What is Enhanced External Counterpulsation (EECP)?

What is Enhanced External Counterpulsation (EECP)?

EECP is an FDA-approved, noninvasive outpatient therapy that uses sequential inflation of leg cuffs during diastole to increase coronary perfusion pressure and reduce cardiac afterload, specifically indicated for patients with coronary artery disease and refractory angina who have failed standard revascularization and aggressive medical therapy. 1

Mechanism of Action

EECP employs inflatable cuffs wrapped around the lower extremities that inflate sequentially from calves to thighs during diastole and deflate instantaneously during systole. 1 This produces several hemodynamic effects:

• Diastolic augmentation increases coronary perfusion pressure by raising diastolic aortic pressure 1
• Systolic unloading decreases peripheral resistance and afterload 1
• Enhanced venous return improves left ventricular diastolic filling and cardiac output 2

The acute hemodynamic effect mimics that of an intra-aortic balloon pump but is completely noninvasive. 2

Proposed Long-Term Mechanisms

Beyond acute hemodynamics, EECP may provide sustained benefit through: 1

• Recruitment and development of coronary collaterals
• Promotion of angiogenesis and vasculogenesis
• Improved peripheral flow-mediated dilation and endothelial function
• Attenuation of oxidative stress and proinflammatory cytokines
• Peripheral conditioning effects

Treatment Protocol

A standard EECP course consists of 35 one-hour sessions administered 5 days per week over 7 weeks. 1, 2

FDA Approval and Indications

EECP received FDA approval in 1995 specifically for patients with CAD and refractory angina pectoris who fail to respond to standard revascularization procedures and aggressive pharmacotherapy. 1

Contraindications

Absolute contraindications include: 1

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

Clinical Evidence and Efficacy

Randomized Controlled Trial Data

The MUST-EECP trial (139 patients) demonstrated that active EECP significantly increased time to 1-mm ST-segment depression on stress testing (337±18s to 379±18s) compared to sham treatment (326±21s to 330±20s; p=0.01). 1 However, groups did not differ in exercise duration, daily nitroglycerin use, or mean angina frequency. 1

A smaller RCT (42 patients) showed significant improvement in Canadian Cardiovascular Society (CCS) angina class with EECP (3.16±0.47 to 1.20±0.40) versus no change with sham control (2.93±0.26 to 2.93±0.26; p<0.001). 1

Observational Registry Data

A meta-analysis of 13 observational studies (949 patients) found that 86% of EECP-treated patients improved by ≥1 CCS angina class (95% CI: 82-90%), though significant heterogeneity among studies limits confidence in these results. 1

The International EECP Registry reported 81% of patients improved ≥1 CCS class immediately after treatment. 1 Long-term follow-up studies show sustained benefit, with 55% maintaining angina reduction at 2 years. 1

Special Populations

In patients with left ventricular dysfunction (EF ≤35%): 72% improved from severe angina to no or mild angina after EECP, with 52% discontinuing nitroglycerin use. 3 At 2-year follow-up, the survival rate was 83% and major adverse cardiovascular event-free survival was 70%. 3

In post-CABG patients with ischemic cardiomyopathy: EECP combined with medical therapy produced significant improvement in CCS class (p=0.005) and NYHA class (p=0.002) compared to medical therapy alone. 4

Adverse Events

Common adverse events occur in approximately 55% of patients (versus 26% with sham treatment; RR 2.13,95% CI 1.35-3.38), with about half being device-related. 1 These include:

• Leg and back pain
• Skin abrasions

The treatment is generally well tolerated with a low risk of serious adverse events. 2, 5

Current Guideline Recommendations

The 2014 ACC/AHA guidelines assign EECP a Class IIb recommendation (Level of Evidence B) for relief of refractory angina in patients with stable ischemic heart disease. 1 This means EECP may be considered when other options have been exhausted.

Critical Limitations

Data from RCTs on long-term outcomes are lacking. 1 The writing committee notes that while existing data from largely uncontrolled studies suggest benefit, additional well-designed RCTs are needed to better define EECP's role in stable ischemic heart disease. 1

Approximately 20% of patients require repeat EECP treatment, with failure to complete the initial treatment course being the strongest predictor (HR 2.9,95% CI 1.7-4.9). 3

Clinical Application Algorithm

Consider EECP when:

1. Patient has documented CAD with refractory angina (CCS class III-IV preferred based on evidence) 5
2. Standard revascularization has failed or is not feasible 1
3. Aggressive pharmacotherapy has been maximized 1
4. No contraindications exist (decompensated HF, severe PAD, severe AR) 1
5. Patient can commit to 35 sessions over 7 weeks 1

Do not use EECP in patients with CCS class II angina, as evidence shows no significant benefit in this population. 5