Circulation: Arrhythmia and Electrophysiology On the Beat March 2018 - a podcast by Paul J. Wang, MD

Paul Wang:         Welcome to the monthly podcast “On The Beat”, for Circulation: Arrhythmia and Electrophysiology. I am Dr. Paul Wang, Editor-in-Chief, with some of the key highlights from this month's issue. We'll also hear from Dr. Suraj Kapa, reporting on new research from the latest journal articles in the field.

                                In our first article, Adetola Ladejobi and associates studied 1,433 patients, between 2000 and 2012, who were discharged alive after sudden cardiac arrest. A reversible and correctable cause was identified in 792 patients, or 55%. A reversible cause for sudden cardiac arrest was defined as significant electrolyte or metabolic abnormality, evidence of acute myocardial infarction or ischemia, recent initiation of antiarrhythmic drug, or illicit drug use, or other reversible circumstances.

                                Of the 792 sudden cardiac arrest survivors, due to reversible or correctable cause, 207 or 26% of the patients received an ICD after their indexed sudden cardiac arrest. During a mean follow-up of 3.8 years, 319 or 40% of patients died. ICD implantation was highly associated with a lower all-cause mortality, p < 0.001, even after correcting for unbalanced baseline characteristics.

                                In subgroup analyses, only patients with sudden cardiac arrest, were not associated with myocardial infarction, extracted benefit from the ICD, p < 0.001.

                                The authors concluded that in survivors of sudden cardiac arrest, due to a reversible and correctable cause, ICD therapies associated with lower all-cause mortality, except if the sudden cardiac arrest was due to myocardial infarction.

                                Further prospect of multi-center randomized control trials will be needed to confirm this observation.

                                In our next study, Carlo Pappone and associates, studied 81 patients with persistent atrial fibrillation, randomized to undergo high density electrophysiological mapping, to identify repetitive regular activities, before modified circumferential pulmonary vein ablation, or modified circumferential pulmonary vein ablation alone. The primary endpoint was freedom from arrhythmia recurrence at one year.

                                In the 81 patients with persistent atrial fibrillation, there were 479 regions exhibiting repetitive regular activities in these patients, or 5.9 repetitive regular activities per patient. There were 232 regions in the mapping group, which consisted of 41 patients, and 247 regions in the control group, consisting of 40 patients. Overall, 39% of the repetitive regular activities were identified within pulmonary veins, whereas 61% were identified in non-pulmonary vein regions.

                                Mapping-guided ablation resulted in higher arrhythmia termination rate, as compared to conventional strategy, 61% vs. 30%, p < 0.007. Total RF duration, mapping, and fluoroscopy times were not significantly different between the groups. No major procedure related adverse events occurred.

                                After one year, 73% of the mapping group of patients were free of recurrences, compared to 50% of the control group, p = 0.03.

                                The authors concluded that targeted ablation of regions showing repetitive regular activities provided adjunctive benefit in terms of arrhythmia freedom at one year in treatment of patients with persistent atrial fibrillation. These findings should be confirmed by additional larger randomized multi-centered studies.

                                In the next article, Maciej Kubala and associates examine repolarization abnormalities in 40 patients with arrhythmogenic right ventricular cardiomyopathy, comparing extent and location of abnormal T-waves of one millimeter or greater in depth, downsloping elevated ST segment in two or more adjacent leads to the area and location of endocardial bipolar and unipolar, and epicardial bipolar voltage abnormalities. They found an abnormal unipolar right ventricular endocardial area of 33.4% with presence in eight patients without negative T-waves. Patients with negative T-waves extending beyond V3, seen in 20 patients, had larger low bipolar and unipolar endocardial areas, and larger epicardial low bipolar areas, compared to those with negative T-waves limited to leads V1 to V3.

                                ECG localization of negative T-waves regionalized to the location of substrate. Patients with downsloping elevated ST segment, all localized to leads V1, V2 had more unipolar endocardial abnormalities involving outflow in mid-right ventricle, compared to patients without downsloping elevated ST segment.

