What causes a reduction in ejection fraction (EF) after percutaneous coronary intervention (PCI) for Chronic Total Occlusion (CTO)?

Causes of Post-PCI CTO Ejection Fraction Reduction

The primary causes of ejection fraction (EF) reduction after percutaneous coronary intervention (PCI) for chronic total occlusion (CTO) include no-reflow phenomenon, distal embolization, side-branch occlusion, coronary perforation, and periprocedural myocardial infarction.

No-Reflow Phenomenon

No-reflow is one of the most common mechanisms leading to EF reduction after CTO-PCI. It occurs in two distinct forms:

1. Interventional no-reflow: This is attributed to:

   • Vasospasm
   • Downstream embolization of debris dislodged during PCI
   • More common during atherectomy, in the presence of thrombus, or with degenerated saphenous vein grafts 1

2. Suboptimal reperfusion: Characterized by:

   • Endothelial injury
   • Embolization
   • Vasospasm
   • Manifests as abnormal TIMI frame counts and TIMI blush scores 1

The principal clinical consequence of no-reflow is myonecrosis, which can directly impact left ventricular function.

Periprocedural Myocardial Infarction

CTO-PCI carries a higher risk of periprocedural myocardial infarction compared to non-CTO PCI, which can lead to EF reduction:

• Elevated cardiac biomarkers (CK-MB) post-procedure indicate myocardial injury
• Even low-level elevations of CK-MB are associated with increased intermediate and long-term risks 1
• CK-MB index increase of more than 5 times the upper limit of normal should be treated as signifying an MI 1

Procedural Complications

Several procedural complications during CTO-PCI can lead to EF reduction:

1. Coronary Perforation

• Occurs in approximately 6.6% of CTO-PCI cases 2
• Risk factors include:
  • Advanced age
  • Female gender
  • Previous coronary artery bypass graft
  • Blunt stump
  • Proximal cap ambiguity
  • Moderate-severe calcification 2
• Technical success is lower in patients with perforations (69% vs 85%) 2

2. Side-Branch Occlusion

• Occurs in 8% to 80% of unselected patients during bifurcation PCI
• More common with complex bifurcation morphology
• Associated with Q-wave and non-Q-wave MI 1

3. Donor Vessel Injury

• During retrograde approaches, injury to the donor vessel providing collaterals can occur
• Can lead to compromised blood flow to previously viable myocardium 1

Patient-Related Factors

Certain patient characteristics are associated with higher risk of EF reduction after CTO-PCI:

1. Reduced baseline EF: Patients with already reduced EF (≤35%) have higher in-hospital mortality (1.1% vs 0.3% for those with EF ≥50%) 3

2. Comorbidities: Diabetes mellitus, chronic kidney disease, and multi-vessel disease are associated with worse outcomes 4

3. Left main disease: Associated with higher incidence of cardiac death post-procedure 4

Preventive Strategies

To minimize the risk of EF reduction after CTO-PCI:

1. Pharmacological interventions for no-reflow:

   • Intracoronary vasodilators (adenosine, calcium channel blockers, or nitroprusside) are reasonable to treat PCI-related no-reflow (Class IIa recommendation) 1

2. Procedural considerations:

   • Careful patient selection based on viability and ischemia in the CTO territory
   • Provisional side-branch stenting as initial approach in bifurcation lesions (Class I recommendation) 1
   • Elective double stenting for complex bifurcation morphology involving large side branches (Class IIa recommendation) 1

3. Technical expertise:

   • CTO-PCI should be performed by experienced operators within dedicated programs
   • Higher CTO-PCI volume is associated with higher success rates and fewer complications 1
   • Flexibility in changing crossing strategies when initial approach fails 1

Monitoring and Management

1. Post-procedure evaluation:

   • 12-lead ECG before and after PCI, and if symptoms occur
   • Cardiac biomarker measurements in patients with suspected ischemia 1
   • Careful monitoring for angina-like symptoms with ECG changes 1

2. Imaging follow-up:

   • Cardiovascular magnetic resonance (CMR) can help assess improvement in EF and left ventricular volumes after CTO-PCI 5

Clinical Implications

Despite the risks of EF reduction, successful CTO-PCI has been associated with:

1. Improved left ventricular function in patients with heart failure and reduced EF:

   • Decrease in left ventricular end-systolic volume
   • Increase in LVEF (from 31.3% to 37.7%) 5
   • Reduced number of segments showing perfusion defects 5

2. Reduced mortality:

   • Successful CTO recanalization is associated with reduced all-cause mortality in both preserved and reduced LV function groups 6
   • Similar relative risk reductions in both preserved EF (adjusted HR 0.48) and reduced EF groups (adjusted HR 0.63) 6

In conclusion, while there are several mechanisms that can lead to EF reduction after CTO-PCI, successful revascularization generally leads to improved EF and better clinical outcomes when performed by experienced operators with appropriate patient selection.