Elevated Troponin and Rheumatic Heart Disease

Today we discussed a case of a woman with chest pain, new atrial fibrillation and an elevated troponin. She likely had rheumatic fever as a child and an echo revealed severe MR with a dilated left atrium. There were some great learning points that came up! Lets discuss.

Troponin is sensitive, not specific! 
When you assess a patient with an elevated troponin do not immediately jump to ACS as the cause! While this will be the most common cause (and certainly one of the more concerning) there are many other etiologies. Always be rigorous in your history and physical exam to decide whether or not ACS is the most likely diagnosis and to rule out others. Some other causes of elevated troponin include:

• Myocardial Infarction
• Post-instrumentation (PCI, cardiac surgery)
• PE
• End stage renal disease
• Pericarditis/Myocarditis
• Aortic Dissection
• Heart Failure
• Sepsis
• Trauma
• Stroke or intracerebral hemorrhage

Check out this great article on the differential diagnosis of elevated troponin: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1860726/

Rheumatic fever is less common in developed countries but we still need to know about it.

Acute rheumatic fever occurs a few weeks after group A strep pharyngitis. However, not everyone who gets group A strep pharyngitis will get rheumatic fever! In fact, in developed countries, only about 3% of patients with untreated group A strep pharyngitis develop rheumatic fever. This number is lower than in developing countries - most likely due to improved hygiene (reduced transmission) and higher rates of antibiotic use for 'strep throat'.

Rheumatic fever is an illness characterized by classic signs and symptoms in a patient who had recent group A strep pharyngitis. 

We are all familiar with the 'Duke Criteria' for endocarditis. Well, rheumatic fever has the Jones Criteria to help you diagnose it:

There is a high probability that your patient has acute rheumatic fever if they had a recent group A strep infection and fulfill 2 major criteria or 1 major + 2 minor critera.

Acute rheumatic fever can lead to rheumatic heart disease.

Those who develop acute rheumatic fever are at high risk of having cardiac involvement and developing cardiac complications. Lasting complications of rheumatic heart disease are due to heart valve destruction and include CHF, stroke, endocarditis and death. How does pharyngitis cause heart disease you ask? Well it's not perfectly understood but you can explain it using buzzwords like 'molecular mimicry' (antibodies against strep will attack native cells/tissue, like myocytes). You'll have to check out another source if you want to learn more about that...

So the key is to prevent acute rheumatic fever by promptly diagnosing and treating group A strep pharyngitis in the first place!

Mitral regurgitation is the most common valve pathology of rheumatic heart disease. These patients will frequently develop chronic mitral regurgitation. According to the ACC/AHA guidelines (which I have summarized here), you should consider surgery for severe mitral regurgitation when any of the following indications are met:

• Acute, symptomatic severe MR
• Chronic MR which is symptomatic 
• Chronic MR with LV dysfunction
• Chronic MR for patients undergoing other cardiac surgery 
• Atrial fibrillation
• Pulmonary hypertension
• Mitral valve prolapse and ventricular arrhythmias

Thanks Team 1 for a great case!

Check out the following resources for more info:

1. Seckeler MD, Hoke TR. The worldwide epidemiology of acute rheumatic fever and rheumatic heart disease. Clinical Epidemiology. 2011;3:67-84. doi:10.2147/CLEP.S12977.
2. Korff S, Katus HA, Giannitsis E. Differential diagnosis of elevated troponins.Heart. 2006;92(7):987-993. doi:10.1136/hrt.2005.071282.
3. Bonow RO, Carabello B, de Leon AC, Jr., et al. ACC/AHA guidelines for the management of patients with valvular heart disease: A report of the American College of Cardiology/American Heart Association Task Force on practice guidelines (Committee on management of patients with valvular heart disease)12. J Am Coll Cardiol. 1998;32(5):1486-1582. doi:10.1016/S0735-1097(98)00454-9.

Pancytopenia

Today we discussed a very interesting case of pancytopenia. This is a great internal medicine topic that is definitely worth reviewing. The causes of pancytopenia are extensive so it can be overwhelming to come up with a comprehensive differential diagnosis. That's why it's great to have an organized approach and stick to it every time!

