Rapid ventricular tachycardia in patients with tetralogy of Fallot and implantable cardioverter-defibrillator: Insights from the DAI-T4F nationwide registry.

BACKGROUND: In repaired tetralogy of Fallot (TOF), little is known about characteristics of patients with rapid ventricular tachycardia (VT). Also, whether patients with a first episode of nonrapid VT may subsequently develop rapid VT or ventricular fibrillation (VF) has not been addressed. OBJECTIVES: The objectives of this study were to compare patients with rapid VT/VF with those with nonrapid VT and to assess the evolution of VT cycle lengths (VTCLs) overtime. METHODS: Data were analyzed from a nationwide registry including all patients with TOF and implantable cardioverter-defibrillator (ICD) since 2000. Patients with ≥1 VT episode with VTCL ≤250 ms (240 beats/min) formed the rapid VT/VF group. RESULTS: Of 144 patients (mean age 42.0 ± 12.7 years; 104 [72%] men), 61 (42%) had at least 1 VT/VF episode, including 28 patients with rapid VT/VF (46%), during a median follow-up of 6.3 years (interquartile range 2.2-10.3 years). Compared with patients in the nonrapid VT group, those in the rapid VT/VF group were significantly younger at ICD implantation (35.2 ± 12.6 years vs 41.5 ± 11.2 years; P = .04), had more frequently a history of cardiac arrest (8 [29%] vs 2 [6%]; P = .02), less frequently a history of atrial arrhythmia (11 [42%] vs 22 [69%]; P = .004), and higher right ventricular ejection fraction (43.3% ± 10.3% vs 36.6% ± 11.2%; P = .04). The median VTCL of VT/VF episodes was 325 ms (interquartile range 235-429 ms). None of the patients with a first documented nonrapid VT episode had rapid VT/VF during follow-up. CONCLUSION: Patients with TOF and rapid VT/VF had distinct clinical characteristics. The relatively low variation of VTCL over time suggests a room for catheter ablation without a backup ICD in selected patients with well-tolerated VT.

Sex Differences in Outcomes of Tetralogy of Fallot Patients With Implantable Cardioverter-Defibrillators.

BACKGROUND: Women with congenital heart disease at high risk for sudden cardiac death have been poorly studied thus far. OBJECTIVES: The aim of this study was to assess sex-related differences in patients with tetralogy of Fallot (TOF) and implantable cardioverter-defibrillators (ICDs). METHODS: Data were analyzed from the DAI-T4F (French National Registry of Patients With Tetralogy of Fallot and Implantable Cardioverter Defibrillator) cohort study, which has prospectively enrolled all patients with TOF with ICDs in France since 2010. Clinical events were centrally adjudicated by a blinded committee. RESULTS: A total of 165 patients (mean age 42.2 ± 13.3 years) were enrolled from 40 centers, including 49 women (29.7%). Among the 9,692 patients with TOF recorded in the national database, the proportion of women with ICDs was estimated to be 1.1% (95% CI: 0.8%-1.5%) vs 2.2% (95% CI: 1.8%-2.6%) in men (P < 0.001). The clinical profiles of patients at implantation, including the number of risk factors for ventricular arrhythmias, were similar between women and men. During a median follow-up period of 6.8 years (IQR: 2.5-11.4 years), 78 patients (47.3%) received at least 1 appropriate ICD therapy, without significant difference in annual incidences between women (12.1%) and men (9.9%) (HR: 1.22; 95% CI: 0.76-1.97; P = 0.40). The risk for overall ICD-related complications was similar in women and men (HR: 1.33; 95% CI: 0.81-2.19; P = 0.30), with 24 women (49.0%) experiencing at least 1 complication. CONCLUSIONS: Our findings suggest that women with TOF at high risk for sudden cardiac death have similar benefit/risk balance from ICD therapy compared with men. Whether ICD therapy is equally offered to at-risk women vs men warrants further evaluation in TOF as well as in other congenital heart disease populations. (French National Registry of Patients With Tetralogy of Fallot and Implantable Cardioverter Defibrillator [DAI-T4F]; NCT03837574).

Impact of Pulmonary Valve Replacement on Ventricular Arrhythmias in Patients With Tetralogy of Fallot and Implantable Cardioverter-Defibrillator.

