Question

A patient’s chart reveals that he has a cardiac output of 7,500 mL/min and a stroke volume of 50 mL. What is his pulse (in beats per minute)?

Short answer

The pulse is 150 beats per minute.

Step-by-step solution

- Understand the Relation

To find the pulse rate, use the formula for Cardiac Output (CO): \[ CO = HR \times SV \] where CO is cardiac output, HR is heart rate, and SV is stroke volume.

- Identify Given Values

The problem provides the following values:\[ CO = 7500 \text{ mL/min} \]\[ SV = 50 \text{ mL} \]

- Rearrange the Formula

Rearrange the formula to solve for Heart Rate (HR): \[ HR = \frac{CO}{SV} \]

- Substitution and Calculation

Substitute the given values into the rearranged formula: \[ HR = \frac{7500 \text{ mL/min}}{50 \text{ mL}} \]Calculate the heart rate: \[ HR = 150 \text{ beats per minute} \]

Key concepts

Heart Rate Determination

Heart rate refers to the number of times the heart beats per minute. To determine it in the context of the exercise, you need to understand the relationship between cardiac output and stroke volume.
Cardiac output (CO) is the amount of blood the heart pumps in one minute. Stroke volume (SV) is the amount of blood pumped out of the heart with each beat. The heart rate (HR) can be determined using the formula: \[ HR = \frac{CO}{SV} \]
Here's where it all ties together:

• Given the cardiac output as 7,500 mL/min.
• Given the stroke volume as 50 mL.

You simply plug these values into the formula to discover the heart rate. It simplifies to: \[ HR = \frac{7500 \text{ mL/min}}{50 \text{ mL}} = 150 \space\text{beats per minute} \] This means the heart beats 150 times per minute.

Stroke Volume

Stroke volume is a critical measurement in cardiac physiology. It represents the volume of blood pumped out of the left ventricle per heartbeat. Knowing the stroke volume helps in assessing how well the heart is functioning. In the given exercise, the stroke volume is 50 mL.
To calculate stroke volume, you can use various formulas, depending on the available data. Commonly, it is measured using:

• Ultrasound imaging
• Echocardiography

It can also be estimated using the difference between the end-diastolic volume (EDV) and end-systolic volume (ESV): \[ SV = EDV - ESV \] A typical stroke volume ranges from 60 to 100 mL per beat in a healthy individual. Comparing this to the given value of 50 mL helps in understanding the efficiency of the heart's pumping action.

Cardiac Physiology

Cardiac physiology is the study of the heart's function. It's crucial for comprehending how blood circulates throughout the body. Key concepts in cardiac physiology include:

• Heart rate (HR)
• Stroke volume (SV)
• Cardiac output (CO)

Cardiac output is a significant parameter because it reflects the volume of blood the heart ejects in one minute. It's calculated as the product of heart rate and stroke volume: \[ CO = HR \times SV \] Normal cardiac output ranges from 4 to 8 liters per minute in a resting adult. This measurement varies based on factors such as:

• Physical activity level
• Body size
• Heart health

Understanding these concepts will enhance your grasp of how the heart functions and adapitates to different conditions, ensuring efficient circulation and oxygen delivery throughout the body.