Which of the following decreases stroke volume and contractility?

Decreasing stroke volume and contractility can occur due to several physiological conditions. In the context of this question, each scenario affects the heart's ability to pump effectively.

Heart failure is a condition where the heart's ability to pump blood is impaired, leading to decreased stroke volume. It often results from chronic hypertension or previous myocardial injury, leading to alterations in cardiac structure and function. In heart failure, the weakened myocardium cannot contract as forcefully, thus reducing contractility and stroke volume.

Myocardial infarction, commonly known as a heart attack, causes damage to the heart muscle due to a prolonged lack of blood supply. This damage can directly reduce the muscle's contractile strength, leading to decreased stroke volume. The area of the heart that is infarcted will not contribute effectively to the heart's pumping ability, thereby diminishing the overall contractility.

Acidosis, characterized by an increase in hydrogen ion concentration in the blood, can negatively impact cardiac function. The acidic environment can interfere with myocardial metabolism and electrical activity, reducing contractility. It affects the heart's sensitivity to calcium, which is crucial for proper muscle contraction, leading to a decrease in both contractility and stroke volume.

Since all three conditions—heart failure, myocardial infarction, and