Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in clinical practice, affecting over 37 million people worldwide. Characterised by chaotic, disorganised electrical activity in the atria of the heart, AF produces an irregular and often rapid heart rate that disrupts normal blood flow dynamics. While the condition is most commonly associated with stroke and heart failure, its consequences extend well beyond the chest. The foot and lower limb represent a particularly vulnerable territory — one where the downstream effects of AF can manifest in ways that are painful, disabling, and, if unrecognised, limb-threatening.
The Haemodynamic Foundation
To understand how AF harms the lower limb, it is important to first appreciate the haemodynamic disturbances it creates. In normal sinus rhythm, coordinated atrial contraction contributes approximately 20–30% of ventricular filling. In AF, this “atrial kick” is lost, reducing cardiac output and creating sluggish, turbulent blood flow — particularly within the left atrial appendage. This stagnant pool of blood is a prime environment for thrombus formation. When these clots dislodge and travel through the arterial system, they can lodge in peripheral vessels, precipitating one of the most feared lower limb emergencies: acute limb ischaemia.
Acute Limb Ischaemia: A Vascular Emergency
Acute limb ischaemia (ALI) is perhaps the most dramatic and immediately life-threatening way in which AF impacts the lower limb. Studies consistently demonstrate that AF is responsible for 20–50% of all cases of ALI due to embolic events. The embolus typically originates from a thrombus in the left atrial appendage and travels distally, often lodging at arterial bifurcations — most commonly at the femoral bifurcation, the popliteal trifurcation, or in the tibial vessels of the lower leg.
The clinical presentation follows the classic “six Ps”: pain, pallor, pulselessness, paraesthesia, paralysis, and perishing cold (poikilothermia). In the foot specifically, these signs present with striking clarity. The foot becomes white or mottled, cold to the touch, and exquisitely painful, before progressing — if untreated — to numbness and weakness as ischaemia affects nerve and muscle. Time is tissue: without revascularisation within four to six hours, irreversible ischaemic damage and gangrene may follow. Amputation rates in embolic ALI remain significant even with prompt surgical or catheter-based intervention.
Chronic Peripheral Arterial Disease and AF
Beyond acute embolic events, AF is increasingly recognised as an independent risk factor for chronic peripheral arterial disease (PAD). PAD involves progressive narrowing of the arteries supplying the lower limbs, typically through atherosclerosis. AF shares many of the same risk factors — hypertension, diabetes, obesity, smoking — but also contributes to PAD through its own mechanisms, including chronic low-grade inflammation, endothelial dysfunction, and a prothrombotic state.
In people with both AF and PAD, the clinical picture in the lower limb is compounded. Intermittent claudication — cramping pain in the calf, thigh, or buttock provoked by walking and relieved by rest — is the hallmark of moderate PAD. As the disease advances, rest pain develops, often worst in the foot at night. The foot may exhibit dependent rubor (redness when the foot is lowered), pallor on elevation, and loss of hair and subcutaneous tissue. In its end stage, critical limb ischaemia produces non-healing ulcers and gangrene, most commonly on the toes, heel, or the dorsum of the foot.
The Role of Anticoagulation and Its Complications
The cornerstone of stroke and embolism prevention in AF is anticoagulation therapy, most often using direct oral anticoagulants (DOACs) or warfarin. While these medications protect against thromboembolism, they carry an inherent bleeding risk — and the lower limb is not exempt. Spontaneous haematomas, bleeding into joints (haemarthrosis), and significant bruising can all occur in the lower limb in patients on anticoagulation. Minor foot trauma — a stubbed toe, an ill-fitting shoe, a small cut — can become a major bleeding episode requiring medical attention.
Furthermore, anticoagulated patients with AF who also have PAD present a therapeutic dilemma. Antiplatelet agents are traditionally used in PAD management, yet combining them with anticoagulants significantly increases haemorrhagic risk. Decisions around antithrombotic therapy in such patients must carefully balance the risk of limb-threatening thrombosis against catastrophic bleeding.
Venous Consequences and Oedema
AF-related reduction in cardiac output and right heart dysfunction can promote venous congestion and peripheral oedema. The feet and ankles are the most gravity-dependent regions of the body and are therefore among the first to swell when cardiac output is impaired. Pitting oedema in the feet and lower legs is a common and often distressing finding in people with AF and co-existing heart failure. Persistent oedema compromises tissue integrity, increases the risk of skin breakdown, and creates an environment conducive to venous ulceration and infection.
Neuropathy, Wound Healing, and the Diabetic Foot
Many patients with AF also carry a diagnosis of type 2 diabetes — a condition that independently damages peripheral nerves and small blood vessels. In these individuals, the cumulative effect of AF-related vascular impairment superimposed on diabetic neuropathy and microangiopathy is particularly dangerous. Reduced protective sensation means foot injuries may go unnoticed. Impaired blood flow means wounds heal poorly. Combined, these factors dramatically increase the risk of diabetic foot ulceration, deep infection, and lower limb amputation.
Clinical Vigilance and Podiatric Care
The lower limb and foot consequences of AF demand a multidisciplinary approach. Cardiologists must communicate embolism risk clearly; vascular surgeons must be alert to embolic ALI; and podiatrists play a pivotal role in the regular assessment and preventive care of the AF patient’s feet. Routine foot examination — checking pulses, skin integrity, temperature, capillary refill, and sensation — can detect early vascular compromise before it becomes irreversible.
Patient education is equally vital. People living with AF should be counselled to inspect their feet daily, wear well-fitted footwear, avoid going barefoot, and seek prompt attention for any wound, colour change, or new pain in the lower limb.
Atrial fibrillation is far more than a heart rhythm disorder. Through embolism, arterial disease, venous congestion, and the systemic effects of impaired cardiac function, it imposes a substantial burden on the foot and lower limb. Recognising and managing these downstream consequences — with the same urgency given to stroke prevention — is essential to preserving limb function and quality of life in the millions of people living with this condition.