Prior revascularization increases the effectiveness of enhanced external counterpulsation

The role of enhanced external counter pulsation therapy in clinical practice

Enhanced external counterpulsation (EECP) has been approved by the United States Food and Drug Administration (FDA) for management of refractory angina (Class IIb). EECP uses three sets of pneumatic cuffs that sequentially contract during diastole, increasing aortic diastolic pressure, augmenting coronary blood flow and central venous return. EECP improves anginal symptoms and exercise tolerance, and reduces nitroglycerin use in patients with chronic, stable angina. EECP has also been shown to be safe and beneficial in patients with symptomatic stable congestive heart failure. It has been postulated that cardiac benefits of EECP are mediated though vascular endothelial growth factor (VEGF) and nitric oxide mediated vasodilatation and angiogenesis. In June 2002, the FDA also approved EECP therapy for heart failure patients.

Vasculoprotective properties of enhanced external counterpulsation for coronary artery disease: beyond the hemodynamics

A growing pool of evidence has shown that enhanced external counterpulsation (EECP) is a non-invasive, safe, low-cost, and highly beneficial therapy for patients with coronary artery disease. However, the exact mechanisms of benefit exerted by EECP therapy remain only partially understood. The favorable hemodynamic effects of EECP were previously considered as the primary mechanism of action. Nevertheless, recent advances have shed light on the shear stress-increasing effects of EECP which are vasculoprotective and anti-atherosclerotic. EECP-induced endothelial shear stress increase may lead to improvement in endothelial function and morphology, attenuation of oxidative stress and inflammation, and promotion of angiogenesis and vasculogenesis. This review summarizes evidence of the potential mechanisms contributing to the immediate and long-term benefits of EECP, from the perspective of its shear stress-increasing effects.

Enhanced external counterpulsation: an innovative physical therapy for refractory angina

The prevalence of refractory angina in the United States is 600,000 to 1.8 million. Improved pharmacological, invasive, and surgical therapies for cardiovascular diseases during the last few decades have led to an increase in life expectancy of such individuals. Despite treatment with multiple medications and invasive procedures, these patients remain symptomatic and functionally limited. Enhanced external counterpulsation (EECP) is a safe, noninvasive, well-tolerated, and clinically effective outpatient physical therapy for many patients with refractory angina. Numerous trials demonstrate positive clinical responses among at least 80% of patients undergoing EECP, including reductions in angina and nitrate use, increases in exercise tolerance, and enhanced quality of life. Several mechanisms, including the promotion of collateral blood flow, improvement in endothelial function, reduction in inflammation, and the production of peripheral training effects similar to exercise, are thought to be responsible for the clinical benefits of this therapy. Despite the marked success rates EECP achieves with appropriately selected patients who have end-stage coronary artery disease, the treatment remains largely unknown, particularly among physiatrists. This review will summarize the current evidence for the use of EECP and spark a better understanding of the potential role of this treatment in cardiac rehabilitation.

Long-term prognosis of patients with angina treated with enhanced external counterpulsation: five-year follow-up study

BACKGROUND

Enhanced external counterpulsation (EECP) is a noninvasive treatment for coronary artery disease (CAD) that has been used successfully in patients not responding to medical and/or surgical therapy.

HYPOTHESIS

The study was undertaken to evaluate the effect of EECP on long-term prognosis in such patients.

METHODS

Major adverse cardiovascular events (MACE) were tracked in 33 patients with CAD treated with EECP. Patients were subgrouped based on whether or not they demonstrated an early improvement in radionuclide stress perfusion imaging (Responders vs. Nonresponders) and followed for MACE over a mean follow-up of 5 years. Patient population characteristics included 73% with multivessel disease; 45% with prior myocardial infarction(s); and 61% who had undergone either coronary artery bypass grafting (CABG) or percutaneous transluminal coronary angioplasty (PTCA), or both.

RESULTS

There were 26 of 33 (79%) Responders, and 7 of 33 (21%) Nonresponders. Subsequent MACE over the 5-year follow-up included four deaths and eight patients with cardiovascular events [acute myocardial infarct (4), new CABG or PTCA (6), valve replacement (1), unstable angina (1)]. Nonresponders had significantly (p < 0.01) more MACE (6/7 or 86%) than Responders (6/26 or 23%). Overall, 21 of the 33 (64%) patients remained alive and without MACE and the need for revascularization 5 years post EECP treatment.

