Can angiographic findings predict which coronary patients will benefit from enhanced external counterpulsation?

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.

Maximizing the hemodynamic benefit of enhanced external counterpulsation

BACKGROUND

Enhanced external counterpulsation (EECP) has been demonstrated to be an effective treatment for angina and exertional ischemia in patients with coronary disease.

HYPOTHESIS

It is hypothesized that the ability of EECP to enhance the recruitment or development of coronary collaterals in coronary artery disease may be determined by the relative magnitude of diastolic augmentation (DA) and systolic unloading (SU). This study examines the relation between the proposed EECP effectiveness ratio (DA/SU), as assessed by finger plethysmography, and changes in descending aortic flow as assessed by Doppler echocardiography in 15 patients during EECP.

METHODS

Varying external cuff pressures (0-275 mmHg) were used to generate a range of DA/SU ratios. The effect on aortic antegrade systolic and retrograde diastolic flow was assessed by Doppler echocardiography to determine whether there was an optimal EECP effectiveness ratio that maximizes the hemodynamic effects of EECP. With increasing DA/SU there was an initial positive linear increase in both systolic and diastolic flow volume. Systolic flow maximized at an effectiveness ratio of 1.5 and diastolic flow at a ratio of 2.0

RESULT

Therefore, effectiveness ratios (DA/SU) in the range of 1.5-2.0 are optimal for maximizing the hemodynamic effects of EECP.

Prior revascularization increases the effectiveness of enhanced external counterpulsation

BACKGROUND AND HYPOTHESIS

Enhanced external counterpulsation (EECP) is an effective noninvasive treatment for chronic angina. However, its usefulness has been felt to be limited in patients with angiographically demonstrated triple-vessel coronary artery disease (CAD), in accord with the hypothesis that a patent vessel is necessary for transmission of the EECP-augmented coronary artery pressure and volume to the distal coronary vasculature.

METHODS

The effect of revascularization [coronary artery bypass grafting (CABG)] prior to EECP was examined in 60 patients with CAD and chronic angina (35 without and 25 with prior CABG). Patients were grouped by the extent of CAD (single-, double-, triple-vessel disease in the unrevascularized group) and by the extent of residual disease (number of stenotic native vessels unbypassed or supplied by a stenotic graft in the CABG group). Significant CAD or graft stenoses were defined as stenoses demonstrating > or = 70% luminal diameter narrowing. Benefit was assessed by improvement in post-EECP treatment over pretreatment radionuclide stress testing.

RESULTS

Radionuclide stress testing demonstrated a comparable favorable response (80 vs. 71%; p = NS) in patients with prior CABG versus unrevascularized patients. Enhanced external counterpulsation was highly and comparably effective in patients with unrevascularized native single- and double-vessel CAD and in patients with CABG with residual single- and double-vessel CAD (88 vs. 80%; p = NS). Most notably, CABG significantly increased the beneficial response to EECP in those patients with triple-vessel CAD and stenotic grafts compared with unrevascularized patients with triple-vessel CAD (80 vs. 22%; p < 0.05 by chi-square test).

CONCLUSION

The results suggest a new role for EECP as an effective treatment for post CABG ischemia, despite extensive CAD and even in the presence of stenotic grafts.

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.

Exercise capability and myocardial perfusion in chronic angina patients treated with enhanced external counterpulsation

BACKGROUND

Enhanced external counterpulsation (EECP) has been shown to improve treadmill times and myocardial perfusion. However, improvement in perfusion defects has been demonstrated only in patients exercised to the same cardiac workload on the post-EECP as the pre-EECP stress test.

HYPOTHESIS

This study was to determine the effect of EECP on exercise capacity and myocardial perfusion by comparing results of maximal exercise radionuclide testing pre- and post-EECP treatment.

METHODS

This prospective study included 25 patients with angina who had performed maximal symptom-limited exercise tolerance tests (ETT) with Bruce protocol and radionuclide perfusion single-photon emission computed tomography (SPECT) study prior to and at completion of EECP treatment.

