Douglas Y. Mah

Incidence and Risk Factors for Mortality in Infants Awaiting Heart Transplantation in the USA

BACKGROUND Infants awaiting heart transplantation (HT) face the highest wait-list mortality among all children and adults listed for HT in the USA. We sought to determine the risk of death for infants <12 months old while awaiting HT in the current era, and to identify the principle risk factors associated with wait-list mortality. METHODS We analyzed outcomes for all infants listed for HT in the USA from January 1999 to July 2006, using data reported to the U.S. Scientific Registry of Transplant Recipients. RESULTS Of the 1,133 listed infants, 61% were <3 months of age, 80% were listed as Status 1A, 64% had a congenital heart disease (CHD) and 31% had cardiomyopathy. Of 724 infants with CHD, 25% were on prostaglandin (PG) and 27% had a history of prior surgery. By 6 months after listing, 23% died on the wait-list and 54% were transplanted. Multivariate factors associated with wait-list mortality were weight <3 kg (hazard ratio [HR] 1.4, 95% confidence interval [CI] 1.0 to 1.9), extracorporeal membrane oxygenation (ECMO) support (HR 5.6, CI 4.0 to 7.9), ventilator support (HR 2.1, 95% CI 1.6 to 2.8), CHD with PG support (HR 2.8, 95% CI 1.8 to 4.3), CHD without prior surgery (HR 2.8, 95% CI 1.9 to 3.9) and non-white race/ethnicity (HR 1.8, 95% CI 1.4 to 2.3). CONCLUSIONS One in four infants listed for HT in the USA die before a donor heart can be identified. Wait-list mortality is associated with weight <3 kg, level of invasive support and CHD, but not listing status, which captures medical urgency poorly. Measures to expand infant organ donation, especially among neonates, are urgently needed.

Nonfluoroscopic imaging systems reduce radiation exposure in children undergoing ablation of supraventricular tachycardia

BACKGROUND The current standard of care for imaging during supraventricular tachycardia (SVT) ablation uses fluoroscopy, which exposes otherwise healthy children to the potential harmful effects of radiation. OBJECTIVE The purpose of this study was to determine whether the adjunct use of nonfluoroscopic imaging reduces radiation exposure during SVT ablation among children. METHODS This was a prospective, controlled, single-center study of patients age ≥8 years, weight ≥25 kg, with SVT and normal cardiac anatomy. Patients were randomized to control (fluoroscopy only) or study group (fluoroscopy + AcuNav intracardiac ultrasound + NavX electroanatomic mapping), stratified by operator to one of five electrophysiologists. Fluoroscopy times (minutes) and radiation doses (mGy) were recorded, and outcomes and adverse events were noted. RESULTS Seventy-four patients were enrolled (37 control, 37 study). Median age was 14.7 years (range 8.6-22.3 years); 61% had accessory pathways and 39% had atrioventricular nodal reentrant tachycardia. Nonfluoroscopic imaging reduced median fluoroscopy time by 59% (18.3 minutes vs 7.5 minutes, P <.001) and radiation exposure by 72% (387 vs 110 mGy, P <.001). In the study group, 26 of 37 had ≤10 minutes of fluoroscopy, including 2 with no fluoroscopy exposure and 2 with <30 seconds. Electrophysiologic procedure time was not affected by use of nonfluoroscopic imaging, but total case times were prolonged by 31 minutes (P <.001). Acute success was 97% in control and 100% in study patients, with no difference in adverse events. CONCLUSION Use of nonfluoroscopic imaging during SVT ablation in children resulted in substantial and immediate reductions in fluoroscopy time and radiation exposure without change in acute success or adverse event rates but did increase overall procedural time.

