The Pulmonary Embolism Response Team: Rationale, Operation, and Outcomes

Abstract

The pulmonary embolism response team (PERT) is an institutionally based multidisciplinary team that is able to rapidly assess and provide treatment for patients with acute pulmonary embolism (PE). Intrinsic to the team's structure is a formal mechanism to execute a full range of medical, endovascular, and surgical therapies. In addition, the PERT provides appropriate multidisciplinary follow-up of patients. In the 10 years since the PERT was first introduced, it has gained acceptance in many centers in the United States and around the world. These PERTs have joined together to form an international association, called the PERT Consortium. The mission of this consortium is to advance the diagnosis, treatment, and outcomes of patients with PE. There is considerable evidence that the PERT model improves delivery and standardization of care of PE patients, particularly those patients with massive and submassive PE. However, it is not yet clear whether PERTs improve clinical outcomes. A large prospective database is currently being compiled by the PERT Consortium. Analysis of this database will likely further delineate the role of PERTs in the management of intermediate-to-high risk PE patients and, importantly, help determine in which PE patients PERT may improve clinical outcomes.

Pulmonary embolism (PE) is a clinical problem of enormous magnitude. ¹ It is estimated that, in the United States, up to 100,000 people die as a result of PE each year, ^{2 3} making it the third most common cause of cardiovascular death. ⁴ In addition, there is often an urgency about treating PE, as patients may deteriorate rapidly. ⁵ However, there is considerable variability both between institutions and between individual physicians with regards to treatment strategies, particularly in the case of submassive or massive PE. This variability is due in part to the paucity of robust clinical trials. ^{6 7} Moreover, there are variations in treatment recommendations in clinical guidelines published by societies such as the European Society of Cardiology (ESC), ⁸ the American Heart Association, ⁹ and the American College of Chest Physicians. ¹⁰

Prompted by the above considerations, physicians have, over the past 15 years, attempted to develop more effective and streamlined treatment strategies for PE. In doing so, they have combined lessons learned from several medical systems. The multidisciplinary approach that is central to the working of tumor boards ¹¹ and the Heart Team in cardiology ¹² has been increasingly used in the treatment of PE. Equally, the rapid response team model ¹³ has proved instructive in the prompt and focused delivery of critical care services to PE patients.

All these concepts and aspirations finally became a clinical reality when, in 2012, Dr. Kenneth Rosenfield at Massachusetts General Hospital (MGH) created the pulmonary embolism response team (PERT). ¹⁴ This team comprised physicians across a range of relevant medical specialties who could meet expeditiously as a group and come up with a thoughtful, coordinated, and comprehensive treatment plan for individual PE patients. Soon, other institutions, inspired by the MGH model, began to form their own PERTs and currently there are > 100 institutions in the United States with PERTs. ¹⁵ In 2015, members from over 40 institutions with established or planned PERT programs convened in Boston, Massachusetts and formed the PERT Consortium. ^{15 16} This body was created to advance the diagnosis, treatment, and outcomes of patients with PE throughout the world. ¹⁵

Operation and Structure of the PERT

The PERT is typically activated by a designated 24-hour/ 7-days-a-week telephone number or pager which triggers a prompt evaluation by the on-call clinician or PERT leader ( Fig. 1 ). ^{16 17 18} PERT consultations are most often activated by emergency medicine and intensive care physicians but can also be activated by rapid response teams and floor attendings. In academic centers, the first call generally goes to the PERT fellow (often the on-call cardiology fellow). ¹⁹ The fellow rapidly collects clinical, laboratory, and imaging data and then, working with the attending physician of record, decides whether the case warrants activation of the entire multidisciplinary team.

Fig. 1.

Scheme for the activation of the pulmonary embolism response team. (Used with permission from Rivera-Lebron B, McDaniel M, Ahrar K, et al. Diagnosis, treatment and follow up of acute pulmonary embolism: consensus practice from the PERT consortium. Clin Appl Thromb Hemost 2019;25:1076029619853037.)

In most PERT programs, the multidisciplinary team actively involves 3 to 5 specialties, with some programs involving up to 10 specialties. ^{16 17 18} The wide range of potential specialties in a PERT is shown in Fig. 2 . Barnes et al ¹⁶ performed a survey of members of the PERT Consortium regarding the distribution of specialties in their PERTs. Inclusion of one catheter-based specialty (such as interventional radiology or interventional cardiology) and pulmonary/critical care was generally the rule. Each institution will have a varying profile of subspecialists making up their PERT, based on the experience and resources of the institute. ^{16 17 18 19 20} If it is indeed felt that activation of the multidisciplinary team is warranted, this can be done in several ways. One method is that a page or email is sent to each specialist with a link to a Web-based virtual electronic meeting. ⁶ After the PERT leader has presented the pertinent clinical data, the team can simultaneously view online images such as the chest computed tomography (CT) or echocardiogram.

Fig. 2.

Range of subspecialities that may be part of the pulmonary embolism response team. (Used with permission from Rosovsky R, Zhao K, Sista A, Rivera-Lebron B, Kabrhel C. Pulmonary embolism response teams: purpose, evidence for efficacy, and future research directions. Res Pract Thromb Haemost 2019;3:315–330.)

Alternatively, the process may simply be a conference call between a few clinical specialties. The PERT then needs to formulate recommendations promptly. Key to the success of this multidisciplinary team is the ability of the team to work through disagreement on the best management strategy. ^{16 17 18} Once the PERT comes up with this strategy, they assemble the appropriate resources to execute their recommendations. The latter is a particularly important practical consideration when advanced therapies such as catheter-based or surgical embolectomy are recommended. Then the plan is executed.

