Atrial arrhythmias and heart failure: a "modern view" of an old paradox

BACKGROUND

Heart failure (HF) and atrial arrhythmias (AAs) are two clinical conditions that characterize the daily clinical practice of cardiologists. In this perspective review, we analyze the shared etiopathogenetic pathways of atrial arrhythmias, which are the most common cause of atrial arrhythmias-induced cardiomyopathy (AACM) and HF.

HYPOTHESIS

The aim is to explore the pathophysiology of these two conditions considering them as a "unicum", allowing the definition of a cardiovascular continuum where it is possible to predict the factors and to identify the patient phenotype most at risk to develop HF due to atrial arrhythmias.

METHODS

Potentially eligible articles, identified from the Electronic database (PubMed), and related references were used for a literature search that was conducted between January 2022 and January 2023. Search strategies were designed to identify articles that reported atrial arrhythmias in association with heart failure and vice versa. For the search we used the following keywords: atrial arrhythmias, atrial fibrillation, heart failure, arrhythmia-induced cardiomyopathy, tachycardiomyopathy. We identified 620 articles through the electronic database search. Out of the 620 total articles we removed 320 duplicates, thus selecting 300 eligible articles. About 150 titles/abstracts were excluded for the following reasons: no original available data, no mention of atrial arrhythmias and heart failure crosstalk, very low quality analysis or evidence. We excluded also non-English articles. When multiple articles were published on the same topic, the articles with the most complete set of data were considered. We preferentially included all papers that could provide the best evidence in the field. As a result, the present review article is based on a final number of 104 references.

RESULTS

While the pathophysiology of AACM and Heart Failure with reduced ejection fraction (HFrEF) has been studied in detail over the years, the causal link between atrial arrhythmias and heart failure with Preserved Ejection Fraction (HFpEF) has been often subject of interest. HFpEF is strictly related to AAs, which has always been considered significant risk factor. In this review we described the pathophysiological links between atrial fibrillation and heart failure (Fig. 1). Furthermore, we illustrated and discussed the preclinical and clinical predicting factors of AF and HFpEF, and the corresponding targets of the available therapeutic agents. Finally, we outlined the patient phenotype at risk of developing AF and HFpEF.

CONCLUSIONS

In this review, we underline how these two clinical conditions (AF and HFpEF) represent a "unicum" and, therefore, should be considered as a single disease that can manifest itself in the same phenotype of patients but at different times. Furthermore, considering that today we have few therapeutic strategies to treat these patients, it would be good to make an early diagnosis in the initial stages of the disease or intervene even before the development of signs and symptoms of HF. This is possible only by paying greater attention to patients with predisposing factors and carrying out a targeted screening with the correct diagnostic methods. A systemic approach aimed at improving the immuno-metabolic profile of these patients by lowering the body mass index, threatening the predisposing factors, lowering the mean heart rate and reducing the sympathetic nervous system activation is the key strategy to reduce the clinical impact of this disease. This article is protected by copyright. All rights reserved.

365 ANALYSIS OF PIVOT POINTS AND SLOW CONDUCTION AREAS IN PATIENTS UNDERGOING ATRIAL FIBRILLATION ABLATION

Introduction

Little is known about progression of atrial fibrillation (AF) from paroxysmal to persistent form. Electrical remodeling may play a pivotal role in the arrhythmia transition. The aim of the study was the characterization of the atrial electrical substrate in patients suffering from AF.

Methods

Twenty-seven patients were included in the study (14 with paroxysmal AF and 13 with persistent AF). Two simultaneous electroanatomical maps of the left atrium were collected using PentaRay catheter using the parallel mapping feature [first map during sinus rhythm and a second one with an extrastimulus from coronary sinus (CS)]. We analyzed the propagation of the wavefront and we identified zones of abnormal conduction: slow conduction (SC) corridors and pivot points (PP). SC corridors were defined by the slowing of conduction velocity; pivot points were zones in which propagation pattern changed the direction of 90° or more. Maximum delay between the recording dipoles located at the extremities of the PentaRay splines was calculated. At each of these sites, EGMs were collected and analyzed in terms of amplitude and duration. We checked if areas of abnormal conduction during sinus rhythm were present or they disappeared by delivering an extrastimulus from the coronary sinus.

