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Assessment of myocardial viability

Non-Invasive Imaging


Cardiac imaging has become a sub-speciality in its own right with considerable exposure at the Congress for in the four main techniques: echocardiography, nuclear cardiology, magnetic resonance imaging and X-ray computed tomography. There is overlap between the techniques in the information that they provide but the specialist cardiology centre will need access to them all.

This session continued the Congress tradition of featuring case based presentations with images read and discussed blindly by an expert panel. The simplest of cases can provide a focus for an educational discussion and it can be valuable to see how the imaging expert approaches interpretation and management of unknown cases. The theme of this session was the assessment of myocardial viability, a topic that is primarily of interest in the patient with ischaemic heart disease presenting with symptoms of impaired ventricular function.

Hans Marc Siebelink from Leiden showed the case of a 63 year old man who presented with an anterior ST elevation myocardial infarction. Angiography showed an acutely occluded LAD and a chronically occluded RCA with additional circumflex and marginal disease. The LAD was opened but LV function remained impaired. MRI was used to assess function and viability and this showed thinning and akinesis of the LAD territory, lesser thinning and akinesis of the inferior wall and preserved function only of the lateral wall. Late gadolinium enhancement confirmed transmural infarction of the LAD territory and the inferior wall.

A discussion point was whether the pattern of late gadolinium enhancement contributed anything more than the pattern of thinning and functional impairment, but it was agreed that the high resolution of the images of fibrosis were compelling evidence of the pattern of infarction. There was less agreement on where the chronically occluded right coronary territory was and whether there was any point in revascularisation but the denouement was that the patient was managed conservatively and with defibrillator implantation. The message was that imaging was able to guide appropriate management by demonstrating the lack of viable myocardium in at least two of the coronary territories.

The second case was presented by Heikki Ukkonen from Turku. A 79 year old lady presented with palpitation and episodes of syncope. She was found to have self-limiting episodes of ventricular tachycardia and also of atrial fibrillation and severely impaired left ventricular function. The question was how to investigate her arrhythmia and it was agreed that, although primary or secondary muscle disorders should be considered, ischaemic disease was the most important underlying cause to be excluded. There was some discussion whether non-invasive imaging would be able to differentiate the diagnosis and it was agreed that there might be some virtue in the non-invasive approach but she went straight to coronary angiography, which showed severe three vessel disease.

The next important issue was therefore to decide the pattern of myocardial viability and whether ischaemia might be the underlying cause of her arrhythmia rather than re-entrant circuits around areas of scarring. Although any of the imaging techniques could have been helpful, gated FDG imaging of glucose metabolism showed excellent quality imaging with only relatively minor areas of scarring, and hence a presumed substrate for ischaemia-driven arrhythmias. Although some of the panel would have preferred to see objective evidence of myocardial ischaemia, bypass grafting was performed and the arrhythmias were abolished. The message was that PET imaging of myocardial viability contributed significantly to successful management.

One topic that the panel did not have time to debate was the definition of myocardial viability. Some use the term to mean dysfunctional myocardium that will improve in function with revascularisation and some use it simply to mean myocardium that is alive, leaving myocardial function and ischaemia undefined. The latter approach is technically correct although the former is also common usage. Whichever, the session made it clear that imaging has a great deal to offer in describing myocardial viability, function, ischaemia and metabolism and that the management of complex ischaemic heart disease can benefit from the objective and often quantitative assessment provided by modern imaging techniques.

References


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SessionTitle:

Assessment of myocardial viability

The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.