Improved hemodynamics shown by continuous monitoring of electrical impedance during external counterpulsation with the end-diastolic pneumatic boot and improved ambulatory EKG monitoring after 3 weeks of therapy.
Six normal subjects and 12 patients with clinical angina and significant ST depressions during baseline ambulatory cardiac monitoring were given a single treatment with the end-diastolic pneumatic compression boot, the Circulator Boot. With the use of continuous electrical impedance measurements, multiple hemodynamic variables were followed in five situations: (1) baseline before pumping; during end-diastolic pumping (2) on both legs after every heartbeat, (3) on one leg after every heartbeat, and (4) on both legs on alternate beats; and (5) during pumping on both legs during every systole. Both an increase in venous return and a reduction in afterload likely contributed to significant increases in cardiac output (CO) (51.1 +/- 33.6%), stroke volume (SV) (52.1 +/- 35.6%), change in impedance over time (dZ/dT) (72.0 +/- 68.1%), cardiac index (CI) (51.2 +/- 33.8%), and acceleration index (50.7 +/- 62.2%) during end-diastolic pumping on both legs after every heartbeat. A crucial role for afterload reduction was implied by opposite effects observed on CO, CI, dZ/dT, and SV during systolic pumping. Again, reductions (or a lack of an increase) in ventricular ejection time and/or the preejection period suggested a decrease in afterload during end-diastolic pumping. Pumping on one leg after every beat and on both legs on alternate beats was also effective but less so. After the initial study, the patients were given 14 additional end-diastolic treatments to both legs over 3 weeks. A clinical benefit for the patients was shown by symptomatic improvement in all patients along with a significant reduction in the amount and duration of the RST abnormalities in their ambulatory heart monitoring (p = 0.012).