Embryology of the Heart

The Common Vein

Copyright 2009

Introduction

The “twist” in the story is long and complicated, with important implications in congenital heart disease – beyond the scope and need of this anatomy text. In the normal setting we make the following observations: The blue-blooded chambers tend to be rightward, anterior, and slightly superior in position. One of the main structural differences between the right and left sides is that the right ventricle has a separate and distinct outflow chamber – the RVOT or infundibulum. There is an oblique and leftward pointing orientation of the outflow chamber , so that the pulmonary valve lies to the left and superior to its counterpart, the aortic valve. During embryological development, the RVOT, MPA (Main Pulmonary Artery), and aorta twist around each other to result in the structural positioning and relationships of the valves.   It always seemed odd that the pulmonary valve coming from the right sided chambers lay to the left of the aortic valve.  Under-twisting or over-twisting results in malpositioning of the great vessels in relation to their ventricles with consequent drastic hemodynamic results. Transposition of the great vessels is one such example. The left ventricle arises from the mesodermal germ layer. By the 22nd day of development there is a single heart tube made of an innner endocardial tube and a surrounding myocardial mantle. Starting at the 4th week, the interventricular septum develops to form the distinct left ventricle. This is formed by the inferior endocardial atrioventricular cushion and left conus swelling.

Straight Tube

The heart starts as a straight tube.  In this stick diagram inflow is through the sinus venosus (maroon) which will evolve into the atria.  Blood then  passes through  the single common atrioventricular valve (short pink horizontal  region) which will evolve into the tricuspid and mitral valves.  The next vertical limb (red) represents the portion of the tube that will develop into the ventricles.  The horizontal orange bar represents the conus – or muscular bundle that lies under the truncus arteriosus. (royal blue).  The truncus arteriosus will evolve into the aorta and pulmonary artery.

01477b03 heart cardiac straight tube primitive heart embryology Davidoff art drawing Davidoff MD

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01488b02 heart cardiac straight tube d loop D loop primitive heart embryology right ventricle RV sinus venosus atria atrium A-V cushions conus arteriosus truncus arteriosus drawing Davidoff Art Davidoff MD Davidoff art drawing Davidoff MD

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01477e03 heart cardiac d loop left ventricle is born to the left sepatation truncus arteriosus conus arteriosus ventricles atrium atria primitive heart embryology Davidoff art drawing Davidoff MD

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01492b04L heart cardiac right atrium left atrium right venricle left ventricle atrioventricular canal conus arteriosus truncus arteriosus aortic arches RA LA RV LV AVC embryology Davidoff drawing Davidoff MD

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01492b06b heart cardiac left atrium right atrium coronary arteries coronary ostia A-V canal atrioventricular canal conus arteriosus trunccus arteriosus D loop left ventricle right ventricle embryology Rv LV MV TV LA RA aorta pulmonary artery normal drawing Davidoff art Davidoff MD 01492b11 01492b06b 01492b05b01 01492b1201492b14

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01492b12 heart cardiac left atrium right atrium mitral valve tricuspid valve coronary arteries coronary ostia A-V canal atrioventricular canal conus arteriosus trunccus arteriosus D loop left ventricle right ventricle embryology Rv LV MV TV LA RA aorta pulmonary artery normal drawing Davidoff art Davidoff MD 01492b11 01492b06b 01492b05b01 01492b1201492b14

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01492b14 heart cardiac left atrium right atrium mitral valve tricuspid valve coronary arteries coronary ostia A-V canal atrioventricular canal conus arteriosus trunccus arteriosus D loop left ventricle right ventricle embryology Rv LV MV TV LA RA aorta pulmonary artery normal drawing Davidoff art Davidoff MD 01492b11 01492b06b 01492b05b01 01492b1201492b14

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01806 heart cardiac bilateral conus outflow tract infundibulum aorta pulmonary artery D-loop anatomy embryology Courtesy Ashley Davidoff drawing

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06362b01 heart cardiac bilateral conus outflow tract infundibulum aorta pulmonary artery D-loop RV LV conoventricular defect bilateral conus atrioventricular endocardial cushion mitral valve anatomy embryology subaortic conus subpulmonary conus fibrous continuity MV Courtesy Ashley Davidoff Davidoff drawing

