Crimes of the Heart: a Case Study on Cardiac Anatomy

Teaching Notes Crimes of the Heart: A Case Study on Cardiac Anatomy

Introduction: Caleb’s case is designed to help students better understand heart chamber, valve, and great vessel anatomy. Furthermore, it reinforces the idea that the chambers isolate specific blood volumes during different phases of the cardiac cycle to maintain adequate pulmonary and systemic perfusion. Caleb suffers from a hole in the interventricular septum causing a left-to-right blood shunt. Due to the increased volume of blood in the right ventricle, there is an increase in the total amount of blood pumped to the pulmonary circuit during each systole leading to an increase in pulmonary blood pressure. As the volume and pressure in Caleb’s pulmonary vessels increases, fluid from the blood begins to leak into the alveoli and affects his respiratory status. So, the pulmonary edema is demonstrated physically by Caleb’s labored breathing and difficulty eating. Furthermore, the volume overload in the right ventricle causes an increased end systolic volume, stretching of the myocardium, and enlargement (hypertrophy) of that chamber.

When looking at the effects a ventricular septal defect (VSD) has on the right side of the heart, instructors can discuss how reduced cardiac output decreases systemic tissue perfusion. Although this case focuses on the anatomy of the heart, it provides instructors the opportunity to emphasize the relationship between blood pressure and the flow of blood through the heart and great vessels. Additionally, the case highlights how the anatomy of the heart maintains a separation between the pulmonary (right heart) and systemic (left heart) circuits.

Objectives: Upon completion of this case, students will be able to:  Identify where on the thoracic wall heart valves and murmurs can be auscultated.  Understand the relationship between heart sounds and valve closure.  Understand the anatomy of the pulmonary and systemic circuits and relate this knowledge to the signs and symptoms of a ventricular septal defect.  Demonstrate knowledge of the relationship between blood pressure and the flow of blood in the heart.  Understand the relationship between left ventricular volume, stroke volume, and cardiac output.

Prerequisites: Students should:  Have a basic understanding of heart chamber and valve anatomy.  Identify the anatomical location of the great vessels.  Define the relationship between blood pressure and resistance to flow.  Have a basic understanding of the blood flow pattern through the heart chambers and great vessels.  Define cardiac output, end diastolic volume, end systolic volume, and stroke volume.  Have a basic understanding of the cardiac conduction system and ECG tracings. Classroom Management: This case is designed to be used during the study of heart anatomy. It has its greatest impact when used after discussing the major anatomical structures of the heart, great vessels, cardiac output, and the conduction system. For this case to be used effectively, students need to meet the prerequisites indicated earlier.

The short answer questions are designed to facilitate in-class discussion concerning the pathway of blood through the different chambers of the heart and great vessels. This discussion period can span two class periods or two to three hours. To shorten that time frame, it is reasonable for short answer questions 1–2 to be assigned prior to the discussion session. Students will need a textbook or online resources in order to complete short answer questions 3–7. These questions are grouped in blocks:

 Block A (1–2): Direct knowledge of gross anatomy of the heart and heart sounds  Block B (3–5): Anatomy of the pulmonary and systemic circuits  Block C (6): Relationship between end diastolic volume and cardiac output  Block D (7): Relationship between right atrium, pulmonary circuit, and lungs  Block E (8): Anatomy of the cardiac conduction system

The blocks of questions build on each other so it is important that the students show mastery of one block before they move on to the next. Students can first work on each block individually. Then, groups of four to five students can be formed to discuss their answers. This is a good opportunity for the instructor to provide feedback on common problems and questions. Short answer question 7 will be quite challenging because it pushes students to relate the effects of increased blood volume in the right ventricle to pulmonary effects and effects on the myocardium. It will be helpful to remind students about the direct relationship between pressure and volume.

The multiple choice questions can be used to evaluate the entire class after the case has been discussed in small groups. This type of evaluation can be done as a post-quiz either online or in the classroom.

Additional Resources: It may be helpful for the instructor to show normal and abnormal echocardiograms during the discussion periods. The links provided can be used to facilitate this process:  NORMAL: www.youtube.com/watch?v=TwA0LM5_1dE&feature=related  VSD: www.youtube.com/watch?v=yJt_sVGh8sg&feature=related

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