Prevalence and predictors of Twiddler's syndrome.

BACKGROUND: Twiddler's syndrome is a poorly understood clinical phenomenon when patients either consciously or subconsciously rotate their cardiac device resulting in lead dislodgement. We aimed to determine the true prevalence and risk factors associated with Twiddler's syndrome in a real-world population. METHODS: A retrospective chart review was performed on all patients who underwent cardiac device implantation from January 1st 2017 until Jan 1st 2022. We specifically searched for the terms "Twiddler" or "Twiddler's" imbedded within the text of the medical chart. Demographic and clinical variables were collected from the electronic medical record system. We utilized multivariable logistic regression analysis as well as Kaplan-Meier prediction models to determine independent clinical predictors of Twiddler's syndrome as well as associated mortality, respectively. RESULTS: Twenty one out of 1793 patients (1.2%) were identified as having Twiddler's syndrome after chart review. Independent variables associated with Twiddler's syndrome were female sex (OR 3.76; 95% CI 1.29-10.95), antidepressant medications (OR 3.58; 95% CI 1.07-11.99), and BMI (OR 1.08; 95% CI 1.03-1.31). There was no increased six-month mortality via Kaplan-Meier analysis. CONCLUSION: Our study shows that 1.2% of patients in our real-world population had evidence of Twiddler's syndrome. Independent predictors of Twiddler's syndrome include female sex, antidepressant medications as well as BMI.

Feasibility and safety of laser balloon pulmonary vein isolation in patients with prior left atrial appendage occlusion device implantation.

INTRODUCTION: With the increasing adoption of left atrial appendage occlusion (LAAO) procedures and the eligibility of patients for pulmonary vein isolation (PVI) post device placement, we examined the feasibility and safety of laser balloon (LB) for PVI in patients with prior LAAO. METHODS: We retrospectively examined consecutive patients with paroxysmal or persistent, drug-resistant atrial fibrillation (AF) who underwent LB PVI, after Watchman FLX device implantation at Rush University Medical Center between January 2020 and December 2021. RESULTS: Seven patients (four persistent and three paroxysmal) with a mean age of 64 ± 11 years, predominantly male sex (86%), were included in the study. Two (29%) patients had prior cryoablation PVI with recurrence of AF. The mean CHA2 DS2 VASc is 2.6 ± 0.5 and the mean HAS-BLED score is 3.4 ± 0.8. The mean follow-up duration was 10 ± 7 months. The mean duration between Watchman FLX device implantation and LB PVI was 592 days. Acute first pass left pulmonary vein (PV) isolation was achieved in 100% of the procedures. There were no periprocedural complications such as death, pericardial tamponade or effusion, phrenic nerve injury, PV stenosis, device perforation or embolization, or worsening peri-device leak in any of the patients. None of the patients had AF recurrence after the blanking period. CONCLUSION: LB PVI was safe and effective with 100% acute isolation of left-sided veins in patients with prior LAAO device.

The role of heart rate variability, heart rate turbulence, and deceleration capacity in predicting cause-specific mortality in chronic heart failure.

BACKGROUND: The volume of regional denervated myocardium (D-M) on positron emission tomography has been recently suggested as a strong independent predictor of cause-specific mortality from sudden cardiac arrest (SCA) in chronic heart failure. We sought to evaluate whether ECG indices of global autonomic function predict risk of SCA to a similar degree as regional D-M. METHODS: Subjects enrolled in the Prediction of Arrhythmic Events using Positron Emission Tomography (PAREPET) study were included in this study. Patients completed a 24-hour Holter ECG at enrollment and were followed up at 3-month intervals. SCA events were adjudicated by two board-certified cardiologists. Other cardiovascular death events were classified as nonsudden cardiac death (NSCD). Eight measures of heart rate variability were analyzed: SDNN, RMSSD, low-frequency (LF) and high-frequency (HF) power, heart rate turbulence onset and slope, and acceleration and deceleration capacity. We used competing risk regression to delineate cause-specific mortality from SCA versus NSCD. RESULTS: Our sample included 127 patients (age 67 ±â€¯12, 92% male). After a median follow-up of 4.1 years, there were 22 (17%) adjudicated SCA and 18 (14%) adjudicated NSCD events. In multivariate Cox-regression, LF power was the only HRV parameter to predict time-to-SCA. However, in competing risk analysis, reduced LF power was preferentially associated with NSCD rather than SCA (HR = 0.92 [0.85-0.98], p = 0.019). CONCLUSION: Depressed LF power might indicate impaired vagal reflex, which suggests that increasing vagal tone in these patients would have a protective effect against NSCD beyond that achieved by the mere slowing of heart rate using ß-blockers.

