Case presentation

A 66-year-old man without prior cardiac history developed progressive dyspnea on exertion, culminating in rest chest pain. In the emergency department, the electrocardiogram was normal, but he was found to have an elevated troponin I (5.77 ng/mL), and he was admitted with the diagnosis of a non-ST segment elevation myocardial infarction. He became pain-free on nitrates, beta-blockers, low-molecular-weight heparin, aspirin, and clopidogrel. Past medical history was notable for hypertension, dyslipidemia, prior tobacco abuse, adenomatous colon polyps, benign prostatic hypertrophy, and hypothyroidism. Troponin I subsequently rose to 16.5 ng/mL and he was referred for cardiac catheterization the next day.

Cardiac catheterization

There was a severe stenosis of a small, distal branch of the right coronary artery, which appeared to represent the culprit lesion (Figure 38-1 and Video 38-1). The operator considered this artery too small and the lesion too distal for intervention. Atherosclerotic plaque without significant narrowing was seen in the mid-right coronary artery and the first obtuse marginal artery. A long, moderate stenosis affected the proximal to midsegment of the left anterior descending (LAD) artery at a bifurcation with a large diagonal branch (Figure 38-2 and Video 38-2). The left ventriculogram revealed normal function and no specific wall motion abnormalities. Concerned about the lesion of intermediate severity seen in the left anterior descending artery, the physician decided to assess the lesion’s significance by measuring fractional flow reserve, or FFR. Thus, a guide catheter was engaged in the left coronary artery and, after administering a bolus of 50 U/kg of unfractionated heparin, the operator advanced a pressure wire to the distal LAD. The wire transducer was placed distal to the LAD lesion and simultaneous distal coronary pressure and aortic pressure from the guide catheter tip were sampled after maximum coronary vasodilatation was achieved with 100 mcg of intracoronary adenosine (Figure 38-3). Fractional flow reserve was calculated as the ratio of the mean coronary pressure distal to the stenosis (62 mmHg) to mean pressure of the aorta at the guide catheter (76 mmHg) during maximal hyperemia. This ratio calculated to an FFR of 0.82. Thus, the lesion was determined to be a non–flow-limiting stenosis. Based on the results of the angiogram and the FFR determination, it was decided to treat him medically.