P-wave beat-to-beat analysis to predict atrial fibrillation recurrence after catheter ablation

Introduction

Identification of patients prone to atrial fibrillation (AF) relapse after catheter ablation is essential for better patient selection and risk stratification.

Purpose

The current prospective cohort study aims to validate a novel P-wave index based on beat-to-beat (B2B) P-wave morphological and wavelet analysis designed to detect patients with low burden AF, as a predictor of AF recurrence within a year after successful catheter ablation.

Methods

12-lead ECG and 10-minute vectorcardiogram (VCG) recordings were obtained from 138 consecutive patients scheduled for AF ablation. Pre-ablation B2B P-wave index, along with standard P-wave indices, clinical scores and patients history and physical examination parameters were evaluated as AF recurrence predictors.

Results

Univariate analysis revealed that patients with higher B2B P-wave index had a two-fold risk for AF recurrence (HR: 2.35, 95% CI: 1.24–4.44, p: 0.010). Prolonged P-wave, interatrial block, early AF recurrence, female gender, heart failure history, previous stroke, and CHA2DS2-VASc score ≥2 were also found to be related to higher recurrence rate. Multivariate analysis of predictors that can be assessed before ablation revealed that B2B P-wave index, along with heart failure history and history of previous stroke or transient ischemic attack are independent predicting factors of AF relapse.

Conclusion

B2B P-wave morphology and wavelet analysis, is a promising, non-invasive technique, able to identify patients prone to AF recurrence after pulmonary veins ablation. Further studies are needed to assess the predictive value of B2B index with greater accuracy and evaluate a possible relationship with atrial substrate analysis.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Hellenic Society of Cardiology

Total atrial conduction time and its relationship with morphological & functional characteristics in hypertrophic cardiomyopathy

Funding Acknowledgements

Type of funding sources: None.

Background

Total atrial conduction time (TACT), estimated by tissue Doppler imaging (TDI), is an index reflecting left atrial (LA) structural and electrical remodeling, connected to atrial fibrillation (AF) development and heart failure progression in various substrates. In hypertrophic cardiomyopathy (HCM), the significance of TACT beyond AF and its determinants are not fully investigated.

Purpose

Aim of this study was to estimate TACT in a cohort of HCM patients without AF history and to examine its relationship with other parameters of atrial myopathy, such as LA volume index (LAVI) or LA reservoir strain (LARS). Additionally, to investigate TACT correlation with other phenotypic and functional characteristics of HCM.

Methods

 We included 50 HCM patients (60 ± 16 years, 80% male, maximum wall thickness 18.6 ± 4.1mm) without history of AF who have consecutively undergone 2D-speckle tracking echocardiography and cardiovascular magnetic resonance (CMR) with late gadolinium enhancement (LGE). TACT was measured from the onset P wave on electrocardiogram to the peak A’ wave of the lateral LA wall using TDI (left panel). Burden of fibrosis (percentage of LV mass) was defined by LGE extent (>5 standard deviations compared to nulled myocardium) in CMR slices. Cut-off points for TACT, LAVI and LARS were adopted by literature (≥115 msec, ≥34 mL/m2 and <21.3 % respectively).

Results

 All HCM patients had preserved EF (61.8 ± 8%), while 13 (26%) presented outflow tract obstruction and 4 (8%) diastolic dysfunction stage≥2. LGE was observed in 32 patients (64%) occupying 7.2 ± 5% of left ventricular (LV) mass. Mean TACT was 139.9 ± 22 msec, with LAVI being 30.8 ± 16.1 mL/m2 and LARS 27.6 ± 13.9%. After assessing prevalence of atrial myopathy parameters, 41 patients (82%) presented a prolonged (≥115 msec) TACT with only 13 of them having also a significantly dilated LA (≥34 mL/m2) and 16 an impaired LARS. Among HCM demographic, phenotypic and functional characteristics tested, age and LV mass index were found to be the only independent regressors of TACT (r = 0.54, p < 0.0005 and r = 0.44, p = 0.002 respectively, right panels). On the contrary, no significant correlation was established between TACT and traditional diastolic dysfunction indices such as E/E’ or fibrosis extent.

