Danish Medical Bulletin - No. 3. September 2004. Vol. 51 Page 302.

ABSTRACT OF PhD DISSERTATION

Ischaemic myocardial preconditioning

Haemodynamic and motility aspects studied in pigs

Jette Scheby Berg

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This PhD dissertation was accepted by the Faculty of Health Sciences at the University of Aarhus, and defended on June 4, 2004.

Official opponents: Christian Aalkjær, Guro Valen, Henning Rud Andersen.

Supervisors: Daniel A. Steinbrüchel and J. Michael Hasenkam.

Correspondence: Barthsgade 1, 3th, DK-8200 Aarhus N.
E-mail:jberg@ki.au.dk

Dan Med Bull 2004;51:302.

ABSTRACT

This dissertation is based on experiments conducted during my research fellowship at the Clinical Institute, University of Aarhus, and Department of Cardiothoracic and Vascular Surgical Research, Aarhus University Hospital, Skejby Sygehus, in the period between 2000 and 2004.

In off-pump coronary artery bypass operations (OPCAB) the myocardium is exposed to varying degree of warm ischaemia during anastomosis formation. Myocardial protection against ischaemic damage is important to dimish myocardial damage. In this context ischaemic preconditioning (IPC) is a potent cardio-protecting procedure with respect to infarct size reduction. The aim of the study was to evaluate the effect of IPC on the reactive hyperaemia (RH), coronary vascular resistance (CVR), reversible myocardial dysfunction (stunning) and haemodynamic function in OPCAB surgery, which is partly unsolved.

Two OPCAB pig models were created to allow investigation of the following endpoints: 1) RH measured by use of a transit time flow probe positioned on the left anterior descending coronary artery. 2) CVR measured by simultaneous measurement of the coronary blood flow and the myocardial perfusion pressure, measured as the myocardial arterio-venous pressure difference. 3) Stunning in area at ischaemic risk as well as global left ventricular function measured by sonomicrometry crystals positioned on the left ventricle.

IPC reduced the RH after index ischaemia. The CVR in the early reperfusion period was elevated in the IPC group compared to control animals. Stunning developed equally in both groups and there was no difference in haemodynamic performance between the groups.

In conclusion: IPC preserves the myocardial metabolism after an OPCAB comparable ischaemic episode, measured as reduced RH. This dissertation does not clarify why the CVR is elevated in the early reperfusion period after OPCAB. The absent effect of IPC on stunning and haemodynamic parameters corresponds to previous findings from other studies, and in this context indicates a proper functioning model to further investigations in stunning.
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