                                The authors concluded that in arrhythmogenic right ventricular cardiomyopathy, abnormal electric current areas were proportional to the extent of T-wave inversion on the 12 lead electrocardiogram. Marked voltage abnormalities can exist without repolarization changes. Downsloping elevated ST segment patterns in V1 and V2 occurs with more unipolar endocardial voltage abnormalities, consistent with more advanced trans neural disease.

                                In the next manuscript, Teresa Oloriz and associates examine the timing and value of program stimulation after catheter ablation for ventricular tachycardia. They performed 218 program ventricular stimulations six days after ablation in 210 consecutive patients, 48% with ischemic cardiomyopathy in the median left ventricular ejection fraction of 37%. After ablation, ICDs were programmed according to NIPS results. Class A were noninducible, Class B non documented inducible VT, and Class C documented inducible VT. Concordance between the programmed ventricular stimulation at the end of the procedure and at six days was 67%. The positive predictive value and negative predictive value were higher for the programmed ventricular stimulation at day six. Ischemic patients and those with preserved ejection fraction showed the highest negative predictive value.

                                Among noninducible patients at the end of the procedure, but inducible at day six, 59 patients had VT recurrence at one year follow-up. Recurrences were 9% when both studies were noninducible. There were no inappropriate shocks, incidents of syncope with 3%, none harmful. The rate of appropriate shocks per patient per month according to NIPS was significantly reduced, comparing the month before and after the ablation.

                                The authors concluded that programmed ventricular stimulation at day six predicts VT recurrence.

                                In the next study, Tor Biering-Sørensen and associates examined ECG global electrical heterogeneity, GEH, in its longitudinal changes, are associated with cardiac structure and function, in their Atherosclerosis Risk and Community study, ARIC, consisting of 5,114 patients, 58% which were female and 22% African Americans. Using the resting 12-lead ECGs, and echocardiographic assessments of left ventricular ejection fraction, global strain, left ventricular mass index, end diastolic volume index, end systolic volume index at visit five.

                                Longitudinal analysis included ARIC participants with measured GEH at visits one to four. GEH was quantified by spatial ventricular gradient, the QRST angle, and the sum of the absolute QRST integral. Cross sectional and longitudinal regressions were adjusted for manifest subclinical cardiovascular disease.

                                Having four abnormal GEH parameters was associated with a 6.4% left ventricular ejection fraction decline, a 24.2 gram/meter square increase in left ventricular mass index, a 10.3 milliliter/meter square increase in left ventricular end diastolic volume index, and a 7.8 milliliter/meter square increase in left ventricular end systolic index. All together, clinical and ECG parameters accounted for approximately one third of the left ventricular volume in 20% of the systolic function variability.

                                The associates were significantly stronger in patients with subclinical cardiovascular disease. The QRST integral increased by 20 millivolts/meter second for each three year period participants who demonstrated left ventricular dilatation at visit five. Sudden cardiac death victims demonstrated rapid GEH worsening, while those with left ventricular dysfunction demonstrated slow GEH worsening.

                                The authors concluded that GEH is a marker of subclinical abnormalities in cardiac structure and function.

                                In the next manuscript, Takumi Yamada and associates studied 19 patients with idiopathic ventricular arrhythmias, originating in the parietal band in 14 patients, in the septal band in 5 patients. Among 294 consecutive patients with right ventricular arrhythmia origins, parietal band and septal band ventricular arrhythmias exhibited a left bundle branch block, with left inferior in 12 patients', superior in 2 patients' axes, in left or right inferior axis pattern in four and one patients respectively.

                                In Lead 1, all parietal band ventricular arrhythmias exhibited R-waves, while septal band ventricular arrhythmias often exhibited S-waves. A QS pattern in lead AVR, in the presence of a knock in the mid QRS were common in all infundibular muscle ventricular arrhythmias. During infundibular muscle ventricular arrhythmias, a far-field ventricular electrogram, with an early activation, was always recorded in the His bundle region, regardless of the location of ventricular arrhythmia regions. With 9.2 radiofrequency applications in a duration of 972 seconds, catheter ablation was successful in 15 of the 19 patients. Ventricular arrhythmias recurred in four patients during a fallout period of 43 months.