Conclusions

Atrial electro-mechanical delay assessed through TDI based TACT, is very frequent among HCM patients irrespective of AF and even before LA dilatation and LA strain impairment.  Age and hypertrophy magnitude are the main determinants of TACT, the prognostic significance of which remains to be further elucidated. Abstract Figure.

Strain-volume loops for assessment of diastolic function in hypertrophic cardiomyopathy

Funding Acknowledgements

Type of funding sources: None.

Background

Diastolic function assessment in patients with hypertrophic hearts and preserved ejection fraction (EF) is a rather challenging task, necessitating the introduction of new parameters. Strain-volume loops (SVLs), based on simultaneous frame-by-frame strain and volume changes’ recordings acquired by means of three-dimensional (3D) speckle tracking imaging, is an innovative tool which has been applied in various substrates. The ability of SVLs to assess diastolic function in hypertrophic cardiomyopathy (HCM) has not been investigated until now.

Purpose

Aim of this study was to investigate potential correlations between SVLs, traditional diastolic function indices and phenotypic features of HCM (thickness, obstruction and fibrosis) that may also reflect myocardial "stiffness".

Methods

 We included 40 HCM patients (54.1 ± 14.3 years, 82.5% male, maximum wall thickness 19.3 ± 4.8mm) who have consecutively undergone 3D-speckle tracking echocardiography (panel A) and cardiovascular magnetic resonance (CMR) with late gadolinium enhancement (LGE). Values of 3D strain were plotted vs. volume for each frame to build an SVL. Peak of radial, longitudinal and circumferential systolic strain (Rsp, Lsp, and Csp, respectively), systolic slopes of the loops (RsSl, LsSl, CsSl), strain to end-diastolic volume (EDV) ratios (Rs/V, Ls/V, Cs/V) as well as the extent of systolic-diastolic uncoupling (difference between systolic and diastolic strain for the same volume) were computed for the analysis. Left atrial volume index (LAVI), E/E’ and tricuspid regurgitation velocity (TRvel) were measured to define diastolic dysfunction (DD) stage. Burden of fibrosis was evaluated by LGE extent in CMR slices.

Results

 All HCM patients had preserved EF (60.5 ± 5,7%), while 16 (40%) had LV outflow tract obstruction (LVOTO > 30 mm Hg at rest). Mean LV mass index was 78.9 ± 14.5 g (evaluated by 3D echocardiography). LGE was observed in 23 patients (57.5%) occupying 5.2 ± 4.5% of LV mass. Concerning SVLs the following values were recorded for radial (Rsp 30.8 ± 9.8%, RsSl 0.4 ± 0.13 and Rs/V 0.25 ± 0.09), longitudinal (Lsp -9.4 ± 3.7%, LsSl 0.12 ± 0.06 and Ls/V 0.08 ± 0.04) and circumferential deformation (Csp -14.2 ± 3.5%, CsSl 0.18 ± 0.05 and Cs/V 0.11 ± 0.03). Traditional isolated diastolic indices (E/E’, LAVI, TRvel and DD stage) did not present significant correlations with SVL parameters or HCM phenotypic features. However, potentially "stiffer" hearts (combination of increased LVMI and fibrosis) presented a leftward transition of longitudinal SVLs, which also became wider (greater uncoupling) (panel B).

Conclusions

Traditional diastolic indices show modest only correlations with SVLs or HCM phenotypic characteristics, necessitating new approaches to DD of HCM patients. SVLs seem to be a promising-innovative tool for indirect assessment of myocardial "stiffness" and diastolic function. Abstract Figure.

