Cardiac Practice Question Key

Mr. K is a middle-aged man who complains of fatigue. His systolic blood pressure is high, but his diastolic blood pressure is very low. Pulses in his legs are very weak, as if there is little blood flow to the lower half of his body. His breath sounds are normal. When you listen to his heart, you hear an abnormal second heart sound, and the doctor decides to inject a dye to follow the path of blood through his heart.

The dye shows that blood is moving from the aorta back into the left ventricle during diastole. Mr. K’s lab values have come back and they show that he has high renin and aldosterone levels, slightly low blood K+, and a high hematocrit.

Is his heart normal? If not, what is abnormal about it? How does the abnormality relate to the heart sounds? What has caused his high systolic blood pressure? Why are his blood K+ low and his hematocrit high?

His heart is not normal! Blood should never go from the aorta back into the left ventricle. His aortic semilunar valve is leaking, which accounts for the abnormal heart sound. The second heart sound is caused when the ventricles relax and the semilunar valves snap shut.

The high systolic blood pressure could be caused by the low perfusion in the lower half of his body. His kidneys aren’t getting enough blood flow, so they release renin and start the RAA pathway. The renin creates angiotensin I and II, which raises Bp through vasoconstriction and stimulates aldosterone release. The aldosterone causes Na+ andH2O reabsorbtion from the urine and K+ secretion into the urine. Blood volume increases, causing cardiac output to increase and raising BP. His blood K+ is low because so much is being lost in the urine.

The decrease in kidney blood flow means that the kidneys don't get enough O2. They release erythropoietin and this stimulates the bone marrow to make more RBCs. That increased his hematocrit.