Rajiv Chaturvedi

Complications of pediatric cardiac catheterization: A review in the current era

Objective: To determine types of complications and risks associated with pedatric cardiac catheterization in the current era. Background: Pedatric cardiac catheterization is an important diagnostic and therapeutic tool. Although in the last decade, there have been significant improvements in technology and equipment, the risk for complications remains, adversely effecting outcomes. Design: The clinical records of 11,073 children undergoing cardiac catheterizations between January 1994 and March 2006 were reviewed to identify procedures associated with complications within the first 24 h after catheterization. All childrens electronic and paper chart records were reviewed to obtain demographic, procedural, and treatment data. Results: A total of 858 (7.3%) complications (classified as major or minor) occurred in 816 studies (510 males, 63%), in children ranging in age from 8 h to 20 years (median 4.13 years). There were 195 major (22%) and 663 (78%) minor complications. Vascular complications represented the majority (n = 278; 32.4%) and were major in 53 instances (P < 0.0001). Twenty‐five children died within 24 h (0.23% of total case numbers). Independent risk factors for a complication included young patient age (<6 months), male gender, inpatient status, and year of catheterization. Conclusions: Complications continue to be associated with pedatric cardiac catheterization, although overall incidence appears to be decreasing. Patient age, gender, and inpatient status continue to be risk factors for morbidity and mortality. Efforts at improving equipment for flexibility and size, and developing strategies for the use of alternative methods for catheter access should be encouraged.

Cardiac ECMO for biventricular hearts after paediatric open heart surgery

Objective: To delineate predictors of hospital survival in a large series of children with biventricular physiology supported with extracorporeal membrane oxygenation (ECMO) after open heart surgery. Results: 81 children were placed on ECMO after open heart surgery. 58% (47 of 81) were transferred directly from cardiopulmonary bypass to ECMO. Hospital survival was 49% (40 of 81) but there were seven late deaths among these survivors (18%). Factors that improved the odds of survival were initiation of ECMO in theatre (64% survival (30 of 47)) rather than the cardiac intensive care unit (29% survival (10 of 34)) and initiation of ECMO for reactive pulmonary hypertension. Important adverse factors for hospital survival were serious mechanical ECMO circuit problems, renal support, residual lesions, and duration of ECMO. Conclusions: Hospital survival of children with biventricular physiology who require cardiac ECMO is similar to that found in series that include univentricular hearts, suggesting that successful cardiac ECMO is critically dependent on the identification of hearts with reversible ventricular dysfunction. In our experience of postoperative cardiac ECMO, the higher survival of patients cannulated in the operating room than in the cardiac intensive care unit is due to early effective support preventing prolonged hypoperfusion and the avoidance of a catastrophic cardiac arrest.

Complete heart block associated with device closure of perimembranous ventricular septal defects

OBJECTIVE The development of the Amplatzer Membranous VSD Occluder (AGA Medical Corp, Plymouth, Minn) for closure of the perimembranous ventricular septal defect has ameliorated many of the technical difficulties of previous devices. Application of this new technology requires comparative evaluation with the current standard of surgical repair. We report our experience of complete heart block associated with device closure of a large perimembranous ventricular septal defect with unequivocal indications for intervention. METHODS We performed a retrospective review of 20 patients between January 2003 and August 2005 who underwent perimembranous ventricular septal defect device closure, 18 with hemodynamically large shunts meeting the surgical criteria for intervention. The median age was 1.6 years (range, 0.5-16.2 years), and the median weight was 9.7 kg (range, 6.2-43 kg). RESULTS Acute complete shunt occlusion was achieved in all patients. There were no acute procedural complications. The median follow-up time was 23.1 months (range, 1-37.8 months). Four (22%) had complete heart block at 17 days, 4.2 months, 8.8 months, and 37.5 months after implantation, respectively. No risk factors were identified for development of complete heart block, including age, weight, trisomy 21, preceding conduction abnormalities, perimembranous ventricular septal defect size related to body surface area or device size, and progressive device flattening. CONCLUSIONS Device closure of large perimembranous ventricular septal defects in infants and children with the Amplatzer Membranous VSD Occluder resulted in excellent closure rates but an unacceptably high rate of complete heart block.