RESULTS

After 35 h of EECP, 23 patients (93%) improved by at least one functional angina class. There is a significant improvement in their total treadmill times (357 +/- 93 to 449 +/- 97 s, p < 0.001). There was a significant change in their peak double products, from 18,891 +/- 3,939 pre-EECP to 20,464 +/- 4,305 post-EECP ETT (p < 0.03). Pre EECP, 16 patients had ST-segment depression on their initial ETT. After EECP, 13 of these patients (80%) either no longer had ST depression or had a significant increase in their time to ST depression (229 +/- 52 to 315 +/- 60 s, p < 0.001). The radionuclide perfusion scores also showed a significant reduction in ischemic segments (16.36 +/- 10.52 to 14 +/- 10.9, p < 0.05).

CONCLUSIONS

Patients treated with EECP demonstrated a reduction in angina symptoms, improvement in exercise capacity, increase in time to ST-segment depression, and decrease in perfusion defects despite performing at a higher workload.

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.

The effects of enhanced external counterpulsation on myocardial perfusion in patients with stable angina: a multicenter radionuclide study

BACKGROUND

Enhanced external counterpulsation (EECP) reduces angina and extends time to exercise-induced ischemia in patients with symptomatic coronary disease. One- and two-center studies and a retrospective case series reported that EECP improves myocardial perfusion in stable angina pectoris. We sought to critically evaluate and quantify the effect of EECP on myocardial perfusion.

METHODS

In 6 US university hospitals, EECP was performed for 35 hours in patients with class II to IV angina who had exercise-induced myocardial ischemia. Symptom-limited quantitative gated technetium Tc 99m sestamibi single photon emission computed tomography exercise perfusion imaging was performed at baseline and 1 month post-EECP. Sestamibi was injected at the same heart rate in both stress tests. Single photon emission computed tomography images were read at a blinded core laboratory.

RESULTS

Thirty-seven patients were enrolled, 34 of whom completed pre- and post-EECP stress testing. The mean age was 61 +/- 10 years, 81% were male, 78% had prior revascularization, and 68% had 3-vessel disease. The mean angina class decreased from 2.7 +/- 0.7 at baseline to 1.7 +/- 0.7 after EECP (P < .001). Exercise duration increased from 9.1 +/- 3.7 minutes at baseline to 10.2 +/- 3.6 minutes post-EECP (P = .03). The average percentage of tracer uptake, magnitude of reversibility, average thickening fraction, and the left ventricular ejection fraction remained unchanged after EECP.

CONCLUSIONS

We confirm previous report that EECP reduces angina and improves exercise capacity. There were no significant changes in mean defect magnitude, amount of reversibility, thickening fraction, and ejection fraction measured using myocardial quantitative single photon emission computed tomography imaging when compared at identical pre- and post-EECP heart rates.

An update on enhanced external counterpulsation

The development of advanced revascularization techniques has resulted in the growth of a subset of patients with coronary artery disease who are nonrevascularizable and are considered to have refractory angina. Enhanced external counterpulsation (EECP) has been developed for the management of these patients with chronic, refractory disease. Evidence has shown that through improvement of vascular endothelial function and recruitment of collateral vessels, EECP provides many clinical benefits. These patients experience sustained decreases in angina, improvement in exercise time, improved myocardial perfusion, and enhanced quality of life. Furthermore, EECP appears to be safe and effective in the treatment of angina in patients with impaired systolic function and has similar potential in patients with congestive heart failure.

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 refractory angina pectoris

Enhanced external counterpulsation (EECP) is a non-invasive outpatient treatment used for angina pectoris. In patients with intractable angina refractory to aggressive surgical and medical treatment, several novel strategies are considered including EECP, transmural laser revascularisation, and spinal cord stimulation. EECP produces an acute haemodynamic effect that is presumed to be similar to that produced by the invasive intra-aortic balloon pump. By applying a series of compressive cuffs sequentially from the calves to the thigh muscles upon diastole and rapidly deflating the cuffs in early systole, an increase in diastolic and decrease in systolic pressure is created. Although data indicate improvement in angina in patients undergoing EECP, the role of EECP in the treatment of angina pectoris has not yet been well defined. At present, EECP use should be limited to patients with debilitating (functional class III and IV) refractory angina pectoris who are not candidates for revascularisation, are symptomatic despite being on maximal antianginal pharmacotherapy, and have no contraindications to EECP use.

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.

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.