CONCLUSION

This study suggests that, particularly for the majority of patients demonstrating improvement in radionuclide stress perfusion post treatment, EECP may be an effective long-term therapy.

Passive tobacco exposure may impair symptomatic improvement in patients with chronic angina undergoing enhanced external counterpulsation

Background

The adverse effects of tobacco abuse on cardiovascular outcomes are well-known. However, the impact of passive smoke exposure on angina status and therapeutic response is less well-established. We examined the impact of second-hand smoke (SHS) exposure on symptomatic improvement in patients with chronic ischemic coronary disease undergoing enhanced external counterpulsation (EECP).

Methods

This observational study included 1,026 non-smokers (108 exposed and 918 not-exposed to SHS) from the Second International EECP Patient Registry. We also assessed angina response in 363 current smokers. Patient demographics, symptomatic improvement and quality of life assessment were determined by self-report prior and after EECP treatment.

Results

Non-smoking SHS subjects had a lower prevalence of prior revascularization (85% vs 90%), and had an increased prevalence of stroke (13% vs 7%) and prior smoking (72% vs 61%; all p < 0.05) compared to non-smokers without SHS exposure. Despite comparable degrees of coronary disease, baseline angina class, medical regimens and side effects during EECP, fewer SHS non-smokers completed a full 35-hour treatment course (77% vs 85%, p = 0.020) compared to non-smokers without SHS. Compared to non-smokers without SHS, non-smoking SHS subjects had less angina relief after EECP (angina class decreased ≥ 1 class: 68% vs 79%; p = 0.0082), both higher than that achieved in current smokers (66%). By multivariable logistic regression, SHS exposure was an independent predictor of failure to symptomatic improvement after EECP among non-smokers (OR 1.81, 95% confidence intervals 1.16–2.83).

Conclusion

Non-smokers with SHS exposure had an attenuated improvement in anginal symptoms compared to those without SHS following EECP.

The role of enhanced external counterpulsation in the treatment of angina and heart failure

As the incidence of angina and heart failure continue to rise, new therapeutic options will be needed to treat patients who remain symptomatic or who are intolerant to current treatment. Enhanced external counterpulsation (EECP) is a noninvasive modality being investigated in both angina and congestive heart failure patients. It has been proven to provide symptomatic benefit in angina patients, but has not been proven to show an increase in life expectancy or decrease in cardiovascular events. EECP in heart failure has been proven to be safe, but its efficacy is still uncertain. The present paper summarizes the current literature on the clinical use of EECP in angina and heart failure.

Enhanced external counterpulsation for the treatment of angina pectoris

The treatment of refractory chronic angina pectoris presents an increasing problem for all physicians caring for patients with coronary artery disease because of the large number of individuals who have either failed multiple revascularization procedures or are not appropriate candidates for such procedures. The aim of this study was to review the safety, efficacy, and clinical applicability of a noninvasive technique (external counterpulsation) for the treatment of angina pectoris. A MEDLINE search for all English language abstracts, meeting presentations, journal articles, and reviews from 1960 through December 2005 was conducted. Of the 194 citations in the literature, 60 appeared before 1983 when the enhanced version of the technique (the one that is presently used) was first reported. Criteria for further evaluation of the 134 post-1983 citations were either (1) randomized trial, (2) observational study of at least 10 patients, or (3) investigations into possible mechanisms. Of the 134 citations, 45 were used for data extraction. Observational studies from the United States, Asia, and Europe have demonstrated improvement in symptoms, reduction in anginal episodes, better quality of life, and improved exercise performance in over 5000 patients. The only randomized study (Multicenter Study of Enhanced External Counterpulsation) confirmed these findings as well as the continuation of clinical benefits at least 1 year posttreatment. Although the mechanisms by which diastolic augmentation achieves these beneficial results are still under investigation, this is a promising noninvasive therapy in a group of patients with limited treatment options.

