Despite advances in trial design, digital health and patient engagement, recruitment remains one of the most critical bottlenecks in cardiovascular clinical trials, and many studies struggle to meet enrolment targets in a timely manner.
Cardiovascular diseases (CVD) are among the leading causes of death worldwide. Therefore, efficient and representative clinical trials are essential for developing safe and effective therapies. However, recruitment in this field presents unique operational, clinical and regulatory challenges (1, 2).
This issue is particularly evident in stroke research. Acute stroke trials are subject to extreme time constraints, require rapid decision-making and frequently involve vulnerable patient groups. The well-established concept that “time is brain” highlights the urgency of treatment and, consequently, the difficulty of conducting clinical research in this setting (3). This article outlines the key recruitment challenges in cardiovascular trials, with a focus on stroke studies.
The Recruitment Challenge in Cardiovascular Trials
Recruitment challenges in cardiovascular trials are multifactorial and often interconnected (1, 2).
Narrow time windows in acute stroke:
Stroke trials often require enrolment within hours of symptom onset. This severely limits the time available for identifying patients, assessing eligibility and obtaining informed consent. Treatment effects in acute stroke are highly time-dependent, further increasing the pressure on recruitment processes (3, 4).
Complex eligibility criteria:
Cardiovascular trials frequently require highly specific patient populations (e.g. defined ejection fraction ranges, imaging findings, stroke severity scores and comorbidities). Consequently, many patients are screened but not enrolled.
Consent in emergency situations:
Stroke patients may be cognitively impaired or unconscious. Therefore, obtaining informed consent from legal representatives within a short timeframe can be a major operational challenge.
Competing studies and limited patient pools:
Patients with cardiovascular conditions are often eligible for multiple trials simultaneously. This creates competition between sponsors and sites, particularly at large academic centres (2).
Elderly and multimorbid populations:
Many cardiovascular patients are elderly and have multiple comorbidities. This can increase exclusion rates, complicate consent procedures, and raise safety concerns.
Site burden and operational constraints:
Stroke or myocardial infarction care is highly time sensitive. Clinical teams prioritise acute treatment, which can limit the resources available for research activities.
Why Patient Recruitment is Critical in Cardiovascular Research
Risk of underpowered studies:
Failure to reach recruitment targets can compromise statistical power and restrict how results can be interpreted (1).
Limited representation of real-world patients:
Strict eligibility criteria and operational barriers may exclude elderly or multimorbid patients, reducing generalisability.
Delays in innovation:
Recruitment inefficiencies delay access to improved stroke treatments, including acute interventions and rehabilitation strategies.
Strategies to Improve Recruitment
Addressing recruitment challenges requires a combination of strategic planning and condition-specific adaptations.
Feasibility based on real-world pathways:
Feasibility assessments should reflect actual patient flow in stroke or coronary care units, including emergency department processes and imaging timelines. Data from registries and trial networks can support realistic planning.
Streamlined eligibility criteria:
Where clinically justified, simplifying inclusion and exclusion criteria can improve enrolment without compromising scientific validity.
Integration into clinical workflows:
Trials should be embedded into routine stroke or myocardial infarction pathways (e.g. during imaging or thrombolysis decision-making) to minimise delays.
Use of digital and pre-screening tools:
Electronic health records and automated alerts can help identify eligible patients in real time.
Strong site selection and training:
Selecting experienced stroke centres with established research infrastructure is essential. Continuous training ensures that staff can act quickly and efficiently.
Practical Approaches to Increase Enrolment in Acute Stroke Studies
In addition to strategic measures, the following operational practices can significantly improve recruitment (1):
Prepare emergency consent procedures:
Predefined processes for proxy consent or deferred consent can help to overcome time constraints.
Implement 24/7 screening capability:
Stroke can occur at any time. Therefore, round-the-clock screening and on-call research staff are critical for maximising enrolment.
Use rapid communication tools:
Clear escalation pathways (e.g. alerts to study teams) reduce delays in patient identification and enrolment.
Collaborate with referral networks:
Partnerships with smaller hospitals and emergency services can expand the recruitment pool and enable earlier patient identification.
Monitor recruitment performance in real time:
Dashboards and KPIs allow early identification of bottlenecks and enable targeted interventions.
Conclusion: Improving Recruitment to Advance Cardiovascular and Stroke Care
Recruitment to cardiovascular trials, particularly stroke research, remains complex and resource intensive. However, effective recruitment is also essential for improving trial efficiency and accelerating innovation.
Realistic feasibility planning, streamlined protocols, integration into clinical workflows and strong site engagement can significantly improve recruitment performance.
Optimising recruitment is ultimately essential not only for the success of studies, but also for advancing stroke care and ensuring that patients benefit from new therapies as early as possible.
References
- Bower, P., Brueton, V., Gamble, C., et al. (2014).
Interventions to improve recruitment and retention in clinical trials. Trials, 15, 399. https://doi.org/10.1186/1745-6215-15-399 - McDonald, A. M., Knight, R. C., Campbell, M. K., et al. (2006).
What influences recruitment to randomised controlled trials? Trials, 7, 9. https://doi.org/10.1186/1745-6215-7-9 - Saver, J. L. (2006).
Time is brain—quantified. Stroke, 37(1), 263–266. https://doi.org/10.1161/01.STR.0000196957.55928.ab - Emberson, J., Lees, K. R., Lyden, P., et al. (2014).
Effect of treatment delay, age, and stroke severity on the effects of intravenous thrombolysis with alteplase. The Lancet. https://doi.org/10.1016/S0140-6736(14)60584-5
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