The P wave is a small semi-circular shape located right before the tall QRS complex. It represents the electrical activity of the atria (“atrial depolarization”), which are the two small chambers located at the top of the heart. The QRS complex is the tallest most visible aspect of the ECG trace. It is usually pointy, like a tall, thin triangle and very easy to recognize. It represents the electrical activity of the ventricles (“ventricular depolarization”), which are the two large chambers located at the bottom of the heart that forcefully pump blood throughout the body. The ST segment directly follows the tall QRS complex. It is actually the flat area prior to the next semi-circular shape on the ECG (which is the T wave). The importance of this flat segment (the ST segment), located right after the QRS complex, is that it provides important information to physicians about things such as potential heart attacks.
Often, it will be a fractionated number as the complexes will not land exactly on the squares; for instance, 2. 4 squares or 3. 6 squares may separate adjacent QRS complexes. There are normally 5 little squares embedded in each large square, allowing you to approximate the distance between QRS complexes to the nearest 0. 2 units (because 1 big square divided into 5 small squares gives you markings every 0. 2 units).
Note that a normal heart rate is between 60 to 100 beats per minute. [7] X Trustworthy Source Mayo Clinic Educational website from one of the world’s leading hospitals Go to source Knowing this can help to guide whether you are on course with your heart rate calculations. However, 60 to 100 beats per minute is only a loose guideline. Many athletes who are in excellent physical shape have lower resting heart rates. [8] X Trustworthy Source Johns Hopkins Medicine Official resource database of the world-leading Johns Hopkins Hospital Go to source There are also disease states that can provoke unhealthy slower heart rates (called pathological bradycardias), and diseases that can lead to an unnaturally accelerated heart rate (called pathological tachycardias). Speak to a physician if the person you are calculating heart rate for appears to have an abnormal value.
