In this study, approximately 4–15% of OHCA patients met the eligibility criteria for ECPR, depending on the eligibility criteria used. While 20% of all OHCA patients survived to hospital discharge, only 7–14% of OHCA patients eligible for ECPR had survived to hospital discharge. In this study, only 2 (1%) of patients had initiation of ECPR. However, none of the patients who received ECPR had met any established ECPR eligibility criteria. In comparison, approximately 5 to 15 patients per year at this study’s institution would have been eligible to ECPR depending on the eligibility criteria used.
There have been several recent Canadian studies, evaluating the number of patients eligible for ECPR (10, 15, 16). Grunau et al found that 10.2% of OHCA patients presenting to Vancouver EDs were eligible for ECPR (10). In Ottawa, a similar study identified that 6–15% of their OHCA patients were eligible for ECPR (16). A retrospective study conducted in Saskatoon in 2016 found that 14% of non-survivors of OHCA represented suitable candidates for ECPR (9, 15). In New Brunswick, Rollo et al determined that approximately 5 patients annually would be eligible for ECPR at their hospital (18). In Manitoba, Parr et al reported that ECPR was a feasible intervention to support cardiac catherization laboratory patients in cardiac arrest or cardiogenic shock, with favorable 30-day (47%) and 1-year survival (44%) (17).
However, the establishment of ECPR programs must be tempered by proof of efficacy. Various observational studies have demonstrated improved outcomes (increased survival to hospital discharge and favourable neurological outcomes) for cardiac arrest patients who receive ECPR versus traditional resuscitation (9, 10, 19). Yet, a systematic review by Holmberg et al found that the certainty of evidence still remains very low and there was critical risk of bias (20). A recent randomized trial has supported the use of ECPR-assisted resuscitation, but had an overall small sample size (4). Ongoing randomized clinical trials (NCT02832752, NCT03065647, and NCT03101787) may provide higher quality evidence to answer this question.
Despite this, there is significant interest in establishing ECPR programs. In a survey of United States centres that submitted ECPR cases to the Extracorporeal Life Support Registry in 2016, there were 36 centres that had an ECPR program, of which 65% of programs were < 5 years old and 60% of programs had performed ≤ 3 cases per year (21). Newer programs or smaller centres with less ECMO volume or experience may have worse outcomes (22). In this study, four different eligibility criteria, varying in their degree of inclusivity, were evaluated to determine the number of potential annual ECPR cases. The goal of developing ECPR criteria is to balance the development of clinical expertise to optimize outcomes with the sustainability of such a program, taking into account the available resources and personnel (23). Human resources, particularly trained perfusionists or ECMO specialists, remains a large barrier for implementation of ECMO.
Timeliness of ECPR is another important consideration when developing a program. Prior studies demonstrated a median time of initiation of ECPR of one hour (20, 24, 25). However, prolonged low-flow duration (time from initiation of CPR to initiation of ECPR) has been associated with worse neurological outcomes (25). Successful ECPR programs would require the rapid coordination of multidisciplinary teams, including perfusion, cardiothoracic surgery and intensive care, quick identification of eligible patients, and prompt initiation of ECPR (23).
Overall, this study was informative for our institution, demonstrating that there could be many ECPR-eligible patients. At our centre, future study will be necessary on how to implement an ECPR program to improve the outcomes in this group of patients. Balancing local factors and ECMO availability, our institution may favour a restrictive eligibility strategy to allow for buy-in, program development, purchasing of equipment, training, and simulation. Other centres in Canada may adopt a similar strategy and may conduct similar analyses to anticipate ECPR demand. Additionally, further research into economic analyses, including cost-effectiveness and cost-utility, will likely be required before wide adoption of ECPR programs across Canada (6, 23).