8.2 Upper Extremity Occlusive Disease & Vasospastic Disorders

8.2 Upper Extremity Occlusive Disease & Vasospastic Disorders

Upper extremity arterial pathology encompasses a diverse spectrum of atherosclerotic, inflammatory, traumatic, and vasospastic conditions. Unlike the lower extremities—where atherosclerotic luminal narrowing dominates clinical practice—the upper extremities frequently present with non-atherosclerotic conditions such as large-vessel vasculitis, small-vessel thromboangiitis, occupational repetitive trauma, and autoimmune microvascular vasospasm. Systematic vascular diagnostic testing allows clinicians to distinguish between fixed anatomical obstructions and reversible functional vasospasm.

Etiologies of Upper Extremity Arterial Occlusive Disease

Arterial obstruction in the upper extremity can be categorized into large-vessel proximal disease, thromboembolic events, and specialized inflammatory vasculitides:

1. Atherosclerotic Occlusive Disease

• Prevalence & Localization: Atherosclerosis accounts for the vast majority of proximal upper extremity arterial lesions. The single most common site is the origin of the proximal left subclavian artery, where hemodynamic shear stress and ostial curvature promote atheroma formation.
• Clinical Signs: Patients typically present with exertional arm fatigue, cramping (arm claudication), coolness, and weakness during repetitive overhead tasks. Proximal stenosis frequently induces subclavian steal syndrome, characterized by retrograde flow in the ipsilateral vertebral artery to siphon blood toward the ischemic arm.
• Interarm Systolic Pressure Discrepancy: A resting systolic blood pressure difference $> 15 - 20\text{ mmHg}$ between the two arms strongly suggests hemodynamically significant stenosis ($> 50\%$) or occlusion of the subclavian or brachiocephalic artery on the side with the lower pressure.

2. Thromboembolic Occlusions

• Cardiogenic Emboli: Upper extremity arteries are the destination for approximately $15\% - 20\%$ of all peripheral arterial emboli. Cardiogenic sources include atrial fibrillation, left ventricular mural thrombi following myocardial infarction, dilated cardiomyopathy, and prosthetic valve vegetations. Emboli characteristically lodge at major arterial bifurcations: the brachial bifurcation into the radial and ulnar arteries is the most frequent site.
• Artery-to-Artery Emboli: Embolic showers can arise proximally from ulcerated subclavian atheromas or from subclavian/axillary aneurysms (frequently secondary to thoracic outlet compression). Distal microemboli lodge in the palmar and digital arteries, presenting as acute "blue finger syndrome" with severe resting pain and splinter hemorrhages.
• Acute Limb Ischemia (The 6 P's): Acute embolic occlusion produces sudden, dramatic limb hypoperfusion manifested by: Pain, Pallor, Pulselessness, Paresthesia, Paralysis, and Poikilothermia (coolness). This constitutes a surgical vascular emergency.

3. Non-Atherosclerotic Inflammatory Vasculitides

Hypothenar Hammer Syndrome (HHS)

Hypothenar hammer syndrome is an uncommon but clinically high-yield traumatic vascular condition encountered in occupational and sports medicine:

• Anatomic Pathophysiology: At the wrist, the ulnar artery emerges from the forearm and enters the hand through Guyon's canal (bounded by the pisiform bone medially and the hook of the hamate laterally). In this anatomic space, the ulnar artery lies superficial, shielded only by skin, subcutaneous fat, and the thin palmaris brevis muscle. It rests directly over the hard, unyielding bony prominence of the hook of the hamate.
• Mechanism of Injury: Repetitive blunt percussion or sustained vibrating trauma to the hypothenar eminence—such as using the heel of the palm as a mallet to hammer, push, or strike hard objects (mechanics, carpenters, metalworkers, roofers, baseball catchers, golfers, tennis players)—compresses the ulnar artery directly against the hook of the hamate.
• Vascular Damage: Chronic repetitive trauma fractures the internal elastic lamina and media of the ulnar artery, precipitating intimal proliferation, transmural degeneration, ulnar artery thrombosis, or true/false (pseudo) aneurysm formation.
• Clinical Presentation:
  • Patients present with ischemic pain, cold sensitivity, paresthesias, palmar pallor, and painful digital ulcerations.
  • Because the superficial palmar arch and digital branches to the medial hand originate directly from the ulnar artery, symptoms and digital microembolization characteristically involve the fourth (ring) and fifth (little) fingers.
  • A pulsatile, tender mass may be palpated over the hypothenar eminence if an aneurysm is present.
• Duplex Ultrasound Findings:
  • Localized aneurysmal dilatation or complete thrombotic occlusion of the ulnar artery directly adjacent to the hook of the hamate.
  • Color Doppler demonstrates turbulent, swirling "yin-yang" flow within an aneurysm or absent color filling with hypoechoic intraluminal thrombus in acute occlusion.
  • Interrogation of the digital arteries reveals absent or severely attenuated, high-resistance or flatline flow in the 4th and 5th digits secondary to distal embolization.

