1a. 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.
1b. 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.
2a. 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.
2b. 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
3a. I would expect blood to move from left to right because the left ventricle is stronger and create a stronger contraction
3b. 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.
4a. The right ventricle has deoxygenated blood (blue). The left ventricle has oxygenated blood (red).
4b. The right ventricle has both deoxygenated and oxygenated blood (both blue and red). The left ventricle has oxygenated blood (red).
5a. 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.
6a. 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.
7a. 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.
7b. 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.
8a. 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.