The ratio of cytochrome c oxidase subunit 4 isoform 4I1 and 4I2 mRNA is changed in permanent atrial fibrillation

AIMS

The conditions of hypoxia are suggested to induce permanent atrial fibrillation (AF). The regulation of COX4I2 and COX4I1 depends on oxygen availability in tissues. A role of COX4I2 in the myocardium of AF patients is supposed for pathogenesis of AF and subsequent alterations in the electron transfer chain (ETC) under hypoxia.

METHODS AND RESULTS

In vitro, influence of hypoxia on HeLa 53 cells was studied and elevated parts of COX 4I2 were confirmed. Myocardial biopsies were taken ex vivo from the patients' Right Atria with SR (n = 31) and AF (n = 11), respectively. RT- PCR for mRNA expresson, mitochondrial respiration by polarography and the protein content of cytochrome c oxidase (CytOx) subunit 4I1 and CytOx subunit 4I2 by ELISA were studied. Clinical data were correlated to the findings of gene expressions in parallel. Patients with permanent AF had a change in isoform 4I2/4I1 expression along with a decrease of isoform COX 4I1 expression. The 4I2/4I1 ratio of mRNA expression was increased from 0.630 to 1.058 in comparison. However, the protein content of CytOx subunit 4 was much lower in the AF group, whereas the respiration/units enzyme activity in both groups remained the same.

CONCLUSIONS

This study describes a possible molecular correlate for the development of AF. Due to the known functional significance of COX 4I2, mitochondrial dysfunction can be assumed as a part of the pathogenesis of AF.

The prognostic value of systemic vascular resistance in heart failure patients with permanent atrial fibrillation: a retrospective study

Heart failure (HF) and permanent atrial fibrillation (AF) interact mutually, exacerbating hemodynamic effects and causing adverse outcomes and increased healthcare costs. Monitoring hemodynamic indicators in patients with these comorbidities is crucial for effective clinical management. Transthoracic impedance cardiography (ICG) has been widely employed in assessing hemodynamic status in clinical settings. Given the limited research on the prognostic significance of ICG parameters in HF with permanent AF, we undertook this study. A total of 66 HF patients with permanent AF were included in this retrospective study, and the primary outcome was rehospitalization due to worsening HF within 180-day post-discharge. Cox regression analysis was performed to explore the connection between ICG-evaluated parameters and the outcome risk. Receiver operating characteristic (ROC) curve analysis determined the optimal cutoff values of risk factors, subsequently applied in plotting Kaplan Meier (KM) survival curves. Multivariate Cox regression analysis revealed that systemic vascular resistance (SVR) both on admission and at discharge independently predicted rehospitalization for worsening HF. ROC analysis established optimal SVR cutoff values: 320.89 (kPa s/L) on admission and 169.94 (kPa s/L) at discharge (sensitivity 70%, specificity 94.4%, area under the curve (AUC) 0.831, respectively, sensitivity 90%, specificity 55.6%, AUC 0.742). KM survival curves analysis showed that patients with SVR > 320.89 (kPa s/L) on admission had an 8.14-fold (P < 0.001) increased risk of the end-point event compared with those with SVR ≤ 320.89 (kPa s/L). Similarly, patients with SVR > 169.94 (kPa s/L) at discharge faced a risk elevated by 6.57 times (P = 0.002) relative to those with SVR ≤ 169.94 (kPa s/L). In HF patients with permanent AF, SVR measured by ICG emerges as an independent risk factor and clinical predictor for HF deterioration-related readmission within 180 days after discharge. Higher SVR levels, both upon admission and at discharge, correlate with an incremental rehospitalization risk.

Ivabradine for controlling heart rate in permanent atrial fibrillation: A translational clinical trial

BACKGROUND

Pharmacological options for rate control in atrial fibrillation are scarce. Ivabradine was postulated to reduce the ventricular rate in this setting.

