A crucial aspect in unraveling the complexities of the coexistence of atrial fibrillation (AF) and heart failure with preserved ejection fraction (HFpEF) lies in comprehending the structural and electrical remodeling processes occurring in both the atria and ventricles. This subsection aims to dissect the intricate changes at the cellular and tissue levels, identifying key components of remodeling and elucidating their impact on the perpetuation of AF and HFpEF.
In HFpEF often the ventricular hypertrophy as a comorbidity, results in an impairment of relaxation, and it is a cause of the myocardial stiffening.
Subsection 5: Patient Stratification and Subtypes
Due to the high variability and the various phenotypes of AF and HFpEF, it would be beneficial to study the underlying disease mechanisms at the molecular, structural, or clinical levels in order to identify subtypes of patients that require tailored treatments. Investigating such subtypes could in the end transform the whole way we approach treatment of these conditions finally creating more person specific and targeted therapies.
Molecular Subtypes:
The molecular profiling of patients with HFPEF and AF could be helpful since distinctive subtypes of patients with individual genetic or molecular characteristics can be identified. Identification of molecular profile in HFPEF and AF patients has the capability to separate the patients into distinct subgroups with specific genetic or molecular characteristics [
85] This includes research on Alzheimer's disease (AD) and colorectal cancer (CRC) [
86].
Similarly, in CRC, integrated analysis of transcriptome and genome identified four immunological molecular subtypes (IMSs) with distinct molecular characteristics and clinical outcomes [
87]. These IMSs were associated with immune gene expression, immune microenvironment, and immune checkpoints [
88]. These findings highlight the potential for personalized medicine and patient stratification in immunotherapies [
89]. Therefore, molecular profiling can indeed identify distinct subtypes of patients with unique genetic or molecular signatures in various diseases.
Structural and Clinical Subtypes:
(AF) based totally on structural remodeling patterns or clinical traits can screen subgroups with varying responses to remedy. This method lets in for the improvement of focused interventions that address the unique desires of each affected person subgroup. Studies have proven that HFpEF is a clinically heterogeneous syndrome with more than one etiologic and pathophysiologic elements [
90]. The categorization of HF sufferers based on ejection fraction (EF) has been questioned, as EF may additionally vary relying on exceptional hemodynamic conditions and has sizeable interobserver variability [
91]. HFpEF and HF with mid- range EF (HFmrEF) were described as intermediate populations between HF with reduced EF (HFrEF) and HFpEF, but they also display heterogeneity in presentation and pathophysiology [
92]. AF frequently co-happens with HF, and expertise the interaction among these two conditions is crucial for developing shared preventive and healing strategies [
93].
Cardiac amyloidosis:
Sub-clinical isolated cardiac amyloidosis (ICA) is associated with an increased risk of atrial fibrillation (AF) in elderly patients [
94]. ICA refers to the deposition of amyloid in the atrium without valvular heart disease. In patients with AF, those with ICA are more likely to have persistent forms of AF and lower sinus rhythm P-wave amplitude [
95]. Senile cardiac amyloidosis, predominantly visible in elderly males, is regularly as a In AD, mass-spectrometry proteinomics in cerebrospinal fluid (CSF) showed five molecular subtypes on the basis of their differing genetic profiles, brain atrophy, and clinical outcomes result of wild-kind transthyretin (TTR) and is associated with coronary heart failure with preserved ejection fraction (HFpEF) and AF [
96,
97]. Atrial amyloidosis relates to an improved AF and thromboembolic event risk. This cardiac amyloidosis manifestation underscores early diagnosis' importance for treatment. While scintigraphy proves a common noninvasive prognostic technique, endomyocardial biopsy constitutes the definitive diagnosis' gold standard. Further studies must outline AHF, perceive imaging modalities enabling antemortem diagnosis, and determine optimal control techniques [
98].
Imaging Techniques:
Advanced imaging plays a critical role in our evolving understanding of the complex interplay between atrial fibrillation (AF) and heart failure with preserved ejection fraction (HFpEF). Of these, cardiac magnetic resonance imaging (CMR) and molecular imaging are particularly useful for detailed assessments with several points being elucidated using these modalities.
Cardiac Magnetic Resonance Imaging (CMR):
Left atrial (LA) function has been shown to be important for prognosis in heart failure with preserved ejection fraction (HFpEF) in both sinus rhythm and persistent atrial fibrillation (AF) [
99,
100]. LA strain, quantified by CMR imaging, has been associated with the risk of HFpEF [
101]. Additionally, LA strain has been found to be independently associated with HFpEF and has potential value in diagnosing the condition [
102]. The combination of AF and HFpEF is associated with increased mortality, as AF worsens the hemodynamics of HF [
103]. Further research is needed to understand the prognostic impact of LA function in HFpEF patients with different types of AF.