Passive Stiffness of Myocardium From Congenital Heart Disease and Implications for Diastole

Background— In ventricular dilatation or hypertrophy, an elevated end-diastolic pressure is often assumed to be secondary to increased myocardial stiffness, but stiffness is rarely measured in vivo because of difficulty. We measured in vitro passive stiffness of volume- or pressure-overloaded myocardium mainly from congenital heart disease. Methods and Results— Endocardial ventricular biopsies were obtained at open heart surgery (n=61; pressure overload, 36; volume-overload, 19; dilated cardiomyopathy, 4; normal donors, 2). In vitro passive force-extension curves and the stiffness modulus were measured in skinned tissue: muscle strips, strips with myofilaments extracted (mainly extracellular matrix), and myocytes. Collagen content (n=38) and titin isoforms (n=16) were determined. End-diastolic pressure was measured at cardiac catheterization (n=14). Pressure-overloaded tissue (strips, extracellular matrix, myocytes) had a 2.6- to 7.0-fold greater force and stiffness modulus than volume-overloaded tissue. Myocyte force and stiffness modulus at short stretches (0.05 resting length, L0) was pressure-overloaded >normal≈volume-overloaded>dilated cardiomyopathy. Titin N2B:N2BA isoform ratio varied little between conditions. The extracellular matrix contributed more to force at 0.05 L0 in pressure-overloaded (35.1%) and volume-overloaded (17.4%) strips than normal myocardium. Stiffness modulus increased with collagen content in pressure-overloaded but not volume-overloaded strips. In vitro stiffness modulus at 0.05 L0 was a good predictor of in vivo end-diastolic pressure for pressure-overloaded but not volume-overloaded ventricles and estimated normal end-diastolic pressure as 5 to 7 mm Hg. Conclusions— An elevated end-diastolic pressure in pressure-overloaded, but not volume-overloaded, ventricles was related to increased myocardial stiffness. The greater stiffness of pressure-overloaded compared with volume-overloaded myocardium was due to the higher stiffness of both the extracellular matrix and myocytes. The transition from normal to very-low stiffness myocytes may mark irreversible dilatation.

Percutaneous Pulmonary Valve Implantation in the Young: 2-Year Follow-Up

OBJECTIVES The aim of this study was to investigate physiological and clinical consequences of percutaneous pulmonary valve implantation (PPVI) in patients with chronic right ventricular outflow tract (RVOT) obstruction and volume overload. BACKGROUND The PPVI is a nonsurgical technique to address RVOT conduit dysfunction. METHODS Twenty-eight adolescents (median age 14.9 years; age range 10.9 to 19 years) underwent PPVI due to RVOT stenosis and/or pulmonary regurgitation (PR). Before and after PPVI echocardiographic and magnetic resonance imaging, cardiopulmonary exercise tests were obtained. RESULTS The RVOT gradient (p < 0.001) and right ventricular (RV) systolic pressure decreased (p < 0.001), acutely. Magnetic resonance imaging (median 6 months) documented reduction in RV end-diastolic (149 +/- 49 ml/m(2) vs. 114 +/- 35 ml/m(2), p < 0.005) volume, increases in left ventricular (LV) end-diastolic (p < 0.007) volume and cardiac output (RV: p < 0.04 and LV: p < 0.02), and reduced PR fraction (24 +/- 10% to 7 +/- 7%, p < 0.0001). Symptoms, aerobic exercise performance (maximal oxygen consumption: p < 0.0001) and ventilatory response to carbon dioxide production (p < 0.003) improved. After 24 months, echocardiography demonstrated the RV/systemic-pressure ratio, and RVOT peak pressure gradient reductions persisted, and PR was absent in 93% (n = 12 of 13) of the cohort. Freedom from surgery was 91%, 83%, and 83%, and freedom from transcatheter reintervention was 91%, 80%, and 80%, at 12, 24, and 36 months, respectively. There were no acute device-related complications, with stent fractures noted in 10.8%. CONCLUSIONS Percutaneous pulmonary valve implantation is feasible and safe in the young with dysfunctional RVOT conduits. An improvement in symptoms, hemodynamic status, and objective findings of exercise performance occurs. Early follow-up demonstrates persistent improvement in ventricular parameters, PR, and objective exercise capacity.

