Manage episode 185804584 series 1452724
Dr. Wang: Welcome to the monthly podcast On The Beat for Circulation, Arrhythmia and Electrophysiology. I'm 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.
This month's issue of Circulation: Arrhythmia and Electrophysiology has a number of fascinating and important articles. Let's start with the first article by Philip Halbfass and Associates, which describes the use of esophageal endoscopy in patients undergoing atrial fibrillation ablation. Of 1,802 patients undergoing afib ablation, 832 underwent post-procedural esophageal endoscopy. All patients were ablated using a single tip re-circular ablation catheter. Category one lesions described as erythema erosion were seen in 98 out of these 295 patients, while in 52 out of the 295 patients, ulceration was seen. In three of the 832 patients, esophageal perforation occurred, and in two of the 832 patients, atrial-esophageal fistula occurred.
Esophageal perforation only occurred in patients with category two lesions with an absolute risk of 9.6%. The authors concluded that post-ablation esophageal endoscopy is able to identify patients with high-risk lesions. One out of 10 patients with post-ablation esophageal ulcers progressed to perforation, while no patients without esophageal ulcers showed evidence of perforating complications.
In the next article by Christian Sohns and Associates describes the relationship between atrial fibrosis identified with magnetic resonance imaging and atrial rotor activity identified by noninvasive electrophysiological mapping. Ten patients underwent pulmonary vein isolation for persistent atrial fibrillation. Late gadolinium enhancement using magnetic resonance imaging, which projected onto the anatomy used for noninvasive electrophysiologic mapping.
The noninvasive electrophysiologic mapping identified 410 rotors evenly distributed between the left atrium and the right atrium. This study found that there was no statistically significant association between the presence of late gadolinium enhancement and the presence of rotors.
In the next article written by Jereon Venlet examines the endocardial unipolar voltage that best identifies abnormal epicardial electrograms. Thirty-three patients underwent endocardial epicardial right ventricular electro-anatomical mapping in ablation of right ventricular scar-related ventricular tachycardia. Eighty-six percent of abnormal epicardial electrograms had corresponding endocardial sites with bipolar electrogram less than 1.5 millivolts.
The remaining abnormal epicardial electrograms could be identified by endocardial unipolar voltages of less than 3.7 millivolts. The authors concluded that this use of endocardial unipolar voltage cut off at normal bipolar voltage sites improves the identification of all abnormal epicardial electrograms where there is less than 1 millimeter of fat.
The next article by Alan Bulava and Associates examines the outcomes of hybrid epicardial and endocardial radial frequency ablation, a persistent atrial fibrillation. Seventy patients underwent the epicardial thoracoscopic procedure followed by endocardial mapping ablation two to three months later. At the time of catheter ablation, 76% of patients were in sinus rhythm. All four pulmonary veins were found to be isolated in 69% of the patients and the left atrial posterior wall was isolated in 23% of the patients.
In the 12 months after the catheter ablation, 77% were arrhythmia-free, off antirrhythmic drugs. The majority of arrhythmia occurrences occur during the first 12 months following catheter ablation. Using previously ineffective antiarrythmics drugs and re-ablation procedures, arrhythmia-free survival increased to 97% during a mean followup of 936 days. Left atrial volume greater than 165 milliliters, the absence of sinus rhythm before catheter ablation and induce-ability of any sustained tachyarrhythmia at the end of catheter ablation predicted atrial fibrillation recurrence.
The authors concluded that the majority of patients after epicardial ablation required endocardial catheter ablation to complete the linear ablation or pulmonary vein isolation lesion sets. In the next article, Jason Roberts and Associates studied the clinical phenotype of Type 6 Long QT Syndrome, stemming from mutations in the KCNE2 encoded voltage gated channel beta subunit.
The authors examined individuals reported pathogenic KCNE2 mutations collected from inherited arrhythmia clinics in the Rochester LQTS registry as well as previously reported LQT6 cases identified through a med-line database search. Of 44 probands studied, 16 probands had resting QTC intervals and only developed QT prolongation and malignant arrhythmias following exposure to QT prolonging stressors. Ten had other Long QT pathogenic mutations and 10 did not have a Long QT phenotype, with the remaining eight subjects having a Long QT phenotype, but with evidence suggesting that the KCNE2 variant was not the underlying culprit.
