Kara S. Motonaga

Cardiac Resynchronization Therapy for Pediatric Patients With Heart Failure and Congenital Heart Disease A Reappraisal of Results

Cardiac resynchronization therapy (CRT) is an effective treatment for adult patients with left ventricular (LV) failure. Large prospective, randomized, controlled trials have demonstrated that CRT results in improvement in cardiac function, LV reverse remodeling, decreased hospitalizations for heart failure (HF), improved quality of life, and decreased overall mortality.1–5 However, 30% of adult patients are nonresponders to CRT, spurring further evaluation of electromechanical dyssynchrony to determine optimal pacing sites and to improve CRT selection criteria for maximal response.1,6 The positive response in adult HF prompted exploration of the use of CRT in pediatric HF patients. However, the effectiveness of CRT in the pediatric population is difficult to evaluate because of the complex anatomic substrates of congenital heart disease (CHD) and scar formation from multiple cardiac surgeries with a higher proportion of right bundle-branch block (RBBB) and right ventricular (RV) failure than in the adult population. The typical adult HF scenario of an LV ejection fraction (EF) ≤35% with a left bundle-branch block (LBBB) is uncommon in children; therefore, the adult selection criteria for CRT cannot be easily translated to pediatric patients. Furthermore, a small heterogeneous pediatric patient population hinders a systematic assessment of long-term benefit from CRT. In the normal heart, ventricular electrical activation spreads through the His-Purkinje system, which has unique rapid propagation properties and widespread distribution. This allows highly coordinated electrical activation between distant regions of both ventricles, resulting in highly synchronous mechanical contraction. Given the strong relationship between electrical excitation and mechanical contraction in the myocardium, it is not surprising that abnormal electrical activation results in abnormal mechanical contraction.7,8 During a spontaneous or pacing-induced bundle-branch block, ventricular activation spreads primarily cell to cell through the surrounding myocardium, which can be up to 4 times slower than the specialized His-Purkinje …

The effects of ketamine on dexmedetomidine-induced electrophysiologic changes in children.

Dexmedetomidine is an alpha2‐adrenergic agonist used for sedation and analgesia in children. We previously showed that dexmedetomidine depresses sinus and AV nodal function resulting in adverse hemodynamic effects such as bradycardia and increased blood pressure. We hypothesized that these effects of dexmedetomidine might be antagonized by co‐administration of ketamine, which has sympathomimetic properties.

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.

Intranasal oxytocin treatment for social deficits and biomarkers of response in children with autism

Significance Autism spectrum disorder (ASD) is characterized by social deficits. Emerging evidence suggests that the neuropeptide oxytocin, which regulates mammalian social functioning, may be a promising treatment for ASD. However, prior oxytocin treatment trials in ASD patients have produced equivocal results, perhaps because of variability in patients’ underlying neuropeptide biology. Here we provide evidence that oxytocin treatment improves social abilities in children with ASD and that individuals with the lowest pretreatment blood oxytocin concentrations benefit the most from oxytocin administration. These findings reveal a personalized component to oxytocin treatment which may have important implications for accurately testing oxytocin’s therapeutic potential, both for ASD and for a broad range of developmental and psychiatric disorders in which patients exhibit social impairments. Autism spectrum disorder (ASD) is characterized by core social deficits. Prognosis is poor, in part, because existing medications target only associated ASD features. Emerging evidence suggests that the neuropeptide oxytocin (OXT) may be a blood-based biomarker of social functioning and a possible treatment for ASD. However, prior OXT treatment trials have produced equivocal results, perhaps because of variability in patients’ underlying neuropeptide biology, but this hypothesis has not been tested. Using a double-blind, randomized, placebo-controlled, parallel design, we tested the efficacy and tolerability of 4-wk intranasal OXT treatment (24 International Units, twice daily) in 32 children with ASD, aged 6–12 y. When pretreatment neuropeptide measures were included in the statistical model, OXT compared with placebo treatment significantly enhanced social abilities in children with ASD [as measured by the trial’s primary outcome measure, the Social Responsiveness Scale (SRS)]. Importantly, pretreatment blood OXT concentrations also predicted treatment response, such that individuals with the lowest pretreatment OXT concentrations showed the greatest social improvement. OXT was well tolerated, and its effects were specific to social functioning, with no observed decrease in repetitive behaviors or anxiety. Finally, as with many trials, some placebo-treated participants showed improvement on the SRS. This enhanced social functioning was mirrored by a posttreatment increase in their blood OXT concentrations, suggesting that increased endogenous OXT secretion may underlie this improvement. These findings indicate that OXT treatment enhances social abilities in children with ASD and that individuals with pretreatment OXT signaling deficits may stand to benefit the most from OXT treatment.

