Current State of Cardiac Implantable Electronic Device Remote Monitoring in Pediatrics and Congenital Heart Disease: A PACES-Sponsored Quality Improvement Initiative.

Cardiac implantable electronic device (CIED) remote transmissions are an integral part of longitudinal follow-up in pediatric and adult congenital heart disease (ACHD) patients. To evaluate baseline CIED remote monitoring (RM) data among pediatric and ACHD centers prior to implementation of a Pediatric and Congenital Electrophysiology  Society (PACES)-sponsored quality improvement (QI) project. This is a cross-sectional study of baseline CIED RM. Centers self-reported baseline data: individual center RM compliance was defined as high if there was > 80% achievement and low if < 50%. A total of 22 pediatric centers in the USA and Australia submitted baseline data. Non-physicians were responsible for management of the RM program in most centers: registered nurse (36%), advanced practice provider (27%), combination (23%), and third party (9%). Fifteen centers (68%) reported that > 80% of their CIED patients are enrolled in RM and only two centers reported < 50% participation. 36% reported high compliance of device transmission within 14 days of implant and 77% of centers reported high compliance of CIED patients enrolled in RM. The number of centers achieving high compliance differed by device type: 36% for pacemakers, 50% for ICDs, and 55% for Implantable Cardiac Monitors (ICM). All centers reported at least 50% adherence to recommended follow-up for PM and ICD, with 23% low compliance rate for ICMs. Based on this cross-sectional survey of pediatric and ACHD centers, compliance with CIED RM is sub-optimal. The PACES-sponsored QI initiative will provide resources and support to participating centers and repeat data will be evaluated after PDSA cycles.

High Acuity Therapy Variation Across Pediatric Acute Care Cardiology Units: Results from the Pediatric Acute Care Cardiology Collaborative Hospital Surveys.

We utilized the multicenter Pediatric Acute Care Cardiology Collaborative (PAC3) 2017 and 2019 surveys to describe practice variation in therapy availability and changes over a 2-year period. A high acuity therapies (ATs) score was derived (1 point per positive response) from 44 survey questions and scores were compared to center surgical volume. Of 31 centers that completed the 2017 survey, 26 also completed the 2019 survey. Scores ranged from 11 to 34 in 2017 and 11 to 35 in 2019. AT scores in 2019 were not statistically different from 2017 scores (29/44, IQR 27-32.5 vs. 29.5/44, IQR 27-31, p = 0.9). In 2019, more centers reported initiation of continuous positive airway pressure (CPAP) and Bi-level positive airway pressure (BiPAP) in Acute Care Cardiology Unit (ACCU) (19/26 vs. 4/26, p < 0.001) and permitting continuous CPAP/BiPAP (22/26 vs. 14/26, p = 0.034) compared to 2017. Scores in both survey years were significantly higher in the highest surgical volume group compared to the lowest, 33 ± 1.5 versus 25 ± 8.5, p = 0.046 and 32 ± 1.7 versus 23 ± 5.5, p = 0.009, respectively. Variation in therapy within the ACCUs participating in PAC3 presents an opportunity for shared learning across the collaborative. Experience with PAC3 was associated with increasing available respiratory therapies from 2017 to 2019. Whether AT scores impact the quality and outcomes of pediatric acute cardiac care will be the subject of further investigation using a comprehensive registry launched in early 2019.

The added value of the advanced practice provider in paediatric acute care cardiology.

OBJECTIVES: Advanced practice providers (APPs) are being employed at increasing rates in order to meet new in-hospital care demands. Utilising the Paediatric Acute Care Cardiology Collaborative (PAC3) hospital survey, we evaluated variations in staffing models regarding first-line providers and assessed associations with programme volume, acuity of care, and post-operative length of stay (LOS). STUDY DESIGN: The PAC3 hospital survey defined staffing models and resource availability across member institutions. A resource acuity score was derived for each participating acute care cardiology unit. Surgical volume was obtained from The Society of Thoracic Surgeons database. Pearson's correlation coefficients were used to evaluate the relationship between staffing models and centre volume as well as unit acuity. A previously developed case-mix adjustment model for total post-operative LOS was utilised in a multinomial regression model to evaluate the association of APP patient coverage with observed-to-expected post-operative LOS. RESULTS: Surveys were completed by 31 (91%) PAC3 centres in 2017. Nearly all centres (94%) employ APPs, with a mean of 1.7 (range 0-5) APPs present on weekday rounds. The number of APPs present has a positive correlation with surgical volume (r = 0.49, p < 0.01) and increased acuity (r = 0.39, p = 0.03). In the multivariate model, as coverage by APPs increased from low to moderate or high, there was greater likelihood of having a shorter-than-expected post-operative LOS (p < 0.001). CONCLUSIONS: The incorporation of paediatric acute care cardiology APPs is associated with reduced post-operative LOS. Future studies are necessary to understand how APPs impact these patient-specific outcomes.

