Patients with a high defibrillation threshold: Approaches to management.

Implantable cardioverter-defibrillators (ICDs) have revolutionized the prognosis for patients at elevated risk of ventricular tachyarrhythmias. For safety, defibrillation should be effective with a minimum of 10 J below the device's maximum energy. While modern ICDs rarely deliver ineffective shocks in primary prevention, the surge in managing severe heart failure patients has led to an increased number of patients with high defibrillation thresholds (DFTs). This article elucidates the potential causes of high DFT, including clinical factors, lead and device placement, the presence of a Left Ventricular Assist Device (LVAD), prolonged ventricular arrhythmias, shock vectors, waveform tilt, medications, and manufacturer-specific options. We also detail management strategies, highlighting alternative shock coil placements, practical recommendations, and case studies from our institution. Our management algorithm suggests addressing preventable causes, re-evaluating coil positions, considering non-invasive system modifications, upgrading to a higher-capacity device, and adding extra coil(s).

Natural increase in the efficiency of ablation of ventricular tachyarrhythmias using high-density mapping in patients with non-ischemic etiology.

OBJECTIVE: This research is aimed at evaluating the efficacy and safety of ablation of ventricular tachyarrhythmias using high-density mapping in patients with non-ischemic etiology. MATERIAL AND METHODS: This study analyzed 60 patients with ventricular tachyarrhythmias, using diagnostic tools like electrocardiography and MRI. Treatment involved epicardial ablation following the E. Sosa method, with efficacy evaluated through the SF-36 survey and MRI. Success rates were categorized, and post-treatment care included troponin monitoring and aspirin. Data was analyzed using Excel and Statistika 11.0. RESULTS: Of the 60 patients, 30 underwent surgery at the City Cardiological Center in Almaty and 30 patients were operated on at the National Research Cardiac Surgery Center in Astana. Prior to surgery, all patients underwent a standard clinical diagnostic examination followed by ablation of ventricular tachyarrhythmias using high-density mapping. After six and 12 months from the beginning of the study, all patients underwent a follow-up examination, with an assessment of the effectiveness of the above treatment. After 12 months, follow-up examination of patients showed good results. Left ventricular ejection fraction in patients after 12 months increased from 47 ± 2.4 to 58 ± 4.5%. The end-diastolic diameter of the left ventricle decreased from 61.2 ± 2.31 to 50.1 ± 1.9 mm. CONCLUSION: In summary, the study highlights the efficacy and safety of high-density mapping ablation in treating ventricular tachyarrhythmias, especially from the right ventricular outflow tract in patients with reduced left ventricular ejection fraction. The success rate of the procedure was 95%. This approach proves beneficial for patients unresponsive to antiarrhythmic therapy, enhancing both the quality of life and potentially reducing mortality in patients with ventricular arrhythmias.

Atypical Antiadrenergic Effect of Refralon as a Mechanism of High Antiarrhythmic Effectiveness.

We studied the effect of Refralon on the electrophysiological properties of the supraventricular myocardium against the background of adrenergic (epinephrine) influence in the zone of the pulmonary veins, the area where 50-90% of atrial arrhythmias is triggered. The experiments were carried out on isolated tissue preparations of Wistar rats. The multichannel microelectrode array technique was used to record action potentials simultaneously in the atrium and in the ostium and distal parts of the pulmonary veins. Epinephrine application (12-50 nM) led to depolarization of the resting potential and the conduction block in the distal part of the pulmonary veins. Refralon (30 µg/kg) restored the resting potential in the distal part of the pulmonary veins. Against the background of epinephrine, Refralon did not significantly change the duration of the action potential at 90% repolarization in comparison with control. At the same time, the comparison drug E-4031 against the background of epinephrine significantly increased the duration of action potential in the atrium and in the ostium of the pulmonary veins, and sotalol increased it only in the ostium. Neither E-4031, nor sotalol restored conduction in their distal part. Refralon has a biphasic effect under conditions of adrenergic stimulation: the fast component is responsible for stabilizing the resting potential in the pulmonary vein and reduces the dispersion of action potential duration in the atrium and pulmonary vein and is also quickly washed away, and the slow component is responsible for the increase of the action potential duration and is slowly washed away.