Insights into dyssynchrony in Hypoplastic Left Heart Syndrome

BACKGROUND Cardiac resynchronization therapy has been proposed for treatment of hypoplastic left heart syndrome (HLHS) patients with right ventricular (RV) failure. The role of dyssynchrony, however, is poorly understood in this population. OBJECTIVE The purpose of this study was to better understand the relationship between electrical and mechanical dyssynchrony in HLHS using 3-dimensional electrical mapping, tissue Doppler indices of wall motion, and vector velocity imaging. METHODS Eleven HLHS subjects with normal RV function and ten normal subjects (age 3-18 years) were studied. Electrical and mechanical activation times and dyssynchrony indices (electrical dyssynchrony index, mechanical dyssynchrony index) were calculated using 3-dimensional electrical mapping, tissue Doppler indices, and vector velocity imaging. RESULTS No differences in measures of electrical dyssynchrony were seen when comparing HLHS patients and normal patients (electrical activation time 63.3 ± 22.8 ms vs 56.2 ± 11.2 ms, P = .38; electrical dyssynchrony index 13.7 ± 6.3 ms vs 11.6 ± 3.0 ms, P = .34). However, measures of mechanical dyssynchrony were markedly abnormal in HLHS patients despite normal RV function (mechanical activation time 16 ± 11.3 ms vs 0.9±1.9 ms, P = .01; mechanical dyssynchrony index 7.5 ± 5.5 vs 0.4 ± 0.8, P<.01). CONCLUSION Patients with HLHS and preserved RV systolic function have normal electrical activation when compared to patients with normal right and left ventricles. In contrast, these patients demonstrate mechanical dyssynchrony compared to patients with normal right and left ventricles. This finding raises important questions about the indications for cardiac resynchronization therapy in this patient population.

Electrophysiologic therapeutics in heart failure in adult congenital heart disease.

Arrhythmias have long been recognized as a major cause of morbidity and mortality in the adult with congenital heart disease. It is important that the clinician accurately diagnoses these disturbances and is cognizant of the full array of antiarrhythmic agents and devices available to treat these conditions. This review discusses the most common arrhythmias encountered in this population and the therapeutic options available. Specific issues unique to this population are also addressed.

Risk of cardiac disease and observations on lack of potential predictors by clinical history among children presenting for cardiac evaluation of mid-exertional syncope.

OBJECTIVE This study aimed to evaluate the incidence of cardiac disorders among children with mid-exertional syncope evaluated by a paediatric cardiologist, determine how often a diagnosis was not established, and define potential predictors to differentiate cardiac from non-cardiac causes. Study design We carried out a single-centre, retrospective review of children who presented for cardiac evaluation due to a history of exertional syncope between 1999 and 2012. Inclusion criteria included the following: (1) age ⩽18 years; (2) mid-exertional syncope; (3) electrocardiogram, echocardiogram and an exercise stress test, electrophysiology study, or tilt test, with exception of long QT, which did not require additional testing; and (4) evaluation by a paediatric cardiologist. Mid-exertional syncope was defined as loss of consciousness in the midst of active physical activity. Patients with peri-exertional syncope immediately surrounding but not during active physical exertion were excluded. RESULTS A total of 60 patients met the criteria for mid-exertional syncope; 32 (53%) were diagnosed with cardiac syncope and 28 with non-cardiac syncope. A majority of cardiac patients were diagnosed with an electrical myopathy, the most common being Long QT syndrome. In nearly half of the patients, a diagnosis could not be established or syncope was felt to be vasovagal in nature. Neither the type of exertional activity nor the symptoms or lack of symptoms occurring before, immediately preceding, and after the syncopal event differentiated those with or without a cardiac diagnosis. CONCLUSIONS Children with mid-exertional syncope are at risk for cardiac disease and warrant evaluation. Reported symptoms may not differentiate benign causes from life-threatening disease.

A Pilot Study Assessing ECG versus ECHO Ventriculoventricular Optimization in Pediatric Resynchronization Patients.

Cardiac resynchronization therapy indications and management are well described in adults. Echocardiography (ECHO) has been used to optimize mechanical synchrony in these patients; however, there are issues with reproducibility and time intensity. Pediatric patients add challenges, with diverse substrates and limited capacity for cooperation. Electrocardiographic (ECG) methods to assess electrical synchrony are expeditious but have not been extensively studied in children. We sought to compare ECHO and ECG CRT optimization in children.