                                In the next paper, Uma Mahesh Avula and associates examine the mechanisms underlying spontaneous atrial fibrillation, in an Ovine model of left atrial myocardial infarction. The left atrial myocardial infarction was created by ligating the atrial branch of the left anterior descending artery. ECG loop recorders were implanted to monitor atrial fibrillation episodes.

                                In seven sheep, Dantrolene, a Ryanodine receptor blocker, was administered in vivo, during the observation period. The left atrial myocardial infarction animals experienced numerous episodes of atrial fibrillation during the eight day monitoring period, that were suppressed by Dantrolene. Optical mapping showed spontaneous focal discharges originating through the ischemic/normal-zone border. These spontaneous focal discharges were calcium driven, rate dependent, and enhanced by isoproterenol, but suppressed by Dantrolene.

                                In addition, these spontaneous focal discharges initiated atrial fibrillation-maintaining reentrant rotors anchored by marked conduction delays at the ischemic/normal-zone border. Nitric oxide synthase one protein expression decreased in ischemic zone myocytes, or NADPA oxidase in xanthine oxidase enzyme activities in reactive oxygen species increased. Calmodulin aberrantly increased, Ryanodine binding to cardiac Ryanodine receptors in the ischemic zone. Dantrolene restored the physiologically binding of Calmodulin to the cardiac Ryanodine receptors.

                                The authors concluded that atrial ischemia causes spontaneous atrial fibrillation episodes in sheep, caused by spontaneous focal discharges that initiate re-entry. Nitroso redox imbalance in the ischemic zone is associated with intensive reactive oxygen species production, and altered the Ryanodine receptor responses to Calmodulin. Dantrolene administered normalize the Calmodulin response and prevents left atrial myocardial infarction, spontaneous focal discharges in atrial fibrillation initiation.

                                In the next study, Wouter van Everdingen and associates examine the use of QLV for achieving optimal acute hemodynamic response to CRT with a quadripolar left ventricular lead. 48 heart failure patients with left bundle branch block were studied. Mean ejection fraction 28%, mean QRS duration 176 milliseconds. Immediately after CRT implantation, invasive left ventricular pressure volume loops were recorded during biventricular pacing, with each separate electrode at four atrial ventricular delays.

                                Acute CRT response, measured as a change in stroke work compared to intrinsic conduction, was related to the intrinsic interval between the Q on the electrocardiogram and the left ventricular sensing delay, that is the QLV, normalized for the QRS duration, resulting in QLV over QRS duration in the electrode position.

                                QLV over QRS duration was 84% and variation between the four electrodes was 9%. The change in stroke work was 89% and varied by 39% between the electrodes. In univariate analysis, an anterolateral or lateral electrode position in a high QLV to QRS duration ratio had a significant association with a large change in stroke work, all P less than 0.01.

                                In a combined model, only QLV over QRS duration remained significantly associated with a change in stroke work, P less than 0.5. However, a direct relationship between QLV over QRS duration in stroke work was only seen in 24 patients, while 24 other patients had an inverse relation.

                                The authors concluded that a large variation in acute hemodynamic response indicates that the choice of stimulated electrode on the quadripolar electrode is important. Although QLV to QRS duration ratio was associated with acute hemodynamic response at a group level, it cannot be used to select the optimal electrode in the individual patient.

                                In the next study, Antonio Pani and associates conducted a multi-centered prospective study evaluating the determinance of zero-fluoroscopy ablation of supraventricular arrhythmias. They studied 430 patients with an indication for EP study and/or ablation of SVT. A procedure was defined as zero-fluoroscopy when no fluoroscopy was used. The total fluoroscopy time inversely was related to number of procedures previously performed by each operator since the study start. 289 procedures, or 67%, were zero-fluoro. Multi-variable analyses identified as predictors of zero-fluoro was the 30th procedure for each operator, as compared to procedures up to the ninth procedure, the type of arrhythmia, AVNRT having the highest probability of zero-fluoro, the operator, and the patient's age. Among operators, achievement of zero-fluoro varied from 0% to 100%, with 8 operators, or 23%, achieving zero-fluoro in 75% of their procedures. The probability of zero-fluoro increased by 2.8% as the patient's age decreased by one year. Acute procedural success was obtained in all cases.

