Come and listen to the editor in chief to introduce the most authoritative international heart rhythm research results.
I am Peng-Sheng Chen, the editor-in-chief of Heart Rhythm. Thank you for listening to this podcast.
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The March 2018 issue of Heart Rhythm has a featured article entitled “Unrecognized venous injuries after cardiac implantable electronic device transvenous lead extraction” written by Tarakjin et al from the Cleveland Clinic. An author interview conducted by Dr Dan Morin can be found on the www.heartrhythmjournal.com website. The authors studied 461 patients who had a total of 861 leads extracted with a median lead age of over 2,500 days. Upon microscopic review, 80 leads (9.3% of leads) demonstrated segments of vein, the majority of which were transmural. Despite this finding, only five (1.1%) catastrophic complications occurred that required emergent surgical intervention. The authors conclude that Microscopic venous injuries during lead extraction are common but often not recognized clinically.
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The next paper is entitled “Revisiting anatomic macroreentrant tachycardia after AF ablation using ultrahigh-resolution mapping” by Takigawa et al from Bordeaux, France. The authors studied 88 anatomic macroreentrant atrial tachycardias from 57 patients. They define the practical isthmus as the easiest and most appropriate site for ablation in the circuit. The practical isthmus may be at a completely different location from the anatomic isthmus or a gap around the anatomic isthmus. The results showed that high-density mapping successfully identified the precise circuits and the practical isthmus of anatomic macroreentrant atrial tachycardias in patients with prior atrial fibrillation ablation.
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The next article is “Impaired cardiac autonomic regulation and long-term risk of atrial fibrillation in patients with coronary artery disease” by Nortamo et al from University of Oulu, Finland. The authors used heart rate variability as a marker of cardiac autonomic regulation in predicting new onset AF in coronary artery diseases. They studied over 1700 patients. Among them, 43 cases developed new-onset AF during a follow-up of 5.6 years. They found that impaired cardiac autonomic regulation measured by detrended fluctuation analysis and low-frequency and high-frequency ratio predicts the development of new-onset AF as well as or even better than left atrial diameter in patients with coronary artery diseases. This study suggests that abnormal autonomic nervous system may play an important role in the development of AF in patients with coronary artery diseases.
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The next article is “Time course and interrelationship of dysrhythmias in patients with surgically repaired atrial septal defect” by Houck et al from Rotterdam, The Netherlands. They studied 95 patients with surgically repaired ASD. They found sinus node diseases in 36%, complete AV block in 14%, AF in 49%, and SVT in 45% of the patients. All dysrhythmias presented most often after ASD repair, with a median duration of 12 years to 16 years between repair and onset. The authors conclude that a substantial number of dysrhythmias presented very late after ASD repair. The development of dysrhythmias was not related to redo procedures.
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The next article is “Renal function and risk of stroke and bleeding in patients undergoing catheter ablation for atrial fibrillation” by Yanagisawa et al, Nagoya, Japan. The objective of the study was to evaluate the safety and efficacy of periprocedural uninterrupted direct oral anticoagulant (DOAC) use compared with those of uninterrupted warfarin use in patients undergoing catheter ablation for AF stratified by various renal function groups. The authors studied over 2000 patients. They found that major and minor bleeding events primarily occurred in patients with CKD. Multivariate analysis showed that CKD was an independent predictor of adverse events. The authors conclude that the periprocedural bleeding risk was increased in patients with CKD. Uninterrupted DOAC and warfarin administration during catheter ablation for AF in patients with CKD is feasible and effective.
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The next article is “Impact of ventricular tachycardia ablation on health care utilization” by Winterfield et al from Medical University of South Carolina. The authors retrospectively studied the MarketScan databases and identified 523 patients who met the study inclusion criteria. After VT ablation, median annual cardiac rhythm-related medical expenditures decreased by $5,408. Moreover, the percentage of patients with at least 1 cardiac rhythm-related hospitalization and ER visit decreased significantly. In conclusion, this retrospective study demonstrated that catheter ablation seems to reduce hospitalization and overall health care utilization in VT patients with an ICD or CRT-D in place. The study is limited by the retrospective nature of the data collection and analyses.
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The next article is “Pulmonary vein isolation cryoablation for patients with persistent and long-standing persistent atrial fibrillation” by Tondo et al from University of Milan, Milan, Italy. The authors studied 486 patients with persistent AF and 52 with long-standing persistent AF in 35 Italian centers. Periprocedural complications were observed in 21 subjects (4.3%), and the acute PVI success rate was 97.6% across all patients. The AF event-free survival were 63.9% at 12 months and 51.5% at 18 months. The authors concluded that the PVI procedure was safe, effective, and efficient with regard to the treatment of patients with persistent and long-standing persistent AF. A limitation of the study is that follow-up evaluation was limited to symptoms, ECG and Holter every 3 months. More intensive arrhythmia monitoring may reduce the AF event-free survival.
