Arthur M. Yue

Determination of Human Ventricular Repolarization by Noncontact Mapping Validation With Monophasic Action Potential Recordings

Background—Noncontact mapping (NCM) has not been validated as a clinical technique to measure ventricular repolarization. We used NCM to determine repolarization characteristics by analysis of reconstructed unipolar electrograms (UEs) at the same sites as monophasic action potential (MAP) recordings in the human ventricle. Methods and Results—MAPs were recorded from a total of 355 beats at 46 sites in the left or right ventricle of 9 patients undergoing ablation of ventricular tachycardia guided by NCM (EnSite system). Measurements were made during sinus rhythm, constant right ventricular pacing, and ventricular extrastimuli during restitution-curve construction. The EnGuide locator signal was used to document MAP catheter locations on the endocardial geometry. UE-determined activation-recovery interval (ARI) measured at the maximum derivative of the T wave (Wyatt method) and the minimum derivative of the positive T wave (alternative method) was correlated with MAP measured at 90% repolarization (MAP90%) at the same sites. ARI correlated with MAP90% during steady state by the Wyatt method (r=0.83, P<0.001) and the alternative method (r=0.94, P<0.001). Restitution curves constructed from MAP and UE data exhibited the same characteristics, with a mean correlation coefficient of 0.95 (range, 0.90 to 0.99, P<0.001). The error between ARI and MAP90% was greater over a shorter diastolic coupling interval but was not influenced by distance of the sampling site from the multielectrode array. Conclusions—NCM accurately determines steady-state and dynamic endocardial repolarization in humans. Global, high-density, NCM data could be used to characterize abnormalities of human ventricular repolarization.

Safety and efficacy of multipolar pulmonary vein ablation catheter vs. irrigated radiofrequency ablation for paroxysmal atrial fibrillation: a randomized multicentre trial.

Aims The current challenge in atrial fibrillation (AF) treatment is to develop effective, efficient, and safe ablation strategies. This randomized controlled trial assesses the medium-term efficacy of duty-cycled radiofrequency ablation via the circular pulmonary vein ablation catheter (PVAC) vs. conventional electro-anatomically guided wide-area circumferential ablation (WACA). Methods and results One hundred and eighty-eight patients (mean age 62 ± 12 years, 116 M : 72 F) with paroxysmal AF were prospectively randomized to PVAC or WACA strategies and sequentially followed for 12 months. The primary endpoint was freedom from symptomatic or documented >30 s AF off medications for 7 days at 12 months post-procedure. One hundred and eighty-three patients completed 12 m follow-up. Ninety-four patients underwent PVAC PV isolation with 372 of 376 pulmonary veins (PVs) successfully isolated and all PVs isolated in 92 WACA patients. Three WACA and no PVAC patients developed tamponade. Fifty-six percent of WACA and 60% of PVAC patients were free of AF at 12 months post-procedure (P = ns) with a significant attrition rate from 77 to 78%, respectively, at 6 months. The mean procedure (140 ± 43 vs. 167 ± 42 min, P<0.0001), fluoroscopy (35 ± 16 vs. 42 ± 20 min, P<0.05) times were significantly shorter for PVAC than for WACA. Two patients developed strokes within 72 h of the procedure in the PVAC group, one possibly related directly to PVAC ablation in a high-risk patient and none in the WACA group (P = ns). Two of the 47 patients in the PVAC group who underwent repeat ablation had sub-clinical mild PV stenoses of 25–50% and 1 WACA patient developed delayed severe PV stenosis requiring venoplasty. Conclusion The pulmonary vein ablation catheter is equivalent in efficacy to WACA with reduced procedural and fluoroscopy times. However, there is a risk of thrombo-embolic and pulmonary stenosis complications which needs to be addressed and prospectively monitored. ClinicalTrials.gov Identifier NCT00678340.

Global Dynamic Coupling of Activation and Repolarization in the Human Ventricle

Background— The ability to determine spatial and dynamic changes in ventricular repolarization may help to understand arrhythmogenic mechanisms in humans. We hypothesized that noncontact mapping could be used to investigate global activation-repolarization coupling in the human ventricle during steady state and premature extrastimulation. Methods and Results— Activation-recovery intervals (ARIs) determined from reconstructed unipolar electrograms by the Ensite system were analyzed during sinus rhythm, constant pacing, spontaneous ventricular ectopic beats, and premature stimulation at intermediate and short coupling intervals in the left or right ventricle of 13 patients (6 female; mean age, 48 years) without structural myocardial disease. ARIs were measured from 32 sites in each ventricle with the use of a method validated with monophasic action potential recordings and unipolar contact electrograms. Global T-wave distribution was displayed on a 3-dimensional geometry of the ventricle, with polarities opposite to the direction of activation during steady state and premature stimulation. There was a significant inverse correlation between activation times and ARIs during sinus rhythm, ventricular ectopy, and premature stimulation (r=0.72, slope=−0.76, P<0.001). Premature stimuli at short coupling intervals flattened the regression slope compared with sinus rhythm (−0.61 versus −0.81; P=0.05), but the global pattern of repolarization was preserved. In comparison to our method, the Wyatt method of ARI measurement failed to demonstrate significant coupling between activation and repolarization (r=0.34, slope=0.19). Conclusions— Global, dynamic repolarization mapping of the human ventricle is feasible. An inverse coupling of activation and repolarization during steady state and premature stimulation may preserve electric stability in the normal ventricle.

