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ORIGINAL ARTICLES
Fragmented QRS complex in healthy adults: Prevalence, characteristics, mechanisms, and clinical implications
Ying Tian, Ying Zhang, Qian Yan, Jun Mao, Jianzeng Dong, Changsheng Ma, Xingpeng Liu
January-June 2017, 2(1):34-39
DOI:10.4103/2352-4197.208459  
Background: Fragmented QRS (fQRS) complex on a 12-lead electrocardiogram (ECG) is reportedly associated with myocardial scar or fibrosis in patients with structural heart disease. In healthy persons, however, the prevalence, underlying mechanisms, and clinical implications of fQRS remain unknown. Methods: In this prospective study, the routine 12-lead resting ECGs of 1500 consecutive healthy adults (707 male, age [38 ± 12] years) were independently screened for fQRS by two ECG readers. fQRS was defined as ≥1 additional deflection or notching within the QRS complex, including the peak of the R-wave or the nadir of S-wave, in at least two continuous leads. Results: fQRS was identified in 76 participants (5.1%) in a mean of (2.3 ± 0.7) leads, most commonly inferior leads (86.8%, 66/76), followed by precordial leads (13.2%, 10/76). Longer QRS duration and left deviation of the frontal QRS axis of ≤30° were identified as independent predictors of fQRS. In addition, fQRS in the precordial leads covered the QRS transition lead (from R/S <1 to R/S >1) in all ten participants. Sixteen healthy volunteers who were found to have fQRS underwent late gadolinium enhancement–cardiac magnetic resonance scanning, which revealed no myocardial fibrosis, scar, or other abnormalities. Conclusions: fQRS is not rare in healthy adults. The underlying mechanisms of fQRS in healthy adults seem to be mainly related to left axis deviation (especially deviations ≤30°), rather than myocardial scar or fibrosis.
  6 10,324 613
Implantation and Clinical Performance of an Entirely Leadless Cardiac Pacemaker
Chu-Pak Lau, Keping Chen, Kathy Lai-Fun Lee, Yan Dai, Shu Zhang
January-June 2016, 1(1):50-54
DOI:10.4103/2352-4197.191474  
Background: Entirely leadless pacemakers (LPMs) address limitations of conventional pacemakers that include complications related to the pacing leads, their connections, and pacemaker pockets. The aim of this study was to describe early implantation experience and clinical efficacy of LPM. Methods: A total of eight patients received an LPM (Micra™ Transcatheter Pacing System, Medtronic plc, Minneapolis, MN, USA). LPM was transvenously deployed using a 23 F sheath, and actively fixed by 4 nitinol tines. Results: On average, the patients were 74.3 ± 8.1 years, and 50% were female. All had indications for a ventricular demand (VVI) pacemaker, and ejection fraction was 66.4% ±7.4%. Except for one patient, all were implanted from the right femoral vein. The LPM was deployed either at the right ventricular apex (63%) or at the septum (37%). At implantation, pacing threshold at 0.24 ms was 0.69 ± 0.35 V, and R wave was 8.1 ± 2.9 mV. Successful pacing sites were reached at a median of 1 attempt (range 1–3), and the mean procedure and fluoroscopic times were 74 ± 19 min and 11.0 ± 5.8 min, respectively. 50% were on uninterrupted anticoagulation, and there were no acute complications including groin hematoma. Both pacing threshold and R wave improved at 1 month compared to acute implant value (0.46 ± 0.11 V and 14.5 ± 5.6 mV, respectively, P< 0.05 compared with implant). Between 1 and 3 months follow-up, there was no change in pacing or sensing threshold. The average percentage of ventricular pacing was 65% ± 26%. The intracardiac accelerometer was activated in 3/8 patients, and the satisfactory rate response profile during activity of daily living was achieved. Battery longevity was estimated to be more than 8 years in all patients. Conclusion This study documents excellent implantation success of the Micra™ LPM with stable pacing and sensing and satisfactory rate response profile.