Activation of Myocardial Contraction by the N-Terminal Domains of Myosin Binding Protein-C

Myosin binding protein-C (MyBP-C) is a poorly understood component of the thick filament in striated muscle sarcomeres. Its C terminus binds tightly to myosin, whereas the N terminus contains binding sites for myosin S2 and possibly for the thin filament. To study the role of the N-terminal domains of cardiac MyBP-C (cMyBP-C), we added human N-terminal peptide fragments to human and rodent skinned ventricular myocytes. At concentrations >10 &mgr;mol/L, the N-terminal C0C2 peptide activated force production in the absence of calcium (pCa 9). Force at the optimal concentration (80 &mgr;mol/L) of C0C2 was ≈60% of that in maximal Ca2+ (pCa 4.5), but the rate constant of tension redevelopment (ktr) matched or exceeded (by up to 80%) that produced by Ca2+ alone. Experiments using different N-terminal peptides suggested that this activating effect of C0C2 resulted from binding by the pro/ala-rich C0-C1 linker region, rather than the terminal C0 domain. At a lower concentration (1 &mgr;mol/L), exogenous C0C2 strongly sensitized cardiac myofibrils to Ca2+ at a sarcomere length (SL) of 1.9 &mgr;m but had no significant effect at SL 2.3 &mgr;m. This differential effect caused the normal SL dependence of myofibrillar Ca2+ sensitivity to be reduced by 80% (mouse myocytes) or abolished (human myocytes) in 1 &mgr;mol/L C0C2. These results suggest that cMyBP-C provides a regulatory pathway by which the thick filament can influence the activation of the thin filament, separately from its regulation by Ca2+. Furthermore, the N-terminal region of cMyBP-C can influence the SL-tension (Frank–Starling) relationship in cardiac muscle.

Stenting of the right ventricular outflow tract in the symptomatic infant with tetralogy of Fallot

Background: Repair of neonatal tetralogy of Fallot (TOF) has low mortality. Debate continues regarding the initial management of cyanotic or duct-dependent infants with TOF and adverse risk factors. While repair can and has been performed in these patients, it is associated with increased morbidity. Objective: We review the effectiveness of right ventricular outflow tract (RVOT) stenting in the symptomatic young infant with TOF. Methods: Clinical, echocardiographic, angiographic and haemodynamic data were reviewed for nine patients who underwent 11 RVOT stenting procedures from October 1994 to August 2007. Results: The pulmonary valve was deemed unsalvageable in all patients (median valve diameter 3.7 mm (range 2.7–4.2), Z-score −6.7 (range −9.7 to −5.4). RVOT stenting improved arterial oxygen saturation from a median of 73% (60–85%) to 94% (90–98%) (p = 0.008). Median Z-score for the left pulmonary artery increased from −4.9 (−7.8 to −2.4) before stent implantation to −1.5 (−4.2 to −0.2) (p = 0.02) before surgical repair. Median Z-score for the right pulmonary artery increased from −3.7 (−6.8 to −1.9) to −0.8 (−2.5 to 0.1) (p = 0.008). Median Nakata index increased from 56 mm2/m2 (21–77) to 150 mm2/m2 (123–231) (p = 0.008). There were no procedural complications. Six patients have undergone successful repair. There were no deaths. Conclusions: In the symptomatic young infant with TOF, stenting of the RVOT provides a safe and effective management strategy, improving arterial oxygen saturation and encouraging pulmonary artery growth.

