Cardiology>>>>>CT, CMR, And Nuclear Imaging
Question 48#

The patient is a 62-year-old man with CAD risk factors including diabetes (16 years), hypertension, family history of CAD, and obesity. The patient had a silent inferior MI 2 years earlier detected by ECG. The patient is now sent for preoperative evaluation for bilateral knee surgery. The patient has no CP with exertion; however, his exercise capacity is limited by knee pain. He does occasionally have mild post-prandial dyspnea. His medications include insulin, a statin, an angiotensin-converting enzyme inhibitor, a βblocker, and an aspirin. A pharmacologic dual-isotope (Thal/Tc) scan was performed and is shown in Figure below.

A pharmacologic (adenosine) dual-isotope (Thal/Tc) scan with the stress images displayed on top with the resting images below.

The gated images showed an LVEF of 42% with a wall motion abnormality in the inferolateral wall. There were no ECG changes or symptoms during the adenosine infusion. The rest and post-stress images demonstrate

A. Scarred RCA/LCx territory
B. Scarred LAD territory
C. Normal test with artifacts
D. Scar and ischemia in the LCx/RCA territory
E. Scar and ischemia in the LAD territory

Correct Answer is D

Comment:

Scar and ischemia in the LCx/RCA territory. The full interpretation of the study was that there was marked GI activity in the rest images, but there was also a severe resting perfusion defect involving the basal and midinferolateral segments. Although GI activity can make the basal and midinferior segments difficult to interpret at rest, the post-stress images clearly show that the defect now involves the entire inferolateral and inferior walls, showing infarct with peri-infarct ischemia in the LCx/RCA territory. Cardiac catheterization demonstrated a total obstruction of the proximal LCx (a dominant LCx) with collaterals from the RCA and LAD. There were no obstructions in the RCA and LAD. Important points from this case include that diabetics are at high risk for CAD and clinical parameters do not predict ischemia (from the detection of ischemia in asymptomatic diabetes (DIAD) trial). Myocardial perfusion imaging can be performed safely post MI to assess infarct size and the amount of myocardium at risk. It is also a good test to assess the adequacy of collateral blood flow.