Influence of time-to-treatment, TIMI-flow grades, and ST-segment resolution on infarct size and infarct transmurality as assessed by delayed enhancement magnetic resonance imaging.

AIMS: The time-to-treatment, ST-segment resolution (STR), and TIMI-flow might be associated with infarct size (IS) and infarct transmurality in humans. Delayed enhancement magnetic resonance imaging (DE-MRI) has excellent spatial resolution to uncover these relations. METHODS AND RESULTS: This study analysed 135 ST-elevation myocardial infarction (STEMI) patients randomized to prehospital fibrinolysis or prehospital initiated facilitated percutaneous coronary intervention (PCI). Reperfusion-times, 90 min STR, and TIMI-flow grades were assessed. IS at 6-month follow-up was determined as percentage of left ventricular mass (% LV). Transmurality was defined if segments exceeded > 50% DE. The median time-to-treatment was 93 min [interquartile range (IQR) 66.5; 158.8] for prehospital fibrinolysis and 85 min (IQR 60.0; 143.5) for facilitated PCI patients (P = 0.35). In facilitated PCI, the pre-interventional TIMI-flow correlated with IS [TIMI 0-1 10.8% LV (IQR 7.6; 17.3) vs. TIMI 2-3 3.9% LV (IQR 0.9; 9.6); P = 0.002] and segments with transmurality 1.5 (IQR 0.0; 3.0) vs. 0 (IQR 0.0; 1.5; P = 0.02). In a multivariable model, incomplete STR < 70% was the strongest predictor of high IS [odds ratio (OR) 6.96, P < 0.001] and transmurality (OR 5.71, P < 0.001) followed by time-to-treatment delay (OR/30 min, 1.24; P = 0.01 for high IS and 1.23, P = 0.01 for transmurality). CONCLUSION: Time-to-treatment, STR, and TIMI-flow correlate with IS and transmurality underlining the assumed pathophysiological link between early flow restoration and perfusion in the infarct-related artery.

Reproducibility of chronic and acute infarct size measurement by delayed enhancement-magnetic resonance imaging.

OBJECTIVES: The aim of this study was to evaluate the reproducibility of acute and chronic infarct size (IS) by delayed enhancement (DE) magnetic resonance imaging (MRI). BACKGROUND: Infarct size measurements can be used as surrogate end point to reduce the sample size in studies comparing different reperfusion strategies in myocardial infarction (MI). Delayed enhancement MRI is a rather new technique, and so far infarct IS reproducibility has not been established appropriately. METHODS: In 21 patients (10 acute MI and 11 chronic MI), IS was assessed repeatedly on consecutive days by DE-MRI. Reproducibility, interobserver, and intraobserver variabilities were assessed and compared by the Bland-Altman method. RESULTS: Acute and chronic IS were 17.1 +/- 19.6% (range 5.1% to 69.8%) of LV mass (%LV) and 16.9 +/- 9.9 %LV (range 2.0% to 36.0%), respectively. Infarct size difference (bias) between scan I and scan II was -0.5 %LV, and limits of agreement were +/-2.4 %LV. Mean bias (-0.7 %LV) and limits of agreement (+/-3.2%) were slightly higher for acute in comparison with chronic MI with -0.4 +/- 1.3 %LV. Intraobserver and interobserver variability was low with a mean bias of 0.3 %LV (limits of agreement +/- 1.7 %LV) and -0.7 %LV (limits of agreement +/- 2.2 %LV), respectively. CONCLUSIONS: Infarct size measurement by DE-MRI is an excellent tool for IS assessment, owing to its excellent repeatability in chronic and acute MI. It has therefore the potential to serve as a surrogate end point to uncover advantages of new reperfusion strategies.

Comparison of pre-hospital combination-fibrinolysis plus conventional care with pre-hospital combination-fibrinolysis plus facilitated percutaneous coronary intervention in acute myocardial infarction.

AIMS: Early and complete reperfusion is the main treatment goal in ST-elevation myocardial infarction (STEMI). The timely optimal reperfusion strategy might be a pre-hospital initiated pharmacological reperfusion with subsequent facilitated percutaneous coronary intervention (PCI). This approach has been compared with pre-hospital combination-fibrinolysis only to determine whether either one of these methods offer advantages with respect to final infarct size. METHODS AND RESULTS: Patients with STEMI were randomized to either pre-hospital combination-fibrinolysis (half-dose reteplase+abciximab) with standard care (n=82) or pre-hospital combination-fibrinolysis with facilitated PCI (n=82). Primary endpoint was the infarct size assessed by delayed enhancement magnetic resonance. Secondary endpoints were ST-segment resolution at 90 min and a composite of death, re-myocardial infarction, major bleeding, and stroke at 6 months. The infarct size was lower after facilitated PCI with 5.2% [interquartile range (IQR) 1.3-11.2] as opposed to 10.4% (IQR 3.4-16.3) after pre-hospital combination-fibrinolysis (P=0.001). Complete ST-segment resolution was 80.0% after facilitated PCI vs. 51.9% after pre-hospital combination-fibrinolysis (P<0.001). After facilitated PCI, there was a trend towards a lower event rate in the combined clinical endpoint (15 vs. 25%, P=0.10, relative risk 0.57, 95% CI 0.28-1.13). CONCLUSION: In patients with STEMI, additional facilitated PCI after pre-hospital combination-fibrinolysis results in an improved tissue perfusion with subsequent smaller infarct size as opposed to pre-hospital combination-fibrinolysis alone. This translates into a trend towards a better clinical outcome.