Tyrosine kinase inhibitor-associated ventricular arrhythmias: a case series and review of literature.

BACKGROUND: Tyrosine kinase inhibitors (TKIs) have been increasingly used as first-line therapy in hematologic and solid-organ malignancies. Multiple TKIs have been linked with the development of cardiovascular complications, especially atrial arrhythmias, but data on ventricular arrhythmias (VAs) is scarce. METHODS: Herein we describe five detailed cases of VAs related to TKI use in patients with varied baseline cardiovascular risk factors between 2019 and 2022 at three centers. Individual chart review was conducted retrospectively. RESULTS: Patient ages ranged from 43 to 83 years. Three patients were on Bruton's TKI (2 ibrutinib and 1 zanubrutinib) at the time of VAs; other TKIs involved were afatinib and dasatinib. Three patients had a high burden of non-sustained ventricular tachycardia (NSVT) requiring interventions, whereas two patients had sustained VAs. While all patients in our case series had significant improvement in VA burden after TKI cessation, two patients required new long-term antiarrhythmic drug therapy, and one had an implantable defibrillator cardioverter (ICD) placed due to persistent VAs after cessation of TKI therapy. One patient reinitiated TKI therapy after control of arrhythmia was achieved with antiarrhythmic drug therapy. CONCLUSIONS: Given the expanding long-term use of TKIs among a growing population of cancer patients, it is critical to acknowledge the association of TKIs with cardiovascular complications such as VAs, to characterize those at risk, and deploy preventive and therapeutic measures to avoid such complications and interference with oncologic therapy. Further efforts are warranted to develop monitoring protocols and optimal treatment strategies for TKI-induced VAs.

QRS fragmentation and the risk of sudden cardiac death in MADIT II.

BACKGROUND: QRS fragmentation (fQRS) has been reported as a useful ECG parameter in predicting mortality in high-risk postinfarction patients. Its prognostic value for sudden cardiac death (SCD) and ventricular arrhythmias in ischemic cardiomyopathy (ICM) remains unknown. METHODS: MADIT II enrollment 12-lead ECGs were analyzed for fQRS defined as RSR' patterns (≥1 R' or notching of S or R wave) in patients with a normal QRS duration and >2 notches on the R or S wave in patients with abnormal QRS duration, present in 2 contiguous leads. Exclusion criteria included a paced rhythm and an uninterpretable or incomplete ECG. Study endpoints included SCD, SCD or appropriate implantable cardioverter defibrillator (ICD) shock, and total mortality (TM). RESULTS: Of the 1,232 ECGs reviewed, 1,040 were of suitable quality for fQRS analysis. QRS fragmentation was found in 33% of patients in any leads, in 10% of patients in anterior leads, in 8% of patients in lateral leads and in 21% of patients in inferior leads. Anterior and lateral location of QRS fragmentation was not associated with follow-up events. Inferior location of fQRS was found to be predictive of SCD/ICD shock (hazard ratio [HR] 1.46, P = 0.032), SCD (HR 2.05, P = 0.007), and TM (HR 1.44, P = 0.036). This association was driven primarily by the increase in events found in LBBB patients: SCD/ICD shock (HR 2.05, P = 0.046), SCD (HR 4.24, P = 0.002), and TM (HR 2.82, P = 0.001). CONCLUSIONS: Fragmented QRS, especially identified in inferior leads, is predictive of SCD, SCD or appropriate ICD shock, and all-cause mortality in patients with ICM. Identifying inferior fQRS in patients with LBBB is of particular prognostic significance and should reinforce the use of ICD therapy in this high-risk group.