Evolving treatment strategies for chronic refractory angina

Chronic refractory angina is a term used to describe patients who, despite optimal medical therapy, have both angina and objective evidence of ischaemia. It is estimated that 5-15% of the 12 million patients with chronic angina in the US meet the criteria for having refractory angina. This review focuses on the following evolving pharmacological therapies for chronic refractory angina: L-arginine, ivabradine, ranolazine, nicorandil and trimetazidine. Evolving devices and invasive procedures including enhanced external counterpulsation, spinal cord stimulation, and transmyocardial revascularisation are also briefly discussed.

Angiogenic effects of long-term enhanced external counterpulsation in a dog model of myocardial infarction

Enhanced external counterpulsation (EECP) is an effective noninvasive treatment of coronary artery disease. Its mechanism of action remains unknown. An acute coronary occlusion dog model was created to explore the angiogenic effect of EECP. After coronary occlusion, 12 dogs were randomly assigned to either EECP ( n = 6) or control ( n = 6). Immunohistochemical studies of α-actin and von Willebrand factor (vWF) were used to detect newly developed microvessels. Systemic and local vascular endothelial growth factor (VEGF) were identified by ELISA and reverse transcriptase PCR analysis. There was a significant increase in the density of microvessels per squared millimeter in the infarcted regions of the EECP group compared with the control group (vWF, 15.2 ± 6.3 vs. 4.9 ± 2.1, P < 0.05; α-actin, 11.8 ± 5.3 vs. 3.4 ± 1.2, P < 0.05). The positive-stained area per squared micrometer also increased significantly (α-actin, 6.6 × 103 ± 2.9 × 103 μm2 vs. 0.6 × 103 ± 0.5 × 103 μm2, P < 0.05; vWF, 5.7 × 103 ± 1.9 × 103 μm2 vs. 1.7 × 103 ± 1.4 × 103 μm2, P < 0.05). Immunohistochemical staining and reverse transcriptase PCR analysis documented a significant increase in VEGF expression. These factors associated with angiogenesis corresponded to improved myocardial perfusion by 99mTc-sestamibi single-photon emission computed tomography. Angiogenesis may be a mechanism of action for the improved myocardial perfusion demonstrated after EECP therapy.

Predictors of benefit in angina patients one year after completing enhanced external counterpulsation: initial responders to treatment versus nonresponders

Enhanced external counterpulsation (EECP) has been shown to reduce Canadian Cardiovascular Society angina class. This study examines the factors that affect the reduction at 1 year, especially in patients who do not demonstrate an initial response. The data of 2,007 consecutive patients enrolled in the International EECP Patient Registry were analyzed. After 36.6 +/- 4.9 h of EECP, angina was reduced by at least one class in 82.7%. At 1 year, 35.4% of initial nonresponders and 70.6% of responders remained improved by at least one angina class and free of major adverse cardiovascular events. Multivariate predictors of 1-year benefit are initial response to treatment (odds ratio 4.5, 95% CI 3.5-5.8), baseline angina class compared with class IV (odds ratios: class I 2.1, CI 0.93-4.81; class II 0.62, CI 0.43-0.87; class III 0.80, CI 0.62-1.01) and no history of congestive heart failure (odds ratio 1.41, CI 1.14-1.74).

Effects of enhanced external counterpulsation on hemodynamics and its mechanism

BACKGROUND

The hemodynamic effects of enhanced external counterpulsation (EECP) and its mechanism(s) were investigated in relation to neurohumoral factors in patients with acute myocardial infarction (AMI).

METHODS AND RESULTS

Twenty-four patients with AMI were studied before, during and after EECP treatment for 60 min. Heart rate (HR), right atrial pressure (RAP), pulmonary capillary wedge pressure (PCWP) and cardiac index (CI) were determined. In addition, circulating concentrations of neurohumoral factors were determined at each time point. HR did not change following EECP treatment. However, RAP and PCWP increased significantly and CI was significantly elevated during EECP and thereafter. Blood atrial natriuretic peptide (ANP) concentration was significantly increased 15 and 60 min after the start of EECP treatment, but brain natriuretic peptide (BNP) did not change. Renin, aldosterone and catecholamine concentrations also did not change.

CONCLUSION

Treatment with EECP resulted in an increased preload because of increased venous return, and CI was increased thereafter. In patients with AMI, EECP increased blood ANP concentration, but not BNP, which suggests that an increase in ANP without an increase in BNP is an important mechanism for the effects of EECP treatment.

