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The Speed of Sound: A New Measure to Single Out High-Risk PE Patients

Butts, Christine MD

doi: 10.1097/01.EEM.0000513576.29468.70
The Speed of Sound

Dr. Butts is the director of the division of emergency ultrasound and a clinical assistant professor of emergency medicine at Louisiana State University at New Orleans. Follow her on Twitter @EMNSpeedofSound, and read her past columns at http://bit.ly/EMN-SpeedofSound.

Predicting which pulmonary embolism patients will do well with oral anticoagulation and which will decompensate is a bit murky, at best.

The treatment of pulmonary embolism (PE) has evolved quite a bit in just the past few years. Direct oral anticoagulants mean there is no longer a need to bridge patients to warfarin, and a push to treat more patients as outpatients followed. Peripheral, subsegmental PEs appear to pose little risk to a patient's short-term morbidity and mortality, but what about segmental or submassive PEs?

We know that patients who present with hypotension or hypoxia should be monitored and probably treated more aggressively than just standard anticoagulation, but what about those who look pretty good on presentation?

Echocardiography has value in determining the severity of a pulmonary embolism. Signs of right heart strain can be detected by comparing the overall right ventricular size with the left ventricle, looking at the dynamics of the septum, and searching for the presence of McConnell's sign (regional akinesis of the right ventricular free wall). Some of these findings can be subtle and hard to quantify, however. McConnell's sign in particular falls into the “you'll know it when you see it” category and is intimidating to many. Prognosticating based on these signs alone in hemodynamically stable patients hasn't been shown to be successful.

Tricuspid annular plane systolic excursion (TAPSE) shows promise as a reproducible method of assessing right ventricular strain and predicting outcome. The right ventricle (RV), unlike the left one (LV), is difficult to characterize in terms of an ejection fraction. Its shape and dynamics don't lend well to an easily measurable percentage. TAPSE, however, measures the extent to which the RV contracts in the longitudinal plane (parallel to its long axis), and may give an idea of RV function. The shortening and lengthening of the RV can be measured by placing the M-mode cursor along the long axis of the RV in the apical view, bisecting the tricuspid annulus (the point of attachment of the valve). (See image.) The greater the difference (the more it contracts), the better the function of the RV.

What does this mean for PE? Two recent studies found some promising findings for TAPSE in hemodynamically stable patients with submassive and segmental PEs. (J Thromb Haemost 2014;12[7]:1020; JACC Cardiovasc Imaging 2014;7[6]:553.) Both studies found that an abnormal TAPSE was associated with an increased risk of clinical deterioration, which resulted in the need for thrombolysis or cardiovascular support. Mortality risk was higher in these patients as well. Patients with a normal TAPSE were at lower risk of death or deterioration. This measurement also appears to be less user-dependent than other methods of assessing the RV, such as the end-diastolic diameter and RV/LV ratio. (Cardiovasc Ultrasound 2014;12:29.)

Echo can be intimidating, but mastering TAPSE can serve as a tool to identify high-risk hemodynamically stable patients with submassive and segmental PE.

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