Effects of lifestyle changes and high-dose β-blocker therapy on exercise capacity in children, adolescents, and young adults with hypertrophic cardiomyopathy

Development of a Pediatric Cardiology Cardiopulmonary Exercise Testing Database

Cardiopulmonary exercise testing (CPET) provides clinicians with information vital to the management of pediatric cardiology patients. CPET can also be used to measure cardiorespiratory fitness (CRF) in these patients. CRF is a robust marker of overall health in children. However, a complete understanding of CRF in pediatric cardiology patients is limited by lack of large, standardized CPET databases. Our purpose was to develop a standardized CPET database, describe available data at our institution, and discuss challenges and opportunities associated with this project. CPETs performed from 1993 to present in an urban pediatric hospital were collected and compiled into a research database. Historical data included demographic and clinical variables and CPET outcomes, and additional variables were calculated and coded to facilitate analyses in these cohorts. Patient diagnoses were coded to facilitate sub-analyses of specific cohorts. Quality assurance protocols were established to ensure future database contributions and promote inter-institutional collaborations. This database includes 10,319 CPETs (56.1% male), predominantly using the Bruce Protocol. Patients ranging from ages 6 to 18 years comprise 86.8% of available CPETs. Diagnosis classification scheme includes patients with structurally normal hearts (n = 3,454), congenital heart disease (n = 3,614), electrophysiological abnormalities (n = 2,082), heart transplant or cardiomyopathy (n = 833), and other diagnoses (n = 336). Historically, clinicians were provided with suboptimal interpretive resources for CPET, often generalizing inferences from these resources to non-representative clinical populations. This database supports representative CRF comparisons and establishes a framework for future CRF-based registries in pediatric patients referred for CPET, ultimately improving clinical decision-making regarding fitness in these populations.

Cardiorespiratory fitness, muscle fitness, and physical activity in children with long QT syndrome: A prospective controlled study

Background

In children with congenital long QT syndrome (LQTS), the risk of arrhythmic events during exercise commonly makes it difficult to balance exercise restrictions versus promotion of physical activity. Nevertheless, in children with LQTS, cardiorespiratory fitness, muscle fitness, and physical activity, have been scarcely explored.

Materials and methods

In this prospective, controlled, cross-sectional study, 20 children with LQTS (12.7 ± 3.7 years old) and 20 healthy controls (11.9 ± 2.4 years old) were enrolled. All participants underwent a cardiopulmonary exercise test, a muscular architecture ultrasound assessment, (cross-sectional area on right rectus femoris and pennation angle), a handgrip muscular strength evaluation, and a standing long broad jump test. The level of physical activity was determined using with a waist-worn tri-axial accelerometer (Actigraph GT3X).

Results

Peak oxygen uptake (VO_2peak) and ventilatory anaerobic threshold (VAT) were lower in children with LQTS than in healthy controls (33.9 ± 6.2 mL/Kg/min vs. 40.1 ± 6.6 mL/Kg/min, P = 0.010; 23.8 ± 5.1 mL/Kg/min vs. 28.8 ± 5.5 mL/Kg/min, P = 0.007, respectively). Children with LQTS had lower standing long broad jump distance (119.5 ± 33.2 cm vs. 147.3 ± 36.1 cm, P = 0.02) and pennation angle (12.2 ± 2.4° vs. 14.3 ± 2.8°, P = 0.02). No differences in terms of moderate-to-vigorous physical activity were observed (36.9 ± 12.9 min/day vs. 41.5 ± 18.7 min/day, P = 0.66), but nearly all children were below the WHO guidelines.

Conclusion

Despite similar physical activity level, cardiorespiratory fitness and muscle fitness in children with LQTS were lower than in healthy controls. The origin of this limitation seemed to be multifactorial, involving beta-blocker induced chronotropic limitation, physical and muscle deconditioning. Cardiovascular rehabilitation could be of interest in children with LQTS with significant physical limitation.