Wide area circumferential ablation for pulmonary vein isolation using radiofrequency versus laser balloon ablation.

Background: Persistent atrial fibrillation (AF) is associated with high recurrence rates of AF and atypical atrial flutters or tachycardia (AFT) postablation. Laser balloon (LB) ablation of the pulmonary vein (PV) ostia has similar efficacy as radiofrequency wide area circumferential ablation (RF-WACA); however, an approach of LB wide area circumferential ablation (LB-WACA) may further improve success rates. Objective: To evaluate freedom from atrial tachyarrhythmia (AFT/AF) recurrence postablation using RF-WACA versus LB-WACA in persistent AF patients. Methods: This was a retrospective multicenter study. Patients were followed for up to 24 months via office visits, Holter, and/or device monitoring. The primary endpoint was freedom from AFT/AF after a single ablation procedure. Secondary endpoints included freedom from AF, freedom from AFT, first-pass isolation of all PVs, and procedural complications. Results: Two hundred and four patients were studied (LB-WACA: n = 103; RF-WACA: n = 101). Patients' baseline characteristics were similar except patients in the RF-WACA group were older (64 vs. 68, p = .03). First-pass isolation was achieved more often during LBA (LB-WACA: 88% vs. RF-WACA 75%; p = .04). Procedure (p = .36), LA dwell (p = .41), and fluoroscopy (p = .44) time were similar. The mean follow-up was 506 ± 279 days. Sixty-six patients had arrhythmic events including 24 AFT and 59 AF recurrences. LB-WACA group had higher arrhythmia-free survival (p = .009) after single ablation procedures. In the multivariate Cox regression model, RF-WACA was associated with a higher recurrence of AFT compared with LB-WACA (Adjusted HR 3.16 [95% CI: 1.13-8.83]; p = .03). Conclusions: LB-WACA was associated with higher freedom from atrial arrhythmias mostly driven by the lower occurrence of AFT compared with RF-WACA.

Supplemental Radiofrequency Ablation After Acutely Unsuccessful Cryoballoon Pulmonary Vein Isolation is Associated With Increased Risk of Recurrent Atrial Fibrillation.

Background Cryoballoon (CB) ablation is widely performed for pulmonary vein isolation (PVI) in patients with atrial fibrillation (AF). Anatomic variations in patient pulmonary vein (PV) anatomy are believed to impact short- and long-term procedural success of CB PVI. Methods and Results We hypothesized that failure of initial PV isolation with a standard technique (ie, requiring >2 freeze cycles per PV and/or radiofrequency ablation [RFA] to achieve PV isolation) during index CB PVI procedures would be associated with decreased freedom from AF. We examined a cohort of 177 consecutive patients with drug-refractory AF who underwent CB PVI with a 28-mm balloon second-generation CB device. Mean follow-up time was 19±9 months. Forty-three patients had AF recurrence after the 90-day blanking period after ablation. In 40 patients, acute isolation of one or more PVs could not be achieved by CB ablation with the standard technique (single freeze with or without bonus freeze). To obtain complete acute PVI, 15 patients received extra freeze applications, 20 required supplemental RFA, and 5 received both extra freeze applications and supplemental RFA. Multivariate regression analysis revealed supplemental RFA use during index CB PVI procedures was independently associated with a threefold increased risk of AF recurrence (adjusted hazard ratio, 3.01; 1.45-10.87; P=0.003). Conclusions Use of supplemental RFA during CB PVI procedures to assist with isolation of one or more PVs was independently associated with increased risk of AF recurrence. Use of additional freezes to achieve PVI did not increase the risk for recurrent AF.

