Erroneous electrocardiographic interpretations and its clinical implications.

INTRODUCTION: The advancement of artificial intelligence (AI) has aided clinicians in the interpretation of electrocardiograms (ECGs) serving as an essential tool to provide rapid triage and care. However, in some cases, AI can misinterpret an ECG and may mislead the interpreting physician. Therefore, we aimed to describe the rate of ECG misinterpretation and its potential clinical impact in patient's management. METHODS: We performed a retrospective descriptive analysis of misinterpreted ECGs and its clinical impact from May 28, 2020 to May 9, 2021. An electrophysiologist screened ECGs with confirmed diagnosis of atrial fibrillation (AF), sinus tachycardia (ST), sinus bradycardia (SB), intraventricular conduction delay (IVCD), and premature atrial contraction (PAC) that were performed in the emergency department. We then classified the misinterpreted ECGs as wrongly diagnosed AF, ST, SB, IVCD, or PAC into the correct diagnosis and reviewed the misinterpreted ECGs and medical records to evaluate inappropriate use of antiarrhythmic drugs (AAD), beta-blockers (BB), calcium channel blockers (CCB), anticoagulation, or resource utilization of cardiology and/or electrophysiology (EP) consultation. RESULTS: A total of 4969 ECGs were screened with diagnoses of AF (2282), IVCD (296), PAC (972), SB (895), and ST (638). Among these, 101 ECGs (2.0%) were misinterpreted. Wrongly diagnosed AF (58.4%) was the most common followed by wrongly diagnosed PAC (14.9%), wrongly diagnosed ST (12.9%), wrongly diagnosed IVCD (7.9%), and wrongly diagnosed SB (6.0%). Patients with misinterpreted ECGs were aged 76.6 ± 11.6 years with male (52.5%) predominance and hypertension being the most prevalent (83.2%) comorbid condition. The misinterpretation of ECGs led to the inappropriate use of BB (19.8%), CCB (5.0%), AAD therapy (7.9%), anticoagulation (6.9%) in patients with wrongly diagnosed AF, as well as inappropriate resource utilization including cardiology (41.6%) and EP (8.9%) consultations. CONCLUSIONS: Misinterpretation of ECGs may lead to inappropriate medical therapies and increased resource utilization. Therefore, it is essential to encourage physicians to carefully examine AI interpreted ECG's, especially those interpreted as having AF.

The Arrhythmogenicity of Sotalol and its Role in Heart Failure: A Literature Review.

ABSTRACT: According to the American Heart Association, approximately 6 million adults have been afflicted with heart failure in the United States in 2020 and are more likely to have sudden cardiac death accounting for approximately 50% of the cause of mortality. Sotalol is a nonselective ß-adrenergic receptor antagonist with class III antiarrhythmic properties that has been mostly used for atrial fibrillation treatment and suppressing recurrent ventricular tachyarrhythmias. The use of sotalol in patients with left ventricular dysfunction is not recommended by the American College of Cardiology or American Heart Association because studies are inconclusive with conflicting results regarding safety. This article aims to review the mechanism of action of sotalol, the ß-blocking effects on heart failure, and provide an overview of clinical trials on sotalol use and its effects in patients with heart failure. Small- and large-scale clinical trials have been controversial and inconclusive about the use of sotalol in heart failure. Sotalol has been shown to reduce defibrillation energy requirements and reduce shocks from implantable cardioverter-defibrillators. Torsades de Pointes is the most life-threatening arrhythmia that has been documented with sotalol use and occurs more commonly in women and heart failure patients. Thus far, mortality benefits have not been demonstrated with sotalol use and larger multicenter studies are required going forward.

A case report of deglutition triggered atrial fibrillation in a patient with Laing distal myopathy.

BACKGROUND: Deglutition-induced atrial fibrillation is a rare clinical entity with a reported prevalence of 0.6%. Laing distal myopathy is a rare autosomal dominant muscular dystrophy that is the result of mutations within the slow skeletal muscle fibre myosin heavy chain gene (MYH7). Atrial fibrillation has not been previously reported in patients with Laing distal myopathy. We describe the first reported case of deglutition triggered atrial fibrillation in a female with a history of Laing distal myopathy. CASE SUMMARY: A 44-year-old female with a history of Laing distal myopathy diagnosed at age 32, began experiencing intermittent episodes of pre-syncope and palpitations which occurred after deglutition with food. An ambulatory 30-day patient triggered event monitor recorded episodes of atrial fibrillation with rapid ventricular response. Family history was significant for Laing distal myopathy, atrial fibrillation, as well as sudden cardiac death. Laboratory data, transthoracic echocardiogram, cardiac magnetic resonance imaging, and an exercise treadmill SPECT Imaging stress test were normal. An oesophagram revealed a mild oesophageal dysmotility with no other abnormalities. She was started on flecainide 50 mg p.o. every 8 h and verapamil 40 mg p.o. every 8 h with no further episodes of atrial fibrillation. DISCUSSION: Given the strong genetic component of this myopathy, one could postulate as to a possible genetic component in the development of atrial fibrillation in our patient. Although we cannot make definite correlation between deglutition-induced atrial fibrillation and Laing myopathy, it is important to report this unusual association which has not been described before.