Enhanced external counterpulsation as treatment for chronic angina in patients with left ventricular dysfunction: a report from the International EECP Patient Registry (IEPR)

The International Enhanced External Counterpulsation (EECP) Patient Registry tracks acute and long-term outcome for consecutive patients treated for chronic angina. Although EECP has previously been shown to be a safe and effective treatment for angina, little information is available on its use in patients with left ventricular (LV) dysfunction. This report compares the acute outcome and 6-month follow-up for a group of patients with severe LV dysfunction and a group of patients without LV dysfunction. Of 1,402 patients in the registry recruited in 1998-1999 who had recorded values of LV ejection fraction (LVEF) at baseline, 1,090 (77.7%) had preserved LV function (LVEF >35%) and 312 (22.3%) had LV dysfunction (LVEF </=35%). Six-month follow-up was available on 84% of these patients. Pre-EECP patients with LV dysfunction had a longer history of coronary artery disease (12.9 years vs. 9.1 years; p<0.001), a higher rate of congestive heart failure (60.6% vs. 20.1%; p<0.001) and myocardial infarction (83.5% vs. 61.9%; p<0.001). Patients with LV dysfunction had more severe pre-EECP angina, with 86.2% presenting with Canadian Cardiovascular Society Class III/IV vs. 73.6%; p<0.01. Patients with LV dysfunction, consistent with their more severe baseline profile, suffered more adverse events (death, unstable angina, and exacerbation of heart failure) during the treatment period and were less likely to complete the full course. Immediately post-EECP, angina decreased by at least one class in 67.8% of patients with LV dysfunction (vs. 76.2%; p<0.01), and 35.9% of LV dysfunction patients vs. 39.0% had discontinued nitroglycerin use (p=ns). At 6-month follow-up, patients with LV dysfunction showed higher rates of death (9.3% vs. 2.2%; p<0.001) and exacerbation of congestive heart failure (9.9% vs. 3.7%; p<0.001). Rates of the composite outcome of death/myocardial infarction/coronary artery bypass grafting/percutaneous coronary intervention (15.4% vs. 8.3%; p<0.001) were also higher for patients with LV dysfunction. However, patients not reporting such an event showed maintenance of their improved anginal status, with 81% of LV dysfunction vs. 83.8% of patients without LV dysfunction (p=ns) reporting angina at 6 months equal to or less severe than immediately post-EECP, and nitroglycerin use was still reduced at 46.1% for LV dysfunction vs. 37.4% (p<0.05). The rate of event-free angina maintenance at 6 months was 67.0% for patients with LV dysfunction and 70.6% of patients with preserved LV function (p=ns). Patients with LV dysfunction achieved a less robust reduction in angina than did those without LV dysfunction. For the majority of the patients in the registry, this reduction was maintained at 6 months.

Effects of enhanced external counterpulsation on stress radionuclide coronary perfusion and exercise capacity in chronic stable angina pectoris

Enhanced external counterpulsation (EECP) is an effective noninvasive treatment for patients with coronary artery disease (CAD). EECP has been demonstrated to improve anginal class and time to ST-segment depression during exercise stress testing. This study assesses the efficacy of EECP in improving stress-induced myocardial ischemia using radionuclide perfusion treadmill stress tests (RPSTs). The international study group enrolled patients from 7 centers with chronic stable angina pectoris and a baseline ischemic pre-EECP RPST. Patients' demographic and clinical characteristics were recorded. A baseline pre-EECP maximal RPST was performed within 1 month before EECP treatment. The results were compared with a follow-up RPST performed within 6 months of completion of a 35-hour course of EECP. Four centers performed post-EECP RPST to the same level of exercise as pre-EECP, whereas 3 centers performed maximal RPST post-EECP. The study enrolled 175 patients (155 men and 20 women). Improvement in angina, defined by > or =1 Canadian Cardiovascular Society angina class change, was reported in 85% of patients. In the centers performing the same level of exercise, 81 of 97 patients (83%) had significant improvement in RPST perfusion images. Patients who underwent maximal RPST revealed improvement in exercise duration (6.61 +/- 1.88 pre-EECP vs 7.41 +/- 2.03 minutes post-EECP, p <0.0001); 42 of the 78 patients (54%) in this group showed significant improvement in RPST perfusion images. Thus, EECP was effective in improving stress myocardial perfusion in patients with chronic stable angina at both comparable (baseline) and at maximal exercise levels.

