Mechanoelectrical feedback in pulmonary vein arrhythmogenesis: Clinical challenges and therapeutic opportunities

Electrical and Structural Insights into Right Ventricular Outflow Tract Arrhythmogenesis

The right ventricular outflow tract (RVOT) is the major origin of ventricular arrhythmias, including premature ventricular contractions, idiopathic ventricular arrhythmias, Brugada syndrome, torsade de pointes, long QT syndrome, and arrhythmogenic right ventricular cardiomyopathy. The RVOT has distinct developmental origins and cellular characteristics and a complex myocardial architecture with high shear wall stress, which may lead to its high vulnerability to arrhythmogenesis. RVOT myocytes are vulnerable to intracellular sodium and calcium overload due to calcium handling protein modulation, enhanced CaMKII activity, ryanodine receptor phosphorylation, and a higher cAMP level activated by predisposing factors or pathological conditions. A reduction in Cx43 and Scn5a expression may lead to electrical uncoupling in RVOT. The purpose of this review is to update the current understanding of the cellular and molecular mechanisms of RVOT arrhythmogenesis.

Fluid Retention In The Pulmonary Circulation As A Cause Of Pulmonary Vein Dilatation And Atrial Fibrillation Development In Chronic Heart Failure Patients

Objective — The study objective was to perform a transthoracic echocardiographic study of the remodeling of the left atrium and the maximum and minimum diameters of pulmonary veins, as well as remodeling regression in the process of heart failure treatment, in patients with chronic heart failure (CHF) and different forms of atrial fibrillation (AF). Material and Methods — The prospective study included patients having CHF with paroxysmal AF (n=38) and permanent AF (n=36) and without arrhythmia (n=225); the patients had their maximum and minimum diameters of the pulmonary vein measured, additionally to the standard echocardiographic protocol, before and after six months of standard therapy including a loop diuretic. Results — Structural changes in the left atrium and pulmonary veins of patients with CHF having permanent atrial fibrillation were significantly more distinct than those in patients with paroxysmal AF, in patients without arrhythmia, and in the control group. A decrease in the maximum and minimum diameters of the pulmonary vein followed by termination of AF attacks within a year of observation was detected after CHF treatment with a loop diuretic in patients with paroxysmal AF and permanent AF. Conclusion — Prescribing loop diuretics to patients with pulmonary vein dilatation detected during transthoracic echocardiography in subjects with paroxysmal AF and permanent AF results in a decrease in PV diameters and termination of AF attacks in paroxysmal AF.

Vascular endothelial growth factor modulates pulmonary vein arrhythmogenesis via vascular endothelial growth factor receptor 1/NOS pathway

Atrial fibrillation (AF) is a common form of arrhythmia with serious public health impacts, but its underlying mechanisms are not yet fully understood. Vascular endothelial growth factor (VEGF) is highly expressed in the atrium of patients with AF, but whether VEGF affects AF pathogenesis remains unclear. Pulmonary veins (PVs) are important sources for the genesis of atrial tachycardia or AF. Therefore, this study assessed the effects of VEGF on PV electrophysiological properties and evaluated its underlying mechanisms. Conventional microelectrodes and whole-cell patch clamps were performed using isolated rabbit PV preparations or single isolated PV cardiomyocytes before and after VEGF or VEGF receptor (VEGFR), Akt, NOS inhibitor administration. We found that VEGF (0.1, 1, and 10 ng/mL) reduced the PV beating rate in a dose-dependent manner. Furthermore, VEGF (10 ng/mL) reduced late diastolic depolarization and diastolic tension. Isoproterenol increased PV beating and burst firing, which was attenuated by VEGF (1 ng/mL). In the presence of VEGFR-1 inhibition (ZM306416 at 10 μM) and L-NAME (100 μM), VEGF (1 ng/mL) did not alter PV spontaneous activity. In isolated PV cardiomyocytes, VEGF (1 ng/mL) decreased L-type calcium, sodium/calcium exchanger, and late sodium currents. In conclusion, we found that VEGF reduces PV arrhythmogenesis by modulating sodium/calcium homeostasis through VEGFR-1/NOS signaling pathway.