How sex affects the sinus rhythm heartbeat.

Background: There is increasing awareness of sex-specific differences in epidemiology and pathophysiology of atrial fibrillation (AF). It is, however, unknown whether males and females differ in atrial electrophysiological properties during sinus rhythm (SR). The aim of this study was therefore to investigate sex-based (regional) differences in electrophysiological properties during SR of the right (RA) and left (LA) atrium including Bachmanns Bundle (BB) and pulmonary vein region (PVA). Methods: Intra-operative, high resolution mapping during SR was performed in 53 matched females with males (without a history of AF), to measure lines of conduction block (CB), continuous conduction delay and block (cCDCB), conduction velocities (CV), total atrial activation times (TAT), unipolar potential voltages and percentage of low voltage areas (LVA). Results: Compared to males, females have significantly 1) lower unipolar potential voltages and slower CV at both RA and BB, 2) more LVAs, CB and cCDCB lines and longer CB and cCDCB lines at the RA only (all P < 0.05). Conclusions: Electrophysiological properties of the atria during SR differ between males and females. These sex-based differences are particularly present at the RA and to a lesser degree at BB. In females, both the RA and BB contained more areas of conduction disorders and low voltage potentials. Future studies are required to investigate whether these areas play a role in sex-based differences in vulnerability to arrhythmias such as atrial fibrillation.

Impact of Obesity on Atrial Electrophysiological Substrate.

(1) Background. Obesity is a well-established worldwide recognised risk factor for atrial fibrillation (AF). Prior review papers reported on the associations between obesity and AF development, but not on the relation between obesity and atrial electrophysiology. We therefore conducted a systematic review to describe the current knowledge of the characteristics of the atrial electrophysiological substrate in obese individuals and how they relate to the development of AF. (2) Methods. A search was conducted in Pubmed, Embase, and the Cochrane Library for publications evaluating the impact of obesity on atrial electrophysiology, electrical substrates, and their relation to the development of AF. (3) Results. A systematic literature search retrieved 477 potential publications based on the inclusion criteria; 76 full-text articles were selected for the present systematic review. The literature demonstrated that obesity predisposes to not only a higher AF incidence but also to more extensive atrial electrophysiological abnormalities increasing susceptibility to AF development. (4) Conclusion. Obesity may predispose to an overall increase in atrial electropathology, consisting of an increase in the slowing of the conduction, conduction block, low-voltage areas, and complex fractionated electrograms. To determine the impact of obesity-induced atrial electrical abnormalities on the long-term clinical outcome, further prospective studies are mandatory.

The influence of sex on early post-operative atrial fibrillation after cardiac surgery.

BACKGROUND: Early post-operative atrial fibrillation (EPOAF) occurs more frequently in male (M) patients. However, most patients included in EPOAF studies were also M. The aim of the present study was to compare, in a matched M and F population, the occurrence of EPOAF episodes and EPOAF characteristics using continuous rhythm monitoring (CRM) during the first five post-operative days. METHODS: Our study population consisted of 30 F patients matched with 30 M patients admitted for elective cardiac surgery. After cardiac surgery, patients were continuously monitored for a maximum of 5 days, and the burden of EPOAF episodes was quantified. RESULTS: No significant differences in the onset, number, burden, total duration, shortest, median and longest EPOAF episode were detected between M and F patients. However, EPOAF occurred more frequently on the third post-operative day (F: 16 vs. M: 7; p = .013). CONCLUSIONS: Except for the occurrence of the EPOAF on the third post-operative day. EPOAF characteristics did not differ between M and F patients.

Low-voltage potentials contribute to postoperative atrial fibrillation development in obese patients.

BACKGROUND: Obesity predisposes to the development of atrial fibrillation (AF); however, the pathophysiology underlying this relation is only partly understood. OBJECTIVE: As low-voltage areas are considered indicators of the arrhythmogenic substrates promoting AF, our study aimed to compare the extensiveness of atrial low-voltage areas between obese and nonobese patients by using high-resolution epicardial mapping in order to identify predilection sites of low-voltage areas. METHODS: A total of 430 patients (131 (30%) obese and 299 (70%) nonobese) were matched resulting in 212 patients (body mass index [BMI] ≥30 kg/m2: n = 106; BMI <30 kg/m2: n = 106) undergoing cardiac surgery (mean age 63 ± 11 years; 161 male). All patients underwent epicardial mapping of the right atrium, Bachmann bundle (BB), and left atrium during sinus rhythm. Low-voltage potentials were defined as potentials with peak-to-peak amplitudes below the fifth percentile of all potential amplitudes obtained from nonobese patients. RESULTS: Compared with nonobese patients, obese patients have potentials with lower voltages (median of medians) (4.5 mV [0.4-16.2 mV] vs 5.5 mV [0.8-18.0 mV]; P < .001), especially at BB (4.1 mV [0.4-12.3 mV] vs 6.2 mV [1.0-14.3 mV]; P < .001) and left atrium (5.1 mV [0.5-10.1 mV] vs 6.2 mV [0.8-15.9 mV]; P = .003). The percentage of low-voltage potentials was higher in obese (median 3.6% [0.0%-77.1%]) than in nonobese (median 2.3% [0.0%-57.9%]) patients (P < .001), again at BB (obese: 2.9% [0.0%-77.1%] vs nonobese: 0.9% [0.0%-42.0%]; P < .001). Percentages of low-voltage potentials correlated with incidences of conduction block (P < .001), while BMI (P = .044) and low-voltage potentials (P = .001) were independent predictors for the incidence of early postoperative AF. CONCLUSION: Obesity may predispose to an overall decrease in atrial voltage and a higher percentage in low-voltage potentials. BB was a predilection area for low voltage within the atria of obese patients.

