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Objectives
This study sought to hypothesize that global longitudinal strain (GLS) as a measure of infarct size, and mechanical dispersion (MD) as a measure of myocardial deformation heterogeneity, would be of incremental importance for the prediction of sudden cardiac death (SCD) or malignant ventricular arrhythmias (VA) after acute myocardial infarction (MI).
Background
SCD after acute MI is a rare but potentially preventable late complication predominantly caused by malignant VA. Novel echocardiographic parameters such as GLS and MD have previously been shown to identify patients with chronic ischemic heart failure at increased risk for arrhythmic events. Risk prediction during admission for acute MI is important because a majority of SCD events occur in the early period after hospital discharge.
Methods
We prospectively included patients with acute MI and performed echocardiography, with measurements of GLS and MD defined as the standard deviation of time to peak negative strain in all myocardial segments. The primary composite endpoint (SCD, admission with VA, or appropriate therapy from a primary prophylactic implantable cardioverter-defibrillator [ICD]) was analyzed with Cox models.
Results
A total of 988 patients (mean age: 62.6 ¡À 12.1 years; 72 % male) were included, of whom 34 (3.4 % ) experienced the primary composite outcome (median follow-up: 29.7 months). GLS (hazard ratio [HR]: 1.38; 95 % confidence interval [CI]: 1.25 to 1.53; p < 0.0001) and MD (HR/10 ms: 1.38; 95 % CI: 1.24 to 1.55; p < 0.0001) were significantly related to the primary endpoint. GLS (HR: 1.24; 95 % CI: 1.10 to 1.40; p?=?0.0004) and MD (HR/10 ms: 1.15; 95 % CI: 1.01 to 1.31; p?= 0.0320) remained independently prognostic after multivariate adjustment. Integrated diagnostic improvement (IDI) and net reclassification index (NRI) were significant for the addition of GLS (IDI: 4.4 % [p < 0.05]; NRI: 29.6 % [p < 0.05]), whereas MD did not improve risk reclassification when GLS was known.
Conclusions
Both GLS and MD were significantly and independently related to SCD/VA in these patients with acute MI and, in particular, GLS improved risk stratification above and beyond existing risk factors.
