mTICI Reperfusion Target for Mechanical Thrombectomy
The target mTICI reperfusion score should be mTICI 2c/3 (near-complete to complete reperfusion), not the traditional mTICI 2b threshold.
Understanding the mTICI Scale
The modified Thrombolysis in Cerebral Infarction (mTICI) scale measures the extent of tissue reperfusion after mechanical thrombectomy 1:
- mTICI 0: No perfusion
- mTICI 1: Minimal flow past occlusion but no perfusion
- mTICI 2a: Minor partial reperfusion (<50% of territory)
- mTICI 2b: Major partial reperfusion (50-99% of territory)
- mTICI 2c: Near-complete perfusion with slow flow in few distal vessels or small distal emboli
- mTICI 3: Complete reperfusion without flow defects
The mTICI scale uses a threshold of more than half of the target downstream territory for defining major reperfusion, which differs from the original TICI scale that used two-thirds 1.
Why mTICI 2c/3 Should Be the Target
While mTICI ≥2b has traditionally been considered "successful reperfusion," multiple high-quality studies demonstrate that mTICI 2c/3 produces significantly better outcomes than mTICI 2b:
Superior Functional Outcomes
- mTICI 2c/3 patients achieve favorable 90-day outcomes (mRS 0-2) at nearly twice the rate of mTICI 2b patients (62-67% vs 36-37%) 2
- In the ASTER trial, combining mTICI 2c and 3 grades showed significantly higher rates of favorable outcome compared to 2b (OR 1.72,95% CI 1.01-2.90, P=0.043) 3
- A multicenter study found mTICI 3 independently associated with higher odds of 3-month functional independence (OR 2.08,95% CI 1.22-3.53) compared to mTICI 2b 4
Better Neurological Recovery
- mTICI 3 produces greater absolute (11 vs 9 points) and relative (77% vs 63%) reduction in NIHSS scores during hospitalization compared to mTICI 2b 4
- Complete reperfusion (mTICI 3) results in reduced infarct growth compared to mTICI 2b 5
Lower Complication Rates
- mTICI 3 is associated with lower symptomatic intracranial hemorrhage rates (6% vs 12%) compared to mTICI 2b 4
Consistent Across Patient Populations
Even in challenging populations like patients with low ASPECTS (2-5), achieving mTICI 2c/3 provides significantly better 90-day favorable outcomes compared to mTICI 2b (adjusted OR 2.35,95% CI 1.18-4.81, P=0.02) 6.
The First-Pass Effect
Achieving complete reperfusion (mTICI 3) on the first thrombectomy pass is independently associated with favorable outcomes 2. This "true first-pass effect" shows that:
- Favorable outcomes occur almost twice as often with first-pass complete reperfusion (62-67%) versus multiple passes (36-37%)
- Odds for favorable outcome are 2.4-3.2× higher with first-pass mTICI 3 2
Clinical Implications
Operators should not settle for mTICI 2b when further intervention could achieve mTICI 2c/3, provided the risk-benefit ratio remains favorable. However, be aware that:
- 16% of patients show changes in TICI score within 10 minutes after the procedure 7
- Consider repeat angiography at 10 minutes post-procedure to detect early target vessel re-occlusion
- Balance the pursuit of complete reperfusion against procedural time, number of passes, and risk of complications
Practical Algorithm
- Initial goal: Achieve mTICI 2c/3 on first pass
- If mTICI 2b achieved: Assess whether additional passes are safe and feasible to reach mTICI 2c/3
- Consider: Time from symptom onset, number of passes already performed, vessel tortuosity, patient stability
- Verify: Obtain repeat angiography at 10 minutes to confirm sustained reperfusion
- Document: Final mTICI score using the standardized scale 1
The evidence consistently demonstrates that mTICI 2c/3 should be the new standard for successful reperfusion in mechanical thrombectomy 3, 5, 4, replacing the outdated mTICI ≥2b threshold.