ANATOMY

Detailed explanation-1: -A normal resting heart rate for adults ranges from 60 to 100 beats per minute. Generally, a lower heart rate at rest implies more efficient heart function and better cardiovascular fitness.

Detailed explanation-2: -For regular heart rhythms, heart rate can easily be estimated using the large squares (0.2s) on an ECG. Simply identify two consecutive R waves and count the number of large squares between them. By dividing this number into 300 (remember, this number represents 1 minute) we are able to calculate a person’s heart rate.

Detailed explanation-3: -A healthy human heart beats 72 times per minute which states that there are 72 cardiac cycles per minute. The cardiac cycle involves a complete contraction and relaxation of both the atria and ventricles and the cycle last approximately 0.8 seconds.

Detailed explanation-4: -At 100 bpm heart rate the cardiac cycle duration is = 600 msec. A longer diastolic time fraction improves ventricular filling and coronary perfusion time.

Detailed explanation-5: -There is an inverse relationship between the duration of cardiac cycle and heart rate. Hence when the heart rate is increased to 120 beats per minute, the cardiac cycle duration will be about 0.5 sec.