Year : 2013  |  Volume : 6  |  Issue : 1  |  Page : 101--104

Selected Summaries

Bhava RJ Kannan 
 Department of Cardiology, Vadamalayan Hospitals, Madurai, India

Correspondence Address:
Bhava RJ Kannan
Department of Cardiology, Vadamalayan Hospitals, Madurai

How to cite this article:
Kannan BR. Selected Summaries.Ann Pediatr Card 2013;6:101-104

How to cite this URL:
Kannan BR. Selected Summaries. Ann Pediatr Card [serial online] 2013 [cited 2021 Dec 8 ];6:101-104
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 Permanent Cardiac Pacing in Children-Choosing the Optimal Pacing Site: A Multi-Center Study

Janousek J, van Geldorp IE, Krupickovα S, Rosenthal E, Nugent K, Tomaske M, et al.

Circulation 2013;127:613-623

Right ventricular (RV) apex is the commonest site of pacing in adults and children. Several adult studies have highlighted the pathologic remodeling and long-term left ventricular LV dysfunction associated with chronic RV pacing. The purpose of this multicenter study was to evaluate the influence of different ventricular pacing sites on long-term LV function in children with non-surgical atrioventricular (AV) block. One hundred and seventy-eight patients aged <18 years (median 3.2 years) at the time of primary pacemaker implantation with >70% ventricular paced beats and absence of any but trivial structural heart disease were selected. AV block was congenital in 138 and diagnosed later in the remaining 40. Maternal auto-antibodies were present in 64 of the 136 mothers tested. Approximate pacing site assignment was performed using QRS morphology and axis and biplane chest X-rays to allow seven categories: RV outflow (RVOT), lateral RV wall (RVLat), RV apex (RVA), RV septum (RVS), LV apex (LVA), lateral LV wall (LVLat) and LV base (LVB). Detailed echo evaluation for LV dimensions, volumes, septal to posterior wall motion delay (SPWMD) and inter-ventricular mechanical delay (IVMD) were done. In addition, speckle tracking analysis was done in 125/178 subjects and wasted LV contraction was calculated for various segments.

Median pacing duration was 5.4 years (3.1-8.8). Ninety-seven patients were paced epicardially and 81 from the endocardium. LVA and LVLat pacing yielded significantly higher shortening fraction and ejection fraction EF than RV pacing sites. LVEF was not significantly different between RVS and RVA pacing. Patients with RVOT and RVLat pacing had the largest scatter in LVEF with the lower quartile as low as <38% in the RVOT group. Compared with basal values, mild decrease in left ventricle enddiastolic dimension was seen in nearly half of RV pacing. Patients with subnormal LVEF (<55%) were almost exclusively confined to RV pacing sites or LV base pacing whereas the vast majority of LAV and LVLat-paced patients had completely preserved LV function. None of the other covariates like maternal auto-antibodies, gender, age at implantation, pacing duration, DDD pacing and QRS duration had significant impact on LVEF. Interventricular and intra-LV delays were significantly more with RV pacing with least negative effect with RVA. LVA and LVLat pacing resulted in minimal dyssynchrony. LVEF was significantly dependent on the degree of LV dyssynchrony. Patients with LV pacing were much younger as older children were preferentially given transvenous RV pacing.

In contrast to adults, children need lifelong pacing which would last for several decades. This study is significant as it has established LVA or LVLat as the optimal pacing sites. Currently LV pacing in children is feasible only by surgical approach. Trans-coronary sinus LV pacing might be an option which needs to be tested.

 Sudden Cardiac Death in Adult Congenital Heart Disease

Koyak Z, Harris L, de Groot JR, Silversides CK, Oechslin EN, Bouma BJ, et al.

Circulation 2012;126:1944-54

Life expectancy has remarkably improved in congenital heart disease (CHD) as a result of better surgical and interventional techniques. Though the annual incidence of sudden cardiac death (SCD) in the entire CHD population is relatively low (0.09%/yr), it is much higher than in age-matched controls. SCD is a prominent cause of death in adults with CHD, about 19-26%. Its prevalence is likely to increase in the future. The authors performed a multicenter case control study to investigate adult patients (>18 years old) with various types of CHD who died suddenly with proven or presumed arrhythmic death. Controls were taken matching the age, gender, diagnosis, type of surgical intervention (prior shunt, palliative or corrective surgery, valve replacements, etc.), date of surgical repair and center.