Effects of enhanced external counterpulsation on Health-Related Quality of Life continue 12 months after treatment: a substudy of the Multicenter Study of Enhanced External Counterpulsation

BACKGROUND

The Multicenter Study of Enhanced External Counterpulsation (MUST-EECP) was the first prospective, randomized, blinded, sham-controlled study of enhanced external counterpulsation (EECP) in the treatment of chronic stable angina. We previously reported that EECP therapy lengthens the time to exercise-induced myocardial ischemia and reduces angina. We now describe the effects of EECP therapy versus a sham-treated control group in terms of patients' functioning, their senses of well-being and other Health-Related Quality Of Life (HQOL) parameters from baseline to end of treatment and from baseline to 12 months after treatment.

OBJECTIVE

To determine whether a 35-hour course of EECP affects the HQOL of patients with symptomatic coronary artery disease, 12 months following treatment.

METHODS

Seventy-one of the 139 patients enrolled in MUST-EECP provided evaluable patient-completed questionnaires at baseline, at the end of treatment, and 12 months post-treatment. The Medical Outcomes Study 36-Item Short-Form Health Survey and the Quality of Life Index-Cardiac Version III were used to assess effects on HQOL.

RESULTS

Both groups had similar HQOL scores at baseline. At end of treatment and at 12-month follow up, patients who had active-CP reported greater improvement than those who had inactive-CP in all nine quality of life scales, including ability to perform activities of daily living, ability to work, bodily pain, confidence in health, energy, ability to engage in social activities with family and friends, anxiety and depression, and quality of life issues from the effects of angina on health and functioning. Despite small sample sizes, active-CP patients demonstrated significantly greater improvement at 12 months following treatment in bodily pain, social functioning, and quality of life specific to cardiac patients compared with inactive-CP patients.

CONCLUSION

Significant health-related quality of life improvements were measurable up to 12 months after the completion of treatment with EECP. Improvements in this controlled study are consistent with HQOL changes reported in case series and patient registries. Larger studies are warranted.

Acute hemodynamic effects and angina improvement with enhanced external counterpulsation

Enhanced external counterpulsation (EECP) is an effective noninvasive treatment for coronary artery disease. The mechanism of action is felt to be hemodynamic. The complex hemodynamic effects have been simply quantified by calculating a previously described effectiveness ratio (ER). The EECP Clinical Consortium, a clinical registry of 37 centers, prospectively enrolled 395 chronic stable angina patients (79 women, 316 men, mean age 66 years) to examine the relation of the ER to posttreatment improvement in Canadian Cardiovascular Society angina class (CCS). Women and the elderly underwent planned subgroup analysis. The ER was calculated during the first and last hours of a 35-hour course of EECP treatment. After EECP, CCS improved by at least 1 class in 88% of patients, 87% of men and 92% of women (p = NS), and in 89% of patients < or = 66 years and 88% of patients > 66 years old (p = NS). The initial and final ER were similar in patients with and without improvement in CCS. Significant first-hour ER differences were seen between men and women (0.96 +/- 0.03 vs 0.76 +/- 0.04, p<0.005), and between ages < or = 66 and > 66 years old (1.04 +/- 0.04 vs 0.81 +/- 0.03, p<0.0001). However, all subgroups responded equally well to EECP treatment. EECP is effective in improving CCS in chronic stable angina patients; it has comparable effects in men and women and across a broad range of ages. The hemodynamic effect of EECP (ER) does not predict improvement in CCS and may indicate that other factors, such as neurohormonal changes, may have a significant role in mediating the observed EECP benefits.

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.

The multicenter study of enhanced external counterpulsation (MUST-EECP): effect of EECP on exercise-induced myocardial ischemia and anginal episodes

OBJECTIVES

The purpose of this study was to assess safety and efficacy of enhanced external counterpulsation (EECP).

BACKGROUND

Case series have shown that EECP can improve exercise tolerance, symptoms and myocardial perfusion in stable angina pectoris.

METHODS

A multicenter, prospective, randomized, blinded, controlled trial was conducted in seven university hospitals in 139 outpatients with angina, documented coronary artery disease (CAD) and positive exercise treadmill test. Patients were given 35 h of active counterpulsation (active CP) or inactive counterpulsation (inactive CP) over a four- to seven-week period. Outcome measures were exercise duration and time to > or =1-mm ST-segment depression, average daily anginal attack count and nitroglycerin usage.

