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Sinoatrial nodal artery

The sinoatrial nodal artery (SANa) is the principal arterial branch supplying the sinoatrial (SA) node, the heart’s natural pacemaker. Its origin is variable: in about 60–65% of individuals, it arises from the right coronary artery (RCA) near its origin; in about 30–35%, it arises from the left circumflex artery (LCx), and less commonly from both (dual supply).

The artery typically courses posteriorly and superiorly, encircling the superior vena cava or passing along the atrial wall to reach the SA node located at the junction of the superior vena cava and right atrium. Because of its critical role in perfusing the SA node, occlusion of this artery can lead to arrhythmias, sinus node dysfunction, or ischemia-related conduction disturbances.

Synonyms

  • SA nodal artery

  • Sinoatrial artery

  • Arteria nodi sinuatrialis

Function

  • Provides the sole or primary arterial blood supply to the SA node

  • Maintains viability of the cardiac pacemaker tissue, enabling normal sinus rhythm

  • Contributes to atrial perfusion, particularly in the upper right atrium

  • Variations in its origin are clinically relevant in coronary interventions and CABG surgery

Branches

  • Typically a single branch directed to the SA node

  • May have collateral branches to the right atrium

  • Rarely, dual SA nodal arteries exist, supplying the node from both RCA and LCx

MRI Appearance

T1-weighted images:

  • Lumen appears as a signal void (black) due to flowing blood

  • Vessel wall hypointense, surrounded by intermediate-signal atrial myocardium

T2-weighted images:

  • Artery remains a flow void

  • Adjacent edema or inflammation (e.g., myocarditis, pericarditis) appears hyperintense

MRA (Magnetic Resonance Angiography):

  • Contrast-enhanced MRA best visualizes the small-caliber SA nodal artery

  • Identifies origin (RCA vs LCx), course, and variations

  • 3D reconstructions useful for pre-interventional mapping

CT Appearance

Non-contrast CT:

  • Vessel not well visualized, except if calcified plaques are present

CT Coronary Angiography (CCTA):

  • Best non-invasive modality for imaging the SANa

  • Demonstrates origin, course, and termination at SA node

  • Identifies atherosclerosis, stenosis, occlusion, anomalous origin, or dual supply

  • Crucial in planning CABG, PCI, and ablation procedures

MRI image

Sinoatrial nodal artery mri axial image

CT image

Sinoatrial nodal arter anantomy CT axial image -img-00000-00000