Case 13

Published on 02/03/2015 by admin

Filed under Internal Medicine

Last modified 22/04/2025

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Case 13

A 74-year-old man with hypertension and diabetes was referred for preoperative assessment prior to bladder surgery. He reports a “normal” stress test 14 years ago.

He describes severely reduced functional capacity (<4 METs), but he denies angina. Dipyridamole PET MPI was requested for preoperative risk assessment.

12-Lead ECG

The baseline ECG demonstrates normal sinus rhythm, right bundle branch block, and left anterior fascicular block.

PET Images

The peak stress PET images demonstrate a mild defect in the apical region. Mild defect reversibility is evident on resting images, suggestive of ischemia. Also note that the left ventricular cavity is much larger on peak stress images compared to resting images, with a computed stress/rest left ventricular cavity ratio (SRLVCR) of 1.39.

Quantitative Polar Map

When the perfusion pattern is compared to a normal rubidium-82 (⁸²Rb) perfusion database, the perfusion defect in the apical region is identified as abnormal. However, the extent of the perfusion abnormality is extremely limited, confined to only 1% of the LV myocardium. Quantitative measurements of absolute myocardial blood flow (e.g., in mL/min/g) were not performed on this study.

Gated PET Images

The gated PET images demonstrate normal myocardial systolic thickening in all regions. The resting and peak stress LVEF was 70% and 54%, respectively. A decrease in LVEF at peak dipyridamole stress (compared to resting LVEF) is an abnormal finding on gated PET imaging; it is commonly observed in patients with severe single-vessel disease, multivessel disease, or left main disease.

Despite the limited extent of ischemia detected by perfusion imaging, the elevated SRLVCR and the abnormal decline in LVEF at peak dipyridamole stress prevented the study from being designated as a “low-risk” abnormal study. Therefore, coronary angiography was recommended.

Coronary Angiography

Cardiac Catheterization

Contrast left ventriculography showed normal left ventricular systolic function.

Coronary Angiography

Coronary angiography revealed mild diffuse left main disease, moderate diffuse LAD stenoses, 80% proximal circumflex stenosis, 50% ostial RCA stenosis, and 30% mid-RCA stenosis. Percutaneous intervention of the proximal circumflex artery stenosis was recommended by the interventional cardiologist, but drug-eluting stent placement was deferred until after bladder surgery (to avoid the risk of stent thrombosis if interruption of clopidogrel therapy would be required perioperatively).

Teaching Points: Detection of Balanced Ischemia

1. The presence of multivessel CAD (and the extent and severity of ischemia) can be underestimated by techniques that measure only “relative” myocardial perfusion.

2. Elevated stress/rest left ventricular cavity ratio (SRLVCR) is a marker of extensive ischemia. Elevated SRLVCR is an important “high-risk” marker on PET MPI.

3. A decline in LVEF from rest to peak stress on gated PET images is a marker of extensive ischemia and predicts the presence of severe (often multivessel or left main) CAD.

4. Measurement of absolute myocardial blood flow with ⁸²Rb PET will improve our ability to identify patients with balanced ischemia due to diffuse multivessel disease.

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