How is coronary no reflow diagnosed in the cath lab?

Diagnosis of Coronary No-Reflow in the Cath Lab

Coronary no-reflow is diagnosed in the cath lab primarily through angiographic assessment of TIMI flow grade and myocardial blush grade, with TIMI flow <3 or TIMI flow 3 with myocardial blush grade 0-1 being the definitive diagnostic criteria, along with <70% ST-segment resolution within 4 hours of the procedure. 1, 2

Primary Diagnostic Criteria

Angiographic Assessment

• TIMI Flow Grade:

  • TIMI 0: No antegrade flow beyond occlusion point
  • TIMI 1: Contrast passes beyond obstruction but "hangs up" and fails to opacify entire coronary bed
  • TIMI 2: Slower contrast entry/clearance compared to normal vessels
  • TIMI 3: Normal antegrade flow and clearance

• Myocardial Blush Grade (MBG):

  • Assesses tissue-level perfusion
  • No-reflow is diagnosed when MBG is 0 or 1 despite TIMI 3 flow 1, 2

Electrocardiographic Assessment

• ST-segment resolution <70% within 4 hours of the procedure despite successful epicardial artery opening 1

Additional Diagnostic Methods in the Cath Lab

Direct Invasive Assessment

• Coronary Flow Velocity Measurement:
  • Using Doppler guidewire
  • Rapid deceleration of diastolic flow velocity indicates no-reflow 1, 3

Timing of Diagnosis

• No-reflow typically develops within the first 2 hours of reperfusion 4
• Incidence ranges from 10-40% of patients undergoing reperfusion therapy for STEMI 1, 2

Clinical Significance and Implications

• No-reflow is associated with:
  • Prolonged myocardial ischemia
  • Severe arrhythmias
  • Critical hemodynamic deterioration
  • Increased risk of clinical complications 1, 2
  • Poor prognosis for LV remodeling and function 2, 5
  • Increased mortality independent of infarct size 5

Differential Considerations

• Differentiate persistent slow flow or no-reflow from competitive flow from remaining collateral channels 1
• TIMI grade 2 flow after CTO-PCI is considered a successful result and should be differentiated from slow reflow with evidence of ongoing ischemia 1

Post-Cath Lab Confirmation

While not part of the initial cath lab diagnosis, these methods can confirm and quantify no-reflow:

• Non-invasive imaging techniques:
  • Contrast echocardiography
  • Single-photon emission tomography
  • Positron emission tomography (PET)
  • Contrast-enhanced magnetic resonance imaging (MRI) 1, 3

Practical Approach to Diagnosis

1. Assess TIMI flow grade immediately after intervention
2. If TIMI flow is <3, diagnose as no-reflow
3. If TIMI flow is 3, assess myocardial blush grade
4. If MBG is 0-1 despite TIMI 3 flow, diagnose as no-reflow
5. Monitor ST-segment resolution within 4 hours of the procedure
6. Consider Doppler guidewire assessment for borderline cases

By following this systematic approach, coronary no-reflow can be promptly diagnosed in the cath lab, allowing for timely intervention with intracoronary vasodilators or other appropriate therapies to potentially improve outcomes 1, 2.