Continuous-wave Doppler interrogation in valvular heart disease: pearls and pitfalls

Continuous-wave Doppler (CWD) echocardiography remains a cornerstone in the haemodynamic assessment of valvular heart disease, providing critical insights into transvalvular flow, pressure gradients, and lesion severity. Beyond simple velocity measurements, the morphology, timing, intensity, and contour of Doppler waveforms contain rich physiological information that can refine diagnosis, risk stratification, and clinical decision-making. However, these signals are frequently underutilized or misinterpreted because accurate interpretation requires meticulous acquisition technique, understanding of Doppler physics, and integration with haemodynamic principles. This review discusses the fundamental principles underpinning CWD interrogation, including the Doppler and Bernoulli equations, and highlights the strengths, limitations, and common pitfalls encountered in clinical practice. We systematically review the application of CWD in aortic, mitral, tricuspid, and pulmonary valve disease, focusing on waveform morphology, velocity and gradient interpretation, pressure half-time, velocity-time integral, dimensionless indices, and Doppler signal intensity analysis. Particular emphasis is placed on complex haemodynamic scenarios, including low-flow states, dynamic obstruction, mixed valve disease, severe regurgitation, prosthetic valves, and discordant findings between Doppler and invasive measurements. The review also explores emerging concepts such as Doppler signal pixel intensity analysis and the future role of artificial intelligence in integrating high-density Doppler information into physiology-driven interpretation frameworks. Ultimately, Doppler echocardiography should not be viewed merely as a source of numerical outputs, but as a comprehensive bedside physiological tool requiring critical interpretation within the broader clinical and haemodynamic context.