Normative Reference Values of Cardiac Output by Pulsed-Wave Doppler Echocardiography in Adults

Cardiac output (CO) is routinely assessed by pulsed-wave Doppler echocardiography, yet reference values in adults are lacking. We aim to establish normative values of CO and cardiac index (CI) by pulsed-wave Doppler-echocardiography and to analyze their relation with gender and age in nonobese and obese adults. We included 4,040 adults (mean age: 55 years, 53% women, 950 obese [body mass index ≥30 kg/m²]) with normal blood pressure, no history of cardiovascular disease, and normal transthoracic echocardiography. Normative reference CO and CI values for were calculated in 3,090 nonobese patients by quantile regression. CO normal limits were lower in females than in males (lower limit: 3.3 vs 3.5 L/min, upper limit: 7.3 vs 8.2 L/min). CI normal limits were identical for both genders (lower limit: 1.9 L/min/m², upper limit: 4.3 L/min/m²). Although the relation of CO to age was weak and observed only in women, CI of both genders was not influenced by age. CO of obese patients was significantly greater than that of their nonobese counterparts. CI of obese patients was not influenced by age and gender and was not significantly different than that of nonobese patients (lower limit 1.8 L/min/m², upper limit 4.1 L/min/m² for both genders). In conclusion, in a large adult population we establish normative reference values for CO and CI measured by Doppler-echocardiography. CI is a remarkably stable parameter that is not influenced by age, gender, and body size and should be used to define low- and high-output states.