José Fernando Rodríguez Palomares, MD, University Hospital Vall d’Hebron, Barcelona, Spain, shared preliminary results from the PROMISE trial [NCT00781404] in patients with STEMI in which transmural infarction was identified by cardiac magnetic resonance imaging (CMR) early after STEMI. At the 6-month follow-up, the results demonstrated a decreased extent of infarction in many affected myocardial segments, with significant improvements in their contractile function.

According to Prof Rodríguez Palomares, in patients with acute myocardial infarction, the extent of transmural necrosis, as determined by CMR in the early post-STEMI phase, has been established as an excellent predictor of improvement in myocardial contractile function. However, data from some studies have suggested that the extent of transmural necrosis can be overestimated during the acute phase because of the presence of edema in the infarcted tissue. Prof Rodríguez Palomares noted that after percutaneous coronary intervention, the recovery of dysfunctional myocardial segments that have an intermediate extent of transmural necrosis is variable, is difficult to predict, and may be related to the contractility of the remaining viable but stunned myocardium. He indicated that additional studies have also addressed this issue in chronic ischemic heart disease, showing that low-dose dobutamine test CMR is superior to extent of infarction for the prediction of functional recovery of myocardial contraction.

With this in mind, Prof Rodríguez Palomares and colleagues conducted the PROMISE trial to investigate the accuracy of the extent of transmural infarction in predicting the presence of contractile reserve and recovery of myocardial function at 6 months post-STEMI.

The study enrolled 95 patients with an acute STEMI. Following successful primary angioplasty, participants underwent CMR and a dobutamine stress echocardiogram during the first week and at 6-month follow-up.

The transmural extent of infarction in myocardial segments was determined by CMR. The researchers evaluated a total of 1520 myocardial segments and categorized transmural infarction as an extent of necrosis > 50%. They determined peak longitudinal systolic strain (SS) and systolic strain rate (SSR) at baseline and after infusion of 10 µg/kg/min of dobutamine in 16 myocardial segments in each participant (except the apex, segment 17).

The results showed a decrease in deformation parameters as the extent of transmural necrosis increased: SS and SSR at baseline, after infusion of 10 µg/kg/min of dobutamine, and at 6-month follow up, were decreased with increased extent of transmural infarction. However, at 6 months, the extent of necrosis was significantly decreased, even in transmural infarcts (P < .001). Eighty percent of myocardial segments with 50% to 75% infarction, and 48% of those with > 75% infarction in the acute phase demonstrated contractile reserve and improvement in myocardial contractile reserve, with concomitant decrease in the extent of transmural necrosis.

Prof Rodríguez Palomares therefore concluded that assessment of the transmural extent of a myocardial infarct early post-STEMI does not accurately predict functional recovery at 6 months and therefore should not be relied upon as an accurate short-term surrogate marker of improvement in myocardial contractile function.