Left atrial adaptation in ischemic heart disease: insights from a cardiovascular magnetic resonance study.

Left atrium (LA) plays a key role in the overall cardiac performance. However, it remains unclear how LA adapts, in terms of function and volumes, to left ventricular dysfunction in the acute and post-acute phases of myocardial infarction. LA volumes and function were evaluated in patients in the acute phase of ST-segment elevation myocardial infarction (acute-STEMI group) and in the post-acute phase after STEMI (post-acute STEMI group). Ten age and sex-matched healthy controls served as control group. In all subjects LA was assessed by a compressed-sensing cine pulse sequence and by a 3D non-model-based reconstruction. LV infarct size and microvascular obstruction were determined on late-gadolinium-enhancement data and LV myocardial oedema and myocardial haemorrhage were measured on T2-mapping data. Indexed LA maximum and minimum volumes did not differ between the acute (n = 50) and post-acute (n = 47) STEMI groups. LA active emptying fraction (LAAEF) was higher in the acute-STEMI as compared with the post-acute STEMI groups (0.63 ± 0.23 vs 0.37 ± 0.24, p < 0.0001). Conversely, LA passive emptying fraction (LAPEF) was lower in the acute-STEMI compared with post-acute-STEMI (0.34 ± 0.15 vs 0.65 ± 0.15, p < 0.0001) patients. In the acute-STEMI group, LAAEF was positively and LAPEF negatively correlated with LV myocardial tissue damage (r = 0.523 p = 0.0001; r = - 0.451 p = 0.0013). Negative and positive correlations were also found between LAAEF and LAPEF and time after STEMI (r = - 0.559 p = 0.0013 and r = 0.589 p = 0.0006, respectively). LA increases its active contractile function in the acute phase of STEMI to support LV filling. The extent (but not the type) of LV damage determines LA adaptions which normalizes over time.