Pediatric Cardiogenic Shock
- Dec 5th, 2014
- Jason Long
Pediatric Cardiogenic Shock
By Jason D. Long MD and Hilary E. Fairbrother MD, MPH
Emergency Medicine, New York Methodist Hospital
Edited by Alex Koyfman MD and Stephen Alerhand MD
————-> The Pediatric Emergency Department is humming with the playful and terrified screams of children of all ages. You pick up the next patient to be seen: a 2 year-old boy coming in for abdominal pain and vomiting. Vital signs are Temperature 99.5 (rectal), Heart Rate 145, Blood Pressure 76/55, Respiratory Rate of 32, and Saturation 97%. The mother tells you that for 2 weeks the child has been eating less, complains of his stomach pain every day, and has vomited after eating several times in the last few days. She went to see his PMD about a month ago for a fever, but other than that, the child has been healthy. All his immunizations are up to date. No recent travel. Physical exam shows normal TMs, a non-erythematous oropharynx, no cervical lymphadenopathy, clear lungs (though he has increased work of breathing), and RUQ tenderness with moderate hepatomegaly. You order basic labs and liver enzymes. You also order a 20cc/kilogram bolus of normal saline because the child has been vomiting and is tachycardic.
What is your differential at this point? Hepatitis, gastroenteritis, viral syndrome? Sepsis? Does he appear to be in shock? Would the possibility of heart failure be in the recesses of your mind? Perhaps not with the limited information provided. Many initial presentations of pediatric cardiogenic shock are missed, not only because the condition is relatively rare, but also because the presenting complaints are often non-specific.
Shock is a state of inadequate tissue perfusion – the cardiovascular system failing the metabolic needs of the rest of the body. Hypovolemic shock is the most common type of shock seen in children. Distributive shock in children is usually caused by sepsis. Neurogenic shock is rare. This article will focus on cardiogenic shock – decreased systolic function and depressed cardiac output.
At first, shock can be compensated for by increasing the cardiac output through elevated heart rate and contractility. Decreased flow to the kidneys activates the renin / angiotensin / aldosterone system leading to fluid retention. Sympathetic activation increases contractility. Peripheral vasoconstriction shunts blood to more vital organs. This response is typically robust in children, allowing them to maintain a normal blood pressure for a prolonged period despite decreased cardiac output. Patients in compensated shock generally have some signs of decreased perfusion such as cool skin, decreased peripheral pulses, tachycardia, and/or oliguria. Eventually compensation will fail. The pediatric patient may present either compensated or decompensated and the signs and symptoms will be correspondingly different, but will also vary with the cause of shock and the age of the child.
Infants may present with only failure to thrive or diaphoresis with feeding. Older children may present with malaise, anorexia, dyspnea, or abdominal pain. In one cross-sectional study of children in heart failure, the vast majority had at least one gastrointestinal complaint (most commonly nausea and vomiting) and at least one respiratory sign or symptom (most commonly dyspnea or increased work of breathing). Hepatomegaly, tachypnea, and tachycardia were the most common presenting signs.iii
More than 14,000 pediatric heart failure-related hospitalizations occur annually in the United States. Most of these children have some form of congenital heart disease. While these cases are obviously important to be aware of, this discussion will focus on heart failure from other etiologies such as intrinsic and acquired conditions, arrhythmias, ischemic, and exposure-related cardiomyopathies. These categories together comprise a varied list of causes (table 1 – this table is not exhaustive).
————-> You reassess your 2 year-old after seeing the fluid bolus is done. He is still tachycardic and appears to have worsening SOB, with some nasal flaring that you did not notice before. You order an EKG and a CXR. The EKG shows sinus tachycardia with low-voltage QRS complexes. Repeat rectal temperature: 99.1. Labs show: mild hyponatremia; BUN and creatinine within normal limits; mild elevation of liver enzymes. CXR shows cardiomegaly without increased pulmonary vascular markings. You add on a pro-BNP, UA, and lactate, and re-examine the patient: still tachypneic, still with nasal flaring, lungs are clear, but now you notice that the child’s capillary refill is delayed and the extremities are cool. When the pro-BNP comes back at 1,900, the urinalysis is clean, and the lactate is 1.09, you finally accept your and the child’s bad luck, order lasix 1mg/kg IV and call the PICU attending for admission.
Diagnosis and admission of cardiogenic shock can be delayed by this condition’s insidious presentation. In one study, misleading presenting symptoms led to 26% of patients inappropriately receiving an initial fluid bolus in the setting of heart failure. Point-of-care echocardiography (POCE) is possible in the ED if the physician is appropriately trained, with one study showing a sensitivity of 95% and specificity of 83% in regards to LV dysfunction, pericardial effusion, and IVC collapsibility.
The overall hospital mortality for these children is 7%. Children who are hospitalized with heart failure have a 20-fold increase in the risk of death during hospitalization.ii Rapid detection may improve outcome. Early initiation of vasoactive therapy in adults is associated with lower rates of ICU transfers from other units and higher hospital discharge rates. Acutely, dopamine, epinephrine, milrinone, and inamrinone can be used to support contractility, however, dopamine and epinephrine cause increased myocardial oxygen consumption.i Randomized trials of effective therapy in pediatric heart failure are lacking, and subsequently most of the therapy is based on adult models. Fluid overload is treated with lasix. Afterload reduction with oral ACE inhibitors is common, however, it is contraindicated in patients with renal insufficiency or right-to-left shunts. Beta-blockers and digoxin are used in more stable patients as long-term therapies, though digoxin is contraindicated in acute myocarditis due to its proarrhythmogenic potential.
