Things We Do for No Reason: Routine Echocardiography in Hemodynamically Stable Patients with Acute Pulmonary Embolism

Echocardiography is a common method for evaluating RVD, and echocardiographic RVD confers an increased risk of adverse outcomes in PE.^10-12 In the earliest meta-analysis to evaluate this association, Sanchez et al. combined data from five studies that included 623 patients from emergency room and inpatient settings. They found that echocardiographic RVD conferred an unadjusted relative risk for short-term mortality of 2.53 (95%CI 1.17-5.50).¹² A subsequent meta-analysis by Cho et al. pooled data from both prospective and retrospective cohorts to examine short-term mortality in a total of 3,283 hemodynamically stable patients with PE, of whom 1,223 (37.3%) had RVD diagnosed by echocardiogram.¹⁰ In this population, RVD was associated with an odds ratio of 2.29 (95%CI 1.61-3.26) for short-term death. Thus, echocardiography could be viewed as a risk stratification tool, even in hemodynamically stable PE.

For most hemodynamically stable patients, echocardiographic findings will not enhance prognostication and/or have a therapeutic impact. The following four reasons explain why echocardiography adds little value to the care of these patients.

First, phenotypic expression of RVD varies from asymptomatic, despite abnormalities on diagnostic testing, to obstructive shock. Unfortunately, available prognostic models classify echocardiographic RVD in a binary fashion (present/absent)^4,7,10 whereas RVD exists on a continuum. Consequently, RVD is commonly found in acute PE^8,10,11 and has been identified in more than half of patients hospitalized with PE referred for echocardiography.⁸ Existing data do not allow clinicians to judge the clinical impact of the severity of echocardiographic RVD,⁸ and only the phenotypic expression of refractory hypotension has clear therapeutic implications.^6,7

Second, while echocardiographic RVD is associated with short-term mortality,^10-12 absolute rates of adverse outcomes are quite low when RVD is identified. For example, in a study merging multiple prospective cohorts, Becattini et al. demonstrated that RVD diagnosed by echocardiography or CT occurred in 41% of hospitalized patients stratified to low-risk PE by the simplified Pulmonary Embolism Severity Index (sPESI).⁸ For these patients, the 30-day mortality was 1.2%,⁸ which approximates the expected mortality from a low-risk sPESI score alone (1.1%).¹³ Even among intermediate-risk acute PE patients with RVD and/or elevated troponin enrolled in thrombolysis trials, the overall risk of death at 30 days was approximately 2%-3%, irrespective of the treatment arm.^5,14,15

Third, RVD identified by echocardiography does not inform or enhance prognostication as compared with cardiac biomarker testing. In a meta-analysis by Sanchez et al., echocardiographic RVD predicted death with a risk ratio of 2.53 (95% CI 1.17-5.50).¹² However, both elevated cardiac troponin and brain natriuretic peptide indicated a significantly worse outcome than imaging findings, with risk ratios of 8.3 (95% CI 3.6-19.3) and 9.5 (95% CI 3.2-28.6), respectively.¹³ More recently, Jiménez derived and validated a multivariable risk prediction model for stable PE.¹¹ In their data, echocardiographic RVD had an unadjusted odds ratio of 2.62 (95% CI 1.54-4.45) for predicting a 30-day complicated course. After multivariable adjustment that included sPESI scores, lower extremity ultrasound results, and cardiac biomarker testing, these odds became insignificant.¹¹ In other words, identifying echocardiographic RVD did not improve prognostication in hemodynamically stable PE patients when other commonly available variables were used.

Finally, in hemodynamically stable patients, echocardiographic RVD might create patient anxiety and cause harm. In a recent retrospective cohort study of 64,037 stable patients with PE, exposure to echocardiography was associated with a five-fold increase in likelihood of having received thrombolysis without any significant differences in risk-adjusted mortality.¹⁶ These data suggest that when faced with an abnormal echocardiogram, clinicians and patients may opt for more aggressive, time-sensitive therapies. Basing thrombolysis decisions on echocardiographic RVD potentially subjects patients to harm without decreasing mortality.^5,14,15 For example, the PEITHO study, which was the largest randomized trial evaluating thrombolysis in intermediate-risk acute PE, enrolled 1,006 patients and demonstrated that treating 29 intermediate-risk patients with thrombolysis prevented one case of hemodynamic decompensation.⁵ These benefits were counterbalanced by a number needed to harm of 14 to cause stroke or major bleeding. Ominous echocardiographic findings may also bias clinicians toward more intensive monitoring. Rates of echocardiogram utilization in hemodynamically stable PE are linked to higher rates of ICU admission and longer hospital stays without significant impact on patient outcomes.¹⁶