Dependence of the Atrioventricular Conduction Time on the Conduction through the Atrioventricular Node and His-Purkinje System.

The electrical depolarization of the heart passes through various structures of the cardiac conduction system, which modify its conduction to different extents. In this study, we investigated the relationship between the atrioventricular conduction time (AV interval) and its contributors, the atrioventricular node (AVN) and the His-Purkinje system (HPS), as represented by the AH and HV intervals, respectively. We also compared sex differences in these intervals and their relations. Resting intracardiac tracings lasting 5 min were obtained from 64 patients (33 women) during an invasive electrophysiological study. The aforementioned intervals were measured for all consecutive beats. The mean AH interval was 85.9 ms, HV 43.7 ms, and AV 129.6 ms. Men had longer AH (80.0 vs. 65.9 ms), HV (38.4 vs. 35.3 ms), and AV intervals (124.7 vs. 108.5 ms) than women. The AV intervals were linearly correlated with AH intervals in all patients (r2 = 0.65). No significant correlation was found between AV and HV intervals in all patients (r2 = 0.05). There were no sex differences in these associations. Our results suggest that the atrioventricular conduction time depends mainly on the conduction through the AVN and less on the HPS. These relations are similar in both sexes, although men had longer conduction times through the AVN, HPS, and total atrioventricular conduction time.

Straight and crosier­shaped catheter techniques for phrenic nerve stimulation during cryoballoon pulmonary vein isolation for the treatment of atrial fibrillation.

BACKGROUND: Cryoablation is an effective and safe method of pulmonary vein isolation (PVI) for the treatment of atrial fibrillation (AF). However, monitoring of phrenic nerve function during cryoballoon PVI remains an important issue. AIMS: We aimed to compare 2 techniques of phrenic nerve stimulation (PNS) with the use of either a straight or a crosier­shaped decapolar deflectable catheter. METHODS: The study included 218 patients (mean [SD] age, 61.8 [10.9] years; 87 women) referred for cryoballoon PVI for AF. Patients were randomly assigned to PNS with either a straight or a crosier­shaped catheter. RESULTS: The groups did not differ in demographic characteristics or PVI effectiveness. The current threshold during PNS was lower in the group in which the crosier­shaped catheter was applied (mean [SD], 6.7 [4.9] mA vs 4.8 [3.7] mA; P <0.01). In this group, the procedure time was shorter (mean [SD], 72.6 [22.8] min vs 64.4 [14.8] min; P <0.01), fewer repositioning maneuvers were required (31.8% vs 19.4%; P <0.05), and atrial capture during PNS was observed more frequently (11.5% vs 29.6%; P <0.01). CONCLUSIONS: Straight and crosier­shaped catheter techniques are equally effective in monitoring for phrenic nerve palsy. The crosier­shaped catheter maintains its position better, thus leading to fewer dislocations and requiring fewer correction maneuvers, which might correlate with shorter procedure time. Moreover, this technique provides lower pacing thresholds. Both techniques may be safely used in patients with AF, and if stable phrenic nerve capture cannot be achieved, switching to another technique seems reasonable.

Interventional treatment of atrial fibrillation - contemporary methods and perspectives.

Atrial fibrillation (AF) is estimated to affect nearly 3 million people around the world. It is the most common arrhythmia and its incidence increases with age. Catheter ablation is an interventional procedure performed to reduce the patient's AF burden when pharmacotherapy did not succeed in relieving the patient's symptoms. The ablation is most effective in paroxysmal AF; however, many techniques are being developed to make this procedure more eligible for patients with persistent arrhythmia. The most common AF ablation technique involves separating electric activity of the pulmonary veins from the left atrium. Over recent years, many novel and promising techniques were developed (e.g., balloon cryoablation, circular catheter ablation, laser ablation, robotic navigation, etc.), which may further improve AF ablation efficacy.

Asymmetry of the variability of heart rate and conduction time between atria and ventricles.

BACKGROUND: Heart rate asymmetry is caused by an unequal contribution of heart rate decelerations and accelerations to heart rate variability. This study evaluates the asymmetric properties of the variability of the AA, HH, VV, AH and HV intervals. METHODS AND RESULTS: We recorded 50 1-min intracardiac ECG tracings from 10 patients (18-66 years old; 8 females) during a routine electrophysiological study. Standard descriptors of variance asymmetry were calculated for all intervals. Nonparametric tests were used for statistical comparisons. The prolongations of VV (P=0.0297), AH (P=0.0133) and HV (P=0.0004) intervals contributed significantly more than their shortenings to their short-term variance. The proportion of recordings with a larger contribution of prolongations than shortenings was significantly different from random for VV (0.66, P=0.0328), AH (0.68, P=0.0154) HV (0.74, P=0.0009). CONCLUSIONS: In addition to heart rate asymmetry (VV interval), the conduction from the atria, through the atrioventricular node, His-Purkinje system to ventricles shows asymmetric properties in 1-min tracings.

Low-density lipoprotein, its susceptibility to oxidation and the role of lipoprotein-associated phospholipase A2 and carboxyl ester lipase lipases in atherosclerotic plaque formation.

An increased level of low-density lipoprotein (LDL) is a very well established risk factor of coronary artery disease (CAD). Unoxidized LDL is an inert transport vehicle of cholesterol and other lipids in the body and is thought to be atherogenic. Recently it has been appreciated that oxidized products of LDL are responsible for plaque formation properties previously attributed to the intact particle. The goal of this article is to review the recent understanding of the LDL oxidation pathway. The role of oxidized products and key enzymes (lipoprotein-associated phospholipase A2 and carboxyl ester lipase) are also extensively discussed in the context of clinical conditions.