THE WAY WE TEACH.. .
Anatomy of the Coronary Artery Svstem
Med Teach Downloaded from informahealthcare.com by University of Newcastle on 01/09/15 For personal use only.
JON M. ROGERS, JOHN L. ROBINSON, PHILIP K. FULKERSON and JOHN M. STANG, with the artistic assistance of STEVEN MOON
A simple model to enhance understanding of the threedimensional anatomy of the human epicardial coronary artery circulation is discussed and potential instructive applications reviewed. The chambers of the heart are visualized as being related to one another as in a pair of opposed hands, which can be rotated to demonstrate the various structures as viewed in different angles of obliquity. A thorough knowledge of the normal human coronary arterial circulation is essential in the interpretation of angiographic procedures. In addition to providing an insight into the functional significance of disease noted at coronary arteriography, a clear understanding of epicardial coronary artery anatomy helps to give a firm grasp of the pathological processes associated with occlusive atherosclerotic coronary artery disease. For example, precise anatomical localization of infarction patterns based on regional blood supply by divisions of the coronary arteries is much more easily conceptualized and taught if there is a sound understanding of the course and distribution of the normal coronary arteries. The same applies to appreciating the significance of the occurrence of papillary muscle dysfunction and ischemic rupture of papillary muscle heads, with resultant severe mitral regurgitation in the face of acute myocardial infarction. Familiarity with the anatomy of the coronary circulation also enhances understanding of ventricular septal defects occurring in the setting of acute ischemic disease. However, the ability of medical students and medical house officers to grasp the anatomical relationships of normal coronary arteries is often hampered by the inability to construct mentally the normal coronary circulation in three dimensions and to view the course of the coronary arteries in relationship to other central cardiac structures such as the atria and ventricles as well as to the Jon M. Rogers, MD is Fellow and Clinical Instructor, John L. Robinson, MD is Associate Professor, Philip K. Fulkerson, MD is Associate Professor, John M. Stang, MD is Assistant Professor at the Division of Cardiology, and Steven Moon, MA is Clinical Instructor at the Division of Biomedical Illustration, Departments of Medicine and Allied Medical Professions, Ohio State University College of Medicine, Ohio State University Hospital, 410 West 10th Avenue, Columbus, Ohio 43210. USA.
Medical Teacher Vol 6 No 2 1984
great vessels. This problem becomes readily apparent when learners view opacified epicardial coronary arteries in various projections obtained at coronary cineangioPPhYWe have developed a teaching aid to help students and house officers conceptualize the anatomical locations of the epicardial coronary arteries. This method simply uses the hands as a model of the heart chambers and the great vessels, and may be applied on the wards or in the cine viewing room.
Method The intact human heart, when viewed in situ in the anterior projection, is comprised largely of the right atrium and right ventricle (Figure 1). In order to reproduce the anatomical relationships of the ventricles and atria in the human heart, we visualized these chambers as being related to one another in the same way as a pair of opposed hands. The left (or posterior) hand is skewed off the right (anterior) hand by one centimetre so as to duplicate the anterolateral aspect of the left ventricle as viewed in the anterior projection. The right thumb is abducted to 90 degrees to represent the superior vena cava (for later illustrating the course of the sinus node artery), and the left thumb is flexed at 45 degrees at the distal interphalangeal joint and opposed to the head of the left second metacarpal bone to represent the root of the aorta and the right and left coronary cusps. The nail of the left coronary cusp, and the anterior aspect of the distal phalanx of the left thumb represents the right coronary cusp (Figure 2). In this model the dorsal aspect of the right hand is related to the anterior and right lateral location of the right atrium, and the fingers of the right (anterior) hand are related to the right ventricle. The location of the left ventricle is represented by the left fingers in a lateral and posterior position to the right fingers (which occupy the location of the right ventricle). The superior vena cava is represented by the abducted right thumb, and the left thumb representation of the aortic root and cuspal structures is as noted above. In this relationship, when viewed from any oblique angle, the interventricular groove is composed of the groove between the two opposed sets of 57
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Medical Teacher Vol 6 No 2 1984
Med Teach Downloaded from informahealthcare.com by University of Newcastle on 01/09/15 For personal use only.
