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Abstract & Commentary
By Michael H. Crawford, MD, Professor of Medicine, and Chief of Clinical Cardiology, at the University of California, San Francisco. Dr. Crawford is on the speaker's bureau for Pfizer.
Source: Imazio M, et al. Indicators of Poor Prognosis of Acute Pericarditis. Circulation 2007:115:2739-2744.
Most cases of acute pericarditis are due to idiopathic or viral causes and have a benign prognosis with symptomatic treatment. How to identify those cases due to specifically treatable causes or those who are not going to do well would be useful to know. Thus, this group from Torino, Italy, studied 453 patients who met criteria for acute pericarditis in the absence of acute myocardial infarction. Patients were included if they met 2 of the following criteria for acute pericarditis: typical pericarditis chest pain; pericardial friction rub; diffuse ST elevation or PR depression on ECG, and new or worsening pericardial fluid on echocardiogram. Myopericarditis was diagnosed if one of the following were present: elevated cardiac enzymes and new focal or diffuse left ventricular dysfunction by echocardiogram. All patients had coronary artery disease excluded by stress nuclear perfusion scintigraphy or coronary angiography. Pericardial tamponade was diagnosed using a combination of clinical and supportive echocardiographic signs. Clinical features in the literature associated with a poor prognosis or specific diagnoses were assessed for their predictive ability. Patients were prospectively enrolled from 1996 to 2004.
Results: A specific cause was discovered in 17% of the patients. Corticosteroid treatment was employed initially in about 25%. Multivariate analysis identified women (RR 1.67); fever (3.56), subacute course (3.97), large effusion or tamponade (2.15) and NSAID failure (2.5) as predictors of a specific cause. Elevated troponin predicted a lower risk of a specific cause (0.37). After a mean follow-up of 31 months, 21% of patients had a complication: recurrence in 18%, tamponade 3% and constriction 1.5%. Patients with a specific cause had a higher rate of complications (38 vs 18%, p < 0.001).
Multivariate analysis showed that women (RR 1.65), large effusion or tamponade (2.51) and NSAID failure (5.50) were predictive of complications. Corticosteroid use was associated with more complications in idiopathic or viral pericarditis (48 vs 14%, p < 0.001). The authors concluded that fever, sub acute course, large effusions or tamponade and NSAID failure may help predict those more likely to have a specific cause of acute pericarditis or those more likely to suffer a complication.
This is a potentially clinically useful study, since currently in the developed world acute pericarditis is usually admitted to the hospital. Deployment of this risk stratfication scheme could result in sending home the 80% of patients who have a viral or idiopathic etiology who are highly likely to do well. The predictors include laboratory tests and echocardiography, which would have to be readily available in the acute care setting. Let's look at the multivariate predictors identified. Female sex is not very useful as it means admitting roughly half the patients. Also, the risk ratio is < 2.0 for this variable, which is not a strong predictor. All of the other predictors have risk ratios > 2.0 . Two of the predictors identified predict specific causes and a higher risk of complications, so they would be the most valuable clinically (large effusion or tamponade and NSAID failure). Others are associated with a specific cause only: fever and subacute course. Elevated troponin was associated with lack of a specific cause.
Translating this into practice if a patient with acute pericarditis has a large effusion or tamponade, they should be admitted because these features predict complications and a specific cause. NSAID failure should also be admitted for the same reason, but this is likely to be an unusual presentation. Febrile patients or those with an indolent course likely have a specific cause that could be evaluated as an outpatient in some settings. An elevated troponin and a lack of other high-risk features would reinforce the decision to send the patient home, as long as acute myocardial infarction is excluded. Remember, the most common cause of acute pericarditis in a middle-aged man is acute infarction. These patients were excluded from this study. If you are on the fence about what to do, female sex could be used to tip the balance toward admission.
This study confirms the impression that about 80% of non-infarction-related acute pericarditis is idiopathic or viral, so most patients should not need hospitalization. Based upon their data, the most common specific causes of acute pericarditis are autoimmune disease, neoplasm and tuberculosis with or without HIV. Other bacterial causes are rare (< 1%). This may be different in less developed countries. The study also suggests the notion that steroids should not be the initial therapy of idiopathic/viral pericarditis as they increase the likelihood of recurrences. Finally, some clinical features such as warfarin use, trauma and immunosuppressed state were too infrequent to make clear judgment about their risk prediction potential.