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Instructors' Collection ECG of the WEEK, July 26, 2014 __ Hyperkalemia

Sun, 07/27/2014 - 00:29 -- Dawn

This ECG was obtained from a patient who was suffering from renal failure and had a serum potassium level of 6.8 mEq/L.  It shows some of the earliest ECG signs of hyperkalemia.  There are tall, sharply-peaked T waves in many leads.  There is an irregular, bradycardic rhythm.  We can just barely see P waves, but they will soon flatten out and disappear.  At this level of hyperkalemia, we can expect to see conduction disturbances and bradycardia.  Caution:  hyperkalemia can progress and become life-threatening very quickly.

Potassium is primarily an intracellular electrolyte.  It is necessary for proper electrical functioning of the heart.  Extracellular  serum potassium can rise due to renal failure, or taking potassium supplements, potassium-sparing diuretics, or ACE inhibitors.

ECG signs may vary among people with hyperkalemia, but in general:

Serum K levels of 5.5 mEq/L or greater can cause repolarization abnormalities like tall, peaked T waves.

Serum K levels of 6.5 mEq/L or greater cause progressive paralysis of the atria.  The P waves will lose amplitude, widen and flatten.   The PR segment will lengthen. Eventually, the P waves will disappear.

Serum K levels of 7.0 mEq/L or greater cause conduction abnormalities.  The QRS will widen and the rate will slow.  There may be bundle branch blocks or fascicular blocks.  The QRS morphology will be bizarre - not necessarily showing a typical bundle branch block pattern.  AV blocks may occur, with either ventricular or junctional escape rhythms.

As the patient's condition worsens and the serum potassium rises, the QRS and T waves lose amplitude, widen, and may seem to blend together.  

At levels above 8.0 mEq/L, we may see what looks like a bizarre idioventricular rhythm, or a sine wave pattern.  This sine wave pattern signals cardiac arrest is imminent.

For a comprehensive discussion of hyperkalemia on the ECG with many examples of the different phases, go to Life In The Fast Lane.  Ed Burns has compiled a very instructive collection of ECGs that illustrate the progression of this deadly condition.

Dr. Steve Smith's blog has several very good discussions on the subject.  For a comparison of tall T waves caused by several factors, including hyperkalemia, go to Dr. Smith's Blog.

It is important the patient with hyperkalemia is treated rapidly, as it can be rapidly fatal.

ECG Basics: Atrial Flutter With 2:1 Conduction Ratio

Thu, 07/17/2014 - 17:40 -- Dawn

One of the most frequently misdiagnosed rhythms, atrial flutter with 2:1 conduction often masquerades as sinus tach.  Sinus tach usually has an obvious cause, such as exercise, severe hypovolemia, or age less than 6 months.  Atrial flutter usually produces flutter waves (P waves) at a rate of 250 - 350 per minute.  Therefore, a 2:1 conduction ratio would result in a heart rate of about 125 - 175 bpm).  

Often, students are taught about atrial flutter using an electronic rhythm generator or a book with limited illustrations, and they become acustomed to seeing atrial flutter with 3:1 or 4:1 conduction.  The flutter waves are very easy to see in such a situation.  However, the AV node, if not affected by medication, is usually well able to conduct at a rate of 150 or more.  Therefore, the physiological block that protects us from extreme rates will keep the heart rate around 150 bpm in atrial flutter.

This is a single rhythm strip.  It can be VERY helpful to look at multiple leads to look for flutter waves.  See this week's Instructors' Collection ECG of the WEEK for the SAME patient's 12-Lead ECG.  Also, your students should be reminded that sinus rhythms, including sinus tach, tend to change rates based on the needs of the patient.  For example, as a patient is treated for his/her condition, the rate may improve by slowing.  Conversely, if the condition becomes worse, or the patient is stressed, the rate may increase.  Atrial flutter, like all re-entry tachycardias, tends to stay at a steady rate unless the conduction ratio changes.

Show your students that the flutter waves are CONTINUOUS.  That is, they don't pause for the QRS.  The second illustration shows the flutter waves highlighted, to aid in seeing the continuous line of flutter waves.

jer5150's picture

ECG Challenge donated by Guru member "chireu".

This is a derived (i.e., EASI) 12-lead ECG donated to the ECG Guru by new member "chireu".  The only history they were able to provide was one of possible atrial flutter but that was uncertain.  How would you interpret this ECG?

jer5150's picture

Jason's Blog: ECG Challenge for the month of July, 2014.

This is an ECG I performed a couple of years ago on an asymptomatic 83-year old man as an outpatient procedure. 

The computer interpreted this as:  "Marked sinus bradycardia [with] Frequent Premature ventricular complexes".  IS THE COMPUTER CORRECT?  Is there more than one plausible interpretation?  What is the differential diagnosis?

ECG Teaching Series: ST Elevation M.I.

Sat, 06/21/2014 - 15:23 -- Dawn

This series shows the evolution of ECG changes in anterior wall M.I. secondary to occlusion of the proximal left anterior descending artery.  The patient is an 88-year-old woman with chest pain.  She was designated a "cardiac alert" from the field by paramedics.  Her proximal LAD was opened and stented in the cath lab.  We do not have follow-up information on her.

The first ECG in the series, titled "12-Lead 3", shows ST elevation at the J point in V1 through V3.  In addition, the T waves are "hyperacute" - tall, broad, and asymmetrical. This can be an early, transient sign of myocardial injury.  Slight reciprocal depressions are seen in the inferior leads.  Lead V4 has a T wave inversion that is out of place with the progression of the T waves in V3 and V5.  Lead placement may be to blame.  Hyperacute T waves in a patient with chest pain should be taken very seriously.

The second ECG, titled "12-Lead 4", shows continued elevation at the J point in Leads V1 through V3, with a lessening of T wave amplitude.  In addition, Lead aVL is showing some T wave changes. The T wave is biphasic, and may be about to become inverted.  This is not an improvement!  V1 through V3 show us the anterior-septal wall, and an M.I. here indicates occlusion in the LAD.  Leads I and aVL show the high lateral area of the anterior wall, and damage here is an indicator that the occlusion is proximal.

The third ECG, titled "12-Lead 5", shows a "maturing" of the ST segment elevation.  Even though there is some significant artifact, we can see that the ST segment in V1 is coved upward, and the ST segment in V2 is flat.  Both shapes are abnormal, and a sign of CAD.  The T waves have become less pronounced, but V2 looks as if the T wave may become inverted in the near future.  V3 looks improved in this image.

The patient's clinical symptoms did not improve during these ECG changes.  Hyperacute T waves are not a definitive sign of STEMI, but they provide a highly visible warning that may catch attention.  They definitely are an indication to run serial ECGs, as these paramedics did.


Glossary of ECG Terms by Dr. Ken Grauer

Fri, 04/25/2014 - 17:20 -- Dawn
Dr. Grauer will continually expand and update his ECG terms glossary, so follow this link to view it in the latest version:  Glossary of ECG Terms.

This Glossary of ECG Terms is intended to accompany Dr. Grauer's newest publication, "A 1st Book on ECGs-2014".   It is not meant to be a complete glossary of all ECG terms, but is very good for helping your students navigate the early lessons.  They will  find Dr. Grauer's book very helpful, also.


Wed, 01/15/2014 - 20:55 -- Dawn


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The ECG Guru is committed to providing high-quality resources for ECG instructors and students FREE of CHARGE and FREE of COPYRIGHT.  We do rack up some expenses keeping the website going.  We came up with the idea of fund raising while also providing a product that we know our members and visitors will LOVE. 

Go to the STORE to learn more about this shirt.

Broken Heart

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