Medical Teacher Vol 6 No 2 1984
59
Med Teach Downloaded from informahealthcare.com by University of Newcastle on 01/09/15 For personal use only.
Med Teach Downloaded from informahealthcare.com by University of Newcastle on 01/09/15 For personal use only.
fingers, as shown in Figure 1. This relationship is important in conceptualizing the course of the left coronary anterior circulation and the path of the posterior intraventricular groove branch of the right coronary artery. One can use a piece of paper held between the opposed hands to illustrate the location of the interventricular septum as well as the interatrial septum. The two sets of knuckles in the model also represent the atrioventricular groove, and the continuity between the anterior and posterior sets of knuckles in the model emphasizes the concept of the continuous circular nature of the base of the heart where the annuli of the atrioventricular valves are contained. In using the model for demonstration we have found it helpful for the instructor to oppose the hands of a volunteer and to point out the course of the coronary arteries and cardiac chambers. This makes it easier to rotate the two hands in concert to demonstrate the various structures, as viewed in different oblique angles, when teaching in small groups.
right coronary artery (now in its distal portion) runs in the atrioventricular groove inferiorly, and at right-angles to the groove it gives rise to the posterior interventricular groove artery. One can rotate the opposed set of hands by 90 degrees (Figure 3) to illustrate the course in the interventricular groove of that artery, which supplies the inferobasalar portion of the interventricular septum. This view is also helpful in demonstrating the intersection of the atrioventricular and interventricular grooves, and also serves to locate the origin of the atrioventricular node artery, which arises at right-angles to the plane of the inferior portion of the heart and runs through the interventricular septum to nourish the atrioventricular node. At the crux of the heart, the distal right coronary artery runs further in the atrioventricular groove (posterior or left-hand set of knuckles) to give rise, occasionally, to posterolateral branches which generally run in parallel to the grooves between the fingers of the left hand to supply the posterolateral aspect of the left ventricle.
Course of the Normal Coronary Circulation
Lcfr Coronary A d q
Right Coronary Artery
The course of the epicardial left coronary artery is shown in Figures 4 and 5. The left main coronary artery is given off from the left coronary cusp as represented by the nail of the left thumb, and it divides into anterior and posterior trunks. The anterior trunk courses in the interventricular groove formed by the two opposed hands and running anterolaterally. One or more diagonal branches depart from the anterior trunk and ramify over the lateral surface. of the left ventricle, as represented by the lateral aspect of the left fingers. The first septal perforator branch departs at right angles to the left anterior descending artery and courses in the plane between the two opposed hands, while the remainder of the left anterior descending coronary artery, in its midportion and distal segments, are represented by the artery shown in Figure 4. The posterior circulation, however, arises at the great division of the left main coronary artery and curves posteriorly outside of the atrioventricular groove (and out of the posterior or left hand row of knuckles) to give rise to the obtuse marginal branch, which ramifies over the posterolateral high base of the left ventricle. As the true posterior trunk travels inferiorly and to the right, several large posterolateral branches are given off, which roughly parallel the course of the grooves between the left fingers and which functionally supply the large portion of the posterolateral aspect of the left ventricle. At this point, the posterior trunk drops into the atrioventricular groove, again represented by the posterior set of knuckles, to become the true circumflex artery in its mid and distal portions and may develop a large branch at the crux cordis to form a posterior interventricular groove artery in the case of left coronary circulation dominance (Figure 5).