Treatment should be tailored to the specific etiology of the heart failure, especially when an unusual cause is at play. Case reports exist of heart failure following scorpion sting , ophthalmic drugs , hypocalcemia , as well as cumulative dose-dependent anthracycline-mediated cardiomyopathy . In these instances, amiodarone, supportive care, calcium, and judicious use of anthracyclines seem to be effective treatments, respectively.
Cardiomyopathy is usually idiopathic. Myocarditis is a particularly important cause though, contributing to 30-35% of dilated cardiomyopathy and myocarditis has a high association with sudden death in children. The natural history of myocarditis generally falls into two categories: fulminant myocarditis and acute myocarditis. Fulminant myocarditis is characterized by the onset of symptoms over 1-2 days with hemodynamic compromise requiring inotropic support. Surprisingly, the fulminant myocarditis patients seem to fare better with survival rates as high as 91%. x This is in spite of a significant proportion of these patients requiring mechanical ventilation or even ECMO. Though the children with acute myocarditis have a poorer prognosis, overall survival remains high at nearly 80%. ix
————-> While in the PICU, your 2 year-old receives a full work-up. Echocardiography shows dilated cardiomyopathy. Troponins come back positive and repeatedly hover around 0.75. Cardiac MRI is consistent with myocarditis. IVIG therapy is initiated. Serial EKGs begin to show diffuse ST segment elevations and then second-degree atrioventricular block. On day three, serologies for adenovirus, echovirus, coxsackie virus, CMV, and EBV come back negative. Anti-Ro, anti-La, anti-nuclear antibody, anti-double stranded DNA, and rheumatoid factor titers are all undetectable. On day five, the child goes into cardiac arrest. The resuscitation team achieves ROSC in 5 minutes and initiates ECMO. Echocardiography at this time shows diffuse hypokinesis with an estimated ejection fraction of 10%. He is placed on the priority list for heart transplantation.
Acute myocarditis is an example of an etiology of heart failure that can progress to profound cardiac dysfunction and even death. Recommended therapy is generally supportive. IVIG is given in more than 70% of myocarditis cases.xi However, it remains controversial whether IVIG therapy conveys a mortality benefit. Diagnosis of myocarditis is challenging, as there are so many potential causes. Viral offenders have evolved over the past 20 years from adeno- and enteroviruses to more commonly include parvovirus and herpes virus 6.x Autoimmune-mediated myocarditis can benefit from immunosuppression, but other causes likely do not.ix For many of those unfortunate pediatric patients that go on to refractory cardiogenic shock, mechanical circulatory support is a life-saving measure. ECMO is used in nearly 20% of American children hospitalized with myocarditis. And of patients requiring ECMO or a ventricular assist device, the sickest of the sick, roughly 60% showed recovery of myocardial function. The ones that do not recover cardiac function while on mechanical circulatory support have only one option for improved cardiac function: transplantation. In one case series, waiting list mortality was 42.9% with an average of 25 days. Other short-term mortality estimates vary between 20-31%. Survival after transplantation is roughly 70% at five years.ix
————-> Within seven days of being on ECMO, the child’s cardiac function began to improve. By ECMO day 10, his ejection fraction is 35%. He is removed the next day and maintains signs of adequate tissue perfusion. After just over three weeks in the hospital, he is discharged home on lisinopril and spironolactone.
Summary and Pearls
Pediatric cardiogenic shock is an often insidious phenomenon with presentations requiring a broad differential diagnosis. Even after narrowing the diagnosis to cardiogenic shock, the list of possible etiologies is vast and the cause important to determine because the source of the shock will respond differently to different treatments. Limited randomized controlled trials exist in children, so the majority of therapies are based on what has worked in adults. Despite often having a dramatic course, the prognosis for children with heart failure is good if their management is conducted appropriately.
• Maintain a high index of suspicion: if you don’t suspect it, you likely won’t find it
• History and physical can accurately guide you early: a combination of unexplained tachypnea and gastrointestinal symptoms should raise your suspicion
• Ancillary tests like the EKG and pro-BNP can be helpful to quickly direct your clinical pathway toward impaired cardiac function.
• CXR is your best quick radiologic investigation: cardiomegaly was apparent in 98% of cases in one studyiii. Bedside echo (POCE) is helpful as well.
• Involve your pediatric cardiologist as soon as possible: early appropriate vasoactive therapy will likely benefit the patient.
[i] Gary R. Strange, William R. Ahrens, Robert W. Schafermeyer, Robert A. Wiebe, Pediatric Emergency Medicine, 3e, Chapter 48: Congestive Heart Failure
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[ix] Burch M. Heart failure in the young. Heart. 2002 Aug;88(2):198-202. Review. PubMed PMID: 12117860; PubMed Central PMCID: PMC1767239
[x] Canter CE, Simpson KP. Diagnosis and treatment of myocarditis in children in the current era. Circulation. 2014 Jan 7;129(1):115-28. doi: 10.1161/CIRCULATIONAHA.113.001372
[xi] Ghelani SJ, Spaeder MC, Pastor W, Spurney CF, Klugman D. Demographics,trends, and outcomes in pediatric acute myocarditis in the United States, 2006 to 2011. Circ Cardiovasc Qual Outcomes. 2012;5:622–627
[xii] Jatene MB, Miana LA, Pessoa AJ, Riso A, Azeka E, Tanamati C, Gimenez S, Lopes AA, Marcial MB, Stolf NA. Pediatric heart transplantation in refractory cardiogenic shock: a critical analysis of feasibility, applicability and results. Arq Bras Cardiol. 2008 May;90(5):329-33. English, Portuguese. PubMed PMID: 18516404