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Sulcus terminalis of heart

The sulcus terminalis is a shallow vertical groove located on the external surface of the right atrium of the heart. It runs from the anterior aspect of the superior vena cava (SVC) down to the anterior margin of the inferior vena cava (IVC). This groove externally marks the junction between the smooth posterior wall of the right atrium (sinus venarum) and the muscular anterior wall with pectinate muscles.

Internally, the sulcus terminalis corresponds to the crista terminalis, a muscular ridge within the right atrial cavity. This anatomical landmark is important as it indicates the site of the sinoatrial (SA) node, the natural pacemaker of the heart, which lies near the superior end of the sulcus terminalis, close to the SVC.

The sulcus terminalis is clinically relevant for electrophysiological procedures, right atrial surgery, and imaging, as it guides localization of the conduction system and separates atrial structures of different embryological origin.

Synonyms

  • Terminal groove of right atrium

  • Sulcus terminalis atrii dextri

  • External terminal sulcus

Function

  • Serves as an external landmark for the crista terminalis and SA node

  • Marks the division between the sinus venarum (smooth posterior atrium) and pectinate muscle region (anterior atrium)

  • Important guide for electrophysiologists, cardiac surgeons, and imaging specialists

  • Aids in orientation of right atrial anatomy during interventions

MRI Appearance

T1-weighted images:

  • Appears as a thin external groove along the right atrial wall, best inferred by adjacent fat planes

  • Right atrial wall shows low-to-intermediate signal; blood pool appears intermediate to high signal

T2-weighted images:

  • Groove itself not well differentiated; visualized indirectly by right atrial wall contour

  • Adjacent atrial blood pool is hyperintense; wall appears hypointense

  • Useful for detecting adjacent wall thickening, fibrosis, or infiltration

STIR (Short Tau Inversion Recovery):

  • Suppresses fat to highlight pericardial or atrial wall edema

  • Sulcus terminalis remains a subtle external contour landmark

T1 Post-Contrast (Gadolinium-enhanced):

  • Atrial wall enhances homogeneously

  • Helps identify abnormal thickening, fibrosis, or infiltration near the sulcus terminalis and SA node region

CT Appearance

CT Coronary Angiography (CCTA):

  • Sulcus terminalis seen as a subtle external groove along the right atrial wall between SVC and IVC

  • Contrast opacifies the right atrium, allowing recognition of the groove by wall contour

  • High-resolution CT may demonstrate adjacent SA node artery course

  • Relevant in pre-procedural imaging for ablation, device implantation, or right atrial surgery

CT image

Sulcus terminalis of heart CT axial image -img-00000-00000

MRI image

Sulcus terminalis of heart mri axial image