Overall, 1189 of 25,790 adults (5%) died, of whom 213 died suddenly (19%). The causes of sudden death were: proven or presumed arrhythmia in 171 (80%), aortic dissection or aneurysm rupture in 19 (9%), cerebrovascular accident in 8 (4%), pulmonary embolism/hemorrhage in 8 (4%), myocardial infarction in 4 (2%), and upper gastrointestinal bleeding in 3 patients (1%). Of the 171 SCDs, 118 events (69%) occurred at rest, 19 (11%) during sleep and only 17 (10%) during exercise. Rhythm documentation at the time of the event was available for 37 patients (22%) and showed Ventricular tachycardia ventricular tachycardia (VF) in 23 (62%), ventricular fibrillation (VT) in 4 (11%), combined VT/VF in 4 (11%), supraventricular tachycardia (SVT) in 3 (8%), and bradyarrhythmia in 3 (8%) patients. Neither heart failure symptoms, worse New York Heart Association functional class, nor documented ventricular arrhythmias and antiarrhythmic medication altered the risk of SCD. Cardiac surgery with ventriculotomy and subsequent myocardial scar was not found as a specific risk factor for SCD.

Clinical parameters associated with SCD in multivariate analysis were documented SVTs (OR, 3.5; 95% CI, 1.5-7.9; P = 0.004), QRS duration (OR, 1.34 [per 10-ms increase]; 95% CI, 1.10 -1.34; P = 0.008), QT dispersion (OR, 1.22 [per 10-ms increase]; 95% CI, 1.22-1.48; P = 0.008), moderately to severely impaired systemic ventricular function (OR, 3.4; 95% CI, 1.1-10.4; P = 0.034), and moderately to severely impaired subpulmonary ventricular function (OR, 3.4; 95% CI, 1.1-10.2; P 0.030). Systemic ventricular dysfunction is associated with SCD in a general CHD population, particularly in adults with congenitally corrected transposition of great arteies, (cTGA), cyanotic patients with or without Eisenmenger physiology, and surgically repaired Tetralogy of Fallot TOF patients. Atrial fibrillation was associated with SCD, especially in patients with c-TGA and TOF. Eleven percent of SCDs had septal defects, 89% were closed, the few untreated septal defects were not hemodynamically relevant. Patients with atrial septal defects were older, and potentially, coronary artery disease might have been the cause of SCD.

In this large international study on SCD in adults with CHD, the clinical parameters found to be associated with SCD are similar to those in ischemic heart disease. While QRS duration was an important risk factor, ventriculotomy per se was not found to be a risk factor. Even patients with mild cardiac lesions (septal defects, left ventricular outflow tract obstructions) are potentially at risk for SCD. This study highlights the importance of preserving ventricular function as a means of reducing the risk of SCD.

 Junctional Ectopic Tachycardia after Infant Heart Surgery: Incidence and Outcomes

Zampi JD, Hirsch JC, Gurney JG, Donohue JE, Yu S, LaPage MJ, Hanauer DA, Charpie JR.

Pediatric Cardiol 2012;33:1362-9.

Except for the rare congenital form, junctional ectopic tachycardia (JET) is almost exclusively seen in the immediate postoperative period. Its incidence has been estimated between 3.6 and 10.8% in pediatric cardiac surgeries. Patients who develop JET have increased morbidity as assessed by increased duration of mechanical ventilation and intensive care unit stay, at times it is related to higher mortality too. This study focused on the infant population, aiming to estimate the incidence of postoperative JET, patient- and procedure-related risk factors for JET and postoperative morbidity and mortality related to JET.

Between July 2005 and June 2010, of the 1134 infants who underwent a total of 1451 cardiac surgeries under cardiopulmonary bypass, 162 (14.3%) patients had JET during the postoperative period. There were no statistical differences in race, sex, previous bypass surgery, weight, or body surface area between the cases and age-matched controls, and the use of circulatory arrest was also not associated with JET. On univariate analysis, longer cardiopulmonary bypass (P = 0.03) and aortic cross-clamp times (P = 0.0002) were associated with JET. However, only longer aortic cross-clamp time remained an independent risk factor associated with JET on multivariate analysis [AOR 1.02, 95 % CI 1.01-1.03, P = 0.001]. Only patients with TOF and TOF variants undergoing complete repair were found to be significant independent risk factors for JET. No relation was found with surgeries like TAPVC repair or arterial switch operation. Patients with JET had longer length of intubation (4 vs. 3 days), length of intensive care unit (ICU) stay (7 vs. 5 days), and length of hospitalization (18 vs. 13 days) (all P = <0.0001). In addition, JET patients had a greater chance of requiring ECMO support during their ICU stay (13 vs. 4.3%). There was no difference in the need for cardiopulmonary resuscitation (CPR) (11.7 vs. 7.4%) or 30-day mortality (13 vs. 11.1%) between patients who developed JET compared with controls.

