ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

The Basics of EKG Interpretation and Rhythm Recognition: Normal Sinus Rhythm

Updated on January 1, 2015

Learning to Read EKGs

Looking at an EKG can be very intimidating and difficult to understand for a lay person. EKG interpretation is a little tricky at first, but with some persistence, you can put together what the P wave, QRS, and T wave correspond to as the heart is working. Since Normal Sinus Rhythm is the easiest and most common rhythm, we are going to start there, then look at abnormalities starting from the atrial heart arrhythmias and working down to the ventricular arrhythmias. I will also cover ectopy and blocks later.

I hope I can shed some light on this particular skill and demystify it a little bit for the lay person.

Photo by: Brykmantra

EKG
EKG

Starting with "Normal Sinus Rhythm"

Looking at an EKG can be very intimidating and difficult to understand for a lay person. EKG interpretation is a little tricky at first, but with some persistence, you can put together what the P wave, QRS, and T wave correspond to as the heart is working. Since Normal Sinus Rhythm is the easiest and most common rhythm, we are going to start there, then look at abnormalities starting from the atrial heart arrhythmias and working down to the ventricular arrhythmias. I will also cover ectopy and blocks later.

Do not think that "Sinus Rhythm" has something to do with your nasal sinuses. The cardiac "sino-atrial" (SA) node is the pacemaker of the heart and is located on the right atrium of the heart.

I hope I can shed some light on this particular skill and demystify it a little bit for the lay person.

P wave EKG
P wave EKG

The P Wave

The P wave is the part of the EKG that shows where the atria are contracting, pumping blood down into the ventricles. If they are not functioning properly, you lose what is known as "atrial kick" and will lose between 5 and 30% of circulating blood pressure. After the initial atrial contraction, there is a repolarization to enable the atria to contract again, but it is generally not visible on an EKG, being obscured by the QRS complex.

The right atrium pumps blood into the right ventricle. The left atrium pumps blood into the left ventricle.

Occasionally, you may find P waves that are biphasic or inverted. A biphasic P wave looks like 2 smaller humps, one above and one below the baseline of the EKG. Inverted P waves look similar to normal P-waves, but upside-down. Generally, these are associated with something called a junctional rhythm. You shouldn't see them too often.

A normal P wave will be upright, and will be associated with a QRS complex. They should also be the same distance from the QRS complex. If they are not, you may be dealing with rhythm other than normal sinus rhythm or possible a heart block.

Some atrial arrhythmias: Atrial Fibrillation (A-Fib), Atrial Flutter(A-Flutter)

EKG QRS Complex
EKG QRS Complex

The QRS Complex

The QRS complex is the portion of the electrocardiogram that shows when the ventricles beat, forcing blood throughout the body. The right ventricle pumps blood through the pulmonary portion (that is, the lungs) while the left ventricle pumps blood throughout the rest of the body and brain, as well as the heart itself.

The QRS complex should be narrow and thin. If you print out your EKG, it will be 3 small boxes horizontally or smaller in length. If it isn't you may be dealing with a left or right bundle branch block. You will not be able to tell from a single rhythm strip if it is a bundle branch block, but if you do a 12-lead you can be trained to interpret and recognize them. A wide QRS can indicate old damage (like a prior heart attack) or be acute and require immediate medical attention. More often then not, when I see a wide QRS on an EKG, I presume that it is old damage, but question the patient about it. Even if the patient is not aware of a prior heart attack, unless he or she is symptomatic, a wide QRS is not a cause for sudden alarm.

Do not confuse a wide QRS with a premature ventricular contraction, known as a PVC. I will cover PVCs, and other ectopy, in another page.

Some things may change the shape of the QRS complex: Left Bundle Branch Block, Right Bundle Branch Block, low voltage QRS, bi-fascicular block

EKG T wave
EKG T wave

The T Wave

The T wave is the part of beat where the ventricles re-polarize and get ready to beat again. Remember that the atria repolarize as well, but you normally cannot see that on an EKG.

T wave shapes can change based on electrolyte imbalances. A tall, peaked T-wave generally means high potassium, known as hyperkalemia. Depressed T-waves can indicate low potassium, or hypokalemia.

Some associated abnormalities: ST segment elevation, ST segment depression, R on T phenomenon, inverted T waves

ECGs made easy
ECGs made easy

Practice

To get really good at EKG interpretation, you must expose yourself to it many times, so that you can become familiar with a normal sinus rhythm, as well as arrhythmias, blocks, and ectopy. If you want to further you learning, I started learning from ECGs Made Easy.

I would like to point out that ECG and EKGs are the same thing. EKG comes from the German Electrokardiogramm, whereas ECG comes from the English Electrocardiogram. EKG is traditional, ECG is more modern. Either work just fine. I use EKG myself.

Looking at different people's EKGs and seeing the many ways that a sinus rhythm can present itself is key to not making a mistake down the road.

I really hope I have helped you understand EKGs better.

Would you like to learn more? Atrial Fibrillation is next.

Have I helped you?

    0 of 8192 characters used
    Post Comment

    • shellys-space profile image

      Shelly Sellers 3 years ago from Midwest U.S.A.

      I would have to study a bit more, but you have explained what the EKG waves mean to the common person.

    • flycatcherrr profile image

      flycatcherrr 3 years ago

      I've always wondered what the up-and-downs of the EKG meant. We all know from watching too much medical-drama television that a "flat line" isn't exactly a good thing, but it is really interesting to have an explanation of what to look for in the waves & what kind of thing an EKG is telling the medicos when they look at the monitor.

    • Coffee-Break profile image

      Dorian Bodnariuc 3 years ago from Ottawa, Ontario Canada

      You are a good teacher Devin. Will keep this page handy, in my bookmarks, just in case I ever need to read an EKG.

    • Grifts profile image
      Author

      Devin Gustus 3 years ago

      @flycatcherrr: "Flat Lines" are known as asystole. The problem with "Flat Line" on Television is that they tend to defibrillate (CLEAR! SHOCK!) them, which, medically speaking, is completely wrong.

    Click to Rate This Article