A case of an 82-year-old man who suffered an acute ST-elevation myocardial infarction while receiving treatment with intravenous immunoglobulin (IVIg) for thrombocytopenia is discussed. A total of 29 other cases of thromboembolism related to IVIg therapy have been reported, and the incidence seems to be especially high in elderly patients with cerebrovascular risk factors and also in patients with paraproteinemias. Possible mechanisms to account for this complication may include some of the following: platelet activation, increased blood viscosity, contamination of IVIg with activated coagulation factors, induced arterial vasospasm, production of vasoconstrictive cytokines, and vasculitis. Ten patients out of the 29 reported patients died from this serious complication. In our patient, spontaneous reperfusion occurred without any treatment and he had an uneventful outcome.
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BPP from foci outside the regions of dominant activation alters dispersion of atrial repolarization. Modulation of apamin-sensitive channels may contribute to the shortening of repolarization in CS and PV regions. Alterations of atrial repolarization gradient create an arrhythmogenic substrate and may be an early step in atrial electrophysiologic remodeling.
Initial clinical studies indicate a potential beneficial effect of erythropoietin (EPO) in patients with anemia and heart failure. Here, we investigate the direct contractile effects of erythropoietin on myocardial tissue. Treatment with EPO (50 U/ml) using excitable murine and human left ventricular muscle preparations resulted in a 37% and 62% increase in twitch tension, respectively (P<0.05). Isolated murine cardiomyocytes exposed to EPO demonstrated a 41% increase in peak sarcomere shortening (P=0.012). Using compounds that specifically stimulate a non-erythropoietic EPO receptor yielded similar increases in contractile dynamics. Cardiomyocyte Ca2+ dynamics showed an 18% increase in peak calcium in EPO treated cardiomyocytes over controls (P=0.03). Studies in muscle strips skinned after EPO treatment demonstrated a phosphorylation dependant increase in the viscous modulus as well as an increase in oscillatory work. The EPO mediated increase in peak sarcomere shortening was abrogated by PI3-K blockade via wortmannin and by non-isozyme specific PKC blockade by chelerythrine. Finally, EPO treatment resulted in an increase in PKCε in the particulate cellular fraction, indicating activation of this isoform. EPO exhibits direct positive inotropic and lusitropic effects in cardiomyocytes and ventricular muscle preparation. These effects are mediated through PI3-K and PKCε isoform signaling to directly affect both calcium release dynamics and myofilament function.
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