Validation of a machine learning algorithm to identify pulmonary vein isolation during ablation procedures for the treatment of atrial fibrillation: results of the PVISION study.

AIMS: Pulmonary vein isolation (PVI) is the cornerstone of ablation for atrial fibrillation. Confirmation of PVI can be challenging due to the presence of far-field electrograms (EGMs) and sometimes requires additional pacing manoeuvres or mapping. This prospective multicentre study assessed the agreement between a previously trained automated algorithm designed to determine vein isolation status with expert opinion in a real-world clinical setting. METHODS AND RESULTS: Consecutive patients scheduled for PVI were recruited at four centres. The ECGenius electrophysiology (EP) recording system (CathVision ApS, Copenhagen, Denmark) was connected in parallel with the existing system in the laboratory. Electrograms from a circular mapping catheter were annotated during sinus rhythm at baseline pre-ablation, time of isolation, and post-ablation. The ground truth for isolation status was based on operator opinion. The algorithm was applied to the collected PV signals off-line and compared with expert opinion. The primary endpoint was a sensitivity and specificity exceeding 80%. Overall, 498 EGMs (248 at baseline and 250 at PVI) with 5473 individual PV beats from 89 patients (32 females, 62 ± 12 years) were analysed. The algorithm performance reached an area under the curve (AUC) of 92% and met the primary study endpoint with a sensitivity and specificity of 86 and 87%, respectively (P = 0.005; P = 0.004). The algorithm had an accuracy rate of 87% in classifying the time of isolation. CONCLUSION: This study validated an automated algorithm using machine learning to assess the isolation status of pulmonary veins in patients undergoing PVI with different ablation modalities. The algorithm reached an AUC of 92%, with both sensitivity and specificity exceeding the primary study endpoints.

Quality of life and symptoms in patients selected for ablation of ventricular extrasystoles: a prospective study.

PURPOSE: Evaluation of the impact of catheter ablation for ventricular extrasystoles (VES) in structurally normal hearts on quality of life (QOL) and symptomatology. METHODS: Symptom analysis assessed with a disease-specific questionnaire, EHRA score for AF, and QOL analysis at baseline and 1 year after ablation. RESULTS: The study enrolled 39 patients between April 2016 and November 2019. Two patients were excluded from further analysis. At baseline, palpitations were reported in 31/37 (84%); syncope in 12/37 (32%); other cardiac symptoms in 33/37 (89%) of patients. The EHRA score was 3 or 4 in 13 patients (35%). With the modified arrhythmia-specific questionnaire (MASQ) psychological and physical scores were 46 and 39%. The overall perception of health in the SF-36 was 56 ± 16%. Ablation was performed in 35/37 (95%). At regular follow-up, symptoms were reported in 14/37 (38%) patients. ECG suggested a good procedural outcome in 65% with VES burden on Holter < 1% in 68%. At follow-up, palpitations were reported in 61% (P < 0.07); syncope in only 1 patient (P < 0.05). The EHRA score was 3 or 4 in only one patient (P < 0.05). MASQ scores improved to 62 and 60% (both p < 0.001). The overall perception of health in the SF-36 became 64 ± 17% (P < 0.02). CONCLUSIONS: Patients with VES suffer from a wide variety of symptoms and have a low quality of life, as demonstrated by the EHRA score and conventional questionnaires. After catheter ablation, palpitations are still reported, but become less frequently present. Syncope becomes rare. Quality of life improves significantly from all perspectives.

Clinical validation of a 13-lead electrocardiogram derived from a self-applicable 3-lead recording for diagnosis of myocardial supply ischaemia and common non-ischaemic electrocardiogram abnormalities at rest.

