Reversal of atrial remodeling after cardioversion of persistent atrial fibrillation measured with magnetocardiography

Clinical magnetocardiography: the unshielded bet-past, present, and future

Magnetocardiography (MCG), which is nowadays 60 years old, has not yet been fully accepted as a clinical tool. Nevertheless, a large body of research and several clinical trials have demonstrated its reliability in providing additional diagnostic electrophysiological information if compared with conventional non-invasive electrocardiographic methods. Since the beginning, one major objective difficulty has been the need to clean the weak cardiac magnetic signals from the much higher environmental noise, especially that of urban and hospital environments. The obvious solution to record the magnetocardiogram in highly performant magnetically shielded rooms has provided the ideal setup for decades of research demonstrating the diagnostic potential of this technology. However, only a few clinical institutions have had the resources to install and run routinely such highly expensive and technically demanding systems. Therefore, increasing attempts have been made to develop cheaper alternatives to improve the magnetic signal-to-noise ratio allowing MCG in unshielded hospital environments. In this article, the most relevant milestones in the MCG's journey are reviewed, addressing the possible reasons beyond the currently long-lasting difficulty to reach a clinical breakthrough and leveraging the authors' personal experience since the early 1980s attempting to finally bring MCG to the patient's bedside for many years thus far. Their nearly four decades of foundational experimental and clinical research between shielded and unshielded solutions are summarized and referenced, following the original vision that MCG had to be intended as an unrivaled method for contactless assessment of the cardiac electrophysiology and as an advanced method for non-invasive electroanatomical imaging, through multimodal integration with other non-fluoroscopic imaging techniques. Whereas all the above accounts for the past, with the available innovative sensors and more affordable active shielding technologies, the present demonstrates that several novel systems have been developed and tested in multicenter clinical trials adopting both shielded and unshielded MCG built-in hospital environments. The future of MCG will mostly be dependent on the results from the ongoing progress in novel sensor technology, which is relatively soon foreseen to provide multiple alternatives for the construction of more compact, affordable, portable, and even wearable devices for unshielded MCG inside hospital environments and perhaps also for ambulatory patients.

Atrial remodeling and atrial fibrillation recurrence after catheter ablation : Past, present, and future developments

The term "atrial remodeling" is used to describe the electrical, mechanical, and structural changes associated with the presence of an arrhythmogenic substrate for atrial fibrillation. Rhythm control therapy may slow down or even reverse progressive atrial remodeling. Atrial remodeling has long been recognized as an important predictor of clinical outcomes and therapeutic success, but recent advances have highlighted its clinical relevance and revealed the implications of specific anatomical changes such as atrial asymmetry or shape. This has opened the path to computational precision medicine that captures these data in detail and combines them with other factors, to provide patient-specific solutions. The goal of precision medicine lies in improving clinical outcomes, reducing costs, and avoiding unnecessary procedures. In this article, we review the history of atrial remodeling and we summarize the insights from our research on anatomical atrial remodeling and its association with rhythm outcomes after catheter ablation. Finally, we present recent advances in the field, reflecting the beginning of a new technological era that will enable us to improve patient care by personalized patient-specific medicine.

Predictive value of unshielded magnetocardiographic mapping to differentiate atrial fibrillation patients from healthy subjects

BACKGROUND

P-wave duration, its dispersion and signal-averaged ECG, are currently used markers of vulnerability to atrial fibrillation (AF). However, since tangential atrial currents are better detectable at the body surface as magnetic than electric signals, we investigated the accuracy of magnetocardiographic mapping (MCG), recorded in unshielded clinical environments, as predictor of AF occurrence.

METHODS

MCG recordings, in sinus rhythm (SR), of 71 AF patients and 75 controls were retrospectively analyzed. Beside electric and magnetic P-wave and PR interval duration, two MCG P-wave subintervals, defined P-dep and P-rep, were measured, basing on the point of inversion of atrial magnetic field (MF). Eight parameters were calculated from inverse solution with "Effective Magnetic Dipole (EMD) model" and 5 from "MF Extrema" analysis. Discriminant analysis (DA) was used to assess MCG predictive accuracy to differentiate AF patients from controls.

