Impact of symptom-to-reperfusion-time on transmural infarct extent and left ventricular strain in patients with ST-segment elevation myocardial infarction: a 3D view on the wavefront phenomenon

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Abstract
We examined the association between the symptom-to-reperfusion-time and cardiovascular magnetic resonance (CMR)-derived global strain parameters and transmural infarct extent in ST-segment elevation myocardial infarction (STEMI) patients. The study included 108 STEMI patients who underwent successful primary percutaneous coronary intervention (PPCI). Patients were categorized according to the median symptom-to-reperfusion-time: shorter (160 min, n = 54). CMR was performed 2–7 days after PPCI and at 1 month. CMR cine imaging was performed for functional assessment and late gadolinium enhancement to evaluate transmural infarct extent. Myocardial feature-tracking was used for strain analysis. Groups were comparable in relation to incidence of LAD disease and pre- and post-PPCI thrombolysis in myocardial infarction (TIMI) flow grades. The mean transmural extent score at follow-up was lower in patients with shorter reperfusion time (P < 0.01). Both baseline and follow-up maximum transmural extent scores were smaller in patients with shorter reperfusion time (P = 0.03 for both). Patients with shorter reperfusion time had more favourable global left ventricular (LV) circumferential strain (baseline, P = 0.049; follow-up, P = 0.01) and radial strain (baseline, P = 0.047; follow-up, P < 0.01), whilst LV longitudinal strain appeared comparable for both baseline and follow-up (P > 0.05 for both). In multi-variable regression analysis including all three strain directions, baseline LV circumferential strain was independently associated with the mean transmural extent score at follow-up (β=1.89, P < 0.001). In STEMI patients, time-to-reperfusion was significantly associated with smaller transmural extent of infarction and better LV circumferential and radial strain. Moreover, infarct transmurality and residual LV circumferential strain are closely linked. The representation of global left ventricular (LV) strain findings according to reperfusion delay is illustrated in the following manner: the baseline (BL) and follow-up (FU) global LV strain results of patients with shorter reperfusion time are presented on the left side, whilst the results of patients with longer reperfusion time are shown on the right side. Longitudinal strain findings are displayed using corresponding strain colour maps on a four-chamber view, along with strain time curves at BL and FU. Circumferential and radial strain findings are visualized through corresponding strain colour maps on short-axis views, with strain time curves at BL and FU. BL longitudinal strain values seem comparable between patients with shorter and longer reperfusion time. However, both circumferential and radial strain values appear markedly more favourable in patients who have a shorter reperfusion time. Furthermore, strain results in all directions (e.g. longitudinal) demonstrate improvement over time (BL to FU) in both patient groups (shorter and longer reperfusion time).
Funding Information
  • AstraZeneca

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