Aims: In this study, we compare the diagnostic accuracy of a standard 12-lead electrocardiogram (ECG) with a novel 13-lead ECG derived from a self-applicable 3-lead ECG recorded with the right exploratory left foot (RELF) device. The 13th lead is a novel age and sex orthonormalized computed ST (ASO-ST) lead to increase the sensitivity for detecting ischaemia during acute coronary artery occlusion. Methods and results: A database of simultaneously recorded 12-lead ECGs and RELF recordings from 110 patients undergoing coronary angioplasty and 30 healthy subjects was used. Five cardiologists scored the learning data set and five other cardiologists scored the validation data set. In addition, the presence of non-ischaemic ECG abnormalities was compared. The accuracy for detection of myocardial supply ischaemia with the derived 12 leads was comparable with that of the standard 12-lead ECG (P = 0.126). By adding the ASO-ST lead, the accuracy increased to 77.4% [95% confidence interval (CI): 72.4-82.3; P < 0.001], which was attributed to a higher sensitivity of 81.9% (95% CI: 74.8-89.1) for the RELF 13-lead ECG compared with a sensitivity of 76.8% (95% CI: 71.9-81.7; P < 0.001) for the 12-lead ECG. There was no significant difference in the diagnosis of non-ischaemic ECG abnormalities, except for Q-waves that were more frequently detected on the standard ECG compared with the derived ECG (25.9 vs. 13.8%; P < 0.001). Conclusion: A self-applicable and easy-to-use 3-lead RELF device can compute a 12-lead ECG plus an ischaemia-specific 13th lead that is, compared with the standard 12-lead ECG, more accurate for the visual diagnosis of myocardial supply ischaemia by cardiologists.

Congenital left ventricular diverticulum: A rare cause of cardiac arrhythmia.

Congenital left ventricular diverticula are rare cardiac malformations that usually remain asymptomatic. However, life-threatening complications as ventricular arrhythmias, systemic embolism, spontaneous rupture and development of valvular regurgitation, are described. Diagnosis is based on excluding coronary artery disease, traumatic or inflammatory causes, and other underlying cardiomyopathies. Treatment is directed towards the potential complications, yielding mainly therapy of ventricular arrhythmia. Surgical resection is required for larger-sized congenital aneurysms with adverse hemodynamic effects. We present two cases of a left ventricular diverticulum causing cardiac arrhythmia which led to further surgical treatment.

Different dynamics of new-onset electrocardiographic changes after balloon- and self-expandable transcatheter aortic valve replacement: Implications for prolonged heart rhythm monitoring.

BACKGROUND: New onset electrocardiographic (ECG) changes after transcatheter aortic valve replacement (TAVR) are used to assess the risk for late atrioventricular block. However, the time of ECG evaluation remains controversial. We aimed to compare the time course and dynamics of new onset ECG changes according to valve design in balloon- (BEV) and self-expandable (SEV) TAVR. METHODS AND RESULTS: This single center study enrolled 133 consecutive TAVR patients (28.6% SEV, 71.4% BEV). Patients with pre-existent permanent pacemaker implant (PPMI), procedural death or incomplete ECG registration were excluded. Standard 12­lead ECG was performed before the procedure, at 1, 24, 48 and 120 h and 1 month. In BEV patients, no significant PR prolongation occurred, whereas in SEV patients the PR interval prolonged significantly with 33.7 ± 22.0 ms (p < 0.001, compared to pre-TAVR) but only after 48 h after TAVR. Widening of QRS duration was comparable among both BEV and SEV patients (6.7 ± 21.5 versus 17.0 ± 26.9 ms, p = 0.061) and occurred immediately after TAVR. New-onset left bundle branch block was seen in 18.5% of BEV and 30.8% of SEV patients (p = 0.120) and occurred within 24 h after TAVR in both groups. Late PPMI (>24 h after TAVR) was higher in SEV compared to BEV patients (15.3% versus 1.5%, p = 0.008). CONCLUSION: Self-expandable valves cause more impairment in atrioventricular conduction with a delayed time course compared to balloon expandable valves. This might explain the higher pacemaker need beyond 24 h after TAVR. Our findings suggest that patients with self-expandable valves require at least 48 h ECG monitoring post TAVR.

Therapy From a Novel Substernal Lead: The ASD2 Study.

OBJECTIVES: The ASD2 (Acute Extravascular Defibrillation, Pacing, and Electrogram) study evaluated the ability to adequately sense, pace, and defibrillate patients with a novel implantable cardioverter-defibrillator (ICD) lead implanted in the substernal space. BACKGROUND: Subcutaneous ICDs are an alternative to a transvenous defibrillator system when transvenous implantation is not possible or desired. An alternative extravascular system placing a lead under the sternum has the potential to reduce defibrillation energy and the ability to deliver pacing therapies. METHODS: An investigational lead was inserted into the substernal space via a minimally invasive subxiphoid access, and a cutaneous defibrillation patch or subcutaneous active can emulator was placed on the left mid-axillary line. Pacing thresholds and extracardiac stimulation were evaluated. Up to 2 episodes of ventricular fibrillation were induced to test defibrillation efficacy. RESULTS: The substernal lead was implanted in 79 patients, with a median implantation time of 12.0 ± 9.0 min. Ventricular pacing was successful in at least 1 vector in 76 of 78 patients (97.4%), and 72 of 78 (92.3%) patients had capture in ≥1 vector with no extracardiac stimulation. A 30-J shock successfully terminated 104 of 128 episodes (81.3%) of ventricular fibrillation in 69 patients. There were 7 adverse events in 6 patients causally (n = 5) or possibly (n = 2) related to the ASD2 procedure. CONCLUSIONS: The ASD2 study demonstrated the ability to pace, sense, and defibrillate using a lead designed specifically for the substernal space.