The role of trigger factors in the occurrence of appropriate ICD shocks and their clinical and prognostic implications.

BACKGROUND: The role of triggers in the occurrence of appropriate implantable cardioverter-defibrillator (ICD) shocks due to ventricular tachyarrhythmias is not well known. The aim of the study was to assess the prevalence of trigger factors in appropriate ICD shocks and to analyze their prognostic impact on clinical outcome. METHODS: A total of 710 consecutive patients of a prospective single-center ICD-registry who received a first appropriate ICD shock between 2000 and 9/2021 were analyzed. RESULTS: In 35% of ICD patients with first ICD shock, at least one of the following triggers was found: Ischemia (22%), Compliance (9%), Decompensation (38%), Stress (12%), Technical (5%), Electrolyte/endocrinological disorder (22%) and Medication side effects (4%). The trigger factors can be summarized under the acronym ICD-STEMi. The prospective application of the ICD-STEMi scheme increased the rate of identified triggers from 32% to 56% (p < .001). Patients with triggered first ICD shock had an increased 5-year mortality rate (50% vs. 38%, p < .001). Patients with triggers did not show different mortality outcomes or recurrent ICD shocks whether they received arrhythmia therapy or not. CONCLUSIONS: The evaluation of trigger factors after the occurrence of ICD shocks is mandatory and can be systematically evaluated using the acronym ICD-STEMi. Systematic evaluation of triggers using the ICD-STEMi scheme can identify triggers in about half of ICD patients with first appropriate ICD shock. Patients with triggered ICD shock have a 12% higher 5-year mortality rate.

Effect of sodium glucose cotransporter 2 inhibitors on atrial tachy-arrhythmia burden in patients with cardiac implantable electronic devices.

INTRODUCTION: Use of sodium glucose cotransporter 2 inhibitors (SGLT2i) was associated with a reduction in atrial fibrillation hospitalizations. Therefore, we aim to evaluate the effects of SGLT2i on atrial tachy-arrhythmias (ATA) in patients with cardiac implantable electronic devices (CIEDs). METHODS: All 13 888 consecutive patients implanted with a CIED in two tertiary medical centers were enrolled. Treatment with SGLT2i was assessed as a time dependent variable. The primary endpoint was the total number of ATA. Secondary endpoints included total number of ventricular tachy-arrhythmias (VTA), ATA and VTA, and death. All events were independently adjudicated blinded to the treatment. Multivariable propensity score modeling was performed. RESULTS: During a total follow-up of 24 442 patient years there were 62 725 ATA and 10 324 VTA events. Use of SGLT2i (N = 696) was independently associated with a significant 22% reduction in the risk of ATA (hazard ratio [HR] = 0.78 [95% confidence interval {CI} = 0.70-0.87]; p < .001); 22% reduction in the risk of ATA/VTA (HR = 0.78 [95% CI = 0.71-0.85]; p < .001); and with a 35% reduction in the risk of all-cause mortality (HR = 0.65 [95% CI = 0.45-0.92]; p = .015), but was not significantly associated with VTA risk (HR = 0.92 [95% CI = 0.80-1.06]; p = .26). SGLT2i were associated with a lower ATA burden in heart failure (HF) patients but not among diabetes patients (HF: HR = 0.68, 95% CI = 0.58-0.80, p < .001 vs. Diabetes: HR = 0.95, 95% CI = 0.86-1.05, p = .29; p < .001 for interaction between SGLT2i indication and ATA burden). CONCLUSION: Our real world findings suggest that in CIED HF patients, those with SGLT2i had a pronounced reduction in ATA burden and all-cause mortality when compared with those not on SGLT2i.

Incidence of atrial and ventricular arrhythmias in obese patients with heart failure with reduced ejection fraction treated with sacubitril/valsartan.

