CHICAGO — The Pulmonary Embolism Severity Index provides clinicians with a useful tool for selecting patients with acute pulmonary embolism for outpatient therapy, Col. Lisa K. Moores, MC USA, said.
Recent evidence suggests that many patients presenting in the emergency department with nonmassive pulmonary embolism (PE) can be safely treated as outpatients using low-molecular-weight heparins or discharged early. Based on this growing body of evidence, the British Thoracic Society now recommends outpatient treatment for clinically stable patients with PE.
The Pulmonary Embolism Severity Index (PESI) and Geneva score are two standardized prognostic models that have been recently developed to identify patients at low risk for PE. The PESI uses 11 clinical findings routinely available at presentation that were previously shown to be associated with mortality in patients with PE or other acute diseases, said Dr. Moores, assistant dean for clinical sciences at the Uniformed Services University of the Health Sciences, Bethesda, Md.
These variables include demographics (age and male sex), comorbid conditions (cancer, chronic heart failure, and chronic lung disease), and six signs, including a heart rate of 110 bpm or more, systolic blood pressure less than 100 mm Hg, respiratory rate of 30 bpm or more, temperature less than 36° C, altered mental state, and oxygen saturation less than 90%.
A score is calculated by using age, then adding points based on the various factors present. Patients are then stratified by their score into five severity classes of increasing risk of death and other adverse outcomes.
A validation study demonstrated that patients in PESI class I (no more than 65 points) and class II (66–85 points) had a 30-day mortality of 1.6% or less and 3.5% or less, respectively (Am. J. Respir. Crit. Care Med. 2005;172:1041–6). Nonfatal cardiogenic shock or cardiorespiratory arrest occurred in 1% or less in class I and 1.3% or less in class II, and no patient in these two classes had nonfatal bleeding or recurrent venous thromboembolism, Dr. Moores said at the annual meeting of the American College of Chest Physicians (ACCP).
The Geneva score has been validated in two studies and uses six factors to stratify patients as low risk (up to 2 points) or high risk (3 points or more). Those factors are cancer, heart failure, previous deep vein thrombosis, systolic BP less than 100 mm Hg, arterial oxygen pressure less than 60 mm Hg, and deep vein thrombosis on ultrasound. Of 180 low-risk patients, only 4 (2%) had an adverse outcome, compared with 23 of 88 (26%) high-risk patients (Thromb. Haemost. 2000;84:548–52).
Dr. Moores acknowledged that the PESI model is “harder to get your hands around” than the Geneva model, but said some of the most intriguing data of 2007 suggests that the PESI is “more accurate and clinically useful.” An independent, head-to-head comparison in which the models were retrospectively applied to a cohort of 599 patients with objectively confirmed PE, indicated a 30-day mortality in Geneva low-risk patients of 5.6%, compared with a mortality in PESI low-risk (class I and class II) patients of 0.9% (Chest 2007;132:24–30). The PESI classified significantly fewer patients as low risk than did the Geneva model (36% vs. 84%), but the area under the receiver operating characteristic curve was higher for the PESI (0.76 vs. 0.61).
“More patients can be classified via Geneva as low risk, but the difference in mortality rates between the two systems suggests doing it more safely with the PESI,” she said.
Dr. Moores suggests that patients with a higher PESI class (class III-IV) should be observed in the ICU or a telemetry unit for the first 24 hours. In addition, clinicians should consider evaluating biomarkers in these patients such as troponin, brain natriuretic peptide, and N-terminal pro-brain natriuretic peptide levels, which when elevated have been correlated with PE death.
An audience member asked if the PESI or Geneva models can be used to select patients for thrombolysis, but Dr. Moores said the predictive values drop off in higher risk patients. “Where the crossover point is to say a patient needs thrombolysis is not yet available,” she said.