22q11.2 Deletion Status and Perioperative Outcomes for Tetralogy of Fallot with Pulmonary Atresia and Multiple Aortopulmonary Collateral Vessels.

Deletion of 22q11.2 (del22q11) is associated with adverse outcomes in patients with tetralogy of Fallot (TOF). We sought to investigate its contribution to perioperative outcome in patients with a severe form of TOF characterized by pulmonary atresia (PA) or severe pulmonary stenosis (PS) and major aortopulmonary collateral arteries (MAPCAS). We conducted a retrospective review of patients with TOF/MAPCAS who underwent staged surgical reconstruction between 1995 and 2006. Groups were compared according to 22q11.2 deletion status using t-tests or the Wilcoxon Rank sum test. We included 26 subjects, 24 of whom survived the initial operation. Of those, 21 subjects had known deletion status and constitute the group for this analysis [15 with no deletion present (ND) and 6 del22q11 subjects]. There was no difference with respect to occurrence of palliative procedure prior to initial operation, or to timing of closure of the ventricular septal defect (VSD). Other than higher prevalence of prematurity (50%) in the del22q11 group versus no prematurity in the ND, the groups were comparable in terms of pre-operative characteristics. The intra- and post-operative course outcomes (length of cardiopulmonary bypass, use of vasopressors, duration of intensive care and length of hospital stay, tube-feeding) were also comparable. Although the del22q11 had longer mechanical ventilation than the ND, this difference was not significant [68 h (range 4-251) vs. 45 h (range 3-1005), p = 0.81]. In this detailed comparison of a small patient cohort, 22q11.2 deletion syndrome was not associated with adverse perioperative outcomes in patients with TOF, PA, and MAPCAS when compared to those without 22q11.2 deletion syndrome. These results are relevant to prenatal and neonatal pre-operative counseling and planning.

Perioperative Factors Influence the Long-Term Outcomes of Children and Adolescents with Repaired Tetralogy of Fallot.

Tetralogy of Fallot (TOF) often carries long-term seqüelae following surgical intervention. We hypothesized that early perioperative factors are associated with long-term adverse right ventricular (RV) remodeling, diminished exercise capacity, and increased morbidity. We conducted a retrospective cohort study of patients operated for TOF that underwent cardiac magnetic resonance imaging study (CMR), exercise stress test (EST), and detailed review of past medical history. Outcome variables included measures of RV size, and function, maximal work rate, and oxygen consumption, and interim hospitalizations, surgeries, and catheterizations. Thirty-nine subjects were included. Age at surgical repair was 0.3 ± 0.3 years and age at testing was 9.7 ± 1.4 years. On CMR, there was borderline RV dilation with moderate pulmonary insufficiency (PI) [RF 32% (8; 43)] and normal RV ejection fraction [60% (55; 67)]. On EST, there was low percent-predicted maximal oxygen consumption (77 ± 20%), and percent-predicted maximal work rate (84 ± 23%). On multivariable analysis, mechanical ventilation and Blalock-Taussig (BT) shunt prior to complete surgical repair were associated with the number of future hospitalizations. Duration of cardiopulmonary bypass and prior BT shunt were associated with future catheterizations. Prior BT shunt was a predictor of worse RVEF, while duration of mechanical ventilation and use of transannular patch were predictors of worse PI. Longer duration of mechanical ventilation (or LOS) was associated with worse maximal work rate. Surgical and perioperative factors may portend long-term RV remodeling and outcome in TOF. Further studies are warranted to explore these associations and potential underlying mechanisms.

Collective quality improvement in the paediatric cardiology acute care unit: establishment of the Pediatric Acute Care Cardiology Collaborative (PAC3).