Beat-to-beat P-wave analysis outperforms conventional P-wave indices in identifying patients with a history of paroxysmal atrial fibrillation, during sinus rhythm

Introduction

Atrial fibrillation (AF) is the most common arrhythmia and is associated with high risk of morbidity and mortality. In many patients, AF is of episodic character (paroxysmal AF – PAF), which makes the identification of these patients during sinus rhythm (SR) challenging.

Purpose

The aim of the present study is to compare the performance of beat-to-beat P-wave analysis with P-wave indices used as predictors of PAF, such as P-wave duration, area, voltage, axis, terminal force in V1, inter-atrial block or orthogonal type, in identifying patients with history of PAF during sinus rhythm.

Methods

Standard 12-lead ECG and 10-minute orthogonal ECG recordings were obtained from 40 consecutive patients with short history of PAF under no antiarrhythmic medication and 60 age- and sex- matched healthy controls. The P-waves on the 10-minute recordings were analyzed on a beat-to-beat basis and classified as belonging to a primary or secondary morphology according to previous study. Wavelet transform used to further analyze P-wave orthogonal signals of main morphology on a beat-to-beat basis.

Results

38 out of 327 studied features were found to differ significantly among the two groups. These features were tested for their diagnostic ability and receiver operating characteristic curves were ploted. Only 3 of them performed adequetly, with an area under curve (AUC) above 0.65; Two of them came from morphology analysis (percentage of beats following main morphology in axis X and Y) and one from wavelet analysis (max energy in high frequency zone -Y axis). Among standard P-wave indices, P-wave area in lead II was the one with the highest AUC (0.64).

Conclusion

Novel indices derived from beat-to-beat analysis outperform stadard P-wave markers in identifying patients with PAF history during sinus rhythm.

Funding Acknowledgement

Type of funding sources: None. ROC curves of most significant featuresAUC characteristics of P-wave indices

How intravenous iron therapy affects arrhythmia burden and functional status in patients with advanced heart failure and implantable devices

Background

Heart failure with reduced ejection fraction (HFrEF) is a disease that confers significant morbidity and mortality to patients. Patients suffer from increased arrhythmia burden; lethal ventricular arrhythmias are frequent. Iron deficiency (ID) is increasingly recognized as a common comorbidity that constitutes a further detriment to patients' cardiorespiratory capacity and an independent prognosticator of mortality. ID treatment with intravenous ferric carboxymaltose (IV FCM) has proven beneficial, improving QoL and exercise capacity in HFrEF patients with ID. Iron depletion is linked to disturbed myocyte electromechanical balance, especially in HF. However, the role of IV FCM arrhythmic burden in HFrEF patients with ID has not been examined.

Purpose

Investigate the effect of IV FCM treatment on the functional capacity, QoL and arrhythmic burden of in HFrEF patients with ID and cardiac implantable electronic devices (CIED).

Methods

HFrEF patients with ID and CIEDs were recruited from our outpatient HF clinic. CIED telemetry revealed their arrhythmic burden for the 6 months preceding IV FCM administration. Patients underwent physical examination, blood testing, 6-minute walk testing, 24-hour Holter monitoring, QoL quantification with the KCCQ and EQ-5D-5L questionnaires and repeat CIED telemetry at study baseline (IV FCM administration) and 6-months. Microvolt T-wave alternans (MTWA) and heart rate turbulence (HRT) slope and onset were quantified through the 24-hour ECG recordings. HRT results are reported as HRT0, HRT1 or HRT2 based on the number of abnormal HRT parameters.

Results

So far, 83 (aged 68.3±8.7 years, 82% male) out of a total of 96 recruited patients have completed the 6-month follow-up (3 of 83 died before the 6-month mark). Picture 1 contains patients' baseline characteristics and 6-month results. Patients received a mean of 1.43±0.61g of IV FCM during the follow-up period, which significantly ameliorated iron status (Picture 1). The 6MWD increased by 32.4m (95% CI: 14.7–47.2, P<0.001), as did the KCCQ total score (P=0.008). Patients' CIEDs recorded significantly more nsVTs in the 6 months preceding IV FCM administration (2.2±15.7 per month) opposed to the subsequent period (0.06±3.1 per month, P=0.006). Patients' MTWA improved at 6-months over baseline (P=0.004), and a trend for improvement in HRT scores was observed (P=0.06). Hospitalization-free survival curves of these time periods reveal a non-significant trend for lower hospitalization risk following IV FCM (HR=1.9, P=0.09).