Hybrid Versus Norwood Strategies for Single-Ventricle Palliation

Background— Hybrid and Norwood strategies differ substantially in terms of stage II palliative procedures. We sought to compare these strategies with an emphasis on survival and reintervention after stage II and subsequent Fontan completion. Methods and Results— Of 110 neonates with functionally single-ventricle physiology who underwent stage I palliation between 2004 and 2010, 75 (69%) infants (Norwood, n=43; hybrid, n=32) who subsequently underwent stage II palliation were studied. Survival and reintervention rates after stage II palliation, anatomic and physiologic variables at pre-Fontan assessment, and Fontan outcomes were compared between the groups. Predictors for reintervention were analyzed. Freedom from death/transplant after stage II palliation was equivalent between the groups (Norwood, 80.4% versus hybrid, 85.6% at 3 years, P=0.66). Hybrid patients had a higher pulmonary artery (PA) reintervention rate (P=0.003) and lower Nakata index at pre-Fontan evaluation (P=0.015). Aortic arch and atrioventricular valve reinterventions were not different between the groups. Ventricular end-diastolic pressure, mean PA pressure, and ventricular function were equivalent at pre-Fontan assessment. There were no deaths after Fontan completion in either group (Norwood, n=25, hybrid, n=14). Conclusions— Survival after stage II palliation and subsequent Fontan completion is equivalent between the groups. The hybrid group had a higher PA reintervention rate and smaller PA size. Both strategies achieved adequate physiology for Fontan completion. Evolution of the hybrid strategy requires refinement to provide optimal PA growth.

Percutaneous pulmonary valve implantation within bioprosthetic valves

AIMS Replacement of bioprosthetic valves in the right ventricular (RV) outflow tract (RVOT) is inevitable due to acquired valvar dysfunction. Percutaneous pulmonary valve implantation (PPVI) may result in acceptable clinical improvement avoiding surgical reintervention. To report outcomes of PPVI in dysfunctional surgically implanted bioprosthetic valves. METHODS AND RESULTS All children undergoing PPVI into a bioprosthetic pulmonary valve between October 2005 and February 2008 were reviewed. Acute haemodynamic changes were compared and an analysis of variance applied to assess changes in ventricular geometry and pressure over time. Fourteen children (seven males), median weight 57.8 kg and 14.7 years of age were identified, with an echocardiographic RVOT gradient of 59.6 +/- 26.8 mmHg and a pulmonary regurgitation (PR) grade of 3.6 +/- 0.8 (out of 4). Implantation was successful in all. Twenty-four hours after implantation, there was a significant improvement in RV pressure (RVP) (from 82.2 +/- 15.6 to 59.4 +/- 9.9 mmHg, P < 0.001) and degree of PR to 0.6 +/- 0.9 (P < 0.001). Mean hospital stay was 2.0 +/- 0.4 days. Freedom from reintervention was 92 and 89% at 1 and 2 years, respectively. Follow-up echocardiography (mean 12.9 +/- 9.8 months) revealed a further reduction in RVP (P < 0.001) and RVOT gradients (P < 0.001) and an increase in left ventricular end-diastolic volume (P= 0.01) and aortic valve annulus diameters (P < 0.001). CONCLUSIONS Percutaneous pulmonary valve implantation for RVOT dysfunction in a previously implanted prosthetic valve is feasible and safe. Short-term follow-up data are encouraging, yet longer-term information is required to determine if this form of palliation has a significant impact on management strategies.

Intraoperative apical ventricular septal defect closure using a modified Rashkind double umbrella.

OBJECTIVE: To demonstrate the safety and efficacy of intraoperative apical ventricular septal defect (VSD) closure using a modified Rashkind double umbrella. DESIGN: Descriptive study of all patients in whom intraoperative device closure of apical VSDs was attempted. SETTING: A tertiary referral centre. PATIENTS: Four patients with an apical VSD requiring closure, during the period January 1993 to May 1995. INTERVENTIONS: Intraoperative placement of a modified Rashkind umbrella. RESULTS: Four successful placements resulting in apical VSD closure, as judged by transoesophageal colour flow mapping. Three patients received a 17 mm and one a 12 mm umbrella. Early complete closure was achieved in three patients. There was a small residual leak around the 12 mm device that had resolved at 5 month follow up. There was one early death, which was unrelated to VSD closure. CONCLUSION: Apical ventricular septal defects can be closed safely and effectively with intraoperative use of a modified Rashkind umbrella.