INTRODUCTION — Hypertrophic cardiomyopathy (HCM) is one of the most common forms of inherited cardiomyopathy in both adults and children, and it is characterized by hypertrophy of the left ventricle (LV) which sometimes involves the right ventricle. The disease course is highly variable but it is well recognized that there is an increased risk of morbidity and sudden cardiac death (SCD). (See "Sudden cardiac arrest and death in children".)
In broad terms, the symptoms related to HCM can be categorized as those related to heart failure, chest pain, or arrhythmias. Patients with HCM have an increased incidence of both supraventricular and ventricular arrhythmias and are at an increased risk for SCD. Overall, age at death has a bimodal distribution with the highest frequencies in infancy and adolescence, and the poorest survival in patients with inborn errors of metabolism and multiple congenital anomaly syndromes diagnosed before one year of age [1]. HCM is the most common cause of SCD in young, athletic, seemingly healthy individuals, accounting for more than one-third of SCD cases [2]. (See "Hypertrophic cardiomyopathy in adults: Supraventricular tachycardias including atrial fibrillation" and "Hypertrophic cardiomyopathy: Risk stratification for sudden cardiac death".)
Importantly, no medical treatments have been shown to alter disease progression. Management strategies are focused on symptom improvement, with utilization of potentially life-saving therapy in the form of implantable cardioverter defibrillators (ICDs) in patients deemed to be at high risk of SCD.
This topic will provide an overview of the management and prognosis of HCM in children. The clinical manifestations and diagnosis of HCM in children are discussed separately. (See "Hypertrophic cardiomyopathy in children: Clinical manifestations and diagnosis".)
The clinical manifestations, diagnosis, management, and natural history of HCM in adults are discussed separately:
●(See "Hypertrophic cardiomyopathy: Clinical manifestations, diagnosis, and evaluation".)
●(See "Hypertrophic cardiomyopathy: Medical therapy for heart failure".)
●(See "Hypertrophic cardiomyopathy: Risk stratification for sudden cardiac death".)
●(See "Hypertrophic cardiomyopathy: Natural history and prognosis".)
DEFINITIONS — The term HCM is applied broadly to a number of different clinical presentations:
●Sarcomeric HCM – True HCM is a genetically-determined condition attributed to mutations of sarcomeric proteins, and with no other explanation for the left ventricular hypertrophy (LVH). The terms "idiopathic" and "familial" HCM are sometimes used to describe patients who phenotypically have HCM in whom genetic testing is negative or was not performed, in the absence of evidence for a syndrome or systemic disease ("idiopathic HCM") or in the presence of a positive family history ("familial HCM"). The assumption is that such patients are genetically-determined with a yet undiscovered mutation or gene. Clinically, idiopathic and familial HCM follow the path of sarcomeric HCM.
●HCM phenocopies – There are a number of HCM mimickers, or "phenocopies," that present similarly to sarcomeric HCM but that have different pathophysiologies. These include inborn errors of metabolism (IEM), multiple congenital anomaly syndromes (eg, Noonan syndrome), mitochondrial disorders, and neuromuscular disorders (table 1). Phenocopies account for approximately 25 percent of pediatric HCM cases reported in large registry studies [1,3]. The most common phenocopy is Noonan syndrome, with other examples including Danon disease, Friedreich’s ataxia, LEOPARD syndrome, Pompe disease, mitochondrial diseases, and mutation of PRKGA2 [4].
In a series of 855 patients in the Pediatric Cardiomyopathy Registry diagnosed with HCM between 1990 and 2007, the relative frequency of each cause was as follows [1]:
•"Idiopathic" HCM (ie, sarcomeric HCM) – 74 percent
•Multiple congenital anomaly syndromes – 9 percent
•IEM – 9 percent
•Neuromuscular disorders – 7 percent
●Adaptive or secondary LVH – Adaptive changes to stimuli such as athletic training or hypertension can occur in pediatric patients; however, LVH resulting from these adaptations is not considered HCM. In addition, secondary causes of LVH such as pulmonary parenchymal or vascular disease, endocrine disease (eg, maternal diabetes), rheumatic disease, immunological disease, and cardiotoxic exposures are not considered HCM. (See "Hypertrophic cardiomyopathy in children: Clinical manifestations and diagnosis", section on 'Differential diagnosis'.)
There is debate over whether the phenocopies should be included when describing HCM; however, the approach to therapy is often the same. In this topic review, sarcomeric HCM and phenocopies are considered together under the broad term "HCM," unless otherwise specified.
