Cracks in structural steel were retarded or even stopped when fatigued in aerated seawater environments at 10 Hz. Backface strain measurements proved that the cause was corrosion product wedging, which enhances the effect of crack closure. The wedge thickness depended on the oxygen supply inside the crack. This is enhanced by acration and solution pumping, which was more effective at higher frequencies.

Funding Acknowledgements Type of funding sources: None. Background Untreated obstructive sleep apnoea (OSA) contributes to progression of atrial fibrillation (AF) and reduces the success rate of heart rhythm control strategies. OSA remains one of the most frequently underdiagnosed modifiable risk factors in AF patients due to a lack of standardized screening methods and low awareness. Purpose To assess the impact of implementation of a structured remote OSA screening and management pathway on the prevalence of OSA in AF patients scheduled for AF ablation procedures. Methods In October 2020, a novel remote OSA screening and management pathway (VIRTUAL-SAFARI) was introduced in two AF outpatient clinics in the Netherlands. Consecutive patients scheduled for AF ablation were offered OSA screening consisting of sending a portable home sleep test to patients’ homes to perform a remote sleep recording for one night, analysis by a sleep physician, discussion of results with the patient, and initiation of treatment (when applicable). The impact of this structural screening strategy was assessed by comparing the prevalence of concomitant OSA (defined as apnoea-hypopnoea index ≥5) for patients scheduled for AF ablation in the year before and after introduction of the OSA management pathway. Results A total of 733 patients was studied, 308 in the year before (Oct ’19 - Sep ’20) and 425 in the year after (Oct ’20 - Sep ’21) introduction of the VIRTUAL-SAFARI pathway. Median age was 65 [58-71], 64% was male and median body mass index (BMI) was 27 [25-30] kg/m2. Baseline characteristics were comparable for the groups before and after introduction of the pathway (Table 1). In the cohort before pathway introduction, OSA had been diagnosed in 26 patients (8%, Figure 1) and was treated with positive airway pressure in 10 cases (3%). In the cohort after pathway introduction, OSA had previously been diagnosed in 53 patients (12%). Eighty-eight percent of patients without previous OSA screening was referred via the remote pathway. Results of the sleep recordings were available for 213 (59%) at the time of this analysis. Previously unknown OSA was diagnosed in 184 patients (86% of available recordings), increasing the prevalence of confirmed OSA to 237 (55%). For 22% of patients, results of sleep recordings are pending. Absence of OSA was confirmed in 9%, and 13% of patients had not been screened (e.g. because of patient preference or logistical reasons). After pathway introduction, 82 patients (19%) were treated or received advice to start treatment with positive airway pressure. Treatment decisions are pending for 9% of the cohort. Conclusion After the implementation of structured remote OSA screening in a well characterized cohort of consecutive patients scheduled for AF ablation, the prevalence of diagnosed OSA increased from 8% to 55%. Whether appropriate risk factor management, including treatment of OSA identified by structured screening, will improve AF outcomes needs to be tested in future studies.

Funding Acknowledgements Type of funding sources: None. Background TeleCheck-AF is a mobile health (mHealth) infrastructure developed to provide remote management and comprehensive care to patients with atrial fibrillation (AF) during the Covid disease-19 pandemic lockdown within cardiology centers in Europe. TeleCheck-AF integrates an on-demand photoplethysmography-based heart rate/rhythm monitoring application supported a scheduled teleconsultation. Purpose The current sub-study of the TeleCheck-AF project aimed to provide the first real-world dataset on patient adherence and motivation to a standardized mHealth application integrated in remote AF management. Methods Patients were instructed to perform 60-second app-based heart rate/rhythm recordings three times daily and in case of symptoms for seven consecutive days prior to teleconsultation. Motivation was defined as number of days in which the expected number of measurements (≥three/day) were performed per number of days over the entire prescription period. Adherence was defined as number of performed measurements per number of expected measurements over the entire prescription period. Results Data from 990 consecutive patients with diagnosed AF (median age 64 [57-71] years, 39% female) from 10 centers that included the highest number of patients (≥25) were analyzed. Patients with both optimal motivation (100%) and adherence (≥100%) constituted 28% of the study population and had a lower percentage of recordings in sinus rhythm (90 [53-100%] vs 100 [64-100%], P<0.001) compared to others. Age and diabetes were predictors of both optimal motivation and adherence (odds ratio [OR] 1.02, 95% coincidence interval [95% CI] 1.01-1.04, P<0.001 and OR, 0.49, 95% CI 0.28-0.86, P=0.013, respectively). Patients with 100% motivation also had ≥100% adherence. Independent predictors for optimal adherence alone were age (OR 1.02, 95% CI 1.00-1.04, P=0.014), female sex (OR 1.70, 95% CI 1.29-2.23, P<0.001), previous AF ablation (OR 1.35, 95%CI 1.03-1.07, P=0.028). Conclusion In the TeleCheck-AF project, older age and diabetes were predictors of optimal patient motivation and adherence to app-based heart rate/rhythm monitoring. Therefore, physicians, nurses and allied health specialists involved in the management and care for patients with AF should not be discouraged to provide a mHealth infrastructure to elderly patients. Patient engagement improves mHealth adherence/motivation, hence, it is crucial to tailor the mHelath intervention to the needs and preferences of the patient.