In this large study on postoperative JET, TOF-related surgeries, long cardiopulmonary bypass times and aortic cross-clamp times were associated with increased incidence. The treatment of JET, its success and the influence of the treatment on the overall outcome has not been discussed. While JET was related to increased morbidity, it did not influence the mortality.

 Device Closure of Secundum Atrial Septal Defects in Children <15 Kg: Complication Rates and Indications for Referral

Bartakian S, Fagan TE, Schaffer MS, Darst JR

JACC Cardiovasc Interv 2012;11:1178-84

Device closure of ostium secundum atrial septal defect (ASD) is a standard procedure in the current era in a selected group of patients. A low complication rate is quoted for ASD closure, both surgically or by nonsurgical method. However, these are based on the studies on older and larger patients. The authors aimed to determine the complication rates for elective percutaneous ASD closure in patients <15 kg. Secondary outcomes included indications for early referral, procedural success rates, residual shunt rate, rate of resolution of right heart enlargement and patient growth. Patients with coexisting complex congenital cardiac defects were excluded while those with other medical conditions unrelated to the cardiovascular system, like genetic abnormality or prematurity were included.

During a 10-year period (March 2000 to April 2010), 347 patients had attempted ASD device closure of which 139 (40%) weighed <15 kg. Excluding the 11 patients with complex defects, the study group consisted of 128 patients. The median age was 1.92 years (3 months to 4.92 years) and the median weight was 10.8 kg (4.3 to 14.9 kg). The median ASD diameter measured 9 mm (4.3 to 20 mm). The procedural success rate was 98% with only 1 device removal and 2 patients having their procedure abandoned without a device being placed. The median Qp: Qs was 1.46 and median fluoroscopy time was 17.6 min (5-68 min). Fourteen of them had their patent ductus arteriosus coiled in the same sitting. Amplatzer septal occluder was used in 109 (median size 12), Gore HELEX septal occluder in 15 (median size 25), Cardioseal septal occluder in 3 and Amplatzer cribriform septal occluder in 1.

Twelve patients (9.4%) had short-term minor complications including transient arrhythmia, access site re-bleeding and small pericardial effusion which resolved spontaneously in 4 . There were 7 short-term major complications (5.5%) in 5 patients. There were 3 instances of complete heart block necessitating removal of deployed device, two with Ampltzer device and one with Helex device. Pulmonary hypertensive crisis was noted in one child with Down syndrome while embolic stroke occurred in one patient on the third post-catheterization day. The most common cause of referral was right heart enlargement (34%) while poor growth was the indication in 29%. The rate of resolution of right heart enlargement by the following morning was 50%. It was 88% at one-month follow-up and >92% by 12 to 24 months. Of the patients specifically referred for poor growth, only 2 had significant weight gain of at least 1 SD after the procedure during the follow-up period.

Considering the fact that defects as large as 8 mm could spontaneously close, the median diameter of 10 mm in this study suggests that many of these defects may have closed spontaneously had they been not intervened . Though left to right shunts could cause failure to thrive, there is no evidence that an isolated secundum ASD will cause a significant increase in metabolic demand to cause a decline in growth. This is substantiated in this study that ASD device closure did not result in expected growth in those who were primarily referred for poor growth. Considering the significant major complications' rate, authors recommended deferral of closure of ASD until the historically established timeline of around 4 to 5 years.

 Fluid Overload in Infants Following Congenital Heart Surgery

Hazle MA, Gajarski RJ, Yu S, Donohue J, Blatt NB

Pediatr Crit Care Med 2013;14:1-6.

Fluid overload (FO) is common following infant congenital heart surgery with cardiopulmonary bypass (CPB). It is an important clinical marker of renal dysfunction and has been correlated with increased duration of mechanical ventilation, prolonged intensive care and hospital lengths of stay. This study was designed to study postoperative FO patterns in infants undergoing congenital heart surgery and its impact on mortality and morbidity.