Results

The average number of collected EGMs per map was 4790 ± 1333 (PAF 4829 ± 1407; PsAF 4745 ± 1402).

Total abnormal conduction areas in the 27 patients were 62, 65% of which were slow conduction. Pivot points and slow conduction manifested a trend to cluster in some areas: both of them were mostly present at the ostia of pulmonary veins, in a specific segment between LAA ostium and mitral annulus and in the posterior wall. During sinus rhythm, pivot points were 29, while pacing from distal CS catheter the same zones showed normal conduction in 14 cases: they were still present in 60% in PAF group and 50% in PsAF. Slow conduction corridors, instead, show a trend to remain while pacing from CS: 76% in the first group and 78% in the second one.

Conclusions

SC corridors are fixed alterations of atrial substrate, while pivot sites may be more dynamic entities: both of them may have a key role in remodeling atrial structures and atrial fibrillation progression and maintenance. These may represent future targets for AF therapy and prevention.

27 PROGNOSTIC FACTORS IN POST-OPERATIVE ATRIAL FIBRILLATION: A COHORT STUDY IN 53.387 PATIENTS

Introduction

Post-operative atrial fibrillation (POAF) represents the most common arrhythmia in the post-operative setting, with a peak incidence from day 0 to 5 after surgery and it represents a main cause of morbidity, mortality, length of stay, thromboembolic events and stroke. Cardiothoracic surgery has the highest rates of POAF, while data about other surgeries are contrasting amongst various studies. Aim of this study was to detect POAF onset in the 28 days after surgery and to better assess its predictors, especially the role of inflammation.

Methods

This is a retrospective single center cohort study of 53.387 patients undergoing surgery from January 2016 to January 2020. Patients were classified in four groups according to types of surgery performed: (I) orthopedic surgery, (II) not thoracic nor abdominal surgery, (III) abdominal and esophageal surgery and (IV) lung and cardiovascular surgery. Kaplan–Meier estimates were used to draw the cumulative incidence curves by surgery groups; finally, they were compared with a log-rank test. Furthermore, multivariable Cox proportional hazards (PH) models of prognostic factors were used. Confounders were selected according to a review of the literature, statistical relevance, and consensus opinion by an expert group of physicians and methodologists. After fitting the model, the PH assumption was examined on the basis of Schoenfeld residual.

Results

The primary endpoint of AF onset occurred in 570 patients (1.1%) with a mean incidence after surgery of 3.4±2.6 days. 90 patients died (0.17%) after an average of 13.7±8.4 days.

The Kaplan-Meier analysis showed the lowest 28-day event-free survival in group IV and the highest in group I (log-ranks test p=0.0001). In patients who developed AF, levels of C-Reactive Protein (CRP) were higher than the others (mean 0,70+0.03 log10 mg/dL versus mean 0,40+0.01 log10 mg/dl; p <0.0001) with higher levels in group III and group IV. In the univariable Cox regression, CRP was a strong predictor of AF (HR per 1 unit increase in log-scale, 2.64; 95% C.I,1.74–4.0; p<0.0001). This was confirmed at the multivariable analysis, adjusting for confounding factors like age, gender, length of stay in hospital and group of surgery (adjusted HR per 1 mg/dL increase in log-scale, 1.81; 95% CI,1.18–2.79; p = 0.007). Other strong predictors of POAF were age (HR per 1 year increase, 1.06; 95% CI, 1.04–1.08; p< 0.0001) and surgery of group III and IV (HR, 23.62; 95% CI, 5.65–98.73; p< 0.0001 and HR,6.26; 95% CI, 1.48–26.49; p 0.013, respectively).The PH assumption was not violated (p=0.12).

Conclusions

POAF represents a frequent complication of surgery and major burden for healthcare. Inflammation may represent a major driver in its pathophysiology, especially in non-cardiac surgery, in which manipulation of cardiac tissue is avoided. This may explain the poor response to antiarrhythmic drugs and its self-limiting nature, which expires when post-operative inflammation turns off.

Right atrial appendage firing in atrial fibrillation

Background

The role of atrial fibrillation (AF) drivers located at the left atrium, superior vena cava, crista terminalis and coronary sinus (CS) is well established. While these regions are classically targeted during catheter ablation, the role of right atrial appendage (RAA) drivers has been incompletely investigated.