Using the above model the right coronary artery arises from the right coronary cusp, represented by the anterior aspect of the distal phalanx of the left thumb. It courses anteriorly over the head of the right second metacarpal bone to run in the anterior atrioventricular groove, represented by the anteriorly placed knuckles of the right hand. The conus branch of the right coronary artery leaves the main right coronary artery early in its course and curves superiorly over the first right knuckle to nourish the right ventricular outflow tract. The next major branch of the right coronary artery, the sinus node branch, arises from the right proximal coronary artery and curves superiorly and to the right to wind around the superior vena cava to supply the sinus node and the left and right atria by means of smaller branches. Using the thumb to represent the superior vena cava and the dorsum of the right hand to represent the right atrium, the course of the sinus node node artery can be demonstrated (Figure 2) as well as the anatomical location of the sinus node. As the right coronary courses in the atrioventricular groove (represented by the knuckles of the right hand) several branches are given off at right angles to the midportion of the right coronary artery which course anteriorly over the dorsum of the right hand. These branches represent right ventricular branches and run parallel to the grooves between the individual fingers of this hand. Several smaller right atrial branches are given off perpendicular to the mid-right coronary artery to run anteriorly over the right atrium, represented by the dorsum of the right palm. As the mid-right coronary artery courses inferiorly and anteriorly through the atrioventricular groove, the acute marginal branch is given off which courses in the imaginary angle formed between the diaphragm and the anterior aspect of the right ventricle. Following the departure of the acute marginal branch, the 62
Discussion As discussed above, the model is a simple representation of the cardiac chambers and the great vessels; it is quickly learned and may be used in group teaching to show the Medical Teacher Vol 6 N o 2 1984
Med Teach Downloaded from informahealthcare.com by University of Newcastle on 01/09/15 For personal use only.
course of the normal epicardial coronary arteries. It is useful in teaching coronary anatomy in the cineangiographic viewing suite, when native coronary artery injection is filmed in different angles as shown in Figure 6. Here, the opposed hand model is viewed in the left anterior oblique projection and clearly demonstrates the three major coronary arterial divisions as they appear angiographically in this projection. The other major feature of‘this model is the ease with which the concept of collateral circulation may be taught once the basic concepts of coronary anatomy have been mastered. Right-to-left collaterals arising from the distal right to circumflex the coronary artery as well as the posterior interventricular groove artery to the distal left descending coronary artery may be easily demonstrated in this manner as well as left-to-right collaterals in the opposite direction of flow.
Nutrition in Medical Education, The Teaching of Nutrition to Doctors at the undergraduate and postgraduate level is a controversial area and was judged to be an important subject for the first British Nutrition Foundation Task Force. The Monograph: Nutrition in Medical Education’ is the outcome of this Task Force. The Report recommends that: 0 Teaching of nutrition should begin at the preclinical stage and continue throughout medical training. 0 Teaching should include basic scientific aspects of nutrition but also demonstrate its practical application. 0 The objective may be best achieved by ensuring that in each medical school one academic unit takes a special interest in nutrition. 0 There should be one person appointed as a coordinator for nutrition education in each medical school, in the relevant department. 0 There is a need for continuing postgraduate training in nutrition, particularly for the general practitioner and community physician. 0 In district hospitals there is a need for a department to organize a ‘nutrition team’ to provide a nutrition advisory service for the hospital and community. 0 Closer associations in research and teaching are needed between medical schools and nonmedical centres of research. 0 There is a strong case for the Royal Colleges to appoint a working party to review the scope for medical students and junior doctors of education in nutrition.
‘Gray J (ed). Nufrifiun in medical educafiun. London: Tht British Nutrition Foundation, 1983. Price f 1.95.
Medical Teacher Vol 6 No 2 1984
UPDATE POSTGRADUATE CENTRE SERIES BOOKLETS CURRENTLY AVAILABLE Allergy 3rd ed. Anaerobic Infections Angina Chronic Bronchitis 2nd ed. Contraception Disorders of the Oesophagus 2nd ed. Disorders of the Stomach & Duodenum Eczema & Psoriasis 5th ed. Pain The Premenstrual Syndrome Wound Treatment and Care in General Practice SEMINAR SERIES Control of Hospital-Acquired Infections Pain Peptic Ulcer
FORTHCOMING PUBLICATIONS Acne 2nd ed. Asthma Chronic Bronchitis Diabetes Eczema & Psoriasis Epilepsy Occupational Dermatology The Menopause Practical Aspects of Dermatology Respiratory Tract Infection Rheumatoid Arthritis Terminal Care Ulcerative Colitis Urinary Tract Infection SEMINAR SERIES Allergy 2nd ed. Asthma Breast Cancer Hypertension 2nd ed. Pain 2nd ed. Peptic Ulcer 2nd ed. Schizophrenia Each Booklet costs f2.00 (in. p&p) cheques or postal orders to:
UPDATE PUBLICATIONS LIMITED 33134 Alfred Place. London WC1E 7DP
Anatomy of the Coronary Artery Svstem
Med Teach Downloaded from informahealthcare.com by University of Newcastle on 01/09/15 For personal use only.