AIM: To compare clinical outcomes among patients with heart failure and reduced ejection fraction (HFrEF) according to body mass index (BMI) after initiating treatment with an angiotensin-receptor neprilysin inhibitor (ARNI). METHODS: We gathered data from 2016 to 2020 at the University Medical Center Mannheim; 208 consecutive patients were divided into two groups according to BMI (< 30 kg/m2 ; n = 116, ≥ 30 kg/m2 ; n = 92). Clinical outcomes, including mortality rate, all-cause hospitalizations and congestion, were systematically analysed. RESULTS: At the 12-month follow-up, the mortality rate was similar in both groups (7.9% in BMI < 30 kg/m2 vs. 5.6% in BMI ≥ 30 kg/m2 ; P = .76). All-cause hospitalization before ARNI treatment was comparable in both groups (63.8% in BMI < 30 kg/m2 vs. 57.6% in BMI ≥ 30 kg/m2 ; P = .69). After ARNI treatment, the hospitalization rate was also comparable in both groups at the 12-month follow-up (52.2% in BMI < 30 kg/m2 vs. 53.7% in BMI ≥ 30 kg/m2 ; P = .73). Obese patients experienced more congestion compared with non-obese patients at follow-up, without statistical significance (6.8% in BMI < 30 kg/m2 vs. 15.5% in BMI ≥ 30 kg/m2 ; P = .11). Median left ventricular ejection fraction (LVEF) improved in both groups, but significantly more in non-obese compared with obese patients at the 12-month follow-up (from 26% [3%-45%] [min.-max.] vs. 29% [10%-45%] [min.-max.] [P = .56] to 35.5% [15%-59%] [min.-max.] vs. 30% [13%-50%] [min.-max.] [P = .03], respectively). The incidence of atrial fibrillation (AF), non-sustained (ns) and sustained ventricular tachycardia (VT) and ventricular fibrillation (VF) was less in non-obese than in obese patients after initiation of sacubitril/valsartan at the 12-month follow-up (AF: 43.5% vs. 53.7%; P = .20; nsVT: 9.8% vs. 28.4%; P = .01; VT: 14.1% vs. 17.9%; P = .52; VF: 7.6% vs. 13.4%; P = .23). CONCLUSIONS: The incidence of congestion in obese patients was higher compared with non-obese patients. LVEF improved significantly more in non-obese compared with obese HFrEF patients. Furthermore, AF and the ventricular tachyarrhythmia rate were revealed more in obesity compared with those without obesity at the 12-month follow-up.

Evaluation of a standardized approach using optimized and contiguous RF applications for electrical isolation of the superior vena cava.

The superior vena cava (SVC) is well described as one of the most common non-pulmonary vein (PV)-triggers for atrial tachyarrhythmias (ATA). In our study we evaluated a standardized approach for electrical isolation of the SVC from the right atrium using a horseshoe-shaped lesion set with optimized and contiguous ostial RF lesions. The results are promising, demonstrating a very high rate of acute SVC isolation in a safe and time efficient manner (mostly less than 10 min).

Ibrutinib and Bruton's Tyrosine Kinase Inhibitors in Chronic Lymphocytic Leukemia: Focus on Atrial Fibrillation and Ventricular Tachyarrhythmias/Sudden Cardiac Death.

BACKGROUND: The natural history of chronic lymphocytic leukemia (CLL) was dramatically improved by the introduction of ibrutinib, a Bruton's tyrosine kinase (BTK) inhibitor. In this review, we aimed to summarize and critically evaluate the association between first- and second-generation BTK inhibitors and the risk of atrial fibrillation (AF) and ventricular arrhythmias (VA). SUMMARY: Since the first clinical experience, the development of AF was observed as the result of off-target effects that likely combined with patient's predisposing risk factors and concomitant cardiac morbidities. More recently, both ibrutinib dose reduction and arrhythmia management allowed long-term treatment, with positive effects on progression-free survival and reduced all-cause mortality as well. Second-generation BTK inhibitors, acalabrutinib, and zanubrutinib have been tested and validated in CLL. A lower occurrence of AF as compared with ibrutinib has been found, although AF has always been a secondary endpoint of all studies that probed these agents. KEY MESSAGES: For this reason, caution should be exercised before concluding that second-generation BTK inhibitors are safer than ibrutinib. Recent data on the effectiveness of ibrutinib over a follow-up of 8 years show a remarkable benefit on all-cause mortality, which is of great value also for interpreting the clinical impact of the few cases of VA and sudden cardiac death (SCD) reported for ibrutinib, independently of QT lengthening. Since a risk of VA and SCD has been recently reported also during treatment with second-generation BTK inhibitors, it appears that this risk, usually reaching its maximum size effect at long-term follow-up, likely denotes a class effect of BTK inhibitors.

