Vasodilator stress myocardial perfusion examination discrepancy with coronary angiography: clarification with intravascular ultrasound.

Clinical presentation. On presentation, a 58-yearold man had symptoms of chest pain suggestive of unstable angina. He had negative troponins and no electrocardiographic ST-segment changes. After stabilization, he was referred for adenosine vasodilator rest/ stress gated myocardial perfusion testing. Imaging. The imaging study was positive for multivessel disease with significant reversibility of perfusion from stress to rest noted in both the septum and inferior walls (Figure 1). Quantitative perfusion scintigraphy revealed a summed stress score of 23 and a summed rest score of 0, indicative of high risk for both cardiac death and nonfatal myocardial infarction (Figure 2). Coronary angiography revealed obstructive disease in both the left anterior descending artery (LAD) and right coronary artery (RCA) distributions. Specifically, there was an 80% proximal LAD lesion (not shown), and a 40% to 50% indeterminate lesion in the distal RCA (Figure 3). This RCA lesion was determined to be 43% stenotic by quantitative coronary angiography.Percutaneous revascularization of the LAD was carried out with primary stenting. The patient had an excellent final result with 0% residual lesion, TIMI 3 flow, and preservation of all branches of the LAD. Clinical dilemma. Although the angiographically significant LAD lesion presented no problem in management, the indeterminate RCA lesion was discrepant with the result of the adenosine vasodilator rest/stress myocardial perfusion examination. Further imaging, diagnosis, and treatment. To further evaluate the significance of the indeterminate RCA lesion noted on angiography, a decision was made to perform intravascular ultrasound (IVUS) immediately after stenting the LAD. The angiographically indeterminate lesion showed a severe 80% area stenosis of the distal RCA (Figure 4). The lesion was treated with primary stent implantation. An excellent final result was obtained with 0% residual lesion, TIMI 3 flow, and preservation of all branches. The patient was discharged the following day in stable condition. He has been followed up for over 1 year. He remains asymptomatic and gainfully employed as a truck driver. Discussion. This case demonstrates an example of a discrepancy in stenosis severity between nuclear imaging and visual assessment/quantitative coronary angiography, as well as the subsequent use of IVUS for clarification of the conflicting results. Several reports have suggested that angiography has several limitations and may underestimate intermediate lesions (50%-75% stenosis). Iodinated angiography demonstrates only the contrast inside the vessel lumen, which can underestimate original vessel size. This inaccuracy is due to the atherosclerosis positive remodeling effect, in that the segments proximal and distal to the stenosis used for reference are affected by atherosclerosis themselves. Two studies demonstrated that the use of IVUS altered the management strategy in approximately 20% of patients undergoing angiography before a coronary intervention. In conclusion, the information gained from nuclear imaging influenced us to scrutinize the angiographic results of an intermediate lesion more closely with IVUS, yielding clinically useful information about vessel diameter and minimum lumen area. The use of IVUS in selected angiographic studies clarifies indeterminate angiographic lesions and helps optimize revascularization plans. In our case a flow marker (myocardial perfusion imaging) was more accurate than the conventional anatomic imaging (angiography).