Post-systolic shortening: a functional window into ischemic memory?

CXCR4+ and FLK-1+ identify circulating cells associated with improved cardiac function in patients following myocardial infarction

The biomarkers CXCR4/FLK-1 select cardiac progenitors from a stem cell pool in experimental models. However, the translational value of these cells in human ischemic heart disease is unknown. Here, flow-cytometry identified CD45(-)/CXCR4(+)/FLK-1(+) cells in 30 individuals without ischemic heart disease and 33 first-time acute myocardial infarction (AMI) patients. AMI patients had higher CD45(-)/CXCR4(+)/FLK-1(+) cell-load at 48-h and 3- and 6-months post-AMI (p = 0.003,0.04,0.04, respectively) than controls. Cardiovascular risk factors and left ventricular (LV) ejection fraction were not associated with cell-load. 2D-speckle-tracking strain echocardiography assessment of LV systolic function showed improvement in longitudinal strain and dyssynchrony during follow-up associated with longitudinal increases in and higher 48-h post-AMI CD45(-)/CXCR4(+)/FLK-1(+) cell-load (r = -0.525, p = 0.025; r = -0.457, p = 0.029, respectively). In conclusion, CD45(-)/CXCR4(+)/FLK-1(+) cells are present in adult human circulation, increased in AMI and associated with improved LV systolic function. Thus, CD45(-)/CXCR4(+)/FLK-1(+) cells may provide a diagnostic tool to follow cardiac regenerative capacity and potentially serve as a prognostic marker in AMI.

A patient with recent chest discomfort-ischemia or no ischemia? Postsystolic shortening comes to the rescue

The diagnosis of myocardial ischemia in the emergency department can be challenging particularly in a patient in whom the chest discomfort has abated. Symptoms can be atypical, physical exam is often noncontributory, the electrocardiogram is usually nondiagnostic and cardiac enzymes remain normal. Thus, the decision for hospital admission or discharge can be quite difficult. Here, we describe such a patient in whom echocardiography with strain imaging identified the presence of postsystolic shortening (PSS) at the left ventricular apex. This suggested the likelihood of ischemic memory in the territory of the left anterior descending (LAD) artery. At coronary angiography a high grade stenosis was present in the proximal LAD artery. Our report highlights the role of echocardiography in the detection of myocardial ischemia and apical PSS as a marker of ischemic memory.