What is the evidence supporting the use of a coronary sinus excluder (CSEx) in reducing morbidity and mortality?

Evidence Behind the Coronary Sinus Reducer for Refractory Angina

The coronary sinus reducer (CSR) is an effective device for treating refractory angina in patients who are not candidates for revascularization, with significant improvements in angina symptoms and quality of life demonstrated in recent clinical studies. 1

Mechanism of Action and Device Description

• The coronary sinus reducer is a balloon-expandable, stainless-steel device designed for implantation in the coronary sinus that creates a controlled narrowing 2
• It works by increasing coronary sinus pressure, which redistributes blood flow from the less ischemic sub-epicardium to the more ischemic sub-endocardium, potentially alleviating myocardial ischemia 2
• The device may also stimulate neoangiogenesis, contributing to improved myocardial perfusion 2

Clinical Evidence

Efficacy Data

• The REDUCER-I study, a large multicenter observational study of 400 patients with refractory angina, demonstrated that 69.8% of patients improved by at least 1 Canadian Cardiovascular Society (CCS) class at 6 months after CSR implantation 1
• Six-minute walk distances improved by 34.1 ± 85.8 meters at 6 months (p < 0.0001) 1
• Long-term follow-up data shows sustained improvement in angina symptoms and quality of life through 3 years 1
• A separate multicenter study with median follow-up of 3.38 years showed that mean CCS class improved from 3.1 ± 0.5 at baseline to 1.66 ± 0.8 at 1 year (p < 0.001), with benefits maintained at 2 years and last follow-up 3
• The percentage of patients with severe disabling angina (CCS class 3-4) decreased from 91% at baseline to only 17.9% at 1 year (p < 0.001) 3

Safety Profile

• The REDUCER-I study reported a low major adverse cardiac event rate of 1.6% (95% CI: 0.7-3.6) and serious adverse event rate of 1.1% within 30 days 1
• No deaths were reported within 30 days of the procedure 1
• Long-term mortality rates in patients with CSR implantation appear similar to those reported for patients with stable coronary artery disease 3

Limitations and Non-Responders

• Between 15-30% of patients do not respond to coronary sinus reducer therapy 4
• Factors associated with poor response include:
  1. Inappropriate patient selection
  2. Cardiac venous system anatomical heterogeneity
  3. Coronary sinus size variations
  4. Incomplete device endothelialization
  5. Coronary artery disease phenotype and progression
  6. Limited myocardial ischemia at baseline 4

Current Guideline Recommendations

• The European Society of Cardiology included the coronary sinus reducer in their 2019 guidelines for the management of chronic refractory angina 4
• Current guidelines for chronic coronary syndromes emphasize a comprehensive approach to management, including optimal medical therapy with beta-blockers, ACE inhibitors, and statins as first-line treatments 5
• For patients with refractory symptoms despite optimal medical therapy who are not candidates for revascularization, additional treatment options may be considered 5

Clinical Context and Patient Selection

• The CSR is specifically indicated for patients with refractory angina who remain symptomatic despite optimal medical therapy and are not candidates for further revascularization 2, 1
• These patients typically have poor quality of life due to persistent angina symptoms despite maximal medical management 2
• The mortality rate in this population is relatively low, but the condition is associated with high hospitalization rates and significantly reduced exercise capacity 2

Historical Context

• Interest in coronary sinus interventions dates back almost 100 years, with various techniques attempted to improve myocardial perfusion via the coronary venous system 6
• Early techniques included coronary sinus occlusion, retroinfusion, and retroperfusion of arterial blood 6
• Modern percutaneous catheter techniques have allowed for safer and more effective coronary sinus interventions compared to historical approaches 6

In summary, the coronary sinus reducer represents a promising treatment option for patients with refractory angina who have exhausted conventional treatment options. While not mentioned in the most recent American guidelines, European guidelines have recognized its potential role in managing this challenging patient population.