Pulmonary embolism (PE) is a major cardiovascular emergency, accounting for significant morbidity and associated with up to 300,000 deaths annually in the United States,1 also ranking among the leading causes of preventable hospital deaths globally. Hence, identification and investigation of patients with acute PE at high risk for adverse outcomes is critical to optimizing outcomes.2

Patients with high-risk PE have been reported to have a mortality of 41% when associated with obstructive shock and 74% following a cardiac arrest.3 An independent prognostic determinant of short-term mortality from acute PE is the presence of right ventricular dysfunction (RVD), even in patients presenting clinically as low risk and hemodynamically stable, compared to those without RVD.2,4 The presence of RVD is associated with a 4-fold increased risk of death.5

In 2019, the European Society of Cardiology (ESC), in collaboration with the European Respiratory Society (ERS), introduced updated guidelines that standardize the severity criteria in adult patients based on the risk of early mortality (in-hospital or 30-day death).6 The guidelines emphasize the role of assessing RVD and have categorized PE severity into 3 primary risk levels: high-risk, intermediate-high-risk (further divided into intermediate-low and intermediate-high), and low-risk.

High-risk (Massive PE) is defined by PE associated with hemodynamic instability, which may present as persistent hypotension (systolic blood pressure <90 mmHg or a > 40 mmHg drop lasting at least 15 minutes), obstructive shock (characterized by end-organ hypoperfusion requiring vasopressors to uphold systolic blood pressure >90 mmHg), or cardiac arrest.6 Intermediate-high-risk is characterized by PE in the presence of both right heart strain, as evidenced by chest computed tomography (CT) or transthoracic echocardiogram (TTE), and biochemical markers of myocardial necrosis, including elevated troponin-T and pro-B-type natriuretic peptide (pro-BNP).6 Intermediate-low-risk is defined by a PE with either right heart strain or biochemical evidence of myocardial necrosis, or neither, but not both.6 Low risk is identified by the absence of clinical parameters of PE, and if assessed, troponin-T and pro-BNP are negative.6 This standardized stratification system provides a critical framework for evaluating PE severity, guiding treatment decisions, and improving patient outcomes by tailoring management strategies to the risk of early mortality.

To stratify the risk associated with RVD, imaging parameters used include TTE and computed tomography pulmonary angiogram (CTPA). On TTE, the right ventricle (RV)/left ventricle (LV) end-diastolic diameter ratio provides data on RV morphology. The measurement of tricuspid annulus plane systolic excursion (TAPSE) on TTE reflects global systolic RV function. A prospective cohort study of 782 patients supports the prognosis that an enlarged RV (RV/LV end-diastolic diameter ratio >1.0) significantly increases the likelihood of PE-related mortality (hazard ratio [HR] 8.9; 95% confidence interval [CI] 1.1-74.7; P = 0.04).7 However, the most valuable predictor of 30-day mortality when using TTE is the measurement of TAPSE. Patients with a TAPSE of ≤ 16 mm at the time of PE diagnosis were significantly more likely to die from PE (HR 4.4; 95% CI 1.3-15.3; P = 0.02).7

A chest CT enables simultaneous assessment of the pulmonary vasculature and cardiac structures, providing a valuable opportunity to evaluate RVD in real-time while diagnosing a PE. According to a prospective cohort multicenter study of 457 patients, right ventricle enlargement was defined by an RV/LV end-diastolic diameter ratio >0.9.4 The study found that patients with an acute PE who were hemodynamically stable at presentation but exhibited evidence of RVD on CT were at significantly higher risk for in-hospital death or clinical deterioration (HR 3.8, 95% CI 1.3-10.9).4 Other studies have shown that an RV/LV ratio >1.0 correlates with a rising prognostic specificity and is associated with a 5-fold risk for PE-related mortality (odds ratio [OR] 5.0, 95% CI 2.7-9.2), indicating that RV/LV ratio >1.0, instead of 0.9 on CTPA may be more appropriate to predict poor prognosis.8, 9, 10, 11 Furthermore, for every 0.1 increase in RV/LV, the odds ratio for death is 1.14 (P-value = 0.023).10 The presence of septal bowing identified on CT is a beneficial finding strongly supporting the presence of RVD (specificity at 98%, positive likelihood ratio 13.6).2 These studies highlight that RVD is a key independent predictor of poor short-term outcomes in those who initially appear hemodynamically stable, thus emphasizing the need for early recognition and monitoring of RVD as part of risk stratification in an acute PE.

Both CT and TTE have demonstrated similar statistical reliability (including specificity, sensitivity, and positive and negative predictive values) in assessing RVD in the presence of a PE. These imaging techniques are comparable in their ability to identify RVD and express similar prognostic implications regarding PE-related 30-day mortality. While TTE is effective, it is not as widely accessible as CT, especially in acute settings/out-of-hours when there are less skilled operators available.4 Using CT to identify RVD may streamline the diagnostic process, reducing the need for additional investigations in hospitalized patients.

Stratifying the risk of 30-day mortality in acute PE is crucial for guiding treatment decisions. This approach can help avoid overtreatment and minimize complications, including in-hospital and iatrogenic events like bleeding associated with thrombolytic therapy. High-risk patients with hemodynamic instability are typically treated with thrombolysis.6 For patients with a contraindication to thrombolysis or in those patients where thrombolysis is ineffective, surgical embolectomy or catheter-directed therapies are alternative options.6 Assessing RV function is crucial in patients with intermediate-low-risk and clinically stable. Those with an RV/LV end-diastolic ratio <0.9 have a low risk of mortality from PE (100% negative predictive value), which may support decisions for early discharge or outpatient treatment.4