Normal Coronary Sinus Dimensions
The normal adult coronary sinus diameter on echocardiography measures approximately 5-10 mm at its termination in the right atrium, with the structure typically measuring 20-60 mm in length. 1, 2
Echocardiographic Measurements
Standard Dimensions
- Maximum diameter (at termination): 9.6 ± 2.6 mm in anatomic studies, which correlates with echocardiographic measurements 2
- Length: External length ranges from 20.5-58.8 mm (mean 38.2 ± 8.6 mm), with internal length ranging from 16.3-49.6 mm (mean 34.5 ± 8.9 mm) 2
- Caliber: Approximately 1 cm in normal adults, though this varies throughout the cardiac cycle 2, 3
Measurement Technique
- Optimal imaging view: The coronary sinus is best visualized in the apical two-chamber view using zoom M-mode recordings for precise caliber measurement 1, 3
- Alternative views: The structure can also be imaged in the parasternal right heart inflow view and appears as a small tubular sonolucency in the posterior atrioventricular groove 1, 3
- Timing considerations: Maximal coronary sinus caliber occurs during ventricular systole, while the structure narrows during atrial contraction in patients with sinus rhythm 1, 3
Cross-Sectional Imaging Findings
CT and MRI Characteristics
- Normal morphology: The coronary sinus appears as a tubular structure located in the posterior atrioventricular sulcus in 98% of cases 2, 4
- Shape variations: Two primary shapes exist—funnel-shaped (82%) and tubular/cylindrical (18%) 2
- Width variation: The coronary sinus is widest at its termination into the right atrium and progressively narrows toward its origin 2
Clinical Context and Pathologic Dilatation
When to Suspect Abnormality
- Mild dilatation: Patients with poor left ventricular systolic function may show mild coronary sinus dilatation beyond the normal 10 mm range 1
- Marked dilatation: Greater dilatation suggests persistent left superior vena cava, with huge dilatation occurring when this anomaly is accompanied by absence of a right superior vena cava 1, 4
- Diagnostic confirmation: Injection of sonicated saline (agitated saline) into left and right arm veins helps confirm venous anomalies when coronary sinus dilatation is present 1
Physiologic Variations
- Cardiac cycle changes: The coronary sinus demonstrates dynamic caliber changes throughout the cardiac cycle, narrowing during atrial contraction in sinus rhythm but remaining static in atrial fibrillation 1, 3
- Heart failure effects: Congestive heart failure with inferior vena cava plethora causes attenuation of normal coronary sinus narrowing during atrial contraction 1, 3
- Cardiac hypertrophy: Hearts with increased weight (365-675 gm) show increased coronary sinus volume (1.76 ± 0.73 cc) compared to normal weight hearts (1.26 ± 0.45 cc) 5
Common Pitfalls to Avoid
- Do not confuse normal dynamic changes with pathology: The coronary sinus normally contracts with atrial systole and dilates during ventricular systole—absence of this pattern suggests atrial fibrillation or elevated central venous pressure, not necessarily structural abnormality 1, 3
- Recognize anatomic coverage: The coronary sinus is covered by left atrial muscles in 96% of hearts, which can affect visualization and measurement 2
- Account for valvular structures: The Thebesian valve covers the coronary sinus ostium an average of 41% in normal hearts (26% in enlarged hearts), which may affect measurement accuracy 5