Heart Rate and Pulse Rate

The terms heart rate and pulse rate are often used interchangeably but they have some striking features which distinguish both of them. The term heart rate is referred to the frequency or number of contractions of the heart (beats) in a minute. It is measured as beats per minute (bpm). A person’s normal resting heart rate (RHR) is 70-80 beats per minute (bpm). Pulse rate refers to the arterial pulse from the sudden arterial expansion. It occurs as a result of the sudden filling of the aorta with blood and this flow is taken down to the system of arteries and vessels.

Site and Techniques to Measure Pulse Rate

A proper technique is essential to get accurate results. To measure the pulse rate the patient should be in a resting or reclined posture.

Sites to Palpate to obtain Pulse Rate

In the upper extremity:

• Carotid artery
• Subclavian artery
• Radial artery
• Ulnar artery
• Brachial artery

In the lower extremity:

• Posterior tibialis artery
• Dorsalis pedis artery
• Femoral artery
• Popliteal artery

In obese patients specifically, deep palpations may be necessary to obtain subclavian, popliteal, or femoral pulse rates. The pulse rate can be named based on the area the individual is palpating. For example, peripheral pulse, carotid pulse, etc. 

Factors influencing Heart Rate

1. Age

At an early age, there is a high vagal tone that leads to a decrease in heart rate values whereas, in old age, the heart rate gets slightly higher owing to a fall in vagal tone. 

• Foetal HR is 140-150 bpm
• At birth, the heart rate is around 130-140 bpm
• In adults, it ranges from to 70-80 beats per minute
• In old age, heart rate reaches up to 100 beats per minute

2. Sex

• Females when compared to males have slightly higher values of heart rate due to low systemic blood pressure. (Marey’s law: heart rate is inversely proportional to the systemic blood pressure)

3. Body Temperature

4. Drugs

• Various drugs are known to increase or decrease the heart rate Epinephrine and norepinephrine are known to bring an elevation in heart rate values

5. Exercise

• The relationship between exercise or physical exertion lies in linearity with that of heart rate

6. Emotional Stimulus

• Stimulus-like happiness and excitement elevate heart rate (induces tachycardia) and hypertensive conditions
• The stimulus of grief, sadness, shock, or apprehension induces bradycardia and hypotensive condition

7. Respiration

• Heart rate is known to elevate during the inspiratory phase and decrease during the expiratory phase. This phenomenon is referred to as sinus arrhythmia

8. Painful stimulus

• Pain in superficial segments causes tachycardia and a rise in blood pressure
• It is due to the activation of the sympathetic system
• Pain in deep segments of the body is known to cause bradycardia and fall in systemic blood pressure

9. Diseases 

Factors influencing Pulse Rate

1. Presence of reflected, resonance, or standing waves
2. Variability in the elastic and distensible properties of the blood vessels.
3. The changes in the calibre of the peripheral arteries distributed in upper and lower body segments
4. Distance: As the distance between the heart to the peripheral artery increases, distortion of the arterial pulse would be greater peripherally.
5. The size of pulse rate is also dependent on left ventricular ejection volume and the ejection rate.

Based on Deviation from Normal

There is a term for every deviation from a normal value of heart rate and pulse rate in terms of frequency, volume, and amplitude. For example,

• Tachycardia: refers to an increase in the heart rate (HR)
• Bradycardia: refers to a decrease in the heart rate (HR)
• Hyperkinetic Pulse: a low volume and low amplitude pulse is called as 
• Hypokinetic Pulse: a high volume and large amplitude pulse are called a hyperkinetic pulse.

Base on Clinical Presentation Due to Alteration in Pulse Rate and Heart Rate

1. Thyrotoxicosis: It is associated with an increase in resting heart rate. It is a condition due to a hypersecreting thyroid gland. 
2. Hypoxia: a person suffering hypoxia displays an increased heart rate to meet the oxygen demands.
3. Intracranial tension: increased intracranial tension alleviates blood flow to the medulla. This causes a decrease in heart rate (bradycardia). Cushing reflex refers to the reflex where high intracranial tension is associated with bradycardia.
4. Sinus arrhythmia: During inspiration, the pulse rate goes up and falls slowly during expiration. 
5. In atrial flutter or atrial fibrillation, there is evidence of irregularity in pulse rate.
6. Inadequately perfused tissue gives a sign indicating a low volume of the pulse. 
7. In patent ductus arteriosus (PDA), hyperthyroidism, fever, stress, aortic regurgitation, anemia, venous fistulas, etc. there could be evidence of hyperkinetic pulse.
8. Hypokinetic pulse is evident in pericardial tamponade, myocardial infarction, cardiomyopathy, pericarditis, etc.

Conclusion

The heart rate and pulse rate are synonymous terms which although refer to the number of heart contractions (beats) that occurred in a minute, share some distinguishing characteristics. Both of them can be altered by various factors. Any imbalance arising is capable of inducing changes in the normal values of heart rate and pulse rate.