Impact of Cardiac Devices on the Quality of Life in Pediatric Patients

Background— Cardiac rhythm devices are increasingly used in the pediatric population, although their impact on quality of life (QOL) is poorly understood. The purpose of this study was to compare (QOL) scores among pediatric device patients, healthy controls, and congenital heart disease (CHD) patients and determine the key drivers of QOL in pediatric device patients. Methods and Results— Multicenter, cross-sectional study at 8 pediatric centers of subjects aged 8 to 18 years with either a pacemaker or defibrillator was carried out. Patient–parent pairs completed the Pediatric Quality of Life Inventory and Pediatric Cardiac Quality of Life Inventory. QOL outcomes in device patients were compared with healthy controls and patients with various forms of CHD. Structural equation modeling was used to test for differences in Pediatric Cardiac Quality of Life Inventory scores among (1) device type, (2) presence of CHD, and (3) hypothesized key drivers of QOL. One hundred seventy-three patient–parent pairs (40 defibrillators/133 pacemakers) were included. Compared with healthy controls, patients with devices and their parents reported significantly lower Pediatric Quality of Life Inventory scoring. Similarly, compared with patients with mild forms of CHD, parents and patients with devices reported significantly lower Pediatric Cardiac Quality of Life Inventory scores and were similar to patients with more severe CHD. Key drivers of patient QOL were presence of implantable cardioverter-defibrillator and CHD. For patients, self-perception was a key driver of lower QOL, whereas for parents behavioral issues were associated with lower QOL. Conclusions— Patient QOL is significantly affected by the presence of cardiac rhythm devices. Whether these effects can be mitigated through the use of psychotherapy needs to be assessed.

The Electroanatomic Mechanisms of Atrial Tachycardia in Patients with Tetralogy of Fallot and Double Outlet Right Ventricle

Atrial Tachycardia in Tetralogy of Fallot and DORV. Background: Atrial tachycardias (AT) are common after palliation or repair of congenital heart disease. The electroanatomic mechanism of AT in postoperative tetralogy of Fallot (TOF) and double outlet right ventricle (DORV) patients has not been fully explored.

The use of an integrated electroanatomic mapping system and intracardiac echocardiography to reduce radiation exposure in children and young adults undergoing ablation of supraventricular tachycardia

AIMS Non-fluoroscopic imaging (NFI) devices are increasingly used in ablations. The objective was to determine the utility of intracardiac echocardiography (ICE) in ablating paediatric supraventricular tachycardias (SVTs) and assess whether its integrated use with electroanatomic mapping (EAM) resulted in lower radiation exposure than use of EAM alone. METHODS AND RESULTS Prospective, controlled, single-centre study of patients (pts) age ≥10 years, weight ≥35 kg, with SVT and normal cardiac anatomy. Patients were randomized to ICE + EAM (ICE) or EAM only (no ICE). Both had access to fluoroscopy as needed. Eighty-four pts were enroled (42 ICE, 42 no ICE). Median age was 15 years (range 10.4-23.7 years); 57% had accessory pathways, 42% atrioventricular nodal reentry tachycardia. There was no difference in radiation dose (9 mGy ICE vs. 23 mGy no ICE, P = 0.37) or fluoroscopy time (1.1 min ICE vs. 1.5 min no ICE, P = 0.38). Transseptal punctures were performed in 25 pts (16 ICE, 9 no ICE), with ICE reducing radiation (8 mGy ICE vs. 62 mGy no ICE, P = 0.002) and fluoroscopy time (1.1 min ICE vs. 4.5 min no ICE, P = 0.01). Zero fluoroscopy was achieved in 13 pts (15% of total, 5 ICE, 8 no ICE), and low-dose cases (<50 mGy) in 57 pts (68% of total, 33 ICE, 24 no ICE). Acute success was 95% for ICE, 88% for no ICE. CONCLUSION Use of an integrated EAM/ICE system was no better than EAM alone in limiting radiation, but can be helpful for transseptal punctures. Given the low dose savings, use of ICE may be weighed against its financial cost. Low-fluoroscopy cases are performed in most NFI procedures.