MANAGEMENT
Overview — Management varies considerably depending upon the age of the patient, the degree of heart failure symptoms, whether there is left ventricular outflow tract (LVOT) obstruction, and/or other important findings such as arrhythmic syncope, documented ventricular tachyarrhythmias, and/or prior sudden cardiac arrest. Patients with a diagnosis of HCM but without LVOT obstruction or evidence for arrhythmia warrant regular follow-up, but medical therapy is generally not necessary. With few exceptions, children with HCM should be managed by or in close collaboration with a pediatric cardiologist/electrophysiologist with expertise in this area.
Treatment goals — The goals of management in patients with HCM are to reduce symptoms, reduce the LVOT gradient, preserve LV function, and prolong survival [5]. Importantly, medical treatments have not been shown to alter disease progression. Management strategies are focused on symptom improvement, with utilization of potentially life-saving therapy in the form of implantable cardioverter defibrillators (ICDs) in patients deemed to be at high risk of sudden cardiac death (SCD).
General principles of medical therapy — General principles of medical management of HCM include the following:
●Pharmacologic therapy – Medications used to treat HCM are aimed at reducing LVOT obstruction, decreasing myocardial oxygen demand, and slowing the heart rate to improve ventricular filling (ie, keeping the heart "slow and full" in an effort to reduce the effective LVOT gradient). Beta blockers are the most commonly used agents in children. (See 'Pharmacologic therapy' below and "Hypertrophic cardiomyopathy: Medical therapy for heart failure", section on 'Mechanisms of action'.)
●Avoidance of volume depletion – In patients with HCM, volume depletion tends to decrease stroke volume and worsen the LVOT gradient (or induce an LVOT gradient if no gradient is present during euvolemia). Worsening of the LVOT gradient, particularly when volume depleted, can lead to hypotension, lightheadedness, and syncope.
●Avoidance of medications that may increase the LVOT gradient – Medications that can increase the LVOT gradient should be avoided, including:
•Vasodilators – Vasodilators, such as angiotensin converting enzyme inhibitors, angiotensin II receptor blockers, dihydropyridine calcium channel blockers (eg, nifedipine, amlodipine), and nitroglycerin can produce a fall in peripheral resistance with an increase in LVOT obstruction and filling pressures, thereby resulting in hypotension and/or worsening heart failure (HF) symptoms [5].
•Diuretics – By reducing preload, diuretics can result in less LV filling, a smaller LV chamber, and therefore greater outflow obstruction. However, cautious use of diuretics may be attempted only in non-obstructed HCM patients with persistent HF and evidence of volume overload.
•Digoxin – Digoxin is generally avoided in HCM given that the function is hyperdynamic at baseline. One exception is in patients with systolic dysfunction, as seen in "burned-out" HCM. In this case, standard heart failure therapies may be indicated despite the recommendation to avoid them in patients with HCM and preserved LV systolic function. (See "Heart failure in children: Management", section on 'Digoxin'.)
Pharmacologic therapy — Negative inotropic agents (most commonly beta blockers; less commonly, non-dihydropyridine calcium channel blockers [eg, verapamil] and disopyramide) are the most widely used initial therapies in children (algorithm 1). There have been no large randomized trials of pharmacologic therapies in HCM. As a result, treatment strategies are based upon observational data and clinical experience [6]. An empiric approach is usually required, since it is not possible to predict which drug will work best for a given patient (algorithm 1).
Patient selection — There are varied approaches regarding when to initiate treatment for children with HCM, and practice varies considerably, particularly for asymptomatic patients.
●There is general consensus that symptomatic patients should receive pharmacologic therapy. However, LVOT obstruction resulting in symptoms with exertion is uncommon in children with HCM, often despite a high LVOT gradient. In addition, determining symptoms in younger patients may be difficult, as is determining the presence of a provocable LVOT gradient.
●The approach to treating asymptomatic patients is significantly more variable, with limited data in children to guide the decision to initiate pharmacologic therapy or the choice of a particular therapy. Some experts initiate pharmacologic therapy (usually with a beta blocker) in asymptomatic children whose LVOT gradient is moderate or higher (typically >50 mmHg at rest). Other experts prefer to avoid pharmacologic therapy (regardless of the LVOT gradient) in asymptomatic children, particularly if a reliable assessment of symptoms can be obtained.
