Effect of external counterpulsation on cardiac work following cardiac surgery: Implications of the mechanism responsible for clinical benefits

SummaryBackgroundExternal counterpulsation (ECP) has been recognized as a non-invasive treatment for chronic refractory angina or heart failure. However, the mechanisms responsible for the clinical benefits of ECP therapy remain elusive. Moreover, the clinical significance of ECP therapy for postoperative patients has not been established yet.MethodsSix adult patients received ECP therapy for 60 min under pulmonary artery catheter monitoring after cardiac surgery. Hemodynamic data were obtained before ECP therapy (pre-ECP), 20 min after ECP was commenced (20-min-ECP), 40 min after ECP was commenced (40-min-ECP), and after ECP therapy (post-ECP).ResultsThe mean right atrial pressure (pre-ECP: 9 ± 4 mmHg; 20-min-ECP: 12 ± 5 mmHg; 40-min-ECP: 12 ± 4 mmHg; and post-ECP: 9 ± 4 mmHg), pulmonary wedge pressure (16 ± 6 mmHg, 20 ± 7 mmHg, 20 ± 7 mmHg, and 17 ± 7 mmHg, respectively), cardiac index (2.4 ± 0.4 l/min/m2, 2.8 ± 0.6 l/min/m2, 2.7 ± 0.5 l/min/m2, and 2.5 ± 0.4 l/min/m2, respectively), cardiac work index (2.5 ± 0.4 kg m/m2, 3.3 ± 0.8 kg m/m2, 3.1 ± 0.8 kg m/m2, and 2.6 ± 0.5 kg m/m2, respectively), and left ventricular stroke work index (32 ± 7 g m/m2, 41 ± 12 g m/m2, 39 ± 12 g m/m2, and 33 ± 8 g m/m2, respectively) significantly (p < 0.05) increased after ECP was commenced (pre-ECP vs. 20-min-ECP) and decreased after ECP was discontinued (40-min-ECP vs. post-ECP). Significant (p < 0.001) diastolic augmentation (20-min-ECP: 24 ± 6%, 40-min-ECP: 23 ± 5%) and systolic unloading (3 ± 1%, and 3 ± 1%, respectively) were obtained. No clinical adverse effects were observed.ConclusionsECP increases venous return, cardiac output, and cardiac work in addition to diastolic augmentation and systolic unloading. These actions may play important roles in the clinical benefits of ECP therapy. Our data also suggest that ECP is beneficial for patients undergoing cardiac surgery.