Clinical Case Study•Cardiac PET/CT

Epicardial CAD in a Patient with Normal Rest/Stress PET Perfusion but Abnormal Myocardial Blood Flow Reserve

Erin Stevens, CNMT, NCT  ·  Breanna Winters, R.T.(N) ARRT  ·  Deborah Hughes, MDOregon Heart Center — Salem, Oregon

Rubidium-82 PET/CTMyocardial blood flowGlobal MBFR 1.613-vessel CAD at cath

The bottom linePerfusion imaging alone would have called this study normal. Quantified myocardial blood flow reserve was globally reduced, prompting catheterization that revealed three-vessel disease with a 99% mid-RCA culprit lesion. Without the flow data, significant CAD would have gone undetected.

Case history

  • 80-year-old patient with no known coronary artery disease, presenting with symptoms suggestive of angina
  • History of paroxysmal atrial fibrillation, hypertension, and a pacemaker
  • Exercise capacity limited, so pharmacologic stress PET perfusion was ordered to evaluate symptoms

PET protocol

  • Stress agent: regadenoson
  • Isotope: Rubidium-82, 30 mCi at rest and at stress
  • Camera: GE NXi with Net Retention software for myocardial blood flow
  • Heart rate 70 BPM at rest, 93 BPM at stress; blood pressure 141/75 at rest, 132/65 at peak stress
  • Quality control: no misregistration, minimal motion artifact, excellent blood-flow QC

Myocardial blood flow reserve

Net retention model. All territories fell into the abnormal range despite visually normal perfusion.

1.66LAD

1.47LCx

1.62RCA

1.61Global

Interpretation and outcome

Myocardial perfusion was normal with a normal TID ratio, and global wall motion was normal at rest and stress. Gated ejection fractions differed between acquisitions (37% and 51%) with the patient in atrial fibrillation during gating, against a previously normal echocardiogram.

Rest flow sat in the normal range with minimal vascular variability. Stress flow rose uniformly across all three vessels but stayed below normal, producing a moderately abnormal reserve in every territory.

Given the abnormal reserve and ongoing symptoms, the patient underwent elective catheterization: moderate diffuse disease in the LAD, 80% stenosis of an obtuse marginal off the circumflex, and a 99% mid-RCA stenosis. The RCA was considered the culprit lesion. The first PCI attempt failed because the stenosis could not be crossed, and medical therapy was maximized. Symptoms persisted, and a second PCI attempt two months later was successful.

Teaching points

  • Assess all of the blood flow data — rest, stress, and reserve — not just the perfusion images
  • Abnormal flow despite normal perfusion points to epicardial and/or microvascular disease and warrants further evaluation
  • Catheterization confirmed epicardial CAD here; had it been normal, microvascular disease would be the working diagnosis
  • Risk of significant multi-vessel disease rises as MBFR falls below 2, with the highest risk below 1.6–1.7

View the full case presentationComplete slide deck with QC screens, perfusion and gated data, flow polar maps, and catheterization images.

View Case Study (PDF)

References
1. Murthy et al. Journal of Nuclear Cardiology 2018; 25:269-97.
2. Bateman et al. Journal of Nuclear Medicine 2021; 62:1599-1615.

Presented in collaboration with the American Society of Nuclear Cardiology. Case images are not for diagnostic use. This material is intended for healthcare professionals and is educational in nature; it is not clinical advice for any individual patient.

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