Vasospastic Disorders: Primary vs. Secondary Raynaud

Vasospastic disorders of the upper extremity are characterized by episodic, exaggerated, reversible digital ischemia triggered by cold exposure or emotional stress. Clinically, attacks manifest as the classic triphasic color change:

1. Pallor (Chalky White): Acute, intense vasoconstriction and spasm of digital arteries and precapillary arterioles, arresting digital capillary inflow.
2. Cyanosis (Blue / Purple): Capillary blood pools and stagnates, with local tissues extracting oxygen, leaving desaturated hemoglobin.
3. Rubor (Deep Red / Flushing): Spasm resolves, initiating reactive hyperemia with rapid arterial reperfusion, throbbing pain, tingling, and cutaneous burning.

Differentiation: Primary Raynaud Disease vs. Secondary Raynaud Phenomenon

Differentiating primary from secondary vasospasm is one of the most critical diagnostic determinations on the CCI RVS examination:

Cold-provocation assessment and limitations

A history of cold- or stress-triggered digital color change is central to evaluation. If a laboratory performs cold-provocation testing, use its validated protocol, patient selection, safety precautions, and standardized baseline/rewarming measurements. Severe ischemia, ulcers, or poor tolerance require appropriate clinical judgment rather than forcing exposure.

Record baseline digital pressures or PPG waveforms, the maneuver, symptoms, and recovery. Cold causes physiological vasoconstriction in healthy people as well as exaggerated responses in Raynaud presentations. Temperature, medication, autonomic state, technique, and underlying disease affect the response. No universal five-, ten-, or fifteen-minute recovery boundary independently diagnoses primary versus secondary Raynaud.

Primary Raynaud generally lacks tissue injury or evidence of a secondary disorder. Secondary causes include connective-tissue disease and vascular disease; resting waveforms may be normal or abnormal depending on the condition. Abnormal nailfold findings or digital ulcers warrant clinical evaluation, but no single PPG contour establishes the systemic diagnosis. Differentiate fixed obstruction, vasospasm, embolic disease, and technical failure using the entire study.

Pre-Operative Palmar Arch Assessment: The Allen Test

Evaluating the integrity and completeness of the palmar arches is mandatory before procedures that sacrifice or instrument the radial artery:

• Clinical Indications:
  1. Harvesting the radial artery as a bypass conduit for Coronary Artery Bypass Grafting (CABG).
  2. Creating a radiocephalic arteriovenous (AV) fistula (Brescia-Cimino) for hemodialysis access.
  3. Placement of an indwelling radial arterial line for invasive hemodynamic monitoring.

1. Subjective Clinical Allen Test & Its Limitations

• The patient clenches their fist tightly for 30 seconds while the examiner manually compresses both the radial and ulnar arteries at the wrist to exsanguinate the hand.
• The patient opens the hand (avoiding hyperextension), revealing a blanched, pale palm.
• The examiner releases compression from the ulnar artery while maintaining firm compression on the radial artery.
• Interpretation: If the palm reperfuses (turns pink) within $< 5 - 6\text{ seconds}$, ulnar collateralization is considered intact (normal/negative test). If pallor persists for $> 10\text{ seconds}$, the test is abnormal/positive (incomplete arch; radial artery dependence).
• Limitation: The subjective Allen test has an unacceptably high rate of false-positive and false-negative results due to examiner pressure variations, patient hand overextension (which compresses palmar microvessels), and subjective color interpretation.

2. Objective Modified Doppler & PPG Allen Test

To overcome the inaccuracies of the clinical test, vascular laboratories perform an objective modified Allen test using Doppler ultrasound or photoplethysmography (PPG):

Objective PPG Allen Test Protocol:

Step 1: Place PPG sensor on index finger (Digit 2) or thumb (Digit 1).
Step 2: Record baseline pulsatile PPG waveform.
Step 3: Manually compress Radial Artery firmly against the radial styloid.
Step 4: Observe Digit PPG Waveform during compression:
        ├── Waveform Remains Robust / Increases ──► Palmar Arch COMPLETE (Safe to harvest Radial Artery)
        └── Waveform Flatlines / Severely Damps ──► Palmar Arch INCOMPLETE (Radial Dependent - DO NOT HARVEST!)

• Technique:
  1. A PPG sensor is secured to the fleshy pulp of the index finger (second digit) or thumb (first digit), which are the digits most dependent on radial inflow.
  2. A baseline pulsatile waveform is displayed and recorded.
  3. The sonographer applies firm digital pressure to the radial artery at the wrist, completely obliterating radial inflow.
  4. Complete Arch (Intact Ulnar Collaterals): The PPG waveform on the thumb/index finger maintains its pulsatile contour or increases in amplitude during continuous radial artery compression. This confirms that ulnar collateral blood flow travels across the superficial and deep palmar arches to supply the radial digits. This supports collateral flow under the test conditions; it does not guarantee the safety of harvest or ligation without the full surgical assessment.
  5. Incomplete Arch (Radial Dependency): The PPG waveform instantly flatlines or diminishes into a severely damped trace when the radial artery is compressed. This proves that the radial-sided digits rely solely on radial artery inflow and receive no collateral support from the ulnar artery. Harvesting the radial artery in this patient is strictly contraindicated, as it will result in ischemic gangrene and necrosis of the thumb and index finger.
  6. Reciprocal Ulnar Compression: The procedure is repeated by compressing the ulnar artery while monitoring the fifth (little) finger to assess radial collateral flow to the ulnar digits.