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Today I figured out how to read an EKG.

While some people might say this skill should require 13 years prep school, four years college, four years medical school, and a specialty in cardiac electrophysiology, I say ... Pshaw! This is not rocket science! If so, there would be more combustion and potential for fast projectiles going wrong. (You know, I bet Rocket Scientist Christmas parties are really fun ... and imagine the July 4th Company Picnic!)

This is just cardiology, simple biological lines and lines. EKGs are even easier as they are a real-time moving map of the "wire" part and how they conduct electricity. Reading EKGs seems difficult because most cardiologists use long (expensive) words.

To warm up for the rest of this article, you might want to take a look at Today I Found Out's article, "How the Heart Works." Or, to cut a long story short, most healthy hearts pump blood around the body when stimulated by an electrical signal that travels in predetermined paths. This causes the heart cells to contract in exactly the right order, resulting in a magical four-chamber pumping action.

An EKG is a graph (hence called an electrocardiograph) that records the strength and direction of this electrical signal. Cables equipped with conductive swarms are located on different parts of the body so that the heart can be seen from different angles. If, at any given time, the electrical activity of the heart moves in the direction of the lead currently displayed, the line rises up on the graph (positive distraction). As the electrical activity moves away from the lead, the lead will drop (negative deflection). This diagram is traced by a pen on moving graph paper. In a normal healthy heart, an EKG that represents a full heartbeat looks like this:

This first small bump, affectionately known as the P-wave, represents the electrical signal that begins in a group of cells called the sinoatrial knot. This signal then travels through the atria (the smaller and upper two chambers of the heart), causing them to contract, forcing blood into the larger and stronger ventricles below.

The "PR Interval" segment represents a delay in the signal at another group of cells called the atrio-ventricular node. This delay gives the atria time to fully bring their head premium into the ventricles. With perfect timing, this signal continues through the Bundle of His. The signal splits and accelerates along the left and right bundle branches, gets to the Purkinje fibers, and turns north again. This stimulates the ventricular beefcakes to contract and bring their payload into the lungs and body (if the heart had biceps, the left ventricle would be the proverbial "gun show" ... that's such a pig of fame!).

The travel that this second contraction causes through the ventricles is represented by the QRS portion of the EKG. The larger T-wave that then kills our heartbeat is the repolarization of the ventricles. I know what you're thinking, either "What's going where now?" Or hopefully "Which wave represents the repolarization of the atria"? Well, the repolarization of the atria is embedded in the larger signal of the QRS and therefore not visible in the graphic.

This pattern is called normal sinus rhythm. It is the basic EKG of a normal healthy heart. Of course, there are deviations from the normal within the healthy population. For example, my friend is very fit and has a * huge * R-wave (hands off his large left ventricle, it's all mine!) And don't let me start with his early repolarization ... and no, in this case it is it not very early definitely not a bad thing).

However, anything outside of the normal range is analyzed along with the patient's symptoms to establish a functional diagnosis. There are different types of anomalies. Too long a PR interval is called a first-degree block. A QRS that lasts longer than 0.12 seconds is likely caused by a delay in one or both bundle branches called a bundle branch block. A complete lack of P waves and in their place a curved line combined with an irregular heartbeat is likely atrial fibrillation. What really excites a paramedic or ER doctor is when they see an elevation in the ST segment in a few consecutive leads. This is known as ST elevation myocardial infarction (heart attack) and generally results in a quick trip to the catheterization lab (if you can be more interested in what happens during a heart attack, see How a Heart Attack Works)). The list of irregular EKGs is really endless.

To mock the words of Leo Tolstoy, who seemed to know a thing or two about the heart: “Happy [hearts] are all equal; Every unhappy [heart] is unhappy in its own way. "If only Anna Karenina's problems could be solved by a trip to the cardiologist!

Bonus facts:

  • Each small box on the modern EKG strip corresponds to 0.04 seconds on the horizontal axis.
  • EKG paper is calibrated so that it moves past the pen at 25 mm per second.
  • The EKG was carried out in 1903 by the Dutchman Dr. Willhelm Einthoven, for which he received the Nobel Prize in 1924. More impressive, it also had a triangle named after him.
  • It's very rare, but it's possible that an EKG shows a flat line (asystole) when the heart is actually still beating and generating a pulse. For this reason, it is common practice to confirm a patient's death by looking for asystole in more than one line.
  • Conversely, it is also possible and more common for an EKG to show cardiac activity and even normal sinus rhythm after a person dies and their heart stops pumping blood. This is known as PEA (pulsationless electrical activity) and shows what is left of the heart's electrical system intact after the muscle itself has failed.
Today I figured out how to read an EKG. While some people might say this skill should require 13 years prep school, four years college, four years medical school, and a specialty in cardiac electrophysiology, I say ... Pshaw! This is not rocket science! If it were, more combustion and the potential for faster projectiles would be gone