How do we measure heart health?

• Electrocardiogram (ECG): Uses electrodes placed on various parts of the chest, arms, and legs in order to measure the electrical activity of the heart. This is one of the quickest and easiest ways to evaluate the heart.


• Echocardiogram: An ultrasound that uses sound wave echoes from the heart to see how the heart’s chambers and valves are pumping blood.


• Cardiac Magnetic Resonance Imaging (Cardiac MRI): A magnetic field and radio waves are used to create detailed pictures of the heart to assess its structure and function.


• Multigated Acquisition Scan (MUGA): A nuclear medicine test that uses gamma rays and a chemical tracer to assess how well a heart is pumping blood.


• Cardiac Catherization: A procedure where a small, flexible tube (a catheter) is inserted into a blood vessel and threaded all the way into the heart to get very accurate measurements on the blood pressure in various chambers of the heart.

How does sickle cell disease affect the heart?

Over time, sickled cells can cause damage to the blood vessels that carry blood to the lungs. This damage means that the heart must work harder to pump blood to the lungs and causes increased blood pressure in the arteries of the lungs leading to pulmonary hypertension. Eventually, this can cause weakening of the heart muscle and can lead to heart failure.

An echocardiogram measures the pressure and flow in various parts of the heart to estimate if someone has pulmonary hypertension, but cardiac catheterization is necessary to definitively diagnosis this. This pressure can be estimated by measuring the tricuspid regurgitant jet velocity (TRJV). Elevated TRJV can be seen in 20-40% of adults with sickle cell disease (1,2), but cardiac catheterization showed that less than 10% of these patients have pulmonary hypertension. Studies have also shown that elevated TRJV is associated with about 10% yearly increased risk of death in adults with sickle cell disease (3).

While heart disease generally develops over time, sometimes children can develop elevated TRJV and pulmonary hypertension.

Heart disease is one of the reasons why doctors may recommend a hematopoietic stem cell transplant (HSCT) or gene therapy for a person with sickle cell disease.

We are studying whether curative therapies will help improve the heart function of patients by improving the TRJV and lead to improved survival. The COALESCE study will help us understand this better as we will be gathering results of heart function tests before and after curative therapy.

References

1. Gladwin MT, Sachdev V, Jison ML, et al. Pulmonary hypertension as a risk factor for death in patients with sickle cell disease. N Engl J Med. Feb 26 2004;350(9):886-95. https://doi.org/10.1056/NEJMoa035477


2. Sutton LL, Castro O, Cross DJ, Spencer JE, Lewis JF. Pulmonary hypertension in sickle cell disease. Am J Cardiol. Sep 15 1994;74(6):626-8. https://doi.org/10.1016/0002-9149(94)90760-90


3. Gladwin MT, Barst RJ, Gibbs JS, et al. Risk factors for death in 632 patients with sickle cell disease in the United States and United Kingdom. PLoS One. 2014;9(7):e99489. https://doi.org/10.1371/journal.pone.0099489