What is the meaning of a low threshold for thrombectomy?

Meaning of Low Threshold for Thrombectomy

A "low threshold for thrombectomy" means being more liberal and less restrictive in offering mechanical thrombectomy to stroke patients, extending treatment beyond the narrow eligibility criteria used in randomized trials to include patients who may still benefit despite not meeting all traditional selection parameters.

Core Concept

The phrase reflects a clinical philosophy that prioritizes treatment access over strict adherence to trial enrollment criteria. This approach recognizes that:

• Randomized trials used restrictive eligibility criteria to optimize the chances of demonstrating efficacy, not to define the full population that could benefit 1
• Many organizations translated verbatim restrictive trial criteria into guidelines, which unnecessarily limit thrombectomy to highly selected patients 1
• The decision to offer thrombectomy should be multifactorial with the aim of maximizing patient outcomes, not based on rigid cutoffs alone 2

Clinical Applications of Low Threshold Approach

Special Populations Where Lower Thresholds Apply

Elderly Patients (Age >80 years):

• MT should not be withheld from octogenarians and nonagenarians, but rather evaluated case-by-case 3
• Clinical outcomes improve in elderly patients who receive MT compared to those who do not, despite worse outcomes than younger patients 3
• Age alone should not be an exclusion criterion 3

Low NIHSS Scores (<6):

• The decision should not be based on NIHSS score alone 2
• MT is safe and effective for patients with large vessel occlusions and low initial NIHSS scores 2
• MT was associated with smaller infarct size and decreased mortality even in NIHSS <6 patients 2

Thrombocytopenic Patients:

• MT should not be withheld from thrombocytopenic patients 3
• There is no absolute minimum platelet count that excludes patients from MT given the high morbidity of large vessel occlusion 3
• Platelet counts <20K are concerning, but hematologic consultation is reasonable rather than automatic exclusion 3

Pediatric Patients:

• MT should not be withheld from neonates, infants, children, and adolescents, but evaluated case-by-case 3

Recent Surgery Patients:

• MT should not be withheld from patients who have recently undergone surgery 3

Pregnant Patients:

• Endovascular thrombectomy should be considered for pregnant patients in a similar manner as non-pregnant patients 3
• A low threshold for anesthesia and obstetrics consultation is recommended 3

Extended Time Windows

Beyond 24 Hours (Basilar Artery Occlusion):

• It may be reasonable to consider thrombectomy beyond 24 hours on a case-by-case basis for basilar artery occlusion with NIHSS ≥6 or PC-ASPECTS ≥6 3
• This represents an extremely low threshold given the tremendous uncertainty about benefit in these extended windows 3

COVID-19 Context:

• The presence of COVID-19 should not alter inclusion and exclusion criteria for MT 3
• A low threshold for prophylactic intubation of COVID-19-positive patients prior to transport is recommended 3

Rationale for Lower Thresholds

The Problem with Restrictive Criteria

The cycle of restrictive trial eligibility criteria leading to restrictive guidelines has been repeated often, leaving many stroke patients without validated treatment options 1. The clinical problem becomes: what to do for all other stroke patients equally in need of care? 1

Evidence Supporting Broader Application

• Denial of thrombectomy likely creates a greater drain on healthcare resources given the significant proven benefit for large vessel occlusion 3
• Observational studies consistently show that patients outside narrow trial criteria also benefit from treatment 1

Important Caveats

When Not to Lower the Threshold

Absolute contraindications still exist:

• ASPECTS 0 indicates extensive irreversible brain damage, well below the minimum ASPECTS ≥6 threshold 4
• Absence of perfusion mismatch indicates no salvageable brain tissue 4
• Patients with very low platelet counts (<20K) require careful consideration and hematologic consultation 3

Maintaining Quality Standards

• The technical goal remains reperfusion to mTICI 2b/3 to maximize probability of good functional outcome 3, 5
• Treatment should be performed at experienced stroke centers with immediate access to cerebral angiography and qualified interventionalists 5
• Time still matters: reduced time from symptom onset to reperfusion is highly associated with better clinical outcomes 3

Practical Implementation

A low threshold approach means:

• Evaluating patients individually rather than applying rigid exclusion criteria 3, 2
• Considering thrombectomy when untreated large vessel occlusion would likely result in disabling or fatal outcome 3
• Not automatically excluding patients based on single parameters like age, NIHSS score, or platelet count 3, 2
• Balancing potential benefits against procedural risks in borderline cases 3