Doppler Echo Cardiac Output Calculator

The calculation relies on several interconnected physiological formulas. First, Body Surface Area (BSA) is determined using the Mosteller formula: BSA = sqrt(weight * height / 3600). The Cross-Sectional Area (CSA) of the Left Ventricular Outflow Tract (LVOT) is found using the circular area formula: CSA = pi * (LVOTdiameter / 2)^2. Stroke Volume (SV) represents the blood volume ejected per beat and is calculated as: SV = CSA * LVOT_vti. Cardiac Output (CO) translates this to volume per minute: CO = SV * heartRate / 1000. Finally, Cardiac Index (CI) normalizes output to body size: CI = CO / BSA.

Consider an adult patient with a weight of 70 kg and a height of 175 cm. First, calculate BSA = sqrt(70 * 175 / 3600) = sqrt(3.402) = 1.84 m^2. Suppose the measured LVOT diameter is 2.0 cm (0.02 m), yielding a CSA of pi * (2.0 / 2)^2 = 3.14 cm^2. If the LVOT velocity-time integral (VTI) is 20 cm, the Stroke Volume is SV = 3.14 * 20 = 62.8 mL per beat. With a resting heart rate of 75 beats per minute, Cardiac Output is CO = (62.8 * 75) / 1000 = 4.71 L/min. Finally, the Cardiac Index is CI = 4.71 / 1.84 = 2.56 L/min/m^2, indicating normal resting cardiac performance.

Ensure precise caliper placement when measuring the LVOT diameter during mid-systole on a zoomed parasternal long-axis view, as squaring this value magnifies measurement errors. Always trace the modal velocity of the envelope on the pulsed-wave Doppler spectral display carefully to secure an accurate LVOT VTI. When computing indices for pediatric or atypical body habitus populations, double-check that height and weight units align correctly with the formula requirements.