Relationship between myocardial blush grades, staining, and severe microvascular damage after primary percutaneous coronary intervention a study performed with contrast-enhanced magnetic resonance in a large consecutive series of patients.
BACKGROUND
Although angiographic perfusion has been traditionally evaluated by myocardial blush grade (MBG), pathophysiologic features underlying different MBG and the persistent blush, traditionally called staining, have been poorly explained. The aim of the study was to evaluate the correlation between MBG and morphologic aspects on cardiac magnetic resonance (CMR).


METHODS
Myocardial blush grade and morphologic aspects on contrast-enhanced CMR, with special reference to staining phenomenon and persistent microvascular damage (PMD), were evaluated in a consecutive series of patients with acute myocardial infarction (AMI) treated by primary percutaneous coronary intervention.


RESULTS
A total number of 294 AMI patients were enrolled and classified into 2 groups, that is, MBG 0/1 (115, 39%) and MBG 2/3 (179, 61%), according to the angiographic profile. By comparing MBG 0/1 versus MBG 2/3 patients, the former exhibited a larger enzymatic infarct size (P < .001) and a greater infarct size index (P < .001) and PMD (P < .001). In the MBG 0/1 group, a subgroup of 51 patients with staining phenomenon (MBG 0 staining) was also identified, with a worse CMR profile as PMD (P < .001). Multivariate analysis confirmed the strong association between MBG 0/1 and mean number of segments with transmural necrosis (odds ratio 1.62, 95% CI 1.17-2.24, P = .003) and PMD index (odds ratio 3.13, 95% CI 1.19-8.29, P = .021).


CONCLUSIONS
In AMI patients treated by primary percutaneous coronary intervention, angiographic parameters of impaired reperfusion correlate with PMD as detected by contrast CMR. Among patients with MBG 0, the presence of the so-called staining phenomenon identifies a subgroup of patients with more severe PMD.