ECO

Exercise Cardiac Output (ECO^®)

Measurement of hemodynamic and metabolic responses to stress using the cardiopulmonary stress test (CPX) is important in the evaluation and management of patients with chronic heart failure (CHF). Parameters measured during the CPX test enable clinicians to index disease severity, to evaluate the effectiveness of therapy, helps in the estimation of risk for morbidity and mortality, and is used to help guide development of safe and effective patient specific exercise prescriptions^(1,2). For all these purposes, the most widely used parameter obtained during CPX is the maximal oxygen uptake (peak VO2) because it closely parallels the cardiac output (CO) response to exercise⁽³⁾. In the figure to the right, one can see that minute-by-minute changes in VO2 are closely correlated with changes in CO. However, peak VO2 can be difficult to determine in some patients^(4,5), can be difficult to define^(4-6), is influenced by motivation, and varies considerably in some patients with similar cardiac function^(7-10). The CPX is therefore underutilized in the cardiology community, except mainly at transplant centers where it is paramount to the evaluation of a patient’s eligibility for heart transplantation. Recently, it was found that direct measures of cardiac function, in specific Peak Cardiac Power and Peak Cardiac Output are the most powerful independent predictors of outcome in heart failure patiens. These parameters were found to be of higher correlation to CHF than were VO2 related parameters⁽¹¹⁾

The feasibility and utility of Exercise Cardiac Output (ECO^®) using Bioreactance to determine cardiac response to stress in CHF patients have been shown in large scale studies of heart failure employing exercise testing ^(12-15). 

Recently, it was shown that NICOM-derived hemodynamics were related to heart failure clinical endpoints occurring in the year following initial testing and were able to provide prognostic information with similar significance as did cardiopulmonary stress testing. The combined information from both modalities was synergistic and further enhanced that derived by each modality alone⁽¹⁶⁾.

Select findings:

ECO^® measures the peak cardiac output and cardiac power able to be generated at the patient’s maximally tolerated level of exertion Allows measurement of total peripheral resistance and its changes during exercise Helps in the assessment of the relative contributions of chronotropic, inotropic and vasodilatory reserve to exercise intolerance Provides direct indexes of Cardiac Reserve (defined as the ratio between peak CO and resting CO) Implementing ECO^® to determine Peak Cardiac Output and Peak Cardiac Power offers several advantages: Direct determination of cardiac function in rest and stress conditions Test is simple to perform and does not require patient cooperation (as is the case for VO2 measurement), does not require special equipment apart from a NICOM CO monitor and a bike or treadmill exercise system A minute-by-minute report is generated (see figure to the right) that allows for immediate interpretation of test results