What is the incidence of slow reflow or no reflow phenomenon during coronary interventions?

Incidence of Slow Reflow or No Reflow Phenomenon During Coronary Interventions

The no-reflow phenomenon occurs in approximately 10-40% of patients undergoing reperfusion therapy for ST-elevation myocardial infarction (STEMI), with the incidence varying based on the diagnostic technique used. 1, 2

Definition and Diagnosis

• No-reflow is characterized by inadequate myocardial reperfusion despite successful reopening of the epicardial infarct-related artery 2
• Diagnosis is typically made when post-procedural TIMI flow is < 3, or when TIMI flow is 3 but myocardial blush grade (MBG) is 0 or 1 1, 2
• ST-segment resolution within 4 hours of the procedure is < 70% 2
• Diagnostic techniques include:
  • Angiographic grading of flow in the infarct vessel and myocardial blush 1
  • Coronary flow velocity measurement with a Doppler wire 1
  • Non-invasive techniques: ST-segment resolution analysis, contrast echocardiography, single-photon emission tomography, positron emission tomography, and contrast-enhanced MRI 1

Pathophysiology

• Multiple mechanisms contribute to no-reflow:
  • Downstream microvascular embolization of thrombotic or atheromatous debris 1, 2
  • Reperfusion injury 1, 2
  • Microvascular disruption and endothelial dysfunction 2
  • Inflammation and myocardial edema 2
  • Vasospasm 1

Clinical Significance

• No-reflow has serious clinical implications:
  • Prolonged myocardial ischemia 2
  • Severe arrhythmias and critical hemodynamic deterioration 2
  • Significantly increased risk of clinical complications 1, 2
  • Principal clinical sequela is myonecrosis 2
  • Associated with reduced survival rate 1

Incidence in Different Clinical Scenarios

• Primary PCI for STEMI: 10-40% of patients 1, 2
• During elective PCI: Less common but still occurs, particularly during vein graft interventions 3, 4
• In a study of 70 consecutive STEMI patients undergoing primary PCI, 11 patients (15.7%) developed slow/no-reflow phenomenon 5
• In another study, no-reflow was observed in 28.6% of patients who did not receive preventive adenosine treatment versus 5.9% in those who did receive adenosine 6

Prevention and Treatment

• Pharmacological approaches:

  • Intracoronary vasodilators: adenosine (100-1000 μg), verapamil (100-1000 μg), nitroprusside, or papaverine 1, 2, 3
  • GP IIb/IIIa receptor antagonists (abciximab) improve tissue perfusion 1, 2
  • High-dose intravenous adenosine infusion may reduce infarct size 1

• Mechanical approaches:

  • Manual thrombus aspiration during primary PCI can improve tissue perfusion and ST resolution 1, 4
  • Distal protection devices are effective in saphenous vein graft interventions but not in native coronaries 7, 4

• Preventive strategies:

  • Prophylactic intracoronary adenosine before balloon inflation, particularly in vein graft interventions 3, 6
  • GP IIb/IIIa inhibitors are effective in reducing no-reflow during PCI of native coronaries but not during SVG interventions 7

Common Pitfalls and Caveats

• Systemic hypotension can occur with vasodilator therapy, particularly with nitroprusside 2
• Using an intracoronary perfusion catheter when possible can help deliver medications directly to affected areas 2, 3
• No-reflow can be easily missed if only TIMI flow is assessed without evaluating myocardial blush grade or ST-segment resolution 1, 2
• Despite successful epicardial artery opening, microvascular obstruction may persist, requiring specific treatment 1