Conclusions

After 6 months of IV FCM treatment, HFrEF patients with ID had significantly better exercise capacity and quality of life. Regarding arrhythmias, a tentative improvement in CIED- and Holter-derived arrhythmic markers was observed. Extended follow-up of a larger sample size will provide further insight for the effect of IV FCM in these patients' arrhythmic burden.

Funding Acknowledgement

Type of funding sources: None. Baseline and 6-month resultsHospitalization curves pre-post IV FCM

Left atrial coupling index versus left atrial function index in heart failure with reduced ejection fraction and iron deficiency

Background

Left atrial (LA) form and function has been the focus of extensive research in heart failure with reduced ejection fraction (HFrEF). The LA coupling index (LACI, see Picture 1 for definition) and the LA function Index (LAFI) have both been proposed as potent predictors of morbidity and mortality in HFrEF. Albeit promising, both parameters have drawbacks that could limit their usefulness in clinical settings - LACI can only be measured during sinus rhythm (SR), while LAFI calculation is arguably more involved. A side-by-side comparison of the two indices has not yet been performed.

Purpose

Investigate and compare the feasibility and efficacy of using LACI and LAFI as prognostic factors in HFrEF.

Methods

HFrEF patients that visited our outpatient HF clinic were invited to participate in the study. Clinical examination, 6-minute walk testing, and a full echocardiographic study were performed, the latter enabling quantification of LACI, LAFI, as well as most traditional echocardiographic predictors of HF prognosis (Picture 1). LACI and LAFI cut-offs of 6 and 25 respectively were defined in accordance with the relevant literature. Cox regression was performed to assess each parameter's correlation with risk of HF-related hospitalization and mortality over a 6-month follow-up period.

Results

In the end, 63 patients were included in the study (aged 69.3±9.7 years, 84% male). LACI could not be measured in 19 patients due to atrial tachycardia. The median LACI was 6.2 (8.7) while the median LAFI of the entire sample was 24.8 (44.5). LACI and LAFI correlated strongly (r=−0.813, p<0.001). Neither correlated significantly with the risk of HF-related hospitalization (Picture 1) or death in our sample (Picture 2). 6MWD was the only parameter to independently correlate with increased risk of hospitalization (HR=0.39, p<0.001) or death (HR=0.42, p=0.02).

Conclusions

The collinearity detected between LACI and LAFI indicate that both quantify similar aspects of left atrial (dys)function. That said, neither index had significant capability to predict hospitalization or death in our sample of HFrEF patients. Although a non-significant trend for higher LACI in patients with poorer prognosis was detected in our sample, it was also incalculable in 30% of patients, who were not in SR during echocardiography. Extended follow-up of an expanded sample size will enable more refined investigation of LACI's and LAFI's prognostic capacity.

Funding Acknowledgement

Type of funding sources: None. Hospitalization Cox regression resultsLACI and LAFI survival curves

P-wave beat-to-beat morphology analysis outperforms conventional P-wave indices in detecting patients with paroxysmal atrial fibrillation

Funding Acknowledgements

Type of funding sources: None.

Background

Atrial fibrillation (AF) - the most common sustained cardiac arrhythmia - while not a life-threatening condition itself, leads to an increased risk of stroke and high rates of mortality. Early detection and diagnosis of AF is a critical issue for all health stakeholders.

Purpose

The aim of this study is to compare the performance of standard P-wave indices with beat-to-beat P-wave morphological variability parameters in identifying patients with history of Paroxysmal Atrial Fibrillation (PAF).

