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Conus arteriosus

The conus arteriosus, also called the infundibulum, is the smooth-walled superior portion of the right ventricle that leads into the pulmonary valve and pulmonary trunk. It forms the right ventricular outflow tract (RVOT). Unlike the trabeculated inflow portion of the right ventricle, the conus arteriosus has thin, smooth myocardium, facilitating laminar blood flow during systole. It lies anterior and superior to the right ventricle and inferior to the pulmonary trunk. Clinically, the conus arteriosus is important in congenital heart diseases such as Tetralogy of Fallot, pulmonary stenosis, and in surgical approaches to the RVOT.

Synonyms

  • Infundibulum

  • Right ventricular outflow tract (RVOT)

  • Pulmonary conus

Function

  • Provides a smooth muscular channel for blood ejection from the right ventricle to the pulmonary valve

  • Prevents turbulent flow, ensuring efficient right ventricular outflow

  • Serves as a transition zone between the trabeculated ventricle and the pulmonary trunk

  • Plays a role in cardiac conduction and hemodynamics, as it is adjacent to the septal conduction system

MRI Appearance

T1-weighted images:

  • Appears as a myocardial structure with intermediate signal intensity, similar to ventricular myocardium

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

T2-weighted images:

  • Myocardial wall remains intermediate to low signal

  • Blood flow within the lumen appears as signal void

  • Useful for assessing myocardial wall thickness or pathology (e.g., hypertrophy, tumor infiltration)

Cine MRI (SSFP sequences):

  • Provides real-time dynamic imaging of RV outflow

  • Clearly demonstrates systolic blood ejection through the pulmonary valve

  • Useful in evaluating RVOT obstruction, stenosis, aneurysm, or post-surgical repair (e.g., Tetralogy of Fallot)

  • Phase-contrast sequences quantify flow velocity, stroke volume, and regurgitant fraction

T1 Post-Contrast (Gadolinium-enhanced):

  • Myocardial wall of conus arteriosus enhances similarly to other myocardium

  • Pathological conditions (fibrosis, tumor, inflammation, post-surgical scar) show abnormal delayed enhancement

  • Helpful for detecting post-operative changes or myocarditis

CT Appearance

Non-contrast CT:

  • Seen as a smooth-walled muscular outflow tract anterior to the right ventricle

  • Lumen is hypodense (air/blood density depending on timing)

  • Calcifications are rare but may be seen in post-surgical settings

Contrast-enhanced CT (CT Angiography):

  • Provides excellent visualization of the infundibulum, pulmonary valve, and pulmonary trunk

  • Detects congenital anomalies, RVOT stenosis, aneurysm, or post-repair anatomy

  • Multiplanar and 3D reconstructions are critical for surgical and interventional planning

MRI images

Conus arteriosus anatomy MRI coronal image -img-00000-00000

CT image

Conus arteriosus anatomy ct axial image -img-00000-00000