Myocardial oxygen demand decreases by all EXCEPT
**Core Concept**
Myocardial oxygen demand is influenced by several factors, including the heart rate, contractility, and afterload. The demand for oxygen is highest during periods of increased contractility, heart rate, or afterload, which can lead to ischemia in the presence of coronary artery disease. Understanding the factors that influence myocardial oxygen demand is crucial for managing patients with cardiovascular disease.
**Why the Correct Answer is Right**
The correct answer is the factor that does not decrease myocardial oxygen demand. Myocardial oxygen demand is directly proportional to the heart rate, contractility, and afterload. Decreasing these factors can lead to a reduction in myocardial oxygen demand. This is why beta-blockers are often used to reduce the heart rate and contractility in patients with heart failure or coronary artery disease.
**Why Each Wrong Option is Incorrect**
**Option A:** Decreasing contractility, such as with beta-blockers, decreases myocardial oxygen demand.
**Option B:** Reducing afterload, such as with vasodilators, decreases myocardial oxygen demand.
**Option C:** Increasing contractility, such as with inotropes, increases myocardial oxygen demand.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that myocardial oxygen demand is directly proportional to the heart rate, contractility, and afterload. Managing these factors is crucial for preventing ischemia in patients with coronary artery disease.
**Correct Answer: C. Increasing contractility increases myocardial oxygen demand.**