Radiation induced pericarditis


 * Associate Editor(s)-In-Chief: Varun Kumar, M.B.B.S.; Lakshmi Gopalakrishnan, M.B.B.S.

Overview
The survival rate in Hodgkin lymphoma, Non-Hodgkin's lymphoma and breast carcinomas has significantly improved with use of radiation therapy. However, radiation therapy to thoracic and mediastinal cancers have also led to development of pericarditis, coronary artery disease, cardiomyopathy, conduction abnormalities in heart and valvular heart diseases which account for significant morbidity and mortality. The incidence is higher with doses greater than 40 Gy (4000 rad).

Epidemiology
Incidence of radiation induced pericarditis has significantly decreased with the use of lower doses and newer radiotherapy techniques. In a study, incidence decreased from 20% to 2.5% with the changes in methods of RT administration

In as study among pediatric population with various cancers, radiation therapy with ≥15 GY increased the risk of developing pericarditis by two to six times

Pathophysiology
Radiation exposure causes endothelial damage, capillary rupture, and platelet adhesion which initiates an inflammatory response and leads to development of adhesions between the two membranes of pericardium. Collagen and fibrous deposition occur on the outer layer of the heart leading to pericardial fibrosis, effusion, and sometimes tamponade

Radiation induced pericarditis depends on:
 * 1) Total dose of radiation
 * 2) Amount of cardiac silhouette exposed
 * 3) Nature of the radiation source
 * 4) Duration and fractionation of therapy

In a retrospective study, 27.7% of the patients developed pericardial effusion after median time period of 5.3 months following radiotherapy for esophageal carcinoma with radiation dose ranging between 3 to 50Gy. It was concluded that high dose-volume of the irradiated pericardium and heart increased the risk of developing pericarditis.

History and symptoms
Radiation induced pericarditis may present in two forms:
 * Acute pericarditis
 * Late onset pericarditis occur from about a year to up to 20 years after exposure

Patients may present with the following symptoms:
 * Fever
 * Chest pain that improves on leaning forward and worsens on inspiration
 * Breathlessness
 * Dizziness
 * Palpitation
 * Malaise
 * Ankle edema

Physical examination
Patients may present with fever

Vitals: Hypotension, tachycardia

Neck: Jugular venous distension with a prominent Y descent and Kussmaul's sign

Chest: Ewart's sign may be present. This includes a pericardial knock, pericardial rub(heard best while leaning forwards) and distant heart sounds

Abdomen: Hepatomegaly, ascites

Extremities: Ankle edema

Electrocardiogram
Non-specific ST and T wave changes or ST segment elevation in all leads may be noted.

Pericardiocentesis
Radiation induced pericardial effusion can be confused with malignant pericarditis and hypothyroidism (secondary to mediastinal irradiation) induced pericarditis. Pericardiocentesis can be used to differentiate them with fluid analysis for malignant cells and thyroid function tests.

Treatment

 * Pericarditis with large effusion can be drained either percutaneously or surgically
 * Those with recurrent pericardial effusion can be treated with pericardiotomy(pericardial window) or by surgical stripping.
 * Pericardiectomy is recommended for patients who develop constrictive pericarditis. However, the perioperative mortality rate is higher in postradiation constrictive pericarditis compared to that of idiopathic constrictive pericarditis.