National Physical Therapy Examination (NPTE) Practice Exam

Rate pressure product is most indicative of which cardiac factor?

1. Stroke volume

2. Cardiac output

3. Pulse amplitude

4. Myocardial oxygen demand

The correct answer is: Myocardial oxygen demand

Rate pressure product is a clinical measurement used to estimate myocardial oxygen demand, which is crucial for assessing the heart's workload. It is calculated by multiplying the heart rate by the systolic blood pressure. This product provides insight into how hard the heart is working and the amount of oxygen the myocardium needs during various activities or in response to stress. As heart rate increases or blood pressure rises, the rate pressure product increases as well, indicating a corresponding increase in myocardial oxygen consumption. This relationship is essential for understanding conditions such as angina, where the heart may not receive sufficient oxygen due to narrowed coronary arteries. The other factors—stroke volume, cardiac output, and pulse amplitude—play roles in overall cardiovascular function but do not directly correlate with the myocardial oxygen demand as defined by the rate pressure product. Stroke volume pertains to the amount of blood ejected by the heart in one contraction, cardiac output is the volume of blood the heart pumps per minute, and pulse amplitude refers to the strength of the pulse felt in blood vessels. While these factors contribute to cardiac function, they do not specifically represent the oxygen needs of the myocardium in the same way that the rate pressure product does.