Hai, Jo Jo

Background: Cardiac amyloidosis (CA) is associated with sinus node dysfunction (SND) and conduction system disease (CSD) yet data on pacing indications and outcomes is scarce. Methods: Retrospective review of patients (pts) with CA who had device implantation due to pacing indication at our institution. Results: At total of 51 (mean age 67.2±9.2 years, 90.2% male) pts with immunoglobulin light chain (n=27, 52.9%), hereditary transthyretin (n=7, 13.7%) and wild-type transthyretin (n=17, 33.3%) CA were included. Indication for pacing was exercise intolerance (n=16, 31.4%), syncope (n=16, 31.4%), congestive heart failure (n=5, 9.8%) and palpitation (n=2, 3.9%) with SND (n=23, 45.1%), CSD (17=33.3%) and uncontrolled atrial fibrillation (n=11, 21.6%). 16 (31.4%) pts received defibrillators (ICD) for primary prevention, of whom 8 (15.7%) had left ventricular ejection fraction (LVEF) ≤35%. Atrial (P wave: 1.7±1.2mV, threshold: 1.1±0.5mV/0.5±0.2ms) and right ventricular (RV) (R wave: 7.9±3.8mV, threshold: 0.8±0.4mV/0.4±0.1ms) lead parameters were satisfactory at implantation. During follow-up (mean 36.6±33.6 months), 26 (51%) pts reported symptomatic improvement (SI). Syncope was the only predictor of SI (OR 16.4, 95%CI 1.8-145.2, p=0.01) while exercise intolerance was not (OR 0.09, 95%CI 0.02-0.44, p=0.003). First-time life-threatening ventricular arrhythmias (VA) occurred in 6 (11.8%) pts, 3 (5.9%) had ICD implanted for LVEF ≤35%, 3 (5.9%) without ICD and LVEF ≥35%. Syncope was not predictive of first-time VA. RV lead noise led to inappropriate ICD shocks in 1 patient. Atrial lead sensing failure occurred in 6 (11.8%) and loss of capture in 5 (9.8%). Conclusion: Device implantation in patients with cardiac amyloidosis is safe but atrial lead failure is common. Syncope usually improves with pacing whereas other factors should be considered in those presented with exercise intolerance. Selection of pts who need pacing for prophylactic ICD implantation is challenging as neither left ventricular ejection fraction nor syncope are predictive of arrhythmic events.

Objective Sudden cardiac arrest (SCA) is the most devastating outcome in hypertrophic cardiomyopathy (HCM). We evaluated repolarisation features on the surface electrocardiogram (ECG) to identify the potential risk factors for SCA. Methods Data was collected from 52 patients with HCM who underwent implantable cardioverter defibrillator (ICD) implantation. Leads V2 and V5 from the ECG closest to the time of ICD implant were utilised for measuring the Tpeak-Tend interval (Tpe), QTc, Tpe/QTc, T-wave duration and T-wave amplitude. The presence of the five traditional SCA-associated risk factors was assessed, as well as the HCM risk-SCD score. Results 16 (30%) patients experienced aborted cardiac arrest over 8.5±4.1 years, with 9 receiving an ICD shock and 7 receiving ATP. On univariate analysis, T-wave amplitude was associated with appropriate ICD therapy (HR per 0.1 mV 0.79, 95% CI 0.56 to 0.96, p=0.02). Aborted SCA was not associated with a greater mean QTc duration, Tpeak-Tend interval, T-wave duration, or Tpe/QT ratio. Multivariate analysis (adjusting for cardinal HCM SCA-risk factors) showed T-wave amplitude in Lead V2 was an independent predictor of risk (adjusted HR per 0.1 mV 0.74, 95% CI 0.57 to 0.97, p=0.03). Addition of T-wave amplitude in Lead V2 to the traditional risk factors resulted in significant improvement in risk stratification (C-statistic from 0.65 to 0.75) but did not improve the performance of the HCM SCD-risk score. Conclusions T-wave amplitude is a novel marker of SCA in this high risk HCM population and may provide incremental predictive value to established risk factors. Further work is needed to define the role of repolarisation abnormalities in predicting SCA in HCM.

