Dingchao He

Intra/extracardiac fenestrated modification leads to lower incidence of arrhythmias after the Fontan operation

OBJECTIVE The study objective was to compare the incidence of short- and intermediate-term arrhythmias among 3 different surgical modifications of the Fontan procedure. METHODS We performed a retrospective review of all patients who underwent the Fontan operation at a single institution between January 2004 and May 2010 for preoperative, perioperative, and follow-up variables. Three surgical modifications were studied: intra/extracardiac conduit with limited atriotomy, standard extracardiac conduit, and lateral tunnel. Rhythm was classified as normal or abnormal. A rhythm dysfunction grading was devised and used to identify worsening of rhythm for patients with abnormal rhythm preoperatively. Multivariable logistic regression was used to determine predictors of abnormal rhythm. To eliminate confounding effects of transient immediate postoperative arrhythmias, data were analyzed for abnormal rhythm within the first 2 weeks and for more than 2 weeks after surgery. RESULTS Of the 134 patients (n = 50 with intra/extracardiac conduit with limited atriotomy, n = 19 with standard extracardiac conduit, n = 65 with lateral tunnel) (median follow-up, 36 months; interquartile range, 22-50 months; 2 operative deaths and 6 late deaths), rhythm data for more than 2 weeks postoperatively were available in 88 (40 with lateral tunnel, 14 with standard extracardiac conduit, 34 with intra/extracardiac conduit with limited atriotomy). These patients constituted the study groups. Patients in the lateral tunnel group were relatively younger at the time of the Fontan operation (P < .001) and had a longer follow-up (P < .001). Multivariable logistic regression confirmed that greater than moderate atrioventricular valve regurgitation was the only independent predictor of abnormal rhythm during the first 2 postoperative weeks. Older age at Fontan (odds ratio, 1.20; 95% confidence interval, 1.05-1.38; P = .012) and higher preoperative mean pulmonary artery pressure (odds ratio, 1.2; 95% confidence interval, 1.03-1.44; P = .026) were predictors of abnormal rhythm more than 2 weeks postoperatively. Intra/extracardiac conduit with limited atriotomy Fontan modification was associated with a significantly lower incidence of abnormal rhythm after 2 weeks postoperatively compared with lateral tunnel modification (odds ratio, 0.28; 95% confidence interval, 0.10-0.84; P = .015). CONCLUSIONS Intra/extracardiac conduit with limited atriotomy Fontan modification has a significantly lower risk of abnormal rhythm postoperatively in the short and intermediate term when compared with the lateral tunnel.

Newly created animal model of human postoperative junctional ectopic tachycardia.

OBJECTIVE Junctional ectopic tachycardia complicates the postoperative recovery from open heart surgery in children. The reported risk factors include younger age, prolonged cardiopulmonary bypass times, and administration of inotropic agents. Junctional ectopic tachycardia occurs early after open heart surgery, in the setting of relative postoperative sinus node dysfunction, and exhibits QRS morphology consistent with an origin from the atrioventricular node or proximal conduction system. Our goal was to develop a reproducible animal model for postoperative junctional ectopic tachycardia. METHODS Eleven pigs, aged 2 to 4 months, underwent open heart surgery after induction of general anesthesia. Electrodes were sewn to the left atrium and right ventricle. RESULTS Sinus node dysfunction was created using clamp crushing without or with radiofrequency ablation (successful in 1 of 5 pigs) or sinus node removal (successful in 4 of 4). After prolonged cardiopulmonary bypass (>120 minutes) alone and with isoproterenol infusion, no spontaneous junctional ectopic tachycardia developed. Junctional ectopic tachycardia or fascicular tachycardia could be initiated after either slow atrioventricular nodal pathway ablation and/or digoxin administration. Junctional ectopic tachycardia occurred in 8 of 9 pigs (mean ventricular rate, 171 ± 32 bpm), and fascicular tachycardia occurred in 9 of 9 pigs (mean ventricular rate, 187 ± 39 bpm). His and right bundle recordings confirmed the conduction system origin. CONCLUSIONS Experimental junctional ectopic tachycardia or fascicular tachycardia can occur in the intraoperative setting of sinus node dysfunction, prolonged cardiopulmonary bypass, and enhanced conduction system automaticity. Conduction system automaticity occurred after either physical injury (ablation or tricuspid valve stretch) or measures to augment the transient inward current of the conduction system (isoproterenol and digoxin). This animal model can serve as the basis to assess new treatments of postoperative junctional ectopic tachycardia.