One approach that we discussed is to divide the causes of pancytopenia into those associated with bone marrow which is either hypocellular or hypercellular:

Hypocellular Marrow:

• Drugs/Toxins: Methotrexate, chemotherapeutics, various antibiotics, allopurinol...
• Infection: Parvovirus B19, EBV, HIV, TB, Hepatitis, Sepsis 
• Autoimmune: Lupus, HLH
• Paroxysmal Nocturnal Hemoglobinuria (PNH)

Hypercellular Marrow

• Malignancy: Leukemia, Lymphoma, MDS
• Nutritional: Deficiencies in B12, folate, copper
• Marrow Replacement: Myelofibrosis, Granulomatous disease (TB, sarcoid, fungal), solid tumor metastatic disease

A few words about paroxysmal nocturnal hemoglobinuria (PNH):

This is a rare acquired stem cell disorder which can present as unexplained hemolytic anemia, thrombosis, hemoglobinuria and non-specific symptoms. It can certainly present as pancytopenia along with the associated complications. PNH should be considered in Coombs negative hemolytic anemia or other unexplained cases of anemia. The diagnosis is made with flow cytometry using a technique that determines whether certain cell wall proteins (GPI) are present or not - they are absent in PNH. Definitive treatment of PNH is a stem cell transplant.

Another few words about Myelophthisic Anemia:

What a great word! Whoever decided to put a `ph` next to a `th` must have enjoyed watching people struggle with pronouncing things... This entity was brought  up today in morning report. Myelophthisis refers to bone marrow being displaced by some other process. This could include tumor, infection (TB), granulomatous conditions (sarcoid) or fibrosis. There are often clues on the peripheral blood film that may suggest a myelophthisic process. These include teardrop cells and nucleated red blood cells.

Check out this article for a general overview of the causes of pancytopenia: http://www.ncbi.nlm.nih.gov/pubmed/23270895 

Hyperkalemia

Hyperkalemia can be fatal! Now that I have your attention, time for some learning…

We recently discussed a case of hyperkalemia in morning report. This is a ‘bread and butter’ internal medicine topic for which trainees have been taught the same approach for eons: pre-renal, renal and post-renal. Instead of focusing on the approach to the many causes of hyperkalemia I will review the acute management.

Stop potassium from coming in

• Low potassium diet
• Stop potassium containing IV fluids - sounds obvious but makes sure to check!
• Also, remember to stop nephrotoxic medications - think about NSAIDs, ACE-inhibitors, etc...

 Stabilize the cardiac membrane

• Calcium gluconate (or chloride) will stabilize the cardiac membrane and (hopefully) prevent a dangerous arrhythmia. But the effect lasts under an hour so give calcium first to buy yourself time to initiate the definitive measures below.

Shift potassium into cells

• Insulin 10-20 units IV to shift potassium into the cells.
• Dextrose D50W 1-2 amps to avoid hypoglycemia from your insulin. The sugar load will also stimulate release of endogenous insulin, thereby further shifting potassium into cells.
• Beta agonists are also effective at transiently lowering serum potassium.
• Sodium Bicarbonate infusion has been shown to cause a small reduction in serum potassium. However, you may not always need to give it if your other measures are successful.

Remove potassium from the body

• Renal: Is the patient producing urine? It is important to address any cause of AKI. Healthy kidneys with a reasonable GFR should eliminate any excess potassium. If the patient is volume overloaded and the clinical situation permits, you can give a loop diuretic to promote renal excretion of potassium. If the patient is pre-renal, perhaps he just needs some IV fluids to start excreting potassium. 
• GI: Resins are often used to treat hyperkalemia (ie. Kayexalate aka sodium polystyrine sulfate) but they are frequently not effective after a single dose and their use has been linked to intestinal necrosis. So if you're going to use a resin, make sure the patient is not post-operative and has no GI problems (ileus/obstruction). Another school of thought is to avoid kayexalate and instead use lactulose to induce a diarrhea which will result in potassium loss. Regardless of your approach, the bottom line is that after you do all (or some) of the above, make sure to follow the serum potassium closely (recheck in 1-2 hours), make sure that one of the methods of potassium excretion is working and address the underlying cause.
• Hemodialysis: If the hyperkalemia is refractory to your management (above) you should consult your friendly nephrologist for consideration of dialysis.

Check out the following review article from CMAJ on Manegement of Acute Hyperkalemia: http://www.ecmaj.ca/cgi/content/citation/182/15/1631