The authors noted that the collective frequency of KCNE2 variance implicated in Long QT6 syndrome in the exome aggregation consortium database was 1.4%, in comparison with the 0.0005% estimated clinical prevalence of LQT6 syndrome. Thus, the authors concluded that based on clinical phenotype, the high allelic frequencies of LQT6 mutations in the exome consortium database, in absence of prior documentation of genotype phenotype segregation, many KCNE2 variants, and perhaps all have been erroneously designated as long QT syndrome causative mutations.
Instead, KCNE2 variants may confer pro-arrhythmic susceptibility when provoked by additional environmental acquired or genetic factors. In the next article, Alexander Quinn and Associates examine how mechanically-induced ectopy may cause ventricular fibrillation, the mechanism of commotio cordis. It is known that the block of stretched sensitive ATP inactivated potassium channels limits ventricular fibrillation occurrence in a porcine model of commotio cordis.
In isolated rabbit heart preparations using optical voltage mapping combined with pharmacological block of potassium ATP or stretch activated cation nonselective channels, the authors showed that the mechanical stimulation reliably triggers premature ventricular excitation at the contact site with induce-ability predicted by local tissue indentation. Mechanically-induced premature ventricular excitation induction is decreased by stretch activated cation nonselective channel block.
The authors also found that mechanically-induced premature ventricular excitation resulted in ventricular fibrillation only if the mechanical stimulation site overlaps the re-polarization wave edge in hearts where T-waves involve a well-defined re-polarization edge traversing the epicardium. This defines a narrow subject-specific vulnerable window for commotio cordis-induced ventricular fibrillation in both time and space.
In the next article Matthias Seidl and Associates examine the gene expression required for development of atrial fibrillation in a transgenic mouse model. Recent studies showed that atrial fibrillation susceptibility is associated with down regularization of target genes of the CREB/CREM family of transcription factors. CREB/CREM refers to cyclic and P-response element binding protein modulator.
Short CREM repressor isoforms like CREM-IbΔC-X bind to cyclical A&P responsive elements preventing transcriptional activation. Messenger RNA for CREM-IbΔC-X is up-regulated in atrial biopsies from patients with paroxysmal or chronic atrial fibrillation. The authors examined transgenic mice expressing CREM-IbΔC-X, which spontaneously developed atrial fibrillation proceeding to permanent fibrillation with age.
The authors found that the most prominent alterations of the gene program linked to CREM-induced atria modeling were identified in expression of genes related to structure, metabolism, contractility and electrical activity regulation. In the next article by Takumi Yamada and Associates electrophysiologic characteristics of the idiopathic ventricular arrhythmias originating from the parietal band, one of the muscle bands of the right ventricle, were examined.
Of 294 consecutive patients with right ventricular origins, 14 patients had ventricular arrhythmia origins in the parietal band. All patients have left bundle block pattern with 12 inferior and two superior axis. All patients had the notch in the middle of the curess in all cases. Seven patients had precordial transition before lead V3 and four patients had a slow curess onset.
Far field ventricular electrogram with an early activation was always recorded in His bundle region regardless of the location of the ventricular arrhythmia origin. During the catheter ablation, a mean number of 10.4 radio frequency of applications with a mean duration of 1,099 seconds were delivered. Catheter ablation was successful in 10 patients and ventricular arrhythmias recurred in four with a mean followup of 41 months.
In the Advances in Arrhythmia and Electrophysiology section, the Buza and Associates have reviewed cancer treatment-induced arrhythmias. The authors describe ECD advances in arrhythmias associated with individual cancer chemotherapeutic agents. Now here with a review of the highlights from the articles from journals throughout the world in the past month, is Dr. Suraj Kapa.
Dr. Kapa: Hello. Today we're going to be going over several hard hitting articles we have identified that seem to stand out in the electrophysiological literature from the month of July 2017. The first area we will be delving into is that of atrial fibrillation. Specifically related to cardiac mapping and ablation. The first article in this area that we've chosen was published by Samuel et al. in the Journal of Cardiovascular Electrophysiology entitled Catheter Ablation for the Treatment of Atrial Fibrillation Is Associated with a Reduction in Healthcare Resource Utilization.
Samuel et al. reviewed data from a large population base cohort in Quebec, Canada including over 1,500 patients undergoing cardiac ablation for atrial fibrillation. They demonstrated that healthcare resource utilization including hospitalizations, emergency room visits and cardioversions were significantly reduced both 12 months as well as 24 months after the next ablation. These findings seem to suggest that catheter ablation has a sustained overall impact on resource utilization amongst patients with atrial fibrillation.
While the study was not randomized and was a retrospective evaluation of outcomes, these findings are provocative. Certainly as we wait for the results of the Cabana trial in about one year we hope to see whether or not cardiac ablation carries the weight of potential beneficial impacts both in terms of long-term care as well as long-term outcomes. Of course being a retrospective evaluation, one question that lies with regards to these findings is whether or not the reduction in resource utilization might be a byproduct of improved ambulatory care of these patients or whether it's a byproduct of patients understanding their disease process better, and thus perhaps not seeking emergency room care or hospitalization as frequently.
The next publication we'll focus on was published by Anselmino et al. in The International Journal of Cardiology entitled Conduction Recovery Following Catheter Ablation in Patients with Recurrent Atrial Fibrillation and Heart Failure. This publication synergizes with several other publications that have come out in the month of July. Focusing on the publication by Anselmino et al., they reviewed retrospectively patients undergoing redo atrial fibrillation ablation in the setting of underlying heart failure.
What they demonstrated was that nearly a third of patients had no pulmonary vein reconnection, but tended to have more persistent forms of atrial fibrillation suggesting more extensive atrial substraights. This study is complimentary to a publication by [inaudible 00:15:23] et al., published in JACC EP. this past month where they evaluated the longterm outcomes of patients who, when presenting for redo atrial fibrillation ablation had persistent pulmonary vein isolation.
In that article, they found that nearly 17% of patients presenting for redo ablation had persistent pulmonary vein isolation. Moreover, these patients tended to perform significantly worse in terms of longterm outcomes than those who presented with PV reconnection, with about a 56% freedom from affiliate swipe after we do ablation in the setting of persistent pulmonary vein isolation as opposed to 76% when there was PV reconnection seen.
So the question becomes if we see this greater atrial substraight, should we automatically be doing more ablation? Of course as we all know, there have been many studies performed trying to tease out whether additional ablation in patients who might have more significant atrial substraight carries benefits. In this regard, Fink et al. in last month's edition of Circulation, Arrhythmia and Electrophysiology demonstrated that in fact as an index procedure of performing a stepwise concomitant café plus linear ablation on top of pulmonary vein isolation in persistent and long standing persistent atrial fibrillation patients did not necessarily confer an increased likelihood of longterm success over pulmonary vein isolation alone.
Thus, the jury continues to still be out as far as what the right strategy is in many of these patients. However, these studies highlight the importance of continued evaluation and understanding of how we can use information about atrial substraight to guide our ablation procedures more successfully. Changing gears, we'll move on the pathophysiology mechanisms of disease within atrial fibrillation.
The article we will choose to focus on here was published by Die et al. in The Journal of Cardiovascular Electrophysiology entitled The Effects of Extrinsic Cardiac Nerve Stimulation on Atrial Fibrillation Induce-ability: The Regulatory Role of the Spinal Cord. Over the course of the last several years many investigators have sought to show that modulation of the autonomic nervous system can successfully alter cardiac electrophysiology and provide antiarrythmic benefits.
However, when subject to prospective trials such as the recently published Defeat HF Trial, they have not necessarily found clear benefit. Thus, a critical question becomes how we translate our animal models into human treatment. The interesting results from Die et al. lie in the fact that they looked at the effects of spinal cord stimulation and spinal cord block in addition to concomitant stimulation of other centers such as the venous nerve, the stellate ganglion and ganglionated plexi.
They demonstrated that spinal cord stimulation enhanced the effects of venial nerve stimulation while attenuating the effects of stimulating the left stellate ganglion or ganglionated plexus. In turn, the combinations of these different levels of stimulation had different effects on affiliate swipe induce-ability, whether significantly increasing or decreasing the potential.
The reason this article is important is it highlights the extensive cross linking and synergy that exists within the autonomic nervous system and that attention paid to only a single center of autonomic innovation may not be sufficient for certain paradigms of care. This past month there were also two reviews summarizing the role of the autonomic nervous system and modulation of that nervous system and the treatment of arrhythmias.
The first was by Witt et al. and Europace. The other by Schwartz et al. in the International Journal of Cardiology. These articles help the reader understand the extensive crosslinking and cross communication that might occur, that might sometimes defeat our efforts to use a single element of the autonomic nervous system to modulate cardiac arrhythmias. Changing gears yet again, we'll move on to risk stratification and management for atrial fibrillation.
Perino et al. in last month's edition of The Journal of the American College of Cardiology published an article entitled Treating Specialty in Outcomes in Newly Diagnosed Atrial Fibrillation from the Treat AF Study. They present data based on a very large cohort of over 180,000 veterans regarding the effect of treating specialty on atrial fibrillation outcome. Interestingly they demonstrated that when a cardiologist was involved in the care of the patient, there was an overall decrease in stroke and mortality.
Albeit with a concomitant increase in hospitalization for AF. The stroke reduction seen was also seen to be secondary to better anticoagulation prescription within 90 days of diagnosis when those patients were seen by a cardiologist as compared with a general internist. This earlier prescription anticoagulation however did not mediate the mortality reduction. These data presented by a Perino et al. are provocative in this era of rising healthcare costs.
The question is, as atrial fibrillation rates rise, as the general population ages, how quickly and how aggressively we should engage specialty care early on in patient evaluation. The data by Perino et al. suggests that maybe this engagement should occur earlier. Part of the reasons for this might be improved understanding of current evidence regarding treatment of such patients or better systems of care that allow for providers to identify patients who might need alterations and care faster.
However, if anything this is hypothesis-generating. Why anticoagulation prescriptions are delayed when patients are not seen by a specialist or why there would be a difference in mortality are important factors to review further. In this past month Hernandez et al. in Stroke published an article discussing the large degree of geographic variation that exists with regards to appropriate anticoagulation prescription in patients with atrial fibrillation.
They demonstrated that there's extensive inhomogeneity across the United States in terms of how and in whom anticoagulation gets prescribed. Thus, how much of these outcomes are specialist-driven, geographically-driven or based on elements of access to care or other issues are going to be important features that have to be evaluated.
The next article in risk stratification was published by Mostofsky et al. in Heart, entitle Chocolate Intake and Risk of Clinically Apparent Atrial Fibrillation: The Danish Diet, Cancer and Heart Study. In this study they demonstrated in a population of over 55,000 patients that when accounting for as many variables as they could, higher chocolate intake, more than once per month, was associated with a decreased atrial fibrillation risk when compared with those consuming less chocolate than once per month.
Of course, they note that despite these attempts to account for multiple confounding variables, residuary confounders cannot be accounted for. The relevance of this article lies in the question of lifestyle choices patients are asked to make when thinking about how to either prevent themselves from having atrial fibrillation or trying to even treat their atrial fibrillation risk.
Chocolate has been shown to have multiple potential beneficial effects in multiple areas of cardiology, however, how to counsel patients with data like these becomes very difficult. The questions lies in how chocolate might mediate arrhythmia risk and how it might also modulate other potential risks such as weight gain or other factors.
Thus while important to consider this in light of patients often asking what they can and cannot have, it is important to further consider that we don't understand the full story. The other key element to understand is that really when they say that chocolate intake reduces risk of clinically apparent atrial fibrillation they are speaking about moderate chocolate intake and not necessarily having it for three meals a day.
Changing gears away from atrial fibrillation, we will next focus on the area of ICDs pacemakers and CRT. Aberi et al. in Nature's Scientific Reports published regarding inductively power wireless pacing via miniature pacemaker and remote stimulation control system. Their approach provides potential novel opportunities beyond currently available both lead-based and leadless pacemakers and improving battery and allowing for further miniaturization of such devices.
They noted by creating a very novel inductive power supply they're able to miniaturize the pacing components and also significantly reduce the power requirements. In fact, they suggested that they could create a leadless device that could be as small as being delivered out of the anterior ventricular vein. This is the first report of such an inductively powered miniaturized pacing system with low enough power consumption that may prove viable for ambulatory human use.
The desire to create improved pacing and fibrillation systems is further highlighted by an article published by [Kalu 00:25:41] et al. in JACC Clinical Electrophysiology this past month where they demonstrated initial results of percutaneous epicardially delivered partially insulated defibrillator lead. Work like these holds the potential to improve options for patients and in traditional vascular access is not desired, or an identifying new ways of delivering pacing therapy that exists outside the traditional lead base or even somewhat miniaturized leadless approaches.
We'll next focus on the area of sudden death and cardiac arrest. The first article we'll focus on was published by Stecker et al. in The Journal of The American Heart Association entitled Health Insurance Expansion and Incidence of Out of Hospital Cardiac Arrest: A Pilot Study in the US Metropolitan Community. This article looked at the results of The Affordable Care Act, mainly health insurance expansion, on the rate of out of hospital cardiac arrest in a large US metropolitan community of over 600,000 people.
They separately studied a middle aged population that might have been affected by healthcare expansion versus an older population, above 65, who would have had relatively stable insurance plans having been covered by Medicare both prior to and after this change in healthcare plans. They demonstrated that there was a significant decrease in overall out of hospital cardiac arrests amongst middle age people without any significant change amongst the more elderly Medicare population in the same time period.
The time period studied was relatively short, nearly less than a decade. Of course, whether there were other events that might have occurred to alter this risk such as improvements in care beyond the combination of availability and mandates plus carrying health insurance, it remains to be seen. However, the data is very suggestive. Further evaluation at the national level in varying communities however would be useful, as well as consideration of population level cost benefit analysis.
The next article published by Shen et al. in the New England Journal of Medicine entitled Declining Risk of Sudden Death in Heart Failure. They presented data across 40,000 patients from multiple clinical trials over two decades regarding the changing rates of sudden death amongst heart failure patients. Interestingly they noted there was an overall 44% reduction in sudden death rates across these trials over time dating from the 1990s to 2014.
In the earliest trials considered, the mortality rate within 90 days after randomization was as high as 2.4% while the most recent trials suggest that that rate is more like 1.0%. This profound decline was attributed to improved usage and prescription of medications early on in the heart failure course, which may modulate outcomes.
The relevance of these findings lies in trials that have been published recently and met analysis that we've discussed regarding utility of defibrillators in nonischemic cardiomyopathy or even ischemic cardiomyopathy. The recently published Danish study suggested that ICDs might not confer an equivalent mortality risk as what would have been expected years ago. However, this publication by Shen et al. is particularly provocative because it calls into question whether the same mortality benefit we anticipated from earlier heart failure trials should still be the rubric by which current defibrillator trials are powered.
Namely, if we consider that Danish saw the 25% difference in mortality, with a 44% overall reduction in sudden death seen in trials over time for heart failure, seeking a 25% reduction might be excessive. Thus, this highlights the need to potentially power trials for ICDs and the benefit of such ICDs better. This importance of better stratifying better heart failure patients for sudden death risk has been raised in multiple articles this month, including in a review by Holiday et al. in Circulation and in the series of reviews published in Volume 237 of The International Journal of Cardiology.
The last article we choose to focus on in the role of sudden death and cardiac arrest was published by Vehmeijer in Circulation: Arrhythmia and Electrophysiology entitled Prevention of Sudden Cardiac Death in Adults with Congenital Heart Disease: Do the Guidelines Fall Short? They reviewed outcomes amongst 26,000 adults with congenital heart disease in light of existing guidelines for risk prediction and prevention of sudden death.
They demonstrated that less than half of the patients with sudden cardiac death actually had a guideline basis recommendation for an ICD on the basis of either the 2014 consensus statement on arrhythmias or the 2015 European Society of Cardiology Guidelines. These findings are very provocative in suggesting that we don't really understand who requires treatment amongst adults with congenital heart disease.
With improved care paradigms, both with improvements in surgical outcomes as well as ambulatory care of these patients and recognition of need for interventions, arrhythmias are becoming a greater and greater problem amongst patients with adult congenital heart disease. However, large scale studies are limited in stratifying overall risk of arrhythmias. The risk is certainly present as many of these patients have ventricular scar often attributable to cardiac surgeries or have hemodynamic insults that may result in progressive fibrosis of the ventricles.
In addition, the basal abnormalities of cardiac formation itself may lend itself to a sudden increased risk of arrhythmias. Thus, the question remains as how to best risk stratify these patients in order to reduce these overall sudden death rates. Changing gears yet again, we'll focus on two articles within the realm of cellular electrophysiology. The first article was published by Cerrone et al. in Nature Communications entitled Plakophilin-2 is Required for Transcription of Genes that Control Calcium Cycling and Cardiac Rhythm.
They demonstrated that plakophilin-2, or PKP2, which is known to mediate arrhythmogenic right ventricular cardiomyopathy due to abnormalities in the desmosomes actually has other direct electrical effects independent of substraight effects that are seen. Specifically PKP2 plays a significant role in maintaining gene transcription for several genes that mediate normal electrophysiologic activity, such as the ryanodine receptor, calsequestrin and others.
They demonstrated that this reduced expression of other genes secondary to PKP2 absence or abnormality leads to increased isoproterenol or adrenaline-induced arrhythmias that in turn can be suppressed with Flecainide. These findings are provocative in the fact that they suggest that it is possible for patients to have abnormalities of genes such as PKP2 that result in electrical abnormalities independent of the structural abnormalities.
Furthermore, it suggests that manifestation of the disease such as catecholaminergic polymorphic ventricular tachycardia may be immediate upstream of typical channels associated with the disease. For example, if PKP2 reduces expression of the ryanodine receptor, this might result in manifestations similar to CPTB in some patients. Along the same lines, Hewitt et al. published in Science Advances regarding deregulated calcium cycling underlies the development of arrhythmia and heart disease due to mutant obscurin.
Obscurins are a relatively growing area of interest as these are cytoskeletal proteins that have be associated with both hypertrophic and dilated cardiomyopathy. Similar to the story we just told about PKP2 however, they demonstrated that obscurins, likely through circa 2 and pentameric phospholamban can cause abnormal calcium handling. In fact, they demonstrated that the principle phenotype associated with obscurin abnormalities is one of an electrical abnormality, namely frequent PVCs.
In turn, mechanical phenotypes such as cardiomyopathy result in the setting of chronic pathologic stress such as increased afterload, thus these findings demonstrate that genes such as obscurin or PKP2, which are commonly associated with structural or mechanical myopathic processes might have direct independent electrical effects. The story with obscurin raises further question into how this may apply to conditions of PVC-related cardiomyopathy or other such conditions.
The other key point about these two areas of interest lie in the fact that it is possible as these genetic abnormalities mediate not just direct substraight elements, but arrhythmogenesis via abnormal channel expression, whether in all patients presenting with such specific genetic abnormalities substraight-based ablation alone will result in reduction of arrhythmia tendency. Of course this remains to be seen and is primarily hypothesis-generating.
Next we'll focus on three articles within the area of genetic channelopathies. The first paper was published by Rohatgi et al. in The Journal of the American College of Cardiology entitled Contemporary Outcomes in Patients With Long QT Syndrome. In a large single center practice, they reviewed the results of over 600 patients predominantly affected by LQT1 or LQT2 and demonstrated that after initial evaluation along with treatment based on the individual, done at a highly skilled center, 92% of patients did not experience any breakthrough cardiac events over longterm followup.
It was noted however, that the incidence of breakthrough cardiovascular events over longterm followup were far more common in patients who were symptomatic prior to their first evaluation than asymptomatic. In other words, if you were symptomatic prior to your first evaluation, the likelihood of a breakthrough cardiovascular event over longterm followup was as high as 25%, but if you were asymptomatic it was as low as 2%.
These data suggest that our overall care of the Long QT patient is improving. However, it also supports that further improvements in care are needed as breakthrough cardiovascular events can continue to occur. It also highlights the importance of close followup of that symptomatic patient in the modern era.
The second article was published by Kannenkeril et al. in JAMA Cardiology entitled the Efficacy of Flecainide in the Treatment of Catecholaminergic Polymorphic Ventricular Tachycardia. Flecainide currently carries a class 2A indication according to both the 2015 ENC guidelines and 2013 HRS AHRA APHRS consensus statement for treatment of patients with CPVT who fail max dose beta blockers. A lot of this evaluation however, has been based on retrospective evaluations.
Kannenkeril reviewed in a prospective single blind placebo controlled crossover trial the effect of Flecainide on exercise associated arrhythmias in CPTV patients who were already on max tolerated beta blockers and had an ICD. Amongst the 14 patients included of whom 13 completed the study, they showed there was a significant reduction in median ventricular arrhythmia score during exercise and in fact there was complete suppression with Flecainide compared to the placebo of 85%.
These findings thus add to the existing literature in terms the potential incremental value of Flecainide in achieving adequate arrhythmia suppression when used in conjunction with maximal tolerated beta blockers. The last article within the realm of genetic channelopathies we'll focus on was published by Yang et al. in The Journal of Physiology entitled A Multi-Scale Computational Modeling Approach Predicts Mechanisms of Female Sex Risk in the Setting of Arousal-Induced Arrhythmias.
