Starvation induces shrinkage of the bacterial cytoplasm.

Environmental fluctuations are a common challenge for single-celled organisms; enteric bacteria such as Escherichia coli experience dramatic changes in nutrient availability, pH, and temperature during their journey into and out of the host. While the effects of altered nutrient availability on gene expression and protein synthesis are well known, their impacts on cytoplasmic dynamics and cell morphology have been largely overlooked. Here, we discover that depletion of utilizable nutrients results in shrinkage of E. coli's inner membrane from the cell wall. Shrinkage was accompanied by an ∼17% reduction in cytoplasmic volume and a concurrent increase in periplasmic volume. Inner membrane retraction after sudden starvation occurred almost exclusively at the new cell pole. This phenomenon was distinct from turgor-mediated plasmolysis and independent of new transcription, translation, or canonical starvation-sensing pathways. Cytoplasmic dry-mass density increased during shrinkage, suggesting that it is driven primarily by loss of water. Shrinkage was reversible: upon a shift to nutrient-rich medium, expansion started almost immediately at a rate dependent on carbon source quality. A robust entry into and recovery from shrinkage required the Tol-Pal system, highlighting the importance of envelope coupling during shrinkage and recovery. Klebsiella pneumoniae also exhibited shrinkage when shifted to carbon-free conditions, suggesting a conserved phenomenon. These findings demonstrate that even when Gram-negative bacterial growth is arrested, cell morphology and physiology are still dynamic.

Management of Junctional Rhythm in Patients After the Fontan Operation: A Multicenter Congenital Cardiology Survey.

Sinus node dysfunction with concomitant junctional rhythm (JR) is frequently observed among Fontan patients and has been recognized as a contributor to heart failure. The impact and management of JR is unclear. A survey was mailed to all members of the Pediatric and Congenital Electrophysiology society (PACES) and members were asked to forward the questionnaire to their non-electrophysiology colleagues. Responses were received from 154 physicians (88 electrophysiologists (EP's) and 66 non-EP's (46 pediatric cardiologists and 20 adult congenital cardiologists). There were few differences in the response between EP's and non-EP's. Overall, 57% recommended an annual ambulatory ECG (AECG). A significant majority (80%) opted to continue to follow patients with significant periods of JR on AECG as long as the patients were asymptomatic, and showed no echocardiographic signs of cardiac decompensation. However, 84% would place a pacemaker in a patient with JR who was having open chest surgery for other reasons. Finally, pacemaker placement would be performed by 91% if a patient with JR showed signs of heart failure. Most congenital cardiologists would not recommend pacemaker placement in asymptomatic Fontan patients with JR. Further studies are needed on the Fontan population to determine the impact of SND and JR on longer term outcomes and to determine the role and optimal timing of pacemaker placement in these patients.

Patterns of Electrocardiographic Abnormalities in Children with Hypertrophic Cardiomyopathy.

Hypertrophic cardiomyopathy (HCM), a common cardiomyopathy in children, is an important cause of morbidity and mortality. Early recognition and appropriate management are important. An electrocardiogram (ECG) is often used as a screening tool in children to detect heart disease. The ECG patterns in children with HCM are not well described.ECGs collected from an international cohort of children, and adolescents (≤ 21 years) with HCM were reviewed. 482 ECGs met inclusion criteria. Age ranged from 1 day to 21 years, median 13 years. Of the 482 ECGs, 57 (12%) were normal. The most common abnormalities noted were left ventricular hypertrophy (LVH) in 108/482 (22%) and biventricular hypertrophy (BVH) in 116/482 (24%) Of the patients with LVH/BVH (n = 224), 135 (60%) also had a strain pattern (LVH in 83, BVH in 52). Isolated strain pattern (in the absence of criteria for hypertrophy) was seen in 43/482 (9%). Isolated pathologic Q waves were seen in 71/482 (15%). Pediatric HCM, 88% have an abnormal ECG. The most common ECG abnormalities were LVH or BVH with or without strain. Strain pattern without hypertrophy and a pathologic Q wave were present in a significant proportion (24%) of patients. Thus, a significant number of children with HCM have ECG abnormalities that are not typical for "hypertrophy". The presence of the ECG abnormalities described above in a child should prompt further examination with an echocardiogram to rule out HCM.

Sudden cardiac death in congenital heart disease.

