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? Auscultation for the tricuspid valve would be in the left sternal margin of the 5th intercostal space. The mitral valve sounds are heard over the apex of the heart (5th intercostal space) in line with the middle of the clavicle. Pulmonary valve sounds are auscultated at the 2nd intercostal space at the left sternal margin. The aortic valve is heard at the 2nd intercostal space of the right sternal margin. b. Where do you think would be the best place to auscultate Caleb’s abnormal heart sound? Explain your answer. The abnormal heart sounds would best be heard over the tricuspid area – the lower left sternal border. This is the area which 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. The normal sounds of the heart are “lub-dup” are caused by the opening and closing of the heart valves. The first sound – lub- is from the closing of the mitral and tricuspid heart valves. The second sound -dup- is from the closure of the pulmonary and aortic valves. b. In relation to the normal heart sounds, when would you expect to hear the abnormal sound Dr. Baker heard? Explain your answer. A ventricular septal defect is a systolic murmur. The abnormal sounds can be heard during or after the first heart sound and ends before or during the second heart sound.
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 the blood to move from the left to the right ventricle. b. Based on your understanding of blood pressure and resistance in the heart and great vessels, explain your answer to question 3a. In the heart blood flows from areas of high pressure to areas of low pressure. Blood normally enters on the right side of the heart (deoxygenated), is pumped to the lungs and returns to the left side of the heart (oxygenated) which will then be pumped out to the rest of the body.
In Caleb’s case blood will enter the right side of the heart, be pumped to the lungs and return to the left side of the heart. Every time his heart beats, some blood is then forced through the VSD back to the right side. It then goes back to the lungs even though it is already oxygenated, so blood that is not oxygenated can’t get oxygen. A lower blood volume then remains in the left ventricle to be pumped out to the rest of the body. High pressure would occur in the lungs due to extra blood being pumped into lung arteries this make heart and lungs work harder.
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 normally pumps blue blood because the blood is without oxygen and the left ventricle pumps red blood because the blood has oxygen. b. In Caleb’s heart, what color would the blood be within the right and left ventricles, respectively? It is both blue and red in the right ventricle because the already oxygenated blood flows back into the right ventricle and blood in the left ventricle would be 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 the mixing of blood. There is a hole in center of heart where the wall 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 heart’s right side and mix with deoxygenated blood, then go back to the lungs. Another abnormality is Atrial Septal Defect (ASD), 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. Caleb’s systemic cardiac output will be decreased. His blood will enter the right ventricle be pumped to the lungs, return to the left ventricle and then be shunted back to the right ventricle. This causes more blood to enter the right ventricle. The extra blood then leaving the right ventricle causes a volume overload to the lungs. Because blood is being shunted back to the right ventricle, there is a lesser volume of oxygenated blood that leaves the heart to supply the rest of the body.
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. In VSD the right and left ventricles are working harder, pumping a greater volume of blood than they normally would. Extra blood will pass through the pulmonary artery into the lungs causing, blood pressure to be higher than normal in the blood vessels and lungs.
b. Describe what would happen to the myocardium of Caleb’s right ventricle as a result of his VSD. The right ventricular heart muscle will thicken and lose elasticity over time, causing the heart to work harder to effectively pump blood the lungs and rest of the body.
8. Based on the location of Caleb’s defect, what part of the conduction system might be at risk for abnormalities? It is extremely rare that VSD would cause a conduction system defect due to the fact that the two systems are different, different embryological development, yet are in close proximity to each other. It is possible for the bundle of His to be displaced, but usually is unaffected. Sometimes a branch of the bundle of His could be on a rim of the VSD, but is still able to function. The only tricky part is if surgery is needed, the doctor needs to be careful when closing the defect.