JON M. ROGERS, JOHN L. ROBINSON, PHILIP K. FULKERSON and JOHN M. STANG, with the artistic assistance of STEVEN MOON
A simple model to enhance understanding of the threedimensional anatomy of the human epicardial coronary artery circulation is discussed and potential instructive applications reviewed. The chambers of the heart are visualized as being related to one another as in a pair of opposed hands, which can be rotated to demonstrate the various structures as viewed in different angles of obliquity. A thorough knowledge of the normal human coronary arterial circulation is essential in the interpretation of angiographic procedures. In addition to providing an insight into the functional significance of disease noted at coronary arteriography, a clear understanding of epicardial coronary artery anatomy helps to give a firm grasp of the pathological processes associated with occlusive atherosclerotic coronary artery disease. For example, precise anatomical localization of infarction patterns based on regional blood supply by divisions of the coronary arteries is much more easily conceptualized and taught if there is a sound understanding of the course and distribution of the normal coronary arteries. The same applies to appreciating the significance of the occurrence of papillary muscle dysfunction and ischemic rupture of papillary muscle heads, with resultant severe mitral regurgitation in the face of acute myocardial infarction. Familiarity with the anatomy of the coronary circulation also enhances understanding of ventricular septal defects occurring in the setting of acute ischemic disease. However, the ability of medical students and medical house officers to grasp the anatomical relationships of normal coronary arteries is often hampered by the inability to construct mentally the normal coronary circulation in three dimensions and to view the course of the coronary arteries in relationship to other central cardiac structures such as the atria and ventricles as well as to the Jon M. Rogers, MD is Fellow and Clinical Instructor, John L. Robinson, MD is Associate Professor, Philip K. Fulkerson, MD is Associate Professor, John M. Stang, MD is Assistant Professor at the Division of Cardiology, and Steven Moon, MA is Clinical Instructor at the Division of Biomedical Illustration, Departments of Medicine and Allied Medical Professions, Ohio State University College of Medicine, Ohio State University Hospital, 410 West 10th Avenue, Columbus, Ohio 43210. USA.
Medical Teacher Vol 6 No 2 1984
great vessels. This problem becomes readily apparent when learners view opacified epicardial coronary arteries in various projections obtained at coronary cineangioPPhYWe have developed a teaching aid to help students and house officers conceptualize the anatomical locations of the epicardial coronary arteries. This method simply uses the hands as a model of the heart chambers and the great vessels, and may be applied on the wards or in the cine viewing room.
Method The intact human heart, when viewed in situ in the anterior projection, is comprised largely of the right atrium and right ventricle (Figure 1). In order to reproduce the anatomical relationships of the ventricles and atria in the human heart, we visualized these chambers as being related to one another in the same way as a pair of opposed hands. The left (or posterior) hand is skewed off the right (anterior) hand by one centimetre so as to duplicate the anterolateral aspect of the left ventricle as viewed in the anterior projection. The right thumb is abducted to 90 degrees to represent the superior vena cava (for later illustrating the course of the sinus node artery), and the left thumb is flexed at 45 degrees at the distal interphalangeal joint and opposed to the head of the left second metacarpal bone to represent the root of the aorta and the right and left coronary cusps. The nail of the left coronary cusp, and the anterior aspect of the distal phalanx of the left thumb represents the right coronary cusp (Figure 2). In this model the dorsal aspect of the right hand is related to the anterior and right lateral location of the right atrium, and the fingers of the right (anterior) hand are related to the right ventricle. The location of the left ventricle is represented by the left fingers in a lateral and posterior position to the right fingers (which occupy the location of the right ventricle). The superior vena cava is represented by the abducted right thumb, and the left thumb representation of the aortic root and cuspal structures is as noted above. In this relationship, when viewed from any oblique angle, the interventricular groove is composed of the groove between the two opposed sets of 57
58
Medical Teacher Vol 6 No 2 1984
Med Teach Downloaded from informahealthcare.com by University of Newcastle on 01/09/15 For personal use only.
