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- CABG, coronary artery bypass graft surgery
- CASS, coronary artery surgery study
- IABP, intra-aortic balloon pump
- LVEF, left ventricular ejection fraction
- NYHA, New York Heart Association
- WMS, wall motion score
In the early 1980s Rahimtoola reviewed the results of coronary bypass surgery trials1 and identified patients with coronary artery disease and chronic left ventricular dysfunction that improved upon revascularisation. The results of medical treatment for ischaemic cardiomyopathy have been poor. Coronary artery bypass grafting provides superior long term survival, but may be associated with a high operative mortality and significant morbidity for certain patient subgroups with heart failure and very low left ventricular ejection fraction (LVEF). The potential benefits of revascularisation are to reduce the ischaemic burden, to reduce the arrhythmic potential, to reduce maladaptive growth, and to restore the coordinated movement in dysfunctional myocardial segments.
Data from the coronary artery surgery study (CASS) registry for patients with LVEF < 35% involved 651 patients.23 The five year survival was significantly better in surgical patients (68%) than in the medical group (54%). The contrast became more pronounced in patients with LVEF < 26% whose five year survival was 63% with surgery, but 43% with medical treatment. This information is the cornerstone of our current approach to patients with coronary artery disease and heart failure. The difficulties in selecting patients and in interpreting both metabolic and functional scans, particularly when they are discordant, will be discussed.
PREOPERATIVE ASSESSMENT
Case selection is arguably the most important ingredient for success in coronary artery surgery for ischaemic cardiomyopathy. We commonly perform both extended thallium perfusion scans to assess coronary flow and dobutamine stress echocardiography to assess function. When both modalities are in agreement either negative or positive, the clinical decision is straightforward. Unfortunately, in approximately 20–45% of cases the tests disagree and the results of coronary artery bypass grafting in this setting are, not surprisingly, unpredictable.
A common clinical problem is to establish the relevance of …