First-line agents — In our practice, we typically use beta blockers as a first-line therapy. The preference for beta blockers over other agents is based on the ease of dosing, greater experience and comfort with these agents, and the limitations of verapamil use in infants (verapamil is generally avoided in infants <12 months due to concerns for apnea, hypotension, and cardiac arrest). Many experts favor beta blockers over verapamil (particularly in combination with disopyramide) in patients with evidence of LVOT obstruction, due to the potential risks associated with the vasodilatory effects of non-dihydropyridine calcium channel blockers and disopyramide [7-10].
In a retrospective cohort study, high-dose beta blocker therapy was the only treatment found to be associated with improved survival in childhood HCM [11].
Second-line agents — For patients who are intolerant of beta blockers due to side effects, we typically attempt second-line monotherapy with a non-dihydropyridine calcium channel blocker (usually verapamil) or disopyramide. Verapamil is generally avoided in infants <12 months due to concerns for apnea, hypotension, and cardiac arrest.
Combination therapy — For patients who have significant symptoms and LVOT obstruction despite monotherapy, we proceed with combination therapy. Options for combination therapy include:
●Beta blocker plus non-dihydropyridine calcium channel blocker (usually verapamil)
●Beta blocker plus disopyramide
●Non-dihydropyridine calcium channel blocker (usually verapamil) plus disopyramide
Beta blocker in combination with verapamil is our preferred combination therapy. However, this approach is frequently limited by symptomatic bradycardia, particularly in younger patients who are more dependent on calcium and less tolerant of bradycardia. Patients should be monitored for adverse effects, including bradycardia, hypotension, fatigue, decreased appetite, and feeding intolerance. Combinations using disopyramide are not commonly encountered in pediatric patients, and data are limited, but its use may be applicable in the older adolescent as a third-line option in patients unable to tolerate the combination of beta blocker plus nondihydropyridine calcium channel blocker. There is generally no role for using three drugs (eg, beta blockers, verapamil, and disopyramide) simultaneously.
Persistent heart failure symptoms — Some patients have persistent heart failure symptoms (eg, dyspnea, fatigue, poor feeding, poor growth) despite maximal therapy with negative inotropes (ie, beta blockers, non-dihydropyridine calcium channel blockers, and disopyramide) [12]. Therapeutic options in such patients include:
●Cautious use of diuretics – Diuretics are relatively contraindicated in most patients with HCM due to the potential reduction in preload, which may exacerbate LVOT obstruction, resulting in worsening symptoms and hypotension. However, in patients without LVOT obstruction who have refractory heart failure symptoms and are volume overloaded, diuretics may be used cautiously and are often effective in low doses transiently or on an as-needed basis [8]. (See "Heart failure in children: Management", section on 'Diuretics'.)
●Nonpharmacologic therapies – For patients with refractory symptoms and/or persistent severe LVOT obstruction (ie, LVOT gradient ≥50 mmHg) who are not adequately managed with maximal medical therapy, nonpharmacologic therapies aimed at relieving the LVOT obstruction may be considered, including:
•Surgical myectomy – If pharmacotherapy is ineffective or not tolerated, and limiting heart failure symptoms persist in the setting of LVOT obstruction, surgical myectomy can be highly effective. In a study of 127 pediatric and young adult patients with HCM and LVOT obstruction who underwent transaortic septal myectomy, the procedure was found to be safe and effective, with a reduction in mean LVOT gradient from 89 to 6 mmHg [13]. Overall survival was >90 percent at 20 years, with a total of six patients undergoing repeat septal myectomy for recurrent symptoms. Despite this overall safety and effectiveness, it should be noted that myectomy in younger children is complicated by higher prevalence of inadequate relief of LVOT obstruction. Of the patients who needed re-operation for persistent LVOT obstruction, all were under the age of 14 at initial surgery. In patients with LV obstruction due to Noonan syndrome, a small study including 12 patients undergoing surgical myectomy demonstrated similar results to those undergoing myectomy for nonsyndromic HCM [14]. (See "Hypertrophic cardiomyopathy: Nonpharmacologic treatment of left ventricular outflow tract obstruction", section on 'Surgical septal myectomy'.)
•Alcohol septal ablation – Alcohol septal ablation is rarely performed in pediatric patients. A number of uncertainties regarding the long-term effects of the procedure (ventricular arrhythmia, LV impairment) limit its use in children and adolescents [11,15-17]. Given the numerous concerns, alcohol septal ablation is not recommended in pediatric patients who should, instead, be referred to a surgical center. (See "Hypertrophic cardiomyopathy: Nonpharmacologic treatment of left ventricular outflow tract obstruction", section on 'Alcohol (ethanol) septal ablation'.)