Medical Teacher Vol 6 No 2 1984
59
Med Teach Downloaded from informahealthcare.com by University of Newcastle on 01/09/15 For personal use only.
Med Teach Downloaded from informahealthcare.com by University of Newcastle on 01/09/15 For personal use only.
fingers, as shown in Figure 1. This relationship is important in conceptualizing the course of the left coronary anterior circulation and the path of the posterior intraventricular groove branch of the right coronary artery. One can use a piece of paper held between the opposed hands to illustrate the location of the interventricular septum as well as the interatrial septum. The two sets of knuckles in the model also represent the atrioventricular groove, and the continuity between the anterior and posterior sets of knuckles in the model emphasizes the concept of the continuous circular nature of the base of the heart where the annuli of the atrioventricular valves are contained. In using the model for demonstration we have found it helpful for the instructor to oppose the hands of a volunteer and to point out the course of the coronary arteries and cardiac chambers. This makes it easier to rotate the two hands in concert to demonstrate the various structures, as viewed in different oblique angles, when teaching in small groups.
right coronary artery (now in its distal portion) runs in the atrioventricular groove inferiorly, and at right-angles to the groove it gives rise to the posterior interventricular groove artery. One can rotate the opposed set of hands by 90 degrees (Figure 3) to illustrate the course in the interventricular groove of that artery, which supplies the inferobasalar portion of the interventricular septum. This view is also helpful in demonstrating the intersection of the atrioventricular and interventricular grooves, and also serves to locate the origin of the atrioventricular node artery, which arises at right-angles to the plane of the inferior portion of the heart and runs through the interventricular septum to nourish the atrioventricular node. At the crux of the heart, the distal right coronary artery runs further in the atrioventricular groove (posterior or left-hand set of knuckles) to give rise, occasionally, to posterolateral branches which generally run in parallel to the grooves between the fingers of the left hand to supply the posterolateral aspect of the left ventricle.
Course of the Normal Coronary Circulation
Lcfr Coronary A d q
Right Coronary Artery
The course of the epicardial left coronary artery is shown in Figures 4 and 5. The left main coronary artery is given off from the left coronary cusp as represented by the nail of the left thumb, and it divides into anterior and posterior trunks. The anterior trunk courses in the interventricular groove formed by the two opposed hands and running anterolaterally. One or more diagonal branches depart from the anterior trunk and ramify over the lateral surface. of the left ventricle, as represented by the lateral aspect of the left fingers. The first septal perforator branch departs at right angles to the left anterior descending artery and courses in the plane between the two opposed hands, while the remainder of the left anterior descending coronary artery, in its midportion and distal segments, are represented by the artery shown in Figure 4. The posterior circulation, however, arises at the great division of the left main coronary artery and curves posteriorly outside of the atrioventricular groove (and out of the posterior or left hand row of knuckles) to give rise to the obtuse marginal branch, which ramifies over the posterolateral high base of the left ventricle. As the true posterior trunk travels inferiorly and to the right, several large posterolateral branches are given off, which roughly parallel the course of the grooves between the left fingers and which functionally supply the large portion of the posterolateral aspect of the left ventricle. At this point, the posterior trunk drops into the atrioventricular groove, again represented by the posterior set of knuckles, to become the true circumflex artery in its mid and distal portions and may develop a large branch at the crux cordis to form a posterior interventricular groove artery in the case of left coronary circulation dominance (Figure 5).
