The prevalence of microvascular obstruction in acute myocardial infarction: importance of ST elevation, infarct size, transmurality and infarct age

Results The population consisted of 147 (56%) patients with STEMI, 2 (0.8%) with left bundle branch block, and the remaining 117 (44%) with non-STEMI. The mean age was 59±13 years and 68% were male. The overall observed prevalence of MO was 53%. IS and transmurality were significantly larger in patients with MO than without (24% vs 7%, p 25%) or transmural extent was high (upper tertile, >80%) the prevalence of MO was similar (93% vs 92%, p=0.9; and 90% vs 85%, p=0.5, respectively). The prevalence of MO was dependent on both IS and


Objective
To assess the prevalence of microvascular obstruction (MO) by delayed-enhancement cardiac magnetic resonance (DE-CMR) in patients with first acute myocardial infarction (AMI) and describe its relationship with type of infarction, infarct size (IS), transmurality, and infarct age.

Background
MO has been associated with poor LV remodeling and adverse prognosis. The clinical and CMR characteristics of MO have predominantly been examined in patients with ST-segment elevation MI (STEMI). There are no prior studies that have included both STEMI and non-STEMI patients to allow direct comparison of the prevalence of MO. Additionally, the relationship of MO with IS, transmurality, and infarct age are incompletely understood.

Methods
We studied 266 consecutive patients from 2 centers (Duke and Maastricht University) with first AMI (elevated biomarkers and angiographically confirmed CAD). Baseline characteristics and the presence of STsegment elevation (2-contiguous leads ≥0.2 mV in men and ≥0.15 mV in women in leads V2-V3 and/or ≥0.1 mV in other leads) were recorded. Cine and DE-CMR were performed at 4±3 days. IS and transmural extent were measured by planimetry.

Results
The population consisted of 147 (56%) patients with STEMI, 2 (0.8%) with left bundle branch block, and the remaining 117 (44%) with non-STEMI. The mean age was 59±13 years and 68% were male. The overall observed prevalence of MO was 53%. IS and transmurality were significantly larger in patients with MO than without (24% vs 7%, p<0.0001; and 83% vs 56%, p< 0.0001, respectively). The prevalence of MO was higher in STEMI than non-STEMI (69% vs 31%, p<0.0001, Figure 1), however, when IS was large (upper tertile, >25%) or transmural extent was high (upper tertile, >80%) the prevalence of MO was similar (93% vs 92%, p=0.9; and 90% vs 85%, p=0.5, respectively). The prevalence of MO was dependent on both IS and 1 Duke University, Durham, NC, USA Full list of author information is available at the end of the article Figure 1 The prevalence of MO for NSTEMI and STEMI in all patients, patients with IS >25% (upper tertile) and patients with transmural extent (TE) >80% (upper tertile).

Conclusions
Microvascular obstruction is more than twice as common in patients with STEMI than non-STEMI, however, the prevalence of MO is similar when accounting for infarct size and transmurality. Only larger infarct size, greater extent of transmurality and earlier infarct age are independent predictors of MO. Van Assche et al. Journal of Cardiovascular Magnetic Resonance 2011, 13(Suppl 1):P147 http://jcmr-online.com/content/13/S1/P147