Vascular Occlusive Syndromes of the Upper Extremity

In most patients, the dominant blood supply to the hand is provided by the superficial palmar arch, a continuation of the ulnar artery, and to a lesser degree by the deep palmar arch, a continuation of the radial artery. Minor blood supply to the hand is provided by intraosseous channels via the radial and ulnar bones, as well as by the median artery, which is present in a minority of patients.

In approximately 80% of patients, the deep and superficial palmar arches are connected and are referred to as complete. This results in a dual perfusion supply to the common and proper digital vessels. This is an important attribute of hand vascular architecture, providing collateral blood flow in the event of vascular pathology affecting one of these palmar arches.

The vascular supply to the thumb is unique and includes sources directly from the radial artery and from the deep and superficial arch. In addition to its direct supply, the radial artery gives rise to a large dorsal artery, which passes distally to supply the thumb. The palmar blood supply to the thumb is provided by the princeps pollicis artery, which is derived from the first palmar metacarpal artery, the deep arch, the wrist dorsal metacarpal artery, or a terminal branch of the superficial palmar arch.

The four terminal arteries to the thumb are the ulnar and radial palmar arteries and the ulnar and radial dorsal arteries. Vessels have been categorized arbitrarily on the basis of their diameter, with macrovessels measuring 100 μm or greater in diameter and microvessels measuring less than 100 μm.

Human skin provides the termination of the microcirculation, composed of nutritional papillary capillary beds, as well as nonnutritional thermoregulatory vessels. Interestingly, in normal physiology, 80-90% of microcirculation passes only through thermoregulatory vessels.

Multiple factors determine vascular flow, including the following:

• Environmental events
• Metabolic demands
• Sympathetic nervous tone
• Local and circulating humoral mediators

Vasoconstriction can result from increased sympathetic tone or alpha-adrenergic–stimulating humoral mediators, such as norepinephrine. In contrast, vasodilation may be prompted by parasympathetic tone (inhibiting the sympathetic tone), release of nitric oxide by endothelial cells, or myogenic autoregulatory mediators arising from increased cellular waste products, such as adenosine.

Considerable interest has been focused on the effect of endothelium on vascular tone, because of its capacity to produce two competing molecules: nitric oxide, a vasodilatory endothelium-derived relaxing factor, and endothelin, a potent vasoconstrictor. Sympathetic nerves typically penetrate the arterial and venous walls, affecting the muscularis component at frequent intervals. These nerves travel variable distances in peripheral nerves before entering the perivascular adventitia.

In vasospastic disorders, abnormal vascular control can arise from abnormal receptor expression or from response to agonists, abnormal levels of local humoral mediators, aberrant myogenic and metabolic control mechanisms, and overwhelming sympathetic tone. In contrast, vascular insufficiency may result from physical trauma to vessels, with resulting transection or thrombotic or embolic sequelae.

Ultimate interstitial flow is determined by the pressure gradient across a single vascular lumen, as well as the total (potential) capacity of the arteriolar-capillary-venular bed. Vasospasm, which is observed in hypothenar hammer syndrome and Raynaud disease, may cause pressure gradients to fall below critical levels without affecting the total capacity of the vascular bed.

In contrast, peripheral occlusive diseases, such as those seen in scleroderma, impede the pressure gradient as well as the total potential capacity of the vascular bed. This distinction is important because it affects indications for treatment and prognosis after surgery or other interventions.

Environmental factors, such as external toxins and ambient temperatures, affect vascular patency. This is of interest because the interaction between the external environment and the internal autonomic system has dynamic interplay. For example, for a period following digit replantation, the external temperature may affect inflow pressures at the amputation site but will not affect the vessels of the amputated part, because the sympathetic system of the adventitia will have been disrupted.

Causes of vascular compromise include the following:

• Acute trauma
• Chronic modalities, such as repetitive microtrauma
• Systemic disease processes involving metabolic or autoimmune processes
• Atherosclerotic occlusive disease
• Acute occlusions related to plaque rupture and thrombosis or embolization
• Physiologic vasospasm in response to shock

Patient age influences the propensity for vascular occlusive disorders. Raynaud disease affects women aged 30-50 years. Males are affected bimodally, with different disorders being prominent in young males as opposed to middle-aged men. Acute traumatic vascular disorders are more common in younger males because of the high incidence of motor vehicle accidents in this age group. In contrast, repetitive traumatic vascular disorders occur most often in middle-aged men who are employed in manual-type labor. In the latter case, the labor usually involves handheld vibrating tools that cause chronic trauma.

The onset of vascular occlusive disorders is affected by the sex of the patient. As noted, Raynaud disease affects women aged 30-50 years, whereas males are affected in a bimodal fashion. 

No current findings identify any one race as having a particular propensity for developing vascular occlusive syndromes involving the upper extremities.

Vaso-occlusive diseases give rise to variable morbidity in patients, depending on the pathophysiology of the underlying condition. Vascular flow is determined by multiple factors, including environmental events, metabolic demands, sympathetic nervous tone, and local or circulating humoral mediators.

When vascular flow is compromised, a range of symptoms, including dysesthesias, paresthesias, pallor, cold intolerance, and ulceration associated with tissue necrosis, may be present; thus, vaso-occlusive diseases can result in significant morbidity. Unlike the lower extremity, however, the upper extremity has a robust collateral network that allows for sufficient blood flow despite occlusive disease; thus, patients may be asymptomatic even in the setting of acute occlusion. 

Causes of vascular compromise include acute trauma or chronic modalities, such as repetitive microtrauma and systemic diseases involving metabolic processes, autoimmune processes, or both. Environmental factors as trivial as arsenic exposure may lead to severe, chronic peripheral vasospasm.