OBJECTIVES: This study aimed to assess the impact of pulmonary valve replacement (PVR) on ventricular arrhythmias burden in a population of tetralogy of Fallot (TOF) patients with continuous cardiac monitoring by implantable cardioverter-defibrillators (ICDs). BACKGROUND: Sudden cardiac death is a major cause of death in TOF, and right ventricular overload is commonly considered to be a potential trigger for ventricular arrhythmias. METHODS: Data were analyzed from a nationwide French ongoing study (DAI-T4F) including all TOF patients with an ICD since 2000. Survival data with recurrent events were used to compare the burden of appropriate ICD therapies before and after PVR in patients who underwent PVR over the study period. RESULTS: A total of 165 patients (mean age 42.2 ± 13.3 years, 70.1% male) were included from 40 centers. Over a median follow-up period of 6.8 (interquartile range: 2.5 to 11.4) years, 26 patients (15.8%) underwent PVR. Among those patients, 18 (69.2%) experienced at least 1 appropriate ICD therapy. When considering all ICD therapies delivered before (n = 62) and after (n = 16) PVR, the burden of appropriate ICD therapies was significantly lower after PVR (HR: 0.21; 95% confidence interval [CI]: 0.08 to 0.56; p = 0.002). Respective appropriate ICD therapies rates per 100 person-years were 44.0 (95% CI: 35.7 to 52.5) before and 13.2 (95% CI: 7.7 to 20.5) after PVR (p < 0.001). In the overall cohort, PVR before ICD implantation was also independently associated with a lower risk of appropriate ICD therapy in primary prevention patients (HR: 0.29 [95% CI: 0.10 to 0.89]; p = 0.031). CONCLUSIONS: In this cohort of high-risk TOF patients implanted with an ICD, the burden of appropriate ICD therapies was significantly reduced after PVR. While optimal indications and timing for PVR are debated, these findings suggest the importance of considering ventricular arrhythmias in the overall decision-making process. (French National Registry of Patients With Tetralogy of Fallot and Implantable Cardioverter Defibrillator [DAI-T4F]; NCT03837574).

Long-Term Follow-Up of Patients With Tetralogy of Fallot and Implantable Cardioverter Defibrillator: The DAI-T4F Nationwide Registry.

BACKGROUND: Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart disease, and sudden cardiac death represents an important mode of death in these patients. Data evaluating the implantable cardioverter defibrillator (ICD) in this patient population remain scarce. METHODS: A Nationwide French Registry including all patients with tetralogy of Fallot with an ICD was initiated in 2010 by the French Institute of Health and Medical Research. The primary time to event end point was the time from ICD implantation to first appropriate ICD therapy. Secondary outcomes included ICD-related complications, heart transplantation, and death. Clinical events were centrally adjudicated by a blinded committee. RESULTS: A total of 165 patients (mean age, 42.2±13.3 years, 70.1% males) were included from 40 centers, including 104 (63.0%) in secondary prevention. During a median (interquartile range) follow-up of 6.8 (2.5-11.4) years, 78 (47.3%) patients received at least 1 appropriate ICD therapy. The annual incidence of the primary outcome was 10.5% (7.1% and 12.5% in primary and secondary prevention, respectively; P=0.03). Overall, 71 (43.0%) patients presented with at least 1 ICD complication, including inappropriate shocks in 42 (25.5%) patients and lead dysfunction in 36 (21.8%) patients. Among 61 (37.0%) patients in primary prevention, the annual rate of appropriate ICD therapies was 4.1%, 5.3%, 9.5%, and 13.3% in patients with, respectively, 0, 1, 2, or ≥3 guidelines-recommended risk factors. QRS fragmentation was the only independent predictor of appropriate ICD therapies (hazard ratio, 3.47 [95% CI, 1.19-10.11]), and its integration in a model with current criteria increased the 5-year time-dependent area under the curve from 0.68 to 0.81 (P=0.006). Patients with congestive heart failure or reduced left ventricular ejection fraction had a higher risk of nonarrhythmic death or heart transplantation (hazard ratio, 11.01 [95% CI, 2.96-40.95]). CONCLUSIONS: Patients with tetralogy of Fallot and an ICD experience high rates of appropriate therapies, including those implanted in primary prevention. The considerable long-term burden of ICD-related complications, however, underlines the need for careful candidate selection. A combination of easy-to-use criteria including QRS fragmentation might improve risk stratification. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03837574.

An Unusual Cause of Neonatal Heart Failure.