Do ICD diagnostics predict failure of ventricular tachycardia response to antitachycardia pacing and need for shock?

BACKGROUND: Among heart failure patients with implantable cardioverter defibrillators (ICDs), monomorphic ventricular tachycardia (MMVT) failing antitachycardia pacing (ATP) and terminated by shock renders higher mortality as compared to MMVT terminated by ATP only. It is unknown if the higher mortality in ATP failure reflects decompensated heart failure. OBJECTIVE: It was the purpose of the present study to determine if ICD heart failure diagnostics can predict the failure of ATP and the need to shock to terminate MMVT. METHODS: This was a single-center retrospective review of 103 consecutive patients with Medtronic ICDs who had MMVT and received ICD therapy. Heart failure diagnostics preceding each MMVT event were reviewed including atrial fibrillation burden, patient activity, night heart rate, heart rate variability, Optivol® fluid index, and MMVT heart rate. RESULTS: A total of 452 MMVT events were analyzed, of which 23% required shock. Compared to MMVT that responded to ATP, MMVT that failed ATP and required shock had significantly faster heart rates and higher atrial fibrillation burden. Patient activity, night heart rate, heart rate variability, and OptiVol® fluid index were similar between ATP responsive MMVT events and those that failed ATP. In a multivariate analysis adjusting for baseline characteristics, higher atrial fibrillation burden and lower patient activity were associated with ATP failure and shock termination. CONCLUSION: Device diagnostics associated with decompensated heart failure identified MMVT events that failed ATP and necessitated shock.

Systematic review and meta-analysis of catheter ablation of ventricular tachycardia in ischemic heart disease.

BACKGROUND: Patients with ischemic heart disease (IHD) are at risk for ventricular tachycardia (VT). Catheter ablation (CA) may reduce this risk. OBJECTIVE: To perform a systematic review and meta-analysis of randomized controlled trials (RCTs) of CA of VT in patients with IHD. METHODS: Literature searches of MEDLINE, the Cochrane Central Register of Controlled Trials (CENTRAL), and the Cochrane Database of Systematic Reviews (CDSR) were performed from January 2000 through April 2018 to identify RCTs comparing a strategy of CA vs no ablation in patients with IHD and an implantable cardioverter defibrillator (ICD). Outcomes of interest included appropriate ICD therapies, appropriate ICD shocks, VT storm, recurrent VT/ventricular fibrillation (VF), cardiac hospitalizations, and all-cause mortality. Using an inverse variance random-effects model, odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for each endpoint. RESULTS: A total of 5 RCTs (N = 635 patients) were included, with a duration of follow-up ranging from 6 months to 27.9 months. Patients who underwent CA experienced decreased odds of appropriate ICD therapies (OR 0.49; 95% CI 0.28-0.87), appropriate ICD shocks (OR 0.52; 95% CI 0.28-0.96), VT storm (OR 0.64; 95% CI 0.43-0.95), and cardiac hospitalization (OR 0.67; 95% CI 0.46-0.97) vs those who did not undergo ablation. There was no evidence of a benefit for recurrent VT/VF (OR 0.87; 95% CI 0.41-1.85), although this endpoint was not reported in all trials, or for all-cause mortality (OR 0.89; 95% CI 0.60-1.34). CONCLUSION: In this systematic review and meta-analysis of RCTs, CA was associated with a significant reduction in the odds of appropriate ICD therapies, appropriate ICD shocks, VT storm, and cardiac hospitalizations in patients with IHD.

Heart failure as a substrate and trigger for ventricular tachycardia.

