Clinical Application (20 pts)
Your friend's 1-year-old Ragdoll cat, Jasper, was recently diagnosed with
hypertrophic cardiomyopathy (HCM). Before they went to the vet, Jasper had a slight
loss of appetite, and he was less active as well. Following an echocardiogram of the
heart, Jasper's left ventricle appeared hypertrophied (excessive enlargement or
overgrowth), and he has an elevated resting heart rate. After more testing, your friend
was informed by the veterinarian that this is a hereditary condition, and that Jasper will
have to take treatments like Enalapril, an ACE inhibitor, to improve heart function.
Because you took BIOS 343, you are very informed about the anatomy and
physiology of vertebrates. Your friend knows the mutation that causes HCM affects
sarcomeres, and that it causes the muscle tissue within the left ventricle to thicken.
However, your friend remembers from high school that the left ventricle is known to be
thicker than the right ventricle because it pumps out blood to the entire body. They
ask you: if the left ventricle is thicker, isn't that a good thing that there is more muscle
to pump out blood to the body? After a bit of research, you both realize that the
growth is so abnormal that it actually obstructs blood flow and causes backflow.
You come across many details about HCM, including the fact that it can result
in fibrosis of the heart, which is characterized by excess thickening and scarring of
tissues. It is also known that as more scar tissue builds up, the nervous system is affected
negatively, preventing signals from traveling through the cardiac conduction system
properly or even at all. Particularly those serving to lower blood pressure. Additionally.
the change in tissue anatomy makes it hard for the ventricles to fill and eject blood
as effectively, making it hard for it to match its input with its output. Enalapril and
other medications prevent the progression of HCM by decreasing blood pressure.
although they can cause symptoms such as increased urination.
A. Of the following options, choose the one that would help to properly match the
above scenario. Reject all the rest. For full points you must also provide an
explanation for each case. Defend the correct choice with adequate
justification. For those that are false, explain why they are incorrect. (10pts)
1. Accept/Reject: The ACE inhibitor increases blood volume by blocking water
reabsorption in the PCT and collecting duct. This lowers the blood pressure, so
the cardiac muscle performs less work, and Jasper can have a functional heart.
2. Accept/Reject: The direct release of Angiotensin II from the liver is prevented in
the presence of an ACE inhibitor, preventing fibrosis and protecting the Purkinje
fibers in Jasper's neurogenic heart.
