Feasibility and safety of left atrial posterior wall isolation with a new Cryoballoon technology in patients with persistent atrial fibrillation.

BACKGROUND: Left atrial posterior wall isolation (LAPWI) is often performed in addition to pulmonary vein isolation (PVI) in the setting of persistent atrial fibrillation (AF) ablation. The aim of this study was to evaluate the feasibility and safety of a new cryoballoon ablation system in achieving PVI + LAPWI isolation. METHODS: The study was a prospective, non-randomized, single center study. Forty consecutive patients, undergoing PVI + LAPWI with the novel POLARx™, were compared to 40 consecutive patients who underwent the same procedure with the established Arctic Front Advance PRO™. RESULTS: Acute isolation was achieved in all PVs in both groups and left posterior wall isolation (LAPWI) was achieved in 38 patients (95%) in the POLARx group and in 36 patients (90%) in Arctic Front group. Procedural outcomes were similar between both groups, except for lower temperatures during cryoenergy in the POLARx group, for both pulmonary vein isolation (PVI) and LAPWI. CONCLUSION: LAPWI + PVI with the novel POLARx™ Cryoballoon is feasible and safe; the results are comparable with the Arctic Front Advance PRO™ system.

Comparison between the novel diamond temp and the classical 8-mm tip ablation catheters in the setting of typical atrial flutter.

PURPOSE: Radiofrequency (RF) catheter ablation is widely accepted as a first-line therapy for cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL). The novel DiamondTemp (DT) catheter with temperature feedback during RF ablation has been released recently on the market. The purpose of this study was to evaluate the impact of DiamondTemp (DT) technology on ablation efficiency during AFL. METHODS: In this single-center study, 30 consecutive patients with typical AFL indicated to ablation of CTI were included. The first 15 patients underwent CTI ablation using 8-mm tip catheter, and the following 15 patients underwent temperature-controlled RF ablation using DT catheter. The endpoints were number and mean total duration of RF applications, mean temperature reached in the setting of CTI, procedural times, and fluoroscopy times. RESULTS: There were no significant differences between the two groups concerning baseline characteristics. Mean duration of the each application (71.5 s ± 30.6 vs 12.4 s ± 13.2, p value < 0.001), mean total duration of RF applications (517,73 s ± 377,96 vs 112,8 s ± 43,58; p value < 0.001), procedural times (51.6 min ± 24.2 vs 38.6 ± 8.2; p = 0.03), and fluoroscopy times (16.2 min ± 10.2 vs 8 min ± 4.24; p = 0.005) were longer in the 8-mm ablation catheter group. Mean temperature measurements (51.9 °C ± 3.59 vs 56.7 °C ± 3.34, p value < 0.003) were as well lower in the 8-mm ablation catheter group. CONCLUSIONS: Catheter ablation of CTI-dependent AFL by means of DT resulted in a significant reduction of total and single application RF delivery time, procedure, and fluoroscopy times.

Myocardial disease and ventricular arrhythmia in Marfan syndrome: a prospective study.

BACKGROUND: Aortic root dilatation and-dissection and mitral valve prolapse are established cardiovascular manifestations in Marfan syndrome (MFS). Heart failure and arrhythmic sudden cardiac death have emerged as additional causes of morbidity and mortality. METHODS: To characterize myocardial dysfunction and arrhythmia in MFS we conducted a prospective longitudinal case-control study including 86 patients with MFS (55.8% women, mean age 36.3 yr-range 13-70 yr-) and 40 age-and sex-matched healthy controls. Cardiac ultrasound, resting and ambulatory ECG (AECG) and NT-proBNP measurements were performed in all subjects at baseline. Additionally, patients with MFS underwent 2 extra evaluations during 30 ± 7 months follow-up. To study primary versus secondary myocardial involvement, patients with MFS were divided in 2 groups: without previous surgery and normal/mild valvular function (MFS-1; N = 55) and with previous surgery or valvular dysfunction (MFS-2; N = 31). RESULTS: Compared to controls, patients in MFS-1 showed mild myocardial disease reflected in a larger left ventricular end-diastolic diameter (LVEDD), lower TAPSE and higher amount of (supra) ventricular extrasystoles [(S)VES]. Patients in MFS-2 were more severely affected. Seven patients (five in MFS-2) presented decreased LV ejection fraction. Twenty patients (twelve in MFS-2) had non-sustained ventricular tachycardia (NSVT) in at least one AECG. Larger LVEDD and higher amount of VES were independently associated with NSVT. CONCLUSION: Our study shows mild but significant myocardial involvement in patients with MFS. Patients with previous surgery or valvular dysfunction are more severely affected. Evaluation of myocardial function with echocardiography and AECG should be considered in all patients with MFS, especially in those with valvular disease and a history of cardiac surgery.