Heterogeneity in Conduction Underlies Obesity-Related Atrial Fibrillation Vulnerability.

BACKGROUND: Obese patients are more vulnerable to development of atrial fibrillation but pathophysiology underlying this relation is only partly understood. The aim of this study is to compare the severity and extensiveness of conduction disorders between obese patients and nonobese patients measured at a high-resolution scale. METHODS: Patients (N=212) undergoing cardiac surgery (male:161, 63±11 years) underwent epicardial mapping of the right atrium, Bachmann bundle, and left atrium during sinus rhythm. Conduction delay (CD) was defined as interelectrode conduction time of 7 to 11 ms and conduction block (CB) as conduction time ≥12 ms. Prevalence of CD/CB, continuous CDCB (cCDCB), length of CD/CB/cCDCB lines, and severity of CB were analyzed. RESULTS: In obese patients, the overall incidence of CD (3.1% versus 2.6%; P=0.002), CB (1.8% versus 1.2%; P<0.001), and cCDCB (2.6% versus 1.9%; P<0.001) was higher and CD (P=0.012) and cCDCB (P<0.001) lines are longer. There were more conduction disorders at Bachmann bundle and this area has a higher incidence of CD (4.4% versus 3.3%, P=0.002), CB (3.1% versus 1.6%, P<0.001), cCDCB (4.6% versus 2.7%, P<0.001) and longer CD (P<0.001) or cCDCB (P=0.017) lines. The severity of CB is also higher, particularly in the Bachmann bundle (P=0.008) and pulmonary vein (P=0.020) areas. In addition, obese patients have a higher incidence of early de-novo postoperative atrial fibrillation (P=0.003). Body mass index (P=0.037) and the overall amount of CB (P=0.012) were independent predictors for incidence of early postoperative atrial fibrillation. CONCLUSIONS: Compared with nonobese patients, obese patients have higher incidences of conduction disorders, which are also more extensive and more severe. These differences in heterogeneity in conduction are already present during sinus rhythm and may explain the higher vulnerability to atrial fibrillation of obese patients.

Impact of atrial programmed electrical stimulation techniques on unipolar electrogram morphology.

INTRODUCTION: Intra-atrial conduction abnormalities are associated with the development of atrial fibrillation (AF) and cause morphological changes of the unipolar atrial electrogram (U-AEGM). This study examined the impact of different atrial programmed electrical stimulation (APES) protocols on U-AEGM morphology to identify the most optimal APES protocol provoking conduction abnormalities. METHODS: APES techniques (14 protocols) were applied in 30 patients referred for an electrophysiology study, consisting of fixed rate, extra, and decremental stimuli at different frequencies. U-AEGM morphologies including width, amplitude, and fractionation for patients without (control group) and with a history of AF (AF group) were examined during APES. In addition, sinus rhythm (SR) U-AEGMs preceding different APES protocols were compared to evaluate the morphology stability over time. RESULTS: U-AEGM morphologies during SR before the APES protocols were comparable (all P > .396). Atrial refractoriness was longer in the AF group compared to the control group (298 ± 48 vs 255 ± 33 ms; P ≤ .020), but did not differ between AF patients with and without amiodarone therapy (278 ± 48 vs 311 ± 40 ms; P ≥ .126). Compared to the initial SR morphology, U-AEGM width, amplitude, and fractionation changed significantly during the 14 different APES protocols, particularly in the AF group. In both groups, U-AEGM changes in morphology were most pronounced during fixed-rate stimulation with extra stimuli (8S1-S2 = 400-250 ms). CONCLUSION: APES results in significant changes in U-AEGM morphology, including width, amplitude, and fractionation. The impact of APES differed between APES sequence and between patients with and without AF. These findings suggest that APES could be useful to identify AF-related conduction abnormalities in the individual patient.