Coronary steal: Revealing the diagnosis with quantitative cardiac PET/CT

Excerpt

A 68-year-old male was evaluated at our chest pain unit because of recent onset exertional anginal chest pain. The symptoms commenced after an initial episode of angina that had lasted for several hours. The electrocardiogram (ECG) showed signs of a recent inferior myocardial infarction (Figure 1) after which the patient was treated with antiplatelet agents, a statin, and beta-blockers. To further evaluate the extent of coronary artery disease and ischemia, a cardiac PET/CT was performed. The imaging protocol consisted of a 64-slice CT coronary angiography (CTCA) and myocardial perfusion measurements using oxygen-15-labeled water PET during rest and pharmacologically induced vasodilation (adenosine). During vasodilation, the patient reported anginal chest pain and the ECG displayed ST-segment elevation in the Q-wave leads suggestive of transmural inferior ischemia, although it should be noted that stress-induced ST segment elevation in Q-leads may also occur in the absence of ischemia. Heart rate and blood pressure did not change appreciably during the stress study, and the ECG abnormalities and symptoms resolved immediately after termination of adenosine infusion. CTCA revealed an occlusion of the right coronary artery (RCA) with collateral filling of the distal segment (Figure 2). PET images displayed a mild resting perfusion defect in the inferior wall (Figure 3). During hyperemia, the perfusion defect expanded toward the inferior distal wall and part of the septum and lateral wall. Of interest, quantitative perfusion analysis displayed a restflow in the RCA perfusion territory of 0.70 mL/minute/g of perfusable tissue, which paradoxally decreased during hyperemia to 0.49 mL/minute/g, yielding a flow reserve of 0.7 (Figure 4). The patient was referred for invasive coronary angiography, which confirmed the occlusion of the RCA (Figure 5). In addition, a significant stenosis of the margo obtusis branche of the circumflex coronary artery was detected, compatible with the reduced flow reserve in the circumflex perfusion territory (Figure 4). Through a percutaneous coronary intervention, both RCA and circumflex lesions were stented and the patient was discharged free of symptoms.

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