Remodeled left ventricular myocardium remote to infarction sites is the arrhythmogenic substrate for sudden cardiac death

Antiarrhythmic effects of metformin

Atrial fibrillation/flutter (AF) is a major public health problem and is associated with stroke, heart failure, dementia, and death. It is estimated that 20%-30% of Americans will develop AF at some point in their life. Current medications to prevent AF have limited efficacy and significant adverse effects. Newer and safer therapies to prevent AF are needed. Ventricular arrhythmias are less prevalent than AF but may have significant consequences including sudden cardiac death. Metformin is the most prescribed, first-line medication for treatment of diabetes mellitus (DM). It decreases hepatic glucose production but also reduces inflammation and oxidative stress. Experimental studies have shown that metformin improves metabolic, electrical, and histologic risk factors associated with AF and ventricular arrhythmias. Furthermore, in large clinical observational studies, metformin has been associated with a reduced risk of AF in people with DM. These data suggest that metformin may have antiarrhythmic properties and may be a candidate to be repurposed as a medication to prevent cardiac arrhythmias. In this article, we review the clinical observational and experimental evidence for the association between metformin and cardiac arrhythmias. We also discuss the potential antiarrhythmic mechanisms underlying this association. Repurposing a well-tolerated, safe, and inexpensive medication to prevent cardiac arrhythmias has significant positive public health implications.

Coronary Flow Reserve in Non-Infarcted Myocardium Predicts Long-Term Clinical Outcomes in Patients Undergoing Percutaneous Coronary Intervention

PURPOSE

Coronary flow reserve (CFR) is recognized as an indicator of myocardial perfusion. The aim of this study was to assess the relationship between CFR in the non-infarcted myocardium and the incidence of major adverse cardiac events (MACEs).

MATERIALS AND METHODS

100 consecutive patients with acute myocardial infarction (AMI) undergoing percutaneous coronary intervention (PCI) were enrolled in the present study, and divided into MACE and non-MACE groups according to the incidence of 12-month MACEs. Left ventricular function and CFR were analyzed using two-dimensional echocardiography and myocardial contrast echocardiography at one week after PCI. Cardiac troponin I levels were assayed to estimate peak concentrations thereof.

RESULTS

The MACE group was associated with lower CFR, compared to the non-MACE group (2.41 vs. 2.77, p<0.001). In the multivariable model, CFR in the non-infarcted myocardium was an independent predictor of 12-month MACE (hazard ratio: 0.093, 95% confidence interval: 0.020-0.426, p=0.002) after adjustment for baseline demographic and clinical characteristics.

CONCLUSION

CFR in the non-infarcted myocardium is a useful marker for predicting 12-month MACEs in patients with AMI undergoing primary PCI.

Different effects of lysophosphatidic acid on L-type calcium current in neonatal rat ventricular myocytes with and without H2O2 treatment

L-type calcium current (I(Ca-L)) alterations are implicated in various cardiac diseases, and the lysophosphatidic acid (LPA) level increases in several ischemic heart diseases. We investigated the effects of LPA on I(Ca-L) in normal and H2O2-treated neonatal rat ventricular myocytes. LPA treatment (24h) increased the action potential duration (APD) and I(Ca-L) in normal ventricular myocytes, but it decreased these parameters in H2O2-treated myocytes. LPA increased the single-channel open probability of L-type calcium channels in both normal and H2O2-treated myocytes. LPA activated calcineurin (CaN) and induced the cytoplasm-to-nucleus translocation of nuclear factor of activated T-cells (NFAT) in H2O2-treated cardiomyocytes. In H2O2-treated cardiomyocytes, LPA decreased Ca(v)1.2 mRNA and protein expression levels at 4 and 8h, respectively. A CaN inhibitor (FK-506) prevented LPA-induced APD, I(Ca-L), and Ca(v)1.2 mRNA and protein down-regulation. The LPA-induced I(Ca-L) increase in normal cardiomyocytes was CaN-NFAT signaling-independent, and LPA did not affect Ca(v)1.2 mRNA or protein expression. In conclusion, LPA increases the I(Ca-L) in normal ventricular myocytes by increasing the single-channel open probability of L-type calcium channels, and LPA decreases I(Ca-L) in H2O2-treated cardiomyocytes via the CaN-NFAT pathway.