Left Ventricular Hypertrophy and Ventricular Tachyarrhythmia: The Role of Biomarkers.

Left ventricular hypertrophy (LVH) refers to a complex rebuilding of the left ventricle that can gradually lead to serious complications-heart failure and life-threatening ventricular arrhythmias. LVH is defined as an increase in the size of the left ventricle (i.e., anatomically), therefore the basic diagnosis detecting the increase in the LV size is the domain of imaging methods such as echocardiography and cardiac magnetic resonance. However, to evaluate the functional status indicating the gradual deterioration of the left ventricular myocardium, additional methods are available approaching the complex process of hypertrophic remodeling. The novel molecular and genetic biomarkers provide insights on the underlying processes, representing a potential basis for targeted therapy. This review summarizes the spectrum of the main biomarkers employed in the LVH valuation.

Variable clinical severity in TANGO2 deficiency: Case series and literature review.

Biallelic pathogenic variants in the TANGO2 (transport and Golgi organization 2 homolog) gene have been identified as causing a rare metabolic disorder characterized by susceptibility to recurrent rhabdomyolysis, lactic acidosis, encephalopathy, and life-threatening tachyarrhythmias. Recently published reports suggest variable clinical severity and phenotypes. This study details five new patients from two families with biallelic pathogenic variants in the TANGO2 gene identified by whole exome sequencing and includes the largest number of affected individuals from a single family reported to date. We document significant intrafamilial variability and highlight that milder phenotypes may be underrecognized. We present biochemical and clinical data to help highlight the features that aid in consideration of this condition in the differential with disorders of fatty acid oxidation. We also present a comprehensive literature review summarizing the molecular, clinical, and biochemical findings for 92 individuals across 13 publications. Of the 27 pathogenic variants reported to date, the recurrent exons 3-9 deletion represents the most common variant seen in 42% of individuals with TANGO2 deficiency. Common clinical features seen in >70% of all individuals include acute metabolic crisis, rhabdomyolysis, neurologic abnormalities, developmental delay, and intellectual disability. Findings such as elevated creatine kinase, hypothyroidism, ketotic hypoglycemia, QT prolongation, or abnormalities of long-chain acylcarnitines and urine dicarboxylic acids should raise clinical suspicion for this life-threatening condition.

Early Atrial Tachyarrhythmia Recurrence Predicts Late Atrial Tachyarrhythmia Recurrence After the Cryo-Maze Procedure　- An Observational Study.

BACKGROUND: It is unknown whether early atrial tachyarrhythmia (ATA) recurrence occurring within 3 months after the Maze procedure predicts late ATA recurrence.Methods and Results: This study involved 610 patients who underwent the modified Cryo-Maze procedure in conjunction with other cardiac surgery. The primary outcomes were late ATA recurrence, defined as occurring ≥3 months after surgery. The effects of early ATA recurrence on late ATA recurrence were analyzed using a Cox proportional hazards model. The following 11 covariates were considered explanatory variables: early ATA recurrence, age, sex, body surface area, preoperative duration of atrial fibrillation, preoperative left atrial diameter, and concomitant surgery (mitral valve replacement, mitral valve repair, aortic valve replacement, tricuspid annuloplasty, and left atrial appendage closure). Statistical analyses were performed with a 2-sided 5% significance level. Early ATA recurrence occurred in 174 patients (28.5%). Late ATA recurrence occurred in 167 patients (27.5%), with 595 events identified in these patients. The Cox proportional hazards model showed that early ATA recurrence was an independent predictor of late ATA recurrence (hazard ratio, 4.14; 95% confidence interval, 3.00-5.70; P<0.001)Conclusions: Early ATA recurrence was an independent predictor of late ATA recurrence among patients undergoing the modified Cryo-Maze procedure. The blanking period might not be applied to patients undergoing the modified Cryo-Maze procedure.

