Why Is Troponin Elevated in Kidney Disease
Troponin is a marker used to evaluate cardiac problems or cardiac ischemia. Doctors use the troponin level to determine whether cardiac damage has occurred. However, there are other indications other than cardiac issues that will cause the troponin level to be elevated.
Elevated Troponin Causes
In this article, I talked extensively about the reasons that troponin levels might be elevated. Some of these reasons are:
- Heart attack
- High blood pressure
- Congestive heart failure
- Heart surgery
- Kidney failure
- Blood clots
- Autoimmune diseases
Kidney disease patients have a high rate of heart attacks and coronary artery disease. Therefore, it is imperative that doctors know the difference between troponin levels elevated because of heart issues versus kidney disease.
Chronic Kidney Disease and Troponin Levels
People with chronic kidney disease or kidney failure usually have other health issues such as coronary artery disease, high blood pressure, and diabetes. Therefore, when a patient diagnosed with kidney disease comes into the emergency room with cardiac symptoms, the doctors need to do other tests besides the troponin test.
For example, when a patient with kidney failure comes into the emergency room complaining of chest pain, one of the first tests that the doctor will perform is a troponin level. However, this test can be misleading because oftentimes, the troponin is elevated in the patient with chronic kidney disease.
Every day in the emergency room, troponin levels are done as the usual workup for patients presenting with chest pain.
Diagnostic Tests Done When Troponin Levels are Elevated
Traditional tests done for cardiac problems such as the EKG and ECHO are not helpful in this kidney disease population. However, the problem is troponin levels are increased in patients with kidney failure.
The ECG is not really helpful because the renal patient often has electrolyte imbalances. We know that electrolyte imbalances can sometimes be shown on the ECG as a heart problem when it is not.
Many times the troponin levels are elevated and the person has no heart issues. So why do people with kidney failure have elevated troponins?
The problem becomes more challenging because cardiovascular disease accounts for 50% of deaths in the kidney disease population.
Why Do People With Kidney Disease Have Elevated Troponins?
In one study, almost 80% of people with a low GFR or glomerular filtration rates have elevated troponins even in the absence of cardiac issues. The GFR is the rate at which the kidneys are able to filter out toxins and to control fluid balance.
According to Dr. Saravia who is 2nd-year resident at NYU Medical Center, a study that included 700 patients with renal disease found that almost 6% of the patients had an elevated troponin. These findings suggest that this is a common finding.
There is no concrete understanding among doctors as to why the troponin is elevated in renal disease.
One of the reasons for the elevation of troponins in kidney disease is that the newest troponin labs reacted with skeletal muscle. The 3 troponins levels that are measured are:
- TnT- Troponin T anchors the troponin complex to the muscle fiber structure
- TnC – Troponin C initiates contraction by binding calcium and moves Troponin I so that the two proteins that pull the muscle fiber shorter can interact.
- TnI – The inhibitory subunit, binds actin in the relaxed state, thereby preventing muscle contraction by inhibiting the ATPase activity of actomyosin.
Troponin and Kidney Injury
I know these different types of troponin can be confusing, but just know that these are things that pertain to the lab. When we get our lab results, it is just listed as the troponin level.
According to some scientists, the presence of uremia in the kidney patient causes elevated troponin. This is because uremia damages skeletal muscle fibers, and when skeletal muscle is damaged, one of the byproducts is troponin.
Uremia is a clinical condition associated with worsening renal function, is characterized by fluid, electrolyte, and hormone imbalances in addition to metabolic abnormalities. Uremia is toxic to the organs and muscles.
There are several forms of TnT that are found in skeletal muscle.
There are actually some theories that people with heart disease present with atypical heart disease symptoms. These elevations may be the result of a “silent heart attack”. Many patients with kidney failure are found to have many manifestations of heart disease such as :
- Enlarged heart disease
- High blood pressure
These 3 conditions can cause an elevation in the troponin level. Patients with enlarged hearts have cell damage which releases troponin.
There is also evidence that increased phosphates are associated with elevated troponin. Phosphates are elevated because the kidney cannot process and eliminate phosphates.
Another explanation is that the troponin is just not able to clear the body because the kidneys are failing.
Dialysis does not affect troponin levels. Although, if a patient has a dialysis treatment, the troponin levels will be reduced because dialysis will pull some of the excess troponins out.
There are different reference numbers for different labs. The average reference number is less than 0.04 ng/ml.
If you have kidney failure, just know that it is “normal” to have an elevated troponin level in the absence of heart problems. However, just to be sure your physician should always check out your heart if you have an elevated troponin level.
The best way to avoid heart issues when you have kidney failure is to be 100% compliant with your diet and treatment plan. The diet included limitations such as potassium, protein, and fluids. Whatever you do, do not skip dialysis.
As a nurse, I have witnessed many people who have skipped dialysis with disastrous results. Have you ever had an elevated troponin level and did not have any cardiac issues?
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