What is the evidence for External Counterpulsation (ECP) therapy in preventing cardiovascular disease?

Evidence for External Counterpulsation Therapy in Preventing Cardiovascular Disease

External counterpulsation therapy may be considered for relief of refractory angina in patients with stable ischemic heart disease, but there is insufficient evidence supporting its use for primary prevention of cardiovascular disease. 1

Mechanism of Action

Enhanced External Counterpulsation (EECP) is a non-invasive treatment that uses inflatable cuffs wrapped around the lower extremities to:

• Increase venous return and augment diastolic blood pressure
• Sequentially inflate cuffs from calves to thigh muscles during diastole
• Deflate instantaneously during systole

This process creates several physiological effects:

• Increased coronary perfusion pressure
• Decreased peripheral resistance
• Improved left ventricular diastolic filling
• Enhanced peripheral flow-mediated dilation and endothelial function

Proposed mechanisms for symptom improvement include:

• Recruitment of collateral circulation
• Attenuation of oxidative stress and proinflammatory cytokines
• Promotion of angiogenesis and vasculogenesis
• Peripheral training effects similar to exercise 1

FDA Approval and Treatment Protocol

EECP was approved by the FDA in 1995 specifically for treating patients with:

• Coronary artery disease (CAD)
• Refractory angina pectoris
• Failure to respond to standard revascularization procedures and aggressive pharmacotherapy

A standard treatment course consists of:

• 35 one-hour sessions
• 5 days per week for 7 weeks 1

Contraindications

EECP is contraindicated in patients with:

• Decompensated heart failure
• Severe peripheral artery disease
• Severe aortic regurgitation 1

Evidence for Efficacy in Angina

The evidence for EECP in treating angina comes primarily from two randomized controlled trials and several observational studies:

1. MUST-EECP Trial: 139 patients with angina, documented CAD, and exercise-induced ischemia were randomized to active or inactive counterpulsation. Results showed:

   • Significant increase in time to 1-mm ST-segment depression during stress testing (p=0.01)
   • No significant difference in exercise duration, daily nitroglycerin use, or mean frequency of angina
   • 55% of EECP patients reported adverse events (leg/back pain, skin abrasions) vs. 26% in control group 1

2. Smaller RCT: 42 symptomatic CAD patients randomized to EECP or sham treatment showed:

   • Significant improvement in Canadian Cardiovascular Society angina class with EECP compared to control (p<0.001) 1

3. Meta-analysis of 13 observational studies (949 patients):

   • 86% of EECP-treated patients showed improvement by ≥1 Canadian Cardiovascular Society angina class
   • High heterogeneity among studies (p=0.008) reduces confidence in results 1

4. Registry data:

   • EECP Consortium (2,289 patients): Improved perfusion images and increased exercise duration
   • International EECP Registry: 81% of patients showed improvement of ≥1 Canadian Cardiovascular Society angina class 1

Evidence for Cardiovascular Disease Prevention

There is a critical gap in the evidence regarding EECP for primary prevention of cardiovascular disease:

• No randomized controlled trials have evaluated EECP specifically for preventing cardiovascular events in patients without established disease
• Data from RCTs on long-term outcomes are lacking 1
• Most studies focus on symptom relief rather than mortality or cardiovascular event reduction
• The American College of Cardiology/American Heart Association guidelines do not recommend EECP for primary prevention 1

Current Guideline Recommendations

The 2014 ACC/AHA/AATS/PCNA/SCAI/STS Guideline for Stable Ischemic Heart Disease states:

• Class IIb recommendation (may be considered): "EECP may be considered for relief of refractory angina in patients with stable ischemic heart disease" (Level of Evidence: B) 1
• This recommendation is specifically for patients with refractory angina who have failed standard treatments, not for primary prevention

The 2002/2003 ACC/AHA Guidelines similarly classified EECP as:

• Class IIb recommendation (Level of Evidence: B) 1
• To be used only in patients who cannot be managed adequately by medical therapy and who are not candidates for revascularization

Safety Considerations

EECP is generally well-tolerated but has reported adverse events:

• Leg and back pain
• Skin abrasions
• Relative risk of adverse events: 2.13 (95% CI: 1.35 to 3.38) compared to control 1

Conclusion for Clinical Practice

When considering EECP therapy:

1. For established refractory angina: May be considered as a Class IIb recommendation for symptom relief in patients who have failed standard medical therapy and revascularization options

2. For primary prevention of cardiovascular disease: Not currently supported by evidence or guidelines

3. For heart failure patients: Limited evidence suggests potential benefit, but requires further study

The existing evidence base consists primarily of studies examining symptomatic improvement in patients with established coronary artery disease, with a notable absence of data supporting mortality reduction or prevention of cardiovascular events in primary prevention settings.