Sudden cardiac death (SCD) accounts for up to 25% of deaths in patients with congenital heart disease (CHD). To date, research has largely been driven by observational studies and real-world experience. Drawbacks include varying definitions, incomplete taxonomy that considers SCD as a unitary diagnosis as opposed to a terminal event with diverse causes, inconsistent outcome ascertainment, and limited data granularity. Notwithstanding these constraints, identified higher-risk substrates include tetralogy of Fallot, transposition of the great arteries, cyanotic heart disease, Ebstein anomaly, and Fontan circulation. Without autopsies, it is often impossible to distinguish SCD from non-cardiac sudden deaths. Asystole and pulseless electrical activity account for a high proportion of SCDs, particularly in patients with heart failure. High-quality cardiopulmonary resuscitation is essential to improve outcomes. Pulmonary hypertension and CHD complexity are associated with lower likelihood of successful resuscitation. Risk stratification for primary prevention implantable cardioverter-defibrillators (ICDs) should consider the probability of SCD due to a shockable rhythm, competing causes of mortality, complications of ICD therapy, and associated costs. Risk scores to better estimate probabilities of SCD and CHD-specific guidelines and consensus-based recommendations have been proposed. The subcutaneous ICD has emerged as an attractive alternative to transvenous systems in those with vascular access limitations, prior device infections, intra-cardiac shunts, or a Fontan circulation. Further improving SCD-related outcomes will require a multidimensional approach to research that addresses disease processes and triggers, taxonomy to better reflect underlying pathophysiology, high-risk features, early warning signs, access to high-quality cardiopulmonary resuscitation and specialized care, and preventive therapies tailored to underlying mechanisms.

Transseptal puncture during catheter ablation associated with higher radiation exposure.

BACKGROUND: Electroanatomic mapping systems are increasingly used during ablations to decrease the need for fluoroscopy and therefore radiation exposure. For left-sided arrhythmias, transseptal puncture is a common procedure performed to gain access to the left side of the heart. We aimed to demonstrate the radiation exposure associated with transseptal puncture. METHODS: Data were retrospectively collected from the Catheter Ablation with Reduction or Elimination of Fluoroscopy registry. Patients with left-sided accessory pathway-mediated tachycardia, with a structurally normal heart, who had a transseptal puncture, and were under 22 years of age were included. Those with previous ablations, concurrent diagnostic or interventional catheterisation, and missing data for fluoroscopy use or procedural outcomes were excluded. Patients with a patent foramen ovale who did not have a transseptal puncture were selected as the control group using the same criteria. Procedural outcomes were compared between the two groups. RESULTS: There were 284 patients in the transseptal puncture group and 70 in the patent foramen ovale group. The transseptal puncture group had a significantly higher mean procedure time (158.8 versus 131.4 minutes, p = 0.002), rate of fluoroscopy use (38% versus 7%, p < 0.001), and mean fluoroscopy time (2.4 versus 0.6 minutes, p < 0.001). The acute success and complication rates were similar. CONCLUSIONS: Performing transseptal puncture remains a common reason to utilise fluoroscopy in the era of non-fluoroscopic ablation. Better tools are needed to make non-fluoroscopic transseptal puncture more feasible.

Epicardial atrial pacing after the extracardiac Fontan operation: Feasibility of an entirely transvenous approach.

This series describes an innovative technique for pacing in patients with sinus node dysfunction after extracardiac Fontan surgery. This transpulmonary approach to the left atrial epi-myocardium has been successfully applied to three patients at two centers and resulted in excellent acute and midterm pacing characteristics without known complications. The principal advantage of this procedure in comparison to prior iterations is the absence of pacing material within the pulmonary venous atrium, so that future systemic thromboembolism risk is minimized. The transpulmonary approach for permanent atrial pacing offers a novel solution to the unique challenges for patients after extracardiac Fontan operation.

Utilising electroanatomic mapping during ablation in patients with CHD to reduce radiation exposure.