Validation of the national Danish ablation database: a retrospective, registry-based validation study.

Aim.To validate the National Danish Ablation Database (NDAD) by investigating to what extent data in NDAD correspond to medical records.Type of study. Non-blinded, registry-based, retrospective, validation study. Material and methods. A sample of patients who underwent ablation for atrial fibrillation in Denmark between 1 January 2016 and 31 December 2016 were included. By utilizing medical records as gold standard, positive predictive (PPV) and negative predictive values (NPV) for NDAD were assessed and presented as five main categories: arrhythmia characteristics, demographics, cardiac history, complications, and medication. PPV's and NPV's exceeding 90% were considered as high agreement. Results. 597 patients (71.0% males) were included in the study. Median age was 63.1 (IQR: 54.9-68.4) years. The median PPV and NPV estimates across all variables were respectively 90.4% (95% CI: 68%-95.2%) (PPV) and 99.4% (95% CI: 98.4%-99.8%) (NPV) at baseline, and 91.7% (95% CI: 67.4%-95.4%) (PPV) and 99.3% (98.2%-99.3%) (NPV) at follow-up. Conclusion. The data registered in NDAD agrees to a great extent with the patients' medical records, suggesting NDAD is a database with high validity. As a result of low complication rate, the PPV- and NPV-estimates among complication variables were prone to somewhat greater uncertainty compared to the rest.

Clinical outcome of out-of-hospital vs. in-hospital cardiac arrest survivors presenting with ventricular tachyarrhythmias.

Limited data regarding the prognostic impact of ventricular tachyarrhythmias related to out-of-hospital (OHCA) compared to in-hospital cardiac arrest (IHCA) is available. A large retrospective single-center observational registry with all patients admitted due to ventricular tachyarrhythmias was used including all consecutive patients with ventricular tachycardia (VT) and fibrillation (VF) on admission from 2002 to 2016. Survivors discharged after OHCA were compared to those after IHCA using multivariable Cox regression models and propensity-score matching for evaluation of the primary endpoint of long-term all-cause mortality at 2.5 years. Secondary endpoints were all-cause mortality at 6 months and cardiac rehospitalization at 2.5 years. From 2.422 consecutive patients with ventricular tachyarrhythmias, a total of 524 patients survived cardiac arrest and were discharged from hospital (OHCA 62%; IHCA 38%). In about 50% of all cases, acute myocardial infarction was the underlying disease leading to ventricular tachyarrhythmias with consecutive aborted cardiac arrest. Survivors of IHCA were associated with increased long-term all-cause mortality compared to OHCA even after multivariable adjustment (28% vs. 16%; log rank p = 0.001; HR 1.623; 95% CI 1.002-2.629; p = 0.049) and after propensity-score matching (28% vs. 19%; log rank p = 0.045). Rates of cardiac rehospitalization rates at 2.5 years were equally distributed between OHCA and IHCA survivors. In patients presenting with ventricular tachyarrhythmias, survivors of IHCA were associated with increased risk for all-cause mortality at 2.5 years compared to OHCA survivors.

Arrhythmias and electrocardiographic findings in Coronavirus disease 2019: A systematic review and meta-analysis.

BACKGROUND: Coronavirus disease 2019 (COVID-19) primarily causes lung infection, but recent studies have shown that cardiac involvement is associated with a worse prognosis. OBJECTIVES: We conducted a systematic review and meta-analysis to examine the prevalence of cardiac arrhythmias detected by the electrocardiogram and their relationships with adverse outcomes in patients with COVID-19. METHODS: PubMed and Google were searched for studies that reported on cardiac arrhythmias and/or examined the relationship between arrhythmias and adverse outcomes. RESULTS: Thirty studies with 12,713 participants were included in the systematic review, and 28 studies (n = 12,499) in the meta-analysis. The mean age was 61.3 ± 16.8 years; 39.3% were female. In 25 studies with 7578 patients, the overall prevalence of cardiac arrhythmias was 10.3% (95% confidence interval [CI]: 8.4%-12.3%). The most common arrhythmias documented during hospitalization were supraventricular arrhythmias (6.2%, 95% CI: 4.4%-8.1%) followed by ventricular arrhythmias (2.5%, 95% CI: 1.8%-3.1%). The incidence of cardiac arrhythmias was higher among critically ill patients (relative risk [RR]: 12.1, 95% CI: 8.5-17.3) and among non-survivors (RR: 3.8, 95%, CI: 1.7-8.7). Eight studies reported changes in the QT interval. The prevalence of QTc > 500 ms was 12.3% (95% CI: 6.9%-17.8%). ST-segment deviation was reported in eight studies, with a pooled estimate of 8.7% (95% CI: 7.3% to 10.0%). CONCLUSION: Our meta-analysis showed that QTc prolongation, ST-segment deviation, and various other cardiac arrhythmias were observed in patients hospitalized with COVID-19. The presence of cardiac arrhythmias was associated with a worse prognosis.

