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In the contemporary era of primary percutaneous coronary intervention (PPCI) to treat acute ST segment elevation myocardial infarction (STEMI), the frequency and predictors of persistent microvascular obstruction (MVO) have not been elucidated. Real time myocardial contrast echocardiography (RTMCE) can be utilized to detect both the presence and extent of MVO in this setting. The goal of this study was to assess MVO frequency and severity in the current era, and how it affects outcome.
170 consecutive patients receiving successful emergent PPCI for STEMI (TIMI grade 2/3 flow) were examined with RTMCE within 24-48 hours of PPCI. RTMCE was performed with a continuous infusion or slow bolus of intravenous commercially available ultrasound contrast media and brief high mechanical index impulses to examine for both delayed microvascular replenishment and abnormal plateau intensity within the infarct zone (IZ). Patients were divided into 3 groups: Group 1 with normal microvascular flow (MVF) within the IZ, Group 2 with delayed replenishment but normal plateau intensity, and Group 3 both delayed replenishment and abnormal plateau intensity (MVO). Clinical and angiographic predictors of persistent MVO were determined using Odds Ratios (OR). Event free survival (EFS) from death, heart failure, recurrent infarction, and defibrillator placement was determined by Kaplan Meier estimates.
Mean age was 59±12 years (79% male). Prevalence of hypertension, hyperlipidemia, DM, smoking, history of MI and door to balloon times were not different between groups, but 37% had normal MVF (Group I), 29% had only delayed replenishment (Group 2), and 35% patients had MVO (Group 3). Age (OR 1.2;CI 1.1-1.4) and LAD infarct (OR 7.3;CI 3.6-15.6) were independent predictors of MVO. One year event rates were 27% in Group 3 compared to 8% in Group 1 and Group 2. The presence of MVO was associated with significantly lower EFS when compared to Group I and II patients (p=0.008).
In the contemporary era of successful PPCI for STEMI, MVO persists in over one third of the patients, especially following LAD infarction. The presence of MVO by RTMCE identifies patients at highest risk for adverse outcomes.
IMAGING: Imaging: Non-Invasive