Objective

To determine the prevalence and electrophysiological characteristics of AF driver’s arising from the RAA.

Materials and methods

We conducted a retrospective analysis of clinical and procedural data of 317 consecutive patients who underwent an AF ablation procedure after bi-atrial mapping (multipolar catheter). We selected patients who presented with a per-procedural RAA firing (RAAF). RAAF was defined as the recording of a sustained RAA EGM with a cycle length shorter than 120 ms or 120 < RAAF CL ≤ 130 ms and ratio RAA CL/CS CL ≤ 0.75.

Results

Right atrial/atrium appendage firing was found in 22 patients. The prevalence was estimated at 7% (95% CI, 4–10). These patients were mostly men (72%), median age: 66 yo ± 8 without structural heart disease (77%). RAAFs were predominantly found in paroxysmal AF patients (63%, 32%, and 5% for paroxysmal, short standing and long-standing AF, respectively, p > 0.05). RAAF median cycle length was 117 ms ± 7 while CS cycle length was 180 ms ± 10 (p < 0.01).

Conclusion

In 317 consecutive AF ablation patients (22 patients, 7%) the presence of a high-voltage short-cycle-length right atrial appendage driver (RAAF) may conclusively be associated with AF termination. This case series exemplifies the not-so-uncommon role of the RAA in the perpetuation of AF.

ITER collective Thomson scattering-Preparing to diagnose fusion-born alpha particles (invited)

The ITER Collective Thomson scattering (CTS) diagnostic will measure the dynamics of fusion-born alpha particles in the burning ITER plasma by scattering a 1 MW 60 GHz gyrotron beam off fast-ion induced fluctuations in the plasma. The diagnostic will have seven measurement volumes across the ITER cross section and will resolve the alpha particle energies in the range from 300 keV to 3.5 MeV; importantly, the CTS diagnostic is the only diagnostic capable of measuring confined alpha particles for energies below ∼1.7 MeV and will also be sensitive to the other fast-ion populations. The temporal resolution is 100 ms, allowing the capture of dynamics on that timescale, and the typical spatial resolution is 10-50 cm. The development and design of the in-vessel and primary parts of the CTS diagnostic has been completed. This marks the beginning of a new phase of preparation to maximize the scientific benefit of the diagnostic, e.g., by investigating the capability to contribute to the determination of the fuel-ion ratio and the bulk ion temperature as well as integrating data analysis with other fast-ion and bulk-ion diagnostics.

409 Not all ST elevation are myocardial infarction: a lesson learned from ‘spiked helmet sign’

Aims

ST segment elevation is an electrocardiogram (ECG) finding first of all suggestive of acute coronary syndrome (ACS). However, there are other causes of ST segment elevation that seem to not have any relationship with coronary artery disease (CAD). One of these is the so-called ‘Spiked Helmet Sign’ (SHS), an ECG pattern characterized by upslope of ST segment before R wave onset that is reported to be found in critical illness and is associated with negative outcomes.

Methods and results

A 14-years-old boy came comatose (Glasgow Coma Scale = 4) to the Emergency Room after being run over by a car. He was immediately intubated and mechanically ventilated. Baseline ECG was reported to be normal, showing an incomplete right bundle branch block and a slightly prolonged QTc interval. CT-scan showed subarachnoid haemorrhage and multiple skull fractures requiring decompressive craniectomy. During hospitalization the patient developed marked hypotension complicated by rise of inflammation indexes and 12 lead ECG revealed new-onset of diffuse ST-segment elevation with spike-and-dome appearance mainly in lateral precordial leads, while lead II and V2 didn’t show any ST-segment alteration. Transthoracic echocardiogram was reported to be normal. Due to critical conditions and low likelihood of CAD, angiography wasn’t performed. The clinical course was worsened by occurrence of hyperkalaemia, acute kidney injury, and multiple episodes of ventricular tachycardia evolving in pulselessness electrical activity which required advanced life support. The patient subsequently died due to multi-organ failure, without the possibility of escalation therapy due to his status. SHS is an emerging ECG sign that is reported to be associated with critical conditions (mechanical ventilation, sepsis, bowel perforation) and in the majority of cases it is not related to CAD. It usually occurs in inferior leads (especially in case of abdominal disease) and in precordial leads (pneumothorax, aortic dissection, mechanical ventilation). Our patient had features consistent with previous cases reported in literature and, even if he experienced several episodes of cardiac arrest and blood exams revealed elevated values of cardiac troponin, the typical ECG pattern and the normal echocardiogram suggest SHS instead of ACS, avoiding unnecessary percutaneous coronary intervention. As reported in literature, even if in our case the appearance of this sign was associated with poor prognosis.