Development of New-Onset or Progressive Atrial Fibrillation in Patients With Permanent HIS Bundle Pacing Versus Right Ventricular Pacing: Results From the RUSH HBP Registry.

Background Conventional right ventricular pacing (RVP) has been associated with an increased incidence of atrial fibrillation (AF). We sought to compare the occurrence of new-onset AF and assessed AF disease progression during long-term follow-up between His bundle pacing (HBP) and RVP. Methods and Results We included patients undergoing initial dual-chamber pacemaker implants at Rush University Medical Center between January 1, 2016, and June 30, 2019. A total of 360 patients were evaluated, and 225 patients (HBP, n=105; RVP, n=120) were included in the study. Among the 148 patients (HBP, n=72; RVP, n=76) with no history of AF, HBP demonstrated a lower risk of new-onset AF (adjusted hazard ratio [HR], 0.53; 95% CI, 0.28-0.99; P=0.046) compared with traditional RVP. This benefit was observed with His or RVP burden exceeding 20% (HR, 0.29; 95% CI, 0.13-0.64; P=0.002), ≥40% (HR, 0.31; P=0.007), ≥60% (HR, 0.35; P=0.015), and ≥80% (HR, 0.40; P=0.038). There was no difference with His or RV pacing burden <20% (HR, 0.613; 95% CI, 0.213-1.864; P=0.404). In patients with a prior history of AF, there was no difference in AF progression (P=0.715); however, in a subgroup of patients with a pacing burden ≥40%, HBP demonstrated a trend toward a lower risk of AF progression (HR, 0.19; 95% CI, 0.03-1.16; P=0.072). Conclusions HBP demonstrated a lower risk of new-onset AF compared with RVP, which was primarily observed at a higher pacing burden.

Efficacy of medical therapy for the reduction of heart failure events in patients with implanted cardioverter defibrillators.

BACKGROUND: Prophylactic therapy with the implantable cardioverter defibrillator (ICD) reduces the mortality among patients with left ventricular dysfunction; however, life-prolonging device therapy has been shown to be associated with an increased risk for subsequent heart failure (HF) events. There are limited data on the effect of the primary types of HF medications, angiotensin converting enzyme inhibitors (ACE-I), and beta-blockers on HF progression in ICD-treated patients. METHODS: Multivariate Cox proportional hazards regression analysis was used to assess the effect of time-dependent medical therapy with ACE-I and beta-blockers on the development of HF in patients with an ICD in the Multicenter Automatic Defibrillator Trail (MADIT) II. RESULTS: In multivariate analysis, ICD therapy was associated with a significant 39% increase in the risk of HF as compared with conventional medical therapy. ACE-I and beta-blockers exhibited a graded efficacy for the reduction in the risk of HF events in ICD-treated patients: the greatest risk reduction of HF was seen in patients taking combination therapy (HR = 0.36, P < 0.001), followed by patients using beta-blockers only (HR = 0.51, P = 0.017) and ACE-I only (HR = 0.64, P = 0.071). Beta-blocker subtypes (metoprolol [HR = 0.49, P = 0.001] and carvedilol [HR = 0.58, P = 0.004]) exhibited similar efficacy. Consistent results were demonstrated when the combined endpoint of HF or death was assessed. CONCLUSIONS: ICD-treated patients experience an increased risk for HF events that can be significantly attenuated by medical therapy with beta-blockers and ACE-inhibitors.

Clinical Outcomes of Selective Versus Nonselective His Bundle Pacing.