OBJECTIVES

The objectives of this study were to evaluate the mechanism of inhibition of atrioventricular conduction produced by ivabradine and to determine its efficacy and safety in atrial fibrillation.

METHODS

The effects of ivabradine on atrioventricular node and ventricular cells were studied by in vitro whole-cell patch-clamp experiments and mathematical simulation of human action potentials. In parallel, a multicenter, randomized, open-label, phase III clinical trial compared ivabradine with digoxin for uncontrolled permanent atrial fibrillation despite β-blocker or calcium channel blocker treatment.

RESULTS

Ivabradine 1 μM inhibited "funny" current and rapidly activating delayed rectifier potassium channel current by 28.9% and 22.8%, respectively (P < .05). The sodium channel current and L-type calcium channel current were reduced only at 10 μM. Ivabradine slowed the firing frequency of a modeled human atrioventricular node action potential by 10.6% and induced a minimal prolongation of ventricular action potential. Thirty-five (51.5%) patients were randomized to ivabradine and 33 (49.5%) to digoxin. The mean daytime heart rate decreased by 11.6 beats/min (-11.5%) in the ivabradine arm (P = .02) vs 19.6 (-20.6%) in the digoxin arm (P < .001), although the noninferiority margin of efficacy was not met (Z = -1.95; P = .97). The primary safety end point occurred in 3 patients (8.6%) on ivabradine and in 8 (24.2%) on digoxin (P = .10).

CONCLUSION

Ivabradine produced a moderate rate reduction in patients with permanent atrial fibrillation. The inhibition of funny current in the atrioventricular node seems to be the main mechanism responsible for this reduction. Compared with digoxin, ivabradine was less effective, was better tolerated, and had a similar rate of serious adverse events.

The clinical utility of direct His-bundle pacing in patients with heart failure and permanent atrial fibrillation

In patients with significantly impaired left ventricle function permanent atrial fibrillation (AF) often coexists with symptoms of heart failure. Based on various studies, it is assumed that in patients with heart failure in functional class III and IV AF occurs in 40-50% of patients. AF adversely affects cardiac hemodynamics, and its harmfulness increases particularly in the failing heart. The lack of mechanical function of the left atrium, the usually fast ventricular rate and the irregular sequence of ventricular contraction constitute the spectrum of harmful effects of this arrhythmia. Therefore, the only way to address the underlying problem of AF, which is irregular ventricular rhythm, is to pace the ventricles and to slow or block the AV conduction. Classic, right ventricular pacing is contraindicated in this population as it promotes the abovementioned disorders by initiating additional dyssynchrony of left ventricular contraction with reduction of its contractility and aggravation of AF-related mitral regurgitation. The possibility of direct His bundle pacing (DHBP) significantly extended the clinical armamentarium of cardiac pacing. The restoration of the physiological electrical activation could significantly contribute to echocardiographic and clinical improvement. With time and the development of dedicated tools for direct His bundle pacing the success rate of implantations became more than 90% and the acceptable pacing thresholds under 2.0 V (1 ms) could be achieved in most patients. This contributed to the broader clinical application of DHBP in different patient' groups with various pacing indications. The authors of the paper discuss different electrocardiographic and clinical indications for DHBP.

The clinical utility of direct His-bundle pacing in patients with heart failure and permanent atrial fibrillation