Mechanism and Ablation of Arrhythmia Following Total Cavopulmonary Connection

Background—The ability to identify and ablate different arrhythmia mechanisms after the total cavopulmonary connection has not been studied in detail. Methods and Results—After obtaining Institutional Review Board approval according to institutional guidelines, consecutive patients after a total cavopulmonary connection undergoing electrophysiology study over a 6-year period were included (2006–2012). Arrhythmia mechanism was determined, and the procedural outcome was defined as complete, partial success, or failure. A 12-point arrhythmia severity score was calculated for each patient at baseline and on follow-up. Fifty-seven procedures were performed on 52 patients (18.4±11.8 years; 53.0±27.2 kg). Access to the pulmonary venous atrium was necessary in 33 procedures, via fenestration (16) or transbaffle puncture (17), and in 2 cases, an additional retrograde approach was used. In total, 80 arrhythmias were identified in 47 cases: macroreentrant (n=25) or focal atrial tachycardia (n=8), atrioventricular nodal reentry tachycardia (n=13), reentry via an accessory pathway (n=4) or via twin atrioventricular nodes (n=4), ventricular tachycardia (n=5), and undefined atrial tachycardia (n=21). Procedural outcome in 32 patients who underwent ablation was complete success (n=25), partial success (n=3), failure (n=3), or empirical ablation (n=1). After successful ablation, there was a significant decrease in arrhythmia score over 18.2 (4–32) months follow-up, with a sustained trend even in the face of arrhythmia recurrence (50%). Conclusions—Arrhythmia mechanism post total cavopulmonary connection is highly varied, encompassing simple and more complex substrates, documentation of which facilitates a strategic approach to invasive arrhythmia management. Despite the anatomic limitations, successful and clinically meaningful ablation is possible.

Transbaffle Mapping and Ablation for Atrial Tachycardias After Mustard, Senning, or Fontan Operations

Background In Fontan and atrial switch patients, transcatheter ablation is limited by difficult access to the pulmonary venous atrium. In recent years, transbaffle access (TBA) has been described, but limited data document its safety and utility. Methods and Results All ablative electrophysiological study cases of this population performed between January 2006 and December 2010 at Boston Childrens Hospital were reviewed. Pre‐case and follow‐up clinical characteristics were documented. Adverse events were classified by severity and attributability to the intervention. We included 118 cases performed in 90 patients. TBA was attempted in 74 cases and was successful in 96%: in 20 via baffle leak or fenestration and in 51 (94%) of 54 using standard or radiofrequency transseptal techniques. There were 10 procedures with adverse events ranked as moderate or more severe. The event rate was similar in both groups (TBA 8% versus non‐TBA 9%, P=1), and no events were directly attributable to TBA. There was a trend to higher proportion of cases having a >5‐point drop in saturations from baseline in the TBA group versus the non‐TBA group in Fontan cases (15% vs 0%, P=0.14). When cases with follow‐up >90 and >365 days were analyzed, the median initial arrhythmia score of 5 significantly changed −3 points in both time periods (P≤0.001). Conclusions TBA is feasible in this population; its use was not associated with a higher incidence of adverse events; and changes in clinical scores support its efficacy. Desaturation observed in some patients is of uncertain significance but warrants postablation monitoring and prospective study.

In-Hospital Arrhythmia Development and Outcomes in Pediatric Patients With Acute Myocarditis

