Malignant Pericardial Effusion
Echocardiography in pericardial effusion with tamponade shows right atrial or right ventricular compression, or left atrial compression, decreased left ventricular dimension, and absence of collapse of the inferior vena cava on deep inspiration.[6,25] Echocardiography findings predictive of pericardial tamponade have been reported. Right atrial collapse has a sensitivity of 55% to 60% and a specificity of 50% to 68%. Right ventricular diastolic collapse has a lower sensitivity of 38% to 48% but a higher specificity ranging from 84% to 100%. Because neither finding provides 100% sensitivity and specificity, patients who are clinically symptomatic should have a diagnostic pericardiocentesis, even in the absence of definitive findings on echocardiography.[4,27] One study found right atrial collapse present in only 42% of patients and right ventricular collapse in 62%. Nonetheless, 80% of patients with malignant pericardial effusions had symptomatic relief following pericardiocentesis.
The most definitive test for the diagnosis of cardiac tamponade is equalization of diastolic pressures between all cardiac chambers on right-heart cardiac catheterization. This invasive technique, however, is not necessary to diagnose tamponade.
Electrocardiograms in patients with pericardial effusions typically show diminished QRS amplitude in all leads. A classic but uncommonly seen finding in large effusions with pericardial tamponade is variation in the amplitude of the P wave and QRS complex in successive beats on EKG, referred to as electrical alternans. This finding results from movement of the heart within the pericardial sac. Electrocardiography is not sufficiently sensitive to diagnose pericardial effusions.
Pericardial fluid cytology has an accuracy of 80% to 90% in diagnosing malignant pericardial effusion.[6,28] Lymphomas and mesothelioma have higher false-negative detection rates on cytology evaluation.[6,29] Pericardial fluid cytology has a specificity of up to 100%, but sensitivity ranges from 57% to 100% [Level of evidence: II] in patients with a known cancer diagnosis and pericardial fluid. Because nonmalignant causes of pericardial effusion can occur in 42% to 62% of patients with cancer and pericardial fluid, a negative cytology examination of pericardial fluid does not help distinguish malignant from nonmalignant causes. The use of more than one cytological preparation (such as concentrating the sample via cytospin, using special markers, or analyzing DNA content) increases the yield over a single preparation; however, multiple samples using the same technique did not significantly increase the diagnostic yield in a retrospective study of 215 patients. In a survey of 80 samples, measurement of DNA index via flow cytometry of pericardial fluid has a sensitivity of 94.8% and a specificity of 100%, compared with routine cytology with a sensitivity of 98.5% and a specificity of 92.3%.[Level of evidence: II] Pericardial biopsy may increase the sensitivity of diagnosing pericardial effusions of malignant origin. Because pericardial effusions usually occur in advanced disease and portend a shorter survival than do other sites of metastatic involvement, however, the relief of symptoms rather than diagnosis should be the overriding factor in determining the extent of the evaluation and the course of treatment. Two studies failed to show a difference in survival in cancer patients with pericardial effusion dependent on the results of fluid cytology.[10,32]