Case report: Synergetic effect of ischaemia and increased vagal tone inducing ventricular fibrillation in a patient with Brugada syndrome.

BACKGROUND: Brugada syndrome (BS) is a hereditary channelopathy associated with syncope, malignant ventricular arrhythmia, and sudden cardiac death. Right ventricular ischaemia and BS have similar underlying substrates precipitating ventricular tachycardia or fibrillation (VF). CASE SUMMARY: A 72-year-old woman with BS and a stenosis on the proximal right coronary artery received several subsequent implantable cardioverter-defibrillator shocks due to VF during an episode of extreme nausea with vomiting. DISCUSSION: This case report emphasizes on the synergetic effect of mild ischaemia and increased vagal tone on the substrate responsible for BS to create pathophysiological changes precipitating VF.

Early markers of atrial fibrillation recurrence after pulmonary vein isolation.

BACKGROUND: Postprocedural atrial extrasystole (AES) frequency predicts atrial fibrillation (AF) recurrence after pulmonary vein isolation (PVI) in patients with paroxysmal AF. However, the predictive value of preprocedural AES frequency is unknown. We investigate whether preprocedural AES frequency is a feasible marker to predict (timing of) AF recurrence after PVI. METHODS: Patients (N = 684) with paroxysmal or persistent AF undergoing first-time PVI were evaluated for (a) the frequency of AES/day on Holter recordings without AF prior to PVI, (b) AF episodes during the 90 days blanking period, and (c) AF recurrences afterward. The correlation between AES/day and both development and timing of AF recurrences was tested. RESULTS: Preprocedural AES/day was similar in patients with paroxysmal (66 [20-295] AES/day) and persistent AF (115 [12-248] AES/day, P = .915). During the blanking period, 302 (44.2%) patients showed AF episodes. AF recurred in 379 (55.4%) patients at 203 (105-400) days after PVI. AF recurred more frequently in patients with persistent (N = 104 [69.3%]) than in patients with paroxysmal AF (N = 275 [51.5%], P < .001). Frequency of AES prior to PVI was not correlated with development (P = .203) or timing (P = .478) of AF recurrences. AF recurrences occurred both more frequently (P < .001) and earlier (P < .000) in patients with AF during the blanking period. CONCLUSION: AES/day prior to PVI is not correlated with (timing of) AF during the blanking period or AF recurrences, and is therefore not a feasible marker for AF recurrences in patients with PAF. AF during the blanking period is correlated with AF recurrence.

Feasibility of His-bundle pacing in patients with conduction disorders following transcatheter aortic valve replacement.

BACKGROUND: Conduction disorders requiring permanent pacemaker implantation occur frequently after transcatheter aortic valve replacement (TAVR). This multicenter study explored the feasibility and safety of His bundle pacing (HBP) in TAVR patients with a pacemaker indication to correct a TAVR-induced left bundle branch block (LBBB). METHODS: Patients qualifying for a permanent pacemaker implant after TAVR were planned for HBP implant. HBP was performed using the Select Secure (3830; Medtronic) pacing lead, delivered through a fixed curve or deflectable sheath (C315HIS or C304; Medtronic). Successful HBP was defined as selective or nonselective HBP, irrespective of LBB recruitment. Successful LBBB correction was defined as selective or nonselective HBP resulting in paced QRS morphology similar to pre-TAVR QRS and paced QRS duration (QRSd) less than 120 milliseconds with thresholds less than 3.0 V at 1.0-millisecond pulse width. RESULTS: The study enrolled 16 patients requiring a permanent pacemaker after TAVR (age 85 ± 4 years, 31% female, all LBBB; QRSd: 161 ± 14 milliseconds). Capture of the His bundle was achieved in 13 of 16 (81%) patients. HBP with LBBB correction was achieved in 11 of 16 (69%) and QRSd narrowed from 162 ± 14 to 99 ± 13 milliseconds and 134 ± 7 milliseconds during S-HBP and NS-HBP, respectively (P = .005). At implantation, mean threshold for LBBB correction was 1.9 ± 1.1 V at 1.0 millisecond. Thresholds remained stable at 11 ± 4 months follow-up (1.8 ± 0.9 V at 1.0 millisecond, P = .231 for comparison with implant thresholds). During HBP implant, one temporary complete atrioventricular block occurred. CONCLUSION: Permanent HBP is feasible in the majority of patients with TAVR requiring a permanent pacemaker with the potential to correct a TAVR-induced LBBB with acceptable pacing thresholds.