Molecular Imaging:
Think of PET and MRI as the heart's own detectives, like the medical Sherlock Holmes and Watson! These imaging wizards step into action when there's a heart issue, unraveling the mystery of inflammation and checking in on the immune cell hustle during a myocardial infarction [
104,
105]. T It's like they've got this superpower to see beyond the surface and reveal the heart's secrets. What makes these imaging sidekicks truly special is their ability to play it cool without any invasive measures. They're like the heart's personal photographers, capturing snapshots of the damage, keeping an eye on tissue makeover, and documenting the heart's journey to recovery [
106]. Imagine them as the paparazzi of the medical world, but with a heartwarming mission.PET imaging deserves its own spotlight as the storyteller extraordinaire. Picture it as a skilled artist, illustrating a vibrant canvas of inflammation markers, fibrosis, and the blooming of new blood vessels in cases of hypertensive heart failure [
107]. Additionally, whole-body molecular imaging with PET has been employed to study the cardio-renal crosstalk after MI, providing insights into systemic inflammation and its impact on renal function [
108]. These techniques enable the identification and monitoring of important molecular components such as inflammatory markers, cellular receptors and metabolic pathways. By targeting these specific molecules, molecular imaging improves our ability to understand the molecular signatures associated with AF and HFpEF, thereby helping to develop targeted therapeutic strategies.
Molecular Biology Techniques
In addition to advanced imaging methodologies, molecular biology techniques offer deeper insight into the molecular complexity underlying both AF and HFpEF. Analysis of tissue samples using molecular biology methods provide valuable information regarding molecular mechanisms and changes at the cellular level. These include:
Molecular Biology Techniques for Tissue Analysis:
Molecular biology techniques for tissue analysis in AF-HFPEF include the use of next-generation sequencing panels (NGS) for targeted genetic analysis and comprehensive genomic profiling (CGP) for more comprehensive analysis of genetic alterations. Formalin-fixed paraffin-embedded (FFPE) samples are widely used in tissue analysis but low-quality genetic material extracted from FFPE samples can render sequence data unreliable. Low-acid fixatives, such as low-acid formalin fixation (ADF) and precooled ADF (coldADF), have shown better DNA preservation and sequence capture performance compared to neutral buffered formalin (NBF) [
109]. Another study offered additional promise of discovery again by combining high-level microRNA profiling with humaninduced pluripotent stem cell-derived cardiomyo-cytes (hiPSC-CMs). The aim was to discover novel molecular pathways in HFpEF; microRNA profiling to elucidate the molecular underpinnings of HFpEF, with hiPSC- CMs serving as a HFpEF disease model system [
110].
Rationale Behind Molecular Techniques:
Molecular biology techniques are powerful tools. They identify key players in AF and HFpEF. The methods decipher gene expression alterations, mutations, and epigenetic modifications contributing to disease pathogenesis[
111,
112,
113]. Elucidating the molecular underpinnings pinpoints potential therapeutic targets and biomarkers. This paves the way for precision medicine approaches. These approaches are tailored to the unique molecular profiles of AF and HFpEF individuals[
114]. These techniques, such as next-generation sequencing and DNA analysis, provide crucial insights into disease mechanisms and allow for accurate diagnostic methods and personalized drug treatment modalities [
115].
Management of patients with HFpEF and AF
HFpEF-AF and medical therapy:
Treatment with dapagliflozin, an SGLT2i, in the EMPEROR-Preserved trial was found to decrease the overall incidence of atrial fibrillation/flutter, regardless of the presence of diabetes [
116]. Mechanisms by which SGLT2i may reduce the burden of atrial fibrillation include hypertension, oxidative stress, inflammation, increased sympathy, and reduction of left atrial dilation and epicardial fat volume [
117]. Sodium glucose-linked transporter 2 inhibitors (SGLT2i) have demonstrated efficacy in reducing hospitalizations related to heart failure and enhancing the quality of life in patients with HFpEF [
118].
Dapagliflozin has been shown to decrease serum TNF-α levels [
119]. In addition, dapagliflozin seems to be making a positive impact on the heart's electrical activity, specifically influencing parameters related to ventricular repolarization, like how the P-wave spreads. This is especially beneficial for individuals dealing with type 2 diabetes mellitus (T2DM). What's noteworthy is that dapagliflozin effectively decreased the occurrence of adverse events linked to atrial fibrillation or atrial flutter (AFL) in individuals with heightened risks due to diabetes. [
119]. This positive impact on atrial fibrillation persisted, regardless of whether the person had a complicated history of atrial fibrillation, a previous heart attack, or heart failure [
120].