Funding Acknowledgements Type of funding sources: None. Purpose Sleep-disordered breathing (SDB) is prevalent in up to 50% of patients undergoing atrial fibrillation (AF) ablation. Currently, it remains unclear whether all AF patients should be systematically screened for SDB, or whether pre-selection of patients requiring screening can be improved. We aimed 1) to assess the accuracy of the STOP-Bang screening questionnaire as a tool for detecting SDB in patients scheduled for AF ablation; and 2) to develop a refined, AF-specific version of the STOP-Bang to improve pre-selection. Methods Consecutive patients scheduled for AF ablation without a previous history of SDB and/or SDB screening were included. Patients were digitally referred to the previously described Virtual-SAFARI SDB screening and management pathway1 including a home sleep test using polygraphy. An apnoea-hypopnoea-index (AHI) of ≥15 was interpreted as moderate-to-severe SDB. The accuracy of the STOP-Bang questionnaire (Snoring, Tiredness, Observed apneas, blood Pressure, BMI ≥35 kg/m², Age, Neck circumference, and Gender) was evaluated. Logistic regression was used to assess characteristics within and outside the STOP-Bang questionnaire associated with moderate-to-severe SDB. These characteristics were used to refine the STOP-Bang specifically for AF patients. Results Of 206 included patients, 51% was diagnosed with moderate-to-severe SDB. The STOP-Bang questionnaire performed poorly in detecting SDB, with an area under the receiver operating characteristic curve (AUROC) of 0.647 (0.573-0.721). AF-specific refinement of the STOP-BANG resulted in the BOSS-GAP score. Therein, tiredness and neck circumference were removed, while body mass index with cut-off point ≥27 kg/m² and previous stroke or transient ischaemic attack were added. The BOSS-GAP questionnaire performed better with an AUROC of 0.738 (0.672-0.805) in the overall population. Conclusion The STOP-Bang questionnaire showed limited value when used as a pre-selection tool for SDB screening. The refined, AF-specific BOSS-GAP questionnaire demonstrated slightly improved, but still limited accuracy in identifying AF patients with SDB. Whether questionnaires bring an advantage in pre-selection for SDB screening compared to structural screening in patients with AF, requires further study.

Funding Acknowledgements Type of funding sources: None. Background In patients with atrial fibrillation (AF), expiratory airflow limitation adds to overall morbidity and may impair the response to heart rhythm control strategies. Purpose We aimed to determine the prevalence of expiratory airflow limitation in patients scheduled for AF ablation and evaluated whether routine preprocedural cardiac analyses can detect occult lung disease. Methods Consecutive AF patients scheduled for catheter ablation were systematically screened for expiratory airflow limitation with handheld (micro)spirometry devices. As part of routine preprocedural care, patients underwent cardiac computed tomographic angiography (cCTA), transthoracic echocardiography and respiratory polygraphy. Qualitative analyses of cCT was performed for emphysema, airway abnormalities and lymphadenopathy. Sleep apnea severity and nocturnal desaturation were derived from polygraphy. Multivariate logistic regression was performed to assess if routinely preprocedural studies were associated with expiratory airflow limitation. Results (Micro)spirometry was performed in 110 consecutive patients and expiratory airflow limitation was detected in 25% of patients (previously unknown in 24 of 28 patients; Figure 1). Patients with expiratory airflow limitation more often presented with pulmonary abnormalities on cCTA, such as mild-to-severe emphysema (odds ratio [OR] 4.2, 95% confidence interval [CI] 1.12-15.1, p < 0.05), lymphadenopathy (OR 3.6, 95% CI 1.1-11.3, p < 0.05) and bronchial wall thickening (OR 2.6, 95% CI 1.0-6.5, p < 0.05; Figure 2). The negative predictive value of the absence of pulmonary abnormalities on cCTA to identify patients with normal lung function was 85%. Polygraphy-derived sleep apnea status and nocturnal desaturation was less severe in patients with expiratory airflow limitation compared to patients with normal lung function (32% vs 48% moderate-to-severe sleep apnea, p = 0.23; oxygen desaturation index 3.0 [2.4-6.5] vs. 6.7 [3.4-11.4], p = 0.03). Echocardiography data did not differ between patients with compared to patients without expiratory airflow limitation. Conclusions Spirometry detected expiratory airflow limitation in 25% of patients scheduled for AF ablation. Routine preprocedural cCTA includes pulmonary features which may help in triage referral for formal pulmonary assessment.