●Heart transplantation – Referral for heart transplant evaluation is appropriate in patients with "burnt out HCM" (ie, progressive disease manifested by reduced systolic function). In other cases, patients may develop symptomatic heart failure from diastolic dysfunction despite normal systolic function. Pediatric heart transplantation is discussed separately. (See "Heart failure in children: Management", section on 'Heart transplantation'.)
Arrhythmia treatment and prevention of sudden cardiac death — The implantable cardioverter-defibrillator (ICD) is the best available therapy for patients with HCM who have survived sudden cardiac death (SCD) or who are at high risk of ventricular arrhythmias and SCD. Because of an increased risk of lead fracture with continued linear growth in pre-adolescent pediatric patients, ICD placement is usually reserved for adolescent patients near adult size unless placed for secondary prevention or if there are other factors that place the child at very high risk of SCD. Antiarrhythmic drug therapy may be appropriate for children with frequent ventricular tachycardia who are not candidates for ICD therapy or who have repeat appropriate device shocks for VT/VF. However, antiarrhythmic medications should not be used alone in lieu of ICD placement in a patients considered to be at high risk for SCD.
ICD therapy — The general principles of ICD use and efficacy in children are similar in many respects to those in adults. However, there are some unique considerations in pediatric patients, including the longevity of the device and lead, the size of the patient relative to the device, and the increased physical activity, particularly in young children. In addition, many children with ICDs outlive their devices and leads, necessitating complex extraction and multiple replacement procedures. These issues need to be carefully considered when evaluating therapeutic options in children with HCM. The risks and benefits of each approach differ by age, size, and whether the patient has symptoms or other risk factors for SCD. (See "Implantable cardioverter-defibrillators: Overview of indications, components, and functions".)
Risk factors for sudden cardiac death — The reported incidence of life-threatening arrhythmia or SCD in pediatric patients with HCM ranges from <1 to 2.8 percent at one year after diagnosis and 9 percent at five years after diagnosis [18]. While these rates are relatively low, the effects on individual patients are devastating, and entire communities can be impacted [19-21].
●Risk prediction in adults – Risk factors for SCD in adults with HCM have been established (table 2), although they continue to evolve and different guidelines use different approaches to risk stratification. Risk stratification in adult patients is discussed in detail separately. (See "Hypertrophic cardiomyopathy: Risk stratification for sudden cardiac death".)
●Risk prediction in pediatric patients – Data on risk factors for SCD in pediatric patients with HCM are less robust. Based on the available data, risk factors identified in adult patients (table 2) appear to have generally similar predictive value in pediatric patients [22]. However, there may be no "one size fits all" approach to risk stratification that can be universally applied to all pediatric patients, given the considerable variation in size and level of maturation among pediatric patients with HCM.
In a cohort of 146 patients <20 years old with HCM, 60 patients were implanted with primary prevention ICDs based on one or more major risk factors derived from ACC/AHA enhanced guidelines (table 2), with mean follow up of 5.8 years [22]. A total of 10 patients (9 patients with an ICD and 1 high-risk patient who declined primary prevention ICD) experienced ventricular tachyarrhythmias requiring intervention. The sensitivity of the enhanced ACC/AHA guidelines for predicting ventricular tachyarrhythmias was 100 percent and exceeded that of other published risk scores and the European Society for Cardiology risk calculator.
Massive left ventricular hypertrophy (LVH) is an important risk factor for SCD in pediatric patients with HCM. In the cohort study described above, massive LVH was the most common risk factor prompting ICD placement, occurring in 70 percent of patients treated with ICDs [22]. In children, LVH is often defined using a z-score rather than an absolute cut-off. In a study of 128 children <19 years old with HCM, septal thickness >190 percent above the 95th percentile for age (which roughly corresponds to a z-score >10) was an independent predictor of SCD, with a sensitivity of 91 percent and a specificity of 61 percent [23]. In another report of 96 pediatric patients (mean age 10.6 years), LVH wall thickness z-score >6 and blunted blood pressure response to exercise were associated with increased risk of death or cardiac transplantation; however, this included both SCD (n = 3) and non-SCD (n = 3) [24].