Are wide complex tachycardia algorithms applicable in children and patients with congenital heart disease

INTRODUCTION Several algorithms have been developed to help determine the etiology of wide complex tachycardias (WCTs) in adults. Sensitivity and specificity for differentiating supraventricular tachycardia (SVT) with aberration from ventricular tachycardia (VT) in adults have been demonstrated to be as high as 98% and 97%. These algorithms have not been tested in the pediatric population. We hypothesize that these algorithms have lower diagnostic accuracy in children and patients with congenital heart disease. METHODS A retrospective review of the pediatric electrophysiology database at Stanford from 2001 to 2008 was performed. All children with WCT, a 12-lead electrocardiogram (ECG) available for review, and an electrophysiology study confirming the etiology of the rhythm were included. Patients with a paced rhythm were excluded. The ECGs were analyzed by 2 electrophysiologists blinded to the diagnosis according to the algorithms described in Brugada et al,(2) and Vereckei et al.(5) Additional ECG findings were recorded by each electrophysiologist. RESULTS A total of 65 WCT ECGs in 58 patients were identified. Supraventricular tachycardia was noted in 62% (40/65) and VT in 38% (25/65) of the ECGs. The mean age was 13.5 years (SD ± 5.1), the mean weight was 51.8 kg (SD ± 22.4), and 48% (31/65) were male. The mean tachycardia cycle length was 340 milliseconds (SD ± 95). Congenital heart disease (CHD) was present in 37% (24/65) of patients (7 tetralogy of Fallot, 6 Ebsteins, 4 double-outlet right ventricle, 3 complex CHD, 2 d-transposition of great arteries, 1 status-post orthotopic heart transplantation, 1 ventricular septal defect). The Brugada algorithm correctly predicted the diagnosis 69% (45/65) of the time, the Vereckei algorithm correctly predicted the diagnosis 66% (43/65) of the time, and the blinded reviewer correctly predicted the diagnosis 78% (51/65) of the time. There was no difference in the efficacy of the algorithms in patients with CHD vs those with structurally normal hearts. The findings of left superior axis deviation (P < .01) and a notch in the QRS downstroke of V(1) or V(2) (P < .01) were more common in VT than SVT, whereas a positive QRS deflection in V(1) (P = .03) was more commonly present in SVT than VT. CONCLUSION The Brugada and Vereckei algorithms have lower diagnostic accuracy in the pediatric population and in patients with congenital heart disease than in the adult population. Left superior axis deviation and a notch in the QRS downstroke were more commonly associated with VT, whereas a positive QRS deflection in V(1) was more commonly associated with SVT in this population.

Diminished exercise capacity and chronotropic incompetence in pediatric patients with congenital complete heart block and chronic right ventricular pacing

BACKGROUND Chronic right ventricular (RV) pacing has been associated with decreased exercise capacity and left ventricular (LV) function in adults with congenital complete atrioventricular block (CCAVB), but not in children. OBJECTIVE The purpose of this study was to evaluate the exercise capacity and LV function in pediatric patients with CCAVB receiving chronic RV pacing. METHODS We prospectively evaluated pediatric patients with isolated CCAVB receiving atrial synchronous RV pacing for at least 5 years. Supine bicycle ergometry was performed, and LV ejection fraction (EF) was evaluated by echocardiography. RESULTS Ten CCAVB subjects and 31 controls were matched for age, gender, and body surface area. CCAVB subjects had normal resting EF (63.1% ± 4.0%) and had been paced for 7.9 ± 1.4 years. Exercise testing demonstrated reduced functional capacity in CCAVB patients compared to controls with a lower VO₂peak (26.0 ± 6.6 mL/kg/min vs 39.9 ± 7.0 mL/kg/min, P <.001), anaerobic threshold (15.6 ± 3.9 mL/kg/min vs 18.8 ± 2.7 mL/kg/min, P = .007), and oxygen uptake efficiency slope (1210 ± 406 vs 1841 ± 452, P <.001). Maximum heart rate (165 ± 8 bpm vs 185 ± 9 bpm, P <.001) and systolic blood pressure (159 ± 17 mm Hg vs 185 ± 12 mm Hg, P <.019) also were reduced in CCAVB patients despite maximal effort (respiratory exchange ratio 1.2 ± 0.1). EF was augmented with exercise in controls but not in CCAVB patients (13.2% ± 9.3% vs 0.2% ± 4.8% increase, P <.001). CONCLUSION Clinically asymptomatic children with chronic RV pacing due to CCAVB have significant reductions in functional capacity accompanied by chronotropic incompetence and inability to augment EF with exercise.