Mitral valve annuloplasty and chordal cutting. The effects on interventricular flow of the infarcted heart.

Teeuwen, L.A (2015) Mitral valve annuloplasty and chordal cutting. The effects on interventricular flow of the infarcted heart. thesis, Medicine.

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Abstract

Introduction Ischemic mitral regurgitation (IMR) is the leakage of the mitral valve which is a common complication of coronary artery disease, this is caused by ventricular remodelling. The ventricular remodelling causes the shape of the valve to deform and forces the papillary muscles with chordae tenineae out of place. The pull of the chordae tendineae on the leaflets becomes disruptive: chordal tethering. Most cases are treated with a repair by placement of a ring around the mitral valve forcing the circumference back into its original shape. This technique has great short-term results but regurgitation reoccurs in up to 80% of the cases in 5 years. 4D-flow MRI is a method of evaluating flow dynamics of the left ventricle in-vivo. A healthy ventricle is characterized by the formation of vortices. In previous studies by this institute it was shown that the implantation of under-sized rings, which is common practice in the treatment of IMR, causes significant changes in intra-ventricular flow in healthy animals. The influence of a repair for IMR on the internal ventricular blood flow patterns of the infarcted heart are unknown. Chordal cutting, a technique where the most tethered chordeae are cut, is believed to improve leaflet mobility and coaptation, this could potentially enhance the durability of the repair. Investigating the flowpatterns in hearts treated by these methods could help in developing better and longer lasting repair techniques. Material and Methods Over the course of a year 25 dorset sheep were subject to a series of three subsequent procedures. First an infarct was induced in all animals by ligating a specific part of the circumflex artery. After the infarction has consolidated over the course of 8 to 16 weeks the animals received a pre-operative MRI. Two weeks after the MRI a 28 mm Physio ring was implanted in all animals. A chordal cutting procedure was done at random in half the animals. On the same day a post-operative MRI was performed. All animals were euthanized after completion of the procedures. During the three procedures hemodynamic and echographic data was collected. MRI data was processed in order to assess 4D flow images of the left ventricle pre and post operatively. Data was analysed statistically with students T-test and Chi-square test. Results Nine out of 25 animals survived yielding good results. Most animals died because of the induced MI or surgical complications. Hemodynamic data showed an overall decrease in cardiac function. Bloodflow patterns observed pre and post operatively were incoherent. Almost all animals in the preoperative phase showed vortices close to the mitral valve and a column of flow proceeding towards the apex. The disbanding of the column into vortices was found in half the cases. The other half of the cases the column disbanded without forming vortices. These two distinct flow patterns were also observed post-operatively but held no relation with pre-operative flowpatterns, hemodynamic differences or chordal cutting. Discussion The flow patterns pre-and post-operatively were incoherent but showed components as seen in healthy animals in other studies. The implantation of normal sized rings did not have structural effects on the intra-ventricular flow. The effect of IMR seems to be at random but does not significantly disrupts flow components as seen in healthy subjects. Chordal cutting does not seem to have influence on the intra-ventricular flow as is observed. Undersized rings seem to have most influence on intra-ventricular flow. In general no factors were found to explain the differences in flow patterns. The size of the infarcted area has not been investigated in this study, this could be a factor worth investigating. Improvement of post-processing techniques could help in describing flows more adequately and determine effects of surgical procedures.

Item Type:	Thesis (Thesis)
Supervisor name:	Erasmus, dr. M.E.
Supervisor name:	Gorman, Prof. J.H. and Son, Prof. W.J. van and The Perelman School of Medicine, University of Pennsylvania
Faculty:	Medical Sciences
Date Deposited:	25 Jun 2020 10:58
Last Modified:	25 Jun 2020 10:58
URI:	https://umcg.studenttheses.ub.rug.nl/id/eprint/1829

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