Heart failure (HF) is a major cause of morbidity and mortality with more than 5.1 million individuals affected in the USA. Ventricular tachyarrhythmias (VAs) including ventricular tachycardia and ventricular fibrillation are common in patients with heart failure. The pathophysiology of these mechanisms as well as the contribution of heart failure to the genesis of these arrhythmias is complex and multifaceted. Myocardial hypertrophy and stretch with increased preload and afterload lead to shortening of the action potential at early repolarization and lengthening of the action potential at final repolarization which can result in re-entrant ventricular tachycardia. Myocardial fibrosis and scar can create the substrate for re-entrant ventricular tachycardia. Altered calcium handling in the failing heart can lead to the development of proarrhythmic early and delayed after depolarizations. Various medications used in the treatment of HF such as loop diuretics and angiotensin converting enzyme inhibitors have not demonstrated a reduction in sudden cardiac death (SCD); however, beta-blockers (BB) are effective in reducing mortality and SCD. Amongst patients who have HF with reduced ejection fraction, the angiotensin receptor-neprilysin inhibitor (sacubitril/valsartan) has been shown to reduce cardiovascular mortality, specifically by reducing SCD, as well as death due to worsening HF. Implantable cardioverter-defibrillator (ICD) implantation in HF patients reduces the risk of SCD; however, subsequent mortality is increased in those who receive ICD shocks. Prophylactic ICD implantation reduces death from arrhythmia but does not reduce overall mortality during the acute post-myocardial infarction (MI) period (less than 40 days), for those with reduced ejection fraction and impaired autonomic dysfunction. Furthermore, although death from arrhythmias is reduced, this is offset by an increase in the mortality from non-arrhythmic causes. This article provides a review of the aforementioned mechanisms of arrhythmogenesis in heart failure; the role and impact of HF therapy such as cardiac resynchronization therapy (CRT), including the role, if any, of CRT-P and CRT-D in preventing VAs; the utility of both non-invasive parameters as well as multiple implant-based parameters for telemonitoring in HF; and the effect of left ventricular assist device implantation on VAs.

ICD shocks in LVAD patients are not associated with increased subsequent mortality risk.

BACKGROUND: Implantable cardioverter-defibrillator (ICD) shocks are associated with increased mortality risk in heart failure patients. Whether ICD shocks are associated with mortality in continuous flow LVAD (CF-LVAD) patients is unknown. We studied the relationship of ICD shocks and ventricular arrhythmias (VAs) to morbidity and mortality in CF-LVAD-supported patients in our institution. METHODS: Single-center, retrospective study of prospectively collected ICD and LVAD databases. We analyzed data on VA which received ICD therapy in patients who underwent CF-LVAD implantation at Hartford Hospital between 2008 and 2018. RESULTS: A total of 157 patients were studied. During a median follow-up of 10 months (interquartile range 5-20 months), 48 patients (30.6%) experienced post-LVAD sustained VA. Thirty patients (19.1%) had appropriate shocks for VA and 5 patients (3.1%) had inappropriate shocks. Shocks for any arrhythmia were not associated with an increased risk of death (OR 0.836, 95% CI 0.224-3.115, p = 0.789). Neither post-LVAD VA nor the rate of VA was associated with an increased mortality risk (OR 0.662 [0.329-1.334], p = 0.248; OR 1.001 [0.989-1.014], p = 0.817, respectively). Cox multivariate regression analysis revealed pre-LVAD VA as a significant predictor of VA post LVAD implantation (OR 3.284 [1.584-6.808], p = 0.001). Symptoms with VA occurred in 22 (45.8%) patients, ranging from palpitations to near syncope/syncope. None of the variables including the rate of VA was associated with death or symptoms. CONCLUSIONS: VAs are common in CF-LVAD patients and occur with higher frequency in those with pre-LVAD VA and frequently cause symptoms. Neither VA nor ICD shocks are associated with mortality risk.

Clinical predictors of antitachycardia pacing response in implantable cardioverter defibrillator patients.