BACKGROUND: Patients with CHD can be exposed to high levels of cumulative ionising radiation. Utilisation of electroanatomic mapping during catheter ablation leads to reduced radiation exposure in the general population but has not been well studied in patients with CHD. This study evaluated the radiation sparing benefit of using three-dimensional mapping in patients with CHD. METHODS: Data were retrospectively collected from the Catheter Ablation with Reduction or Elimination of Fluoroscopy multi-institutional registry. Patients with CHD were selected. Those with previous ablations, concurrent diagnostic or interventional catheterisation and unknown arrhythmogenic foci were excluded. The control cohort was matched for operating physician, arrhythmia mechanism, arrhythmia location, weight and age. The procedure time, rate of fluoroscopy use, fluoroscopy time, procedural success, complications, and distribution of procedures per year were compared between the two groups. RESULTS: Fifty-six patients with congenital heart disease and 56 matched patients without CHD were included. The mean total procedure time was significantly higher in patients with CHD (212.6 versus 169.5 minutes, p = 0.003). Their median total fluoroscopy time was 4.4 minutes (compared to 1.8 minutes), and their rate of fluoroscopy use was 23% (compared to 13%). The acute success and minor complication rates were similar and no major complications occurred. CONCLUSIONS: With the use of electroanatomic mapping during catheter ablation, fluoroscopy use can be reduced in patients with CHD. The majority of patients with CHD received zero fluoroscopy.

Extreme Acid Modulates Fitness Trade-Offs of Multidrug Efflux Pumps MdtEF-TolC and AcrAB-TolC in Escherichia coli K-12.

Bacterial genomes encode various multidrug efflux pumps (MDR) whose specific conditions for fitness advantage are unknown. We show that the efflux pump MdtEF-TolC, in Escherichia coli, confers a fitness advantage during exposure to extreme acid (pH 2). Our flow cytometry method revealed pH-dependent fitness trade-offs between bile acids (a major pump substrate) and salicylic acid, a membrane-permeant aromatic acid that induces a drug resistance regulon but depletes proton motive force (PMF). The PMF drives MdtEF-TolC and related pumps such as AcrAB-TolC. Deletion of mdtE (with loss of the pump MdtEF-TolC) increased the strain's relative fitness during growth with or without salicylate or bile acids. However, when the growth cycle included a 2-h incubation at pH 2 (below the pH growth range), MdtEF-TolC conferred a fitness advantage. The fitness advantage required bile salts but was decreased by the presence of salicylate, whose uptake is amplified by acid. For comparison, AcrAB-TolC, the primary efflux pump for bile acids, conferred a PMF-dependent fitness advantage with or without acid exposure in the growth cycle. A different MDR pump, EmrAB-TolC, conferred no selective benefit during growth in the presence of bile acids. Without bile acids, all three MDR pumps incurred a large fitness cost with salicylate when exposed at pH 2. These results are consistent with the increased uptake of salicylate at low pH. Overall, we showed that MdtEF-TolC is an MDR pump adapted for transient extreme-acid exposure and that low pH amplifies the salicylate-dependent fitness cost for drug pumps. IMPORTANCE Antibiotics and other drugs that reach the gut must pass through stomach acid. However, little is known of how extreme acid modulates the effect of drugs on gut bacteria. We find that extreme-acid exposure leads to a fitness advantage for a multidrug pump that otherwise incurs a fitness cost. At the same time, extreme acid amplifies the effect of salicylate selection against multidrug pumps. Thus, organic acids and stomach acid could play important roles in regulating multidrug resistance in the gut microbiome. Our flow cytometry assay provides a way to measure the fitness effects of extreme-acid exposure to various membrane-soluble organic acids, including plant-derived nutrients and pharmaceutical agents. Therapeutic acids might be devised to control the prevalence of multidrug pumps in environmental and host-associated habitats.

Pulmonary vein and left atrial posterior wall isolation for the treatment of atrial fibrillation: Comparable outcomes for adults with congenital heart disease.

INTRODUCTION: Optimal treatment strategies for ACHD with AF are unknown. This study sought to assess outcomes of pulmonary vein isolation (PVI) ± left atrial (LA), posterior wall isolation (PWI) for adults with congenital heart disease (ACHD), and atrial fibrillation (AF). METHODS: A retrospective review of all cryoballoon (CB) PVI ± PWI procedures at a single center over a 3-year period were performed. Clinical characteristics and outcomes for patients with and without ACHD were compared. The primary outcome was the occurrence of atrial tachyarrhythmia at 12-months postablation after a 90-day blanking period. RESULTS: Three-hundred and sixteen patients (mean: 63 ± 12 years, [63% male]) underwent CB PVI ± PWI during the study, including 31 (10%) ACHD (simple 35%, moderate 39% complex 26%; nonparoxysmal AF in 52%). ACHD was younger (51 vs. 64 years; p < .001) with a lower CHADS2 DS2 -VASc score (1.2 vs. 2.1; p = .001) but had a greater LA diameter (4.9 vs. 4.0 cm; p < .001) and a number of prior cardioversions (0.9 vs. 0.4; p < .001) versus controls. 12-month freedom from recurrent AF was similar for ACHD and controls (76% vs. 80%; p = .6) and remained nonsignificant in multivariate analysis (hazard ratio: 1.8, 95% confidence interval: 0.7-5.1; p = .22). At 12-months postablation, 75% of ACHD versus 93% of control patients were off antiarrhythmic drug therapy (p = .07). CONCLUSION: This study demonstrates younger age and lower conventional stroke risk, yet clinically advanced AF for ACHD relative to controls. CB PVI ± PWI was an effective strategy for the treatment of AF among all forms of ACHD with similar 12-month outcomes as compared to controls.