Research on developing risk prediction models for SCD in children with HCM is ongoing. One such model, dubbed HCM Risk-Kids, was developed from a cohort of 1024 children aged ≤16 years with HCM; Variables included in the HCM Risk-Kids model include unexplained syncope, maximal LV wall thickness, left atrial diameter, LVOT gradient, and nonsustained VT. The model generates an individualized risk score (similar to the HCM Risk-SCD score in adults) and was shown to have moderate discrimination for predicting SCD (C-statistic 0.69) [25]. Another model, developed using 572 patients from the Precision Medicine for Cardiomyopathy (PRIMaCY) international registry of pediatric HCM, includes the variables of age at diagnosis, nonsustained VT, unexplained syncope, septal and posterior wall thickness z-scores, left atrial diameter z-score, LVOT gradient, and presence of a pathogenic variant [18]. The PRIMaCY model also showed moderate discrimination for predicting SCD events (C-statistic 0.75). Of note, family history was not associated with SCD, and in contrast to most other studies there was an inverse association between LVOT gradient and SCD once the gradient was >100 mmHg. Only the PRIMaCY model has been validated in an independent cohort, consisting of 285 phenotype positive patients from the Sarcomeric Human Cardiomyopathy Registry (ShaRe). Neither model has been prospectively validated. The PRIMaCY risk calculator is not yet available for public use.
Our approach to ICD placement in children — The approach to ICD implantation is different for older adolescent patients who are nearing adult size, compared with younger adolescents or pre-adolescent children.
●Older adolescent patients nearing adult size — Application of adult guidelines for ICD implantation is generally the approach in the older adolescent (ie, ≥16 years), and the HCM SCD risk calculator based on European Society of Cardiology guidelines is valid for patients 16 years and older [26]. These guidelines are not intended for use in patients younger than 16 years old. Traditional risk factors of septal dimension >3 cm, family history of SCD, personal history of nonsustained ventricular tachycardia, personal history of unexplained syncope, or lack of appropriate blood pressure response during exercise stress, as well as the newer risk factor of late gadolinium enhancement burden, generally can be applied to older adolescent patients. (See "Hypertrophic cardiomyopathy: Management of ventricular arrhythmias and sudden cardiac death risk", section on 'Implantable cardioverter-defibrillators (ICDs)'.)
Specifically:
•For pediatric patients who survive an episode of sustained VT or sudden cardiac arrest, we implant an ICD for the secondary prevention of SCD.
•Older adolescent patients with HCM and ≥2 of the major noninvasive risk markers (table 2) are at higher risk of SCD and may benefit from ICD implantation for primary prevention of SCD.
•In addition, an ICD may also be reasonable in older adolescent patients with one of the major risk markers, particularly in patients with a family history of SCD due to HCM, massive LVH (ie, ≥30 mm), history of nonsustained ventricular tachycardia on ambulatory monitoring, or recent unexplained syncope.
•Unlike recent adult considerations for end-stage HCM (ie, LVEF <50 percent), there are insufficient data to support or refute placement of ICD in similarly affected adolescent patients [27].
●Younger adolescent and pre-adolescent children — The risk-to-benefit profile for ICD placement in younger and/or smaller patients is less favorable as compared with adolescents and adults. Smaller children have limited space options for ICD generator placement and are at considerably higher risk for ICD lead fracture with continued linear growth and related inappropriate ICD discharges [28]. For these reasons, ICD placement in pre-adolescent patients is generally reserved patients who survive an episode of sustained VT or sudden cardiac arrest (ie, secondary prevention) and patients deemed to be at very high risk of SCD. These decisions are individualized, taking into account the age and size of the patient, family history, septal thickness, history of syncope, and other risk factors. Risk stratification schemas that are used in adult patients generally do not apply to small children. In particular, rather than an absolute value for septal thickness, some experts use septal dimension z-score >5 as a cut-off for consideration of ICD placement [23,24]. However, other experts prefer to rely on absolute septal thickness and offer ICD placement for values close to or greater than 30 mm. Efforts to develop risk calculators for pediatric patients are ongoing, and these tools may prove to be clinically useful in the future. (See "Implantable cardioverter-defibrillators: Overview of indications, components, and functions".)
Benefits and risks of ICDs in children — Limited data suggest that pediatric patients with high-risk HCM (as assessed by traditional adult risk factors (table 2)) benefit from implantation of an ICD. However, the available studies included mostly adolescent and young adult patients, and these findings may not apply to young children. Furthermore, with approximately 5 to 15 percent of patients with ICD placed in the pediatric age range experiencing an appropriate shock on long-term follow-up, improved understanding of which patients are high risk may limit unnecessary procedures in patients unlikely to need this particular therapy [18,27].