Collaborative quality improvement and learning networks have amended healthcare quality and value across specialities. Motivated by these successes, the Pediatric Acute Care Cardiology Collaborative (PAC3) was founded in late 2014 with an emphasis on improving outcomes of paediatric cardiology patients within cardiac acute care units; acute care encompasses all hospital-based inpatient non-intensive care. PAC3 aims to deliver higher quality and greater value care by facilitating the sharing of ideas and building alignment among its member institutions. These aims are intentionally aligned with the work of other national clinical collaborations, registries, and parent advocacy organisations. The mission and early work of PAC3 is exemplified by the formal partnership with the Pediatric Cardiac Critical Care Consortium (PC4), as well as the creation of a clinical registry, which links with the PC4 registry to track practices and outcomes across the entire inpatient encounter from admission to discharge. Capturing the full inpatient experience allows detection of outcome differences related to variation in care delivered outside the cardiac ICU and development of benchmarks for cardiac acute care. We aspire to improve patient outcomes such as morbidity, hospital length of stay, and re-admission rates, while working to advance patient and family satisfaction. We will use quality improvement methodologies consistent with the Model for Improvement to achieve these aims. Membership currently includes 36 centres across North America, out of which 26 are also members of PC4. In this report, we describe the development of PAC3, including the philosophical, organisational, and infrastructural elements that will enable a paediatric acute care cardiology learning network.

Success rates in pediatric WPW ablation are improved with 3-dimensional mapping systems compared with fluoroscopy alone: a multicenter study.

INTRODUCTION: Three-dimensional mapping (3-D) systems are frequently used for ablation of supraventricular tachycardia. Prior studies have demonstrated radiation dosage reduction with 3-D, but there are no data on whether 3-D improves the efficacy of ablation of Wolff-Parkinson-White syndrome (WPW). We sought to determine if 3-D improves the success rate for ablation of WPW in children. METHODS: Multicenter retrospective study including patients ≤21 years of age with WPW undergoing ablation from 2008 to 2012. Success rates using the 2 techniques (3-D vs. fluoroscopy alone [FLUORO]) were compared. RESULTS: Six hundred and fifty-one cases were included (58% male, mean age 13 ± 4 years, 366 [56%] 3-D). Baseline characteristics including gender, weight, accessory pathway (AP) location, number of APs, and repeat ablation attempts were similar between the 2 groups (3-D and FLUORO) The 3-D group was slightly younger (12.7 ± 4.0 vs. 13.3 ± 4.0 years; P = 0.04) and less likely to undergo ablation utilizing cryoenergy (38 [10%] vs. 56 [20%]; P < 0.01). The 3-D group had a higher acute success rate of ablation (355 [97%] vs. 260 [91%]; P < 0.01). No differences were seen in recurrence (16 [5%] vs. 26 [9%]; P = 0.09) or complication rates (1 [0.3%] vs. 1 [0.4%]; P = 0.86) between the groups. On multivariable analysis, 3-D was shown to significantly improve success at ablation with an odds ratio of 3.1 (95% CI 1.44-6.72; P < 0.01). CONCLUSIONS: Use of 3-D significantly improved success rates for ablation of WPW in children. The increase in acute success associated with 3-D suggests it is an important adjunct for catheter ablation of WPW in children.

Verapamil-sensitive idiopathic left ventricular tachycardia in a 6-month-old: unique considerations in diagnosis and management in an infant.

Idiopathic left ventricular tachycardia of the Belhassen type is rare in infants. We present a 6-month-old infant girl with a wide-complex tachycardia with right bundle branch block QRS morphology, a superior axis, and atrioventricular dissociation, consistent with a left anterior fascicular tachycardia. Initial echocardiogram revealed depressed ventricular function. The tachycardia was unresponsive to therapeutic trials of adenosine, esmolol, procainamide, and lidocaine. There was brief conversion of the tachycardia to sinus rhythm with transesophageal atrial overdrive pacing, suggesting a reentrant mechanism of the arrhythmia. Ultimately, the judicious administration of intravenous verapamil resulted in termination of the arrhythmia, which has been sustained on oral therapy.

The fate of nontargeted endocardial leads during the extraction of one or more targeted leads in pediatrics and congenital heart disease.

