In this issue of Polish Archives of Internal Medicine, Stępniewski et al¹ present the results of a survey focusing on adherence to the 2019 European Society of Cardiology guidelines for management of acute pulmonary embolism (PE), specifically the current practices with regard to diagnosis and risk stratification.^2,3 Their findings are notable: the guidelines are hardly followed, especially when it comes to the applied diagnostic algorithm in daily practice, independent of professional experience of the physicians that participated in the study. Why do health care providers choose to not adhere to the validated clinical decision rules for determining the pretest probability of PE, and does this impact outcomes of care?

Numerous large (randomized) diagnostic outcome studies have demonstrated the benefits of following a standardized algorithm, where a pretest probability and D‑dimer levels guide decisions to order diagnostic imaging in patients with suspected acute PE across several health care settings.^4,5 The benefits of using such algorithms include both the optimal use of health care resources (fewer expensive and time‑consuming imaging tests, shorter emergency room visit times, lower costs, and earlier initiation of anticoagulant therapy), as well as better outcomes for patients, that is, fewer missed venous thromboembolism diagnoses, less potentially irrelevant subsegmental PEs, and lower exposure to ionizing radiation and potentially harmful contrast agents.^4-9 The level of evidence for the use of these algorithms is very high, and international guidelines recommend using them without exception.¹⁰ Making physicians use a dedicated diagnostic algorithm leads to fewer imaging tests ordered and a lower 3‑month diagnostic failure rate, further highlighting the relevance of these recommendations.⁸ The most recently proposed and validated algorithms that involve pretest probability‑dependent D‑dimer thresholds hold promise: more than half of the patients can be managed without imaging tests, which is especially relevant for younger patients and pregnant women.^11-13 So yes, physicians, independent of their experience or setting, should routinely rely on such algorithms for the benefit of their patients. Exceptions of course apply, mostly for patients who present with shock and those who are actively treated with therapeutic doses of anticoagulants. The patients with shock are in critical condition and require ultrafast management decisions, while D‑dimer tests are unreliable in patients on anticoagulation as they may be false‑negative.

Risk stratification of patients with proven PE is another equally relevant issue. Optimal risk stratification allows for immediate initiation of adequate treatment tailored to the patient’s needs. It mostly enables timely initiation of reperfusion therapy and organ support in the most severe PE cases, where diagnostic and therapeutic delay may lead to death.³ The crucial difference from diagnosing PE is that evidence supporting proper risk stratification of PE patients is mostly unavailable. Large epidemiologic studies have undoubtedly demonstrated that patients with compromised hemodynamics or respiratory insufficiency are at the highest risk of dying from PE. For those patients who are hemodynamically stable, markers of right ventricular (RV) overload or dysfunction (either imaging or biomarkers) and markers of poor tissue perfusion (eg, lactate levels) also consistently predict a higher risk of adverse clinical outcome.^2,3 However, management studies that showed benefit of management decisions based on a certain risk classification model are hardly available. For instance, the rationale for systemic thrombolysis in high‑risk PE is based on a single randomized trial that was discontinued early after enrolling only 8 patients.¹⁴ Differentiating hemodynamically stable patients by looking at RV function and biomarkers of myocardial damage makes sense, and does identify patients at higher (intermediate‑high and intermediate‑low risk) or lower risk of hemodynamic collapse and death (low risk).^2,3 However, well‑designed, high‑quality randomized outcome studies with patient‑relevant “hard” outcomes that show without doubt that patients in the intermediate risk categories benefit from a more aggressive treatment than anticoagulation alone are lacking. Circumstantial evidence suggests that especially the intermediate‑high risk category patients may have better outcomes, when they are subjected to safe reperfusion treatment on top of anticoagulation, but “circumstantial” does not count in evidence‑based medicine. For low‑risk patients, either defined by the HESTIA criteria or the simplified Pulmonary Embolism Score Index combined with clinical judgement, with or without the explicit absence of signs of RV overload or dysfunction, strong evidence supports good outcomes of care in the outpatient setting.¹⁵ Ongoing randomized trials with half‑dose thrombolysis or different catheter‑directed strategies will considerably broaden our knowledge of risk stratification and its implications. Until then, the optimal way of risk stratification may be debated and establishing its quality criteria is difficult.

Stępniewski et al¹ touch upon the relevance of echocardiography and multidisciplinary collaboration (the United States PE response team or its European counterpart, EXPERT‑PE) to improve the quality of the initial patient management in acute PE. Indeed, echocardiography is the bedside imaging test of choice to establish RV function in both acute and chronic setting of PE management. However, the current guidelines do not leave room for management decisions based on echocardiography alone, as the hemodynamic profile of the patient informs the risk stratification. Interestingly, the abovementioned ongoing randomized trials focusing on different reperfusion strategies in hemodynamically stable PE patients do not rely on echocardiography for patient selection. The optimal application of echocardiography may thus not so much lie in immediate treatment decisions, but more in early follow‑up after hospitalization to recognize treatment failure (worsening or lack of improvement of cardiac function and / or hemodynamic or respiratory parameters). It is here that EXPERT‑PE teams may have additional value, by standardizing such decisions and application of advanced reperfusion treatment.

The study by Stępniewski et al¹ is an important wake‑up call: there is still work to be done to achieve the level of evidence needed to establish strict risk stratification criteria and related management decisions. We may want to be the best boy or girl in class, but to get there, we must first go back to school.