Accuracy of a Single-Lead ECG Device for Diagnosis of Cardiac Arrhythmias Compared Against Cardiac Electrophysiology Study.

BACKGROUND: Single-lead electrocardiogram (ECG) devices may allow detection and diagnosis of cardiac rhythms. However, data on their accuracy for detecting cardiac arrhythmias beyond atrial fibrillation are limited. We aimed to determine the accuracy of the AliveCor KardiaMobile (AC) (AliveCor Inc, Mountain View, CA, USA) for the diagnosis of arrhythmias against gold standard cardiac electrophysiology study (EPS). METHOD: Patients undergoing clinically indicated EPS underwent simultaneous rhythm recording with an AC, standard 12-lead ECG, and EP catheters for intracardiac electrograms. Rhythms recorded during EPS were classified based on electrogram, 12-lead ECG, and clinical findings. Blinded reviewers provided differential diagnoses for the single-lead AC tracings; a separate reviewer compared diagnoses made between the AC tracings and EPS findings. RESULTS: In 49 patients, 843 cardiac rhythms were captured during 502 AC recordings. Analysis of tracings containing sinus rhythm (n=273) returned an overall accuracy of 92%, with sensitivity and specificity values of 93% and 92%, respectively. Accuracy for tracings per rhythm was atrial fibrillation 91% (n=51); supraventricular tachycardia accuracy was 89% (n=191), ventricular tachycardia 91% (n=198), ventricular fibrillation 98% (n=11), and asystole 100% (n=5). Accuracy for supraventricular ectopy was 93% (n=28) and for premature ventricular complexes was 91% (n=86). Overall accuracy was 94% for solitary rhythms and 93% in tracings from patients with baseline bundle branch block. CONCLUSIONS: When compared against the gold standard EPS diagnosis, the interpretation of arrhythmias recorded by an AliveCor single-lead ECG device had reasonable diagnostic accuracy.

Predicting factors for omitting beta-blockers in patients with tachycardia-induced cardiomyopathy after successful catheter ablation for atrial fibrillation.

Tachycardia induces a reduction in the left ventricular ejection fraction (LVEF), which is defined as tachycardia-induced cardiomyopathy (TIC). Conversion to and maintenance of sinus rhythm by catheter ablation can improve LVEF in patients with TIC due to atrial fibrillation (AF). Beta-blockers are mandatory for the treatment of heart failure with reduced LVEF(HFrEF), but the necessity of beta-blockers in TIC patients even after catheter ablation remains unclear. We examined the effect of beta-blockers on cardiac function in TIC patients after catheter ablation. We retrospectively analyzed 124 patients with a history of heart failure and an LVEF of ≤ 50% who underwent catheter ablation for AF. TIC was defined as a ≥ 10% improvement in the baseline LVEF and an improvement to an LVEF of ≥ 50% at 6 months after ablation. Patients with other cardiomyopathy diagnosed before the ablation were excluded. LVEF was significantly increased with the reductions of the left ventricular and left atrial volumes at the 6-month follow-up in all 80 patients with TIC. No beta-blockers were prescribed during the post-ablation follow-up in 21 patients with TIC. The absolute values of and changes in the echocardiographic parameters between before and after ablation were not significantly different between patients with and without beta-blockers after the ablation. A simple score using the history of hospitalization for heart failure and use of beta-blockers or diuretics prior to ablation was useful in identifying TIC patients who did not need prescription of beta-blockers after catheter ablation. LVEF similarly improved in both patients with and without prescription of beta-blockers after the ablation. Beta-blockers may not need to be prescribed after successful catheter ablation for AF in LVEF of ≤ 50% patients without other cause of cardiomyopathy diagnosed before the ablation, a history of hospitalization for heart failure and prescription of beta-blockers and diuretics before the ablation.

Predictor of A4 amplitude using preprocedural electrocardiography in patients with leadless pacemakers.