In-hospital and 12-month follow-up outcome from the ESC-EORP EHRA Atrial Fibrillation Ablation Long-Term registry: sex differences.

AIM: The purpose of this study was to compare sex differences of atrial fibrillation (AF) catheter ablation (CA) and to analyse the opportunities for improved outcomes. METHODS AND RESULTS: All data were collected from the Atrial Fibrillation Ablation Long-Term registry, a prospective, multinational study conducted by the ESC-EORP European Heart Rhythm Association (EHRA) under the EURObservational Research Programme (ESC-EORP). A total of 104 centres in 27 European countries participated. Of 3593 included patients, 1146 (31.9%) were female. Female patients were older (61.0 vs. 56.4 years; P < 0.001), had more comorbidities (hypertension, diabetes, and obesity), more episodes of arrhythmias per month (6.9 vs. 6.2; P < 0.001), and a higher average EHRA score (2.6 vs. 2.4; P < 0.001). The duration of the procedure was shorter in females (160.1 min vs. 167.9 min; P < 0.001), irrespective of additional ablation lesions added to pulmonary vein isolation. Overall cardiovascular complications were more frequent in women than in men (5.7% vs. 3.4%; P < 0.001). Furthermore, cardiac perforations (3.8% vs. 1.3%; P = 0.011) and neurological complications (2.2% vs. 0.3%; P = 0.004) were found in females in less experienced centres than in experienced ones. On a final note, at 12 months, AF recurrence rate was similar in females and males (34.4% vs. 34.2%; P = 0.897), but more females were still on antiarrhythmic drugs (50.6% vs. 44.1%; P < 0.001) when compared with men. CONCLUSION: Females underwent CA procedures for AF less frequently than males throughout Europe, despite more recurrent symptoms. With the same success rate, severe acute complications remained considerable in females, especially in less experienced centres.

Sleep apnea and the impact on cardiovascular risk in patients with Marfan syndrome.

BACKGROUND: Marfan syndrome (MFS) is an inherited connective tissue disorder characterized by ectopia lentis, aortic root dilation and dissection and specific skeletal features. Obstructive sleep apnea (OSA) in MFS has been described earlier but the prevalence and its relation with the cardiovascular risk is still controversial. This study aimed to further investigate these aspects. METHODS: In this prospective longitudinal study, we performed an attended polysomnography in 40 MFS patients (60% women, 37 ± 12.8 years) and evaluated several cardiovascular parameters through echocardiography, resting electrocardiogram, 24 hr-Holter monitoring and serum NT-ProBNP measurements. RESULTS: We found that OSA was present in 42.5% of the patients and that higher body mass index was the most important factor associated with the presence of OSA. We observed that overweight was present in 27.5% of the patients in the whole cohort and in 55.6% if >40 years. Furthermore, when evaluating the impact of OSA on the cardiovascular system, we observed that patients with OSA tended to have higher systolic blood pressure, larger distal aortic diameters and a higher prevalence of ventricular arrhythmia. These differences were, however, not significant after adjusting for confounders. CONCLUSIONS: Our study shows a high prevalence of OSA and a high prevalence of overweight in MFS patients. We found some trends between OSA and cardiovascular features but we could not establish a solid association. Our study, however might be underpowered, and a multicenter collaborative study could be very useful to answer some important open questions.

Intensive recreational athletes in the prospective multinational ICD Sports Safety Registry: Results from the European cohort.