  3 4,641 393
REVIEW ARTICLES
Magnetic resonance imaging-conditional devices: Where have we reached today?
Kamal K Sethi, Surendra K Chutani
January-June 2018, 3(1):16-24
DOI:10.4103/IJHR.IJHR_12_16  
Scientific growth in the field of magnetic resonance imaging (MRI) and cardiac devices has been exponential in recent decades. Cardiac implantable electronic devices due to their ferromagnetic constituents in leads and device body have always been an issue if patients need MRI. MRI is relatively safe. Recent introduction of changes in leads and device body constituents renders them less ferromagnetic, making MRI less frightening to a certain extent. Simultaneously, there is increasing research interest in MRI. Not only anatomy and pathology but also physiology of cardiac and nervous structures can be imaged. It is estimated that 53%–64% of intracardiac defibrillator (ICD) patients will require an MRI determination over a 10-year time horizon, highlighting the importance of MRI-conditional devices for this patient population. In this article, we briefly describe evolution and current status of conditioning of cardiac devices to make them MRI-friendly and briefly discuss where we are in terms of our physician role with respect to MRI-conditional devices.
  3 5,348 537
CASE REPORT
Clinical implications of real time implantable cardioverter-defibrillator high voltage lead short circuit detection
Roy Chung, Patricia D Garrett, Brian Wisnoskey, Mandeep Bhargava, Bruce L Wilkoff
January-June 2017, 2(1):49-51
DOI:10.4103/2352-4197.208454  
Implantable cardioverter-defibrillator lead failures are uncommon and predicting impending failure is challenging. We described a clinical case of a successful defibrillation despite initial detection of low high voltage impedance using Dynamic Tx algorithm, by withholding therapy if there is a short circuit and changing its shocking vector to an alternate one.
  2 2,850 412
ORIGINAL ARTICLES
Feasibility of an Elective Cardioversion Service Led by Advanced Practice Providers without Direct Cardiologist Supervision
Chad M House, Dennis W.X Zhu, Manish K Saha, Tarek S Hamieh, David G Benditt, William B Nelson
January-June 2016, 1(1):38-42
DOI:10.4103/2352-4197.191480  
Background: Elective direct current cardioversion (DCCV) has traditionally been performed by physicians in the United States. A few recent reports from the United Kingdom suggested that a specialist nurse-led service for elective DCCV of persistent atrial fibrillation was feasible. This practice has not been reported in the United States previously. Several years ago, we introduced a program where specially trained advanced practice providers (APPs) (physician assistants and nurse practitioners) assisted by an anesthesiology team, performed elective DCCV in patients with atrial fibrillation and atrial flutter, without direct cardiologist supervision. Methods: Upon receiving approval from the Institutional Review Board, we conducted a retrospective analysis of 447 consecutive DCCVs electively performed by APPs, for atrial fibrillation or atrial flutter, at Regions Hospital between 12/2006 and 10/2010. Transient deep sedation was administered by an anesthesiology team. The cohort was evaluated for procedural success and safety. Results: The procedural success rate was 92% (412/447). The incidence of procedural related adverse events, requiring immediate intervention, was 0.2% (1/447). This patient required emergent temporary pacing catheter insertion followed by a permanent pacemaker implantation at a later date. There were no other procedure-related complications and no thromboembolic events. A comparison with fifty elective cardioversions performed by cardiologists during the same period found no statistical difference in procedural success rates or complications. Conclusion: Under deep sedation administered by anesthesiology service, elective DCCV of atrial fibrillation and atrial flutter performed by well-trained APPs, without direct cardiologist supervision, is feasible and does not compromise patient safety.