This was a prospective study on infants under 6 months of age undergoing cardiac surgery with CPB between July 2009 and July 2010. All patients received routine care including use of dextrose solution during the first 24-48 h postoperatively followed by total parenteral nutrition. All were started on bolus furosemide (1mg/kg/dose q6h) with the first 24 h. FO was calculated using two methods:

([fluid in - fluid out] / preoperative kg weight) × 100

([current kg weight - preoperative kg weight] / preoperative kg weight) × 100

Acute kidney injury was defined if the serum creatinine S. Cr increased by either ≥0.3 mg/dl or there was a 50% rise from the preoperative baseline with the first 3 days postoperatively. Composite outcome of need for continuous renal replacement therapy (CRRT), time to first extubation or ICU stay or death within 30 days was used for analysis.

Forty-nine patients were studied. Except for an infant who underwent a Stage 2 hemi-Fontan operative, all others underwent their initial reparative or palliative surgery. The most common surgeries were VSD closure (12), TOF repair (9), HLHS (9), AVSD repair (6) and DTGA repair (5). Seventeen (35%) had at least one poor outcome and were younger in age, smaller and underwent more complex surgical procedures. Six patients needed ECMO in the immediate postoperative period for low cardiac output syndrome. Two of them needed CRRT and subsequently died. One more child died, 12 had prolonged time to first extubation and 16 had prolonged ICU stay.

Poor outcome patients had a greater degree of maximal FO both by fluid balance and daily weight methods and they took longer to achieve a negative fluid balance. Maximal FO <10% was associated with a good outcome and maximal FO of >20% was associated with a poor outcome. There were 13 patients who had >10% FO by both methods; 8 of these (62%) had a poor outcome (P=0.04). From multivariate analysis, CPB time, use of circulatory arrest and maximum vasoactive inotrope score remained statistically significant predictors of a poor outcome. As many as 86% had acute kidney injury but only two received CRRT. Thus, FO assessed by daily weight method was a significant predictor of a poor outcome after adjusting for S. Cr. indicating that FO may be a clinically useful parameter independent of the degree of acute kidney injury based on current definitions.

 Warfarin Anticoagulation after Congenital Heart Surgery at A Large Children's Hospital

Lowry AW, Moffett BS, Moodie D, Knudson JD

Pediatr Cardiol 2012;33:1377-82.

Management of warfarin therapy for pediatric patients remains a challenge. This study aimed to measure the time required to reach anticoagulation for patients administered warfarin therapy after cardiac surgery and to characterize the risk factors for supratherapeutic anticoagulation and adverse events after warfarin initiation. Fifty-nine patients had received warfarin between 2006 and 2011. The primary indication for warfarin was mechanical valve placement and it was planned to maintain a therapeutic goal (INR value) of 2.0-3.0 for aortic prosthesis and between 2.5 and 3.5 for other valve positions. The loading dose was 0.2 mg/kg. In patients with liver dysfunction (Basal INR >1.3) or those with Fontan palliation, a lower loading dose of 0.1 mg/kg was used.

The median time required to reach an INR of at least 2 after initiation of warfarin was 2 days (interquartile range (IQR), 2-4) and only 25% required more than 4 days. As the half-life of Vit K-dependent coagulant factors is long, one would expect around 3 to 4 days for the therapeutic effect of Vit K antagonists. The authors hypothesize that the decreased time required to reach an INR of 2 in patients starting warfarin sooner after surgery may be secondary to transient cardiopulmonary-bypass-associated hepatic dysfunction. Unfortunately, hepatic synthetic function data were not available for a sufficient number of postoperative patients to permit testing of this hypothesis.

The only groups that required a significantly longer time to reach an INR of 2 were those with a postoperative delay in initiation of warfarin and those receiving heparin anticoagulation before and during warfarin initiation. Those who received heparin bridge had a more complicated postoperative course, received more blood transfusions and were loaded with a significantly lower warfarin dose. Nine patients experienced an INR of 4 or more. Three patients had a clinically significant bleeding event and four patients needed vitamin K. There was no significant association between elevated INR and age, body mass index (BMI), time since cardiac surgery, time required to reach an INR exceeding 2, or baseline INR value at initiation of warfarin. The factors related to a supratherapeutic INR were larger loading dose and greater maximum dose at any point during the warfarin load.

In this largest reported group of patients receiving anticoagulation after cardiac surgery, warfarin was well tolerated across all age groups using standardized dosing protocols and close follow-up. The need for heparin bridge identifies a sicker patient who would be expected to take a longer time to reach therapeutic INR level.