| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||
Ann Thorac Surg 1996;62:1067-1068
© 1996 The Society of Thoracic Surgeons
DR MARK B. RATCLIFFE (San Francisco, CA):
This is a very good paper, Dr Glasson. I have previously described a technique that I called sonomicrometry array localization, or SAL, which is able to determine the three-dimensional coordinates of whole arrays of sonomicrometry crystals. With modern, commercially available electronics, we can collect the data necessary for the array determination in about 10 milliseconds. Doctors Gorman and Edmunds and their colleagues from the University of Pennsylvania have used this technique to study the pathogenesis of ischemic mitral regurgitation in sheep. Those sheep underwent posterolateral myocardial infarction, which included the posterior papillary muscle. Concurrent echocardiography shows that the mitral regurgitation is between 2+ and 3+. The sonomicrometry crystals were placed not only on the mitral annulus, but also on the submitral apparatus, the papillary muscles, and the ventricular wall. We also saw enlargement of the posterior annulus; however, we saw significant changes in the three-dimensional alignment of the posterior papillary muscle. Specifically, the muscle elongates and then fails to shorten normally after isovolumic contraction, causing the tip of the papillary muscle actually to move closer to the plane of the mitral valve as the ventricle shortens along its long axis. In addition, if you look at the papillary muscle through the mitral valve from the left atrial view, the axis of the posterior papillary muscle actually rotates in a clockwise direction.
We believe that ischemic mitral regurgitation is related to malalignment of the posterior papillary muscle and not just to enlargement of the posterior annulus. Did you have beads on the papillary muscles and on the ventricular wall, and did you see changes similar to those seen with the sonomicrometry crystals? I would be interested in your comments.
DR GLASSON:
Yes, we did. In addition to the annular markers described and analyzed here, our extensive marker array included miniature radiopaque markers placed in the left ventricular subepicardium, as well as sutured to the tips and bases of both papillary muscles, and to various sites on both mitral leaflets. We chose to analyze initially the mitral annular marker data independent of other marker data because three-dimensional dynamic alterations in the size and shape of the mitral annulus that occur during ischemic mitral regurgitation are incompletely understood, yet mitral ring annuloplasty remains a common treatment for this disease. We are currently analyzing data from the left ventricular wall, papillary muscle, and mitral leaflet markers, and we will have further results soon, which we hope to present.
DR RATCLIFFE:
Did your infarct involve the posterior papillary muscle?
DR GLASSON:
We believe it did. Dogs have variable coronary anatomy, and therefore we were not expecting to achieve substantial ischemic mitral regurgitation, as we did in this model. Reports in the literature suggest that sheep have a much more consistent coronary arterial anatomy, and studies that are now ongoing in our laboratory use an ovine model to investigate further the pathogenesis of ischemic mitral regurgitation. We occluded the proximal circumflex coronary artery (in 6 of 7 dogs) or a large posterior descending coronary artery (in 1 dog) to induce ischemic mitral regurgitation in this model. We did not perform histologic examination of the hearts after the study, and therefore we do not know the precise location and size of the ischemic regions. Transthoracic echocardiography performed during coronary occlusion, however, revealed left ventricular wall motion abnormalities in the region of the posterior papillary muscle, suggesting that the ischemic zone did indeed involve the posterior papillary muscle.
Related Article
Ann. Thorac. Surg. 1996 62: 1059-1067.
| ||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |