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The next article is entitled “A novel algorithm increases the delivery of effective cardiac resynchronization therapy during atrial fibrillation: The CRTee randomized crossover trial” by Plummer et al from Freeman Hospital, Newcastle upon Tyne, United Kingdom. The eCRTAF, or the “EffectivCRT during AF” algorithm is designed to maximize percent LV capture while minimizing the increase in pacing rate. The results confirmed these predictions. This algorithm may represent a novel noninvasive method of significantly increasing effective CRT delivery during AF, potentially improving CRT response. A limitation of the study is the absence of data on actual CRT response rate. Whether or not this algorithm improves CRT response in patients with AF remains a topic for future investigation.
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The next paper is entitled “Detection of new atrial fibrillation in patients with cardiac implanted electronic devices and factors associated with transition to higher device-detected atrial fibrillation burden” by Boriani et al from University of Modena and Reggio Emilia, Modena, Italy. The authors performed a pooled analysis of data from 3 prospective studies to identify 6580 patients with no history of AF and no use of anticoagulants at baseline. The results showed that a new AF, with an AF burden of ≥5 minutes, was detected in 34% of patients during a follow-up period of 2.4 years. Among these patients, half transitioned to a higher AF-burden threshold during follow-up. The authors conclude that more than one-third of patients with no history of AF developed device-detected AF, with attainment of different thresholds of daily AF burden over time. This paper was accompanied by an editorial from Healy et al from Ontario, Canada. The authors pointed out that, although stroke has been the most extensively studied, newer evidence suggests that progression to longer episodes of subclinical AF may be an even stronger predictor of incident heart failure hospitalization.
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The next article is entitled “Implantable cardioverter–defibrillator therapy in hypertrophic cardiomyopathy” by Vamos et al from University Hospital Frankfurt, Frankfurt, Germany. They analyzed the patients enrolled in the SIMPLE trial. In patients with hypertrophic cardiomyopathy, outcomes were also compared between those randomized to defibrillation testing vs no defibrillating testing. The authors did not find any difference in intraoperative defibrillation efficacy, perioperative complications, and long-term outcomes between patients with hypertrophic cardiomyopathy and those with ischemic or dilated cardiomyopathy. Defibrillation testing did not improve intraoperative or clinical shock efficacy in hypertrophic cardiomyopathy patients. An editorial by Estes and Maron pointed out that the study is underpowered to detect a difference in outcomes of patients with hypertrophic cardiomyopathy with or without defibrillation threshold testing. The implanting physicians should not routinely omit defibrillation testing in patients with hypertrophic cardiomyopathy.
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The next article is entitled “Effects of angiotensin-neprilysin inhibition compared to angiotensin inhibition on ventricular arrhythmias in reduced ejection fraction patients under continuous remote monitoring of implantable defibrillator devices” by de Diego et al from Alicante, Spain. The authors prospectively included 120 patients with ICD with low ejection fraction. For 9 months, patients received 100% angiotensin inhibition ACE inhibitors or ARB. Subsequently, ACE inhibitors or ARB was changed to sacubitril-valsartan in all patients, who were followed for 9 months. They found that angiotensin-neprilysin inhibition significantly decreased ventricular arrhythmias and appropriate ICD shocks in reduced ejection fraction heart failure patients compared to angiotensin inhibition. An editorial by Ehrlich suggested that the impact of antiarrhythmic effects of sacubitril/valsartan on indications for the use of ICDs in primary prevention will need to be considered.
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The next article is “Beneficial effects of upgrading to His bundle pacing in chronically paced patients with left ventricular ejection fraction<50%” by Shan et al, the First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China. The purpose of this study was to assess clinical outcomes of upgrading to permanent His bundle pacing (pHBP) in patients with heart failure who underwent device upgrade from RV pacing or CRT nonresponse. They studied 16 patients including 11 with pacing-induced cardiomyopathy and 5 (31.2%) CRT nonresponders. At 1-year follow-up after pHBP, left ventricular end-diastolic dimensions decreased and LVEF increased from baseline. The authors conclude that in paced patients with clinically symptomatic heart failure and LVEF<50%, pHBP improved left ventricular function.
