Enhanced external counterpulsation (EECP) is a noninvasive form of treatment for angina. While several clinical studies appear to show that this treatment can be quite helpful in reducing symptoms of angina in patients with coronary artery disease (CAD), EECP has yet to be accepted by most cardiologists, and has not entered the mainstream of cardiology practice.
What is EECP?
EECP is a mechanical procedure in which long inflatable cuffs (like blood pressure cuffs) are wrapped around both of the patient’s legs. While the patient lies on a bed, the leg cuffs are inflated and deflated synchronously with each heartbeat. The inflation and deflation are controlled by a computer, which uses the patient’s ECG to trigger deflation just as each heartbeat begins, and to trigger inflation just as each heartbeat ends. The inflation of the cuffs occurs in a sequential fashion, so that the blood in the legs is “milked” upwards, toward the heart.
EECP has at least two potentially beneficial actions on the heart. First, the milking action of the leg cuffs increases the blood flow to the coronary arteries during diastole. (The coronary arteries, unlike other arteries in the body, receive their blood flow in between heartbeats, instead of during each heartbeat. EECP, then, helps to “pump” blood into the coronary arteries.) Second, by its deflating action just as the heart begins to beat, EECP creates something like a sudden vacuum in the arteries, which reduces the work of the heart muscle in pumping blood into the arteries.
Both of these actions have long been known to reduce cardiac ischemia (the lack of oxygen in the heart muscle) in patients with CAD. Indeed, an invasive procedure that does the same thing, intra-aortic counterpulsation (IACP, in which a balloon-tipped catheter is positioned in the aorta, which then inflates and deflates in time with the heartbeat), has been in widespread use in intensive care units for decades, and its effectiveness in stabilizing extremely unstable patients is well known.
While a primitive form of external counterpulsation has also been around for a long time, it has not been very effective until recently. Thanks to new computer technology that allows precise timing of the inflation and deflation of the cuffs, modern EECP has been greatly enhanced.
EECP is administered as a series of outpatient treatments. Patients receive 5 one-hour sessions per week, for 7 weeks (for a total of 35 sessions). The 35 one-hour sessions are aimed at provoking long lasting beneficial changes in the circulatory system.
How Effective Is EECP?
Several studies suggest that EECP can be quite effective in treating chronic stable angina. A 1999 randomized trial with EECP showed that EECP significantly improved both the symptoms of angina (a subjective measurement) and exercise tolerance (a more objective measurement) in patients with CAD. EECP also significantly improved “quality of life” measures, as compared to placebo therapy. Studies also show that the improvement in symptoms following a course of EECP seems to persist for up to five years (though 1 in 5 patients may require another course of EECP to maintain their improvement).
How Does EECP Work?
The mechanism for the sustained benefits seen with EECP is not fully defined. Everyone can agree that there are good reasons for EECP (just as for standard IACP therapy) to benefit the heart while the treatment is actually taking place. But as to why the benefit of EECP seems to persist even after the therapy is finished, no one can say for sure. There is some evidence suggesting that EECP can help induce the formation of collateral vessels in the coronary artery tree, by stimulating the release of nitric oxide and other growth factors in within the coronary arteries. There is also evidence that EECP may act as a form of “passive” exercise, leading to the same sorts of persistent beneficial changes in the autonomic nervous system that are seen with real exercise.
Can EECP Be Harmful?
EECP can be somewhat uncomfortable (it is said to be more difficult to watch that to actually have it done– what with the patient being noticeably jostled due to the milking action of the inflatable leg cuffs), but is not painful. In fact, it is apparently very well tolerated by the large majority of patients.
But not everyone can have EECP. People probably should not have EECP if they have certain types of valvular heart disease (especially aortic insufficiency), or if they have had a recent cardiac catheterization, an irregular heart rhythm such as atrial fibrillation, severe hypertension, peripheral artery disease involving the legs, or a history of deep venous thrombosis (blood clots in the legs). For anyone else, however, the procedure appears to be quite safe.
When Is EECP Recommended?
Based on what we know today, EECP should be considered in anybody who still has angina despite maximal medical therapy, and in whom stents or bypass surgery are deemed not to be good options. Medicare has approved coverage for EECP for patients in this category, that is, for patients with angina who have exhausted all their other choices.
The American College of Cardiology/American Heart Association guidelines have so far declined to recommend EECP for anybody, saying that more clinical trials are needed first. These guidelines first reviewed the available clinical studies with EECP and summarized them as follows: “These studies found the treatment to be generally well tolerated and efficacious; anginal symptoms were improved in approximately 75% to 80% of patients.” But without any further elaboration, the guidelines in the very next sentence concluded, "However, additional clinical trial data are necessary before this technology can be recommended definitively.” So the guidelines followed by cardiologists stopped short of recommending EECP for anyone, ever - despite the fact that the studies cited by the guidelines appear to show it is quite safe, and apparently quite effective.
In any case, the cardiology community - which is only too pleased to have an excuse to altogether ignore such an outlandish form of therapy - generally fails to even consider offering EECP as a therapeutic option. And consequently, most patients who have angina never hear about it.
When a noninvasive treatment for angina exists that is safe and well tolerated, when available evidence (as imperfect as it may be) strongly suggests the treatment is quite effective in many patients, and when the patient being treated will be able to tell pretty definitively whether or not the treatment has helped in their own individual case (by the presence or absence of a substantial reduction in angina symptoms), it does not seem unreasonable to allow patients with stable angina to opt for a trial of that noninvasive therapy, before they are pushed into invasive therapy.
If you are being treated for stable angina and still have symptoms despite medical therapy, and if your doctor is talking to you about a stent, it is entirely reasonable for you to bring up the possibility of trying EECP. Keep in mind that treating stable angina with stents has not been shown to improve survival or prevent heart attacks over and above medical therapy - in most cases a stent just helps get rid of the symptom of angina. If that same goal (relieving angina) can be achieved noninvasively (which is why your doctor tried medical therapy in the first place), why not consider it?
Your doctor should be quite willing to discuss the possibility of EECP with you, and without prejudice.
Arora RR, Chou TM, Jain D, et al. The multicenter study of enhanced external counterpulsation (MUST-EECP): effect of EECP on exercise-induced myocardial ischemia and anginal episodes. J Am Coll Cardiol 1999; 33:1833.
Soran O, Kennard ED, Kfoury AG, et al. Two-year clinical outcomes after enhanced external counterpulsation (EECP) therapy in patients with refractory angina pectoris and left ventricular dysfunction (report from The International EECP Patient Registry). Am J Cardiol 2006; 97:17.
Urano H, Ikeda H, Ueno T, et al. Enhanced external counterpulsation improves exercise tolerance, reduces exercise-induced myocardial ischemia and improves left ventricular diastolic filling in patients with coronary artery disease. J Am Coll Cardiol 2001; 37:93.
Shechter M, Matetzky S, Feinberg MS, et al. External counterpulsation therapy improves endothelial function in patients with refractory angina pectoris. J Am Coll Cardiol 2003; 42:2090.
Committee on the Management of Patients with Chronic Stable Angina. ACC/AHA 2002 Guidelines Update for the Management of Patients with Chronic Stable Angina - Summary Article. Circulation, 2003;107:149–158.