Failure to detect life-threatening arrhythmias in ICDs using single-chamber detection criteria.

BACKGROUND: There are anecdotal reports of sudden death despite a functional implantable cardioverter defibrillator (ICD). We sought to describe scenarios leading to fatal or near-fatal outcome due to inappropriately inhibited ICD therapy in devices programmed with single-chamber detection criteria. METHODS: Programmed settings, episode lists, and intracardiac electrograms from 24 patients with a life-threatening event (n = 12) or fatal outcome (n = 12) related to failed ventricular arrhythmia detection were used to clarify the underlying scenario. RESULTS: Fifty episodes of failed ventricular arrhythmia detection were identified and categorized into six scenarios: (1) spontaneous ventricular tachycardia (VT) or ventricular fibrillation (VF) with a rate below the detection limits, (2) misclassification of polymorphic VT (PVT) or VF as supraventricular tachycardia (SVT), (3) misclassification of VT/VF as cluster of nonsustained VT episodes, (4) misclassification of monomorphic VT (MVT) as SVT, (5) inappropriate shock abortion, and (6) false termination detection. These scenarios occurred respectively 6, 9, 3, 9, 8, and 15 times. In 9/9 (100%) patients with PVT/VF classified as SVT, rate stability was active for rates ranging from 222 to 250 beats/min. MVT detected as SVT was due to the sudden onset criterion in 7/9 (78%) patients and twice a consequence of the rate stability criterion active for rates ranging from 200 to 250 beats/min. CONCLUSION: We describe six scenarios leading to failure of ventricular arrhythmia detection in a single-chamber detection setting withholding life-saving therapy. These scenarios are more likely to occur with high-rate programming and long detection times, especially if combined with rate stability and sudden onset.

Clinical assessment and comparison of annotation algorithms in high-density mapping of regular atrial tachycardias.

BACKGROUND: High-density automated mapping of regular atrial tachycardias (ATs) requires accurate assessment of local activation times (LATs). OBJECTIVE: To evaluate high-density mapping of ATs and compare the accuracy of different automated LAT annotation algorithms. METHODS: Fifteen patients underwent AT ablation guided by the automated ConfiDENSEۛ high-density mapping module (Carto 3 v4) allowing manual reannotation (edited maps). For each AT, unedited automated maps were reconstructed offline by three algorithms: maximum unipolar slope (LATSlope ), bipolar peak (LATPeak ), and a new hybrid annotation algorithm (LATHybrid ). Five blinded experts were asked to define the (1) tachycardia mechanism, (2) ablation target, and (3) level of difficulty of these unedited maps. RESULTS: Twenty-one ATs (cycle length 300 ± 46 ms, activation points 955 ± 421) were successfully ablated using LATHybrid guided ablation with manual editing in a small number of points. At 6 months, 14 (93%) of the patients were free of AT recurrences. Unedited LATHybrid maps showed the highest accuracy in defining the tachycardia mechanism (LATHybrid : 49% vs. LATPeak : 27% vs. LATSlope : 28%, P < 0.001) and ablation target (LATHybrid : 65% vs. LATPeak : 39% vs. LATSlope : 31%, P < 0.001). Overall, LATHybrid -annotated maps were graded as "easier to interpret" by the experts (difficulty score 2.3 ± 0.9) versus LATPeak (2.8 ± 1) and LATSlope (3.2 ± 0.8) (P < 0.001). Only 12% of the LATHybrid maps were annotated as uninterpretable compared to 31% of LATSlope and 45% of the LATPeak maps (P < 0.001). CONCLUSION: Automated LATHybrid annotation allows better and easier recognition of the tachycardia mechanism compared to automated LATPeak and LATSlope algorithms, although fully automated mapping still requires further improvements.

