Killu, Ammar M.

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.

Background— Ventricular tachycardia and premature ventricular complexes (PVCs) most frequently occur in the context of structural heart disease. However, the burden of idiopathic ventricular arrhythmias (IVA) in the general population is unknown. Methods and Results— We identified incident cases of IVA between 2005 and 2013 from Olmsted County, Minnesota, using the Rochester Epidemiology Project database. For PVC cohorts, we included those with frequent (defined as ≥100 PVC/24 hours) symptomatic PVCs. We defined IVA-associated cardiomyopathy as a drop in ejection fraction of ≥10% from baseline. Between 2005 and 2013, we identified 614 individuals with incident IVA (229 [37.3%] were male; average age was 52.1±17.2 years). Of these, 177 (28.8%) had idiopathic ventricular tachycardia, 408 (66.5%) had symptomatic PVCs, and 29 (4.7%) had IVA-associated cardiomyopathy. The age- and sex-adjusted incidence rates in 2005 to 2007, 2008 to 2010, and 2011 to 2013 were 44.9 per 100 000 (95% confidence interval [CI], 38.0–51.8), 47.6 per 100 000 (95% CI, 40.8–54.5), and 62.0 per 100 000 (95% CI, 54.4–69.6), respectively. In idiopathic ventricular tachycardia, there was an increase in incidence rate with ages ( P <0.001) but not between sexes ( P =0.12). The age-adjusted incidence of symptomatic PVC was higher in females than in males (46.2 per 100 000 [95% CI, 40.9–51.6] versus 20.5 per 100 000 [95% CI, 16.8–24.3]; P <0.001). The small number of individuals with IVA-associated cardiomyopathy precluded any formal testing. Conclusions— The incidence of IVA is increasing. Furthermore, overall incidence increases with age. Although the rate of idiopathic ventricular tachycardia is similar across sexes, women have a higher incidence of symptomatic PVC.

BackgroundAutomated external defibrillators can provide life‐saving therapies to treat ventricular fibrillation. We developed a prototype unit that can deliver a unique shock waveform produced by four independent capacitors that is delivered through two shock vectors, with the rationale of providing more robust shock pathways during emergent defibrillation. We describe the initial testing and feasibility of this unique defibrillation unit, features of which may enable downsizing of current defibrillator devices.MethodsWe tested our defibrillation unit in four large animal models (two canine and two swine) under general anesthesia. Experimental defibrillation thresholds (DFT) were obtained by delivery of a unique waveform shock pulse via a dual‐vector pathway with four defibrillation pads (placed across the chest). DFTs were measured and compared with those of a commercially available biphasic defibrillator (Zoll M series, Zoll Medical, Chelmsford, MA, USA) tested in two different vectors. Shocks were delivered after 10 seconds of stable ventricular fibrillation and the output characteristics and shock outcome recorded. Each defibrillation series used a step‐down to failure protocol to define the defibrillation threshold.ResultsA total of 96 shocks were delivered during ventricular fibrillation in four large animals. In comparison to the Zoll M series, which delivered a single‐vector, biphasic shock, the energy required for successful defibrillation using the unique dual‐vector biphasic waveform did not differ significantly (P = 0.65).ConclusionsOur early findings support the feasibility of a unique external defibrillation unit using a dual‐vector biphasic waveform approach. This warrants further study to leverage this unique concept and work toward a miniaturized, portable shock delivery system.

Percutaneous Pericardiotomy ToolIntroductionEpicardial procedures frequently require pericardial manipulation. We aimed to develop a nonsurgical percutaneous pericardial modification tool that may (1) facilitate epicardial‐based procedures by enabling adhesiolysis or (2) attenuate the myocardial constraining effect of the pericardium.MethodsThree novel devices were developed to enable pericardiotomy, all of which can be deployed in over‐the‐wire fashion following percutaneous epicardial access. The grasper permits us to seize the pericardial membrane providing leverage for incision. The scissors enables anterograde cutting maneuvers. The reverse‐slitter allows retrograde incisions; in addition, this device has a deflectable tip that increases the potential cutting area. We optimized these tools for safety by including electrodes to test for phrenic nerve stimulation as well as myocardial stimulation to determine directionality of the cutting devices. The base of the scissors and reverse‐slitter are also blunt ensuring that the cutting element is always away from the myocardium.ResultsFollowing 5 nonbeating heart bench test experiments for prototype development, 11 animal (9 canine, 2 swine) studies were performed. Of these 2 were proof‐of‐concept open chest studies; the remaining 9 were entirely closed‐chest, percutaneous procedures allowing for remodification of the prototypes. The tools successfully permitted incision of the pericardium in all studies. Hemodynamic measurements were assessed postincision and showed no compromise of systolic function. No coronary artery or phrenic nerve damage was seen in any study.ConclusionPercutaneous pericardiotomy is feasible and appears to be safe. It may provide leverage in epicardial‐based procedures and offer treatment options in disease processes characterized by pericardial restraint.