Conclusions

SHS mainly occurs in critically ill patients and is associated with death and poor outcomes. The potential pathophysiological mechanisms are still unclear. It is important to promptly recognize this pattern and differentiate between other causes of ST-segment elevation to select the appropriate therapy according to the setting. This is the first case-report among Italian hospitals of SHS.

Localized Atrial Tachycardia and Dispersion Regions in Atrial Fibrillation: Evidence of Spatial Concordance

Introduction: During atrial fibrillation (AF) ablation, it is generally considered that atrial tachycardia (AT) episodes are a consequence of ablation. Objective: To investigate the spatial relationship between localized AT episodes and dispersion/ablation regions during persistent AF ablation procedures. Methods: We analyzed 72 consecutive patients who presented for an index persistent AF ablation procedure guided by the presence of spatiotemporal dispersion of multipolar electrograms. We characterized spontaneous or post-ablation ATs’ mechanism and location in regard to dispersion regions and ablation lesions. Results: In 72 consecutive patients admitted for persistent AF ablation, 128 ATs occurred in 62 patients (1.9 ± 1.1/patient). Seventeen ATs were recorded before any ablation. In a total of 100 ATs with elucidated mechanism, there were 58 localized sources and 42 macro-reentries. A large number of localized ATs arose from regions exhibiting dispersion during AF (n = 49, 84%). Importantly, these ATs’ locations were generally remote from the closest ablation lesion (n = 42, 72%). Conclusions: In patients undergoing a persistent AF ablation procedure guided by the presence of spatiotemporal dispersion of multipolar electrograms, localized ATs originate within dispersion regions but remotely from the closest ablation lesion. These results suggest that ATs represent a stabilized manifestation of co-existing AF drivers rather than ablation-induced arrhythmias.

Phrenic nerve displacement by intrapericardial balloon inflation during epicardial ablation of ventricular tachycardia: Four case reports

BACKGROUND

Phrenic nerve (PN) injury is one of the recognized possible complications following epicardial ablation of ventricular tachycardia (VT). High-output pacing is a widely used maneuver to establish a relationship between the PN and the ablation catheter tip. An absence of PN capture is usually considered an indication that it is safe to ablate, and that successful ablation may be performed at adjacent sites. However, PN capture may impact the procedural outcome. Only a few cases have been reported in the literature that avoid PN injury by using different techniques.

CASE SUMMARY

Three patients with a previous history of myocarditis and one patient with ischemic cardiomyopathy underwent epicardial ablation for drug-refractory VT. Before the procedure, transthoracic echocardiogram, coronary angiogram, and cardiac magnetic resonance imaging were performed on all patients. Under general anesthesia, endo/epicardial three-dimensional anatomical and substrate maps of the left ventricle were accomplished. Before radiofrequency delivery, the course of the PN was identified by provoking diaphragmatic stimulation with high-output pacing from the distal electrode of the ablation catheter. In every case, a scar region with late potentials was mapped along the PN course. After obtaining another epicardial access, a second introducer sheath was placed, and a vascular balloon catheter was inserted into the epicardial space and inflated with saline solution to separate the PN from the epicardium. Once the absence of PN capture had been proven, radiofrequency was applied to aim for complete late potential elimination and avoid VT induction.

CONCLUSION

PN injury can occur as one of the complications following epicardial VT ablation procedures, and may prevent successful ablation of these arrhythmias. PN displacement by using large balloon catheters into the epicardial space seems to be feasible and reproducible, avoid procedure-related morbidity, and improve ablation success when performed in selected centers and by experienced operators.