Meta-analysis of catheter ablation in patients with post-infarct cardiomyopathy undergoing defibrillator implantation.

BACKGROUND: Patients with post-infarct cardiomyopathy and ventricular arrhythmias (VT) necessitating implantable cardioverter defibrillators (ICD) are at risk of recurrent shocks with increased morbidity. METHODS: A comprehensive search of electronic databases for all randomized clinical trials that evaluated the role of catheter ablation as a preventive strategy at the time of secondary prevention ICD implantation was performed. We calculated hazard ratios (HR) and 95% confidence intervals (CI) using random-effects model. RESULTS: Four trials were identified with a total of 505 patients (average age 66.4 ± 9.0 years; 87.7% were male). Preventive ablation was associated with a significant reduction in appropriate device therapies (shocks and/or anti-tachycardia therapy) (HR = 0.62; 95% CI = 0.46-0.82; P < .01), sustained VT (HR = 0.74; 95% CI = 0.55-0.99; P = .04) compared to control. There were no differences in inappropriate device shocks (HR = 0.80; 95% CI = 0.38-1.71), all-cause death (HR = 0.93; 95% CI = 0.53-1.64), cardiac death (HR = 0.63; 95% CI = 0.29-1.36), arrhythmic death (HR = 0.26; 95% CI = 0.05-1.31), or cardiac hospitalization (HR = 0.79; 95% CI = 0.57-1.11) between strategies. Preventive ablation was associated with improved SF-36 physical component (mean difference = 2.81; 95% CI-0.53-5.10; P = .02), but not the mental component (mean difference = 1.30; 95% CI = -2.06-4.66). CONCLUSION: Among patients with post-infarct cardiomyopathy and VT, preventive catheter ablation at the time of ICD implantation is associated with a significant reduction of appropriate ICD therapy and sustained VT, and improvement in the physical component of quality-of-life, but no reduction in mortality.

Impact of Sustained Cardiac Tachyarrhythmias Recorded in Coronary Intensive Care Unit on Short- and Long-Term Mortality and Duration of Hospitalization.

BACKGROUND: Studies conducted in coronary intensive care units (CICUs) have demonstrated that tachyarrhythmias are associated with increased mortality after acute coronary syndromes (ACSs). However, the data for tachyarrhythmias occurred in CICUs due to a variety of cardiovascular disorders are limited. METHODS: We conducted a single-center prospective observational study, which included consecutive CICU patients (January 1, 2014 to May 31, 2018). We recorded the ventricular arrhythmias (VAs), supraventricular tachycardias (SVTs), and days of CICU hospitalization. The patients were followed up for 6 months after CICU discharge. RESULTS: A total of 943 patients (age: 66.37 ±15.4 years; 673 males [71.4%]) were included. Patients with tachyarrhythmias had higher in-CICU mortality (8.0% vs 4.1%, P = .029, odds ratio [OR]: 2.04, 95% confidence interval [CI]: 1.08-3.86) and higher 6-month all-cause mortality (12.8% vs 6.1%, P = .002, OR: 2.27, 95% CI: 1.35-3.83) than those who did not develop tachyarrhythmias. Ventricular arrhythmias was significantly associated with higher all-cause mortality than no tachyarrhythmia (15.4% vs 6.1%; P = .001) or SVTs (15.4% vs 7.0%; P = .001). The mean duration of hospitalization for the patients with tachyarrhythmias was 3.89 ± 4.90 days, while for the patients without was 2.79 ± 3.31 days (P < .001). Patients without ACS had higher short- and long-term mortality compared to patients with ACS (9.2% vs 2.9%, P < .001 and 12.9% vs 4.9%, P < .001). CONCLUSIONS: Tachyarrhythmias were associated with prolonged CICU hospitalization, while non-ACS cardiovascular disorders and the occurrence of VAs were associated with increased short- and long-term mortality.

