Find the INCORRECT pairing.

Options

A. SAN - Natural pacemaker
B. Heart rate - Pulse rate
C. Cardiac output - Heart rate x Stroke volume
D. Heart failure - Heart attack

Answer

To find the incorrect pairing from the options provided, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Evaluate the first option: SAN as a natural pacemaker**
- The Sinoatrial Node (SAN) is indeed known as the natural pacemaker of the heart. It is located in the right atrium and generates electrical impulses that initiate heartbeats, maintaining the heart rate.
- **Conclusion**: This pairing is correct.

2. **Evaluate the second option: Heart rate equals pulse rate**
- Heart rate refers to the number of times the heart beats per minute, while pulse rate is the number of times the arteries expand and contract due to the heartbeat. In a healthy individual, these rates are typically equal, as each heartbeat corresponds to a pulse felt in the arteries.
- **Conclusion**: This pairing is correct.

3. **Evaluate the third option: Cardiac output equals heart rate times stroke volume**
- Cardiac output is defined as the volume of blood the heart pumps per minute, which is calculated as the product of heart rate (beats per minute) and stroke volume (the amount of blood pumped with each beat). The formula is:
\[ \text{Cardiac Output} = \text{Heart Rate} \times \text{Stroke Volume} \]
- **Conclusion**: This pairing is correct.

4. **Evaluate the fourth option: Heart failure and heart attack**
- Heart failure refers to a condition where the heart is unable to pump sufficient blood to meet the body's needs, often leading to fluid buildup. In contrast, a heart attack (myocardial infarction) occurs when blood flow to a part of the heart is blocked, causing damage to the heart muscle.
- **Conclusion**: These two conditions are indeed different, making this pairing incorrect.

### Final Answer:
The incorrect pairing is **Option 4: Heart failure and heart attack**.

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