What is the most likely cause of acute left arm swelling in an elderly female patient with a history of hypertension (high blood pressure) and gastroesophageal reflux disease (GERD), who has a normal mammogram?

Acute Left Arm Swelling in an Elderly Female: Deep Vein Thrombosis

The most likely cause of acute left arm swelling in this elderly female patient is upper extremity deep vein thrombosis (UEDVT), which requires immediate venous duplex ultrasound examination and consideration of anticoagulation therapy.

Primary Diagnostic Consideration: Upper Extremity DVT

The clinical presentation of acute unilateral arm swelling in an elderly patient strongly suggests UEDVT, which accounts for approximately 25% of patients screened by venous duplex ultrasound who present with arm swelling or arm pain 1. Immediate venous duplex ultrasound of the affected upper extremity is the diagnostic test of choice 1.

Key Clinical Features Supporting UEDVT

• Acute onset of unilateral arm swelling is the hallmark presentation, occurring in 63% of UEDVT cases 1
• The left-sided location is consistent with May-Thurner-like compression syndromes affecting the upper extremity 2
• Elderly females with cardiovascular risk factors (hypertension) have increased thrombotic risk 2

Critical Risk Assessment

Measure blood pressure in both arms immediately to detect significant discrepancies (>15-20 mmHg difference), which could indicate subclavian artery stenosis or other vascular pathology 3, 4. This is essential because:

• Patients with hypertension have increased risk of subclavian artery involvement 3
• Inter-arm BP differences >15-20 mmHg are abnormal and require further vascular evaluation 3

Serious Complications Requiring Immediate Assessment

Pulmonary Embolism Risk

UEDVT carries a 9% incidence of objectively confirmed pulmonary embolism, with a 1-month mortality rate of 6.4% 1. This is not insignificant and mandates:

• Immediate assessment for dyspnea, chest pain, or tachypnea
• Low threshold for CT pulmonary angiography if any cardiopulmonary symptoms present 1

Concurrent Lower Extremity DVT

16% of patients with UEDVT have concurrent lower extremity DVT 1, necessitating bilateral lower extremity venous duplex ultrasound even with isolated arm symptoms 1.

Diagnostic Workup Algorithm

Immediate Evaluation (Within Hours)

1. Venous duplex ultrasound of the left upper extremity - diagnostic standard for UEDVT 1
2. Bilateral arm blood pressure measurements - to exclude subclavian stenosis 3, 4
3. Focused neurological examination - assess for arm weakness, drift, coordination deficits, facial asymmetry, and speech abnormalities to exclude stroke 4
4. ECG - evaluate for atrial fibrillation as embolic source or acute coronary syndrome 4

Laboratory Assessment

• Complete blood count to assess for thrombocytosis or anemia 3
• Comprehensive metabolic panel including renal function (serum creatinine with eGFR) 3
• D-dimer if ultrasound unavailable immediately (though negative D-dimer does not exclude UEDVT in high pretest probability)

Secondary Evaluation if UEDVT Confirmed

• Bilateral lower extremity venous duplex - due to 16% concurrent DVT rate 1
• Chest imaging - assess for occult malignancy or mediastinal mass causing venous compression 1
• Consider thrombophilia workup if no obvious precipitating factors identified 2

Alternative Diagnoses to Exclude

Neurological Causes

Despite normal mammogram, acute stroke remains in the differential until definitively excluded with proper vascular imaging 4. The American Heart Association emphasizes that small vessel disease and lacunar infarcts may not present with obvious focal deficits 5.

• If BP ≥180/110 mmHg with acute neurological symptoms, this constitutes hypertensive emergency requiring immediate hospitalization 4
• Do not rely solely on CT scan - proceed to MRI if CT negative but clinical suspicion remains high, as MRI is more sensitive for acute ischemia 4

Lymphedema

Chronic lymphedema from prior surgery or radiation would present with gradual onset rather than acute swelling, making this less likely.

Cellulitis or Superficial Thrombophlebitis

These typically present with erythema, warmth, and tenderness along superficial veins, which should be evident on examination.

Management Based on Findings

If UEDVT Confirmed

80% of patients with UEDVT receive anticoagulation therapy 1:

• Initiate therapeutic anticoagulation immediately unless contraindications exist
• Options include low molecular weight heparin, unfractionated heparin, or direct oral anticoagulants
• Duration typically 3-6 months, longer if provoked by malignancy 1

If Hypertensive Emergency Identified

The European Society of Cardiology recommends initiating combination antihypertensive therapy immediately with RAS blocker plus dihydropyridine calcium channel blocker, targeting systolic BP 120-129 mmHg if tolerated 4.

Special Considerations for Elderly Patients

• Assess orthostatic BP changes - orthostatic hypotension occurs in approximately 7% of men over 70 and carries 64% increased age-adjusted mortality 6
• Avoid excessive diastolic BP lowering (keep DBP >60 mmHg) as it increases fall risk 4
• Screen for frailty using validated clinical tests 4

Critical Pitfalls to Avoid

• Do not assume benign etiology based on normal mammogram alone - UEDVT and stroke remain possible 4, 1
• Do not delay ultrasound - venous duplex is readily available and non-invasive 1
• Do not miss bilateral assessment - check both arms for BP and consider bilateral lower extremity ultrasound 3, 1
• Do not overlook medication review - assess for hormone therapy (like Premarin in the case example), which increases thrombotic risk 2
• Do not forget PE screening - maintain low threshold given 9% PE incidence 1

GERD Relevance

While GERD is present in this patient's history, it does not directly cause arm swelling. However, GERD and hypertension frequently coexist as comorbid conditions 7, and both share risk factors such as obesity 8. The GERD history is relevant only if considering atypical chest pain as part of the symptom complex, but does not explain isolated arm swelling 9.