  2 3,849 613
PERSPECTIVE
Risk Stratification of Sudden Cardiac Death: A Multi-racial Perspective
Dean M Abtahi, John Alvin Gayee Kpaeyeh, Michael R Gold
January-June 2016, 1(1):24-32
DOI:10.4103/2352-4197.191479  
Sudden cardiac death (SCD) is the leading cause of cardiovascular mortality and a major international health problem, with an estimated 3.7 million deaths occurring annually, accounting for approximately 15%–20% of all deaths worldwide. The implantable cardiac defibrillator (ICD) is an effective treatment of SCD and has had a major impact on outcomes. However, this therapy has been largely used in patients with left ventricular dysfunction. A changing epidemiology of SCD with fewer patients having marked reductions in left ventricular ejection fraction (LVEF) has renewed the focus on identifying other high risk populations. This article summarizes the current understanding of the diverse clinical, genetic, racial, electrocardiographic and imaging techniques available to detect patients most at risk. Despite many identified risk factors, no single predictor has been shown to have sufficient predictive value to be used to guide preventative therapy and reduce mortality. More recent effort has been directed towards combining markers to define a risk profile for identifying high risk cohorts.
  2 3,989 464
REVIEW ARTICLE
Radiotherapy and devices in cancer patients: What is new in clinical practice?
Fabiana Luca, Iris Parrini, Laura Cipolletta, Stefania Di Fusco, Carmelo Massimiliano Rao, Annamaria Iorio, Andrea Pozzi, Sandro Gelsomino, Domenico Gabrielli, Nadia Ingianni, Massimo Zecchin, Michele Massimo Gulizia
January-June 2019, 4(1):4-13
DOI:10.4103/IJHR.IJHR_2_19  
There has been a significant increase in cancer patients with implanted electronic devices which have been exposed to the risk of malfunction when undergoing radiotherapy in the last few years. In this review, we provide a short summary of radiotherapy principles, later analyzing in vitro and in vivo data and recent recommendations, in order to present the current evidence on predictive factors, risk stratification, and management of patients with implanted electronic devices requiring radiotherapy. The risk of device failure is usually transient, seldom permanent and mainly related to patients' characteristics and cumulative doses administrated during radiotherapy. The strongest predictive factors of implanted electronic device malfunction are higher radiation doses and higher beam energy. Indeed, energy <6 MV and a total dose of 2 Gy are recommended. A close multidisciplinary collaboration involving cardiac electrophysiologists, radiotherapists, and physicists may have important consequences in clinical practice, enabling then to minimize this risk.
  2 2,753 348
REVIEW ARTICLES
Evolution of left atrial appendage exclusion
Victor A Abrich, Dan Sorajja
January-June 2017, 2(1):22-28
DOI:10.4103/2352-4197.208457  
Atrial fibrillation is independently associated with an increased risk of thromboembolic stroke. While anticoagulants decrease this risk, they also carry a substantial risk of bleeding. Most left atrial thrombi arise from the left atrial appendage (LAA), which has led to several investigations into surgical and percutaneous methods of LAA exclusion for stroke reduction. The PubMed database was queried, and over 400 articles were considered for inclusion in this review. Of the surgical methods of LAA exclusion, complete excision is the most effective. Other methods, including ligation and stapling, may be incomplete and associated with left atrial thrombus formation. Surgical LAA exclusion has been commonly performed during mitral valve surgery although it has not been shown to prevent stroke in many retrospective studies. In patients unable to take warfarin, several percutaneous LAA exclusion devices have been studied, including the PLAATO system, Amplatzer Cardiac Plug (ACP), Watchman device, and Lariat. Both the ACP and Watchman have shown a significant stroke reduction and improved procedural safety with greater experience. The Lariat ligates the LAA using a combined endocardial and epicardial approach but is currently associated with substantial procedural risks. With better patient selection for the different options of LAA exclusion, thromboembolic stroke protection can be maximized with fewer complication risks.