Methods

Three-dimensional 1000Hz ECG digital recordings of 10 minutes duration were obtained from a total of 39 PAF patients and 60 healthy individuals. Following artifacts and ectopic beats removal, P‑wave morphology analysis was performed based on the dynamic application of the k‑means clustering process and main and secondary P-wave morphologies were identified. The percentage of P-waves following the main or the secondary morphology in each lead was calculated, as well as established indices such as Advanced Interatrial Block, P-wave duration, axis and area, P-wave Terminal Force in lead V1 and Orthogonal Leads Type 1, 2 or 3.

Results

9 out of 24 parameters studied, were found to be significantly different between the two groups. 7 of these indices were derived from morphology analysis and 2 from P-wave area. Logistic regression revealed that the percentage of P-waves allocated to main morphology in X axis performed better than all other indices in identifying patients with PAF history from healthy volunteers in terms of total accuracy and F1 measure.

Conclusion

P-wave beat-to-beat morphology analysis can identify PAF patients during normal sinus rhythm more efficiently than standard P-wave indices. Abstract Figure.

HFrEF patient activity levels during COVID-19 lockdown: A comparison between physical activity questionnaires and implantable devices data

Funding Acknowledgements

Type of funding sources: None.

Background

The ongoing COVID-19 pandemic is a major public health crisis of great risk to patients with cardiovascular comorbidities. Heart failure (HF) is a deadly chronic disease, a leading cause of hospitalizations worldwide and a great detriment to patients’ quality of life. HF therapy guidelines suggest prescribing physical activity to improve long-term outcomes. Self- or government- imposed behavioral modifications in response to COVID-19 ranging from avoiding social interactions to outright restrictions of movement (lockdowns) could compromise regular PA in HF patients, who constitute an extremely high-risk group.

Purpose

Investigate the effect of the national lockdown in Greece 23rd March – 4th May 2020) on the PA levels of patients suffering from HF with reduced ejection fraction (HFrEF) and cardiac implantable electronic devices (CIEDs).

Methods

HFrEF patients with CIEDs were included in the study. Participants answered the Physical Activity Questionnaire (PAQ) regarding the period before, during and after the 42-day national lockdown. CIED-derived daily activity levels for the corresponding periods were recorded through CIED telemetry. The differences in PAQ- and CIED-derived PA levels and sedentary time before, during and after the lockdown period were investigated.

Results

67 HFrEF patients participated in the study (mean age 69 ± 10.2y, 85% male). Activity levels fell in 55 (82%) of patients. The median PAQ-derived PA level decreased by 28% during lockdown, from 840.5 (944) METmin/week to 602 (1054) METmin/week during the lockdown (p = 0.01). A 53% increase was observed after the lockdown, to 924 (1214) METmin/week (p = 0.004). The CIED-derived activity level was 2.38 (1.3) hours/day pre-lockdown, 1.78 (1.1) hours/day during the lockdown (25% decrease, p < 0.001) and 2.69 (1.5) hours/day post-lockdown (51% increase, p < 0.001). Time spent on sedentary activities also increased to 9 (3) hours per day during the lockdown, up from 6.5 (4) hours before lockdown (p = 0.001).

Conclusions

All measures examined in this study indicate that the COVID-19 lockdown period was associated with a significant decrease in HFrEF patients’ PA. All efforts must be made on the part of clinicians and public health organizations to promote safe exercise in this subgroup of the population that is particularly vulnerable to the effects of a sedentary lifestyle.

The role of the novel MyAlgos e-medicine Platform in promoting patient-centered self-care management in patients with atrial fibrillation: The emPOWERD trial

Funding Acknowledgements

Type of funding sources: None.

Background

The emergence of digital health has revolutionized most aspects of healthcare. Meanwhile, atrial fibrillation (AF) remains the most common sustained arrhythmia associated with high morbidity and impaired quality of life. Patient-perceived treatment burden can be further optimized by digital health interventions utilizing smartphone technology. 