Successful Percutaneous Ablation of Ventricular Tachycardia in Congenitally Corrected Transposition of the Great Arteries, a Case Report

Ventricular tachycardia (VT) is rarely recognized in patients with congenitally corrected transposition of the great arteries (CCTGA). We describe a 48-year-old woman with CCTGA, systemic atrioventricular valve replacement for Ebsteinoid malformation of the valve, ventricular dysfunction and ventricular tachycardia related to the previous surgical scar. The patient had successful non-contact mapping and radiofrequency ablation of the offending tachycardia substrate.

Oversensing and Shock Delivery in the S‐ICD: Five Shocks Two Mechanisms

A 69-year-old male was recommended to have an implantable cardioverter defibrillator (ICD) for secondary prevention of sudden cardiac death. The patient had a relative contraindication to a transvenous ICD (TV-ICD) by having a large right atrial thrombus despite being on warfarin with a therapeutic international normalized ratio. The patient was assessed for suitability for a subcutaneous ICD (S-ICD) and successfully passed the electrocardiogram (ECG) screening process. An S-ICD (Model number 1010, Boston Scientific, Natick, MA, USA) was implanted without complication prior to the patient’s discharge home. The device was programmed with a conditional zone between 190 beats/min and 230 beats/min and a shock zone for rates greater than 230 beats/min. Sensing was from the secondary vector. The patient subsequently presented on four occasions having received a total of five inappropriate shocks from the S-ICD. The first four episodes were from the same mechanism. The patient underwent ventricular tachycardia (VT) ablation that was successful at preventing VT recurrence. The patient then had a fifth episode of inappropriate therapy. The S-ICD was replaced with a TV-ICD. No further inappropriate shocks have occurred since. Questions:

Screening for Atrial Fibrillation using Economical and accurate TechnologY (SAFETY)—a pilot study

Introduction Atrial fibrillation (AF) is a cause of stroke and a marker of atherosclerosis and of all patients with stroke, around 17% have AF. The screening and treatment of AF could prevent about 12% of all strokes. Several relatively low-cost devices with good accuracy now exist which can detect AF including WatchBP and AliveCor. However, they can only measure the ECG or pulse over short time periods. Inexpensive devices such as heart rate monitors, which are widely available, can measure heart rate for prolonged periods and may have potential in screening for AF. This study aims to determine the accuracy of AliveCor and WatchBP along with a bespoke algorithm using a heart rate monitor belt (Polar H7) and a wearable RR interval recorder (Firstbeat Bodyguard 2) for detecting AF during a single screening visit in primary care patients. Methods/analysis A multicentre case–control diagnostic study comparing the four different devices for the detection of AF with a reference standard consisting of a 12-lead ECG in GP surgeries across Hampshire, UK. We aim to recruit 92 participants with AF and 329 without AF aged 65 years and over. We will ask participants to rate comfort and overall impression for each device. We will collect qualitative data from participants capturing their experience of using wearable devices in order to evaluate acceptability. We will collect data from GPs to determine their views on AF screening. Ethics and dissemination This protocol was approved by the London—City & East Research Ethics Committee in June 2016. The findings of the trial will be disseminated through peer-reviewed journals, national and international conference presentations and the Atrial Fibrillation Association, UK. Trial registration number ISRCTN17495003, Pre-results.

Strategies to reduce infections during the cardiac implantable electronic device implant: a time to name and shame

The adage that prevention is better than cure is held to be true by many. An infected cardiac implantable electronic device (CIED) is a disaster for the patient and can reflect a failure of effective healthcare. For the patient it often means risk of significant morbidity and mortality, suffering symptoms of sepsis, courses of antimicrobial medication, and admission to hospital and additional procedures—usually for system extraction and re-implantation. While system extraction has traditionally been thought to carry significant morbidity and mortality, recent data from high-volume centres describe very low rates of mortality.1 Nevertheless, extraction for an infective indication tends to confer worse prognosis.1,2 For the healthcare provider, the cost is measured in pounds/dollars/euros and in hospital bed occupancy. In this article, we discuss the trends in CIED infection and current inadequacy in guidelines addressing the prevention of CIED infection. We draw parallels with surgical specialties and learn from their experience in dealing with and reducing rates of surgical site infections (SSIs). Finally, we propose a mechanism to comprehensively address the issue of reducing the incidence of CIED-related infections. In spite of the costs of CIED infection detailed above, strategies to implement ‘upstream’ CIED infection prevention are inconsistently applied and are variably successful. In the USA, worrying data demonstrate an increase in the incidence of CIED infection, up from a baseline of 1.6–2.5% over recent years.3 The increased rate is thought to reflect the trend of implanting more complex devices into patients with greater co-morbidities. Also, patients are living longer and therefore have more device revisions. It is well recognized that with each device revision there is an incremental risk of complication. European data …

