A growing number of patients with SIHD have refractory angina, defined as multivessel CAD with ischemia and symptoms that cannot be controlled with medical therapy or surgical or percutaneous revascularization. The prevalence of this syndrome is not well established, but data from registries suggest that about 10% of patients referred for angiography for symptomatic SIHD have coronary anatomy that is not amenable to revascularization.933 935 Other nonpharmacologi- cal therapies may be considered in these patients in an effort to improve quality of life. 4.4.4.1. Enhanced External Counterpulsation EECP is a technique that uses inflatable cuffs wrapped around the lower extremities to increase venous return and augment diastolic BP. The cuffs are inflated sequentially from the calves to the thigh muscles during diastole and are deflated instantaneously during systole. The resultant diastol- ic augmentation increases coronary perfusion pressure, and the systolic cuff depression decreases peripheral resistance. Treatment is associated with improved LV diastolic filling and improved endothelial function936 938; other putative mechanisms for improvement in symptoms include recruit- ment of collaterals, release of proangiogenic cytokines, and a peripheral training effect. A treatment course typically con- sists of 35 hour-long treatment sessions, given 5 days a week. Contraindications include decompensated heart failure, se- vere PAD, and severe aortic regurgitation. The efficacy of EECP in treating stable angina pectoris has been evaluated in a single RCT and several observational registry studies. 