RESULTS

Exercise duration increased in both groups, but the between-group difference was not significant (p > 0.3). Time to > or =1-mm ST-segment depression increased significantly from baseline in active CP compared with inactive CP (p = 0.01). More active-CP patients saw a decrease and fewer experienced an increase in angina episodes as compared with inactive-CP patients (p < 0.05). Nitroglycerin usage decreased in active CP but did not change in the inactive-CP group. The between-group difference was not significant (p > 0.7).

CONCLUSIONS

Enhanced external counterpulsation reduces angina and extends time to exercise-induced ischemia in patients with symptomatic CAD. Treatment was relatively well tolerated and free of limiting side effects in most patients.

Enhanced external counterpulsation in the management of patients with cardiovascular disease

Studies over the past several decades support the hypothesis that enhanced external counterpulsation (EECP) can provide long-term benefits in patients with angina secondary to chronic coronary disease. Numerous non-sham controlled trials have recently been substantiated by a multicenter, randomized trial. Although the mechanism by which this mechanical treatment effects an alteration in cellular processes within the myocardium remains unclear, recent scientific investigations suggest that shear stress induced by chronic exposure to EECP might result in the release of a variety of growth factors and the subsequent stimulation of angiogenesis in the coronary beds. Ongoing clinical trials in patients with significant left ventricular dysfunction, an international registry, and additional clinical trials may help to elucidate further the role of this novel and unique therapy in our clinical armamentarium.

Improved hemodynamics shown by continuous monitoring of electrical impedance during external counterpulsation with the end-diastolic pneumatic boot and improved ambulatory EKG monitoring after 3 weeks of therapy

Six normal subjects and 12 patients with clinical angina and significant ST depressions during baseline ambulatory cardiac monitoring were given a single treatment with the end-diastolic pneumatic compression boot, the Circulator Boot. With the use of continuous electrical impedance measurements, multiple hemodynamic variables were followed in five situations: (1) baseline before pumping; during end-diastolic pumping (2) on both legs after every heartbeat, (3) on one leg after every heartbeat, and (4) on both legs on alternate beats; and (5) during pumping on both legs during every systole. Both an increase in venous return and a reduction in afterload likely contributed to significant increases in cardiac output (CO) (51.1 +/- 33.6%), stroke volume (SV) (52.1 +/- 35.6%), change in impedance over time (dZ/dT) (72.0 +/- 68.1%), cardiac index (CI) (51.2 +/- 33.8%), and acceleration index (50.7 +/- 62.2%) during end-diastolic pumping on both legs after every heartbeat. A crucial role for afterload reduction was implied by opposite effects observed on CO, CI, dZ/dT, and SV during systolic pumping. Again, reductions (or a lack of an increase) in ventricular ejection time and/or the preejection period suggested a decrease in afterload during end-diastolic pumping. Pumping on one leg after every beat and on both legs on alternate beats was also effective but less so. After the initial study, the patients were given 14 additional end-diastolic treatments to both legs over 3 weeks. A clinical benefit for the patients was shown by symptomatic improvement in all patients along with a significant reduction in the amount and duration of the RST abnormalities in their ambulatory heart monitoring (p = 0.012).

External leg compression in the treatment of vascular disease

In summary, external compression of the limbs is a mode of therapy that has enjoyed a long history in the treatment of venous and arterial disease. Evidence suggests that its beneficial effects are mediated through enhancement of venous and arterial blood flow, promotion of vasodilation, enhancement of fibrinolysis, and, in the case of obstructive arterial disease, promotion of the development of collateral circulation. The utility of external leg compression in the prevention of deep venous thrombosis and in the management of chronic venous stasis disease has been well documented, and it has become an accepted treatment for these disorders. The use of pneumatic compression in the treatment of atherosclerotic peripheral vascular and cardiovascular disease is less widespread and its indications are less well defined. Though the work of a few investigators in each of these areas shows striking benefits of the technique, further investigation in these areas is warranted. Potential benefits to patients of external limb compression therapy include its non-invasive nature, its ability to be applied in an out-patient setting, and long-term cost savings through possible avoidance of hospitalization and invasive procedures.