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The next paper is “Permanent His-bundle pacing as an alternative to biventricular pacing for cardiac resynchronization therapy: A multicenter experience” by Sharma et al from Rush University Medical Center, Chicago, Illinois. The purpose of this study was to assess the feasibility and outcomes of HBP in CRT eligible or failed patients. Results show that HBP was successful in 95 of 106 patients. During mean follow-up of 14 months, all patients demonstrated significant narrowing of QRS, increase in left ventricular ejection fraction and improvement in New York Heart Association functional class. The authors conclude that permanent HBP is a promising alternative for CRT. This paper, as well as the previous paper, adds to a growing body of literature showing the benefits of permanent His Bundle Pacing.
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The next paper is entitled “High-resolution mapping of the triangle of Koch: Spatial heterogeneity of fast pathway atrionodal connections” by Chua et al from University of Chicago. A total of 18 patients with symptomatic typical AVNRT referred for ablation underwent ultrahigh-density mapping. A median of 422 mapping points was acquired within the triangle of Koch during tachycardia. The most common site of earliest atrial activation within the triangle of Koch was anterior in 67%, Midseptal in 17% (n=3), and posteroseptal activation in 11%. One patient exhibited broad simultaneous activation of the entire triangle of Koch. Slow pathway potentials were not identified. These findings highlight the limitations of an anatomically based classification of AV nodal retrograde pathways.
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The next 3 papers are experimental papers. The first is “Accentuated vagal antagonism paradoxically increases ryanodine receptor calcium leak in long-term exercised Calsequestrin2 knockout mice” by Ho et al from Ohio State University, Columbus, Ohio. The authors subjected calsequestrin knockout mice to 8 weeks of treadmill exercise. Although 8-week treadmill running improved exercise capacity in these CPVT mice, the incidence and duration of ventricular tachycardia also increased. The peak amplitude of Ca2+ transient increased, whereas sarcoplasmic reticulum Ca2+ content decreased. The authors conclude that long-term exercise in calsequestrin knockout mice increases susceptibility to ventricular arrhythmias by accentuating vagal antagonism during β-adrenergic challenge, which prevents heart rate acceleration and exacerbates abnormal RyR2 Ca2+ leak.
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The next paper is “Beat-to-beat variations in activation-recovery interval derived from the right ventricular electrogram can monitor arrhythmic risk under anesthetic and awake conditions in the canine chronic atrioventricular block model” by Wijers (pronounce “Vai-er-sh”) et al, University Medical Center Utrecht, The Netherlands. The authors studied 30 anaesthetized dogs with complete AV block. Short term variability between LV and RV monophasic action potential duration was compared. The authors found that behavior of short term variability from the RV and LV is comparable. Short term variability of RV activation-recovery interval increases significantly before the occurrence of an arrhythmia in awake and anaesthetized conditions. The authors suggested that this finding can be integrated into devices to monitor arrhythmic risk. An editorial by Patil and Berger pointed out that developing an effective strategy in response to an imminent arrhythmia warning may be even more challenging than developing an accurate predictor of arrhythmia.
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The next paper is “Long-term intermittent high-amplitude subcutaneous nerve stimulation reduces sympathetic tone in ambulatory dogs” by Yuan et al from Indiana University, Indianapolis, Indiana. The investigators performed subcutaneous stimulation at two different thoracic sites in 8 dogs. They showed that subcutaneous stimulation led to stellate ganglion cell death, reduced stellate ganglion nerve activity, and suppressed PAT in ambulatory dogs.
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The next paper is “Permanent His bundle pacing: Recommendations from a Multicenter His Bundle Pacing Collaborative Working Group for standardization of definitions, implant measurements, and follow-up” by Vijayaraman et al from Geisinger Heart Institute, Pennsylvania. In this contemporary review the authors proposed to establish a uniform set of definitions encompassing the different forms of HBP as well as define a standardized approach to gathering data end points to ensure consistency in reported outcomes.
Of these articles above, three of them were about the permanent His bundle pacing. Basic science studies have shown that right ventricular pacing can cause calcium accumulation of the late activation sites in the left ventricle. Chronically elevated intracellular calcium could lead to remodeling and worsening of the left ventricular function. Permanent His bundle pacing has the theoretical advantage of synchronizing the activation and prevent left ventricular remodeling due to calcium accumulation. However, the long term benefits and risks of permanent His bundle pacing are still not well defined. It is time to perform prospective multicenter randomized clinical trials to compare the outcomes of permanent His bundle pacing versus RV pacing.
In addition to the above articles, the Journal also published a Josephson and Wellens ECG lesson, an Image of Localized reentrant atrial tachycardia with a very small circuit in very low voltage areas, four EP news and several letters to editors. In addition, we have published a list of remarkable reviewers who provided timely and high quality reviews. We want to thank all our reviewers for their input and guidance. I’m Dr. Peng-Sheng Chen for heart rhythm.
I'm the editor in chief of the heart rhythm magazine, Chen Pengsheng. Thank you for listening to the radio.