OBJECTIVES: The aim of the study was to evaluate the clinical outcomes of nonselective (NS) His bundle pacing (HBP) compared with selective (S) HBP. BACKGROUND: HBP is the most physiologic form of ventricular pacing. NS-HBP results in right ventricular septal pre-excitation due to fusion with myocardial capture in addition to His bundle capture resulting in widened QRS duration compared with S-HBP wherein there is exclusive His bundle capture and conduction. METHODS: The Geisinger and Rush University HBP registries comprise 640 patients who underwent successful HBP. Our study population included 350 consecutive patients treated with HBP for bradyarrhythmic indications who demonstrated ≥20% ventricular pacing burden 3 months post-implantation. Patients were categorized into S-HBP or NS-HBP based on QRS morphology (NS-HBP n = 232; S-HBP n = 118) at the programmed output at the 3-month follow-up. The primary analysis outcome was a combined endpoint of all-cause mortality or heart failure hospitalization. RESULTS: The NS-HBP group had a higher number of men (64% vs. 50%; p = 0.01), higher incidence of infranodal atrioventricular block (40% vs. 9%; p < 0.01), ischemic cardiomyopathy (24% vs. 14%; p = 0.03), and permanent atrial fibrillation (18% vs. 8%; p = 0.01). The primary endpoint occurred in 81 of 232 patients (35%) in the NS-HBP group compared with 23 of 118 patients (19%) in the S-HBP group (hazard ratio: 1.38; 95% confidence interval: 0.87 to 2.20; p = 0.17). Subgroup analyses of patients at greatest risk (higher pacing burden or lower left ventricular ejection fraction) revealed no incremental risk with NS-HBP. CONCLUSIONS: NS-HBP was associated with similar outcomes of death or heart failure hospitalization when compared with S-HBP. Multicenter risk-matched clinical studies are needed to confirm these findings.

Gender-related differences in electrocardiographic parameters and their association with cardiac events in patients after myocardial infarction.

There are limited data regarding gender-related differences in electrocardiographic (ECG) presentation in patients after myocardial infarction (MI) and the prognostic value of ECG variables in women. A series of ECG parameters were analyzed in 838 patients (216 women, 622 men) using standard electrocardiography performed 5 to 7 days after first MI, and their associations with gender and risk for cardiac events, defined as cardiac death, nonfatal MI, or unstable angina, were evaluated. Heart rate was faster and QTc duration was longer, whereas QRS duration was shorter in women compared with men. Women had more lateral ST depressions and more T-wave inversions in the anterior and lateral regions. During mean 2-year follow-up, there were 138 events in men and 65 in women; women had a 38% greater risk for recurrent events (adjusted hazard ratio [HR] 1.38, p = 0.031). In multivariate Cox regression analysis, ST-segment elevation in leads V(1) to V(4) on the fifth to seventh day after MI was associated with increased risk for recurrent events in women (adjusted HR 2.16, p = 0.003) but not in men (adjusted HR = 0.81, p = 0.32). ST depressions in leads V(5), V(6), I, or aVL (adjusted HR 1.70, p = 0.006) in men but not in women (adjusted HR 0.98, p = 0.93) were identified as a risk factor for recurrent events. In conclusion, there are gender-related differences in ECG presentation and the prognostic significance of ECG findings after MI. ST-segment elevation in anterior leads is a significant predictor of events in women, whereas ST depression in lateral leads is a significant predictor in men.

Cumulative burden of atherosclerotic risk genotypes and the age at onset of a first myocardial infarction: a case-only carriership approach.