Lower risk of postoperative arrhythmias in congenital heart surgery following intraoperative administration of magnesium

Objectives Postoperative arrhythmias are common in children undergoing congenital heart surgery. We evaluated whether intraoperative administration of magnesium was associated with a reduced occurrence of specific postoperative arrhythmias, as has been described previously, or had a broader effect on multiple arrhythmia types, and whether there existed a dose–effect of intraoperative magnesium. Methods We used a historical prospective observational cohort study. Propensity score matching using logistic regression was applied to establish similar populations of treatment groups balanced on 5 important covariates. Results Based on propensity score–matched groups, magnesium 50 mg/kg administration was associated with a reduced odds of occurrence of postoperative arrhythmias: any arrhythmia (odds ratio [OR] = 0.50, P < .001), junctional ectopic tachycardia (OR = 0.56, P = .004), accelerated junctional rhythm (OR = 0.56, P = .089), atrial tachycardia (OR = 0.48, P = .005), ventricular tachycardia (OR = 0.52, P = .04), and atrioventricular block (OR = 0.47, P = .03). The effect of magnesium on reducing the odds of occurrence of postoperative arrhythmias did not differ between 25 mg/kg versus 50 mg/kg. Conclusions As many as one third of our patients undergoing congenital heart surgery had postoperative arrhythmias. Use of intraoperative magnesium was associated with a reduction in the odds of occurrence of all postoperative arrhythmias. Our results do not provide evidence that a greater dose of magnesium is associated with greater arrhythmia risk reduction. Despite the intraoperative use of magnesium, there continued to be a high residual incidence of postoperative arrhythmias, raising the question for studying new or additional agents.

Congenital Aneurysm of the Aortomitral Intervalvular Fibrosa

A 5-year-old boy was found to have a congenital left ventricular outflow tract (LVOT) aneurysm of the intervalvular fibrosa, LVOT obstruction after repair of a perimembranous ventricular septal defect, and aortic coarctation. The patient underwent successful plication of the aneurysm, resection of the fibrous subaortic stenosis, and septal myectomy.

Radiofrequency catheter ablation of intractable ventricular tachycardia in an Infant following arterial switch operation

A full-term male neonate presented with cyanosis upon delivery and was subsequently diagnosed with d-transposition of the great arteries, ventricular septal defect, and restrictive atrial septal defect. Following initiation of intravenous prostaglandins and balloon atrial septostomy, an arterial switch operation was performed on day 3 of life. The postoperative course was complicated by intractable ventricular tachycardia that was refractory to lidocaine, amiodarone, esmolol, fosphenytoin, and mexiletine drug therapy. Ventricular tachycardia was suppressed with overdrive atrial pacing but recurred upon discontinuation. Seven weeks postoperatively, radiofrequency catheter ablation was performed due to hemodynamically compromising persistent ventricular tachycardia refractory to medical therapy. The ventricular tachycardia was localized to the inferior-lateral right ventricular outlet septum. The procedure was successful without complications or recurrence. Antiarrhythmics were discontinued after the ablation procedure. Seven days after the ablation, a different, slower fascicular rhythm was noted to compete with the infants sinus rhythm. This was consistent with the preablation amiodarone having reached subtherapeutic levels given its very long half-life. The patient was restarted on oral beta blockers and amiodarone. The patient was subsequently discharged home in predominantly sinus rhythm with intermittent fascicular rhythm.

Nonpharmacologic Control of Postoperative Supraventricular Arrhythmias Using AV Nodal Fat Pad Stimulation in a Young Animal Open Heart Surgical Model

Background—Supraventricular arrhythmias (junctional ectopic tachycardia [JET] and atrial tachyarrhythmias) frequently complicate recovery from open heart surgery in children and can be difficult to manage. Medical treatment of JET can result in significant morbidity. Our goal was to develop a nonpharmacological approach using autonomic stimulation of selective fat pad (FP) regions of the heart in a young canine model of open heart surgery to control 2 common postoperative supraventricular arrhythmias. Methods and Results—Eight mongrel dogs, varying in age from 5 to 8 months and weighting 22±4 kg, underwent open heart surgery replicating a nontransannular approach to tetralogy of Fallot repair. Neural stimulation of the right inferior FP was used to control the ventricular response to supraventricular arrhythmias. Right inferior FP stimulation decreased baseline AV nodal conduction without altering sinus cycle length. AV node Wenckebach cycle length prolonged from 270±33 to 352±89 ms, P=0.02. Atrial fibrillation occurred in 7 animals, simulating a rapid atrial tachyarrhythmias. FP stimulation slowed the ventricular response rate from 166±58 to 63±29 beats per minute, P<0.001. Postoperative JET occurred in 7 dogs. FP stimulation slowed the ventricular rate during postoperative JET from 148±31 to 106±32 beats per minute, P<0.001, and restored sinus rhythm in 7/7 dogs. Conclusions—Right inferior FP stimulation had a selective effect on the AV node, and slowed the ventricular rate during postoperative JET and atrial tachyarrhythmias in our young canine open heart surgery model. FP stimulation may be a useful new technique for managing children with JET and atrial tachyarrhythmias.

Pump in Parallel-Mechanical Assistance of Partial Cavopulmonary Circulation Using a Conventional Ventricular Assist Device.