Using the above model the right coronary artery arises from the right coronary cusp, represented by the anterior aspect of the distal phalanx of the left thumb. It courses anteriorly over the head of the right second metacarpal bone to run in the anterior atrioventricular groove, represented by the anteriorly placed knuckles of the right hand. The conus branch of the right coronary artery leaves the main right coronary artery early in its course and curves superiorly over the first right knuckle to nourish the right ventricular outflow tract. The next major branch of the right coronary artery, the sinus node branch, arises from the right proximal coronary artery and curves superiorly and to the right to wind around the superior vena cava to supply the sinus node and the left and right atria by means of smaller branches. Using the thumb to represent the superior vena cava and the dorsum of the right hand to represent the right atrium, the course of the sinus node node artery can be demonstrated (Figure 2) as well as the anatomical location of the sinus node. As the right coronary courses in the atrioventricular groove (represented by the knuckles of the right hand) several branches are given off at right angles to the midportion of the right coronary artery which course anteriorly over the dorsum of the right hand. These branches represent right ventricular branches and run parallel to the grooves between the individual fingers of this hand. Several smaller right atrial branches are given off perpendicular to the mid-right coronary artery to run anteriorly over the right atrium, represented by the dorsum of the right palm. As the mid-right coronary artery courses inferiorly and anteriorly through the atrioventricular groove, the acute marginal branch is given off which courses in the imaginary angle formed between the diaphragm and the anterior aspect of the right ventricle. Following the departure of the acute marginal branch, the 62
Discussion As discussed above, the model is a simple representation of the cardiac chambers and the great vessels; it is quickly learned and may be used in group teaching to show the Medical Teacher Vol 6 N o 2 1984
Med Teach Downloaded from informahealthcare.com by University of Newcastle on 01/09/15 For personal use only.
course of the normal epicardial coronary arteries. It is useful in teaching coronary anatomy in the cineangiographic viewing suite, when native coronary artery injection is filmed in different angles as shown in Figure 6. Here, the opposed hand model is viewed in the left anterior oblique projection and clearly demonstrates the three major coronary arterial divisions as they appear angiographically in this projection. The other major feature of‘this model is the ease with which the concept of collateral circulation may be taught once the basic concepts of coronary anatomy have been mastered. Right-to-left collaterals arising from the distal right to circumflex the coronary artery as well as the posterior interventricular groove artery to the distal left descending coronary artery may be easily demonstrated in this manner as well as left-to-right collaterals in the opposite direction of flow.
Nutrition in Medical Education, The Teaching of Nutrition to Doctors at the undergraduate and postgraduate level is a controversial area and was judged to be an important subject for the first British Nutrition Foundation Task Force. The Monograph: Nutrition in Medical Education’ is the outcome of this Task Force. The Report recommends that: 0 Teaching of nutrition should begin at the preclinical stage and continue throughout medical training. 0 Teaching should include basic scientific aspects of nutrition but also demonstrate its practical application. 0 The objective may be best achieved by ensuring that in each medical school one academic unit takes a special interest in nutrition. 0 There should be one person appointed as a coordinator for nutrition education in each medical school, in the relevant department. 0 There is a need for continuing postgraduate training in nutrition, particularly for the general practitioner and community physician. 0 In district hospitals there is a need for a department to organize a ‘nutrition team’ to provide a nutrition advisory service for the hospital and community. 0 Closer associations in research and teaching are needed between medical schools and nonmedical centres of research. 0 There is a strong case for the Royal Colleges to appoint a working party to review the scope for medical students and junior doctors of education in nutrition.
‘Gray J (ed). Nufrifiun in medical educafiun. London: Tht British Nutrition Foundation, 1983. Price f 1.95.
Medical Teacher Vol 6 No 2 1984
UPDATE POSTGRADUATE CENTRE SERIES BOOKLETS CURRENTLY AVAILABLE Allergy 3rd ed. Anaerobic Infections Angina Chronic Bronchitis 2nd ed. Contraception Disorders of the Oesophagus 2nd ed. Disorders of the Stomach & Duodenum Eczema & Psoriasis 5th ed. Pain The Premenstrual Syndrome Wound Treatment and Care in General Practice SEMINAR SERIES Control of Hospital-Acquired Infections Pain Peptic Ulcer
FORTHCOMING PUBLICATIONS Acne 2nd ed. Asthma Chronic Bronchitis Diabetes Eczema & Psoriasis Epilepsy Occupational Dermatology The Menopause Practical Aspects of Dermatology Respiratory Tract Infection Rheumatoid Arthritis Terminal Care Ulcerative Colitis Urinary Tract Infection SEMINAR SERIES Allergy 2nd ed. Asthma Breast Cancer Hypertension 2nd ed. Pain 2nd ed. Peptic Ulcer 2nd ed. Schizophrenia Each Booklet costs f2.00 (in. p&p) cheques or postal orders to:
UPDATE PUBLICATIONS LIMITED 33134 Alfred Place. London WC1E 7DP