  2 3,645 364
EDITORIAL
Rethinking Tilt Testing
Richard Sutton
January-June 2016, 1(1):2-4
DOI:10.4103/2352-4197.191478  
Tilt was used physiologically, 1930s–1970s, becoming a clinical diagnostic test for syncope in 1980s. Tilt has been criticized recently for failing to discriminate between reflex and more sinister syncope. Studies on possible benefit of pacing for older reflex syncope patients (2012–2014) yielded unexpected results. Patients with electrocardiogram implantable loop recorder (ILR) documented asystole and negative tilt, despite history strongly suggestive of reflex syncope, did well with pacing having syncope recurrence similar to that in paced His-Purkinje disease, while those with identical ILR findings and positive tilt did little better than those without pacing. These findings prompted explanation. The hypothesis hinged on tilt revealing a hypotensive/vasodepressor tendency rather than defining vasovagal syncope. Support was drawn from literature demonstrating good test sensitivity and specificity but no clinical value in arrhythmic, unexplained, or structural cardiovascular disease syncope. Further, in carotid sinus syndrome, another reflex syncope, the same pattern of disappointing pacing results was seen when tilt was positive but lack of syncope when tilt was negative. Thus, rethinking tilt testing is required to portray it in reflex, arrhythmic, unexplained, and cardiovascular syncope as having value in demonstrating risk of recurrence rather than being diagnostic. Its value in diagnosis of orthostatic hypotension (immediate/delayed), psychogenic pseudosyncope, and postural orthostatic tachycardia remains important and unchanged. The hypothesis has additional implications for management of hypertensive patients with syncope where medication may exacerbate symptoms requiring reduction/discontinuation. Tilt testing has greater value now than that claimed at its 1986 introduction.
  1 3,366 2,099
ORIGINAL ARTICLE
Analysis of 12-lead electrocardiogram signal based on deep learning
Yangxin Chen, Gang Du, Jiangting Mai, Wenhao Liu, Xiaoqiao Wang, Junxia You, Yuyang Chen, Yong Xie, Hai Hu, Shuxian Zhou, Jingfeng Wang
July-December 2018, 3(2):55-59
DOI:10.4103/IJHR.IJHR_4_18  
Background: In this work, a deep learning method is proposed to identify the types of arrhythmia. Methods: The 12-lead electrocardiogram signal is first denoised by filters to eliminate the baseline drift and the myoelectric interference. Then, the filtered signal is sliced into beats and sent to a deep neural network, which contains four convolutional layers, two gated recurrent unit layers, and one full-connected layer. Features in both the spatial domain and the time-frequency domain can be extracted implicitly by the deep neural network, instead of being extracted manually. Results: On the test split of the dataset, our neural network model achieves an accuracy of 98.15%. Among the accuracies for the four types of arrhythmia, respectively, the lowest one is 96% and the highest is 99%. Our model is must better than a baseline support vector machines classifier, with a test accuracy of 73.54%. Conclusion: The results give a supportive evidence to make our model clinically applicable to assist physicians in diagnosing certain diseases.
  1 3,667 401
ORIGINAL ARTICLES
Characteristics of dynamic electrocardiogram, heart rate variability, and electrophysiological study in a Chinese population with vasovagal syncope
Zhuzhi Wen, Chulian Fu, Yangxin Chen, Dengfeng Geng, Jingfeng Wang
January-June 2019, 4(1):26-33
DOI:10.4103/IJHR.IJHR_3_19  
Background: Little is known about characteristics of dynamic electrocardiogram (DCG), heart rate (HR) variability (HRV), and invasive electrophysiological study (EPS) in the presence, pattern, and stage of vasovagal syncope (VVS) during head-up tilt test (HUTT). The present study aims to explore predictive value of these tests for HUTT outcomes with underlying mechanisms. Subjects and Methods: This retrospective study consecutively enrolled 519 patients with VVS from January 2007 to December 2017. Parameters of DCG, HRV, and EPS were evaluated according to the presence, pattern, and stage of syncope during HUTT. Results: Mixed pattern was the predominant subtype of VVS, and vasodepressor patients had a positive response earlier than in cardioinhibitory patients. Compared with negative group, positive group with mixed and cardioinhibitory patterns had significantly slower maximal HR and mean HR all day, at daytime, nighttime, and each hour point. No significance was observed in parameters of HRV between negative and positive groups. There was no significant difference in HR, spectral power components, and time-domain variables among syncopal patterns and syncopal stages. Positive group had longer durations of A-H interval, sinus node recovery time, Wenckebach point, and Wenckebach 2:1 point than negative group. There was a significant difference only in sinus node recovery time among syncopal patterns as well as A-H interval among syncopal stages. Conclusion: DCG-derived HR and EPS properties rather than 24-h HRV may be used to predict positive responses, but they could not predict syncopal patterns and syncopal stages.
