Contrast-enhanced cine cardiac MR detects impairment of coronary microvascular perfusion in patients after acute myocardial infarct

Purpose

To prospectively compare contrast-enhanced (CE) cine steady-state free precession (SSFP) magnetic resonance imaging (MRI) to assess microvascular obstruction (MVO) with delayed-enhancement (DE) MRI, and to evaluate the association between MVO size and angiographic perfusion scores after primary percutaneous coronary angioplasty.

Materials and methods

The study was HIPAA compliant and was approved by the institutional review board. All participants gave written informed consent. Twenty one patients (19 men; mean age, 59 ± 12 years) were examined with contrast-enhanced MRI after presentation and repeated at 6 months in 15 patients. TIMI Flow Grade (TFG), corrected TIMI Frame Count (cTFC), TIMI Myocardial Perfusion grade (TMPG), MVO, infarct size, and left ventricular ejection fraction (EF) were assessed.

Results

MVO zones of decreased signal intensity were observed in 18 of 21 (86%) examinations on CE cineSSFP MR imaging and 17/21 (80%) examinations on DE MRI (P = NS). The size of CE cineSSFP hypointense zone was comparable to the MVO size measured by DE MRI (3.3 ± 3.1% versus 2.9 ± 3.0% of the myocardial mass; P = NS). MVO size correlated well with infarct size (r = 0.76 for CE cineSSFP and r = 0.83 for DE MRI) and EF at follow-up (r = -0.64 for CE cineSSFP and r = -0.58 for CE MRI). TFG 3 was present following percutaneous coronary intervention (PCI) in 20/21 (95%) patients. Abnormal post-PCI TMPG (0/1/2) was present in 11/21 (50%) of subjects and was associated with MVO size on CE cineSSFP (3.6 ± 2.2% with abnormal TMPG versus 0.8 ± 0.7% of the myocardial mass (LV) with TMPG 3; P < 0.05) and DE MRI (4.4 ± 2.6% with abnormal TMPG versus 1.3 ± 1.3% LV with TMPG 3; P < 0.05). There was no association between abnormal post-PCI TFC (≥ 40) and MVO size on CE cineSSFP (3.5 ± 2.5% with abnormal TFC versus 1.8 ± 2.3% LV with TFC < 40, P = 0.26) and DE MRI (2.9 ± 2.0% with abnormal TFC versus 1.5 ± 2.3% LV with TFC < 40, P = 0.29). Abnormal post-PCI TMPG was also associated with greater relative infarct size (18.8% vs. 9.6%, P = 0.04). CEcineSSFP MR had a comparable contrast-to-noise ratio (CNR) to DE MRI for depicting MVO zones (P = NS).

Conclusion

CE cineSSFP hypointense zone depicts the microvascular obstruction region in close agreement with the DE MRI approach, and correlates with infarct size and global LV function at follow-up. TMPG seems to translate better the microvascular integrity compared to cardiac MRI measures of MVO.