Acute outcomes of three-dimensional mapping for fluoroscopy reduction in paediatric catheter ablation for supraventricular tachycardia.

BACKGROUND: Catheter ablation is a safe and effective therapy for the treatment of supraventricular tachycardia in children. Current improvements in technology have allowed progressive reduction in radiation exposure associated with the procedure. To assess the impact of three-dimensional mapping, we compared acute procedural results collected from the Catheter Ablation with Reduction or Elimination of Fluoroscopy registry to published results from the Prospective Assessment after Pediatric Cardiac Ablation study. METHODS: Inclusion and exclusion criteria from the Prospective Assessment after Pediatric Cardiac Ablation study were used as guidelines to select patient data from the Catheter Ablation with Reduction or Elimination of Fluoroscopy registry to compare acute procedural outcomes between cohorts. Outcomes assessed include procedural and fluoroscopy exposure times, success rates of procedure, and complications. RESULTS: In 786 ablation procedures, targeting 498 accessory pathways and 288 atrioventricular nodal reentrant tachycardia substrates, average procedural time (156.5 versus 206.7 minutes, p < 0.01), and fluoroscopy time (1.2 versus 38.3 minutes, p < 0.01) were significantly shorter in the study group. Success rates for the various substrates were similar except for manifest accessory pathways which had a significantly higher success rate in the study group (96.4% versus 93.0%, p < 0.01). Major complication rates were significantly lower in the study group (0.3% versus 1.6%, p < 0.01). CONCLUSIONS: In a large, multicentre study, three-dimensional systems show favourable improvements in clinical outcomes in children undergoing catheter ablation of supraventricular tachycardia compared to the traditional fluoroscopic approach. Further improvements are anticipated as technology advances.

Non-Genetic Diversity in Chemosensing and Chemotactic Behavior.

Non-genetic phenotypic diversity plays a significant role in the chemotactic behavior of bacteria, influencing how populations sense and respond to chemical stimuli. First, we review the molecular mechanisms that generate phenotypic diversity in bacterial chemotaxis. Next, we discuss the functional consequences of phenotypic diversity for the chemosensing and chemotactic performance of single cells and populations. Finally, we discuss mechanisms that modulate the amount of phenotypic diversity in chemosensory parameters in response to changes in the environment.

Experimental Evolution of Escherichia coli K-12 in the Presence of Proton Motive Force (PMF) Uncoupler Carbonyl Cyanide m-Chlorophenylhydrazone Selects for Mutations Affecting PMF-Driven Drug Efflux Pumps.

