Isolated atrial standstill

Isolated atrial standstill (also known as atrial paralysis or atrial quiescence) is an extremely rare cardiac conduction disorder characterized by the complete absence of electrical and mechanical activity in the atria of the heart. In this condition, the atrial myocardium fails to depolarize, meaning the upper chambers of the heart do not contract. On an electrocardiogram (ECG), this manifests as the absence of P waves, a junctional or ventricular escape rhythm, and the inability to stimulate the atria even with direct electrical pacing. The condition primarily affects the cardiac conduction system and can lead to significant hemodynamic compromise. Patients with isolated atrial standstill may present with symptoms related to slow heart rate (bradycardia), including syncope (fainting), dizziness, fatigue, exercise intolerance, and palpitations. Because the atria are not contracting, blood stasis within the atrial chambers increases the risk of thrombus (blood clot) formation, which can lead to thromboembolic events such as stroke. The condition can be partial (affecting one atrium) or total (affecting both atria), and may be persistent or transient. Isolated atrial standstill has been associated with mutations in the SCN5A gene (encoding the cardiac sodium channel Nav1.5) and in some families with connexin-40 (GJA5) gene variants, often following an autosomal dominant or autosomal recessive inheritance pattern depending on the genetic basis. Some cases are also associated with atrial myopathy or fibrosis. Treatment is primarily supportive and includes permanent pacemaker implantation to maintain an adequate ventricular rate, along with long-term anticoagulation therapy to prevent thromboembolic complications. There is currently no curative treatment available for this condition.

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