BACKGROUND: Based on historical studies of leadless pacemakers (LPs), high atrioventricular synchrony (AVS) with mechanical sensing-based VDD pacing is largely influenced by A4 amplitude. A limited study investigated the predictors of A4 amplitude using clinical and echocardiographic parameters. OBJECTIVE: The purpose of this study was to investigate the predictors of A4 amplitude preoperatively to select patients who could benefit the most from AVS among patients with VDD LPs (Micra-AV, Medtronic). METHODS: Data from patients who received Micra-AV implantations from November 2021 to August 2023 at Tottori University Hospital were analyzed. Twelve-lead electrocardiography and transthoracic echocardiography were performed before the Micra-AV implantations. To assess the electrical indices associated with the A4 signal, electrocardiographic morphologic P-wave parameters were analyzed, including P-wave duration, P-wave amplitude, maximum deflection index (MDI), and P-wave dispersion. RESULTS: A total of 50 patients who underwent Micra-AV implantations (median age 84 years; 64% male) were included and divided into 2 groups based on the median value of A4 amplitude, the high-A4 group (A4 amplitude >2.5 m/s2; n = 26), and low-A4 group (A4 amplitude ≤2.5 m/s2; n = 24). There was a significant difference between the high-A4 and low-A4 groups with regard to left ventricular ejection fraction (P = .01), P-wave dispersion (P = .01), and MDI (P <.001). Multivariate logistic analysis revealed that lower MDI was an independent predictor of high A4-amplitude (odds ratio 0.78; 95% confidence interval 0.67-0.92; P = 0.003). CONCLUSION: Preoperative electrocardiographic evaluations of P-wave morphology may be useful for predicting A4 amplitude. MDI was the only independent A4 amplitude predictor that seemed promising for selecting Micra-AV patients.

Mortality after catheter ablation of structural heart disease related ventricular tachycardia.

BACKGROUND: There is a paucity of data describing mortality after catheter ablation of ventricular tachycardia (VT). OBJECTIVES: We describe the causes and predictors of cardiac transplant and/or mortality following catheter ablation of structural heart disease (SHD) related VT. METHODS: Over 10-years, 175 SHD patients underwent VT ablation. Clinical characteristics, and outcomes, were compared between patients undergoing transplant and/or dying and those surviving. RESULTS: During 2.8 (IQR 1.9-5.0) years follow-up, 37/175 (21%) patients underwent transplant and/or died following VT ablation. Prior to ablation, these patients were older (70.3 ± 11.1 vs. 62.1 ± 13.9 years, P = 0.001), had lower left ventricular ejection fraction ([LVEF] 30 ± 12% vs. 44 ± 14%, P < 0.001), and were more likely to have failed amiodarone (57% vs. 39%, P = 0.050), compared to those that survived. Predictors of transplant and/or mortality included LVEF≤35% (HR 4.71 [95% CI 2.18-10.18], P < 0.001), age ≥ 65 years (HR 2.18 [95% CI 1.01-4.73], P = 0.047), renal impairment (HR 3.73 [95% CI 1.80-7.74], P < 0.001), amiodarone failure (HR 2.67 [95% CI 1.27-5.63], P = 0.010) and malignancy (HR 3.09 [95% CI 1.03-9.26], P = 0.043). Ventricular arrhythmia free survival at 6-months was lower in the transplant and/or deceased, compared to non-deceased group (62% vs. 78%, P = 0.010), but was not independently associated with transplant and/or mortality. The risk score, MORTALITIES-VA, accurately predicted transplant and/or mortality (AUC: 0.872 [95% CI 0.810-0.934]). CONCLUSIONS: Cardiac transplant and/or mortality after VT ablation occurred in 21% of patients. Independent predictors included LVEF≤35%, age ≥ 65 years, renal impairment, malignancy, and amiodarone failure. The MORTALITIES-VA score may identify patients at high-risk of transplant and/or dying after VT ablation.

Delivery of Cardioactive Therapeutics in a Porcine Myocardial Infarction Model.

