p<0.05. There was no change in MOA throughout systole (EarlyS vs MidS vs EndS) during baseline conditions or ischemia. Tenting height increased with ischemia near the central and the anterior commissure leaflet edges (B(1)-B(2): 7.1+/-1.8mm vs 7.9+/-1.7 mm, C(1)-C(2): 6.9+/-1.3mm vs 8.0+/-1.5mm, both p<0.05).

CONCLUSIONS

MOA during ischemia was larger throughout systole, indicating that acute IMR in this setting is a holosystolic phenomenon. Despite discrete postero-lateral myocardial ischemia, Post-MOA was not disproportionately larger. Acute ovine IMR was associated with leaflet restriction near the central and the anterior commissure leaflet edges. This entire constellation of annular, valvular, and subvalvular ischemic alterations should be considered in the approach to mitral repair for IMR.