In patients with significantly impaired left ventricle function permanent atrial fibrillation (AF) often coexists with symptoms of heart failure. Based on various studies, it is assumed that in patients with heart failure in functional class III and IV AF occurs in 40-50% of patients. AF adversely affects cardiac hemodynamics, and its harmfulness increases particularly in the failing heart. The lack of mechanical function of the left atrium, the usually fast ventricular rate and the irregular sequence of ventricular contraction constitute the spectrum of harmful effects of this arrhythmia. Therefore, the only way to address the underlying problem of AF, which is irregular ventricular rhythm, is to pace the ventricles and to slow or block the AV conduction. Classic, right ventricular pacing is contraindicated in this population as it promotes the abovementioned disorders by initiating additional dyssynchrony of left ventricular contraction with reduction of its contractility and aggravation of AF-related mitral regurgitation. The possibility of direct His bundle pacing (DHBP) significantly extended the clinical armamentarium of cardiac pacing. The restoration of the physiological electrical activation could significantly contribute to echocardiographic and clinical improvement. With time and the development of dedicated tools for direct His bundle pacing the success rate of implantations became more than 90% and the acceptable pacing thresholds under 2.0 V (1 ms) could be achieved in most patients. This contributed to the broader clinical application of DHBP in different patient' groups with various pacing indications. The authors of the paper discuss different electrocardiographic and clinical indications for DHBP.

Sex-related differences in risk factors, outcome, and quality of life in patients with permanent atrial fibrillation: results from the RACE II study

AIMS

Atrial fibrillation (AF) risk factors translate into disease progression. Whether this affects women and men differently is unclear. We aimed to investigate sex differences in risk factors, outcome, and quality of life (QoL) in permanent AF patients.

METHODS AND RESULTS

The Rate Control Efficacy in Permanent Atrial Fibrillation (RACE II) randomized 614 patients, 211 women and 403 men, to lenient or strict rate control. In this post hoc analysis risk factors, cardiovascular events during 3-year follow-up (cardiovascular death, heart failure hospitalization, stroke, systemic embolism, bleeding, and life-threatening arrhythmic events), outcome parameters, and QoL were compared between the sexes. Women were older (71 ± 7 vs. 66 ± 8 years, P < 0.001), had more hypertension (70 vs. 57%, P = 0.002), and heart failure with preserved ejection fraction (36 vs. 17%, P < 0.001), but less coronary artery disease (13 vs. 21%, P = 0.02). Women had more risk factors (3.7 ± 1.2 vs. 2.9 ± 1.4, P < 0.001) Cardiovascular events occurred in 46 (22%) women and 59 (15%) men (P = 0.03). Women had a 1.52 times [95% confidence interval (CI) 1.03-2.24] higher yearly cardiovascular event-rate [8.2% (6.0-10.9) vs. 5.4% (4.1-6.9), P = 0.03], but this was no longer significant after adjusting for the number of underlying risk factors. Women had reduced QoL, irrespective of age and heart rate but negatively influenced by their risk factors.

CONCLUSION

In this permanent AF population, women had more accumulation of AF risk factors than men. The observed higher cardiovascular event rate in women was no longer significant after adjusting for the number of risk factors. Further, QoL was negatively influenced by the higher number of risk factors in women. This suggests that sex differences may be driven by the greater risk factor burden in women.

The Benefit of Atrioventricular Junction Ablation for Permanent Atrial Fibrillation and Heart Failure Patients Receiving Cardiac Resynchronization Therapy: An Updated Systematic Review and Meta-analysis

BACKGROUND

Atrial fibrillation (AF) is correlated with a poor biventricular pacing and inadequate response to cardiac resynchronization therapy (CRT). Biventricular pacing improvement can be achieved by conducting the atrioventricular junction ablation (AVJA). We aimed to investigate the benefit of AVJA for permanent AF and heart failure with reduced ejection fraction (HFrEF) patients receiving CRT.

METHODS

In August 2020, a systematic review and meta-analysis study comparing CRT plus AVJA versus CRT for permanent AF and HFrEF patients was conducted. Relevant articles were identified through the electronic scientific database such as ClinicalTrials.gov, ProQuest, ScienceDirect, PubMed, and Cochrane. The pooled risk ratio (RR) and pooled mean difference (MD) were estimated.