Arrhythmogenic Substrate of Ventricular Arrhythmias at the AMCIntroductionCatheter ablation of ventricular arrhythmia (VA) at the fibrous aortic mitral continuity (AMC) has been described, yet the nature of the arrhythmogenic substrate remains unknown.MethodsProcedural records of 528 consecutive patients undergoing ablation of VA at Mayo Clinic, Rochester, MN, were reviewed. The electrocardiographic and electrophysiologic characteristics of patients with successful ablation at the AMC were analyzed to characterize the underlying arrhythmogenic substrate.ResultsOf the 21 patients (mean age 53.2 ± 13.4 years, 47.6% male) who underwent ablation of VA at the AMC with acute success, prepotentials (PPs) were found at the ablation sites preceding the ventricular electrogram (VEGM) during arrhythmias in 13 (61.9%) patients and during sinus rhythm in 7 (53.8%) patients. VAs with PPs were associated with a significantly higher burden of premature ventricular complexes (PVCs; 26.1 ± 10.9% vs. 14.9 ± 10.1%, P = 0.03), shorter VEGM to QRS intervals (9.0 ± 28.5 milliseconds vs. 33.1 ± 8.8 milliseconds, P = 0.03), lower pace map scores (8.7 ± 1.6 vs. 11.4 ± 0.8, P = 0.001), and a trend toward shorter V‐H intervals during VA (32.1 ± 38.6 milliseconds vs. 76.3 ± 11.1 milliseconds, P = 0.06) as compared to those without PP. A strong and positive correlation was found between V‐H interval and QRS duration during arrhythmia in those with PPs (B = 2.11, R2 = 0.97, t = 13.7, P < 0.001) but not in those without PPs.ConclusionLocal EGM characteristics and relative activation time of the His bundle suggest the possibility of conduction tissue as the origin for VA arising from the fibrous AMC. Specific identification and targeting of PPs when ablating VAs at this location may improve procedural success.

The traditional route for teaching cardiac anatomy involves didactic instruction, cadaver dissections, and familiarization with the main structure and relationships of the cardiac chambers, valves, and vasculature. In contemporary cardiac electrophysiology, however, a very different view of anatomy is required including details rarely appreciated with a general overview. In this review, we discuss the critical advances in cardiac electrophysiology that were possible only because of understanding detailed anatomic relationships. While we briefly discuss the clinical relevance, we explain in depth the necessary structural information for the student of clinical anatomy. Interspersed through the text are boxes that highlight and summarize the critical pieces of knowledge to be borne in mind while studying the fascinating structural anatomy of the human heart. Clin. Anat. 27:885–893, 2014. © 2014 Wiley Periodicals, Inc.

ECG Lead I and Outflow Tract ArrhythmiaIntroductionOutflow tract ventricular arrhythmia (OTVA) can be complicated to target for ablation when originating from either the periaortic or pulmonary valve (PV) region. Both sites may present with a small R wave in lead V1. However, the utility of lead I in distinguishing these arrhythmia locations is unknown.Methods and ResultsThirty‐six consecutive patients (mean age 41 ± 14 years, 13 male) underwent catheter ablation for OTVA. OTVA origin was determined from intracardiac electrogram tracings and electroanatomic maps. Observers blinded to results measured QRS waveform amplitude and duration from standard 12‐lead ECG tracings. Measurements with highest diagnostic performance were modeled into an algorithm. Sites of successful ablation were anterior right ventricular outflow tract (RVOT; n = 6), posterior RVOT (n = 4), PV (n = 18), and right coronary cusp (RCC; n = 8). Highest performing surface ECG discriminators were from lead I to V1 vectors: RCC, lead I R wave ≥ 1.5 mV, and V1 R wave ≥2.0 mV (sensitivity 87%, specificity 93%); PV, V1 R wave > 0 mV, and lead I R/(R+S) ≤ 0.75 (sensitivity 78%, specificity 72%); anterior RVOT, V1 R wave = 0 mV, and lead I R/(R+S) <0.4 (sensitivity 67%, specificity 97%); posterior RVOT, V1 R wave > 0 mV, and lead I R/(R+S) > 0.75 (sensitivity 75%, specificity 84%). Sequential algorithmic application of these criteria resulted in an overall accuracy of 72% in predicting site of OTVA origin.ConclusionsA relatively large R wave in lead I is seen with RCC origin but not PV origin. A sequential algorithm has limited but potentially significant value beyond assessment of lead I in approaching OTVA.

Ablation and Mapping of the Conus Papillary MuscleCatheter ablation is an increasingly used and successful treatment choice for right ventricular outflow tract (RVOT) arrhythmias. While the role of endocavitary structures and the regional morphology of the ventricular inflow tract and the right atrium as a cause for difficulty with successful ablation are well described, similar issues within the RVOT are not well understood. It is also not commonly appreciated that one of the papillary muscles is located within the proximal RVOT. We report 3 patients in which ventricular arrhythmia was targeted and ablated in the conus papillary muscle. The anatomic features, potential role of the fascicular conduction system, and unique challenges with mapping arrhythmia arising from this structure are discussed.