Arrhythmias in Patients on Maintenance Dialysis: A Cross-sectional Study.

RATIONALE & OBJECTIVE: Patients with kidney failure treated with maintenance dialysis experience a high rate of mortality, in part due to sudden cardiac death caused by arrhythmias. The prevalence of arrhythmias, including the subset that are clinically significant, is not well known. This study sought to estimate the prevalence of arrhythmias, characterize the pattern of arrhythmic events in relation to dialysis treatments, and identify associated clinical characteristics. STUDY DESIGN: Cross-sectional study. SETTING & PARTICIPANTS: 152 patients with kidney failure treated with maintenance dialysis in Denmark. EXPOSURES: Dialysis treatment; clinical characteristics; cardiac output and preload defined using echocardiography. OUTCOMES: Prevalence and pattern of arrhythmias on 48-hour Holter monitoring; odds ratios for arrhythmias. ANALYTICAL APPROACH: Descriptive analysis of the prevalence of arrhythmias. Pattern of arrhythmias described using a repeated-measures negative binomial regression model. Associations between clinical characteristics and echocardiographic findings with arrhythmias were assessed using logistic regression. RESULTS: Among the 152 patients studied, 83.6% were treated with in-center dialysis; 10.5%, with home hemodialysis; and 5.9%, with peritoneal dialysis. Premature atrial and ventricular complexes were seen in nearly all patients and 41% had paroxysmal supraventricular tachycardia. Clinically significant arrhythmias included persistent atrial fibrillation observed among 8.6% of patients, paroxysmal atrial fibrillation among 3.9%, nonsustained ventricular tachycardia among 19.7%, bradycardia among 4.6%, advanced second-degree atrioventricular block among 1.3%, and third-degree atrioventricular block among 2.6%. Premature ventricular complexes were more common on dialysis days, while tachyarrhythmias were more often observed during dialysis and in the immediate postdialytic period. Older age (OR per 10 years older, 1.53; 95% CI, 1.15-2.03; P=0.003), elevated preload (OR, 4.02; 95% CI, 1.05-15.35; P=0.04), and lower cardiac output (OR per 1L/min greater, 0.66; 95% CI, 0.44-1.00; P=0.05) were independently associated with clinically significant arrhythmias. LIMITATIONS: Arrhythmia monitoring limited to 48 hours; small sample size; heterogeneous nature of the population, risk for residual confounding. CONCLUSIONS: Arrhythmias, including clinically significant abnormal rhythms, were common. Tachyarrhythmias were more frequent during dialysis and the immediate postdialytic period. The relevance of these findings to clinical outcomes requires additional study.

Predictive value of fragmented QRS for ventricular tachyarrhythmias in patients with acute myocardial infarction: A meta-analysis.

BACKGROUND: Recent studies indicated that fragmented QRS (fQRS) is associated with malignant cardiac arrhythmias in patients with acute myocardial infarction (AMI). However, a systematic review and meta-analysis on this issue still have not been conducted. Thus, we performed a systematic review and meta-analysis to access the predictive value of fQRS for ventricular tachyarrhythmias (VTAs) in patients with AMI. MATERIALS AND METHODS: We searched the databases of PubMed, Embase and Cochrane Library for relevant studies until 8 June 2019. We included studies which compared VTAs in AMI patients with fQRS vs without fQRS. RESULTS: Six studies enrolling 2218 ST-segment elevation myocardial infarction (STEMI) patients were included in this meta-analysis. The fQRS was significantly associated with greater risk of VTAs in STEMI patients (Odds ratio [OR] 2.81, 95% confidence interval (CI) 1.99-3.95, P < .00001; I2  = 30%). This association was still significant both in prospective (OR 3.25, 95% CI 1.94-5.46, P < .00001; I2  = 0%) and retrospective (OR 2.40, 95% CI 1.22-4.74, P = .01; I2  = 54%) studies. In particularly, fQRS in patients with low left ventricular ejection fraction (≤50%) (OR 2.97, 95% CI 1.88-4.70, P < .00001; I2  = 21%) or <60 years old (OR 3.07, 95% CI 2.02-4.66, P < .00001; I2  = 0%) tripled the risk of VTAs during AMI. CONCLUSION: Our meta-analysis demonstrated that fQRS increases the risk of developing VTAs in patients with STEMI.

