Objectives: We hypothesized that contrast-enhanced and dobutamine tagged magnetic resonance imaging (MRI) could investigate microvascular integrity and contractile reserve of reperfused myocardial infarction (MI) in one examination.
Background: In reperfused MI, microvascular integrity and contractile reserve are important determinants of functional recovery.
Methods: Twenty-three patients with a reperfused first MI were studied. On day 3+/-1 after MI, patients underwent tagged MRI at baseline and during infusion of 5 and 10 microg/kg/min of dobutamine followed by contrast-enhanced MRI (first pass and delayed imaging) after a bolus infusion of gadolinium-diethylenetriaminepenta-acetic acid. Tagged MRI was performed 9+/-1 weeks later (follow-up). Eighty-four transmural regions with hyperenhancement on delayed contrast-enhanced images were defined as COMB (first pass hypoenhancement) or HYPER (normal first pass signal enhancement). Percent circumferential segment shortening was measured within the subendocardium and subepicardum of each region of HYPER or COMB at baseline, peak dobutamine and follow-up.
Results: Shortening improved in COMB regions from 4+/-1% at baseline to 10+/-1% at peak dobutamine and 10+/-1% at follow-up, respectively (p<0.0003 vs. baseline for both). The HYPER regions likewise improved from 10+/-1% at baseline to 16+/-1% and 17+/-1%, respectively (p<0.0004 vs. baseline for both). Function within COMB regions was less than that of HYPER at baseline, peak dobutamine and follow-up (p<0.0003 for all).
Conclusions: Dobutamine magnetic resonance tagging and contrast enhanced MRI are complementary in assessing functional recovery after reperfused MI. Regions of delayed contrast hyperenhancement demonstrate both contractile reserve and late functional recovery. However, if these regions demonstrate first pass contrast hypoenhancement, they are associated with greater myocardial damage.