INTRODUCTION: Extraction of targeted endocardial leads can lead to inadvertent damage or dislodgement of nontargeted leads, though the frequency of this has not been reported in pediatrics and congenital heart disease (CHD). METHODS: This is a retrospective review of lead extraction procedures from 2002 to 2010 from two pediatric and CHD centers evaluating unplanned interventions on nontargeted leads during the extraction of one or more targeted leads. RESULTS: Nontargeted leads were present in the 22 lead extraction procedures performed on 20 patients with median age 15 years (interquartile range, 11.5-18.5 years): 11 (55%) with structurally normal hearts and nine (45%) with CHD. Twenty of 23 targeted leads (86%) were extracted with complete success. Of the 22 nontargeted leads, including 17 atrial leads and five ventricular leads, seven (32%) required further intervention including: five extracted due to damage, dislodgement, or change in device location; one abandoned due to damage; and one dislodged requiring a second procedure for repositioning. The remaining 15 nontargeted leads (68%) were unharmed. Nontargeted leads requiring further intervention had a shorter lead duration in situ (median 2 years, interquartile range 0.5-3.5 years) than unharmed nontargeted leads (median 6.6 years, interquartile range 4.1-9.1 years; P = 0.01). Age at extraction, CHD, implantable cardioverter defibrillator leads, atrial lead position, or primary extraction modality did not predict further intervention for nontargeted leads. Major complications occurred in one procedure (4.5%) with no deaths. CONCLUSIONS: In pediatrics and CHD, nontargeted leads are frequently damaged or dislodged during the extraction of targeted leads. The risk of lead damage or dislodgement has implications for procedural planning and counseling for patients and families of pediatric and CHD patients requiring lead extraction.

Morbidity in children and adolescents after surgical correction of interrupted aortic arch.

Previous studies of outcome after operative correction of interrupted aortic arch (IAA) have focused on mortality and rates of reintervention. We sought to investigate the clinical status of children and adolescents after surgery for IAA. A cross-sectional study of subjects with IAA between the ages of 8 and 18 years was performed with the subjects undergoing simultaneous genetic testing, electrocardiogram, cardiac magnetic resonance imaging, cardiopulmonary exercise testing, and assessment of health status and health-related quality of life as well as concurrent retrospective cohort study reviewing their postoperative use of medical care, including operative and transcatheter reinterventions, noncardiac surgeries, and hospitalizations. Twenty-one subjects with IAA with median age of 9 years were studied. Reintervention rates were 38% for left-ventricular outflow tract, 33% for AA, and 24% for both. Rates of reintervention were highest in the first year of life and decreased in subsequent years. Left-ventricular ejection fraction was preserved (72 ± 6%). Maximal oxygen consumption, maximal work, and forced vital capacity were both significantly decreased from age and sex norms (p < 0.0001). Health status and quality of life were both severely decreased. Subjects with IAA demonstrate a significant burden of operative and transcatheter intervention and large magnitude deficits in exercise performance, health status, and health-related quality of life.

Morbidity in children and adolescents after surgical correction of truncus arteriosus communis.

BACKGROUND: Studies of outcome after operative correction of truncus arteriosus communis (TA) have focused on mortality and rates of reintervention. We sought to investigate the clinical status of children and adolescents with surgically corrected TA. METHODS AND RESULTS: A cross-sectional study of subjects with TA was performed. Subjects underwent concurrent genetic testing, electrocardiogram, cardiac magnetic resonance imaging, cardiopulmonary exercise testing, and completed questionnaires assessing health status and health-related quality of life. Review of their medical history provided retrospective information on cardiac reintervention and use of medical care. Twenty-five subjects with a median age of 11.8 (8.1-18.99) years were enrolled. The prevalence of 22q11.2 deletion was 32%. Incidence of hospitalization, cardiac reintervention, and noncardiac operations was highest in the first year of life. Combined catheter-based and operative reintervention rates were 52% on the conduit and 56% on the pulmonary arteries. Right ventricular ejection fraction and end-diastolic volume were normal. Moderate or greater truncal valve insufficiency was seen in 11% of subjects, and truncal valve replacement occurred in 8% of subjects. Maximal oxygen consumption (P = .0002), maximal work (P < .0001), and forced vital capacity (P < .0001) were all lower than normal for age and sex. Physical health status and health-related quality of life were both severely diminished. CONCLUSION: Patients with TA demonstrate significant comorbid disease throughout childhood, significant burden of operative and catheter-based reintervention, and deficits in exercise performance, functional status, and health-related quality of life.

Diagnosis and ablation of multiform fascicular tachycardia.