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07427b10 heart cardiac bilateral conus outflow tract infundibulum aorta pulmonary artery D-loop RV LV conoventricular defect anatomy embryology subaortic conus subpulmonary conus fibrous continuity anterior leaflet posterior leaflet of the mitral valve MV Courtesy Ashley Davidoff Davidoff drawing

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06370b04 heart cardiac bilateral conus outflow tract infundibulum aorta pulmonary artery D-loop RV LV conoventricular defect bilateral conus atrioventricular endocardial cushion mitral valve anatomy embryology subaortic conus subpulmonary conus fibrous continuity mitral valve MV Courtesy Ashley Davidoff Davidoff drawing

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07427b02 heart cardiac bilateral conus outflow tract infundibulum aorta pulmonary artery D-loop RV LV conoventricular defect anatomy embryology subaortic conus subpulmonary conus fibrous continuity anterior leaflet posterior leaflet of the mitral valve MV Courtesy Ashley Davidoff Davidoff drawing

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06373b05 heart cardiac aorta mitral valve anatomy embryology resorbtion of subaortic conus fibrous continuity mitral valve with aortic valve position shape of aorta MV Courtesy Ashley Davidoff Davidoff drawing

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06376b04 heart cardiac pulmonary artery growth of the subpulmonary conus pulmonary valve infundibulum RV right ventricle RA right atrium IVC inferior vena cava tricuspid valve anatomy embryology position shape of pulmonary artery Courtesy Ashley Davidoff Davidoff drawing

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31149c.8 78 year old female infundibulum right ventricle RVOT right ventricular outflow tract aortic valve aortic sclerosis calcification enlarged left atrium heart normal conotruncal relationship cardiac Courtesy Ashley Davidoff MD copyright 2009

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07523e.8s normal relationship between the aorta and pulmonary artery aorta pulmonary artery conus right ventricular outflow tract MRI T1 weighted Courtesy Ashley Davidoff MD

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The “twist” story is graphically demonstrated in the following axial MRI images, cutting from inferior to superior as we follow the RV sinus, and RVOT around the aorta. Image 1 shows the triangular RV sinus anterior and to the right of the left ventricle. Image 2 is more superior and shows the RVOT making its way leftward and anterior to the aorta. Image 3 shows the final, distal, and leftward position of the RVOT just below the pulmonary valve. The next set of images with color overlay may be helpful. Courtesy of Ashley Davidoff M.D. 32093

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27467c01 aorta pulmonary valve pulmonary artery SVC size position normal CTscan Davidoff MD

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07954eW.800 aorta aortic valve infundibulum RVOT right ventricular outflow tract position relation MRIscan Davidoff MD

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06394c01L.800s embryology bilateral conus DORV growth resorbtion normal mitral to aortic continuity transposition D transposition double outlet right ventricle Davidoff art copyright 2009 all rights reserved

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01488b02b01 heart cardiac straight tube l loop L loop primitive heart embryology right ventricle RV sinus venosus atria atrium A-V cushions conus arteriosus truncus arteriosus drawing Davidoff Art Davidoff MD copyright 2009 Davidoff art drawing Davidoff MD

01477e03b01s

01477e03b01s heart cardiac straight tube l loop L loop primitive heart embryology right ventricle RV sinus venosus atria atrium A-V cushions conus arteriosus truncus arteriosus drawing Davidoff Art copyright 2009 Davidoff art drawing Davidoff MD

06394c02Ls

06394c02Ls embryology bilateral conus DORV growth resorbtion normal mitral to aortic continuity transposition L transposition corrected transposition double outlet right ventricle Davidoff art copyright 2009 all rights reserved

 

Common Conotruncal Abnormalities

86778 01639 01639d02 01639d04 01639f03.jpg Anterior aorta = Transposition Copyright 2009 Courtesy Ashley Davidoff MD all rights reserved

 

Powerpoint

Applied Anatomy of the Heart in Congenital Heart Disease