  1 2,107 279
Safety of continuing warfarin therapy in patients undergoing cardiac resynchronization therapy device implantation
Chad M House, Robert Gao, Imdad Ahmed, William B Nelson, Dennis W.X. Zhu
July-December 2017, 2(2):68-72
DOI:10.4103/IJHR.IJHR_5_17  
Background: Continuing warfarin therapy is considered safe for patient undergoing pacemaker or implantable cardioverter defibrillator procedures, but less evidence exists for patients undergoing cardiac resynchronization therapy (CRT) device implantation. Subjects and Methods: We retrospectively evaluated 136 consecutive patients who received a CRT device. Three periprocedural anticoagulation strategies were utilized: Group 1, continuation of therapeutic warfarin; Group 2, cessation of warfarin with heparin bridging; and Group 3, cessation of anticoagulation temporarily. Groups were compared on the incidence of complications. Results: Of the 136 patients, 87 (64%) were in Group 1, 18 (13%) were in Group 2, and 31 (23%) were in Group 3. Group 1 patients had an international normalized ratio of 2.3 ± 0.5, which was significantly higher than the other two groups. Coronary sinus dissection occurred in four patients: Three in Group 1 and one in Group 2, but no patient experienced pericardial effusion or tamponade. Group 2 experienced a higher incidence of pocket hematoma (P = 0.0065) and a longer length of hospital stay (P = 0.0069) than Group 1. Transient ischemic attack occurred in one patient in Group 3. Conclusion: Continuing warfarin with therapeutic international normalized ratio seems to be safe in individuals undergoing CRT device implantation.
  1 3,109 277
Rapamycin attenuates atrial fibrosis in 5/6 nephrectomized rats by inhibiting mammalian target of rapamycin and profibrotic signaling
Yajuan Yang, Mengqi Gong, Hongliang Li, Xue Liang, Zhiwei Zhang, Meng Yuan, Yue Zhang, Zhanquan Jiao, Gary Tse, Guangping Li, Tong Liu
July-December 2017, 2(2):81-85
DOI:10.4103/IJHR.IJHR_1_17  
Background: Atrial fibrosis plays a vital role in the pathogenesis of atrial fibrillation. However, the complex interplay between inflammation and remodeling remains incompletely understood. In this study, we examined the potential beneficial effects of the immunosuppressant rapamycin on reverse atrial remodeling in a 5/6 nephrectomized (5/6Nx) rat model of chronic kidney disease (CKD). Materials and Methods: Sprague-Dawley male rats were housed under controlled conditions with constant temperature and humidity for 1 week before the operation. They were assigned randomly to the following groups: (1) sham procedure with vehicle treatment, (2) 5/6Nx group with vehicle treatment, and (3) 5/6Nx with rapamycin treatment. The 5/6Nx group underwent nephrectomy by resection of the upper and lower thirds of the left kidney, followed by right nephrectomy. The rapamycin group received daily rapamycin (1 mg/kg/day) from the 4th week to the 8th after operation. Results: A significant increase in the protein expression levels of mammalian target of rapamycin (mTOR), p38, and extracellular signal-regulated kinase was observed in the 5/6Nx + vehicle group (1.56 ± 0.12 vs. 0.72 ± 0.06; 2.64 ± 0.40 vs. 1.20 ± 0.20; and 3.02 ± 0.71 vs. 1.42 ± 0.34; all P < 0.05), which were suppressed by rapamycin treatment (0.88 ± 0.08 vs. 1.56 ± 0.12; 1.96 ± 0.21 vs. 2.64 ± 0.40; and 1.87 ± 1.87 vs. 3.02 ± 0.71; all P < 0.05). Cardiomyocyte hypertrophy and extensive interstitial fibrosis of the atrium were observed in the 5/6Nx + VEH group (P < 0.05). These changes were attenuated in the 5/6Nx + rapamycin group (P < 0.05). Conclusions: In this 5/6Nx CKD rat model, atrial fibrosis was mediated via the mTOR pathway, which was attenuated by rapamycin.