Current therapies for hypertrophic cardiomyopathy: a systematic review and meta-analysis of the literature

AIMS

The aim of this study was to synthesize the evidence on the effect of the current therapies over the pathophysiological and clinical characteristics of patients with hypertrophic cardiomyopathy (HCM).

METHODS AND RESULTS

A systematic review and meta-analysis of 41 studies identified from 1383 retrieved from PubMed, Web of Science, and Cochrane was conducted. Therapies were grouped in pharmacological, invasive and physical exercise. Pharmacological agents had no effect on functional capacity measured by VO2max (1.11 mL/kg/min; 95% CI: -0.04, 2.25, P < 0.05). Invasive septal reduction therapies increased VO2max (+3.2 mL/kg/min; 95% CI: 1.78, 4.60, P < 0.05). Structured physical exercise programmes did not report contraindications and evidenced the highest increases on functional capacity (VO2max + 4.33 mL/kg/min; 95% CI: 0.20, 8.45, P < 0.05). Patients with left ventricular outflow tract (LVOT) obstruction at rest improved their VO2max to a greater extent compared with those without resting LVOT obstruction (2.82 mL/kg/min; 95% CI: 1.97, 3.67 vs. 1.18; 95% CI: 0.62, 1.74, P < 0.05). Peak LVOT gradient was reduced with the three treatment options with the highest reduction observed for invasive therapies. Left ventricular ejection fraction was reduced in pharmacological and invasive procedures. No effect was observed after physical exercise. Symptomatic status improved with the three options and to a greater extent with invasive procedures.

CONCLUSIONS

Invasive septal reduction therapies increase VO2max, improve symptomatic status, and reduce resting and peak LVOT gradient, thus might be considered in obstructive patients. Physical exercise emerges as a coadjuvant therapy, which is safe and associated with benefits on functional capacity. Pharmacological agents improve reported NYHA class, but not functional capacity.

Physical Activity in Paediatric Long QT Syndrome Patients

Background

Physical activity (PA) is important for cardiovascular health as well as social and emotional well-being of children. Patients with long QT syndrome (LQTS) often face PA restrictions and are often prescribed beta-blockers for disease management. The aim of this study was to determine if PA levels were lower in patients with LQTS compared with healthy controls.

Methods

Participants with LQTS from an inherited arrhythmia clinic completed the Physical Activity Questionnaire for Children and Adolescents (PAQ-C/A) and an exercise stress test. PAQ score (a general measure of PA for youth, unitless) and endurance time were compared with healthy controls.

Results

Twenty-three patients with LQTS completed the PAQ and had an exercise stress test within a year of having completed the PAQ. No difference was observed in PAQ scores between LQTS and control groups (LQTS: 2.3 ± 0.15 vs controls: 2.3 ± 0.18; P = 0.78). There was no effect of age on PA in patients with LQTS (P > 0.05), whereas PA significantly decreased in controls with age (eg, 11-12 vs 17-20 years: 3.2 ± 0.07 vs 1.5 ± 0.08, P = 0.005). Endurance time and heart rate at peak exercise were significantly lower in patients with LQTS compared with controls (11 ± 0.5 vs 15 ± 0.5 minutes, P < 0.0001; 169 ± 5 vs 198 ± 2 beats per minute, P < 0.0001).

Conclusions

Despite guideline recommendations restricting PA, risk of sudden cardiac death, and use of beta-blockers, our cohort of patients with LQTS reported similar PA levels as healthy controls.