BACKGROUND: In the ICD Sports Safety Registry, death, arrhythmia- or shock-related physical injury did not occur in athletes who continue competitive sports after implantable cardioverter-defibrillator (ICD) implantation. However, data from non-competitive ICD recipients is lacking. This report describes arrhythmic events and lead performance in intensive recreational athletes with ICDs enrolled in the European recreational arm of the Registry, and compares their outcome with those of the competitive athletes in the Registry. METHODS: The Registry recruited 317 competitive athletes ≥ 18 years old, receiving an ICD for primary or secondary prevention (234 US; 83 non-US). In Europe, Israel and Australia only, an additional cohort of 80 'auto-competitive' recreational athletes was also included, engaged in intense physical activity on a regular basis (≥2×/week and/or ≥ 2 h/week) with the explicit aim to improve their physical performance limits. Athletes were followed for a median of 44 and 49 months, respectively. ICD shock data and clinical outcomes were adjudicated by three electrophysiologists. RESULTS: Compared with competitive athletes, recreational athletes were older (median 44 vs. 37 years; p = 0.0004), more frequently men (79% vs. 68%; p = 0.06), with less idiopathic ventricular fibrillation or catecholaminergic polymorphic ventricular tachycardia (1.3% vs. 15.4%), less congenital heart disease (1.3% vs. 6.9%) and more arrhythmogenic right ventricular cardiomyopathy (23.8% vs. 13.6%) ( p < 0.001). They more often had a prophylactic ICD implant (51.4% vs. 26.9%; p < 0.0001) or were given a beta-blocker (95% vs. 65%; p < 0.0001). Left ventricular ejection fraction, ICD rate cut-off and time from implant were similar. Recreational athletes performed fewer hours of sports per week (median 4.5 vs. 6 h; p = 0.0004) and fewer participated in sports with burst-performances ( vs. endurance) as their main sports: 4% vs. 65% ( p < 0.0001). None of the athletes in either group died, required external resuscitation or was injured due to arrhythmia or shock. Freedom from definite or probable lead malfunction was similar (5-year 97% vs. 96%; 10-year 93% vs. 91%). Recreational athletes received fewer total shocks (13.8% vs. 26.5%, p = 0.01) due to fewer inappropriate shocks (2.5% vs. 12%; p = 0.01). The proportion receiving appropriate shocks was similar (12.5% vs. 15.5%, p = 0.51). Recreational athletes received fewer total (6.3% vs. 20.2%; p = 0.003), appropriate (3.8% vs. 11.4%; p = 0.06) and inappropriate (2.5% vs. 9.5%; p = 0.04) shocks during physical activity. Ventricular tachycardia/fibrillation storms during physical activity occurred in 0/80 recreational vs. 7/317 competitive athletes. Appropriate shocks during physical activity were related to underlying disease ( p = 0.004) and competitive versus recreational sports ( p = 0.004), but there was no relation with age, gender, type of indication, beta-blocker use or burst/endurance sports. The proportion of athletes who stopped sports due to shocks was similar (3.8% vs. 7.5%, p = 0.32). CONCLUSIONS: Participants in recreational sports had less frequent appropriate and inappropriate shocks during physical activity than participants in competitive sports. Shocks did not cause death or injury. Recreational athletes with ICDs can engage in sports without severe adverse outcomes unless other reasons preclude continuation.

Gender differences in electro-mechanical characteristics of left bundle branch block: Potential implications for selection and response of cardiac resynchronization therapy.

BACKGROUND: Female patients are underrepresented in cardiac resynchronization therapy (CRT) trials, although they show better CRT response compared to males and at shorter QRS durations. We hypothesized that differences in left bundle branch block (LBBB) characteristics and mechanical dyssynchrony might explain this gender disparity. METHODS: Patients presenting with true LBBB-morphology (including mid-QRS notching) on surface electrocardiograms (ECG) were selected. LBBB QRS duration (QRSDLBBB) was measured automatically on the ECG. Left ventricular dimensions were assessed by two-dimensional echocardiography. Mechanical dyssynchrony was assessed by the presence of septal flash (SF) on echocardiography. RESULTS: The study enrolled 1037 patients (428 females). Female LBBB patients had smaller QRSDLBBB compared to male LBBB patients (142 [22]ms versus 156 [24]ms, p<0.001). In a multivariate analysis, sex and left ventricular end-diastolic diameter (LVEDD) were independent predictors of QRSDLBBB. QRSDLBBB can be corrected for sex and LVEDD using a simplified formula: corrected-QRSDLBBB=QRSDLBBB+0.5×(50-LVEDD)-10 (if male). SF was more prevalent in females compared to males (60% versus 43%, p<0.001). Women revealed significantly more SF in narrow QRSDLBBB groups compared to men: 65% versus 13% (p<0.001) with QRSDLBBB 120-129ms, 66% versus 18% (p<0.001) with QRSDLBBB 130-139ms and 63% versus 31% (p<0.001) with QRSDLBBB 140-149ms. At QRSDLBBB>150ms, there were no differences in SF prevalence between females and males. CONCLUSION: Female patients show true LBBB morphology at shorter QRSD and have more frequent mechanical dyssynchrony at shorter QRSD compared to males. This might explain the better CRT response rates at shorter QRSD in females.