The significant benefits of dapagliflozin were consistent across all patients, regardless of their initial NT-proBNP concentration. Notably, individuals with higher NT-proBNP concentrations experienced the most pronounced advantages from dapagliflozin treatment [
121]
In the IMPRESS-AF trial, where Shantsila et al. [
122] took the reins, they set out to explore how spironolactone could impact exercise tolerance, quality of life, and diastolic function in individuals dealing with permanent atrial fibrillation (AF) and having preserved cardiac function. Despite the sincere efforts with spironolactone, it's disheartening that there wasn't any significant boost observed in exercise capacity, cardiac function, or overall quality of life. Another study led by Kotecha and team [
123] compared the effects of digoxin and bisoprolol on heart rate in atrial fibrillation, uncovering no substantial differences in how patients perceived their quality of life between the two treatments. These results suggest that, disappointingly, spironolactone may not bring about significant enhancements in terms of boosting exercise tolerance and overall well-being for individuals dealing with atrial fibrillation who are on digoxin. However, it's interesting to observe that symptoms did show considerable differences between the groups, with many patients in the digoxin group reporting a noteworthy two-notch improvement [
123,
124] The use of bisoprolol in patients with heart failure showed clinical benefit in improving QoL . These findings suggest that the choice of rate control therapy in AF should consider factors beyond QoL alone.
Obesity is associated with heart failure with preserved ejection fraction (HFpEF) and has been found to be a distinct phenotype in the HFpEF population [
125]. Obese patients with HFpEF have impaired left ventricular diastolic function, pressure a increased exposure, and other factors contributing to increased left ventricular pressure obesity Hemodynamic, neurohormonal, inflammatory, and mechanical mechanisms may have contributed to the development of HFpEF. May increase plasma volume, activate sympathetic nerve signaling, and inhibit the renin- angiotensin-aldosterone system fibrillation (AF) inflammation. Obesity AF is associated with an increased incidence, especially in patients with HFpEF, as abdominal obesity is associated with a higher risk of atrial fibrillation. Further research is needed to determine effective therapies for obesity-associated HFpEF [
126]. In particular, the Long-term Effect of Goal Directed Weight Management in an Atrial Fibrillation Cohort (LEGACY) study showed that weight reduction resulted in a reduction in AF burden and improvement in AF symptom severity [
127].
Dronedarone is a medication that researchers have explored for managing atrial fibrillation (AF) alongside heart failure (HF) with preserved and mildly reduced ejection fraction. The ATHENA trial demonstrated that dronedarone reduces the risk of cardiovascular events in patients with AF, but there is limited data on its role in patients with AF complicated by HFpEF and HFmrEF [
128]. A post-hoc analysis of the ATHENA trial showed that dronedarone can be a useful antiarrhythmic drug for early rhythm control, as it reduces the burden of AF/atrial flutter (AFL) progression to permanent AF/AFL and increases the regression to sinus rhythm (SR) compared to placebo [
129]. Another post-hoc analysis of the ATHENA trial found that dronedarone has both rhythm- and rate-controlling properties, as it prolongs the time to AF/AFL recurrence, reduces the need for electrical cardioversion, and decreases the likelihood of permanent AF/AFL [
130].
AF-HFpEF and Catheter Ablation:
A thorough examination of uncontrolled pre- and post-intervention data, along with observational controlled data and subsequent analysis from randomized controlled trials (RCTs), offers a holistic perspective on how catheter ablation influences individuals dealing with atrial fibrillation and heart failure with preserved ejection fraction (AF-HFpEF).
The uncontrolled before-and-after studies by Elkaryoni et al., Rattka et al., Sugumar et al., and Yamauchi et al. collectively demonstrate a positive impact of catheter ablation on AF-HFpEF patients. Notably, a 28.5% relative reduction in all-cause hospital admission rate within 120 days after AF ablation emphasizes the potential benefits in terms of healthcare utilization [
131,
132,
133,
134].
The observational studies by Fukui et al. and Arora et al. provide a comparative analysis between AF-HFpEF patients undergoing catheter ablation and those receiving medical therapy. These studies consistently show favorable outcomes in the ablation group, with lower all-cause hospital readmission rates, particularly for HF-related admissions. Lower AF hospital readmission rates in the ablation group highlight the potential efficacy of catheter [
135,
136].
The post-hoc analysis by Packer et al., derived from the CABANA trial, stands out as a key component of the discussion. The reduction in all-cause mortality by 60% in the AF-HFpEF subgroup undergoing catheter ablation compared to medical therapy is a striking finding. This supports the notion that catheter ablation not only addresses AF-related outcomes but also significantly impacts overall survival in HFpEF patients [
137].