[Arrhythmias and Sudden Death Risk in Hypertrophic Cardiomyopathy]

The risk of sudden death in hypertrophic cardiomyopathy is related to the presence of ventricular arrhythmias in most cases. Finding the best schemes to assess the probability of arrhythmic complications will remain a challenge for modern Cardiology. Meanwhile, the multifactorial approach is the best strategy to avoid the unnecessary implantation of devices such as the implantable cardioverter defibrillator. Although the electrocardiogram remains an excellent diagnostic tool, even before echocardiographic expression, it does not have a clear role as a risk factor. However, the identification of associated arrhythmias such as preexcitation or long QT and variants of presentation as apical hypertrophic cardiomyopathy, allows identifying patients with high probability of sudden death. During the last few years, cardiac resonance and quantification of intramyocardial fibrosis (the basic mechanism of ventricular arrhythmias) have gained an important role in the evaluation of these patients.In particular, pediatric patients must have an individualized approach due to the poor prognosis at early ages and the uncertain role of different tools for risk assessment and treatment.

Disopyramide as rescue treatment in a critically ill infant with obstructive hypertrophic cardiomyopathy refractory to beta blockers

Hypertrophic obstructive cardiomyopathy (HOCM) is the most common known cause of sudden death in children beyond infancy and in young athletes. Cases reported indicate that steroid-induced HOCM is usually a benign disorder. The normalization of cardiac morphological changes and clinical signs observed after the discontinuation of steroid therapy indicates that the effects on cardiac muscle are dose-dependent and reversible. However, the management of patients with symptomatic-HOCM presenting in infancy represents a major challenge because left ventricular outflow tract obstruction is a major risk factor associated with increased mortality in pediatric patients. We report a critically ill infant with steroid-induced HOCM resistant to beta-blockers who was successfully treated with disopyramide without relevant adverse events. Adult guidelines and pediatric experts suggest pharmacological therapy with beta-blockers or verapamil as the first- and second-line approach. However, these drugs are not always an option, especially in critical patients, hence, alternative therapeutic options are required. For these cases, disopyramide could be an alternative drug in spite of the little evidence on its safety and efficacy in pediatric patients. Our experience supports this cause, and the need for prospective studies on its use in the management of hypertrophic cardiomyopathy in children. <Learning objective: Patients with symptomatic-HOCM resistant to first-line therapy with beta-blockers represent a challenge and are often referred for advanced care. In children, many authors suggest that disopyramide in combination with beta-blockers could be a useful adjunct therapy option in these cases, resulting in decrease of left ventricular outflow tract obstruction, symptoms, and survival improvement, without significant pro-arrhythmia mortality.>.

Beta-Blockers in Pediatric Hypertrophic Cardiomyopathies

Congestive cardiac failure accounts for 36% of childhood deaths in hypertrophic cardiomyopathy, and in infants with heart failure symptoms before two years of age, the mortality is extremely high unless treatment with beta-receptor antagonists is instituted. The mechanism of heart failure is not systolic dysfunction, but rather extreme diastolic dysfunction leading to high filling pressures.

Risk factors for development of heart failure are a generalized pattern of hypertrophy with a left ventricular posterior wall-to-cavity ratio >0.30, the presence of left ventricular outflow tract obstruction at rest, and the co-existence of syndromes in the Noonan/Leopard/Costello spectrum. The 5-year survival of high-risk patients is improved from 54% to 93% by high-dose beta-blocker therapy (>4.5 mg/kg/day propranolol). The mechanism of the beneficial effect of beta-blockers is to improve diastolic function by lengthening of diastole, reducing outflow-obstruction, and inducing a beneficial remodelling resulting in a larger left ventricular cavity, and improved stroke volume. Hypertrophic cardiomyopathy is associated with increased activity of cardiac sympathetic nerves, and infants in heart failure with hypertrophic cardiomyopathy show signs of extreme sympathetic over-activity, and require exceptionally high doses of beta-blockers to achieve effective beta-blockade as judged by 24 h Holter recordings, often 8-24 mg/kg/day of propranolol or equivalent.

Conclusion: Beta-blocker therapy is without doubt the treatment of choice for patients with heart failure caused by hypertrophic cardiomyopathy, but the dose needs to carefully titrated on an individual basis for maximum benefit, and the dose required is surprisingly large in infants with heart failure due to hypertrophic cardiomyopathy.