Myocardial infarction is one of the leading causes of death and disability worldwide, and there is an urgent need for novel cardioprotective or regenerative strategies. An essential component of drug development is determining how a novel therapeutic is to be administered. Physiologically relevant large animal models are of critical importance in assessing the feasibility and efficacy of various therapeutic delivery strategies. Due to their similarities to humans in cardiovascular physiology, coronary vascular anatomy, and heart weight to body weight ratio, swine is one of the preferred species in the preclinical evaluation of new therapies for myocardial infarction. The present protocol describes three methods of administering cardioactive therapeutic agents in a porcine model. After percutaneously induced myocardial infarction, female landrace swine received treatment with novel agents through either: (1) thoracotomy and transepicardial injection, (2) catheter-based transendocardial injection, or (3) intravenous infusion via jugular vein osmotic minipump. The procedures employed for each technique are reproducible, resulting in reliable cardioactive drug delivery. These models can be easily adapted to suit individual study designs, and each of these delivery techniques can be used to investigate a variety of possible interventions. Therefore, these methods are a useful tool for translational scientists pursuing novel biological approaches in cardiac repair following myocardial infarction.

Efficacy and safety of catheter ablation as first-line therapy for the management of ventricular tachycardia.

BACKGROUND: Ventricular tachycardia (VT) is associated with significantly increased morbidity and mortality. Catheter ablation (CA) in line with an implantable cardioverter-defibrillator (ICD) is highly effective in VT management; however, it is unknown if CA should be considered as first-line therapy. The aim of this study is to verify the efficacy and safety of CA as first-line therapy for the first VT presentation (as adjunctive to ICD insertion), compared to initial ICD insertion and anti-arrhythmic drug (AAD) therapy. METHODS: Data from patients with the first presentation for VT from January 2017 to January 2021 was reviewed. Patients were classified as "ablation first" vs "ICD first" groups and compared the clinical outcomes between groups. RESULTS: One hundred and eighty-four consecutive patients presented with VT; 34 underwent CA as first-line therapy prior to ICD insertion, and 150 had ICD insertion/AAD therapy as first-line. During the median follow-up of 625 days, patients who underwent CA as first-line therapy had significantly higher ventricular arrhythmia (VA)-free survival (91% vs 59%, log-rank P = 0.002) and composite of VA recurrence, cardiovascular hospitalization, transplant, and death (84% vs 54%, log-rank P = 0.01) compared to those who did not undergo CA. Multivariate analysis revealed that first-line CA was the only protective predictor of VA recurrence (hazard ratio (HR) 0.20, P = 0.003). There were 3 (9%) peri-procedural complications with no peri-procedural deaths. CONCLUSION: Real-world data supports the efficacy and safety of CA as first-line therapy at the time of the first VT hospitalization, compared to the initial ICD implant and AAD therapy.

A Prospective, Multicentre Randomised Controlled Trial Comparing Catheter Ablation Versus Antiarrhythmic Drugs in Patients With Structural Heart Disease Related Ventricular Tachycardia: The CAAD-VT Trial Protocol.

IMPORTANCE: Randomised trials have shown that catheter ablation (CA) is superior to medical therapy for ventricular tachycardia (VT) largely in patients with ischaemic heart disease. Whether this translates to patients with all forms and stages of structural heart disease (SHD-e.g., non-ischaemic heart disease) is unclear. This trial will help clarify whether catheter ablation offers superior outcomes compared to medical therapy for VT in all patients with SHD. OBJECTIVE: To determine in patients with SHD and spontaneous or inducible VT, if catheter ablation is more efficacious than medical therapy in control of VT during follow-up. DESIGN: Randomised controlled trial including 162 patients, with an allocation ratio of 1:1, stratified by left ventricular ejection fraction (LVEF) and geographical region of site, with a median follow-up of 18-months and a minimum follow-up of 1 year. SETTING: Multicentre study performed in centres across Australia. PARTICIPANTS: Structural heart disease patients with sustained VT or inducible VT (n=162). INTERVENTION: Early treatment, within 30 days of randomisation, with catheter ablation (intervention) or initial treatment with antiarrhythmic drugs only (control). MAIN OUTCOMES, MEASURES, AND RESULTS: Primary endpoint will be a composite of recurrent VT, VT storm (≥3 VT episodes in 24 hrs or incessant VT), or death. Secondary outcomes will include each of the individual primary endpoints, VT burden (number of VT episodes in the 6 months preceding intervention compared to the 6 months after intervention), cardiovascular hospitalisation, mortality (including all-cause mortality, cardiac death, and non-cardiac death) and LVEF (assessed by transthoracic echocardiography from baseline to 6-, 12-, 24- and 36-months post intervention). CONCLUSIONS AND RELEVANCE: The Catheter Ablation versus Anti-arrhythmic Drugs for Ventricular Tachycardia (CAAD-VT) trial will help determine whether catheter ablation is superior to antiarrhythmic drug therapy alone, in patients with SHD-related VT. TRIAL REGISTRY: Australian New Zealand Clinical Trials Registry (ANZCTR) TRIAL REGISTRATION ID: ACTRN12620000045910 TRIAL REGISTRATION URL: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=377617&isReview=true.