Experimental evolution of Escherichia coli K-12 with benzoate, a partial uncoupler of the proton motive force (PMF), selects for mutations that decrease antibiotic resistance. We conducted experimental evolution in the presence of carbonyl cyanide m-chlorophenylhydrazone (CCCP), a strong uncoupler. Cultures were serially diluted daily 1:100 in LBK medium containing 20 to 150 µM CCCP buffered at pH 6.5 or at pH 8.0. After 1,000 generations, the populations tolerated up to 150 µM CCCP. Sequenced isolates had mutations in mprA (emrR), which downregulates the EmrAB-TolC pump that exports CCCP. A mprA::kanR deletion conferred growth at 60 µM CCCP, though not at the higher levels resisted by evolved strains (150 µM). Some mprA mutant strains also had point mutations affecting emrA, but deletion of emrA abolished the CCCP resistance. Thus, CCCP-evolved isolates contained additional adaptations. One isolate lacked emrA or mprA mutations but had mutations in cecR (ybiH), whose product upregulates drug pumps YbhG and YbhFSR, and in gadE, which upregulates the multidrug pump MdtEF. A cecR::kanR deletion conferred partial resistance to CCCP. Other multidrug efflux genes that had mutations included ybhR and acrAB The acrB isolate was sensitive to the AcrAB substrates chloramphenicol and tetracycline. Other mutant genes in CCCP-evolved strains include rng (RNase G) and cyaA (adenylate cyclase). Overall, experimental evolution revealed a CCCP-dependent fitness advantage for mutations increasing CCCP efflux via EmrA and for mutations that may deactivate proton-driven pumps for drugs not present (cecR, gadE, acrAB, and ybhR). These results are consistent with our previous report of drug sensitivity associated with evolved benzoate tolerance.IMPORTANCE The genetic responses of bacteria to depletion of proton motive force (PMF), and their effects on drug resistance, are poorly understood. PMF drives export of many antibiotics, but the energy cost may decrease fitness when antibiotics are absent. Our evolution experiment reveals genetic mechanisms of adaptation to the PMF uncoupler CCCP, including selection for increased CCCP efflux but also against the expression of PMF-driven pumps for drugs not present. The results have implications for our understanding of the gut microbiome, which experiences high levels of organic acids that decrease PMF.

Inverted Regulation of Multidrug Efflux Pumps, Acid Resistance, and Porins in Benzoate-Evolved Escherichia coli K-12.

Benzoic acid, a partial uncoupler of the proton motive force (PMF), selects for sensitivity to chloramphenicol and tetracycline during the experimental evolution of Escherichia coli K-12. Transcriptomes of E. coli isolates evolved with benzoate showed the reversal of benzoate-dependent regulation, including the downregulation of multidrug efflux pump genes, the gene for the Gad acid resistance regulon, the nitrate reductase genes narHJ, and the gene for the acid-consuming hydrogenase Hyd-3. However, the benzoate-evolved strains had increased expression of OmpF and other large-hole porins that admit fermentable substrates and antibiotics. Candidate genes identified from benzoate-evolved strains were tested for their roles in benzoate tolerance and in chloramphenicol sensitivity. Benzoate or salicylate tolerance was increased by deletion of the Gad activator ariR or of the acid fitness island from slp to the end of the gadX gene encoding Gad regulators and the multidrug pump genes mdtEF Benzoate tolerance was also increased by deletion of multidrug component gene emrA, RpoS posttranscriptional regulator gene cspC, adenosine deaminase gene add, hydrogenase gene hyc (Hyd-3), and the RNA chaperone/DNA-binding regulator gene hfq Chloramphenicol resistance was decreased by mutations in genes for global regulators, such as RNA polymerase alpha subunit gene rpoA, the Mar activator gene rob, and hfq Deletion of lipopolysaccharide biosynthetic kinase gene rfaY decreased the rate of growth in chloramphenicol. Isolates from experimental evolution with benzoate had many mutations affecting aromatic biosynthesis and catabolism, such as aroF (encoding tyrosine biosynthesis) and apt (encoding adenine phosphoribosyltransferase). Overall, benzoate or salicylate exposure selects for the loss of multidrug efflux pumps and of hydrogenases that generate a futile cycle of PMF and upregulates porins that admit fermentable nutrients and antibiotics.IMPORTANCE Benzoic acid is a common food preservative, and salicylic acid (2-hydroxybenzoic acid) is the active form of aspirin. At high concentrations, benzoic acid conducts a proton across the membrane, depleting the proton motive force. In the absence of antibiotics, benzoate exposure selects against proton-driven multidrug efflux pumps and upregulates porins that admit fermentable substrates but that also allow the entry of antibiotics. Thus, evolution with benzoate and related molecules, such as salicylates, requires a trade-off for antibiotic sensitivity, a trade-off that could help define a stable gut microbiome. Benzoate and salicylate are naturally occurring plant signal molecules that may modulate the microbiomes of plants and animal digestive tracts so as to favor fermenters and exclude drug-resistant pathogens.

Ultrahigh-density mapping supplemented with global chamber activation identifies noncavotricuspid-dependent intra-atrial re-entry conduction isthmuses in adult congenital heart disease.

