Effect of enhanced external counterpulsation depends on arterial compliance

Enhanced external counterpulsation (EECP) is a non-invasive therapy offered to patients with refractory angina pectoris. Previous studies have demonstrated that its clinical effect depends on the diastolic/systolic augmentation ratio (D/S ratio). We hypothesized that the D/S ratio is associated with arterial stiffness measured as pulse wave velocity (PWV) and brachial pulse pressure (PP). Twenty patients with known refractory angina (17 men, 3 women; mean age 64 years) were included and underwent one hour of EECP treatment (Vasomedical Inc., Westbury, NY, USA). Three sets of cuffs were applied around the lower extremities. Gated by electrocardiography (ECG), air was inflated in diastole at a pressure of 260 mmHg and deflated at the start of systole. The D/S ratio was monitored with finger plethysmography. Carotid-femoral pulse wave velocity (PWV) was measured with mechanotransducers (Complior SP, Artech Medical, France). PWV and brachial BP were measured at baseline before EECP. The mean (SD) BP was 140 (23.5)/77 (9.9) mmHg, PP 62.8 (18.3) mmHg and PWV 10.8 (4.4) m/s. EECP treatment increased the D/S ratio during a one-hour session compared with baseline (1.30 (0.11) vs. 0.56 (0.04) P < 0.001), and the D/S ratio at 45 min. was significantly correlated with PWV (r = 0.49, P < 0.05) and PP (r = 0.58, P < 0.05). We demonstrated that the diastolic augmentation (D/S ratio) during EECP treatment depends on arterial stiffness. The results suggest that arterial compliance has a crucial influence on the effect of EECP and that large-artery stiffness may reduce the effect of EECP.