INTRODUCTION: Fascicular tachycardia (FT) is an uncommon cause of monomorphic sustained ventricular tachycardia (VT). We describe 6 cases of FT with multiform QRS morphologies. METHODS AND RESULTS: Six of 823 consecutive VT cases were retrospectively analyzed and found attributable to FT with multiform QRS patterns, with 3 cases exhibiting narrow QRS VT as well. All underwent electrophysiology study including fascicular potential mapping, entrainment pacing, and electroanatomic mapping. The first 3 cases describe similar multiform VT patterns with successful ablation in the upper mid septum. Initially, a right bundle branch block (RBBB) VT with superior axis was induced. Radiofrequency catheter ablation (RFCA) targeting the left posterior fascicle (LPF) resulted in a second VT with RBBB inferior axis. RFCA in the upper septum just apical to the LBB potential abolished VT in all cases. Cases 4 and 5 showed RBBB VT with alternating fascicular block compatible with upper septal dependent VT, resulting in bundle branch reentrant VT (BBRT) after ablation of LPF and left anterior fascicle (LAF). Finally, Cases 5 and 6 demonstrated spontaneous shift in QRS morphology during VT, implicating participation of a third fascicle. In Case 6, successful ablation was achieved over the proximal LAF, likely representing insertion of the auxiliary fascicle near the proximal LAF. CONCLUSIONS: Multiform FTs show a reentrant mechanism using multiple fascicular branches. We hypothesize that retrograde conduction over the septal fascicle produces alternate fascicular patterns as well as narrow VT forms. Ablation of the respective fascicle was successful in abolishing FT but does not preclude development of BBRT unless septal fascicle is targeted and ablated.

Fascicular and nonfascicular left ventricular tachycardias in the young: an international multicenter study.

INTRODUCTION: The aim of this study was to evaluate the clinical presentation and outcomes of pediatric patients with ventricular tachycardia (VT) originating from left heart structures. METHODS AND RESULTS: This international multicenter retrospective study including 152 patients (age 10.0 ± 5.1 years, 62% male), divided into those with fascicular VT (85%, 129/152) and nonfascicular LV VT (15%, 23/152). All patients had a normal heart structure or only a minor cardiac abnormality. Adenosine was largely ineffective in both groups (tachycardia termination in 4/74 of fascicular VT and 0/5 of nonfascicular LV VT). In fascicular VT, calcium channel blockers were effective in 80% (74/92); however, when administered orally, there was a 21% (13/62) recurrence rate. In nonfascicular LV VT, a variety of antiarrhythmic therapies were used with no one predominating. Ablation procedures were successful in 71% (72/102) of fascicular VT and 67% (12/18) of nonfascicular LV VT on an intention to treat analysis. Major complications occurred in 5 patients with fascicular VT and 1 patient with nonfascicular LV VT. After a follow-up period of 2 years (1 day to 15 years), 72% of all patients with fascicular VT were off medications with no tachycardia recurrence. One patient died of noncardiac causes. In nonfascicular LV VT, follow-up was 3.5 years (0.5-15 years), P = 0.38. A total of 65% of these patients were free from arrhythmias. Two patients died suddenly (P < 0.01). CONCLUSION: The clinical course and outcomes of pediatric patients with fascicular VT and nonfascicular LV VT are varied. Catheter ablation procedures can be curative.

The Value of Programmed Ventricular Extrastimuli From the Right Ventricular Basal Septum During Supraventricular Tachycardia.