                                The authors concluded that the use of 3D mapping completely avoided the use of fluoroscopy in most cases, with very low fluoro time in the remaining, and high safety and effectiveness profiles.

                                In the next paper, Demosthenes Katritsis and associates examine the role of slow pathway ablation from the septum as an alternative to right-sided ablation. Retrospectively, 1,342 undergoing right septal slow pathway ablation for AV nodal reentry were studied. Of these, 15 patients, 11 with typical and 4 with atypical AVNRT, had a left septal approach following unsuccessful right sided ablation, that is, the righted left group. In addition, 11 patients were subjected prospectively to a left septal only approach for slow pathway ablation, without previous right septal ablation, that is, left group. Fluoroscopy times in the right and left group, and the left groups were 30.5 minutes and 20 minutes respectively, P equals 0.6. The rate of [inaudible 00:18:24] current delivery time for comparable, 11.3 minutes and 10.0 minutes respectively.

                                There are no additional ablation lesions at other anatomical sites in either group, and no cases of AV block were encountered. Recurrence rate for arrhythmias in the right and left group was 6.7% and 0% in the left group, in the three months following ablation.

                                The authors concluded that the left septal anatomical ablation of the left inferior nodal extension is an alternative to ablation of both typical and atypical AV nodal reentry when ablation at the right posterior septum is ineffective.

                                In our next study, Mark Belkin and associates reported prior reports of new-onset device-detected atrial tachyarrhythmias. Despite the clear association between atrial fibrillation and the risk of thromboembolism, the clinical significance of new-onset device-detected atrial tachyarrhythmias and thromboembolism remains disputed.

                                The authors aim to determine the risk of thromboembolic events in these patients. Using the Ovid Medline, Cochrane, SCOPUS databases to identify 4,893 reports of randomized control trials, perspective or retrospective studies of pacemaker and defibrillator patients reporting the incidence of device detected atrial tachyarrhythmias.

                                The authors examine 28 studies, following a total of 24,984 patients. They had an average age of 69.9 years and a mean study duration of 21.8 months. New-onset device-detected atrial tachyarrhythmias was observed in 23% of patients. Among nine studies, consisting of 8,181 patients, reporting thromboembolism, the absolute incidence was 2.1%. Thromboembolic events were significantly greater among patients with new-onset device-detected arrhythmias, with a relative risk of 2.88, compared to those who had less than one minute of tachyarrhythmias, 1.77 risk ratio.

                                The authors concluded that new-onset device-detected atrial tachyarrhythmias is common, affecting close to one quarter of all patients with implanted pacemakers and defibrillators.

                                In our last paper, Sanghamitra Mohanty and associates performed a meta-analysis systematically evaluating the outcome of pulmonary vein isolation with and without thermoablation in patients with atrial fibrillation. For pulmonary vein ablation alone, only randomized trials conducted in the last three years reporting single procedure success rates, off antiarrhythmic drugs at 12 months or greater follow-up were included. In the PVI plus FIRM group, all public studies reporting a single procedure off antiarrhythmic drug success rate with at least one year follow-up were identified.

                                Meta-analytic estimates were derived, using the DerSimonian and Laird Random-effects Models, and pooled estimates of success rates. Statistical heterogeneity was assessed using the Cochran Q test and I-square. Study quality was assessed with the Newcastle-Ottawa Scale.

                                15 trials were included, 10 with PVI plus FIRM, with 511 patients, non-randomized perspective design, and 5 pulmonary vein isolation-only trials, consisting of 295 patients, all randomized.

                                All patients in the pulmonary vein only trials had 100% non paroxysmal atrial fibrillation, except for one study, and no prior ablations. About 24% of the PVI plus FIRM patients had paroxysmal atrial fibrillation.

