Infective pericarditis is a term that means the inflammation of the pericardium due to an infectious etiology. Different infectious causes have been linked to the development of infective pericarditis. Bacterial and fungal pericarditis usually has a more serious presentation with more severe symptoms. Viral pericarditis is becoming more commonly recognized in children.
Epidemiology of Pediatric Infective Pericarditis
In most cases of pericarditis, an exact etiology cannot be identified. The term idiopathic pericarditis is used when the cause of pericarditis is unidentifiable. The incidence of pericarditis due to viral etiologies is very high in the pediatrics’ population, up to 60%!
Bacterial pericarditis is much less common nowadays after the introduction of vaccination against the most common bacterial etiologies, namely, H influenzae and pneumococcus. The most commonly identified risk factor for bacterial pericarditis is malnutrition and overcrowding, both of which are more common in the developing world.
The peak incidence of bacterial pericarditis is observed in children younger than 4 years. Purulent pericarditis in infants is almost always caused by a bacterial etiology.
The cure rate of viral pericarditis without myocarditis is 100%. On the other hand, the mortality rate of untreated bacterial pericarditis can reach 100%. The mortality rate after adequate antibiotic and drainage treatment of bacterial pericarditis remain high, i.e. 20%. Constrictive pericarditis can develop as a complication to purulent pericarditis.
Etiology of Pediatric Infective Pericarditis
Infective pericarditis is usually a complication of an ongoing bacterial infection of the lungs or other adjacent organs. The most commonly identified bacterial organisms are staphylococcus aureus, Haemophilus influenzae, and streptococcus pneumoniae. Gram-negative bacteria have been also implicated in infective pericarditis.
Pathophysiology of Pediatric Infective Pericarditis
Once a bacterial or viral agent gets entry into the pericardium, that infectious agent can grow or replicate and an inflammatory response is started. Because of this inflammatory response, the pericardium’s permeability to proteins, inflammatory cells and fluid increases. The consequence of this pathogenic phenomenon is the accumulation of fluid in the pericardium.
In non-infectious causes of pericardial effusions, the pericardium is usually flexible and can expand largely before symptomatology starts occurring. In infective pericarditis, however, the pericardium is usually stiff and cannot expand. Because of this, symptoms of infective pericarditis are usually disproportionate to the amount of fluid accumulated inside the pericardial space.
Fluid accumulation in the pericardium impacts venous return to the heart. Because of decreased venous return, the cardiac output is also decreased. When the pericardial effusion happens too fast, a tamponade occurs. In that case, the patient becomes hemodynamically unstable due to impaired diastolic filling.
Clinical Presentation of Pediatric Infective Pericarditis
The presentation of bacterial and viral infective pericarditis is different. Viral pericarditis is mainly characterized by chest pain and a fever. Patients are usually not very toxic-appearing, except when their disease is complicated by concomitant myocarditis.
Chest pain might radiate to the left shoulder. Sitting position usually alleviates the pain, while respiratory motion is known to exacerbate the pain. Patients usually prefer a sitting position and to lean forward, rather than lying down. Flu-like symptoms, such as a runny nose and a cough, might also be present in viral pericarditis.
Patients with bacterial pericarditis are usually more poorly, have another infectious focus such as pneumonia, and have a high-grade fever. Respiratory distress and tachycardia are also common signs of bacterial pericarditis. Like viral pericarditis, patients usually complain of chest pain that is alleviated by sitting and leaning forward.
A pericardial friction rub is commonly heard in children with viral pericarditis. A friction rub might not be audible in bacterial pericarditis, especially in young infants with purulent pericarditis. Patients with large pericardial effusions might not have a friction rub. When pericardial effusions are large, heart sounds become muffled.
Patients might also develop cardiac tamponade which is characterized by weak peripheral pulses, cool hands and feet, low blood pressure and tachycardia. Heart sounds on examination are usually muffled. The symptoms of cardiac tamponade are due to venous congestion due to impaired venous return to the heart and a low cardiac output. Due to venous congestion, an elevated nonpulsatile jugular venous pulse might be evident on physical examination if the patient develops a cardiac tamponade. Pulmonary edema might also develop as a complication to venous congestion.
Pulsus paradoxus is characterized by an inspiratory decrease in blood pressure of more than 10 mm Hg, and is commonly seen in patients with cardiac tamponade.
Diagnostic Workup for Pediatric Infective Pericarditis
A complete blood count is indicated in suspected cases of infective pericarditis. Patients with viral pericarditis might have lymphocytosis. Patients with bacterial pericarditis usually have leukocytosis.
Blood cultures in addition to nasopharyngeal and stool samples should be obtained for the isolation and identification of the most likely causative organism.
Erythrocyte sedimentation rate and c-reactive protein are usually elevated in patients with infective pericarditis.
When a pericardial effusion is present, tapping of the effusion is usually indicated. Gram stain and culturing of the pericardial effusion might help in identifying the causative organism. Polymerase chain reaction testing of the fluid collected from the pericardial effusion can also help in the identification of the causative viral agent.
A chest x-ray can reveal cardiomegaly. The heart is not, in fact, enlarged in patients with infective pericarditis, but one can get that impression due to the enlarged pericardium because of fluid accumulation.
Pericardial effusions are best evaluated by echocardiography. The location of the effusion, the determination of the size of the effusion and the identification of other complications, such as myocardium involvement, can be all assessed on echocardiography.
Electrocardiography is also indicated in patients suspected to have pericarditis. Possible findings on electrocardiography include ST segment elevation and a low voltage QRS complex.
Patients who have signs suggestive of cardiac tamponade should undergo a pericardiocentesis. This procedure helps in alleviating the pressure on the four heart chambers and can also be diagnostic. In addition to culture and sensitivity testing, and polymerase chain reaction testing, patients should also get the lactate dehydrogenase and protein levels in their pericardial effusion fluid assessed. Pericardiocentesis can be guided by echocardiography.
Treatment of Pediatric Infective Pericarditis
Nonsteroidal anti-inflammatory drugs (NSAIDs) are indicated in the treatment of viral pericarditis. Patients with viral pericarditis usually do well with pain management and salicylates, and antiviral therapy is generally not indicated.
Patients who do not respond to NSAIDs should receive corticosteroids. Corticosteroids have been linked to rapid symptomatic improvement, but an increased risk of recurrent pericarditis.
More recently, colchicine has been evaluated as a first-line therapy for acute viral pericarditis. Colchicine was found to be effective in decreasing the rate of recurrence, and in alleviating the symptoms of viral pericarditis.
Empirical antibiotic therapy for bacterial pericarditis includes a penicillinase-resistant penicillin and a third-generation cephalosporin. Oxacillin or nafcillin, combined with cefotaxime or ceftriaxone, are good options for the antibiotic therapy for bacterial pericarditis. Once the causative bacterial etiology is identified, a narrow-spectrum antibiotic should be used to avoid the emergence of antibiotic resistance.
Pericardiocentesis can be therapeutic and diagnostic at the same time in cases of cardiac tamponade. Patients who do not respond to pericardiocentesis should undergo emergent surgical drainage. Patients with purulent pericarditis might also require surgical drainage of the pericardium.