BACKGROUND: Antitachycardia pacing (ATP) provides safe and painless termination of reentrant ventricular arrhythmias in patients with implantable cardioverter defibrillator (ICDs), improving their quality of life. Established predictors of ATP responsiveness are not well known; only longer ventricular tachycardia (VT) cycle length and higher ejection fraction have been found to predict ATP success. OBJECTIVE: To investigate clinical and ECG predictors of ATP response in ICD patients with monomorphic VT. METHODS: The ICD clinic database was searched for monomorphic VT events requiring ICD therapy in patients with ischemic or non-ischemic cardiomyopathy. Each patient's first ICD encounter for VT was assessed. Patient demographics, clinical characteristics, VT rate, and ATP responsiveness (always, sometimes, and never successful) were recorded. An ECG was analyzed for QRS morphology and duration. Data was assessed for predictors of ATP responsiveness. RESULTS: In 527 patients, characteristics associated with always successful ATP included ACE-I/ARB therapy and slower VT rate (never successful ATP 197 ± 28 bpm, sometimes successful ATP 190 ± 27 bpm, always successful ATP 183 ± 22 bpm, P < .0001). Secondary prevention indication, amiodarone therapy, and longer QRS duration were associated with ATP failure. After multivariate analysis, only faster VT rate and amiodarone therapy were predictive of ATP failure. CONCLUSIONS: Neither QRS morphology nor duration was predictive of ATP success. Slower VT rate was predictive of repeated ATP responsiveness. Amiodarone therapy, which is known to increase VT cycle length, interestingly was associated with ATP failure for unclear reasons. More individualized and possibly more aggressive ATP programming may be warranted in patients on amiodarone.

Ventricular electrical delay as a predictor of arrhythmias in patients with cardiac resynchronization implantable cardioverter defibrillator.

BACKGROUND: Left ventricular (LV) remodeling and clinical response to cardiac resynchronization therapy (CRT) is inversely related to electrical dyssynchrony, measured as LV lead electrical delay (QLV). Presence of atrial or ventricular arrhythmia is correlated with worsening heart failure and LV remodeling. OBJECTIVE: We sought to assess the association of QLV with arrhythmic events in CRT recipients. METHODS: We identified patients implanted with a CRT device at our center. QLV interval was measured and corrected for baseline QRS (cQLV). We performed multivariable Logistic regression to assess the effect of cQLV on the occurrence of atrial/ventricular arrhythmic events. RESULTS: Sixty-nine patients were included in analyses. The cQLV was significantly shorter in patients with atria tachycardia/supraventricular tachycardia (AT/SVT) events compared to patients without AT/SVT events (43.4 ± 22% vs. 60.3 ± 26.7%, p = .006). In contrast, no significant difference in cQLV was observed between patients with and without ventricular tachycardia/fibrillation (VT/VF) events (46.2 ± 25.4% vs. 56 ± 25.7%, p = .13). cQLV was significantly shorter in patients with new onset AT/SVT events compared to those without (38.3 ± 22.2% vs. 55.7 ± 25.7%, p = .028). In contrast, no significant difference in cQLV was observed between patients with and without new onset VT/VF events (44.2 ± 25.2% vs. 56.3 ± 25.5%, p = .069). Following adjusted analyses, cQLV was a significant predictor of AT/SVT, but not for VT/VF. CONCLUSION: cQLV is a simple measure that can identify a vulnerable cohort of CRT patients at increased risk for atrial tachyarrhythmias, and hence can predict reverse remodeling and clinical response to CRT treatment.

Probable Hypocalcemia Induced Ventricular Fibrillation and Torsades de Pointes following Blood Product Administration.

A 35-year-old male underwent open-heart surgery and required multiple blood product transfusions. Citrate, a preservative in blood products, caused serum ionized calcium chelation leading to hypocalcemia, a prolonged corrected QT (QTc) interval, and separate episodes of ventricular fibrillation and torsades de pointes (TdP). This case highlights an uncommon complication of blood product transfusion-induced hypocalcemia with precipitant arrhythmia.

Role of Antiplatelet Therapy in Stroke Prevention in Patients With Atrial Fibrillation.

Patients with atrial fibrillation are at increased risk of having a cardioembolic stroke. The use of oral anticoagulation is now well established to prevent strokes in patients with atrial fibrillation and a CHA2DS2-VASc (congestive heart failure, hypertension, age ≥75 years [2 points], diabetes mellitus, prior stroke/transient ischemic attack or thromboembolism [2 points], vascular disease, age 65 to 74 years, and sex category) score of greater than 1, beyond sex. However, the role of antiplatelet therapy, specifically aspirin in low-risk patients or as an alternative to oral anticoagulation, remains controversial. The most recent US guidelines conflict with the European guidelines, which do not recommend antiplatelet monotherapy for stroke prevention irrespective of stroke risk. The aim of this review is to summarize published studies that question the role of aspirin in preventing strokes associated with atrial fibrillation. Overall, aspirin is found to play a limited role in the prevention of stroke in patients with atrial fibrillation and is associated with a similar risk of hemorrhagic events compared with anticoagulants. The benefit of dual antiplatelet therapy as an alternative to oral anticoagulation requires further study.

Ranolazine Therapy in Cardiac Arrhythmias.

