Yuki Agarwala; Anushka Gupta; Han Kim; Harit Phowatthanasathian; Adriana Ramos Calvo; Jenny Tang; Annie Szeto

What is a PE and why is it complex to treat?

A pulmonary embolism (PE) is a blood clot, or thrombosis, that blocks a pulmonary artery and limits blood flow.¹ A combination of physiological changes accompany a PE, starting with increased pulmonary artery pressure.² Sudden elevation in pulmonary pressure contributes to the ‘backflow’ of blood into the right side of the heart, creating a pressure imbalance that can lead to decreased cardiac output and heart failure.²

When left untreated, PE can cause a patient’s condition to worsen considerably, even leading to death.

PE is the third most prevalent cause of cardiovascular mortality in the United States, accounting for more than 600,000 deaths every year.³ Furthermore, PE has become more common in younger age groups (25-64 years) due to changes in patient-associated risk factors, such as obesity and stress.⁴

A key challenge is the diversity in PE presentation. For example, some patients have asymptomatic PE that is only incidentally discovered – whilst others have more serious cases of PE that result in sudden death. This variability is challenging for initial diagnosis, but also subsequent treatment decisions. With an array of emerging strategies for PE treatment, deciding on an appropriate therapeutic approach is complex.

What is a PERT?

Seeking to address this complexity, clinicians developed the first Pulmonary Embolism Response Team (PERT) at Massachusetts General Hospital in 2012, to develop educational, research, and clinical infrastructure to advance treatment for PE patients.⁵ A PERT is a group of multiple different specialists, usually in fields such as cardiovascular medicine and surgery, emergency medicine, hematology, pulmonary and critical care, and radiology, all working together to care for PE patients.⁵ The protocol to activate a PERT is a relatively sequential process. First, a clinician who diagnoses a PE calls the hospital’s central call service and activates the PERT. Next, an on-call clinician gathers information about the patient. After collecting the clinical information about the patient, the on-call clinician shares the information with other PERT members who meet (often virtually) to evaluate the case and create a plan of action for the referring clinician. As such, the PERT approach provides a framework to utilize expertise across medical fields. The principle behind this protocol is simple: variability in PE presentation should be tackled with a collaborative and diverse clinical response. In theory, PERT implementation supports decision-making and will improve outcomes, particularly for high-risk PE patients.

By establishing a balanced, inter-disciplinary team with defined response protocols, PE treatment is provided in a structured, efficient, and informed manner. The PERT paradigm has since been implemented by various centers on a global scale to deliver integrated care to PE patients.⁶

PERT in action:

In a 2016 paper reporting the first 30 months of PERT activations at Massachusetts General Hospital (MGH), 80% of patients were intermediate to high risk. ⁷ Most of those patients received anticoagulation treatment (69%) and a smaller percentage of patients received systemic or catheter-directed thrombolysis (11%). When comparing PERT patients that underwent catheter-directed thrombolysis to anticoagulation treatments, the same rate of major bleeding in 30 days was found in each group (4% each), lower than studies of systemic intravenous thrombolysis published before PERTs were formed.⁷ The creation of a PERT led to a greater proportion of patients having advanced therapies and treatments.^8-9 After treatment, the 30-day mortality rate of massive PE patients was 25%, substantially lower than the 52% reported in the International Cooperative Pulmonary Embolism Registry (ICOPER). Thus, this initial report suggested that a PERT increased the efficiency and effectiveness of treatment, especially for high-risk patients. Interestingly, 20% of the patients treated by the MGH PERT were reported to have low risk PE, and low risk PE had a higher 30-day mortality rate (12.2%) than submassive PE patients (2.6%).⁷ While this was not the target population for PERT, subsequent analysis of why these patients gets activated for PERT showed that other high-risk features (like recent surgery), apart from their PE, led to their PERT activation.¹⁰ Therefore, due to their efficient multidisciplinary approach, PERTs may benefit both high-risk and low-risk patients’ diagnostic testing and management.

Recent studies have continued to support the implementation of PERTs. The efficacy of PERTs has been demonstrated in centers across the United States: key outcomes improved by PERTs include mortality, as well as hospital and ICU length of stay.^8,11 These benefits may be linked to PERT’s ability to facilitate expedient decision-making and improved access to advanced therapies.¹² Nevertheless, further research into how PERTs can reduce mortality and lower the risk of adverse patient outcomes is indicated to fully characterize the impact of PERT implementation.^13-14

Next steps:

Since PERTs allow clinicians to decide treatment plans in a team-based manner, their global implementation as the standard of care helps optimize high-risk patients’ care, putting multiple professionals’ expertise at the patient’s disposal.^15,16 There is also a positive feedback loop between the development of the PERT concept and the amount of data generated regarding patient outcomes. This will allow for PERTs to improve their performance in an evidence-based manner to reduce mortality and increase acute PE sufferers’ quality of life.¹⁵ Additional patient data can solve the questions that remain unanswered, including if this approach is cost-effective, can have a positive impact on clinical care, improve PE outcomes, and lead to a more effective PE treatment.¹⁷

The PERT Consortium, a non-profit organization founded in 2016, aims to promote the multidisciplinary care of PE patients and shape future research. It comprises over 150 institutions and 1,500 clinicians in the United States and globally.¹⁸ The PERT Consortium works to promote the PERT model of diagnosis and treatment, encourage research into PE, and educate the public and healthcare workers on the topic of PE.⁷

References:

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