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A 67 year old man underwent 99mTc-sestamibi single photon emission computed tomography (SPECT) for evaluation of atypical epigastric pain. His baseline 12 lead ECG revealed anterior ST elevation (1.5 mm) at rest without Q waves. During exercise SPECT imaging the patient developed ST segment elevation over leads V2—V4 (7 mm in V3) at 4.2 minutes into a Bruce protocol. The ST segment changes persisted for two minutes. Stress (S) and rest (R) studies were performed on separate days.
The figure shows a “bulls-eye” plot of myocardial perfusion and wall thickening (derived from gated images). The anteroseptal left ventricular (LV) wall showed > 90% reduction of perfusion following stress, suggesting transmurality of the ischaemic region. This was associated with a large fall in left ventricular ejection fraction (EF) (from 67% to 47%) and gross increase in left ventricular volumes even one hour after stress (when images were acquired). Persistent wall thickening abnormality was present at one hour after stress suggesting post-ischaemic stunning. Normalisation of perfusion was associated with improvement in wall thickening and LV function at rest (on a separate day). Coronary angiography revealed > 90% lesions in proximal and dominant left anterior descending artery, with diffuse right coronary artery disease (< 50%).
Gated SPECT clearly demonstrates the value of simultaneous assessment of perfusion and function, which reflects the functional significance of the myocardial ischaemia. The mechanism of transient ST segment elevation is likely to be the result of transmural ischaemia leading to severe haemodynamic derangement caused by myocardial stunning.