Automated verification of pulmonary vein isolation in radiofrequency- and cryoballoon-guided ablation.

BACKGROUND: Verification of pulmonary vein isolation (PVI) can be challenging due to the coexistence of pulmonary vein potentials and far-field potentials. This study aimed to prospectively validate a novel algorithm for automated verification of PVI in radiofrequency (RF)-guided and cryoballoon (CB)-guided ablation strategies. METHODS: A data set of 620 (RF: 516 EGMs and CB: 104 EGMs) bipolar electrograms (EGM), recorded by circular mapping catheter placed at the left atrium-pulmonary vein (PV) junction, were prospectively analyzed by a two-step algorithm. The algorithm differentiates isolated from nonisolated EGMs based on typology and specific parameters of the bipolar EGMs. EGMs were recorded at baseline and after proven isolation in RF- and CB-guided procedures. Additionally, in the RF group, EGMs during encircling of the PVs were analyzed. RESULTS: In the RF and CB group, the algorithm correctly identifies EGMs as isolated or nonisolated with respectively 93% and 96% sensitivity and 86% and 90% specificity. In the RF subgroups of (1) baseline and proven isolated EGMs, (2) EGMs during encircling, and (3) EGMs in redo procedures sensitivity was 96%, 88%, and 100%, respectively, with specificity of 81%, 91%, and 100%. Fourteen out of 14 (100%) reconnected PVs were correctly identified as containing PVPs. Eleven out of 12 (92%) failed freeze attempts were correctly identified as being nonisolated. CONCLUSION: We validated a two-step algorithm for automated PVI verification, applicable both for RF- and CB-guided PVI. The algorithm automatically differentiates isolated from nonisolated PVs with high accuracy and without the need for pacing maneuvers.

Evaluating current implantable cardioverter defibrillator implantation procedures: can common complications be minimised?

The implantable cardioverter-defibrillator (ICD) is the cornerstone of treatment and prevention of malignant ventricular arrhythmias. Despite 30 years of experience, implantation of ICDs carries a risk of complications both during the procedure and long-term follow-up. Operator and procedure related factors may contribute to this risk. Furthermore, access, pocket, device and lead related problems occur, on top of problems related to arrhythmias and the patient themselves. Infection is the most feared complication, and its incidence seems to rise. Factors leading to complications are assessed, as well as measures to reduce these complications, including antibiotics and subcutaneous devices. Four patient categories with an increased risk are identified: the elderly with atrial fibrillation, diabetes or renal failure; the pediatric patient with or without congenital heart disease, the young patient with specific inherited diseases, and all those who undergo replacement, upgrade or concomitant lead extraction.

Different Methods to Measure QRS Duration in CRT Patients: Impact on the Predictive Value of QRS Duration Parameters.

BACKGROUND: Measurements of QRS duration (QRSD) in patients undergoing cardiac resynchronization therapy (CRT) are not standardized. We hypothesized that both the measurement of QRSD and its predictive value on CRT response are sensitive to the method by which QRSD is measured. METHODS: Electrocardiograms (ECGs) pre- and post-CRT from 52 CRT patients (66 ± 12 years, 65% male) were retrospectively analyzed. Custom-made software was developed to measure global QRSD (QRSDglobal ) and lead-specific QRSD (QRSDI,II,III,aVR,aVL,aVF,V1,V2,V3,V4,V5,V6 ). QRSD was also assessed automatic by a routinely used ECG device. For each method we measured QRSD pre- and post-CRT and shortening of QRSD (∆QRSD). Response to CRT at 6 months was defined as an improvement of ≥1 class in New York Heart Association classification and an increase by >7.5% in left ventricular ejection fraction. RESULTS: The CRT response rate was 77% (n = 40). Different methods to measure QRSD show divergent nominal values before (median range 152-172 ms, P < 0.001) and after CRT (130-152 ms, P < 0.001). The predictive value of QRSD measurements for CRT response also varies significantly according to the method used (range AUC pre-CRT QRSD 0.400-0.580, P < 0.05; AUC post-CRT QRSD 0.447-0.768, P < 0.05; AUC ΔQRSD 0.540-0.858, P < 0.05). Global QRSD measurements revealed lower variability compared to lead-specific QRSD. CONCLUSION: Different methods to measure QRSD yield not only different nominal values but also influence the value of QRSD in predicting CRT response. Measuring QRSD by a global method can help to standardize QRSD measurements in future studies.

