Increases in Cardiac Output and Oxygen Consumption During Enhanced External Counterpulsation.

BACKGROUND: Regular enhanced external counterpulsation (EECP) improves exercise capacity possibly through a training effect, but the roles of oxygen consumption (VO2) vs. direct EECP effects (diastolic augmentation, DA-ratio), and their relation to cardiac index (CI) during EECP are unknown. METHODS: We studied eight patients with angina pectoris (median [range] age 72 [53-85], 25% women), who underwent EECP for 35 daily sessions. Before, during and after the first and last sessions, we assessed VO2, DA-ratio and CI. RESULTS: At first EECP, CI increased from 2.2 (1.7-2.9) L/min/m2 prior to EECP to 3.0 (2.2-3.8) during EECP (p=0.011), and returned to 2.4 (0.8-3.0). Similarly, VO2 increased during EECP and returned to baseline after EECP. These patterns were reproduced at the last EECP session. Absolute values of CI and VO2 correlated with each other during but not prior to or after EECP. The increase in CI correlated with the increase in VO2 by trend: (first session, r 0.52, p=0.19; second session r 0.69, p=0.09), but not with DA-ratio. CONCLUSIONS: Acutely during EECP, there is an increase in cardiac output that is unrelated to direct EECP effects but related to, and may be secondary to, an increase in peripheral O2 demand. This may represent a training effect.

Relation between N-terminal pro-brain natriuretic peptide levels and response to enhanced external counterpulsation in chronic angina pectoris.

OBJECTIVE: Although enhanced external counterpulsation (EECP) provides symptom reduction in many patients with severe angina pectoris, one-quarter of patients fail to respond. Earlier reports have not clearly established whether and how EECP responders may be identified pre-hoc. We hypothesized that clinical and biochemical data may be used to predict EECP response. METHODS: We explored a database of n=53 patients who had undergone clinically indicated EECP during 35 1-h sessions in our unit (65±7 years; 49 male), and sought to clarify which factors are predictive of response. Efficiency of counterpulsation was measured as the diastolic augmentation (DA) ratio, and was recorded both at beginning and end of the EECP treatment course. An increase in 6-min walk (6MW) distance of 5% was indicative of clinical response. RESULTS: Response occurred in 28 patients (53%; nonresponse in n=25, 47%). Responders had shorter baseline 6MW distance (377±81 vs. 445±62 m; P<0.01), lower left ventricular ejection fraction (48±9 vs. 54±8%; P<0.05), frequently had an increase in DA ratio during the EECP treatment course (23/28 vs. 5/28 with unchanged or decreased DA ratio; P<0.05), and higher levels of N-terminal pro-brain natriuretic peptide [NT-proBNP; 256 (123-547) vs. 62 (26-444) ng/l, P<0.01]. In multivariate logistic regression, response was independently predicted by baseline 6MW distance and baseline NT-proBNP levels (P<0.05 for both; model sensitivity: 82%, specificity: 72%, accuracy: 79%). CONCLUSION: There is larger clinical benefit of EECP in patients with greater functional impairment and higher levels of NT-proBNP.