Several studies, including Rattka et al., Sugumar et al., and Yamauchi et al., delve into the remission of HFpEF following catheter ablation. The observed rates of remission, ranging from 43% to 77% after single or multiple procedures, underscore the potential for catheter ablation to modify the course of HFpEF. The improvement in NYHA functional class, along with reductions in left atrial diameter and natriuretic peptides, further supports the positive impact on HFpEF parameters [
132,
133,
134].
The research conducted by Fukui and colleagues, Arora and team, as well as findings from Packer's study consistently show that individuals who underwent catheter ablation experienced lower rates of readmission to hospitals, considering both general causes and those related to heart failure. Notably, Packer's research goes even further to highlight a substantial decrease in overall mortality rates. This highlights the potential life-saving value of catheter ablation for patients with atrial and heart failure with preserved ejection fraction [
135,
136,
137].
The RACE-AF trial, which delves into the comparison between rate and rhythm control in HFpEF patients with AF, indicates that both approaches, using medications, are equally effective in preventing mortality and hospitalization. This highlights the potential life-saving benefit associated with catheter ablation for individuals managing atrial fibrillation and heart failure with preserved ejection fraction. It emphasizes the need for a personalized approach in managing AF within the HFpEF population. In contrast, the post hoc analysis of CABANA-HF demonstrates the potential superiority of pulmonary vein isolation (PVI) over medications, indicating that catheter-based interventions might play a pivotal role in certain HFpEF populations [
137,
138].
RACE 3, which specifically targets HFpEF patients with AF, advocates for a comprehensive approach involving rhythm control for AF along with treatment for HF, as opposed to focusing solely on comorbidity management. The data suggests that this combined strategy, predominantly utilizing medications, is superior in maintaining sinus rhythm. This aligns with the growing recognition of the need for a holistic approach to address both AF and HF components in HFpEF [
139].
The EAST-AFNET4 trial, encompassing stable HF patients with a significant HFpEF representation, emphasizes the potential benefits of early rhythm control over usual care. This long-term study indicates that early intervention, including PVI in some cases, results in reduced rates of cardiovascular death, stroke, and HF or acute coronary syndrome (ACS)-related hospital stays. This finding highlights the importance of timely and targeted management strategies to improve outcomes in HFpEF patients with AF[
140].
To explore treatment strategies for individuals managing atrial fibrillation (AF) and heart failure with preserved ejection fraction (HFpEF), a study led by Kelly et al compared the effectiveness of rhythm control and rate control. The findings from this study indicate that individuals undergoing rhythm control exhibited a lower risk of all- cause mortality when compared to those under rate control. The hazard ratio (HR) was determined to be 0.71, albeit with a p-value of 0.066, suggesting a trend towards a significant difference in favor of rhythm control[
141]. Another study, led by Zhang and colleagues, delved into the consequences of incident atrial fibrillation (AF) on individuals with heart failure with preserved ejection fraction (HFpEF). The results of this study revealed that the occurrence of AF, irrespective of ejection fraction (EF), was linked to poorer outcomes for individuals with HFpEF [
142]. Additionally, Machino- Ohtsuka et al. found that maintenance of sinus rhythm was associated with improved clinical outcomes in patients with HFpEF and AF [
143].
The BNP level significantly decreased irrespective of the index rate control status, and freedom from AF recurrence was an independent predictor of HF remission, defined as BNP <100 pg/mL at 1 year, in the HFpEF group. Conclusion Catheter ablation is highly feasible for restoring sinus rhythm in non-paroxysmal AF with coexisting HFpEF, thereby improving cardiac function and BNP levels [
134,
144].
Administering catheter ablation to control atrial fibrillation (AF) in individuals with heart failure with preserved ejection fraction (HFpEF) might have adverse effects on the function of the left atrium (LA). This could affect various aspects, such as LA reservoir, conduit, booster pump, and neurohormonal functions. The procedure may disrupt LA electromechanical synchrony and potentially result in a proportional decrease in LA ejection fraction, linked to the volume of scar tissue post-ablation. These observations highlight the complexities and potential consequences associated with catheter ablation in AF-HFpEF cases, emphasizing the importance of careful consideration and monitoring [
145,
146]. LA compliance may also be reduced, leading to increased filling pressures and pulmonary hypertension, known as stiff LA syndrome [
146]. Heart failure symptoms and cardiac biomarkers continued to improve in individuals with heart failure preserved ejection fraction (HFpEF) despite good heart rate monitoring during follow-up. The subsequent echocardiographic assessments uncovered a continued advancement of unfavorable changes in the left atrium, with no notable enhancement in diastolic function among HFpEF patients. Notably, those without HFpEF reported an improvement in their overall quality of life, whereas individuals with HFpEF continued to experience a comparatively lower total physical component score (with a median of 41.5 versus 53.4; P < 0.004). This underscores the persistent challenges associated with HFpEF and emphasizes the need for holistic approaches to address its multifaceted impact on patients [
147].