In a multicenter, international registry study of 224 pediatric patients (mean age 14.5 years) who underwent ICD implantation at the discretion of the managing pediatric cardiologists/electrophysiologists, relying largely on the risk stratification model established for the prevention of SCD in adult patients with HCM, ICD interventions terminating life-threatening arrhythmias occurred at a rate of 4.5 percent per year (14 percent per year for secondary prevention after cardiac arrest, and 3 percent per year for primary prevention) [29]. Similar to adult studies, there was no significant difference in the likelihood of receiving an appropriate ICD discharge whether the patient had 1, 2, or ≥3 risk factors.
In another study of 474 consecutive patients aged 7 to 29 years (mean 20 years) managed at two large referral centers, ICDs were implanted in 231 patients (49 percent) according to SCD risk stratification using conventional markers [21]. Over a median follow-up of six years, ventricular tachyarrhythmias were successfully aborted by appropriate defibrillator interventions in 31 patents (13 percent). Device-related complications occurred in 60 patients (26 percent) at a rate of 1.8 percent per year. The most common complication was inappropriate shock, which occurred in 42 patients (18 percent) and was equally common in patients with ICDs placed for primary versus secondary prevention. Notably, of the 42 patients experiencing inappropriate shocks, 13 (31 percent) also had appropriate device interventions. Other complications included lead fracture, dislodgements, or insulation defect without inappropriate shock (n = 11); hematoma/thrombosis (n = 2); pocket revision (n = 2); infection (n = 1); generator malfunction or replacement because of manufacturer's advisory or recall (n = 1); perforation of right atrium during lead extraction (n = 1). The use of subcutaneous ICD systems that do not require transvenous lead placement has been reported in pediatric patients and may represent an alternative in certain cases; however, long-term efficacy and safety are not yet well demonstrated in this patient population [30].
Therapies other than ICD implantation — Use of antiarrhythmic agents or tachyarrhythmia ablation may be considered as adjunctive therapies in appropriate patients who have either frequent VT and are not candidates for ICD or who experience repeat appropriate ICD shocks. Some patients have benefited from antitachycardia pacing, accessory pathway ablation, and atrial flutter ablation, though published reports in pediatric patients are lacking.
FOLLOW-UP — We suggest that pediatric patients with phenotypic disease, particularly those on medication, should have a clinical evaluation every 6 to 12 months, with electrocardiogram (ECG) and echocardiogram at least annually. Additional testing such as ambulatory ECG monitoring, exercise testing, and cardiovascular magnetic resonance (CMR) are variable based on the specific patient. For those who are genotype-positive/phenotype-negative, evaluation including ECG and echocardiogram is recommended annually, particularly during the adolescent years when patients most commonly develop symptoms. Current adult guidelines recommend clinical assessment and testing, including ECG and echocardiogram, every one to two years or as indicated by symptoms [31,32].
LONG-TERM HEALTH MAINTENANCE — Important aspects of long-term health care maintenance in children with HCM include:
Immunizations — Children with HCM should receive all routine childhood vaccinations, including pneumococcal and yearly influenza vaccine. In addition, respiratory syncytial virus (RSV) immunoprophylaxis should be provided to eligible infants (table 3). (See "Seasonal influenza in children: Prevention with vaccines" and "Respiratory syncytial virus infection: Prevention in infants and children".)
Monitoring of growth parameters — It is important to monitor growth and development in children with HCM as it is in all children. Failure to thrive may be the main clinical sign of heart failure in infants and children. (See "Normal growth patterns in infants and prepubertal children".)
Monitoring for cardiac symptoms — Between visits with the cardiac specialist, the primary care provider should monitor for symptoms related to left ventricular outflow tract (LVOT) obstruction or heart failure. If the patient develops new or worsening symptoms of chest pain, presyncope/syncope, palpitations, or heart failure symptoms (eg, poor feeding, failure to thrive, tachypnea, easy fatigability), the patient should be promptly referred to the specialist for cardiac evaluation.
Antibiotic prophylaxis — Routine antibiotic prophylaxis for the prevention of bacterial endocarditis is not necessary for most children with HCM unless there are other factors that place the child at high risk [33]. Risk factors for bacterial endocarditis are reviewed in detail separately. (See "Prevention of endocarditis: Antibiotic prophylaxis and other measures".)