  1 2,908 270
Effect of transcatheter closure of secundum atrial septal defect on cardiac electric remodeling
Shaimaa Ahmed Mostafa, Abdrabu Abdelhakim, Tarek Helmy Aboelazm, Osama Sanad Arafa, Ahmed M Elemam
January-June 2017, 2(1):40-48
DOI:10.4103/2352-4197.208453  
Purpose: This study aimed to investigate the intermediate- and short-term effects of transcatheter secundum atrial septal defect (ASD) closure on cardiac electric remodeling in children and adults. Methods: Fifty patients with secundum ASD referred for possible transcatheter device closure were subjected to history taking, proper physical examination, electrocardiographic assessment, and transthoracic echocardiographic examination and were evaluated before the ASD closure, 1 day, 3 months, and 6 months after closure. Results: During the 6-month follow-up, electrocardiographic parameters of remodeling were improved. P dispersion decreased from 49.73 ± 9.01 ms to 30.53 ± 5.08 ms (P = 0.004), QT dispersion decreased from 67.60 ± 5.31 to 51.13 ± 5.73 ms (P = 0.003), QRS duration decreased from 134.40 ± 4.97 ms to 116.20 ± 3.47 ms (P = 0.002), and PR interval decreased from 188.87 ± 6.06 ms to 168.00 ± 6.16 ms (P = 0.002). Electric remodeling was associated with remodeling of the cardiac chambers. At the end of follow-up, the right ventricular (RV) end-diastolic dimension decreased from 25.67 ± 5.50 mm to 17.80 ± 2.70 mm (P = 0.001) the left ventricular end-diastolic dimension increased from 33.17 ± 6.44 mm to 37.53 ± 5.15 mm (P = 0.002), mean pulmonary artery pressure decreased from 16.97 ± 3.37 mmHg to 9.22 ± 1.37 mmHg (P = 0.000), and RV systolic pressure decreased from 30.77 ± 4.69 mmHg to 18.8 ± 2.11 mmHg. After 6 months, 93.3% of the patients had normal RV size. Conclusion: Transcatheter ASD device closure leads to a significant improvement in the right-sided chambers' dimension and function and can reverse electrical changes in atrial and ventricular myocardium in children and adults after correcting hemodynamic status in short- and intermediate-term follow-up.
  1 4,188 383
REVIEW ARTICLES
Epsilon wave back in force
Guoliang Li, Ardan M Saguner, Guy Hugues Fontaine
July-December 2018, 3(2):49-54
DOI:10.4103/IJHR.IJHR_2_18  
Four decades of progress in understanding the electrogenesis, clinical value and recording methods of the epsilon wave have been achieved since it was first recognized in 1977. According to the new 2010 Task Force criteria, epsilon waves are a major criterion in the diagnosis of arrhythmogenic right ventricular dysplasia. Epsilon waves can be observed in the right precordial leads when a relevant intramyocardial conduction defect is present in the right ventricle. In this paper, we summarize the progress, challenge, and controversies in the definition of epsilon waves.
  1 3,442 362
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