It is recognized that female gender can increase the risk of Torsades in the setting of both inherited and acquired prolonged QT syndromes. In a combination of experimental and computational approaches, Yang et al. demonstrated that hormone concentrations can partly mediate this risk, specifically as it relates to her-related mutations. They demonstrated testosterone and high progesterone levels provide a protective effect against Torsades. However, estrogen can enhance Torsadogenic potential, particularly in the setting sympathetic stress.
They also demonstrated the mechanism by which this likely occurs is due to interaction of estrogen with pore loop or intracavity binding site of the her channel. In fact, on top of this they demonstrated that combined treatment with both estrogen and Dofetilide can simultaneously blockade the pore channel of her. These findings are provocative and hypothesis-generating. In terms of potential future research to further clarify risk for patients, particularly as it may apply to menstruating females who might have varying levels of estrogen, especially when being treated with concomitant QT prolonging agents such as Defetilide.
Next we will focus on three articles within the realm of ventricular arrhythmias. The first article was published by Sapp et al. in JACC Clinical Electrophysiology entitled Real Time Localization of Ventricular Tachycardia Origin from the Twelve Lead Electrocardiogram. They presented a methodology for rapidly determining in real time the approximate origin of a ventricular tachycardia using the 12 lead during cardiac ablation.
In 38 patients they used a variety of methods that involved multiple linear regression learning methods and demonstrated that a patient-specific regression method using at least 10 training set pacing sites in the individual patient can provide a localization accuracy of the exit site for VT of as much as five millimeters. Furthermore, with additional pacing sites that accuracy could improve further.
These findings support the continued utility of the standard 12 lead ECG in localizing the exit site of ventricular tachycardia. Furthermore, it points out the importance of considering that the electrocardiogram can be patient-specific. By using multiple pacing sites, this helps an algorithm learn how a patient-specific heart exists in terms of its electrical propagation potential. Further informing based on a 12 lead of a specific VT approximately where it should be exiting from.
The next article we will focus on was published by Muser et al. in again, JACC Clinical Electrophysiology entitled Longterm Outcomes of Catheter Ablation of Electrical Storm in Nonischemic Dilated Cardiomyopathy COMpared with Ischemic Cardiomyopathy. The summary point to this article is in a single center, large volume group of patients including about 267 total, the longterm outcomes of VT recurrence or mortality was no different between nonischemic and ischemic patients.
This is important to note as most prospective studies and in fact retrospective studies of the role of ventricular tachycardia ablation have focused on ischemic patients where the substraight is relatively predicable. These findings highlight that ablation may provide a reasonably effective therapy irrespective of the cause of the myopathy. Finally, changing gears within the realm of ventricular arrhythmias, we'll focus on a translational article by Motloch et al. in JACC Basic to Translational Science entitled Increased Afterload Following Myocardial Infarction Promotes Conduction-Dependent Arrhythmias That Are Unmasked by Hypokalemia.
They studied the role of increased afterload after myocardial infarction in a listing arrhythmias in a porcine infarct model. They demonstrated that in the setting of increased afterload there was increased widespread interstitial fibrosis. Interestingly, pacing -induced arrhythmias induced by a rapid burst pacing were mediated by hypokalemia associated conduction abnormalities rather than repolarization abnormalities.
The reason these findings are potentially important lie in the fact that arrhythmias in the early stages after myocardial infarction, especially in a setting of increased afterload, might be considered to be secondary to either repolarization abnormalities or depolarization abnormalities. These findings suggest that in the setting of concomitant hypertension the primary problem really lies in hypokalemia associated conduction abnormalities.
Thus, treatments that impair cardiac excitability, for example, even sodium channel blockade, may similarly confer an increased risk of ventricular arrhythmias when in the presence of increased afterload and myocardial infarction. It also calls into question whether interventions such as antitachycardia pacing in patients with hypertension, in other words increased afterload, might be more prone to acceleration of the ventricular arrhythmias than patients who are relatively better managed as far as afterload.
Changing gears yet again, we will focus on EP relevant myopathies. [inaudible 00:44:19] et al. published in JACC Clinical Electrophysiology regarding use of the 12 lead electrocardiogram to localize regions of abnormal electron atomic substraight in arrhythmogenic ventricular cardiomyopathy. There were really two major articles in this regard that have been published both in the same month.