The MyAlgos platform is an integrated software system designed to enhance the remote management and communication between the patient and the healthcare practitioner. The mobile application encourages patient self-management through educational modules and tools to improve medication adherence. The web-based platform allows the health care practitioner to receive live updates on patient status and design personalized self-care management plans.

Purpose 

To investigate whether the use of the MyAlgos platform by AF patients is safe and improves the quality of self-care, quality of life (QoL), and hospitalization rate.

Methods

We designed a single-center, randomized, controlled, prospective, open-label, pilot study to compare the effect of the use of the full-feature MyAlgos platform version versus a stripped-down control version of the platform on the QoL, medication adherence and hospitalization rate in patients with paroxysmal AF.  The full version of the e-medicine platform includes active patient education, communication with the medical team, medication reminders as well as the full record of clinically significant data such as heart rate and blood pressure. Specialized algorithms monitor patient data and alert physicians for potential AF episodes. The control version only allows the recording of patient’s heart rate.

Results

A total of 80 patients with paroxysmal AF were randomized in a 1:1 ratio to receive either the full or the control version of the MyAlgos Platform. The mean age of all patients, 53 (66%) male, was 58.1 ± 9.1 years. Hypertension and diabetes were present in 47 (59%) and 7 (9%) respectively. At baseline, the majority of patients had AF-related symptoms classified as European Heart Rhythm Association (EHRA) I (45%) or EHRA II (24%), while the mean Atrial Fibrillation Effect on QualiTy-of-Life (AFEQT) score was 70.1 ± 17.0.  Between the two groups, there were no statistically significant differences in the baseline characteristics of the participants.

Conclusion

The emPOWERD trial will provide data on the impact of a novel e-medicine platform on the QoL, medication adherence and hospitalizations of patients with paroxysmal AF. We anticipate better outcomes for the subjects receiving the full version of the MyAlgos platform, allowing it to positively affect the further management of paroxysmal AF.

Abstract Figure. The MyAlgos e-medicine Platform

Three-dimensional volume-strain loops may reflect fibrosis in hypertrophic cardiomyopathy

Background

Combined plotting of deformation parameters against other indices [e.g. arterial pressure, left ventricular (LV) volume] might offer additional information about different diseases. Especially in hypertrophic cardiomyopathy (HCM) this approach might offer new insights into the various phenotypic and pathophysiologic features of this entity.

Purpose

Aim of this study was i) to apply strain-volume loops in HCM based on simultaneous frame-by-frame strain and volume changes' recordings acquired by means of three-dimensional (3D) speckle tracking imaging and ii) to investigate potential correlations between these loops and phenotypic features of HCM (including thickness, obstruction and fibrosis).

Methods

We included 40 HCM patients (54.1±14.3 years, 82.5% male, maximum wall thickness 19.3±4.8mm) who have consecutively undergone 3D-speckle tracking echocardiography and cardiovascular magnetic resonance (CMR) with late gadolinium enhancement (LGE). Values of 3D strain were plotted vs. volume for each frame to build a strain–volume loop. Peak of radial, longitudinal, and circumferential systolic strain (Rsp, Lsp, and Csp, respectively), systolic slopes of the loops (RsSl, LsSl, CsSl), and strain to end-diastolic volume (EDV) ratio (Rs/V, Ls/V, Cs/V) were computed for the analysis (panel A). Additionally, burden of fibrosis (percentage of LV mass) was defined by LGE extent (&gt;5 standard deviations compared to nulled myocardium) in CMR slices.

