Submassive

Submassive is a clinical term used primarily in the context of acute pulmonary embolism to describe an intermediate level of severity between nonmassive (low risk) and massive (high risk) PE. It refers to patients who are hemodynamically stable, without sustained hypotension or shock, but who have signs that indicate a higher risk of adverse outcome, such as right ventricular dysfunction or myocardial injury.

In practice, submassive pulmonary embolism is characterized by evidence of right heart strain or injury despite normal blood pressure. Diagnostic indicators may include imaging findings of right ventricular enlargement or dysfunction on echocardiography or CT, and biomarker evidence such as elevated troponin or natriuretic peptides. Definitions and criteria vary across guidelines; some require both imaging evidence of RV dysfunction and positive cardiac biomarkers, while others rely on a broader combination of findings.

Prognostically, submassive PE carries a higher risk of early deterioration and death than nonmassive PE but lower risk than massive PE. Risk stratification using clinical, imaging, and laboratory data guides decisions about management and monitoring, including the level of surveillance needed in a hospital setting and whether to escalate therapy.

Management generally begins with anticoagulation, typically with heparin. Systemic thrombolysis is not routinely used for submassive PE due to bleeding risk, but may be considered in selected patients at high risk of deterioration. Alternatives include catheter-directed thrombolysis or surgical embolectomy in cases where systemic thrombolysis is contraindicated or unlikely to succeed. The term “submassive” is variably defined and increasingly supplemented or replaced by explicit intermediate-risk descriptors in contemporary guidelines.