The other article was published by Andrews et al. in Circulation, Arrhythmia and Electrophysiology entitled Electrical and Structural Substraight of Arrhythmogenic Right Ventricular Cardiomyopathy Determined Using Noninvasive Electrocardiographic Imaging and Late Gadolinium Magnetic Resonance Imaging.
The relevance of both of these articles lies in their statements about the potential utility of noninvasive approaches essentially using electrocardiograms to determine the distribution of substraight in arrhythmogenic right ventricular cardiomyopathy. The article by [inaudible 00:45:16] et al. specifically focused on fractionation of the QRS. They showed that patients with evidence of fractionation in the QRS on a 12 lead ECG had more extensive substraight.
Furthermore, distribution of fractionation to specific leads such as inferior, anterior or basal superior leads, was 100% specific, but veritably sensitive for identifying substraight as it localizes to specific cardiac regions. In turn, the publication by Andrews et al. in Circulation, Arrhythmia and Electrophysiology reviewed how the addition of multiple leads by a noninvasive electrocardiographic imaging could be used to even more specifically hone in on the relevant substraights.
Their further benefit was in the suggestion that repolarization abnormalities in fact co-localized with origination sites for ventricular ectopy in these patients. In combination, these sites highlight the utility of simple, noninvasive methods of electrocardiographic imaging in identifying and defining the arrhythmogenic substraight in the NRVC.
The next article we will review was by Sommariva et al. in Nature's Scientific Reports published just this past month entitled MIR 320A as a Potential Novel Circulating Biomarker of Arrhythmogenic Cardiomyopathy. They did micro RNA analysis on 53 healthy controls, 21 idiopathic VT patients and 36 arrhythmogenic cardiomyopathy patients and demonstrated that the circulating micro RNA 320A was significantly higher in arrhythmogenic cardiomyopathy than in either other cohorts.
It is recognized that some patients with idiopathic VT, especially right ventricular [inaudible 00:47:09] VT might reflect a cohort that might have what we call "concealed ARVC." The question thus becomes how to define why a patient has a specific manifestation of disease because longterm outcomes, if there is some underlying ARVC might be worse if the ARVC is not recognized and if cure is assumed based on treatment of the initial presenting rhythm.
Thus identifying novel ways of defining the presence of a disease even in the absence of obvious structural abnormalities carries benefit in terms of suggestions on longterm followup. Complimentary to the previously discussed article on the role of PKP2 mutations on mediating electrical instability in the heart, the study by [inaudible 00:48:01] et al. does in fact suggest that there might be methods of distinguishing arrhythmogenic cardiomyopathy from whether it be controls or truly idiopathic ventricular tachycardia using a very specific circulating biomarker.
On a completely different route, we'll finish our podcast today with a discussion of Bruner et al. published in European Heart Journal entitled Alcohol Consumption, Sinus Tachycardia and Cardiac Arrhythmias at the Munich Oktoberfest: Results from the Munich Beer-Related Electrocardiogram Workup Study or Munich Brew.
Bruner et al. studied over 3,000 voluntary participants with a combination of breath alcohol concentration measurements and electrocardiographic recordings via smartphone throughout the Munich Oktoberfest. In addition, they sought to evaluate chronic alcohol consumption effects on arrhythmias in a separate cord of over 4,000 patients from the Cora S4 study. In the study regarding acute alcohol effects, they demonstrated that in line with increasing BAC, there was a greater occurrence of arrhythmias in particular sinus tachycardia in almost a third of patients.
What was even further interesting was that respiratory sinus arrhythmia over the course of higher BAC is from baseline was reduced in the setting of alcohol use. Similarly, with chronic alcohol consumption there was an apparent significant association with the occurrence of sinus tachycardia. The reason these findings are important is in their suggestive element that the effects of alcohol intake in terms of whether it be acute or chronic arrhythmogenesis might somewhat lie in their effects on the basal autonomic states. As demonstrated by the reduction in overall sinus arrhythmia.
These findings serve to further elucidate mechanisms by which alcohol may mediate arrhythmias in a large real world patient sample. Thank you for joining us on this edition of On The Beat. Tune in next month again for more articles that might be of interest to the general electrophysiologic community all summarized in a single location.
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