Hand Acceleration Time (HAT) Assessment Before and After Creating an Arteriovenous Fistula (AVF)

Overview

The main objectives of this observational study are to compare the results of the sonographic parameter hand acceleration time (HAT) measured before and after creating an arteriovenous fistula (AVF) for hemodialysis and assess if it is associated with the incidence of hemodialysis access-induced distal ischemia (HAIDI). The secondary objectives are to study the incidence of HAIDI in patients intervened for the creation of an AVF in the last 6 months, study the AVF permeability at 6 months, and study the AVF-related complications at 6 months.

As the name suggests, hemodialysis access-induced distal ischemia (HAIDI) is an ischemic syndrome affecting the hand in the context of vascular access for hemodialysis. It is caused by the inability of the arterial tree to accommodate and vasodilate after the creation of an arteriovenous fistula (AVF). Furthermore, upper limbs with previously asymptomatic or paucisymptomatic arterial stenoses may suffer from higher blood flow demand after AVF is performed, thus giving rise to ischemic symptoms. HAIDI affects 5-10% of AVF patients with a brachial fistula and less than 1% of those with a radio-cephalic fistula. The clinical presentation consists of hand hypoperfusion symptoms, which can be classified into four degrees of severity, according to Fontaine's classification. Notably, it is most commonly a chronic entity, starting approximately one month after creating the AVF. The diagnostic work-up is often based on non-specific clinical signs and symptoms, such as coldness, paleness, trophic lesions, and absent/weak distal pulses. Complementary non-invasive tests to measure hand perfusion include determining the baseline and post-AVF compression digital pressures, digital-brachial index (DBI), plethysmography, and digital oxygen saturation. Nonetheless, no consensus exists on their reference values to diagnose HAIDI, and the definitive diagnosis often requires performing invasive procedures (arteriography). Performing a duplex ultrasound (DUS) may be useful and provide valuable information. In the context of HAIDI, it may help us assess the proximal arterial integrity, define whether it is a high or low-flow fistula, and establish the distal arterial waveform. One interesting DUS parameter is the acceleration time (AT), which measures the time elapsed (in milliseconds) from the beginning of the arterial Doppler waveform until its systolic peak. It allows for a real-time assessment of the arterial waveform morphology. Some authors have successfully described the reliability of the AT for lower limb assessment (pedal acceleration time, PAT), while others have used it in other arterial territories (e.g., carotid, pulmonary, and coronary arteries and the aorta). Markedly, the hand acceleration time (HAT) has also been described very recently as a potential tool to assess cardiogenic shock, subclavian iatrogenic ischemic lesions, and HAIDI. In the context of HAIDI, it may help us assess the proximal arterial integrity, define whether it is a high or low-flow fistula, and establish the distal arterial waveform. Therefore, we hypothesized that HAT is a sensitive method for detecting HAIDI in patients with an AVF.