Hypertension is an important and under-recognized cause of acquired cardiomyopathy in newborns. Half the etiologies of neonatal hypertension are undetermined. We present a rare case of severe neonatal hypertension with ventricular dysfunction secondary to substance exposure during pregnancy. This case report emphasizes the importance of a well-focused prenatal history on maternal medications and substance use.

Implantable cardiac defibrillator among adults with transposition of the great arteries and atrial switch operation: case series and review of literature.

BACKGROUND: The experience with the implantable cardiac defibrillator (ICD) in patients with transposition of the great arteries (TGA) and history of atrial switch surgery remains limited. METHODS: Retrospective evaluation aiming to assess characteristics and outcomes of consecutive TGA patients with history of atrial switch surgery implanted with an ICD between January 2005 and June 2012 in four French centers. RESULTS: Of the 12 patients (median 34 years [28, 40]; 67% male), 4 patients (33%) were implanted for secondary prevention after symptomatic documented sustained ventricular tachycardia or sudden cardiac arrest. ICDs were implanted for primary prevention in 8 patients (67%), including cardiac resynchronization in 3 patients; severe systemic ventricle dysfunction was present in all cases (median ejection fraction 27% [20, 40]). Overall, one patient died during the ICD implantation secondary to refractory cardiac arrest after defibrillation testing. Over a median follow-up of 19 months [10, 106], 6 patients out of 11 (54%) experienced worsening of congestive heart failure, including 5 who were eventually transplanted. Overall, 3 patients (27%) experienced significant ICD-related complications, whereas only one patient (primary prevention indication) developed appropriate ICD therapy (successful anti-tachycardia pacing without shock). Half of the patients presented with at least one episode of sustained (≥ 5 min) atrial arrhythmia during follow-up. CONCLUSIONS: Our findings underline the key role of progressive heart failure in dictating outcomes among TGA patients with prior atrial switch repair. Our results also underline the need of better risk-stratification for sudden cardiac death in those patients.

Noninvasive electrocardiographic mapping to improve patient selection for cardiac resynchronization therapy: beyond QRS duration and left bundle branch block morphology.

OBJECTIVES: This study sought to investigate whether noninvasive electrocardiographic activation mapping is a useful method for predicting response to cardiac resynchronization therapy (CRT). BACKGROUND: One third of the patients appear not to respond to CRT when they are selected according to QRS duration. METHODS: We performed electrocardiographic activation mapping in 33 consecutive CRT candidates (QRS duration ≥120 ms). In 18 patients, the 12-lead electrocardiographic morphology was left bundle branch block (LBBB), and in 15, it was nonspecific intraventricular conduction disturbance (NICD). Three indexes of electrical dyssynchrony were derived from intrinsic maps: right and left ventricular total activation times and ventricular electrical uncoupling (VEU) (difference between the left ventricular [LV] and right ventricular mean activation times). We assessed the ability of these parameters to predict response, measured using a clinical composite score, after 6 months of CRT. RESULTS: Electrocardiographic maps revealed homogeneous patterns of activation and consistently greater VEU and LV total activation time (LVTAT) in patients with LBBB compared with heterogeneous activation sequences and shorter VEU and LVTAT in NICD patients (VEU: 75 ± 12 ms vs. 40 ± 22 ms; p < 0.001; LVTAT: 115 ± 21 ms vs. 91 ± 34 ms; p = 0.03). LBBB and NICD patients had similar right ventricular total activation times (62 ± 30 ms vs. 58 ± 26 ms; p = 0.7). The area under the receiver-operating characteristic curve indicated that VEU (area under the curve [AUC]: 0.88) was significantly superior to QRS duration (AUC: 0.73) and LVTAT (AUC: 0.72) for predicting CRT response (p < 0.05). With a 50-ms cutoff value, VEU identified CRT responders with 90% sensitivity and 82% specificity whether LBBB was present or not. CONCLUSIONS: Ventricular electrical uncoupling measured by electrocardiographic mapping predicted clinical CRT response better than QRS duration or the presence of LBBB.

Comparison of different invasive hemodynamic methods for AV delay optimization in patients with cardiac resynchronization therapy: implications for clinical trial design and clinical practice.

