1. Dr. Baker spends a long time listening to (auscultating) Caleb’s heart.
a. Where on the thoracic surface do you auscultate to the tricuspid, mitral (bicuspid), pulmonary, and aortic valves?
Tricuspid is the fourth intercostal space on the lower left sternal border; mitral (bicuspid) is the fifth intercostal space medial to left midclavicular line; pulmonary is the second intercostal space on the left upper sternal border; and aortic is the second intercostal space on the right upper sternal border.
b. Where do you think would be the best place to auscultate Caleb’s abnormal heart sound? Explain your answer.
Caleb’s defect lies in the interventricular septum between the atrioventricular valves. So, the best place to hear it would be from the lower left sternal border to the right lower sternal border because this is the area that overlies the defect.
2. Caleb has abnormal heart sounds that tipped the doctor off to a problem.
a. Name the normal sounds of the heart and indicate what causes these sounds.
Heart sounds are created by the sounds of the opening and closing of the heart’s valves, as well as the blood flowing through them. The normal action of the heart is the pumping of the chambers and the closing of the valves. The “lub-dub” sounds are the normal heart sounds in a healthy adult. These are the first and second heart sounds, designated S1 and S2. S1 represents the closing of the tricuspid and mitral valves between the atria and the ventricles. S2 represents the closing of the pulmonary and aortic valves as blood leaves the right and left ventricles, respectively. Other heart sounds are abnormal in adults.
b. In relation to the normal heart sounds, when would you expect to hear the abnormal sound Dr. Baker heard? Explain your answer.
I would expect to hear the murmur after the S1 sound because after the AV valves close, ventricular systole / contraction occurs. But with a ventricular septal defect, blood mixes because the left ventricle pushes blood back into the right ventricle, which decreases systemic vascular resistance
3. The defect in Caleb’s heart allows blood to mix between the two ventricular chambers.
a. Due to this defect would you expect the blood to move from left-to-right ventricle or right-to-left ventricle during systole?
I would expect blood to move from left to right because the left ventricle is stronger and create a stronger contraction
b. Based on your understanding of blood pressure and resistance in the heart and great vessels, explain your answer to question 3a.
Blood moves into an open space where there is the least amount of resistance or down its resistance gradient. The blood pressure in the right ventricle is lower than the pressure in the left ventricle. This phenomenon occurs because the afterload in the right ventricle is lower than the afterload of the right ventricle. The difference between these afterloads is due to the pulmonary blood vessels generating less resistance when compared to the systemic blood vessels.
4. When an echocardiogram is performed, the technician color-codes oxygenated blood (red) and deoxygenated blood (blue).
a. In a healthy baby, what color would the blood be within the right and left ventricles, respectively?
The right ventricle has deoxygenated blood (blue). The left ventricle has oxygenated blood (red).
b. In Caleb’s heart, what color would the blood be within the right and left ventricles, respectively?
The right ventricle has both deoxygenated and oxygenated blood (both blue and red). The left ventricle has oxygenated blood (red).
5. Caleb’s heart allows oxygenated and deoxygenated blood to mix. Based on your knowledge of the heart and the great vessels, describe other anatomical abnormalities that cause the mixing of oxygenated and deoxygenated blood.
Atrioventricular Canal Defect is an abnormality that causes mixing of blood. There is a hole in the center of the heart where the walls between the upper and lower chambers meet. The tricuspid and mitral valves aren’t formed properly and one large valve crosses the defect. The defect lets oxygen rich blood pass to the hearts right side and mix with deoxygenated blood, then goes back to the lungs. Another abnormality is called Atrial Septal Defect. ASD is where the walls of the upper chambers of the heart don’t close completely causing a left to right movement of blood due to the higher pressure. The mixing of oxygenated and deoxygenated blood may cause the right atrium and ventricle to enlarge due to the higher volume of blood.
6. What happens to Caleb’s systemic cardiac output as a result of his ventricular septal defect (VSD)? Explain your answer.
Due to a left-to-right blood shunt, the left ventricular volume falls during systole prior to the opening of the aortic valve. This shunt decreases stroke volume and cardiac output from the left ventricle into the aorta.
7. One of the problems that worried Tiffaney was that Caleb seemed to be breathing too hard all the time. Let’s consider how this symptom is related to his heart defect.
a. Describe what would happen to the blood volume and pressure entering the pulmonary circuit as a result of his VSD.
There is an increase in the total amount of blood pumped to the pulmonary trunk during each systole. Thus, the total pressure in these vessels also increases. This excessive volume/pressure, or pulmonary hypertension, causes pulmonary edema indicated by Caleb’s increased work of breathing.
b. Describe what would happen to the myocardium of Caleb’s right ventricle as a result of his VSD.
Due to the left-to-right shunt, the blood volume within the right ventricle increases. Due the volume overload, the right ventricle cannot effectively pump out blood, causing an increase in end systolic volume and stretching of the myocardium. The end result is an overall enlargement of the wall of the right ventricle called hypertrophy.
8. Based on the location of Caleb’s defect, what part of the conduction system might be at risk for abnormalities?
Since Caleb has a hole in his heart muscle wall these parts of the conduction system might be at risk for abnormalities; the SA node, AV node, and bundle branches.
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