Variability in interpretation of the electrocardiogram in young athletes: an unrecognized obstacle for electrocardiogram-based screening protocols.

AIMS: To assess in young athletes (i) the variability in the percentage of abnormal electrocardiograms (ECGs) using different criteria and (ii) the variability in ECG interpretation among cardiologists and sport physicians. METHODS AND RESULTS: Electrocardiograms of 138 athletes were categorized by seven cardiologists according to the original European Society of Cardiology (ESC) criteria by Corrado (C), subsequently modified by Uberoi (U), Marek (M), and the Seattle criteria (S); seven sports physicians only used S criteria. The percentage of abnormal ECGs for each physician was calculated and the percentage of complete agreement was assessed. For cardiologists, the median percentage of abnormal ECGs was 14% [interquartile range (IQR) 12.5-20%] for C, 11% (IQR 9.5-12.5%) for U [not significant (NS) compared with C], 11% (IQR 10-13%) for M (NS compared with C), and 7% (IQR 5-8%) for S (P < 0.005 compared with C); complete agreement in interpretation was 64.5% for C, 76% for U (P < 0.05 compared with C), 74% for M (NS compared with C), and 84% for S (P < 0.0005 compared with C). Sport physicians classified a median of 7% (IQR 7-11%) of ECGs as abnormal by S (P = NS compared with cardiologists using S); complete agreement was 72% (P < 0.05 compared with cardiologists using S). CONCLUSION: Seattle criteria reduced the number of abnormal ECGs in athletes and increased agreement in classification. However, variability in ECG interpretation by cardiologists and sport physicians remains high and is a limitation for ECG-based screening programs.

Atrioventricular block precipitated by isoproterenol.

An isoproterenol infusion was administered during an electrophysiologic study (EPS) in a patient with a history of near syncope, left bundle branch block, and no documented atrioventricular (AV) block. Isoproterenol precipitated classic 2:1 Infra-Hisian AV block most probably proximal to the site of recording a His-Purkinje potential consistent with right bundle branch activity. Paroxysmal AV block also occurred during isoproterenol washout at a different site located distal to the presumed right bundle branch potential. Isoproterenol may be valuable diagnostically in an occasional patient suspected of AV block in whom an EPS is unrevealing and a drug challenge is negative.

Undersensing by an ICD due to alternans of the ventricular electrogram.

Alternans of the ventricular electrogram (VEGM) during ventricular tachycardia (VT) is a rare cause of ventricular undersensing by an implantable cardioverter-defibrillator (ICD). This report describes a patient with a St. Jude ICD who exhibited sustained monomorphic VT associated with surface QRS alternans, alternating cycle lengths, alternans of the VEGM causing intermittent undersensing of the smaller component, and intermittent 2:1 counting of ventricular intervals during 1:1 sensing in response to the ICD detection algorithm. VEGM undersensing was corrected noninvasively simply by programming the threshold start from 62.5% to 50% which increased the sensitivity based on the amplitude of the VEGM. This maneuver did not affect the satisfactory and stable defibrillation threshold.

Functional atrial undersensing associated with switching to a tracking mode of pacing.

We have previously demonstrated that contemporary St. Jude devices (pacemakers and implantable cardioverter-defibrillators [ICDs]; St. Jude Medical, Sylmar, CA, USA) are designed to generate an extended postventricular atrial refractory period (PVARP) of 475 ms at the termination of conventional automatic mode switching (AMS) in response to atrial tachyarrhythmias . This response may cause functional atrial undersensing . A similar PVARP response unrelated to conventional AMS was found in four St. Jude devices (three ICDs and one pacemaker) whenever a nontracking pacing mode switched to a tracking DDD(R) mode. PVARP extension and functional atrial undersensing were observed when the VOO, VVI, and the DDI(R) modes (unrelated to conventional AMS) switched to the DDD(R) mode . In one patient the switch from the OOO mode (in the programmed noise reversion mode) to the DDD mode occurred after cessation of electromagnetic interference disturbing the ventricular channel. In this case PVARP extension was seen only in the corresponding markers because no P waves occurred coincidentally with the extended PVARP. The PVARP extension caused by a mode switch to the tracking function was designed to prevent sensing of a retrograde P wave on the first cycle of the reestablished tracking mode. The observed functional atrial undersensing is a normal manifestation of device function and must not be misinterpreted as a true atrial undersensing problem.