Correlation of spatial patterns of endocardial pace mapping to underlying scar topography in patients with scar-related ventricular tachycardia.

INTRODUCTION: Endocardial pace mapping (PM) can identify conducting channels for ventricular tachycardia (VT) circuits in patients with structural heart disease (SHD). Recent findings show the temporal and spatial pattern of PM may aid identification of the surface harboring VT isthmii. The specific correlation of PM patterns to scar topography has not been examined. OBJECTIVE: To correlate the pattern of endocardial PMs to underlying scar topography in SHD patients with VT. METHODS: Data from patients undergoing VT ablation from August 2018 to February 2022 were reviewed. RESULTS: Sixty-three patients with SHD-related VT (mean age 65 ± 14 years) with 83 endocardial PM correlation maps were analysed. Two main correlation patterns were identified, an "abrupt-change correlation pattern (AC-pattern)" and "centrifugal-attenuation correlation pattern (CA-pattern)." AC-pattern had lower scar ratio (unipolar/bipolar % scar area; 1.1 vs. 1.5, p < .001), had longer maximal stimulus-QRS intervals (97.5 vs. 68 ms, p = .002), and higher likelihood of endocardial dominant scar (11/21 [52%] vs. 3/38 [8%], p < .001) than CA-pattern seen on intracardiac echocardiography (ICE). In contrast, CA-pattern was more likely to have epicardial dominant scar or mid-intramural scar on ICE (epicardial dominant scar; CA-pattern: 12/38 [32%] vs. AC-pattern: 1/21 [5%], p = .02, mid-intramural scar; CA-pattern: 15/38 [39%] vs. AC-pattern: 1/21 [5%], p = .005). CONCLUSIONS: The spatial pattern of endocardial PM in SHD-related VT directly correlates with scar topography. AC-pattern is associated with endocardial dominant scar on ICE with lower scar ratio and longer stimulus-QRS intervals, whereas CA-pattern is strongly associated with epicardial dominant or mid-intramural scar with higher scar ratio and shorter stimulus-QRS intervals.

Comparison of the arrhythmogenic substrate for ventricular tachycardia in patients with ischemic vs non-ischemic cardiomyopathy - insights from high-density, multi-electrode catheter mapping.

PURPOSE: The purpose of this study was to compare the differences of arrhythmogenic substrate using high-density mapping in ventricular tachycardia (VT) patients with ischemic (ICM) vs non-ischemic cardiomyopathy (NICM). METHODS: Data from patients presenting for VT ablation from December 2016 to December 2020 at Westmead Hospital were reviewed. RESULTS: Sixty consecutive patients with structural heart disease (ICM 57%, NICM 43%, mean age 66 years) having catheter ablation of scar-related VT with pre-dominant left ventricular involvement were included. ICM was associated with larger proportion of dense scar area (bipolar; 19 [12-29]% vs 6 [3-10]%, P < 0.001, unipolar; 20 [12-32]% vs 11 [7-19]%, P = 0.01) compared with NICM. However, the scar ratio (unipolar dense scar [%]/bipolar dense scar [%]) was significantly higher in NICM patients (1.2 [0.8-1.7] vs 1.7 [1.3-2.3], P = 0.003). Larger scar area in ICM was paralleled by higher proportion of complex electrograms (6 [2-13] % vs 3 [1-5] %, P = 0.01), longer and wider voltage based conducting channels, higher incidence of late potential-based conducting channels, longer VT cycle-length (399 ± 80 ms vs 359 ± 68 ms, P = 0.04) and greater maximal stimulation-QRS interval among sites with good pace-map correlation (75 [51-99]ms vs 48 [31-73]ms, P = 0.02). Ventricular arrhythmia (VA) storm was more highly prevalent in ICM than NICM (50% vs 23%, P = 0.03). During the follow-up period, NICM had a significantly higher cumulative incidence for the VA recurrence than ICM (P = 0.03). CONCLUSIONS: High-density multi-electrode catheter mapping of left ventricular arrhythmogenic substrate of NICM tends to show smaller dense scar area and higher scar ratio, compared with ICM, suggestive the extent of epicardial/intramural substrate, with paucity of substrate targets for ablation, which results in the worse outcomes with ablation.