RESULTS

All but one (P-rep) intervals were significantly longer in AF patients. At univariate analysis, three EMD parameters differed significantly: in AF patients, the dipole-angle-elevation angular speed was lower during P-dep (p < 0.05) and higher during P-rep (p < 0.001) intervals. The space-trajectory during P-rep and the angle-dynamics during P-dep were higher (p < 0.05), whereas ratio-dynamics P-dep was lower (p < 0.01), in AF. At DA, with a combination of MCG and clinical parameters, 81.5% accuracy in differentiating AF patients from controls was achieved. At Cox-regression, the angle-dynamics P-dep was an independent predictor of AF recurrences (p = 0.037).

CONCLUSIONS

Quantitative analysis of atrial MF dynamics in SR and the solution of the inverse problem provide new sensitive markers of vulnerability to AF.

Optimum Risk Assessment for Stroke in Atrial Fibrillation: Should We Hold the Status Quo or Consider Magnitude Synergism and Left Atrial Appendage Anatomy?

Thromboembolic stroke and systemic embolism are generally agreed to be the major morbidity/mortality concerns for patients with AF. However, the risk of thromboembolism is not the same for all AF patients. Both AF and comorbidities must interact synergistically to create the risk for thromboembolism. But, is the synergism dichotomous - AF present or absent, comorbid disorder present or absent - or does synergism have magnitude, depending on the number and severity of the associated disorders and the amount of time one is in AF? This review discusses the current risk-score contributors and options for assessing risk of thromboembolism in AF patients, and what their combined roles might be. Also covered is the consideration of left atrial appendage anatomy in this context.

Electrocardiographic features: Various atrial site pacing

Atrial pacing is done for either symptomatic sinus node dysfunction (SND) or for maintenance of atrio-ventricular synchrony in a dual chamber pacemaker. Conventionally, atrial lead is placed in the right atrial appendage. Atrial conduction disorder in patients with permanent pacing results in higher incidence of atrial fibrillation. Atrial septal pacing has emerged as a solution to this problem. So, it is extremely important to understand the different features of paced P wave from various atrial pacing sites. Conventional right atrial appendage pacing in presence of atrial conduction disorder results in marked latency with prolonged P wave duration with reduced amplitude. The morphology is similar to sinus rhythm. Atrial septal pacing causes short and sharp P wave with negative polarity in inferior leads and positive polarity in lead V1 in lower septal pacing, whereas positive polarity in inferior leads and negative polarity in lead V1 during pacing from upper septum.

Early Cardioversion in Atrial Fibrillation: Earlier Is Better, but Not Always and (Maybe) Not Immediately

Atrial fibrillation (AF) is the most common cardiac arrhythmia in humans. One of its important features is the tendency to become more persistent over time, even in the absence of underlying progressive heart disease. Conversion and maintenance of sinus rhythm by pharmacological or electrical methods become increasingly difficult the longer the arrhythmia persists. Electrical, mechanical, structural, and autonomic remodeling processes have been implicated in the mechanisms of AF initiation, perpetuation, and progression. Prevention or reversal of these remodeling processes can halt the progression of the disease. Cardioversion is a powerful tool and rhythm control is a widely used strategy in the management of AF. However, important questions remain unanswered regarding not only if, but also when to perform cardioversion. There are observations from past trials and clinical situations that support attempting to restore sinus rhythm, but further prospective randomized clinical trials are needed. Optimal timing of cardioversion remains somewhat uncertain, but it appears to be some time after the first few hours and before the first few months: the earlier, the better, but not always, and maybe not immediately, and it has to be tailored to the clinical situation and its many variables. This review is intended to summarize the evidence supporting early intervention for the prevention of remodeling in patients with AF.

Genetic ACE I/D polymorphism and recurrence of atrial fibrillation after catheter ablation

BACKGROUND

The angiotensin-converting enzyme (ACE) deletion allele, ACE D, is associated with increased cardiac ACE activity, cardiac fibrosis, and adverse outcomes in cardiovascular disease and has been linked with failure of antiatrial fibrillation (anti-AF) drug treatment. This study tested the hypothesis that the ACE gene insertion/deletion polymorphism associates with AF recurrence after catheter ablation.