Mechanical assistance of systemic single ventricle is effective in pulling blood through a cavopulmonary circuit. In patients with superior cavopulmonary connection, this strategy can lead to arterial desaturation secondary to increased inferior caval flow. We hypothesized that overall augmentation in cardiac output with mechanical assistance compensates for the drop in oxygen saturation thereby maintaining tissue oxygen delivery (DO2). Bidirectional Glenn (BDG) was established in seven swine (25 kg) after a common atrium had been established by balloon septostomy. Mechanical circulatory assistance of the single ventricle was achieved using an axial flow pump with ventricular inflow and aortic outflow. Cardiac output, mean pulmonary artery pressure (PAP), common atrial pressure (left atrial pressure [LAP]), arterial oxygen saturation (SaO2), partial pressure of arterial oxygen (PaO2), and DO2 were compared between assisted and nonassisted circulation. Significant augmentation of cardiac output was achieved with mechanical assistance in BDG circulation (BDG: median [interquartile range {IQR}], 0.8 [0.9–1.15] L/min versus assisted BDG: median [IQR], 1.5 [1.15–1.7] L/min; p = 0.05). Although oxygen saturations and PaO2 trended to be lower with assistance (SaO2; BDG: median [IQR], 43% [32–57%]; assisted BDG: median [IQR], 32% [24–35%]; p = 0.07) (PaO2; BDG: median [IQR], 24 [20–30] mm Hg; assisted BDG: median [IQR], 20 [17–21] mm Hg; p = 0.08), DO2 was unchanged with mechanical assistance (BDG: median [IQR], 94 [35–99] ml/min; assisted BDG: median [IQR], 79 [63–85] ml/min; p = 0.81). No significant change in the LAP or PAP was observed. In the setting of superior cavopulmonary connection/single ventricle, the systemic ventricular assistance with a ventricular assist device (VAD) leads to increase in cardiac output. Arterial oxygen saturations however may be lower with mechanical assistance, without any change in DO2.

Palliation of Truncus Arteriosus Associated With Complete Atrioventricular Canal-Results of Single Ventricle Palliation.

Background: Truncus arteriosus associated with complete atrioventricular canal defect is rare and continues to be a surgical challenge with high morbidity and mortality. In the absence of extension of the ventricular septal defect to the outlet septum, biventricular repair is precluded, and single ventricle palliation remains the only option. We present our experience with five patients with truncus arteriosus and complete atrioventricular canal defect who underwent single ventricular palliation. Methods: Five patients with truncus arteriosus and complete atrioventricular canal defect managed along the single ventricle palliation pathway were retrospectively reviewed. Demographic, echocardiographic, cardiac catheterization, and perioperative data were analyzed. Results: All patients underwent neonatal palliation tailored to their anatomy (excision of pulmonary arteries from the common trunk and systemic to pulmonary artery shunt in two patients, excision of pulmonary artery and right ventricle to pulmonary artery conduit in two patients, and bilateral branch pulmonary artery bands in one patient). There were two early deaths after neonatal palliation. At a median follow-up of 210 days (interquartile range 1,210 days), all three survivors have undergone second-stage palliation. Of these patients, one is interstage II to III, and two patients have completed their Fontan procedure and are doing well. Conclusion: Truncus arteriosus with complete atrioventricular canal defect is a rare combination of defects. Single ventricle palliation pathway with a tailored neonatal approach may be employed for patients with uncommitted ventricular septal defects.

Pulmonary overcirculation following left atrial decompression in hypoplastic left heart syndrome with intact/restrictive atrial septum.

Abstract  Patients with hypoplastic left heart syndrome (HLHS) with intact or severely restrictive atrial septum have slow resolution of their elevated pulmonary vascular resistance after left atrial decompression. We report two neonates who required urgent surgical intervention because of unusually rapid fall in their pulmonary vascular resistance following left atrial decompression leading to pulmonary overcirculation and severe congestive heart failure. HLHS with intact or severely restrictive atrial septum is a predictor of poor outcome. The need for left atrial decompression can be predicted by well defined fetal echocardiographic indicators. However evolution of pulmonary resistance can be difficult to predict. In some patients decompression of the left atrium can lead to early excessive pulmonary blood flow and congestive heart failure requiring urgent intervention. Here, we report two cases of HLHS with highly restrictive atrial septum that after atrial septostomy had an accelerated transition requiring urgent intervention. Because of retrospective nature of the study, Childrens National Medical Center approved waiver of informed consent. (J Card Surg 2012;27:758‐759)

Complete Atrioventricular Canal With Guarded Primum Septal Defect

Common atrioventricular canal (CAVC) is a common congenital heart lesion resulting from a defect in development of the endocardial cushions during early embryogenesis. Depending on the type of defect, CAVC can encompass a spectrum of lesions ranging from partial atrioventricular (AV) canal to complete AV canal. We describe a case of CAVC with unique anatomy in a 4-month-old male infant with Down syndrome.