RESULTS

A total of 3199 patients from 14 cohort studies were involved in this study. Additional AVJA reduced cardiovascular mortality (RR = 0.75, 95% confidence interval [CI] = 0.61 to 0.93, P < 0.01) in permanent AF and HFrEF patients receiving CRT. Biventricular pacing rate was higher in CRT plus AVJA group (MD = 8.65%, 95% CI = 5.62 to 11.67, P < 0.01) than in CRT alone group. The reverse remodeling characterized by the reduction of left ventricular end-diastolic diameter (LVEDD) was greater in the CRT plus AVJA group (MD = -2.11 mm, 95% CI = -3.79 to -0.42, P = 0.01).

CONCLUSION

In permanent AF and HFrEF patients receiving CRT, AVJA effectively increased the biventricular pacing rate. Adequate biventricular pacing rate provided a better response to the CRT marked by the greater ventricular reverse remodeling and survival from cardiovascular mortality.

Atrial fibrillation in dilated cardiomyopathy: Outcome prediction from an observational registry

BACKGROUND

Little is known about the role of different types of atrial fibrillation (AF) in dilated cardiomyopathy (DCM). We investigated the epidemiological and prognostic impact of different types of AF in DCM during long-term follow-up.

METHOD

We evaluated consecutive DCM patients enrolled in the Trieste Muscle Heart Disease Registry. Uni- and multivariable, extended Kaplan-Meier and propensity score-matching analyses were performed for a composite outcome including death/heart transplantation/ventricular-assist device implantation.

RESULTS

Out of 1181 DCM patients (71% males, age 49 ± 15 years, left ventricular ejection fraction 33 ± 11%), 46 (3.9%) had baseline permanent AF (permAF), while 66 (5.6%) had a history of paroxysmal/persistent AF. Compared with sinus rhythm (SR) patients, permAF patients were older (48 ± 15 vs. 61 ± 11 respectively, p = 0.001), were more frequently in NYHA class III-IV (18% vs. 30%, p = 0.002) and had larger left atrium diameter (40 ± 8 vs. 50 ± 10 mm, respectively). Paroxysmal/persistent AF patients had intermediate characteristics between permAF and SR. During a median follow-up of 135 (75-210) months, 63 patients developed permAF (0.45 new cases/100patients/year). At multivariable analysis, permAF as a time-dependent variable was an independent outcome predictor (HR 2.45; 95% C.I. 2.61-3.63, p < 0.001), together with creatinine, NYHA class, restrictive filling pattern and moderate-severe mitral regurgitation, while paroxysmal/persistent AF was neutral. Propensity score-matching analysis confirmed the higher rate of primary outcome events in patients with baseline or incident permAF versus patients without permAF during a very long-term follow-up (70% vs. 20%, p < 0.001).

CONCLUSIONS

PermAF in a large DCM cohort had low prevalence and incidence but had a relevant. prognostic role on hard outcomes.

Influence of heart rate control on exercise capacity and quality of life in patients with permanent atrial fibrillation

BACKGROUND

The optimal level of heart rate (HR) control in patients with atrial fibrillation (AF) is unknown. To assess the effect of rate control on cardiopulmonary exercise capacity and quality of life (QoL) in permanent AF.

METHODS

One hundred forty-three patients with permanent AF were enrolled in this study. All patients received rate control medications and were followed up for 1 year. After 1-year therapy, the exercise capacity and QoL were evaluated by cardiopulmonary exercise testing (CPET) and 36-item Short-Form Health Survey, respectively. Data were compared by dividing the patients according to the following criteria: (1) whether the resting HR was ≤80 or > 80 bpm; (2) whether the exercise HR during moderate exercises on CPET was ≤110 or > 110 bpm; and (3) whether the resting HR was ≤80 bpm and exercise HR was ≤110 bpm.

RESULTS

No significant differences in peak oxygen uptake, peak metabolic equivalent, and anaerobic threshold were found between the strict control and lenient control groups. Both physical component summary (PCS) and mental component summary (MCS) were significantly higher for the strict rate control group than for the lenient control group. The single-factor correlation analysis revealed a negative correlation between resting HR and both PCS and MCS. The multivariable linear regression analysis indicated that both exercise HR and duration of AF linearly correlated with PCS and MCS.