Cardiac arrhythmias are a complication of myocarditis. There are no large studies of in-hospital arrhythmia development and outcomes in pediatric patients with acute myocarditis. This was a retrospective 2-center review of patients ≤21 years hospitalized with acute myocarditis from 1996 to 2012. Fulminant myocarditis was defined as the need for inotropic support within 24 hours of presentation. Acute arrhythmias occurred at presentation and subacute after admission. Eighty-five patients (59% men) presented at a median age of 10 years (1 day to 18 years). Arrhythmias occurred in 38 patients (45%): 16 acute, 12 subacute, and 9 acute and subacute (1 onset unknown). Arrhythmias were associated with low voltages on the electrocardiogram (14 of 34, 41% vs 6 of 47, 13%; odds ratio [OR] 4.78, 95% confidence interval [CI] 1.60 to 14.31) and worse outcome (mechanical support, orthotopic heart transplant, or death; OR 7.59, 95% CI 2.61 to 22.07) but were not statistically significantly associated with a fulminant course, ST changes, initial myocardial function, lactate, creatinine level, C-reactive protein and/or erythrocyte sedimentation rate, or troponin I level, after adjusting for multiple comparisons. Subacute arrhythmias were associated with preceding ST changes (10 of 15, 67% vs 15 of 59, 25%, OR 5.87, 95% CI 1.73 to 19.93). All patients surviving to discharge had arrhythmia resolution or control before discharge (10 on antiarrhythmic), with 1 exception (patient with complete heart block requiring a pacemaker). At 1-year follow-up, there were 3 recurrences of ventricular arrhythmias, but no arrhythmia-related mortality. In conclusion, arrhythmias are common in pediatric patients with myocarditis, occurring in nearly 1/2 of all hospitalized children and are associated with a worse outcome. Early identification of subacute arrhythmias using electrocardiographic changes may help management. A majority of patients do not require continued postdischarge arrhythmia treatment.

Epicardial left atrial appendage and biatrial appendage accessory pathways

BACKGROUND Acute success rates of accessory pathway ablation for Wolff-Parkinson-White (WPW) syndrome can exceed 95%, with rare failures attributed to anatomically complex epicardial connections. Right atrial appendage to right ventricle pathways have been reported, but their left-sided counterparts have only recently been described. OBJECTIVE The purpose of this study was to report three unique cases of WPW syndrome in children with left atrial appendage and biatrial appendage connections. RESULTS Three young patients with high-risk accessory pathways (accessory pathway effective refractory period = 190-240 ms) had unsuccessful endocardial ablations despite aggressive efforts with various catheter techniques. One patient had a left atrial appendage to left ventricular connection; the other two had biatrial appendage pathways connected to their respective ventricular surfaces. The latter two patients had a history of ventricular fibrillation: one experiencing ventricular fibrillation in the electrophysiology laboratory and the other suffering from ventricular fibrillation arrest at home. All three patients were taken to the operating room, where the appendages were noted to be diffusely adherent to their ventricles by fibrofatty connections. Dissection of the appendages led to loss of preexcitation and no further tachycardia. CONCLUSION Surgical management of atrial appendage accessory pathways should be considered if aggressive attempts at endocardial ablation have failed.

Impact of pacing on systemic ventricular function in L-transposition of the great arteries

OBJECTIVE(S) To assess the impact of univentricular versus biventricular pacing (BiVP) on systemic ventricular function in patients with congenitally corrected transposition of the great arteries (ccTGA). METHODS We performed a retrospective review of all patients with a diagnosis of ccTGA who underwent pacemaker insertion. From 1993 to 2014, 53 patients were identified from the cardiology database and surgical records. RESULTS Overall mortality was 7.5% (n = 4). One patient required transplantation and 3 late deaths occurred secondary to end-stage heart failure. Median follow-up was 3.7 years (range, 4 days to 22.5 years). Twenty-five (47%) underwent univentricular pacing only, of these, 8 (32%) developed significant systemic ventricular dysfunction. Twenty-eight (53%) received BiVP, 17 (26%) were upgraded from a dual-chamber system, 11 (21%) received primary BiVP. Fourteen (82%) of the 17 undergoing secondary BiVP demonstrated systemic ventricular dysfunction at the time of pacer upgrade, with 7 (50%) demonstrating improved systemic ventricular function after pacemaker upgrade. Overall, 42 (79%) patients underwent univentricular pacing, with 22 (52%) developing significant systemic ventricular dysfunction. In contrast, the 11 (21%) who received primary BiVP had preserved systemic ventricular function at latest follow-up. CONCLUSIONS Late-onset systemic ventricular dysfunction is a major complication associated with the use of univentricular pacing in patients with ccTGA. All patients with ccTGA who develop heart block should undergo primary biventricular pacing, as this prevents late systemic ventricular dysfunction. Preemptive placement of BiVP leads at the time of anatomical repair or other permanent palliative procedure will facilitate subsequent BiVP should heart block develop.