ORIENTATION VIEWING HEART IN AXIAL CT AND MRI

ORIENTATION: VIEWING HEART IN AXIAL CT AND MRI Orientation of heart in axial CT and MRI RV LV RA LA 5 CHAMBERED HEART? 4 CHAMBERED HEART 20 MINUTE ANATOMY VIDEOS No sinner is ever saved after the first twenty minutes of a sermon - Mark Twain INVERTED Y SHAPE?

ORIENTATION: THORACIC CONTENTS ANTERIOR VIEW Esophagus Trachea R. Brachiocephalic V. Sup. Vena Cava Structures at Root of Lung Left Int. Jugular V. Subclavian V. AORTA Pulmonary Trunk diaphragm R L

POSTERIOR VIEW INCLUDING TRACHEA, ESOPHAGUS 1) Arch of Aorta Esophagus, Thoracic duct 2) Pulmonary Arteries 2 a) Trachea (bifurcation) Order similar to root of Lung diaphragm L 3) Pulmonary Veins IVC R

HEART IS ON LEFT: REASON: ROTATED SO LEFT ATRIUM IS IN MIDLINE Right Ventricle anterior Left Atrium - receives Pulmonary Veins symmetrically from both sides Left Pulmonary Veins RV LA Right Pulmonary Veins

POSTERIOR VIEW: KNOW SEQUENCE SVC 1) Arch of Aorta 2) Pulmonary Arteries Pulmonary Veins 3) Pulmonary Veins IVC

ANTERIOR VIEW AT TOP (SUPERIORLY) - VEIN IN FRONT OF ARTERIES Left Brachiocephalic Vein Brachiocephalic Trunk Right Brachiocephalic Vein SVC ANTERIOR VIEW Left Common Carotid A Left Subclavian A Arch of Aorta Reason: All venous blood drains to Right Atrium

ANTERIOR VIEW PULMONARY TRUNK - arises from Right Ventricle; crosses anterior to Ascending Aorta; then branches Arch of Aorta Ascending Aorta RV Pulmonary Trunk - from Conus Arteriosus

Conus Arteriosus

CONUS ARTERIOSUS EXTENDS TOWARD LEFT; THEN PULMONARY TRUNK BIFURCATES RA Conus Arteriosus Y LA PULMONARY TRUNK ON LEFT IN AXIAL SECTIONS RV LV

AORTA ARISES IN MIDDLE OF HEART RA LA RV AXIAL SECTIONS LOOK LIKE 5 CHAMBERED HEART LV

POSTERIOR VIEW: KNOW SEQUENCE SVC 1) Arch of Aorta 2) Pulmonary Arteries Pulmonary Veins L 3) Pulmonary Veins IVC R

ORIENTATION: VIEWING HEART IN AXIAL CT AND MRI RV Orientation of heart in axial CT and MRI RA LV LA

LV RV LA RA R CT, MRI VIEW HEART FROM BELOW IMAGE FLIPPED VERTICALLY * - AORTA IN CENTER OF HEART L

START AT DIAPHRAGM Diaphragm Inferior vena cava Muscles of ventricles Esophagus Azygous vein R Thoracic (descending) aorta L

Right ventricle Interventricular septum Inferior vena cava Left ventricle Esophagus Azygous vein Thoracic (descending) aorta R 2 CHAMBERED HEART - ventricles only L

Right ventricle Right atrium Left ventricle Left atrium Esophagus R Thoracic (descending) aorta 4 CHAMBERED HEART! L

Right ventricle Right atrioventricular orifice Right atrium Interventricular septum Left ventricle Right pulmonary vein Left atrioventricular orifice LA Left atrium Thoracic (descending) aorta Azygous vein R 4 CHAMBERED HEART! Left pulmonary vein L

Right ventricle * - AORTA - arising from Vestibule Right atrium Left ventricle Left atrium Right pulmonary vein Azygous vein Esophagus R 5 CHAMBERED HEART? Left pulmonary vein Thoracic (descending) aorta L

Right ventricle Superior vena cava Ascending aorta RV Azygous vein R Left main bronchus RIGHT VENTRICLE EXTENDS TO LEFT L

Right ventricle to Pulmonary Trunk Ascending aorta Y Left pulmonary artery Y Superior vena cava Right pulmonary artery Carina at tracheal bifurcation R PULMONARY TRUNK BRANCHES Thoracic (descending) aorta L

Superior vena cava R Trachea Arch of aorta Esophagus L

Superior vena cava Left subclavian artery Trachea Scapula Spinal cord Esophagus R L

Left brachiocephalic vein Right lung Brachiocephalic trunk Left common carotid R Trachea Left subclavian artery Esophagus L LEFT BRACHIOCEPHALIC VEIN CROSSES ANTERIORLY

Summary - Orientation of heart in CT and MRI is complex; rarely appears to have 4 chambers. 1. Position and Orientation of heart - Heart is rotated and tilted so Right Ventricle is anterior and inferior; this makes functional sense; as a result, Left Atrium is located in midline and receives blood symmetrically from Pulmonary Veins (low pressure). 2. Sequence of Structures Inferior to Superior - Pulmonary Veins, Pulmonary artery, Arch of Aorta. 3. Pulmonary artery - arises from Conus arteriosus (Infundibulum) of Right Ventricle; ascends toward left and crosses anterior to Aorta; Pulmonary artery then bifurcates (appears Y shaped in axial CT and MRI). 4. Aorta - arises from Left Ventricle and first courses in middle of heart (Heart appears to have 5 chambers in axial CT and MRI at this level). 5. Order of Structures in Superior Mediastinum - Veins (R and L Brachiocephalic) are anterior to Arteries (Brachiocephalic, L Common Carotid, L Subclavian) arising from Arch of Aorta.

REMEMBER: ANATOMICAL DETAILS ARE COMPLEX AND DIFFICULT TO LEARN BUT PATIENTS CAN DIE FROM 'MINOR DETAILS' OF ANATOMY.