Results

All HCM patients had preserved EF (60.5±5,7%), while 16 (40%) had LV outflow tract obstruction (LVOTO&gt;30 mm Hg at rest). Mean LV mass index was 78.9±14.5 g (evaluated by 3D echocardiography). LGE was observed in 23 patients (57.5%) occupying 5.2±4.5% of LV mass. Concerning strain-volume loops the following values were recorded for radial (Rsp 30.8±9.8%, RsSl 0.4±0.13 and Rs/V 0.25±0.09), longitudinal (Lsp −9.4±3.7%, LsSl 0.12±0.06 and Ls/V 0.08±0.04) and circumferential deformation (Csp −14.2±3.5%, CsSl 0.18±0.05 and Cs/V 0.11±0.03). Among typical HCM characteristics tested (LV mass, LVOTO and LGE), only LV mass presented significant correlations with LsSl (r=−0.41, p&lt;0.01). Interestingly, HCM patients with smaller LVMI and without LGE presented steeper and narrower (difference between systolic and diastolic strain for the same volume) longitudinal strain-volume loops compared to patients with larger LVMIs and fibrosis (panel B).

Conclusions

Strain-volume loop is an innovative application of 3D deformation imaging in HCM. According to this new non-invasive method, increase of LVMI in HCM is accompanied by less longitudinal contribution to stroke volume, whereas better systolic-diastolic coupling may exclude the presence of underlying fibrosis.

Funding Acknowledgement

Type of funding source: None

219A machine learning classification algorithm to detect patients with paroxysmal atrial fibrillation during sinus rhythm

Background

Atrial fibrillation (AF) - the most common sustained cardiac arrhythmia - while not a life-threatening condition itself, leads to an increased risk of stroke and high rates of mortality. Early detection and diagnosis of AF is a critical issue for all health stakeholders.

Purpose

The aim of this study is to identify P-wave morphology patterns encountered in patients with Paroxysmal AF (PAF) and to develop a classifier discriminating PAF patients from healthy volunteers.

Methods

Three-dimensional 1000Hz ECG signals of 5 minutes duration were obtained through the use of a Galix GBI-3S Holter monitor from a total of 68 PAF patients and 52 healthy individuals. Signal pre-processing, consisting of denoising, QRS auto-detection, and ectopic beats removal was performed and a signal window of 250ms prior to the Q-wave (Pseg) was considered for every single beat. P‑wave morphology analysis based on the dynamic application of the k‑means clustering process was performed. For those Pseg that were assigned in the largest cluster, the mean P-wave was computed. The correlation of every P-wave with the mean P-wave of the main cluster was calculated. In case that it exceeded a prespecified threshold, the P-wave was allocated to the main morphology. For the remaining P‑waves, the same approach was followed once again, and the secondary morphology was extracted (picture). The P-waves of the dominant morphology were further analyzed using wavelet transform, whereas time-domain characteristics were also extracted.

A Support Vector Machine (SVM) model was created using the Gaussian Radial Basis Function kernel and the forward feature selection wrapper approach was followed. ECGs were allocated to the training, internal validation, and testing datasets in a 3:1:1 ratio.

Results

The percentage of P-waves following the main morphology in all three leads was lower in PAF patients (91.2 ±7.3%) than in healthy subjects (96.1 ±3.5%, p = 0.02). Classification between the two groups highlighted 7 features, while the SVM classifier resulted in a balanced accuracy of 91.4 ± 0.2% (sensitivity 94.2 ± 0.3%, specificity 88.6 ± 0.1%)

Conclusion

An Artificial Intelligence based ECG Classifier can efficiently identify PAF patients during normal sinus rhythm.

Abstract Figure.

244An automated beat exclusion algorithm to improve beat-to-beat P-wave morphology analysis

Background

A manually beat-to-beat P-wave analysis has previously revealed the existence of multiple P-wave morphologies in patients with paroxysmal Atrial Fibrillation (AF) while on sinus rhythm, distinguishing them from healthy, AF free patients.

Purpose

The aim of this study was to investigate the effectiveness of an Automated Beat Exclusion algorithm (ABE) that excludes noisy or ectopic beats, replacing manual beat evaluation during beat-to-beat P-wave analysis, by assessing its effect on inter-rater variability and reproducibility.

