Citation, DOI, disclosures and article data
Citation:
Savi F, Feger J, "To and fro" waveform. Reference article, Radiopaedia.org (Accessed on 11 Oct 2024) https://doi.org/10.53347/rID-193670
The "to and fro" waveform, or bidirectional flow, is a pulsed Doppler waveform of alternating flow direction in which blood enters and exits a confined space through the same opening 1.
Related pathology
The "to and fro" pattern is a characteristic flow pattern in the setting of a pseudoaneurysm (false aneurysm) seen on Doppler ultrasound examination 1-3, with "to" representing blood moving toward the pseudoaneurysm sac in systole, while "fro" represents blood leaving the sac in diastole 2.
Clinical importance
The appearance of a pseudoaneurysm on B-mode is similar to a noncommunicating hematoma, so it is necessary to demonstrate bidirectional flow in the neck of the aneurysm for definitive diagnosis 3.
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1. Kim E, Sharma A, Scissons R et al. Interpretation of Peripheral Arterial and Venous Doppler Waveforms: A Consensus Statement from the Society for Vascular Medicine and Society for Vascular Ultrasound. Vasc Med. 2020;25(5):484-506. doi:10.1177/1358863x20937665 - Pubmed
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2. Mahmoud M, Al-Saadi M, Abuderman A et al. "To-And-Fro" Waveform in the Diagnosis of Arterial Pseudoaneurysms. World J Radiol. 2015;7(5):89-99. doi:10.4329/wjr.v7.i5.89 - Pubmed
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3. Rozen G, Samuels D, Blank A. The to and Fro Sign: The Hallmark of Pseudoaneurysm. Isr Med Assoc J. 2001;3(10):781-2. - Pubmed
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4. Zierler R & Zierler B. Duplex Sonography of Lower Extremity Arteries. Seminars in Ultrasound, CT and MRI. 1997;18(1):39-56. doi:10.1016/s0887-2171(97)90037-8
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5. Pellerito J & Taylor K. Doppler Color Imaging. Peripheral Arteries. Clin Diagn Ultrasound. 1992;27:97-112. - Pubmed
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