BackgroundMany patients with atrial fibrillation (AF) or atrial flutter (Aflutter) have concomitant sinus node dysfunction (SND). Ablation may result in injury to the sinus node complex or its blood supply resulting in sinus arrest and need for temporary pacing. We sought to characterize patients who develop acute SND (ASND) during/immediately after AF/Aflutter ablation.MethodsWe performed a retrospective analysis of AF/Aflutter ablation patients between January 1, 2010 and February 28, 2015 to characterize those who required temporary pacemaker (TPM) implantation due to ASND (sinus arrest, sinus bradycardia <40 beats/min, or junctional rhythm with hemodynamic compromise) following atrial ablation.ResultsOf 2,151 patients, eight patients (<0.5%) with ASND manifesting as sinus arrest (n = 2), severe sinus bradycardia (n = 2), and junctional rhythm with hemodynamic compromise (n = 4) were identified (all male, age 66 ± 9.9 years, 4/8 [50%] persistent AF). AF ablation was performed in four, atypical Aflutter in one, and AF/Aflutter in three patients. The ablation set consisted of: pulmonary vein (PV) isolation (n = 6), roof line ablation (n = 6), mitral annulus‐left inferior PV line ablation (n = 5), left atrial appendage‐mitral annulus ablation (n = 1), cavotricuspid isthmus ablation (n = 5), and isolation or ablation near the superior vena cava (SVC, n = 4). Patients with peri‐SVC ablation were more likely to develop ASND (P = 0.03). All patients received TPM; six received permanent pacemaker before discharge, performed 3.5 days postablation (range 2–6 days). At 3‐month device interrogation, all patients were atrially paced >50%.ConclusionASND is a rare complication of atrial ablation. It may be more common when peri‐SVC ablation is performed and may necessitate permanent pacemaker implantation.

Endovascular Stimulation for Treatment of HypotensionBackgroundWe have previously shown that sympathetic ganglia stimulation via the renal vein rapidly increases blood pressure. This study further investigated the optimal target sites and effective energy levels for stimulation of the renal vasculatures and nearby sympathetic ganglia for rapid increase in blood pressure.MethodsThe pre‐study protocol for endovascular stimulations included 2 minutes of stimulation (1–150 V and 10 pulses per second) and at least 2 minutes of rest during poststimulation. If blood pressure and/or heart rate were changed during the stimulation, time to return to baseline was allowed prior to the next stimulation.ResultsIn 11 acute canine studies, we performed 85 renal artery, 30 renal vein, and 8 hepatic vasculature stimulations. The mean arterial pressure (MAP) rapidly increased during stimulation of renal artery (95 ± 18 mmHg vs. 103 ± 15 mmHg; P < 0.0001), renal vein (90 ± 16 mmHg vs. 102 ± 20 mmHg; P = 0.001), and hepatic vasculatures (74 ± 8 mmHg vs. 82 ± 11 mmHg; P = 0.04). Predictors of a significant increase in MAP were energy >10 V focused on the left renal artery, bilateral renal arteries, and bilateral renal veins (especially the mid segment). Overall, heart rate was unchanged, but muscle fasciculation was observed in 22.0% with an output >10 V (range 15–150 V). Analysis after excluding the stimulations that resulted in fasciculation yielded similar results to the main findings.ConclusionsStimulation of intra‐abdominal vasculatures promptly increased the MAP and thus may be a potential treatment option for hypotension in autonomic disorders. Predictors of optimal stimulation include energy delivery and the site of stimulation (for the renal vasculatures), which informs the design of subsequent research.

ObjectivesTo determine the frequency and predictors of pericardial effusion following epicardial sheath removal.BackgroundPericardial effusion can occur following cardiac surgical or interventional procedures including percutaneous epicardial access (EpiAcc), which is increasingly used as part of electrophysiology ablation procedures.MethodsA retrospective analysis of the Mayo Clinic comprehensive electronic medical record was performed from all patients who underwent planned EpiAcc as part of an electrophysiology ablation procedure between January 1, 2004 and June 30, 2013.ResultsOf 144 patients (mean age 51.3 ± 15.5 years, 68% male) who underwent planned EpiAcc as part of an electrophysiology ablation (95.8% pericardial access success rate), seven (4.9%) developed a postoperative pericardial effusion requiring repeat EpiAcc. Inferior access was utilized in 74 (51.4%) patients. Patients with pericardial effusion tended to be younger (41.1 years vs 51.8 years, P = 0.08) and were more likely to have undergone inferior approach access (85.7% vs 49.6%, P = 0.06) than those who did not develop postoperative pericardial effusion. Seventy‐one percent of patients with postoperative pericardial effusion versus 32.1% of patients without postoperative pericardial effusion had a preprocedure ejection fraction ≥55% (P = 0.03). There were no procedural‐related deaths, and no difference in mortality between groups.ConclusionsPostoperative pericardial effusion requiring repeat access/drainage was relatively infrequent, occurring in 4.9% of patients shortly after epicardial procedures. While the majority occur early and therefore require close observation, some patients may present in a delayed manner.