Use of wearable cardioverter-defibrillator in association with catheter ablation for atrial fibrillation-related tachycardiomyopathy

Implantable cardioverter-defibrillator (ICD) is an effective therapy in patients known to be at high risk for sudden cardiac death (SCD). Nevertheless, ICD implantation is not indicated in transient or reversible causes of SCD. Wearable cardioverter-defibrillator is increasingly used for SCD prevention in patients with a transient risk of ventricular arrhythmia.

Usefulness of N-terminal pro-B-type natriuretic peptide levels in predicting residual myocardial ischemia in patients with ST elevation acute myocardial infarction

AIM

N-terminal pro-b-type natriuretic peptide (NT pro-BNP) is a neurohormone synthesized predominantly in ventricular myocardium. In patients with symptoms of heart failure, elevation in NT pro-BNP accurately identifies ventricular dysfunction. However, NT pro-BNP levels are not specific for ventricular dysfunction in patients who do not have overt symptoms of heart failure, suggesting that other cardiac processes such as myocardial ischemia may also cause elevation in NT pro-BNP. The study was aimed to determine whether NT pro-BNP elevations are associated with myocardial ischemia.

METHODS

One hundred and thirty patients (104 males, 26 females, mean age 61+12 years), with ST elevation acute myocardial infarction (STEMI) and preserved left ventricular ejection fraction (>45%) at echocardiography performed at entry, from February 2003 and February 2004 were enrolled. In all patients NT pro-BNP plasma levels were checked at entry and 4-5 days after symptoms onset. In addition, maximal or symptom-limited exercise treadmill test (Bruce protocol), and myocardial perfusion scintigraphy using [(99m)Tc]Tetrofosmin single photon emission computed tomography (SPECT) imaging were performed within 30 days of STEMI. Ischemia was defined as reversible perfusion abnormalities.

RESULTS

Of the 130 participants, 66 (51%) had inducible ischemia. Compared with patients in the lowest tertile, those in the highest tertile of NT pro-BNP had a greater significant risk of residual ischemia (odds ratio: 8.66; 95% CI, 3.90 to 19.24). Nevertheless patients in the highest tertile were older (64.19+/-10.80 years versus 55.90+/-9.67 years, P = 0.0001), had a lower left ventricular ejection fraction (49.70+13.46% versus 59.49+/-6.58%, P = 0.0001) and had a great rate of acute myocardial infarction (anterior acute myocardial infarction = 40.63% versus 25%).

CONCLUSIONS

Elevated levels of NT pro-BNP are associated with residual myocardial ischemia among patients with STEMI and preserved left ventricular ejection fraction, as demonstrated by perfusion defect on SPECT imaging, suggesting that these patients may need further evaluation for stratification of the future risk of fatal events. The observed association between NT pro-BNP levels and ischemia may explain because tests for NT pro-BNP are not specific for ventricular dysfunction among patients with coronary artery disease.

Assembly models for Papovaviridae based on tiling theory

A vital constituent of a virus is its protein shell, called the viral capsid, that encapsulates and hence provides protection for the viral genome. Assembly models are developed for viral capsids built from protein building blocks that can assume different local bonding structures in the capsid. This situation occurs, for example, for viruses in the family of Papovaviridae, which are linked to cancer and are hence of particular interest for the health sector. More specifically, the viral capsids of the (pseudo-) T = 7 particles in this family consist of pentamers that exhibit two different types of bonding structures. While this scenario cannot be described mathematically in terms of Caspar-Klug theory (Caspar D L D and Klug A 1962 Cold Spring Harbor Symp. Quant. Biol. 27 1), it can be modelled via tiling theory (Twarock R 2004 J. Theor. Biol. 226 477). The latter is used to encode the local bonding environment of the building blocks in a combinatorial structure, called the assembly tree, which is a basic ingredient in the derivation of assembly models for Papovaviridae along the lines of the equilibrium approach of Zlotnick (Zlotnick A 1994 J. Mol. Biol. 241 59). A phase space formalism is introduced to characterize the changes in the assembly pathways and intermediates triggered by the variations in the association energies characterizing the bonds between the building blocks in the capsid. Furthermore, the assembly pathways and concentrations of the statistically dominant assembly intermediates are determined. The example of Simian virus 40 is discussed in detail.