Different noninvasive techniques can be used for evaluating arterial perfusion in the hand, which include measuring the digital-brachial index (DBI), digital arterial pressures, oxygen saturation, and plethysmographic signals [1]. However, despite their availability, none have become the accepted standard for diagnosing chronic ischemia of the upper extremities, likely due to the rarity and etiological diversity of this condition.

In contrast to its lower limb counterpart [2], upper limb vascular diseases (whether acute or chronic) represent <10% of the consultations in vascular surgery settings [1]. Among these, only a minority (around 4%) ultimately require revascularization procedures [3]. The underlying causes of upper extremity ischemia are varied and include atherosclerosis, thoracic outlet syndrome, different forms of vasculitis (such as Takayasu arteritis, giant cell arteritis, and Buerger disease), connective tissue disorders, trauma, unresolved thrombotic events [3,4], and ischemia secondary to vascular access in patients undergoing dialysis [5].

Particularly noteworthy is hemodialysis access–induced distal ischemia (HAIDI), which affects up to 5%-7% of individuals with end-stage renal disease undergoing dialysis via an arteriovenous access [6]. Although chronic upper limb ischemia is rare overall, HAIDI represents a considerable subset within this population. DBI and digital pressures have been investigated extensively in this context, but no clear consensus exists on their diagnostic thresholds or reliability [7-9]. Furthermore, although adaptations of Fontaine’s classification have been proposed for UPPER limb ischemia, corresponding objective testing metrics such as DBI or digital pressure stratification have not been standardized as they have for lower limb disease.

Because of these limitations, imaging modalities such as computed tomography angiography, magnetic resonance angiography, or arteriography are often needed to confirm a diagnosis of upper limb arterial occlusive disease [3,10]. On the other hand, duplex ultrasound (DUS) is a noninvasive, dynamic tool that can visualize the entire upper extremity arterial tree, and prior studies have successfully described the anatomical characteristics of the hand vasculature by using this approach [11].

One specific DUS parameter—acceleration time—has emerged as a potential indicator of distal arterial compromise. Acceleration time quantifies the interval in milliseconds between the onset of the systole and the systolic peak on Doppler waveform analysis, providing real-time insight into arterial compliance and resistance [12]. The diagnostic applicability of acceleration time has been established in different vascular beds, particularly in the pedal arteries for assessing lower limb ischemia (pedal acceleration time) [13-15]. Additionally, acceleration time has been studied in arterial territories such as the carotid arteries [16], pulmonary arteries [17], and the aorta [18]. Some authors have applied this concept to the upper extremity, measuring what is referred to as the hand acceleration time (HAT) [19-21]. However, current data are limited, mostly consisting of small case series or anecdotal reports, and no formal characterization or validation of HAT has been conducted to date.

In light of this, our study aims to describe a reproducible technique for measuring HAT by using DUS and to assess its diagnostic potential by comparing patients with chronic upper limb ischemia to healthy control participants. We hypothesized that HAT is a useful diagnostic tool for chronic upper limb ischemia, considering that ischemic hands would exhibit prolonged acceleration time values due to impaired perfusion, which would broaden the arterial spectral Doppler waveform. This study aims to describe the technique for assessing hand perfusion through HAT while quantifying it in patients with chronic upper limb ischemia and healthy volunteers.

As of June 2023, 30 participants were enrolled in the study, comprising 15 patients and 15 healthy volunteers, resulting in a total of 15 ischemic and 30 nonischemic hands. Data analyses were concluded in late November 2023, and results were sent for publication in February 2024. The manuscript containing the results was accepted in May 2024 and published online in July 2024, becoming available in PubMed in December 2024 [23]. This study protocol was submitted for publication in July 2024 to enhance transparency and offer comprehensive methodological insight into the HAT technique. No modifications were made to the original protocol used to guide the results, and no further analyses beyond those reported in the published study are planned.

This study protocol outlines the design and methodology of a cross-sectional, prospective, and descriptive investigation into HAT as a diagnostic marker for chronic upper limb ischemia. Although the sequence of the publication is atypical (ie, protocol being published after the dissemination of the corresponding results [23]), it reflects the intent to foster transparency and provide guidance for the future applications of this technique.

To date, the clinical application of HAT has been explored only in a handful of case reports. Notably, one series described its application in 4 patients with HAIDI and associated trophic lesions, where HAT values declined after revascularization, coinciding with symptom resolution [19]. In another case report, palmar DUS was used to guide the need for reperfusion in a patient with subclavian artery disruption and scapulothoracic dissociation, accurately assessing the function of an extra-anatomic bypass [20]. Finally, HAT was successfully used to detect early signs of posthemorrhagic shock state [21]. These preliminary findings suggest that HAT may hold promise as a rapid, noninvasive diagnostic tool for assessing upper limb perfusion and might potentially complement or even replace other noninvasive techniques such as DBI, digital pressures, and plethysmography (which are currently standardized in this context). Nonetheless, this will require future robust prospective studies addressing the sensitivity, specificity, and predictive values of HAT in comparison to these existing modalities.

Herein, we propose a structured and reproducible method for measuring HAT by using DUS in both patients with chronic upper limb ischemia and healthy volunteers. Although the study was not powered to establish definitive diagnostic thresholds, the reported ranges might serve as preliminary reference for future research. Given its descriptive nature and limited sample size, stratifying HAT values across different types of arterial disease was deemed impractical, as subgroup analysis would likely reduce (if not mislead) interpretability. However, this study does describe the anatomical location of the affected arteries, bearing in mind that HAT values tend to be elevated in ischemic hands regardless of the disease site when compared to healthy limbs.

Markedly, this study might incur information bias since the HAT results, like most sonographic measurements, are examiner-dependent; however, if it were the case, it would be a systematic bias (since the same examiner performed all the measurements), yielding similar probabilities of occurrence in all study participants. The small sample size does not allow analysis adjustments for more than one variable and acts as another limitation. Further, generalizing its results to a broader population requires caution, given these limitations; however, they may serve as guidance for conducting future large-scale studies.

Transcutaneous oxygen pressure (TcPO₂) and skin perfusion pressure are valuable tools for assessing tissue perfusion, particularly in the context of lower limb ischemia, and exploring their correlation with HAT in cases of upper limb ischemia would be of interest. However, although TcPO₂ has been well validated for lower limb assessments, no consensus currently exists regarding reference values or diagnostic thresholds for hand ischemia. Based on our clinical experience—despite having previously used TcPO₂ routinely for lower limb evaluation—we found the test to be time-consuming, technically challenging for the upper extremities, and frequently inconclusive in guiding clinical decision-making. Consequently, we progressively discontinued its use in our daily practice. Given these limitations and the lack of validated upper-limb parameters, TcPO₂ was not included in this study. Nevertheless, future research examining the correlation between HAT and alternative perfusion metrics such as TcPO₂ or skin perfusion pressure may contribute to further validating HAT as a diagnostic tool for hand ischemia.

On the other hand, the rich collateral circulation of the hand—arising primarily from the radial, ulnar, and interosseous arteries—plays a significant role in modulating perfusion and may influence arterial Doppler waveforms, potentially affecting HAT results. The HAT protocol was intentionally designed to assess the overall arterial supply to the hand and to provide an indirect measure of collateral flow. To ensure consistency and reliability, we selected 4 arterial segments for evaluation: 2 branches from the radial artery and 2 from the ulnar artery. This choice was based on anatomical studies indicating relatively low interindividual variability in these segments, thereby supporting reproducibility across participants while adequately capturing the contributions of both major vascular axes.