Clinical Case Presentation…
A previously healthy 7-week old (4 kg) male is referred by his pediatrician to the regional children’s hospital 15 miles from his home town with a 2-day history of poor feeding and diaphoresis. He presented with tachycardia, tachypnea with labored breathing and rales upon auscultation. Vital signs include a heart rate of 166 bpm, a respiratory rate of 72 bpm, a room air oxygen saturation of 90% and a blood pressure of 81/56 (64). Due to the infant’s severe respiratory distress and marginal oxygen saturation, he was electively intubated. A 12-lead EKG revealed a sinus tachycardia with what appeared to be signs of left atrial enlargement and a left axis deviation. Laboratory studies included the following:
The Problem
Shortly following stabilization of this infant, a pediatric cardiology consult was requested. Based upon the clinical presentation, 12 lead EKG and laboratory studies (relatively benign with the exception of the compensated respiratory acidosis that appears to be chronic in nature), the emergency physician was concerned with what appeared to be congestive heart failure. But what was causing this in a 7-week old?
The Pediatric Cardiologist performed an echocardiogram which showed an increase in left ventricular wall thickness and asymmetrical septal hypertrophy. This was consistent with hypertrophic cardiomyopathy (HCM). The infant was moved to the intensive care unit (ICU) and arrangements were made to transfer him to a children’s hospital with interventional cardiology and cardiac surgery capabilities beyond what this hospital could currently provide. He was started on parenteral nutrition and an esmolol infusion, and was stable on his current support as the PICU staff awaited the arrival of the transport team.
Background and Comparison
The incidence of cardiomyopathies in the pediatric population are approximately 1.5 cases per 100,000. While dilated cardiomyopathies (DCM) account for the majority of pediatric cardiomyopathy cases (approximately 50%), hypertrophic cardiomyopathies (HCM) are not far behind (approximately 40%). Far less common are restrictive cardiomyopathies (RCM) and Left Ventricular Non-Compaction (LVNC) cardiomyopathies.
HCMs have been well-covered in the news in recent years as this is what most often causes sudden cardiac death in young teenage athletes. It is progressive in nature and is characterized by increased wall size of the left ventricle and ventricular septum. Poorly organized myocytes, responsible for wall growth can contribute to malignant arrhythmias, often leading to sudden cardiac death. A family history is found in nearly half of the cases of HCM.
DCMs on the other hand, are characterized by left ventricular dilation, left atrial enlargement and a reduction in systolic function. While genetics / family history can most certainly be a cause of DCM, other causes include infectious disease and toxic exposure, metabolic disorders, autoimmune disease and inflammatory processes. While clinical examination and suspicion play a key role in diagnosis, definitive identification most often occurs during echocardiography and cardiac magnetic resonance imaging (MRI).
Definitive management options can be rather limited. Infants with HCM (as in the case) have a 2-year mortality rate of 30%. Severe cases where medical management is no longer effective require cardiac transplantation or mechanical support in the form of a cardiac assist device and / or implantable pacemaker / defibrillator. Septal myomectomy can be a possible option for older children and adolescents.
ICU management depends on the type and degree of cardiomyopathy. While the respiratory symptoms of heart failure can be treated with intubation and mechanical ventilation, cardiac support in DCM and HCM can differ slightly. With the systolic dysfunction seen in DCM, management often can include inotropic support, afterload reducing agents and diuretics, just as with cases of heart failure seen in adult patients.
In HCM the goal is for the left ventricle to be “full and slow.” Diuretics are often avoided and beta blockers are typically administered. Patients can often develop hemodynamic instability from the left ventricular outflow tract obstruction that occurs due to the size of the septum and / or ventricular wall. The goal for therapy is to reduce the large pressure / flow gradient caused by this outflow tract obstruction and thus reduce myocardial oxygen demand. A slower heart rate and greater volume at end diastole allows for better cardiac filling and improved cardiac function during subsequent beats. Other medications that can assist with improved diastolic relaxation and a reduction in outflow gradient are calcium channel blockers.
Take Home Points
- Poor feeding and respiratory distress are the main clinical features for a multitude of ailments in the infant population. Realize that initially you may be treating a few diagnoses simultaneously until you are able to narrow down differentials.
- Likewise, heart failure in the pediatric population can have one of several etiologies. As the discussion points to cardiomyopathies, it is important to understand that depending on type, management strategies differ based upon systolic vs. diastolic dysfunction.
- The question of fluids vs. diuretics vs. inotropes vs. vasopressors vs. vasodilators can be quickly answered, and an appropriate management trajectory developed with point of care ultrasound (POCUS) and someone skilled in analysis beyond gross ejection fraction (EF). Ventricular wall motion, wall size, septal size, overall chamber size and outflow tract gradient on both the right and the left can provide valuable information as to what is causing heart failure in a child.
References
Choudhry, S., Puri, K., & Denfield, S. W. (2019). An Update on Pediatric Cardiomyopathy. Current Treatment Options in Cardiovascular Medicine, 21(8), 36.
Lee, T. M., Hsu, D. T., Kantor, P., Towbin, J. A., Ware, S. M., Colan, S. D., … & Addonizio, L. J. (2017). Pediatric cardiomyopathies. Circulation research, 121(7), 855-873.
Leong, K., Kane, J. M., & Joy, B. F. (2018). Acquired Cardiac Disease in the Pediatric Intensive Care Unit. Pediatric annals, 47(7), e280-e285.
Masarone, D., Valente, F., Rubino, M., Vastarella, R., Gravino, R., Rea, A., … & Limongelli, G. (2017). Pediatric heart failure: a practical guide to diagnosis and management. Pediatrics & Neonatology, 58(4), 303-312.