In order to interpret an ECG, it is necessary to understand the different parts of normal sinus rhythm and how they appear. The first thing to look for is what is called a P wave; this is a small elevation before the QRS complex. Next, look at the PR interval; this is measured by counting the small squares from the start of the P wave and ends with the R wave. The PR interval represents the phase of atrial depolarization. The average PR interval should be between 0.12 and 0.20 seconds or 3 to 5 small squares. After the PR interval, it is important to examine the QRS complex; in other words, ventricular depolarization. There should be a QRS following each P wave and it should last no more than 0.12 seconds or 2 ½ small squares. Additionally, the S wave should return to baseline and not be elevated or decreased. After the QRS complex, a T wave should be present as a small elevation from the baseline. The S wave and the T wave are together called the ST interval and represent ventricular repolarization; normally this should be 0.20 seconds or less. All of this represents a complete cycle of depolarization and repolarization of the heart's atria and ventricles to produce cardiac output. The next thing to look at is the RR interval; it's simply a matter of looking at the distance between each QRS complex and seeing if they are evenly spaced and regular. There should not be much variation in the distance between each R wave. Now that I have described what normal sinus rhythm looks like, I will now give the different descriptions of the different abnormal ECG patterns that exist. All abnormal rhythms indicate different issues or problems regarding the heart; therefore, I will also discuss the different treatments for each abnormal rhythm. With...... middle of paper ...... feeling every second beat, while trigeminism is when every third beat is a PVC. Some possible causes are electrolyte imbalances, hypoxia, stress, and caffeine. Lidocaine may be used as a temporary solution, although if symptoms are severe enough ablation may be considered. An ablation is a minimally invasive procedure in which radiofrequency waves are used to destroy the tissue where the early beat is originating. Works Cited • Bradycardia (slow heart rate). WebMD. March 13, 2014 http://www.webmd.com/heart-disease/tc/bradycardia-slow-heart-rate-overview• Sinus arrhythmia. Pediatric cardiologist, diagnosis and treatment of disorders. March 13, 2014 http://pediatricheartspecialists.com/articles/detail/sinus_arhythmia• Wolff-Parkinson-White syndrome. MedlinePlus, reliable health information for you. March 13, 2014 http://www.nlm.nih.gov/medlineplus/ency/article/000151.htm