Catheter Ablation for Atrial Fibrillation with Heart Failure.

BACKGROUND: Mortality and morbidity are higher among patients with atrial fibrillation and heart failure than among those with heart failure alone. Catheter ablation for atrial fibrillation has been proposed as a means of improving outcomes among patients with heart failure who are otherwise receiving appropriate treatment. METHODS: We randomly assigned patients with symptomatic paroxysmal or persistent atrial fibrillation who did not have a response to antiarrhythmic drugs, had unacceptable side effects, or were unwilling to take these drugs to undergo either catheter ablation (179 patients) or medical therapy (rate or rhythm control) (184 patients) for atrial fibrillation in addition to guidelines-based therapy for heart failure. All the patients had New York Heart Association class II, III, or IV heart failure, a left ventricular ejection fraction of 35% or less, and an implanted defibrillator. The primary end point was a composite of death from any cause or hospitalization for worsening heart failure. RESULTS: After a median follow-up of 37.8 months, the primary composite end point occurred in significantly fewer patients in the ablation group than in the medical-therapy group (51 patients [28.5%] vs. 82 patients [44.6%]; hazard ratio, 0.62; 95% confidence interval [CI], 0.43 to 0.87; P=0.007). Significantly fewer patients in the ablation group died from any cause (24 [13.4%] vs. 46 [25.0%]; hazard ratio, 0.53; 95% CI, 0.32 to 0.86; P=0.01), were hospitalized for worsening heart failure (37 [20.7%] vs. 66 [35.9%]; hazard ratio, 0.56; 95% CI, 0.37 to 0.83; P=0.004), or died from cardiovascular causes (20 [11.2%] vs. 41 [22.3%]; hazard ratio, 0.49; 95% CI, 0.29 to 0.84; P=0.009). CONCLUSIONS: Catheter ablation for atrial fibrillation in patients with heart failure was associated with a significantly lower rate of a composite end point of death from any cause or hospitalization for worsening heart failure than was medical therapy. (Funded by Biotronik; CASTLE-AF ClinicalTrials.gov number, NCT00643188 .).

Comparison of Multivariate Risk Estimation Models to Predict Prognosis in Patients With Implantable Cardioverter Defibrillators With or Without Cardiac Resynchronization Therapy.

Several multivariate risk score models were developed to predict prognosis of patients with heart failure (HF). We compared 3 models with regard to prediction of mortality in patients with HF who received an implantable defibrillator (ICD) or a cardiac resynchronization therapy defibrillator (CRT-D), as primary prevention of sudden death. The study cohort consisted of 823 patients (ICD = 410; CRT-D = 413). The evaluated models were the Seattle Heart Failure Model (SHFM), the Multicenter Automatic Defibrillator Implantation Trial II (MADIT II) score, and an adjusted Charlson Comorbidity Index (aCCI). End point was the performance of the models to predict all-cause mortality at 5 years. This was determined by c-statistics, for both subgroups. Multivariate analysis was used to analyze the relations between the risk score models, their individual components and mortality, and its applicability to the entire population. Cumulative mortality was 4.9% at 1 year and 21.1% at 5 years. Discriminatory power for 5-year mortality was highest for the SHFM (0.73; p <0.001) compared with the MADIT II score and the aCCI for the entire population. SHFM performed better than the MADIT II score for CRT-D group. In the entire population, the SHFM and the aCCI were significant predictors of mortality in multivariate analysis (hazard ratio 1.90, 95% confidence interval 1.49 to 2.43 vs hazard ratio 1.11, 95% confidence interval 1.01 to 1.22). The strongest individual components were age, HF, impaired renal function, and cancer, whereas CRT-D use was no predictor. In conclusion, the SHFM has the best discriminatory power for 5-year mortality in patients with HF with an ICD or CRT-D. The aCCI and MADIT II scores are less powerful but viable alternatives.

Biventricular Paced QRS Area Predicts Acute Hemodynamic CRT Response Better Than QRS Duration or QRS Amplitudes.