BACKGROUND: Reproducibility and hemodynamic efficacy of optimization of AV delay (AVD) of cardiac resynchronization therapy (CRT) using invasive LV dp/dtmax are unknown. METHOD AND RESULTS: 25 patients underwent AV delay (AVD) optimisation twice, using continuous left ventricular (LV) dp/dtmax, systolic blood pressure (SBP) and pulse pressure (PP). We compared 4 protocols for comparing dp/dtmax between AV delays: We assessed for dp/dtmax, LVSBP and LVPP, test-retest reproducibility of the optimum. Optimization using immediate absolute dp/dtmax had poor reproducibility (SDD of replicate optima=41 ms; R(2)=0.45) as did delayed absolute (SDD 39 ms; R(2)=0.50). Multiple relative had better reproducibility: SDD 23 ms, R(2)=0.76, and (p<0.01 by F test). Compared with AAI pacing, the hemodynamic increment from CRT, with the nominal AV delay was LVSBP 2% and LVdp/dtmax 5%, while CRT with pre-determined optimal AVD gave 6% and 9% respectively. CONCLUSIONS: Because of inevitable background fluctuations, optimization by absolute dp/dtmax has poor same-day reproducibility, unsuitable for clinical or research purposes. Reproducibility is improved by comparing to a reference AVD and making multiple consecutive measurements. More than 6 measurements would be required for even more precise optimization--and might be advisable for future study designs. With optimal AVD, instead of nominal, the hemodynamic increment of CRT is approximately doubled.

Acute hemodynamic benefits of biventricular and single-site systemic ventricular pacing in patients with a systemic right ventricle.

BACKGROUND: Patients treated by atrial redirection surgery (Senning or Mustard procedure) for transposition of the great arteries (TGA) have an important risk for heart failure caused by dysfunction of the systemic right ventricle. Conventional nonsystemic ventricular pacing (non-systVP) may even further increase this risk. OBJECTIVE: We investigated the effects of endocardial non-systVP, biventricular pacing (BiVP), and single-site systemic ventricular pacing (systVP) on systolic cardiac pump function in patients with TGA and status post atrial redirection surgery (SenningMustardTGA). METHODS: During clinically indicated catheterization in 9 patients with SenningMustardTGA, endocardial ventricular stimulation (overdrive DDD mode; 80-90 beats/min) was applied with temporary pacing leads at the nonsystemic and the systemic ventricle. Acute changes in the maximal rate of pressure rise (dP/dtmax) and systolic pressure of the systemic ventricle, as induced by non-systVP, systVP, and BiVP compared to reference, were assessed with a pressure wire within the systemic ventricle. Reference was AAI pacing with a similar heart rate (n = 7) or non-systVP at a lower heart rate than that during stimulation at experimental sites (85 beats/min vs 90 beats/min; n = 2). RESULTS: Systemic dP/dtmax and systolic ventricular pressure were significantly higher during systVP (+15.6% and +5.1%, respectively) and BiVP (+14.3% and +4.9%, respectively, compared with non-systVP). In 6 of 7 patients, systemic dP/dtmax was higher during BiVP and systVP than during AAI pacing. CONCLUSIONS: In a population of patients with SenningMustardTGA, acute hemodynamic effects of endocardial systVP and BiVP were significantly and equally better than those of non-systVP. In some patients, systVP and BiVP might even be better than ventricular activation by the intrinsic conduction system.

Permanent cardiac pacing in children: choosing the optimal pacing site: a multicenter study.

BACKGROUND: We evaluated the effects of the site of ventricular pacing on left ventricular (LV) synchrony and function in children requiring permanent pacing. METHODS AND RESULTS: One hundred seventy-eight children (aged <18 years) from 21 centers with atrioventricular block and a structurally normal heart undergoing permanent pacing were studied cross-sectionally. Median age at evaluation was 11.2 (interquartile range, 6.3-15.0) years. Median pacing duration was 5.4 (interquartile range, 3.1-8.8) years. Pacing sites were the free wall of the right ventricular (RV) outflow tract (n=8), lateral RV (n=44), RV apex (n=61), RV septum (n=29), LV apex (n=12), LV midlateral wall (n=17), and LV base (n=7). LV synchrony, pump function, and contraction efficiency were significantly affected by pacing site and were superior in children paced at the LV apex/LV midlateral wall. LV dyssynchrony correlated inversely with LV ejection fraction (R=0.80, P=0.031). Pacing from the RV outflow tract/lateral RV predicted significantly decreased LV function (LV ejection fraction <45%; odds ratio, 10.72; confidence interval, 2.07-55.60; P=0.005), whereas LV apex/LV midlateral wall pacing was associated with preserved LV function (LV ejection fraction ≥55%; odds ratio, 8.26; confidence interval, 1.46-47.62; P=0.018). Presence of maternal autoantibodies, gender, age at implantation, duration of pacing, DDD mode, and QRS duration had no significant impact on LV ejection fraction. CONCLUSIONS: The site of ventricular pacing has a major impact on LV mechanical synchrony, efficiency, and pump function in children who require lifelong pacing. Of the sites studied, LV apex/LV midlateral wall pacing has the greatest potential to prevent pacing-induced reduction of cardiac pump function.

