How would a blockage in one of the coronary arteries affect the hearts stroke volume?

Stroke volume: If a major artery is blocked then it will result in damage to that part of the heart muscle and the muscle will not be able to pump blood out of the heart hence the stroke volume will reduce.

By decreasing oxygen: The heart muscle depends on oxygen supplied by the coronary arteries to effectively function. When the artery is narrowed it can decrease the supply of oxygen and decrease the force of the muscle contraction. The stroke volume is a measure of how much blood the heart forces out with each beat.