How does high hemoglobin effect heart?

High hemoglobin levels can lead to increased blood viscosity, which makes it harder for the heart to pump blood effectively. This can strain the cardiovascular system, potentially resulting in elevated blood pressure and an increased risk of heart complications, such as thrombosis or heart failure. Additionally, the heart may work harder to deliver oxygen to tissues, which could lead to hypertrophy or other long-term issues if the elevated hemoglobin persists.