CONCLUSIONS

Therefore, in patients with permanent AF, exercise capacity may not be affected by the stringency of rate control, and strict rate control may be associated with better QoL.

[Medication-related negative outcomes in patients with permanent atrial fibrillation attended in a hospital emergency department]

OBJECTIVES

To detect the frequency of negative outcomes associated with medication in patients with permanent atrial fibrillation (AF) who are attended in a hospital emergency department, and to assess type and severity of such outcomes related to AF medications as well as the rate of preventable negative outcomes.

MATERIAL AND METHODS

Descriptive, observational cross-sectional study in patients with permanent AF who were attended in the emergency department of a tertiary care hospital during a 3-month period. A pharmacist interviewed the patients to record demographic characteristics, health problems, degree of functional impairment, and current drug treatments. An emergency physician and a pharmacist reviewed the patients' questionnaires and medical histories and evaluated them using the Dader method of pharmacotherapeutic follow-up.

RESULTS

Of the 210 patients assessed, 198 entered the final analysis. They had a mean (SD) age of 80.5 (7.3) years, and 114 (57.5%) were women. One handred and thirty-four (67.7%) patients had medication-related negative outcomes; 61 (45.5%) of the outcomes were related to treatment for permanent AF. Twenty-four of these 61 patients (39.3%) had problems affecting safety; 36 (59%) of the problems were caused by drugs to control heart rate. Of the 73 patients with negative outcomes unrelated to AF medication, 34 (46.6%) were related to necessary medications and 38 (52.1%) were taking antibiotics. The frequencies of avoidable negative outcomes were significantly different between the group of patients with problems related to drug therapy for AF (where 55.7% were due to medications considered unnecessary) and those with problems unrelated to AF medications (where 78.1% were from avoidable medications) (P=.010). However, the level of seriousness was similar.

CONCLUSION

Nearly two-thirds of patients with permanent AF who come to the emergency department have a medication- related negative outcome that may or may not be related to AF treatment. Problems from drugs taken for reasons other than AF could more easily be avoided.

Outcomes of apixaban vs. warfarin by type and duration of atrial fibrillation: results from the ARISTOTLE trial

AIMS

It is uncertain whether the benefit from apixaban varies by type and duration of atrial fibrillation (AF).

METHODS AND RESULTS

A total of 18 201 patients with AF [2786 (15.3%) with paroxysmal and 15 412 (84.7%) with persistent or permanent] were randomized to apixaban or warfarin. In this pre-specified secondary analysis, we compared outcomes and treatment effect of apixaban vs. warfarin by AF type and duration. The primary efficacy endpoint was a composite of ischaemic or haemorrhagic stroke or systemic embolism. The secondary efficacy endpoint was all-cause mortality. There was a consistent reduction in stroke or systemic embolism (P for interaction = 0.71), all-cause mortality (P for interaction = 0.75), and major bleeding (P for interaction = 0.50) with apixaban compared with warfarin for both AF types. Apixaban was superior to warfarin in all studied endpoints, regardless of AF duration at study entry (P for all interactions >0.13). The rate of stroke or systemic embolism was significantly higher in patients with persistent or permanent AF than patients with paroxysmal AF (1.52 vs. 0.98%; P = 0.003, adjusted P = 0.015). There was also a trend towards higher mortality in patients with persistent or permanent AF (3.90 vs. 2.81%; P = 0.0002, adjusted P = 0.066).

CONCLUSION

The risks of stroke, mortality, and major bleeding were lower with apixaban than warfarin regardless of AF type and duration. Although the risk of stroke or systemic embolism was lower in paroxysmal than persistent or permanent AF, apixaban is an attractive alternative to warfarin in patients with AF and at least one other risk factor for stroke, regardless of the type or duration of AF.