Acceleration time and maximal acceleration in lower extremity peripheral artery disease: Measurements and application

Acceleration time (AT) is a pulsed-wave Doppler ultrasound parameter reflecting the time interval between the onset of systolic flow and peak systolic velocity. Although described several decades ago, AT has remained underutilized in routine practice. Recent evidence, however, has highlighted its diagnostic and clinical value in lower extremity peripheral artery disease (PAD), particularly in situations where the ankle-brachial index is unreliable. This manuscript provides a comprehensive and practical overview of AT, focusing on its physiological basis, technical requirements for accurate measurement, and clinical applications in PAD. We detail standardized measurement conditions, emphasize common pitfalls, and underline the importance of adequate Doppler acquisition parameters to ensure reproducibility. The diagnostic performance of AT is reviewed across different arterial levels, showing its ability to detect significant upstream stenoses and to exclude hemodynamically relevant disease with high sensitivity and specificity. In advanced PAD, particularly chronic limb-threatening ischemia, the concept of maximal acceleration time (ATmax), defined as the highest AT measured in distal pedal arteries, is discussed as a reliable marker of severe hypoperfusion. ATmax shows strong correlation with toe pressure and has demonstrated prognostic value following revascularization. In addition, maximal systolic acceleration (ACCmax) is complementary Doppler-derived parameter, reflecting the rate of systolic flow acceleration and providing further hemodynamic insight although with higher technical demands. Overall, AT, ATmax and ACCmax are simple, reproducible, and non-invasive markers that enhance vascular ultrasound assessment of PAD. Their systematic integration into clinical practice may improve diagnostic accuracy, disease severity evaluation, and patient management.