Exercise and sports participation — Due to the potential risk of sudden cardiac death (SCD) associated with exercise in patients with HCM, consideration of appropriate restriction of activity is an important component of patient management. Consensus guidelines recommend that athletes with a probable or unequivocal clinical diagnosis of HCM should not participate in most competitive sports, with the possible exception of low intensity sports (figure 1) [34]. Because these and similar guidelines are perceived to be quite restrictive and often not adhered to by patients and clinicians, the appropriate role and safety of exercise in genetic cardiovascular conditions such as HCM is currently being investigated [35,36].
Activity restriction in patients with HCM is discussed in greater detail separately. (See "Athletes: Overview of sudden cardiac death risk and sport participation", section on 'Hypertrophic cardiomyopathy'.)
Planning of noncardiac surgery — Children with HCM who have a significant left ventricular outflow tract (LVOT) gradient are at increased risk for adverse events (eg, acute LVOT obstruction and hemodynamic collapse) when undergoing surgery and other procedures under anesthesia. Careful perioperative planning (including consultation with cardiac anesthesia, coordination with the cardiologist, and appropriate postprocedural monitoring) are important for pediatric patients with obstructive HCM undergoing surgery or other procedures requiring anesthesia/sedation. Management of acute LVOT obstruction, as well as perioperative planning and management, are discussed separately. (See "Hypertrophic cardiomyopathy: Medical management for non-heart failure symptoms", section on 'Acute hemodynamic collapse in the setting of LVOT obstruction' and "Anesthesia for patients with hypertrophic cardiomyopathy undergoing noncardiac surgery".)
PROGNOSIS — The prognosis for children with HCM depends on the age and degree of symptoms at diagnosis and the presence of associated conditions.
●Older children and adolescents with sarcomeric HCM – In older children and adolescents with sarcomeric HCM, who typically have no or minor symptoms at the time of diagnosis, outcomes are generally very good. With contemporary management strategies that employ appropriate medical therapy and use of ICD in patients identified as high risk, low mortality can be achieved in these patients. In a study of 474 consecutive patients between the ages of 7 and 29 years at two referral institutions, five-year survival was >95 percent, with a similar proportion experiencing no or mild symptoms [21]. When mortality does occur in older children and adolescents with HCM, it is often due to arrhythmic SCD, which is frequently unheralded by symptoms. These outcomes may be different for patients who present as symptomatic at diagnosis. In a report of 100 Italian children diagnosed with HCM (mean age 12.2 years at diagnosis), of whom 42 percent were symptomatic at diagnosis, prevalence of adverse disease-related events, including SCD, were substantially higher than that reported in other studies [37]. Over an average follow-up of 9.2 years, nearly one-quarter of the patients in this cohort experienced cardiac events, including SCD (19 percent), heart failure-related death (3 percent), and heart transplantation (2 percent). Whether these data are applicable to other diverse, heterogenous pediatric HCM patient populations is uncertain. (See "Hypertrophic cardiomyopathy: Risk stratification for sudden cardiac death".)
●HCM in infants and patients with IEM and congenital syndromes – The prognosis is less favorable in patients diagnosed with HCM in infancy and patients with inborn errors of metabolism (IEM) and multiple congenital anomaly (MCA) syndromes (table 1). In these patients, mortality is most commonly due to heart failure and other non-SCD causes [1,38-40].
•In a series of 855 patients from the Pediatric Cardiomyopathy Registry, over a median follow-up of 2.1 years, 96 patients (11 percent) died, 18 patients (2 percent) underwent cardiac transplantation, and 11 patients (1 percent) developed dilated cardiomyopathy [1]. The age of death had a bimodal distribution, with a large peak in infancy and a smaller peak in adolescence. The mode of death, when known, was sudden in only 44 percent of deaths that occurred among patients diagnosed infancy; whereas all of the deaths that occurred in older children were sudden deaths. The risk of adverse outcome was increased among patients with infantile HCM (two-year transplant-free survival 70 percent compared with 92 to 98 percent for those diagnosed later) and among patients with IEM and MCA syndromes (one-year survival rates of 54 and 82, respectively) [1].
•Similar findings were noted in another analysis of the Pediatric Cardiomyopathy Registry data aimed at risk stratification at the time of diagnosis [38]. The risk of death or heart transplantation was increased in patients diagnosed before age one year, those with IEM or MCA syndromes, and those with hypertrophic cardiomyopathy in combination with other cardiomyopathy phenotypes (ie, restrictive or dilated cardiomyopathy). Children with HCM associated with IEM or MCA syndromes who presented in infancy had a particularly poor prognosis, with five-year survival rates of 26 and 66 percent, respectively. Additional independent predictors of death or heart transplantation included congestive heart failure symptoms at the time of diagnosis and low weight and body mass index for age.