BACKGROUND: Previously identified atherosclerotic genetic factors have been studied mostly in case-control studies and in nonuniform ethnic populations, whereas data on the cumulative contribution of genetic factors to an earlier onset of a first myocardial infarction (MI) are limited. We hypothesized that several genetic atherosclerotic single nucleotide polymorphisms (SNPs) may exert an additive effect on the earlier occurrence of coronary atherothrombotic disease after adjustment for clinical factors. METHODS: Eighteen atherosclerotic high-risk SNPs were selected based upon meta-analyses of 614 published reports, and were incorporated into a carriership model. Multivariate regression analysis was used to identify the independent contribution of selected genotypes to the age at onset of a first MI in a cohort of 814 white (n = 622) and nonwhite (n = 192) patients enrolled in the Thrombogenic Factors and Coronary Events Study. RESULTS: The analysis demonstrated that selected genotypes were significantly associated with an earlier occurrence of a first MI among white patients (an average of 0.6 year reduction per carried genotype; P = 0.027), whereas the contribution of genotypes to MI onset among nonwhite patients was not significant (an average of 0.7 year increase per carried genotype; P = 0.16), with a significant ethnic x genotype interaction effect (P = 0.02). CONCLUSIONS: Our findings suggest that currently identified atherosclerotic genetic factors confer an independent additive contribution to the earlier onset of coronary atherothrombotic disease among white patients. The lack of a significant association between these genotypes and outcome in other ethnic groups suggests that cardiovascular genetic risk should be studied directly in these populations.

Prognostic significance of fragmented QRS complex for predicting the risk of recurrent cardiac events in patients with Q-wave myocardial infarction.

There are limited data regarding the prognostic value of QRS complex fragmentation, defined as changes in QRS morphology (<120 ms) with different RSR' patterns: additional R waves, notched S wave, or >1 R' wave. The purpose of our analysis was to assess the prognostic value of presence of Q waves and QRS fragmentation for predicting recurrent cardiac events, defined as cardiac death, nonfatal myocardial infarction (MI), or unstable angina, whichever occurs first, in 350 patients with first Q-wave MI. In follow-up (2 months on average) electrocardiograms (ECGs), 277 patients (79%) had persistent Q waves and 73 (21%) had resolution of Q waves. Independently of Q waves, presence of QRS complex fragmentation was found in 187 patients (53%). Resolved Q waves on 2-month ECGs was associated with worsened prognosis (adjusted hazard ratio [HR] 2.33, p = 0.007), whereas presence of any fragmented QRS did not increase risk of recurrent cardiac events (adjusted HR 0.93, p = 0.79). Among patients for whom Q waves disappeared on 2-month ECGs, patients with QRS fragmentation (n = 37) had over twofold higher risk of recurrent events (adjusted HR 2.68, p = 0.004) compared with those without fragmented QRS and persistent Q waves. In conclusion, presence of fragmented QRS independently of Q waves was not associated with increased risk of recurrent events in the general population of patients after MI. However, among patients with resolved Q waves, fragmented QRS was associated with increased risk of cardiac events. Fragmented QRS complex should not be neglected in patients with transient Q waves after myocardial infarction.

Obesity as a risk factor for sustained ventricular tachyarrhythmias in MADIT II patients.

BACKGROUND: Obesity, as defined by body mass index > or =30 kg/m(2), has been shown to be a risk factor for cardiovascular disease. However, data on the relationship between body mass index (BMI) and the risk of ventricular arrhythmias and sudden cardiac death are limited. The aim of this study was to evaluate the risk of ventricular tachyarrhythmias and sudden death by BMI in patients after myocardial infarction with severe left ventricular dysfunction. METHODS: The risk of appropriate defibrillator therapy for ventricular tachycardia or ventricular fibrillation (VT/VF) by BMI status was analyzed in 476 nondiabetic patients with left ventricular dysfunction who received an implantable cardioverter defibrillator (ICD) in the Multicenter Automatic Defibrillator Implantation Trial-II (MADIT II). RESULTS: Mean BMI was 27 +/- 5 kg/m(2). Obese patients comprised 25% of the study population. After 2 years of follow-up, the cumulative rates of appropriate ICD therapy for VT/VF were 39% in obese and 24% in nonobese patients, respectively (P = 0.014). In multivariate analysis, there was a significant 64% increase in the risk for appropriate ICD therapy among obese patients as compared with nonobese patients, which was attributed mainly to an 86% increase in the risk of appropriate ICD shocks (P = 0.006). Consistent with these results, the risk of the combined endpoint of appropriate VT/VF therapy or sudden cardiac death (SCD) was also significantly increased among obese patients (Hazard Ratio 1.59; P = 0.01). CONCLUSIONS: Our findings suggest that in nondiabetic patients with ischemic left ventricular dysfunction, a BMI > or =30 kg/m(2) is an independent risk factor for ventricular tachyarrhythmias.

