Why can polycythemia potentially cause a heart problem?

Answer 1

It is more likely that a heart problem will cause polycythemia than the other way around.
But because polycythemia causes your blood to thicken and slows blood flow, it increases your risk of developing blood clots. If a blood clot occurs in your head, it can cause a stroke. If they reach the coronary arteries that feed the heart muscle, a heart attack will be the result.

Answer 2

because it can lead to thrombosis of the coronary arteries, heart chambers, and or great vessels which in turn can leads to strokes and heart attacks

Answer 3

The blood can become viscous (thick) from an increase in the number of red blood cells circulation. The heart has to work harder to pump thick blood around the body.