The Integration of Doppler Ultrasound With Two-Dimensional Echocardiography and the Noninvasive Cardiac Hemodynamic Revolution of the 1980s

In the 1970s, as cardiac imaging matured from M-mode to two-dimensional echocardiography, investigators in Norway showed that continuous-wave Doppler ultrasonography could be used to accurately measure the mean gradient and pressure half-time for stenotic mitral valves. In the 1980s, continuous-wave Doppler was validated for measurement of the pressure gradient across stenotic aortic valves, and pulsed-wave Doppler combined with two-dimensional echocardiographic imaging was validated for noninvasive measurement of stroke volume and cardiac output. The combination of stroke volume measurement and measurement of the time-velocity integral of flow through the aortic valve was then validated as a means to accurately calculate valve area for patients with stenotic aortic valves or aortic prostheses. This integration of cardiac Doppler ultrasonography with two-dimensional echocardiographic cardiac imaging led to a revolution in noninvasive hemodynamic evaluations, which have replaced invasive hemodynamic evaluations in surgical decision making for most patients with native or prosthetic valvular stenosis.