Methods

Beat-to-beat P-wave morphology analysis was performed on 34 ten-minute ECG recordings of patients with a history of AF. Each recording was analyzed independently by two clinical experts for a total of four analysis runs; once with ABE and once again with the manual exclusion of ineligible beats. The inter-rater variability and reproducibility of the analysis with and without ABE were assessed by comparing the agreement of analysis runs with respect to secondary morphology detection, primary morphology ECG template and the percentage of both, as these aspects have been previously used to discriminate PAF patients from controls.

Results

Comparing ABE to manual exclusion in detecting secondary P-wave morphologies displayed substantial (Cohen"s k = 0.69) to almost perfect (k = 0.82) agreement. Area difference among auto and manually calculated main morphology templates was in every case &lt;5% (p &lt; 0.01) and the correlation coefficient was &gt;0.99 (p &lt; 0.01). Finally, the percentages of beats classified to the primary or secondary morphology per recording by each analysis were strongly correlated, for both main and secondary P-wave morphologies, ranging from ρ=0.756 to ρ=0.940 (picture)

Conclusion

The use of the ABE algorithm does not diminish inter-rater variability and reproducibility of the analysis. The primary and secondary P-wave morphologies produced by all analyses were similar, both in terms of their template and their frequency. Based on the results of this study, the ABE algorithm incorporated in the beat-to-beat P-wave morphology analysis drastically reduces operator workload without influencing the quality of the analysis.

Abstract Figure.

P322Understanding the multiple P-wave morphologies in paroxysmal atrial fibrillation, during sinus rhythm, using computer simulation

Background

Atrial Fibrillation (AF) is the most common atrial arrhythmia. The initiation and perpetuation of AF are related to atrial remodeling affecting the electrical and structural atrial characteristics. The beat-to-beat analysis of the P-wave morphology (PWM), during sinus rhythm (SR), revealed the existence of a secondary PWM, while the proportion of the P-waves which follow the secondary morphology is higher in patients with a history of paroxysmal AF (pAF). This observation has led to the hypothesis that the multiple PWM may be the result of a transient shift in the stimulus origin, possibly within the broader anatomical region of the sinoatrial (SA) node, and it is the atrial electrical remodeling that contributes to more frequent P-waves following a secondary morphology in patients with pAF.

Purpose

To better understand the pathophysiology of AF there is a need to link different levels of analysis, in order to interpret macroscopic observations, through a surface electrocardiogram, with changes occurring at cell and tissue level. Towards this direction, computational modeling can be used as it is a non-invasive and reproducible method of analyzing the electrical activity of the heart.

Methods

The CRN atrial model was used, and a two-dimensional geometry of the atrial architecture was considered, including the major anatomical structures, like Crista Terminalis, Pectinate Muscles and Pulmonary Veins. Using existing knowledge, the CRN model was adapted to describe the ionic properties of the atrial structures as well as the electrical remodeling occurring under pAF conditions. Several scenarios were considered related to the extent of the electrical remodeled tissue and Heart Rate (HR) values. The stimulation protocol was designed as 5 stimuli originated at a specific point within the SA node area whereas the sixth stimulus originated either at the same location or 1 mm far from the previous one. The temporal variations of the atrial activation as a result of the transient shift of the sixth stimulus origin were computed.

Results

In electrically remodeled tissue, the displacement of the excitation site within the SA node resulted in a significant increase of the differences in atrial activation compared to healthy tissue, and the greater the spatial extent of the remodeling the greater the differences in the completion of the electrophysiological processes. In addition, increased HR or HR variability led to the increase of the differences especially when electrical remodeling coexists.

Conclusions

The observed differences in atrial substrate activation can explain the increased number of P-waves that match a secondary PWM in pAF patients during SR, while a future perspective is to use PWM as a marker to estimate the electrical remodeling extent in the atrial tissue. These results underline the need to link the macroscopic findings to the suspected microscopic electrical activity in order to better understand the pathophysiology of AF.