Efficacy and safety of catheter ablation for Brugada syndrome: an updated systematic review.

BACKGROUND: Patients with Brugada syndrome (BrS) may experience recurrent ventricular arrhythmias (VAs). Catheter ablation is becoming an emerging paradigm for treatment of BrS. OBJECTIVE: To assess the efficacy and safety of catheter ablation in BrS in an updated systematic review. METHODS: We comprehensively searched the databases of Pubmed/Medline, EMBASE, and Cochrane Central Register of Controlled Trials from inception to 11th of August 2021. RESULTS: Fifty-six studies involving 388 patients were included. A substrate-based strategy was used in 338 cases (87%), and a strategy of targeting premature ventricular complex (PVCs)/ventricular tachycardias (VTs) that triggered ventricular fibrillation (VF) in 47 cases (12%), with combined abnormal electrogram and PVC/VT ablation in 3 cases (1%). Sodium channel blocker was frequently used to augment the arrhythmogenic substrate in 309/388 cases (80%), which included a variety of agents, of which ajmaline was most commonly used. After ablation procedure, the pooled incidence of non-inducibility of VA was 87.1% (95% confidence interval [CI], 73.4-94.3; I2 = 51%), and acute resolution of type I ECG was seen in 74.5% (95% CI [52.3-88.6]; I2 = 75%). Over a weighted mean follow up of 28 months, 7.6% (95% CI [2.1-24]; I2 = 67%) had recurrence of type I ECG either spontaneously or with drug challenge and 17.6% (95% CI [10.2-28.6]; I2 = 60%) had recurrence of VA. CONCLUSION: Catheter ablation appears to be an efficacious strategy for elimination of arrhythmias or substrate associated with BrS. Further study is needed to identify which patients stand to benefit, and optimal provocation protocol for identifying ablation targets.

Intracardiac echocardiography techniques to identify ventricular arrhythmia substrate.

Intracardiac echocardiography (ICE) is increasingly used to facilitate catheter ablation of ventricular arrhythmias (VA). It allows intraprocedural recognition of myocardial substrate, optimization of catheter-tissue contact, identification of anatomical barriers to ablation, and early recognition of complications. In the era where the 3-dimensionality of substrate for VA is increasingly recognized, ICE is invaluable in identifying scar topography in the endocardial, midmyocardial, and epicardial layers. ICE assists in identifying endocavitary structures that are a common source of VA in idiopathic and structural heart disease. Furthermore, as substrate imaging of the right ventricle has not been optimized with other imaging modalities, ICE offers a unique opportunity to visualize substrate in this chamber. Real-time substrate identification can be particularly useful where there are contraindications to use of other imaging modalities or the images are obscured by artefact in the presence of cardiac device leads. In this review we provide a step-by-step guide in the techniques used to image ventricular arrhythmia substrate with ICE. We also discuss the benefits and limitations of this technique in comparison to other imaging modalities.

Will the insulated-tip radiofrequency catheter transform ablation procedures?

Radiofrequency (RF) ablation has been the most widely employed energy source for catheter ablation to date. However, most of conventional RF ablation energy dissipates into the bloodstream before reaching the target tissue. Technology that conveys RF energy exclusively toward target tissue may potentially improve the quality, safety, and outcome of the RF ablation procedures. RF ablation using a novel insulated-tip catheter (Sirona Medical Technologies [SMT]) may refine RF ablation in the future to minimize the risk of iatrogenic complications. Although it is still unclear whether the results of the SMT catheter can be translated to a human beating heart, the data for SMT catheter of this study are very promising.

