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A Physician's Guide to Enhanced External Counterpulsation
EECP is a noninvasive treatment for patients with coronary artery disease. EECP involves the inflation and deflation of 3 sets of compressive cuffs wrapped around the patient's calves, lower thighs, and buttocks.
During diastole, the cuffs inflate sequentially from the calves to the upper thighs and buttocks to raise diastolic aortic pressure and increase coronary perfusion pressure. Compression of the vascular beds of the legs also increases venous return.
Rapid and simultaneous deflation of the cuffs at the onset of systole produces significant left ventricular unloading with an associated decrease in cardiac workload. Inflation and deflation are triggered by events in the cardiac cycle via microprocessor interpreted EEG signals.
History of EECP Therapy
Kantrowitz and Kantrowitz first described the principle of "phase shift diastolic augmentation", in 1953. Physicians and physicists at Harvard and elsewhere related this principle to oxygen consumption and cardiac workload. This understanding led to the concept of mechanically induced "cardiac assistance" for patients with low cardiac output syndromes, especially cardiogenic shock.
Beginning in the 1960's, research on mechanically induced "cardiac assistance" followed tow distinct paths, one involved the use of a balloon positioned inside the descending thoracic aorta that would inflate during diastole and deflate at the onset of systole and another that involved the external compression and release of the vascular beds in the lower limbs. The first came to be known as the intra-aortic balloon pump or IABP. The second evolved into what is now referred to as external counterpulsation. These early systems were somewhat primitive by today's standards, but both forms of counterpulsation clearly demonstrated the potential for increasing survival of patients with myocardial infarction and cardiogenic shock as well as for relief of angina pectoris.
Early hydraulic systems for external counterpulsation eventually gave way to pneumatics. This, along with refinements of the compression elements of the system, helped to improve outcomes and patient comfort.
The National Institutes of Health (NIH) played a significant role in the evolution of modern external counterpulsation systems by advocating the addition of a second cuff and the use of sequential cuff inflation to increase the amount of blood being returned to the heart and, as a result, diastolic augmentation. During the 1970's, Zheng and associates at Sun Yat-sen University in China reported on a newly designed 3 stage pneumatic pulsation system. In these trials, effects of sequenced cuff inflation were studied in patients with angina pectoris and myocardial infarction. In more than 90% of 200 patients with angina, the system provided long-term symptomatic relief with minimal relapse, following 36 hours of treatment.
The favorable results reported by the Chinese group led scientists at the State University of New York at Stony Brook, to reassess the efficacy of external counterpulsation in treating patients with angina pectoris using a new "enhanced" counterpulsation system.
EECP, enhanced external counterpulsation, employs a three-cuff compression configuration and a sophisticated computerized control of the inflation/deflation sequence. This enhanced system has been shown to provide sustained relief of angina, and improvement in myocardial perfusion documented by nuclear imaging.
Mode of Action
EECP therapy produces beneficial effects that appear mediated through arterial diastolic augmentation. Continuation of benefits for up to 3 years following a course of EECP treatment has been reported. The retrograde arterial pressure wave increases coronary perfusion pressure, creating a gradient between ischemic and non-ischemic areas of the myocardium that may recruit latent conduits and enhance myocardial perfusion.
Diastolic augmentation produced by EECP greatly increases pulsatile shear stress on the intima. Recent research has uncovered a multitude of endothelial responses to shear stress. Increased endothelial shear stress releases growth factors. Increased nitric oxide (NO) and atrial natriuretic peptide (ANP) levels, and decreased endothelin (EN-1) and brain natriuretic peptide (BNP) levels, also ascribed to increased shear stress and improved endothelial function, raise the possibility of peripheral benefits as well as restored coronary flow reserve.
Key Clinical Studies
Clinical trials of external counterpulsation date back to the 1960's and have been ongoing since then. Reduction in anginal episodes, increased exercise times, and significant improvement in health-related quality-of-life scores have been demonstrated in controlled studies. In addition, significant benefits were demonstrated in such diverse patient populations as the elderly, diabetics, patients with LVD, patients refractory to medical therapy, and patients no longer candidates for surgical or catheter-based revascularization.
Patient's Medical Status
Contraindications:
Arrhythmias that interfere with machine triggering (Bigeminal arrhythmia)
Bleeding diathesis
Active thrombophlebitis
Severe lower extremity vaso-occlusive disease
Presence of a documented aortic aneurysm requiring surgical repair
Medicare / Insurance Guidelines
Under Medicare Policy (35-74) patients eligible for EECP are those who have been diagnosed with disabling angina (CCS Angina Class III or IV or an angina equivalent classification) and who, in the opinion of a cardiologist or cardiovascular surgeon, are not readily amenable to surgical intervention.
EECP Therapy: An Option You Can Count On
Non invasive external counterpulsation has been studied for more than 40 years. Recent published clinical studies demonstrate an increase in exercise capacity, peak oxygen consumption and quality of life for angina and ischemic heart failure patients.
Heart failure and angina candidates who benefit from EECP therapy include:
Patients with chronic stable angina
Patients who no longer respond to medical therapy
Patients who have coronary anatomy unsuitable for surgical or catheter-based revascularization
Patients who have failed an invasive procedure and have persistent angina
Patients who have exhausted invasive treatments without lasting relief of symptoms
Patients who are unwilling to undergo additional surgery or ischemia
HF due to obstructive coronary artery disease or ischemia
Patients with microvascular angina (Cardiac Syndrome X)
LVD-Low ejection fractions (EF<35%)
Patients who have restricted their daily activities to help manage their condition and minimize the potential of a symptomatic occurrence
Other co-morbid conditions that increase the risk of revascularization procedures (e.g., diabetes, heart failure, pulmonary disease, renal dysfunction)
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