Effectiveness of enhanced external counterpulsation in patients with left main disease and angina

BACKGROUND

Enhanced external counterpulsation (EECP) is a noninvasive device that uses three pairs of sequentially inflated pneumatic cuffs applied to the lower extremities and synchronized with the heart beat to provide diastolic augmentation, increase coronary blood pressure and flow, venous return and cardiac output, and decrease afterload.

HYPOTHESIS

This study examines the safety and effectiveness of EECP therapy in patients with significant left main coronary artery disease (LMD).

METHODS

In all, 2,861 patients enrolled in the International EECP Patient Registry (IEPR) were divided into three groups, those without LMD (n = 2,377), those with LMD and prior CABG (n = 431), and those with unbypassed LMD (n = 53).

RESULTS

Patients with LMD, with or without prior CABG, were significantly more likely to have triple-vessel disease (98.1 and 88.7%, respectively) than patients without LMD (41.9%). Post-EECP, 74% without LMD, 75% with LMD with prior CABG, and 65% with unbypassed LMD improved their Canadian Cardiovascular Society (CCS) angina by at least one class (p = NS). There were no differences in the mean decrease in weekly angina episodes (7.1 vs. 8.0 vs. 7.6) and in the mean frequency of weekly nitroglycerin use (6.6 vs. 8.1 vs. 8.9). At 6-month follow-up, the CCS class improved further in all three groups, and there was a further reduction in mean weekly angina episodes (4.7 vs. 4.6 vs. 5.3) and nitroglycerin use (6.5 vs. 6.8 vs. 8.2). Kaplan-Meier life table analysis 8 months after starting EECP demonstrated a major cardiovascular event rate of 11.2% in patients without LMD, 15.6% in LMD with CABG, and 24.3% in LMD without prior CABG. Late mortality in unbypassed LMD was 13.2% (confidence interval [CI] 3.3-23.1) versus 4.8% (CI 2.7-7.1) in LMD with CABG, and 2.8% (CI 2.1-3.5) without LMD (p = 0.0039 by log-rank test).

CONCLUSION

Enhanced external counterpulsation is equally effective in relieving angina in patients with or without LMD. However, the significantly increased late mortality in patients with LMD without prior CABG suggests that early revascularization should be considered in these patients.

Current and future treatment strategies for refractory angina

Patients with refractory angina are not candidates for revascularization and have both class III or IV angina and objective evidence of ischemia despite optimal medical therapy. An estimated 300,000 to 900,000 patients in the United States have refractory angina, and 25,000 to 75,000 new cases are diagnosed each year. This review focuses on treatment strategies for refractory angina and includes the mechanism of action and clinical trial data for each strategy. The pharmacological agents that have been used are ranolazine, ivabradine, nicorandil, L-arginine, testosterone, and estrogen; currently, only L-arginine, testosterone, and estrogen are approved by the Food and Drug Administration. Results with the noninvasive treatments of enhanced external counterpulsation and transcutaneous electrical nerve stimulation are provided. Invasive treatment strategies including spinal cord stimulation, transmyocardial revascularization, percutaneous myocardial revascularization, and gene therapy are also reviewed.

Enhanced External Counterpulsation for the relief of angina in patients with diabetes: safety, efficacy and 1-year clinical outcomes

BACKGROUND

Patients with diabetes are at greater risk for coronary events, yet they are less likely to benefit from revascularization than those without diabetes. Enhanced external counterpulsation has recently emerged as a treatment option for select patients with chronic stable angina.

METHODS

We examined baseline characteristics, angina response, and cardiac outcomes of patients with diabetes mellitus treated with Enhanced External Counterpulsation (EECP) for chronic stable angina. Data were collected from patients enrolled in the International EECP Patient Registry (IEPR) before and after a course of EECP, and at 1 year after completion of treatment.

RESULTS

Of 1532 IEPR patients studied, 43% had diabetes mellitus at baseline. Patients with diabetes were experiencing, on average, 11 episodes of angina per week. Most had been revascularized with prior percutaneous coronary intervention or coronary artery bypass graft surgery (86%) and most were considered unsuitable for either additional procedure (87%). Treatment was completed as prescribed in 79% of patients (mean, 32 hours). Immediately after EECP, 69% of patients with diabetes demonstrated a reduction in angina of > or =1 Canadian Cardiovascular Society angina class. After 1 year, maintenance of angina reduction was reported in 72% of patients with diabetes. Quality of life was significantly improved. Despite a high-risk profile among the diabetic group in this study, 1-year mortality was similar to coronary intervention registry populations.