The PERT Follow-Up Clinic

The PERT's involvement in the patient's care does not end with administration of acute treatment in the hospital. ¹⁷ Follow-up of patients in outpatient clinic, preferably by one of the specialists on the PERT and, if possible, in a multidisciplinary clinic is important for several reasons. Given the potential for PE to recur following discharge from hospital (8% at 6 months), ⁵ at each visit patients should be monitored for continued resolution of PE symptoms and investigated for new symptoms suggestive of recurrent PE or deep vein thrombosis. The development of persistent or progressive dyspnea, particularly during the first 3 months to 2 years after the diagnosis of PE, should prompt investigation for the development of chronic thromboembolic pulmonary hypertension (CTEPH), a condition that may affect up to 5% of PE patients. ⁵ It is recommended that clinicians should have a low threshold to repeat diagnostic imaging (CT or ventilation perfusions scanning) if recurrence of PE or CTEPH is suspected. ⁵ In some cases, the underlying cause of a patient's PE may not be readily apparent during the initial hospitalization. In such patients, a search, in the follow-up clinic, for an underlying cause, such as a malignancy or inherited coagulation disorder, may be in order. ^{5 17}

The PERT follow-up clinic also provides an opportunity for meticulous monitoring of the post-PE patient's anticoagulation therapy. The clinic pharmacist can check on patient compliance as well as barriers (including insurance issues) to the patient receiving anticoagulation therapy. Ensuring that, in patients on heparin and warfarin, therapeutic levels of anticoagulation are being achieved is another function of the PERT follow-up clinic. The development of conditions that affect the half-life of the anticoagulant used (renal failure, pregnancy, drug interactions, weight gain/loss) should also be followed. ⁵

Patients should be monitored for complications of therapy, including bleeding from anticoagulation, thrombocytopenia, and osteoporosis with heparin, skin necrosis with warfarin, and device migration (with inferior vena cava [IVC] filters).

Outcomes Following Introduction a PERT Program

Several studies have suggested that introduction of a PERT at an institution result in improved PE management by the providers at that institution. ^{21 22 23} Chaudhury et al at Cleveland Clinic performed a retrospective cohort analysis of intermediate-to-high risk acute PE patients presenting during the 18 months before their institution's introduction of a PERT program (in July 2014) and during an 18-month period after introduction of this program. ²¹ A total of 667 patients were identified: 289 in the pre-PERT era, and 378 in the PERT era. Outcomes were better in patients treated in the PERT era as opposed to the pre-PERT era. Specifically, in the former patients, the time to therapeutic anticoagulation was shorter (12.6 vs. 16.3 hours), the rates of major bleeding were less (8.3 vs. 17%), use of IVC filters less (16.1 vs. 24.6%), and 30-day mortality was lower (10 vs. 5.3%). ²¹ At first glance, it would seem that the PERT improves outcomes. However, the PERT was activated and managed care in only a small minority (57 [15%]) of the 378 patients in the PERT era. As noted by Olin, in a recent thoughtful commentary, the better interpretation of this study is that it was not PERT activation that improved outcomes, but rather better education and thus improved management of patients with PE among providers in that institution. ⁷

Rosovsky et al at MGH compared patients being treated for PE at their center prior to introduction of a PERT (2006–2012) and following implementation of their PERT (2012–2016). ²² When compared with patients in the pre-PERT era, patients in the PERT era were more likely to receive catheter-directed therapy (14 vs. 1%) or any advanced therapy (19 vs. 9%). Interrupted time series analysis demonstrated that this increase in use of advanced therapy was sudden and coincided with implementation of PERT. There were, however, no differences between the two groups in mortality or major bleeding. Accordingly, in this study, a PERT program increased the use of advanced therapies, especially catheter-directed therapies for PE patients but was not found to be associated with reduced mortality or major bleeding.

Carroll et al also evaluated their center's experience regarding patients being treated for PE before and after introduction of a PERT. ²³ Similar to Chaudhury et al's experience, only a small minority of their patients (14.2%) in the PERT era was actually evaluated by the PERT. Carroll et al reported increased risk stratification (by cardiac biomarkers and echocardiography) following implementation of their PERT program as well as an increase in catheter-directed therapy. However, there was no difference in PE-related mortality between the two time periods.

Accordingly, while having a PERT in an institution is associated with improved delivery of care, it is still not clear if activation of a PERT results in improved clinical outcomes.

Future Directions

In the 10 years since it was first introduced, the PERT model has gained acceptance in many institutions throughout the world. Indeed, the ESC in their consideration of treatment strategies for PE, have given the PERT model a class IIA (level of evidence C) recommendation. ⁸ There is an abundance of evidence that the PERT model results in improved delivery and standardization of care. Less clear is whether PERT improves patient outcomes. The PERT Consortium is playing a key role in answering the latter question. This body has, over the last few years, prospectively entered data on > 4,000 patients from 30 sites across the U.S. ²⁴ The acquired data will likely further delineate the role of PERTs in the management of intermediate-to-high risk PE patients and, importantly, help determine in which PE patients PERT may improve clinical outcomes.

The considerable planning and organization associated with implementation of an effective PERT program may seem formidable to an institution contemplating such a step. Here also the PERT Consortium has proven to be a valuable resource. The consortium has recently developed the initiative, PERT partners, which is a comprehensive program designed to help institutions construct and implement a PERT. ¹⁸