OBJECTIVE: To evaluate the role of ultrahigh-density mapping for conduction isthmus (CI) characterization in adult congenital heart disease (ACHD). BACKGROUND: Catheter ablation remains suboptimal for ACHD with atypical intra-atrial reentrant tachycardias (IART) that can be challenging to define using existing mapping technology. METHODS: An ultrahigh-density mapping system was selectively employed over a 1-year period for procedures involving noncavotricuspid isthmus-dependent-IART. A global activation histogram (GAH) was assessed for the ability to predict ablation targets. Procedural characteristics were compared to a group of matched controls. RESULTS: Twenty patients (mean age 43 ± 15, 70% male) underwent 20 procedures targeting 34 tachycardias during the study period. Diagnoses included single ventricle (8), tetralogy of Fallot (2), left heart obstruction (3), Ebstein's anomaly (2) atrial septal defect (2), Mustard operation (2), and Rasteilli operation (1). Prior catheter ablation/Maze operation had been performed in 12 (60%). The median time per map was 21 minutes (interquartile range [IQR], 16-32), representing 14 834 points per map (IQR 9499-43 191; P < .001 vs controls). Review of GAH maps showed lower trough values were associated with more favorable IART CI characteristics (P ≤ =.001 for all). Acute success was achieved in 19/20 (95%) procedures, with tachycardia termination during the first lesion in eight cases (P = .02 vs controls). There was one recurrence during 0.6 years follow-up. CONCLUSIONS: Ultrahigh-density mapping supplemented with the GAH tool was effective for CI identification in a cohort of complex ACHD patients. Catheter ablation was more efficient compared to controls, suggesting precise CI characterization using this technology.

Initial experience with transcatheter pacemaker implantation for adults with congenital heart disease.

BACKGROUND: Transvenous pacemaker systems have significant advantages over epicardial systems in patients with congenital heart disease (CHD). Frequently though, unique anatomic challenges preclude the use of transvenous leads. Although originally developed for patient with normal anatomy, leadless pacemaker systems have enormous potential in the CHD population. OBJECTIVE: To describe an initial experience with leadless pacemaker implantation in adult patients with CHD who were not the candidates for traditional transvenous pacing. METHODS: This was a retrospective review of the experience with Micra Transcatheter Pacing System implantation in adult patients with CHD. Patient demographics, clinical history, pacing indications, procedural details, clinical outcomes, and pacing characteristics at follow-up are reported. RESULTS: Three patients with intracardiac shunts or tricuspid valve disorders who underwent leadless pacemaker placement are described. Pacing indications included sinus node dysfunction in two and permanent atrial fibrillation with atrioventricular (AV) block in one. There were no procedural or thromboembolic complications over the follow-up period. Pacing characteristics were acceptable and ventricular pacing burden remained low except for the single patient with AV block. CONCLUSIONS: Leadless pacemaker systems are a viable pacing option for appropriately selected adult patients with CHD when transvenous pacing is not a suitable option.

A minimally invasive hybrid approach for cardiac resynchronization of the systemic right ventricle.

BACKGROUND: Patients with systemic right ventricle (RV) often develop progressive heart failure and may benefit from cardiac resynchronization therapy (CRT); however, the optimal strategy for CRT has not been defined. METHODS: A retrospective review of all the patients with systemic RV failure undergoing a hybrid transcatheter-surgical approach was performed. Procedural technique and outcomes are reported. RESULTS: Six patients underwent detailed electroanatomical mapping of the systemic RV followed by a new hybrid approach targeting latest endocardial activation, which was followed by focused epicardial mapping. The exact site of latest endocardial activation was variable but localized to the basolateral RV in all cases. Sites of latest activation tended to be more superior during contralateral ventricular pacing versus intact atrioventricular conduction (P = 0.06). Latest endocardial activation at the targeted site occurred at 157 ms (interquartile range [IQR] = 120-181 ms) and corresponding epicardial activation at 174 ms (IQR = 140-198 ms), after the onset of the QRS complex. Following the hybrid CRT, the QRS duration decreased from a median of 193 to 147 ms and the fractional area of change increased from a median of 15.5% to 30% (P < 0.001). Patients were discharged to home after a median of 4 days. Of the three patients who were initially referred for transplant evaluation, two (66%) of them no longer met the criteria following CRT. CONCLUSIONS: Whereas latest endocardial activation for the systemic RV appears to localize to the basolateral region, the optimal lead position may be variable. An approach utilizing endocardial mapping followed by a limited surgical incision and confirmation of latest activation may result in minimally invasive surgery and a favorable acute CRT response.

