How is acceleration time defined on Doppler waveforms?

• A. From the start of systole to the first systolic peak
• B. From the start of systole to the end of systole
• C. From the end of systole to the first systolic peak
• D. From the start of diastole to the first systolic peak

Answer: (A)

Acceleration time is the interval from the onset of systolic upstroke to the first systolic peak velocity on the Doppler waveform. It measures how quickly blood accelerates as systole begins. A short acceleration time indicates brisk upstroke with low downstream resistance, while a longer acceleration time points to proximal resistance or obstruction delaying the rise to peak. This is different from the duration of systole or from diastole, and is distinct from deceleration time, which is measured after the peak as flow decelerates.