Why does cardiac output decrease when heart rate is greater than 160

The heart relies on expansion and contraction to exert force on the blood, allowing blood to flow throughout the body, and this contraction and expansion is called heartbeat. The heart's beating pattern is relatively constant, within a certain safe range, usually calculated in minutes. A heart rate that is too fast is very bad for your health. For example, why does cardiac output decrease when the heart rate is greater than 160? Let’s take a look at the explanation below.

Cardiac output is the product of stroke volume and heart rate. As the heart rate increases, cardiac output increases, but there is a certain limit. For example, if the heart rate is >170 beats/min, the ventricular filling time is significantly shortened, the filling volume is reduced, the stroke volume is reduced to about 50% of the normal level, and the cardiac output decreases. If the heart rate is too slow, <40 beats/min, the cardiac output also decreases. This is because the heart's diastole is too long, and the ventricular filling has already reached its limit. Prolonging the diastole time will not increase the stroke volume accordingly. If the heart rate is too fast or too slow, cardiac output will be reduced.

The amount of blood pumped out by the heart per minute decreases, which may be due to the following reasons:

1. Decreased ejection, insufficient blood supply, and increased peripheral resistance.

2. Myocardial preload. and ventricular end-diastolic volume,

3. Myocardial afterload and arterial blood pressure.

4. Myocardial contractility.

5. The specific reason for the heart rate change can be explained as follows: When the heart rate exceeds 180, the diastole is significantly shortened, resulting in insufficient ventricular filling with blood, which causes the stroke volume to decrease and the cardiac output to decrease.

People of different ages have different heart rates. The younger the age, the faster the heart rate. If the heart rate exceeds the normal range, it is called a tachycardia. The accelerated heart rate caused by illness is most common when you have a fever. For every 1°C increase in body temperature, the heart rate can increase by 10 to 15 beats per minute. Therefore, diseases that can cause fever will often result in an accelerated heart rate, but typhoid patients are an exception. The pulse of typhoid patients is relatively slow, which is called a relatively slow pulse. This is an important characteristic of typhoid.

If your heart rate continues to be too fast, you should consult a doctor. The normal pulse rate of an adult at rest is 60-100 beats per minute, which may vary with factors such as age, gender, labor and mood. Generally, women speed up faster than men, young children speed up faster than adults, and the elderly speed up slower. It may speed up temporarily during exercise or emotional excitement, and slow down during rest and sleep.