Cosmetic outcomes and quality of life in children with cardiac implantable electronic devices.

BACKGROUND: Axillary implant location is an alternative implant location in patients for cardiac implantable electronic devices (CIEDs) for the purposes of improved cosmetic outcome. The impact from the patient's perspective is unknown. The purpose of this study was to compare scar perception scores and quality of life (QOL) in pediatric patients with axillary CIED implant location versus the standard infraclavicular approach. METHODS: This is a multicenter prospective study conducted at eight pediatric centers and it includes patients aged from 8 to 18 years with a CIED. Patients with prior sternotomy were excluded. Scar perception and QOL outcomes were compared between the infraclavicular and axillary implant locations. RESULTS: A total of 141 patients (83 implantable cardioverter defibrillator [ICD]/58 pacemakers) were included, 55 with an axillary device and 86 with an infraclavicular device. Patients with an ICD in the axillary position had better perception of scar appearance and consciousness. Patients in the axillary group reported, on average, a total Pediatric QOL Inventory score that was 6 (1, 11) units higher than the infraclavicular group, after adjusting for sex and race (P = 0.02). CONCLUSIONS: QOL is significantly improved in axillary in comparison to the infraclavicular CIED position, regardless of device type. Scar perception is improved in patients with ICD in the axillary position.

The effects of pulmonary valve replacement on QRS duration in repaired tetralogy of Fallot patients with pulmonary regurgitation.

INTRODUCTION: Chronic pulmonary regurgitation (PR) following surgical correction in Tetralogy of Fallot (TOF) leads to right ventricular (RV) dysfunction, arrhythmias and sudden cardiac death (SCD). Pulmonary valve replacement (PVR) decreases PR and improves RV function, but data regarding QRS duration reduction remain scarce. METHODS: All adult TOF patients undergoing transcatheter PVR or surgical PVR from 2010 to 2016 were included. Clinical characteristics and QRS duration were measured and compared to post-intervention QRS duration using an institutional software and manually verified. Significantly wide QRS was defined as QRS >140 ms. RESULTS: Of 133 PVR patients, 85 had TOF and 27 (21.1%) had QRS > 140 ms (14 transcatheter, 13 surgical) and were included in this analysis. A 6 ms decrease in QRS duration was seen at 3-year follow-up (168.0 ±â€¯3.5 ms vs. 161.8 ±â€¯3.5 ms, p = .04). There was a significant decrease in the median RV size (defined as RV/LV diameter ratio) pre-intervention to 3-year post-intervention: (0.96 vs 0.89, p = .03). The median PR decreased significantly from moderate-severe to mild post-intervention (p < .0001). CONCLUSIONS: Replacement of the pulmonary valve in high risk TOF patients reduces QRS duration at 3 years. Further study is needed to assess whether this QRS duration reduction may identify patients at lower risk of ventricular arrhythmias.

Impact of Obesity on Left Ventricular Thickness in Children with Hypertrophic Cardiomyopathy.

Obesity is associated with additional left ventricular hypertrophy (LVH) in adults with hypertrophic cardiomyopathy (HCM). It is not known whether obesity can lead to further LVH in children with HCM. Echocardiographic LV dimensions were determined in 504 children with HCM. Measurements of interventricular septal thickness (IVST) and posterior wall thickness (PWT), and patients' weight and height were recorded. Obesity was defined as a body mass index (BMI) ≥ 99th percentile for age and sex. IVST data was available for 498 and PWT data for 484 patients. Patient age ranged from 2 to 20 years (mean ± SD, 12.5 ± 3.9) and 340 (68%) were males. Overall, patient BMI ranged from 7 to 50 (22.7 ± 6.1). Obesity (BMI 18-50, mean 29.1) was present in 140 children aged 2-19.6 (11.3 ± 4.1). The overall mean IVST was 20.5 ± 9.6 mm and the overall mean PWT was 11.0 ± 8.4 mm. The mean IVST in the obese patients was 21.6 ± 10.0 mm and mean PWT was 13.3 ± 14.7 mm. The mean IVST in the non-obese patients was 20.1 ± 9.5 mm and mean PWT was 10.4 ± 4.3 mm. Obesity was not significantly associated with IVST (p = 0.12), but was associated with increased PWT (0.0011). Obesity is associated with increased PWT but not IVST in children with HCM. Whether obesity and its impact on LVH influences clinical outcomes in children with HCM needs to be studied.