METHODS AND RESULTS

In 238 consecutive patients (69% male; mean age, 58±11 years) undergoing catheter ablation of paroxysmal (59%) or persistent (41%) AF, the ACE insertion/deletion polymorphism was genotyped using polymerase chain reaction. After a blanking period of 3 months, AF recurrence (defined as any atrial arrhythmia lasting ≥30 s) was detected using serial 7-day Holter ECG recordings after 3, 6, and 12 months. AF recurrence was observed in 39% and was associated with persistent AF, longer history of AF, previous antiarrhythmic drug use, previous use of diuretics, increased left atrial diameter, increased left ventricular end-diastolic diameter, additional linear ablation lesions, and ACE DD polymorphism. In multivariable analysis, left atrial diameter (odds ratio, 1.111; 95% confidence interval, 1.040-1.187; P=0.002) and ACE DD genotype (odds ratio, 2.251; 95% confidence interval, 1.056-4.798; P=0.036) remained predictors for AF recurrence.

CONCLUSIONS

Left atrial enlargement and the ACE DD polymorphism are predictors for AF recurrence after catheter ablation. The association between the ACE DD polymorphism and AF recidivism supports the use of genetic data for predicting response to AF therapies and highlights the role of fibrosis in AF development.

Diagnostic value of magnetocardiography in coronary artery disease and cardiac arrhythmias: a review of clinical data

Despite the availability of several advanced non-invasive diagnostic tests such as echocardiography and magnetic resonance imaging, electrocardiography (ECG) remains as the most widely used diagnostic technique in clinical cardiology. ECG detects electrical potentials that are generated by cardiac electrical activity. In addition to electrical potentials, the same electrical activity of the heart also induces magnetic fields. These extremely weak cardiac magnetic signals are detected by a non-invasive, contactless technique called magnetocardiography (MCG), which has been evaluated in a number of clinical studies for its usefulness in diagnosing heart diseases. We reviewed the basic principles, history and clinical data on the diagnostic role of MCG in coronary artery disease and cardiac arrhythmias.

Asymmetric dimethylarginine concentration and recurrence of atrial tachyarrythmias after catheter ablation in patients with persistent atrial fibrillation

PURPOSE

It has been reported that elevation of asymmetric dimethylarginine (ADMA) concentration is involved in atrial fibrillation (AF) process. The purpose of this study was to determine whether ADMA concentration is related to recurrences of AF after catheter ablation.

METHODS

A total of one hundred and thirty-eight patients with persistent AF (49.91 ± 7.23 years), but without known heart disease, who underwent successful mapping and catheter ablation were included. Serum ADMA levels were measured 1 day before the catheter ablation.

RESULTS

After a mean follow-up period of 285 days (range, 98-651 days), 80 (58%) patients underwent the AF recurrence. Comparing with no AF recurrence group, the serum ADMA concentration, left atrial diameter, and persistent duration of AF in patients with AF recurrence group were significantly increased. Left atrial diameter, persistent duration of AF, and the number of non-pulmonary vein ectopy ablation were increased when serum ADMA concentration was elevated. In addition, AF recurrences were significantly increased when serum ADMA concentration was elevated. A multivariable Cox regression analysis demonstrated that the elevated ADMA concentration [hazard ration (95% CI), 4.59 (1.81-11.62); P = 0.001], the left atrial diameter [1.35 (1.18-1.55), P < 0.001], and the number of non-pulmonary vein ectopy ablation [1.94 (1.18-3.18), P = 0.009] were independent factors associated with the AF recurrence after catheter ablation.

CONCLUSIONS

This study demonstrated that (1) serum ADMA concentrations were associated with non-PV ectopies and (2) increased serum ADMA concentrations were associated with higher rate of AF recurrence after catheter ablation in patients with persistent AF, supporting our hypothesis that ADMA might participate in the process of atrial remodeling.