Ranolazine is an antianginal medication originally granted approval by the U.S. Food and Drug Administration for therapeutic use in 2006. Since its introduction into the U.S. market, there have been multiple trials and clinical case reports that demonstrate ranolazine may be effective in the prevention and treatment of both atrial and ventricular arrhythmias, including postoperative atrial fibrillation following coronary artery bypass graft (CABG) surgery. More recently, the combination of dronedarone with ranolazine has demonstrated in initial studies to have a synergistic effect in the reduction of burden of atrial fibrillation. This article will review the basic pharmacology of ranolazine, the studies demonstrating use of ranolazine in atrial and ventricular arrhythmias, the limitations to the use of ranolazine as antiarrhythmic therapy, and explore the synergistic effect with other agents in the suppression of arrhythmias.

Vitamin K antagonist use: evidence of the difficulty of achieving and maintaining target INR range and subsequent consequences.

Vitamin K antagonists (VKAs) are effective oral anticoagulants that are titrated to a narrow therapeutic international normalized ratio (INR) range. We reviewed published literature assessing the impact of INR stability - getting into and staying in target INR range - on outcomes including thrombotic events, major bleeding, and treatment costs, as well as key factors that impact INR stability. A time in therapeutic range (TTR) of ≥65 % is commonly accepted as the definition of INR stability. In the real-world setting, this is seldom achieved with standard-of-care management, thus increasing the patients' risks of thrombotic or major bleeding events. There are many factors associated with poor INR control. Being treated in community settings, newly initiated on a VKA, younger in age, or nonadherent to therapy, as well as having polymorphisms of CYP2C9 or VKORC1, or multiple physical or mental co-morbid disease states have been associated with lower TTR. Clinical prediction tools are available, though they can only explain <10 % of the variance behind poor INR control. Clinicians caring for patients who require anticoagulation are encouraged to intensify diligence in INR management when using VKAs and to consider appropriate use of newer anticoagulants as a therapeutic option.

Late Gadolinium Enhancement in Patients with Nonischemic Dilated Cardiomyopathy.

One-third of all patients with heart failure have nonischemic dilated cardiomyopathy (NIDM). Five-year mortality from NIDM is as high as 20% with sudden cardiac death (SCD) as the cause in 30% of the deaths. Currently, the left ventricular ejection fraction (LVEF) is used as the main criteria to risk stratify patients requiring an implantable cardioverter defibrillator (ICD) to prevent SCD. However, LVEF does not necessarily reflect myocardial propensity for electrical instability leading to ventricular tachycardia (VT) or ventricular fibrillation (VF). Due to the differential risk in various subgroups of patients for arrhythmic death, it is important to identify appropriate patients for ICD implantation so that we can optimize healthcare resources and avoid the complications of ICDs in individuals who are unlikely to benefit. We performed a systematic search and review of clinical trials of NIDM and the use of ICDs and cardiac magnetic resonance imaging with late gadolinium enhancement (LGE) for risk stratification. LGE identifies patients with NIDM who are at high risk for SCD and enables optimized patient selection for ICD placement, while the absence of LGE may reduce the need for ICD implantation in patients with NIDM who are at low risk for future VF/VT or SCD.

An Adverse Electrophysiological Interaction Between an Implantable Cardioverter-Defibrillator and a Ventricular Assist Device.

Many patients with left ventricular assist devices (LVAD) have implantable cardioverter defibrillators (ICDs) as part of the management of advanced heart failure. With increasing use and coexistence of these devices in patients with advanced cardiomyopathy, adverse interactions between these devices have been recognized. We herewith describe a rare adverse interaction of electromagnetic interference (EMI) between a third-generation, continuous-flow device (The HeartWare HVAD) and an ICD which resulted in the delivery of inappropriate ICD therapies. A schematic approach for the prevention and treatment of electromagnetic interference has also been described.

PYREXIA-INDUCED BRUGADA PHENOCOPY.

Brugada syndrome (BS) is characterized by a typical electrocardiographic (ECG) pattern in the right precordial leads and a predisposition to develop ventricular arrhythmias. Mutations in a subunit of cardiac sodium channel (SCN5A) have been linked to BS. Experimental studies in the literature suggest that this dysfunction of the mutated channel can be temperature sensitive. Several antiarrhythmics have been used in the management of BS but Implantable Cardioverter Defibrillators (ICD) remains the only effective treatment. We herewith present the case report of a 62-year-old man who developed a type-2 Brugada ECG phenotype in a febrile state with complete resolution once the fever subsided.