Objective - The present study was designed to compare the role of 99mTc sestamibi
sciintigraphy (SPECT) and cardiac MR (CMR) in the detection of viable myocardium and
to delineate myocardial scar tissue in patients with established chronic ischemic
heart disease.
Methods - Thirty six patients with established chronic ischemic heart disease on coronary
angiograms which was the gold standard underwent both stress CMR and 99mTc sestamibi
studies. Out of these 11 patients who had reduced end diastolic thickness < 5.5mm
alongwith wall motion abnormalities also underwent dobutamine MR (DMR) for determining
the contractile myocardial reserve.
Results- Both CMR and SPECT showed a good correlation in the detection of perfusion
defects (r=0.89) with the diagnostic region of operating characteristics being 0.97.
The sensitivity and specificity of SPECT to detect perfusion defects were 82.6% and
90.4% respectively. In comparison CMR had a sensitivity, specificity of 92.8% and
98.2% respectively in identifying such defects.It was also superior in defining transmural
infarcts(TMI) with sensitivity being 100% vs 79.3% of SPECT (p=< 0.0001) and all the
10 segments with TMI showed irreversible myocardial dysfunction on DMR. This was the
only imaging parameter that indicated myocardial non viability with a specificity
of 100%.
Conclusions - CMR is a useful diagnostic tool in the evaluation of patients with chronic
myocardial ischemia and is superior to SPECT in the detection and quantification of
myocardial infarctions. Demonstration of a TMI on CMR is a finding strongly associated
with non viability of the myocardium and may preclude the need for doing a DMR in
such cases.
Keywords
Cardiac magnetic resonance (CMR) - Single photon emission computed tomography (SPECT)
- Dobutamine magnetic resonance(DMR) - myocardial ischemia