The effect of intermittent atrial tachyarrhythmia on heart failure or death in cardiac resynchronization therapy with defibrillator versus implantable cardioverter-defibrillator patients: a MADIT-CRT substudy (Multicenter Automatic Defibrillator Implantation Trial With Cardiac Resynchronization Therapy).

OBJECTIVES: This study aimed to investigate the effect of both history of intermittent atrial tachyarrhythmias (IAT) and in-trial IAT on the risk of heart failure (HF) or death comparing cardiac resynchronization therapy with defibrillator (CRT-D) to implantable cardioverter-defibrillator (ICD) treatment in mildly symptomatic HF patients with left bundle branch block (LBBB). BACKGROUND: Limited data exist regarding the benefit of CRT-D in patients with IAT. METHODS: The benefit of CRT-D in reducing the risk of HF/death was evaluated using multivariate Cox models incorporating the presence of, respectively, a history of IAT at baseline and time-dependent development of in-trial IAT during follow-up in 1,264 patients with LBBB enrolled in the MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial With Cardiac Resynchronization Therapy) study. RESULTS: The overall beneficial effect of CRT-D versus ICD on the risk of HF/death was not significantly different between LBBB patients with or without history of IAT (HR: 0.50, p = 0.028, and HR: 0.46, p < 0.001, respectively; p for interaction = 0.79). Among patients who had in-trial IAT, CRT-D was associated with a significant 57% reduction in the risk of HF/death compared with ICD-only therapy (HR: 0.43, p = 0.047), similar to the effect of the device among patients who did not have IAT (HR: 0.47, p < 0.001; p for interaction = 0.85). The percentage of patients with biventricular pacing ≥92% was similar in both groups (p = 0.43). Consistent results were shown for the benefit of CRT-D among patients who had in-trial atrial fibrillation/flutter (HR: 0.30, p = 0.027; p for interaction = 0.41). CONCLUSIONS: In the MADIT-CRT study, the clinical benefit of CRT-D in LBBB patients was not attenuated by prior history of IAT or by the development of in-trial atrial tachyarrhythmias. (MADIT-CRT: Multicenter Automatic Defibrillator Implantation Trial With Cardiac Resynchronization Therapy; NCT00180271).

QRS fragmentation: diagnostic and prognostic significance.

Fragmentation of QRS (fQRS) complex is an easily evaluated non-invasive electrocardiographic parameter. Fragmentation of narrow QRS is defined as presence of an additional R wave (R') or notching in the nadir of the S wave, or the presence of > 1 R' in 2 contiguous leads, corresponding to a major coronary artery territory on the resting 12-lead ECG. Fragmentation of wide complex QRS consists of various RSR patterns, with more than 2 R waves (R'') or more than 2 notches in the R wave, or more than 2 notches in the downstroke or upstroke of the S wave. Presence of fQRS has been associated with alternation of myocardial activation due to myocardial scar and myocardial fibrosis. Initial studies reported higher sensitivity of fQRS than Q wave for detecting myocardial scar and postulated that the presence of fQRS could be a good predictor of cardiac events among the patients with coronary artery disease. The presence of fQRS has been investigated among the patients with ischemic and non-ischemic cardiomyopathy suggesting that this ECG parameter may affect prognosis and risk of sudden cardiac death, risk of implantable cardioverter-defibrillator therapy and response to cardiac resynchronization therapy. In addition, there is evidence that fQRS could play an important role as screening and prognostic tool among the patients with Brugada syndrome, long QT syndrome, arrhythmogenic right ventricular dysplasia and cardiac sarcoidosis. This paper reviews definition, diagnostic and prognostic value of fQRS in different patient populations.