INTRODUCTION: Vectorcardiographic (VCG) QRS area of left bundle branch block (LBBB) predicts acute hemodynamic response in cardiac resynchronization therapy (CRT) patients. We hypothesized that changes in QRS area occurring with biventricular pacing (BV) might predict acute hemodynamic CRT response (AHR). METHODS AND RESULTS: VCGs of 624 BV paced electrocardiograms (25 LBBB patients with 35 different pacing configurations) were calculated according to Frank's orthogonal lead system. Maximum QRS vector amplitudes (XAmpl , YAmpl , ZAmpl , and 3DAmp ) and QRS areas (XArea , YArea , ZArea , and 3DArea ) in the orthogonal leads (X, Y, and Z) and in 3-dimensional projection were measured. Volume of the 3D vector loop and global QRS duration (QRSD) on the surface electrocardiogram were assessed. Differences (Δ) in VCG parameters between BV paced and LBBB QRS complexes were calculated. An increase of 10% in dP/dt max was considered as AHR. LBBB conduction is characterized by a large ZArea (109 µVs, interquartile range [IQR]:75;135), significantly larger than XArea (22 µVs, IQR:10;57) and YArea (44 µVs, IQR:32;62, P < 0.001). Overall, QRS duration, amplitudes, and areas decrease significantly with BV pacing (P < 0.001). Of all VCG parameters, 3DAmpl , Δ3DAmpl , ZArea, ΔZArea , Δ3DArea , and ΔQRSD differentiate AHR response from nonresponse (P < 0.05). ΔZArea predicted best positive AHR (area under the curve = 0.813) and outperformed any other VCG parameter or QRSD measurement. CONCLUSION: Of all VCG parameters, reduction in QRS area, calculated in Frank's Z lead, predicts acute hemodynamic response best. This method might be an easy, noninvasive tool to guide CRT implantation and optimization.

Evaluating current implantable cardioverter defibrillator implantation procedures: can common complications be minimised?

The implantable cardioverter-defibrillator (ICD) is the cornerstone of treatment and prevention of malignant ventricular arrhythmias. Despite 30 years of experience, implantation of ICDs carries a risk of complications both during the procedure and long-term follow-up. Operator and procedure related factors may contribute to this risk. Furthermore, access, pocket, device and lead related problems occur, on top of problems related to arrhythmias and the patient themselves. Infection is the most feared complication, and its incidence seems to rise. Factors leading to complications are assessed, as well as measures to reduce these complications, including antibiotics and subcutaneous devices. Four patient categories with an increased risk are identified: the elderly with atrial fibrillation, diabetes or renal failure; the pediatric patient with or without congenital heart disease, the young patient with specific inherited diseases, and all those who undergo replacement, upgrade or concomitant lead extraction.

Different Methods to Measure QRS Duration in CRT Patients: Impact on the Predictive Value of QRS Duration Parameters.

BACKGROUND: Measurements of QRS duration (QRSD) in patients undergoing cardiac resynchronization therapy (CRT) are not standardized. We hypothesized that both the measurement of QRSD and its predictive value on CRT response are sensitive to the method by which QRSD is measured. METHODS: Electrocardiograms (ECGs) pre- and post-CRT from 52 CRT patients (66 ± 12 years, 65% male) were retrospectively analyzed. Custom-made software was developed to measure global QRSD (QRSDglobal ) and lead-specific QRSD (QRSDI,II,III,aVR,aVL,aVF,V1,V2,V3,V4,V5,V6 ). QRSD was also assessed automatic by a routinely used ECG device. For each method we measured QRSD pre- and post-CRT and shortening of QRSD (∆QRSD). Response to CRT at 6 months was defined as an improvement of ≥1 class in New York Heart Association classification and an increase by >7.5% in left ventricular ejection fraction. RESULTS: The CRT response rate was 77% (n = 40). Different methods to measure QRSD show divergent nominal values before (median range 152-172 ms, P < 0.001) and after CRT (130-152 ms, P < 0.001). The predictive value of QRSD measurements for CRT response also varies significantly according to the method used (range AUC pre-CRT QRSD 0.400-0.580, P < 0.05; AUC post-CRT QRSD 0.447-0.768, P < 0.05; AUC ΔQRSD 0.540-0.858, P < 0.05). Global QRSD measurements revealed lower variability compared to lead-specific QRSD. CONCLUSION: Different methods to measure QRSD yield not only different nominal values but also influence the value of QRSD in predicting CRT response. Measuring QRSD by a global method can help to standardize QRSD measurements in future studies.