AssessmentsValvular heart disease: Pathology review
USMLE® Step 1 style questions USMLE
A 20-year-old man is brought to the emergency department following a syncopal episode during football practice. The patient was running towards the end-zone when he suddenly collapsed. Current temperature is 37.0°C (98.6°F), pulse is 80/min, respirations are 15/min, and blood pressure is 118/85 mmHg. ECG demonstrates downsloping ST segment and T wave inversions in leads I, aVL, V4-V6, as well as prominent Q waves in leads II, III, and aVF. On physical examination, a systolic murmur is appreciated over the lower left sternal border. Which of the following maneuvers will increase the intensity of this murmur?
On the Cardiology ward, there are two individuals. One of them is 75 year old Antonia, who’s complaining of chest pain and says she hardly catches her breath after walking. On clinical examination, her pulse feels pretty weak and on auscultation, a systolic murmur is heard. The murmur was louder just after S1 and got quieter and quieter by the end of S2.
The other individual is 38 year old Mark who has a history of rheumatic fever and is complaining of not being able to swallow properly. On clinical examination, his voice sounds raspy and on auscultation, a snap is heard after S2 along with a diastolic rumble. Based on auscultation, both individuals were sent for echocardiography.
Okay, so based on auscultation and symptoms, both individuals seem to have valvular heart disease. Valvular heart disease involves damage or a defect in one or more of the four valves of the heart, so the aortic and mitral valves on the left side of the heart, and the pulmonary and tricuspid valves on the right side of the heart.
Okay, now, before talking specifics about valvular disease, we’ll first talk about rheumatic fever, which can affect multiple valves. Rheumatic fever can develop after streptococcal infection like strep throat, which is caused by Streptococcus pyogenes. This particular group of streptococcus has an antigen that lumps it into a group called “group A”, and they also produce an enzyme called streptolysin, which causes hemolysis. Some of these strep bacteria have a protein on their cell wall called “M protein”, and this particular protein is highly antigenic, meaning that the immune system sees it and recognizes it as a foreign molecule and produces antibodies against it.
Now, this becomes a problem when these antigens cause a phenomenon called molecular mimicry. M proteins can be structurally similar to human proteins, which means the antibodies that target them will also target our own tissue. In this case, they are similar to proteins found in the myocardium and heart valves. Once bound to cardiac tissue, the antibodies activate nearby immune cells, which causes a cytokine-mediated inflammatory response and tissue destruction. This is also an example of what’s called a type 2 hypersensitivity reaction.
All right, so not everyone that gets strep throat gets rheumatic fever, and it’s actually only a small minority that get it. However, the individuals that do get rheumatic fever from strep infections will have a variety of clinical findings. These make up the Jones criteria which is divided into 5 major criteria that you have to remember, and 5 minor criteria that are also good to keep in mind. Let’s go over the major criteria first.
The most common is migratory polyarthritis of the joints, where multiple large joints become inflamed, swollen and painful, then the inflammation resolves and spreads to other joints. Secondly, some patients have carditis. The inflammation can affect the endo, myo, and pericardium. Since the endocardium includes the valves, they too are affected.
A high yield fact to remember is that the mitral valve is most commonly affected, although the aortic and tricuspid valve can also be affected. In the acute phase of the illness,