Chronic upper limb ischemia syndrome is uncommon compared to lower limb ischemia, with several potential causes (e.g., arteriosclerosis, compressive syndromes, arteritis, connective tissue diseases, trauma, and thrombosis). Many patients with upper limb ischemia remain asymptomatic due to arterial collateral vascularization.

Given the wide variety of potential causes for upper limb ischemia, the diagnosis may require different technical approaches. Doppler ultrasound is a non-invasive, accessible, non-radiating technique that provides direct arterial imaging, yielding valuable information on arterial anatomy and hemodynamics.

Some authors have described the reliability of the arterial duplex ultrasound for lower limb assessment using the pedal acceleration time (PAT). The PAT provides real-time hemodynamic physiological information on the entire limb. The acceleration time (AT) is an ultrasound parameter which measures the time elapsed (in milliseconds, ms) from the beginning of the arterial Doppler waveform until the systolic peak, evaluating the morphology of the arterial waveform in real time. In a healthy individual, this time should be short (between 40 - 100 milliseconds), displaying a triphasic waveform with a systolic acceleration, a sudden diastolic fall, and a subsequent anterograde flow at the end of diastole. A more damped wave suggests proximal stenosis and the acceleration time has been correlated to different degrees of foot ischemia.

Notably, the AT parameter has also been studied in other territories, such as the carotid and pulmonary arteries, coronary arteries, and the aorta. Hand acceleration time (HAT) has also been described very recently as a potential tool to assess hemodialysis access-induced ischemia, cardiogenic shock, and subclavian iatrogenic ischemic lesion. However, the HAT has not yet been properly characterized or validated. Our working hypothesis is that the HAT is a useful diagnostic tool for chronic upper limb ischemia.

Inclusion Criteria (healthy volunteers):

• Healthy adult volunteers (≥ 18 years of age).
• No evidence of upper limb arterial disease.
• Who sign the written informed consent.

Exclusion Criteria (healthy volunteers):

• Healthy volunteers unable (at the investigator discretion) to understand or comply with any study-related procedure.
• Healthy volunteers who refuse to participate.
• Those presenting cardiovascular risk factors (e.g., hypertension, diabetes mellitus, dyslipidemia).

Inclusion Criteria (upper limb ischemia patients):

• Adult patients (≥ 18 years of age) with a known diagnosis of chronic upper limb ischemia.
• Who sign the written informed consent.

Exclusion Criteria (upper limb ischemia patients):

• Patients unable (at the investigator discretion) to understand or comply with any study-related procedure.
• Patients who refuse to participate.

The study population will consist of healthy volunteers accompanying patients to the Angiology and Vascular Surgery outpatient clinic visit and patients diagnosed with chronic upper limb ischemia. Both will be required to sign the written informed consent before joining the study.