The role of amiodarone in contemporary management of complex cardiac arrhythmias.

Amiodarone is an iodinated benzofuran derivative, a highly lipophilic drug with unpredictable pharmacokinetics. Although originally classified as a class III agent due to its ability to prolong refractoriness in cardiac regions and prevent/terminate re-entry, amiodarone shows antiarrhythmic properties of all four antiarrhythmic drug classes. Amiodarone is a potent coronary and peripheral vasodilator and can be safely used in patients with left ventricular dysfunction after myocardial infarction or those with congestive heart failure or hypertrophic cardiomyopathy. Its use is regularly accompanied with QT and QTc-interval prolongation but rarely with ventricular proarrhythmia. It is the most powerful pharmacological agent for long-term sinus rhythm maintenance in patients with atrial fibrillation. Amiodarone, particularly if co-administered with beta-blockers, reduces the rate of arrhythmic death due to ventricular tachyarrhythmias in patients with heart failure, but its benefit on cardiovascular and overall survival in these patients is uncertain. In addition, amiodarone is an important adjuvant drug for the reduction of shocks in patients with an implantable cardioverter-defibrillator. Over the past 40 years, amiodarone became the most prescribed antiarrhythmic. Nevertheless, the slow onset of its antiarrhythmic action requires a loading dose while the high risk of non-cardiac toxicity and common drug-drug interactions limit its long-term use. Furthermore patients treated with amiodarone require a close supervision by the treating physician. Therefore amiodarone is generally considered a secondary therapeutic option. Long-term treatment with amiodarone should be based on the use of minimal doses for satisfactory arrhythmia outcome and serial screening for thyroid, liver and pulmonary toxicity.

Incidence, mechanisms, and clinical impact of inappropriate shocks in patients with a subcutaneous defibrillator.

AIMS: Inappropriate shocks (IAS) remain a challenge for patients and physicians after implantation of the subcutaneous implantable cardioverter-defibrillator (S-ICD). The aims were to assess and characterize different patterns of IAS. METHODS AND RESULTS: Two hundred and thirty-nine patients were implanted with an S-ICD between 2010 and 2018 for primary and secondary prevention. Follow-up data of at least 6 months were analysed. During a mean follow-up of 34.9 ± 16.0 months, a total of 73 shocks occurred in 38 patients (6%). Forty-three (59%) shocks were considered appropriate due to ventricular tachycardia/ventricular fibrillation, while 30 (41%) were inappropriate and occurred in 19 patients (8%). Myopotentials/noise was the most frequent cause of inappropriate shocks (n = 8), followed by T-wave oversensing (n = 6) and undersensing of the QRS, resulting in adaptation of the automatic gain control and inappropriate shock (n = 5). Seventy-four percent of all IAS occurred on the primary vector, while no IAS occurred on the alternate vector. In seven of eight patients (88%), IAS related to myopotentials have occurred on the primary sensing vector. Multivariate analysis identified taller patients, primary sensing vector and first-generation S-ICD device as predictors for IAS. SMART pass effectively reduced the occurrence of IAS in the second-generation S-ICD system. CONCLUSION: Inappropriate therapies are less frequently observed on the alternate vector. The primary vector seems to be unfavourable with regard to oversensing caused by myopotentials. Inappropriate shocks were associated with an increased rate of rehospitalization but not mortality. These observations have implications for the prevention of inappropriate S-ICD shocks.