Biventricular pacing in patients with Tetralogy of Fallot: non-invasive epicardial mapping and clinical impact.

INTRODUCTION: Patients who have undergone repair of Tetralogy of Fallot (TOF) often present with right bundle branch block. Cardiac resynchronization therapy (CRT) with right ventricular (RV) or biventricular (BiV) stimulation has been proposed as a modality to correct electrical abnormalities and improve cardiac contractility in patients with repaired TOF. We aimed to 1) compare ventricular electrical activation in adults with repaired TOF during RV versus BiV stimulation, using a non-invasive epicardial mapping system, and 2) examine the clinical mid-term effects of BiV resynchronization. METHODS: 9 adults with repaired TOF were implanted with a CRT system and underwent 1) a non-invasive epicardial mapping (n=9) during sinus intrinsic rhythm, RV and BiV pacing 2) a clinical evaluation (n=7) before and after 6 months CRT with assessment of NYHA class and exercise capacity. RESULTS: During intrinsic rhythm, non-invasive mapping demonstrated delayed activation of the right compared with the left ventricle in all patients, with the greatest activation delay noted near the infundibulum. However, we observed important differences among patients, in the severity of activation delays. Global activation time and an index of dyssynchrony were improved (p<0.05) during BiV pacing compared with RV pacing and spontaneous rhythm. BiV pacing increased (p<0.05) exercise tolerance and lowered the mean NYHA functional class at 6 months of follow up. CONCLUSION: Patients with corrected TOF present with different patterns of ventricular activation. RV stimulation modestly improved RV activation sequence and was associated with a delayed LV activation. Biventricular stimulation significantly decreased right and left ventricular dyssynchrony.

The role of echocardiography in the assessment of right ventricular systolic function in patients with transposition of the great arteries and atrial redirection.

BACKGROUND: Although dysfunction of the systemic right ventricle (RV) in patients with complete transposition of the great arteries (TGA) after atrial redirection by Mustard or Senning procedures is well recognized, there are few data on systemic RV geometry and function. Echocardiography is a widely available imaging technique that is particularly suitable for clinical follow-up because of its non-invasive nature, low cost and lack of ionizing radiation. AIM: To examine the feasibility and variability of transthoracic echocardiography variables in the assessment of the systemic RV. METHODS: Multivariable transthoracic echocardiographic analysis, including assessment of global function variables (RV ejection fraction [RVEF; Simpson's method], RV fractional shortening [RVFS] and dP/dt), longitudinal function variables (tricuspid annular plane systolic excursion [TAPSE], peak systolic velocity at the junction of the RV free wall and the tricuspid annulus, assessed with pulsed tissue Doppler imaging [S' TDI]), tricuspid regurgitation and asynchrony, was performed in 35 consecutive patients with TGA after atrial redirection. Functional variables were compared with magnetic resonance imaging (MRI). Inter- and intraobserver echocardiographic analysis variability was assessed in ten randomly selected cases. RESULTS: Global and longitudinal function variables were not correlated with RVEF calculated by MRI, except for S' TDI, which was weakly correlated (P = 0.02, r = 0.37). Asynchrony assessment was feasible in all patients. Inter- and intraobserver echocardiographic analysis variability was high for RVEF, RVFS and dP/dt (> 10%), and low for TAPSE and S' TDI (5%). CONCLUSION: Owing to geometric changes, presumed contractility pattern shift and retrosternal position, conventional echocardiographic variables are not relevant for RV function assessment. Assessment of asynchrony and tricuspid regurgitation is easily feasible in routine practice and highly reproducible. Echocardiography does not permit complete assessment of the systemic RV after atrial redirection but is fully complementary with MRI and should not be abandoned. Future improvements in transducers and dedicated software should permit major improvements in the near future.