Clinical, electroanatomic and electrophysiologic characterization and outcomes of catheter ablation for ventricular tachycardia following valvular intervention.

INTRODUCTION: Ventricular tachycardia (VT) can occur following valvular interventions. There are limited data describing substrate and ablation approaches in such patients. We sought to describe the clinical, electrophysiologic, electroanatomic features and catheter ablation outcomes of patients with VT following aortic and/or mitral valve intervention. METHODS: Over 12-years, consecutive patients with aortic valve replacement (AVR) and/or mitral valve replacement (MVR) or repair, undergoing VT ablation, were identified from two centers. Clinical and procedural parameters and outcomes are described. RESULTS: Twenty-three patients (age 66 ± 14years, 78% male, left ventricular ejection fraction 37 ± 16%), with prior AVR (mechanical n = 6, bioprosthetic n = 2, transcatheter n = 1), MVR (mechanical n = 5, bioprosthetic n = 1), mitral valve repair (n = 6) and both mechanical AVR and MVR (n = 2), underwent VT ablation. Sixteen had concurrent ischemic cardiomyopathy, 10 with prior bypass surgery. Left ventricular access was obtained in 21/23 (91%) patients (transseptal n = 14, retrograde aortic n = 5, transapical n = 2), with perivalvular scar identified in 17/21 (81%). Re-entrant VT isthmi involved the perivalvular regions in 12/23 (52%) patients, and regions remote from the valve in the remainder; 9% had nonscar-related VT. Intramural substrate was ablated from adjacent chambers in 5/23 (22%) patients and with half-normal saline irrigation in 8/23 (35%) patients. There were no instances of catheter entrapment. Following final ablation, VA-free survival was 78% at 13-months. CONCLUSION: Only half of VT circuits following valvular interventions involve the valve regions themselves, while the remainder involves unrelated regions. Catheter ablation is safe and efficacious at treating VT following valvular intervention, but novel strategies may be required.

Catheter ablation of ventricular tachycardia in nonischemic cardiomyopathy with near-normal left ventricular ejection fraction.

BACKGROUND: Patients with idiopathic nonischemic cardiomyopathy (NICM) and near-normal left ventricular ejection fraction (LVEF) may develop ventricular tachycardia (VT). OBJECTIVE: The purpose of this study was to describe procedural characteristics and outcomes in patients requiring ablation for NICM-related VT with near-normal LVEF compared to impaired LVEF. METHODS: Over 8 years, 77 consecutive patients with NICM-related VT underwent catheter ablation. Of these patients, 47 had idiopathic NICM (20 near-normal LVEF, 27 impaired LVEF). Procedural characteristics and outcomes were compared. RESULTS: Mean age was 64 ± 12years, mean LVEF was 40% ± 14%, and 75% were male. In the near-normal LVEF group compared to the impaired LVEF group, LVEF was higher (54% ± 5% vs 30 ± 8%; P <.001), scar was predominantly located in the perivalvular left ventricle (LV) and basal septum (15/20 [75%]), was smaller in size [bipolar: 9.7 (6.2-32.4) cm2 vs 30.4 (21.1-37.6) cm2, P = .03; unipolar: 23.3 (6.6-39.9) cm2 vs 57.2 (42.2-74.9) cm2, P = .009], and required smaller areas of ablation [7.0 (5.9-14.2) cm2 vs 11.4 (8.5-16.7) cm2, P = .06]. Both groups experienced comparable procedure times, fluoroscopy doses, ablation times, VT cycle lengths, and acute success rates. After final ablation, VA-free survival was comparable between both groups (65% vs 63%; P = .63) at 12 months. CONCLUSION: Idiopathic NICM-related VT with near-normal LVEF was associated with discrete areas of arrhythmogenic, predominantly intramural, scar in the perivalvular LV and basal septum. Despite smaller scar, patients required similar ablation amounts and experienced comparable long-term outcomes compared to patients with idiopathic NICM-related VT and impaired LVEF. These findings underscore the "three-dimensionality" of substrate, whereby the intramural basal septum forms the third dimension and impacts ablation outcomes.