Assessment of distribution and evolution of Mechanical dyssynchrony in a porcine model of myocardial infarction by cardiovascular magnetic resonance

Background: we sought to investigate the relationship between infarct and dyssynchrony post- myocardial infarct (mi),in a porcine model. mechanical dyssynchrony post-mi is associated with left ventricular (lv) remodeling and increased mortality. methods. cine,gadolinium-contrast,and tagged cardiovascular magnetic resonance (cmr) were performed pre-mi,9 2 days (early post-mi),and 33 10 days (late post-mi) post-mi in 6 pigs to characterize cardiac morphology,location and extent of mi,and regional mechanics. lv mechanics were assessed by circumferential strain (ec). electro-anatomic mapping (eam) was performed within 24 hrs of cmr and prior to sacrifice. results: mean infarct size was 21 4% of lv volume with evidence of post-mi remodeling. global ec significantly decreased post mi (-27 1.6% vs. -18 2.5% (early) and -17 2.7% (late),p < 0.0001) with no significant change in peri-mi and mi segments between early and late time-points. time to peak strain (ttp) was significantly longer in mi,compared to normal and peri-mi segments,both early (440 40 ms vs. 329 40 ms and 332 36 ms,respectively; p = 0.0002) and late post-mi (442 63 ms vs. 321 40 ms and 355 61 ms,respectively; p = 0.012). the standard deviation of ttp in 16 segments (sd16) significantly increased post-mi: 28 7 ms to 50 10 ms (early,p = 0.012) to 54 19 ms (late,p = 0.004),with no change between early and late post-mi time-points (p = 0.56). ttp was not related to reduction of segmental contractility. eam revealed late electrical activation and greatly diminished conduction velocity in the infarct (5.7 2.4 cm/s),when compared to peri-infarct (18.7 10.3 cm/s) and remote myocardium (39 20.5 cm/s). conclusions: mechanical dyssynchrony occurs early after mi and is the result of delayed electrical and mechanical activation in the infarct. © 2012 abd-elmoniem et al; licensee biomed central ltd.