Syncope in Brugada syndrome patients: prevalence, characteristics, and outcome.

BACKGROUND: The report from the 2nd Consensus Committee on BrS suggests that all patients with syncope without a "clear extracardiac cause" should have an implantable cardioverter-defibrillator (ICD). However, a clear extracardiac cause for syncope may be difficult to prove. OBJECTIVE: The purpose of this study was to characterize syncope in patients with Brugada syndrome (BrS). METHODS: All patients diagnosed with BrS at our institution between 1999 and 2010 were enrolled in a prospective registry. Patients with suspected arrhythmic syncope (group 1) were compared to patients with nonarrhythmic syncope (group 2) and to patients with syncope of doubtful origin (group 3). RESULTS: Of 203 patients with BrS, 57 (28%; 44 male, age 46 ± 12 years) experienced at least 1 syncope. Group 1 consisted of 23 patients, all of whom received an ICD. In group 2 (17 patients), 3 received an ICD because of a positive electrophysiologic study. In group 3 (17 patients), 6 received an implantable loop recorder and 6 received an ICD. After mean follow-up of 65 ± 42 months, 14 patients in group 1 remained asymptomatic, 4 had recurrent syncope, and 6 had appropriate ICD therapy. In group 2, 9 patients remained asymptomatic and 7 had recurrent neurocardiogenic syncope. In group 3, 7 remained asymptomatic and 9 had recurrent syncope. One patient from each group died from a noncardiac cause. CONCLUSION: In the present study, syncope occurred in 28% of patients with BrS. The ventricular arrhythmia rate was 5.5% per year in group 1. In 30%, the etiology of the syncope was questionable. No sudden cardiac death occurred in groups 2 and 3.

Effects of nonsystemic ventricular pacing in patients with transposition of the great arteries and atrial redirection.

INTRODUCTION: Ventricular pacing may add additional risk for right ventricular (RV) dysfunction in patients with transposition of the great arteries (TGA) and atrial redirection. The aim of our study was to evaluate the effects of long-term nonsystemic ventricular pacing on cardiac function, dyssynchrony, and clinical performance in patients with systemic RV. METHODS AND RESULTS: Forty-six adults with TGA and atrial redirection, of whom 11 were permanently paced at the nonsystemic ventricle, underwent assessment of clinical status and exercise stress testing, as well as echocardiography to assess parameters of RV function and dyssynchrony. In paced patients, median NYHA functional class was II, which was significantly higher than in nonpaced patients (median class I; P = 0.002). Maximum performance and peak oxygen consumption on exercise testing were significantly lower in paced patients when compared with nonpaced patients (100 ± 30 vs 120 ± 32 W and 22 ± 6 vs 27 ± 7 mLO(2)/kg/min, respectively; P < 0.05 for both). On echocardiography, RV shortening fraction (27 ± 11 vs 33 ± 10%), RV ejection fraction (39 ± 7 vs 44 ± 10%) and RV dP/dt(max) (891 ± 470 vs 1,024 ± 318 mmHg/s) were significantly lower (P < 0.05 for all) in paced versus nonpaced patients. Inter- and intraventricular dyssynchrony was most pronounced in the paced group (99 ± 10 vs 25 ± 9 ms and 70 ± 29 vs 21 ± 15 ms, respectively; P < 0.001 for both). CONCLUSIONS: Long-term pacing of the nonsystemic ventricle in patients with atrial switch for TGA was associated with significantly impaired functional status, exercise capacity, and systemic ventricular function.

Acute hemodynamic response to biventricular pacing in heart failure patients with narrow, moderately, and severely prolonged QRS duration.