CONCLUSION

This study suggests that in select patients with diabetes, EECP can be a safe, effective, well-tolerated treatment option for the relief of angina.

Analysis of baseline factors associated with reduction in chest pain in patients with angina pectoris treated by enhanced external counterpulsation

Data from the International Enhanced External Counterpulsation (EECP) Patient Registry were analyzed to determine which patient characteristics influence improvement in angina class with EECP treatment. Patients with severely disabling angina at baseline, men, and those without a history of smoking are more likely to improve their angina class after EECP, whereas those with diabetes mellitus, prior bypass surgery, and heart failure were less likely to benefit.

Enhanced external counterpulsation for ischemic heart disease: what's behind the curtain?

Enhanced external counterpulsation (EECP) has been shown to reduce angina and to improve objective measures of myocardial ischemia in patients with refractory angina. Prospective clinical studies and large treatment registries suggest that a course of EECP is associated with prolongation of the time to exercise-induced ST-segment depression and resolution of myocardial perfusion defects, as well as with enhanced exercise tolerance and quality of life. With a growing knowledge base supporting the safety and beneficial clinical effects associated with EECP, this therapy can be considered a valuable treatment option, particularly in patients who have exhausted traditional revascularization methods and yet remain symptomatic despite optimal medical care. However, although the concept of external counterpulsation was introduced almost four decades ago, and despite growing evidence supporting the clinical benefit and safety of this therapeutic modality, little is firmly established regarding the mechanisms responsible for the beneficial effects associated with this technique. Suggested mechanisms contributing to the clinical benefit of EECP include improvement in endothelial function, promotion of coronary collateralization, enhancement of ventricular function, peripheral effects similar to those observed with regular physical exercise, and nonspecific placebo effects. This review summarizes the current evidence for a contribution of these mechanisms to the clinical benefit associated with EECP.

Enhanced external counterpulsation

Enhanced external counterpulsation is a noninvasive technique designed to increase myocardial perfusion and reduce cardiac workload in patients with coronary artery disease. Recent trials have documented beneficial hemodynamic effects. Stress testing and radionuclide imaging have demonstrated improvements in functional capacity and myocardial perfusion. This procedure may be the therapeutic choice for patients with severe diffuse disease or in whom repeat revascularization is not possible. The relatively low cost of the technique makes it feasible for patients in developing countries.

Current use of enhanced external counterpulsation and patient selection

Most patients who receive enhanced external counterpulsation (EECP) have symptomatic coronary artery disease. These patients have either responded poorly to pharmacologic therapy or are poor candidates for revascularization procedures. Such patients receive a variety of consistent benefits from EECP treatment. As more is learned about EECP, patients once excluded from early clinical trials are now able to take advantage of EECP. Nevertheless, EECP is not suitable for some patients. It has a favorable adverse event profile for most patients undergoing the treatment. Medicare reimbursement coverage limitations remain an obstacle to having a broad cross-section of patients benefit from EECP.

Psychosocial effects of enhanced external counterpulsation in the angina patient: a second study

Enhanced external counterpulsation (EECP) is a noninvasive technique that has shown promise in the treatment of ischemic coronary artery disease. Patients undergoing EECP were tested for alterations in psychosocial state associated with treatment. Overall perception of health and quality of life improved with EECP. There was also significant improvement in levels of depression, anxiety, and somatization but no change in levels of anger or hostility. On most measures, change was more significant for subjects who showed objective evidence of resolution of ischemia. Given the known predictive relationship between depression and mortality from cardiac disease, the improvement in depression scores through EECP indicates a finding of potential importance that may warrant further study in future research.

Comparison of hemodynamic effects of enhanced external counterpulsation and intra-aortic balloon pumping in patients with acute myocardial infarction

This study compared the hemodynamic effects of enhanced external counterpulsation and intra-aortic counterpulsation in patients with acute myocardial infarction. Results demonstrated similarity between these 2 methods, except enhanced external counterpulsation had a transient effect of increasing right atrial pressure, pulmonary capillary wedge pressure, and cardiac index.