BACKGROUND: The difference between the right ventricular (RV) apical stimulus-atrial electrogram (SA) interval during resetting of supraventricular tachycardia (SVT) versus the ventriculoatrial (VA) interval during SVT (ΔSA-VAapex) is an established technique for discerning SVT mechanisms but is limited by a significant diagnostic overlap. OBJECTIVES: This study hypothesized that the difference between the RV SA interval during resetting of SVTs versus the VA interval during SVTs (ΔSA-VA) would yield a more robust differentiation of atrioventricular nodal re-entrant tachycardia (AVNRT) from atrioventricular reciprocating tachycardia (AVRT) when using the RV basal septal stimulation (ΔSA-VAbase) as compared to the RV apical stimulation (ΔSA-VAapex). Moreover, it was predicted that the ΔSA-VAbase might distinguish septal from free wall accessory pathways (APs) effectively. METHODS: In this prospective study, 105 patients with AVNRTs (age 48 ± 20 years, 44% male) and 130 with AVRTs (age 26 ± 18 years, 54% male) underwent programmed ventricular extrastimuli delivered from both the RV basal septum and RV apex. The ΔSA-VA values were compared between the 2 sites. RESULTS: The ΔSA-VAbase was shorter than the ΔSA-VAapex during AVRT (44 ± 30 ms vs 58 ± 29 ms; P < 0.001), and the opposite occurred during AVNRT (133 ± 31 ms vs 125 ± 25 ms; P = 0.03). A ΔSA-VAbase of ≧85 milliseconds had a sensitivity of 97% and specificity of 96% for identifying AVNRT. Furthermore, a ΔSA-VAbase of 45-85 milliseconds identified AVRT with left free wall APs (sensitivity 86%, specificity 95%), 20-45 milliseconds for posterior septal APs (sensitivity 72%, specificity 96%), and <20 milliseconds for right free wall or anterior/mid septal APs (sensitivity 86%, specificity 98%). CONCLUSIONS: The ΔSA-VAbase during programmed ventricular extrastimuli produced a robust differentiation between AVNRT and AVRT regardless of the AP location with ≧85 milliseconds as an excellent cutoff point. This straightforward technique further allowed localizing 4 general AP sites.

Clinical and electrophysiologic characteristics of antidromic tachycardia in children with Wolff-Parkinson-White syndrome.

BACKGROUND: Antidromic reciprocating tachycardia (ART) is a rare form of wide complex tachycardia in children with Wolff-Parkinson-White syndrome (WPW). The incidence and electrophysiologic characteristics of ART in children with WPW have not been well described. METHODS: A multicenter retrospective analysis of all patients with WPW undergoing electrophysiology (EP) study from 1990 to 2009 was performed. Patients with clinical or inducible ART were included. RESULTS: A total of 1,147 patients with WPW underwent EP study and 30 patients had ART (2.6%) and were the subject of this analysis. The mean age was 16±3 years, weight was 65±16 kg, and tachycardia cycle length was 305±55 ms. There were two patients (7%) with congenital heart disease (both with Ebstein's anomaly). Four patients (13%) had more than one accessory pathway (AP). The location of the AP was left sided in 53% of patients and right sided in 47%, with septal location and left lateral pathways most commonly involved. AP conduction was found to be high risk in 17 patients (57%). Ablation was not attempted in two patients (7%) due to proximity to the HIS and risk of heart block. Ablation was acutely successful in 93% of the patients in whom it was attempted. CONCLUSIONS: ART is a rare finding in children undergoing EP study. Over half of the patients with ART were found to be high risk and multiple AP were uncommon. Unlike the adult population, ART occurred commonly with septal APs.

Cardiac Resynchronization Therapy for Adult Patients With a Failing Systemic Right Ventricle: A Multicenter Study.

Background The objective of this international multicenter study was to investigate both early and late outcomes of cardiac resynchronization therapy (CRT) in patients with a systemic right ventricle (SRV) and to identify predictors for congestive heart failure readmissions and mortality. Methods and Results This retrospective international multicenter study included 13 centers. The study population comprised 80 adult patients with SRV (48.9% women) with a mean age of 45±14 (range, 18-77) years at initiation of CRT. Median follow-up time was 4.1 (25th-75th percentile, 1.3-8.3) years. Underlying congenital heart disease consisted of congenitally corrected transposition of the great arteries and dextro-transposition of the great arteries in 63 (78.8%) and 17 (21.3%) patients, respectively. CRT resulted in significant improvement in functional class (before CRT: III, 25th-75th percentile, II-III; after CRT: II, 25th-75th percentile, II-III; P=0.005) and QRS duration (before CRT: 176±27; after CRT: 150±24 milliseconds; P=0.003) in patients with pre-CRT ventricular pacing who underwent an upgrade to a CRT device (n=49). These improvements persisted during long-term follow-up with a marginal but significant increase in SRV function (before CRT; 30%, 25th-75th percentile, 25-35; after CRT: 31%, 25th-75th percentile, 21-38; P=0.049). In contrast, no beneficial change in the above-mentioned variables was observed in patients who underwent de novo CRT (n=31). A quarter of all patients were readmitted for heart failure during follow-up, and mortality at latest follow-up was 21.3%. Conclusions This international experience with CRT in patients with an SRV demonstrated that CRT in selected patients with SRV dysfunction and pacing-induced dyssynchrony yielded consistent improvement in QRS duration and New York Heart Association functional status, with a marginal increase in SRV function.