BACKGROUND: The efficacy of biventricular (BiV) pacing in patients with a narrow or moderately prolonged QRS duration remains questionable. OBJECTIVE: To assess the hypothesis that electrical dyssynchrony is required to obtain hemodynamic benefit from BiV pacing by investigating the relationship between intrinsic QRS duration and hemodynamic response to BiV pacing in a patient population covering a broad spectrum of QRS duration. METHODS: Eighty-two consecutive heart failure patients underwent cardiac resynchronization therapy implantation irrespective of their QRS duration. Thirty-four patients had a narrow QRS duration (<120 ms), whereas 11 patients had a moderately prolonged QRS duration (≥120 to <150 ms) and 37 patients had a severely prolonged QRS duration (≥150 ms). After implantation, invasive left ventricular (LV) dP/dt measurements were compared between intrinsic rhythm and simultaneous BiV pacing with an optimized atrioventricular delay. RESULTS: A high correlation (r = .65; P < .001) was observed between baseline QRS duration and changes in LV dP/dt(max) induced by BiV pacing. BiV pacing was ineffective in patients with a narrow QRS duration (+0.4% ± 6.1%; P = ns). No significant increase in LV dP/dt(max) was observed in patients with a QRS duration of ≥120 to <150 ms (+4.4% ± 6.9%; P = .06), whereas patients with a QRS duration of ≥150 ms exhibited a significant increase in LV dP/dt(max) (+17.1% ± 13.4%; P <.001). Only 9% of the patients with a narrow QRS duration exhibited a ≥10% increase in LV dP/dt(max). CONCLUSIONS: Baseline QRS duration is linearly related to acute hemodynamic response to BiV pacing. Patients with a narrow QRS duration do not derive hemodynamic improvement. This improvement is also limited in patients with a moderately prolonged QRS duration, raising questions about the potential clinical benefit of this therapy in these patients.

Validation of an animal model of right ventricular dysfunction and right bundle branch block to create close physiology to postoperative tetralogy of Fallot.

BACKGROUND: In the past 5 years a few number of studies and case reports have come out focusing on biventricular (BiV) stimulation for treatment of congenital heart disease related ventricular dysfunction. The few available studies include a diverse group of pathophysiological entities ranging from a previously repaired tetralogy of Fallot (TOF) to a functional single ventricle anatomy. Patient's status is too heterogeneous to build important prospective study. To well understand the implication of prolonged electromechanical dyssynchrony we performed a chronic animal model that mimics essential parameters of postoperative TOF. METHODS: Significant pulmonary regurgitation, mild stenosis, as well as right ventricular outflow tract (RVOT) scars were induced in 15 piglets to mimic repaired TOF. 4 months after hemodynamics and dyssynchrony parameters were compared with a control group and with a population of symptomatic adult with repaired TOF. RESULTS: Comparing the animal model with the animal control group on echocardiography, RV dilatation, RV and LV dysfunction, broad QRS complex and dyssynchrony were observed on the animal model piglets. Moreover, epicardial electrical mapping showed activation consistent with a right bundle branch block. The animal models displayed the same pathophysiological parameters as the post TOF repair patients in terms of QRS duration, pulmonary regurgitation biventricular dysfunction and dyssynchrony. CONCLUSION: This chronic swine model mimics electromechanical ventricular activation delay, RV and LV dysfunction, as in adult population of repair TOF. It does appear to be a very useful and interesting model to study the implication of dyssynchrony and the interest of resynchronization therapy in TOF failing ventricle.

Reliability and reproducibility of QRS duration in the selection of candidates for cardiac resynchronization therapy.

BACKGROUND: A QRS >120 ms remains the recommended criterion for the selection of cardiac resynchronization therapy (CRT) candidates. However, the reproducibility of this measurement has not been studied thoroughly. METHODS: QRS duration was measured by 3 experienced cardiologists and by automatic measurement on 228 electrocardiograms (ECGs) randomly collected from 188 subjects, including neonates, healthy adults, patients with complete and incomplete bundle branch block, and CRT candidates. All ECGs were recorded at a 25 mm/s sweep speed. Forty recordings were duplicated and 50 ECGs were recorded at both 25 and 50 mm/s. RESULTS: Significant interobserver differences (P < 0.001) were found between each combination of paired observers, with an up to 50-ms absolute variability between cardiologists and low concordance with computerized measurements. Intraobserver absolute variability was also significant (P < 0.01) for the 3 observers. These significant differences persisted (P < 0.01) when focusing our interest on the ECGs in the 100-140 ms range (defined as at least one out of the 4 measures in this range). Considering the 120 ms limit, 22 (27.5%) ECGs were differently classified by at least one of the cardiologists. We observed similar interobserver differences between each combination of paired observers with a 50 mm/s sweep speed. CONCLUSION: Manual QRS duration measurements were associated with significant inter- and intraobserver variability and low concordance with computerized measurements. The measurement of QRS is, therefore, operator-dependent and a reevaluation of the measurement methods may be essential to develop clinical and investigative standards.