Monitoring of arrhythmia and sudden death in a hemodialysis population: The CRASH-ILR Study

Introduction It has been suggested that sudden cardiac death (SCD) contributes around 50% of cardiovascular and 27% of all-cause mortality in hemodialysis patients. The true burden of arrhythmias and arrhythmic deaths in this population, however, remains poorly characterised. Cardio Renal Arrhythmia Study in Hemodialysis (CRASH-ILR) is a prospective, implantable loop recorder single centre study of 30 established hemodialysis patients and one of the first to provide long-term ambulatory ECG monitoring. Methods 30 patients (60% male) aged 68±12 years receiving hemodialysis for 45±40 months with varied etiology (diabetes 37%, hypertension 23%) and left ventricular ejection fraction (LVEF) 55±8% received a Reveal XT implantable loop recorder (Medtronic, USA) between August 2011 and October 2014. ECG data from loop recorders were transmitted at each hemodialysis session using a remote monitoring system. Primary outcome was SCD or implantation of a (tachy or bradyarrhythmia controlling) device and secondary outcome, the development of arrhythmia necessitating medical intervention. Results During 379,512 hours of continuous ECG monitoring (mean 12,648±9,024 hours/patient), there were 8 deaths—2 SCD and 6 due to generalised deterioration/sepsis. 5 (20%) patients had a primary outcome event (2 SCD, 3 pacemaker implantations for bradyarrhythmia). 10 (33%) patients reached an arrhythmic primary or secondary end point. Median event free survival for any arrhythmia was 2.6 years (95% confidence intervals 1.6–3.6 years). Conclusions The findings confirm the high mortality rate seen in hemodialysis populations and contrary to initial expectations, bradyarrhythmias emerged as a common and potentially significant arrhythmic event.

Careful Observation of Changes in Cycle Length in the Evaluation of Atrial Tachycardia Mechanism.

A 79-year-old gentleman with known ischemic cardiomyopathy and a 6-month history of lethargy on exertion was referred for catheter ablation. His 12-lead electrocardiograph suggested an atypical atrial flutter morphology with positive flutter waves in the inferior and right precordial leads. During the procedure, informed by a distal (d) to proximal (p) coronary sinus (CS) activation pattern, a 4 mm irrigated tip ablation catheter was advanced into the left atrium. Initial activation mapping started at the antero-septal left atrium at approximately a 9 o’clock position (Fig. 1A) relative to the mitral annulus, and then moved a 10 o’clock position (Fig. 1B). Based on just these initial mapping findings, what tachycardia mechanism is ruled out? What window of interest would you set, relative to CSp, if you were to perform activation mapping?

Examination of a Middle Cardiac Vein Defibrillation Coil as Stand‐Alone Anode, Auxiliary Anode, and Bystander Electrode in a Transvenous Defibrillation Circuit

In porcine studies anodes in the middle cardiac vein compare favorably with those in the RV. It has not been demonstrated whether the RV and middle cardiac vein or the middle cardiac vein alone anodes are superior when shocking to a conventional SVC and active housing cathode nor whether a bystander middle cardiac vein electrode exerts a passive electrode affect. Twelve pigs were anesthetized and had an active housing implanted in the left pectoral region and defibrillation coils placed at the RV apex and in the SVC. A custom‐made defibrillation coil (Ela Medical) was advanced into the middle cardiac vein through a 9 Fr transvenous catheter. The DFT for three anodes (RV; RV and middle cardiac vein; middle cardiac vein) to the SVC and active housing was then assessed by a three reversal binary search, the order of testing was randomized. In seven animals DFT was assessed in the same way for the configuration of RV to SVC and active housing twice more, with and without a bystander middle cardiac vein coil electrode in place. The results were middle cardiac vein 7.5 ± 1.7 J, RV and middle cardiac vein 7.3 ± 1.7 J reduced DFT significantly compared to RV 13.8 ± 4.2 J (both P < 0.000). There was no significant difference between the middle cardiac vein and the middle cardiac vein and RV (P = 0.67, 95% CI for difference − 0.64–0.96). The DFT of RV to SVC and the active housing was the same with (13.2 ± 4.0) and without (13.7 ± 4.2) the middle cardiac vein bystander coil in place (P = 0.177, 95% CI for difference − 0.33–1.33 J). Shocking to a SVC and active housing cathode, middle cardiac vein, and RV and middle cardiac vein anodes are equally effective in lowering DFT compared to the RV. The middle cardiac vein coil electrode does not exert a passive electrode affect on the RV to the SVC and active housing defibrillation.