•Among a United Kingdom cohort of 687 children diagnosed with HCM between 1980 and 2017 (63 percent male; median age at diagnosis 5.2 years, with 23 percent diagnosed before age 1 year), freedom from death or transplantation at five years post-diagnosis was 91 percent for the entire cohort, a finding which remained consistent across different eras [40]. Children diagnosed during infancy, or with associated IEM, had worse five-year survival (81 and 66 percent, respectively).
Outcomes for HCM are better than those for other cardiomyopathies, although presence of restrictive physiology portends a poorer outcome than for HCM alone [41].
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Cardiomyopathy".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topic (see "Patient education: Hypertrophic cardiomyopathy in adults (The Basics)" and "Patient education: Hypertrophic cardiomyopathy in children (The Basics)")
●Beyond the Basics topic (see "Patient education: Hypertrophic cardiomyopathy (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Management of children with hypertrophic cardiomyopathy (HCM) varies considerably depending upon the age of the patient, the degree of heart failure symptoms, whether there is left ventricular outflow tract (LVOT) obstruction, and/or other important findings such as arrhythmic syncope, documented ventricular tachyarrhythmias, and/or prior sudden cardiac arrest. The goals of management in patients with HCM are to reduce symptoms, reduce the LVOT gradient, preserve LV function, and prolong survival. (See 'Management' above.)
●There is no standardized approach regarding when to initiate treatment for children with HCM, and practice varies considerably. In our practice, we treat all symptomatic patients, and we treat asymptomatic patients whose LVOT gradient is greater than mild (ie, >25 mmHg at rest). (See 'Pharmacologic therapy' above.)
•We typically use beta blockers as a first-line therapy. The preference for beta blockers over other agents is based on the ease of dosing, greater experience and comfort with these agents, and the limitations of verapamil use in infants (verapamil is generally avoided in infants <12 months due to concerns for apnea, hypotension, and cardiac arrest). (See 'First-line agents' above.)
•For patients who are intolerant of beta blockers due to side effects, we typically attempt second-line monotherapy with a nondihydropyridine calcium channel blocker (usually verapamil). (See 'Second-line agents' above.)
•For patients who have significant symptoms and LVOT obstruction despite monotherapy, we proceed with combination therapy. Beta blocker in combination with verapamil is our preferred combination therapy. (See 'Combination therapy' above.)
•Some patients have persistent heart failure symptoms despite maximal medical therapy. Therapeutic options in such patients include cautious use of diuretics, nonpharmacologic therapies aimed at reducing LVOT gradient (eg, surgical myectomy), or heart transplantation for "burnt out HCM" or patients with refractory symptoms despite septal reduction therapy. (See 'Persistent heart failure symptoms' above.)
●The implantable cardioverter-defibrillator (ICD) is the best available therapy for patients with HCM who have survived sudden cardiac death (SCD) or who are at high risk of ventricular arrhythmias and SCD. In pediatric patients, ICD placement is usually reserved for patients near adult size unless placed for secondary prevention or if there are other factors that place the child at very high risk of SCD. Use of antiarrhythmic agents or tachyarrhythmia ablation may be considered in appropriate patients who have either frequent ventricular tachycardia (VT) or repeat ICD shocks. (See 'Arrhythmia treatment and prevention of sudden cardiac death' above.)
●We suggest that pediatric patients with phenotypic disease, particularly those on medication, should have a clinical evaluation every 6 to 12 months, with ECG and echocardiogram at least annually. For those who are genotype-positive/phenotype-negative, evaluation including ECG and echocardiogram is recommended annually, particularly during the adolescent years when patients most commonly develop symptoms. (See 'Follow-up' above.)
●Important aspects of long-term health care maintenance in children with HCM include administering routine childhood vaccinations, monitoring growth parameters, monitoring for cardiac symptoms, providing guidance regarding exercise and sports participation, and planning of non-cardiac surgery. Antibiotic prophylaxis for bacterial endocarditis is generally not necessary for children with HCM. (See 'Long-term health maintenance' above.)
●The prognosis for children with HCM depends on the age and degree of symptoms at diagnosis and the presence of associated conditions. In older children and adolescents with sarcomeric HCM, who typically have no or minor symptoms at the time of diagnosis, outcomes are generally very good. By contrast, the prognosis is less favorable in patients diagnosed with HCM in infancy and patients with inborn errors of metabolism (IEM) and congenital multiple congenital anomaly syndromes (table 1). (See 'Prognosis' above.)