                                After 15.9 months of follow-up, the off antiarrhythmic drug pooled success was 50% with FIRM plus PVI, compared to 58% in the PVI alone. The difference in the effect size between the groups was not statistically significant. No significant heterogeneity was observed in this meta-analysis.

                                The authors concluded that the overall pooled estimate did not show any therapeutic benefit of PVI FIRM over PVI alone.

                                That's it for this month, but keep listening. Suraj Kapa will be surfing all journals for the latest topics of interest in our field. Remember to download the podcast On The Beat. Take it away, Suraj.

Suraj Kapa:          Thank you, Paul, and welcome back to “On The Beat”. Again, my name is Suraj Kapa and I'm here to review with you articles across the cardiac electrophysiology literature that were particularly hard hitting in the month of February.

                                To start, we review the area of atrial fibrillation, focusing on anticoagulation. Reviewing an article published in this past month's issue of the Journal of the American Heart Association, by Steinberg et al., entitled Frequency and Outcomes of Reduced Dose Non-Vitamin K Antagonist Anticoagulants, results from ORBIT AF II. The ORBIT AF II registry, also called the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation, is a prospective national observational registry of AF patients.

                                The author sought to describe the frequency, appropriateness, and outcomes of patients prescribed reduced doses of NOACs in the community practice. They reviewed the records of almost 8,000 patients receiving NOACs and noted that the vast majority, nearly 84%, received a standard dose of NOACs, consistent with the U.S. FDA labeling. While only 16% received a reduced dose, only 43% of these were consistent with labeling instructions. Those who received reduced dose NOACs inappropriately more often tended to be younger and have, interestingly, lower overall bleeding risks scores.

                                Furthermore, compared with those appropriately receiving dosing, patients receiving inappropriately reduced dose NOACs had a higher unadjusted rates of thromboembolic events and death.

                                These data are important to understand, in that, discussion with patients, that inappropriate reduction of NOACs does not necessarily offer appropriate protection against long-term risk of thromboembolic events. Thus, close attention must be paid to consideration of the use cases and instructions for use.

                                While the registry cannot get into the details of why the dose was reduced in the spectrum of patients, it does highlight the fact that this continues to be a problem in general practice.

                                Further data is needed to understand what leads to inappropriate dose reduction, which could include factors such as patient preference, or physician education.

                                Staying within the realm of anticoagulation and understanding individual needs, we next review an article published in this past month's issue of Circulation, by Nielsen et al., entitled Female Sex Is a Risk Modifier Rather Than a Risk Factor for Stroke in Atrial Fibrillation. Should we use a CHA2DS2-VA score rather than CHA2DS2-VASc? In this review, the authors sought to evaluate whether female sex is truly an overall risk factor, as opposed to a risk modifier.

                                Using three nationwide registries, they identified patients with nonvalvular atrial fibrillation between 1997 and 2015, and they calculated two sets of scores. The first score, they termed a CHA2DS2-VA score, calculated for men and women with follow-up of one year in the Danish National Patient Registry. They wanted to calculate the risk based on this pseudo-value method. They then reviewed female sex as a prognostic factor by inclusion as an interaction term on the CHA2DS2-VA score, to calculate overall thromboembolic risk.

                                Amongst over 200,000 patients with atrial fibrillation, almost half of whom are women, they noted that the mean CHA2DS2-VA score, where sex is excluded, was a tad higher in women than men, namely 2.7 vs. 2.3. However, women had an overall higher one year thromboembolic rate of 7.3 vs. 5.7 per 100 person-years. Interestingly, with a CHA2DS2-VA score of zero, the absolute risk of thromboembolism was equal amongst men and women, around .5%. Once overall points increased above one, however, women exhibited a higher stroke risk. This interaction was statistically significant.

                                Thus, the authors indicated that female sex is a risk modifier for stroke in patients with atrial fibrillation, rather than a risk factor. The terminology is important to consider. Essentially, what they are noting is that at the lower risk level, fema

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