ECG Guru - Instructor Resources

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Instructors' Collection ECG: Atrial fibrillation and Type 2 M.I.

Sat, 07/20/2019 - 13:41 -- Dawn

The Patient:     This excellent teaching case was donated to the ECG Guru by our friend, Sebastian Garay (who is an ECG Guru himself).  It was taken from a 33-year-old man who was complaining of chest pain and palpitations. He reported a similar episode about six months prior, but failed to follow up with cardiology. Was told by his medical care provider that he had atrial fib.

The ECG:      We are able in this case to provide a 12-lead ECG with each lead recorded for the entire width of the paper. This has the advantage of producing twelve ten-second rhythm strips.  Page one contains the limb leads, and page two shows us the precordial leads.

The rhythm is atrial fibrillation, with a heart rate of 133 bpm and an irregularly irregular rhythm. The QRS axis is extreme left at about 75 degrees.  This has caused Leads II, III, and aVF to be negatively deflected, and aVR and aVL to be positive. Lead I is biphasic, low voltage, and mostly positive, indicating that the axis travels almost perpendicular to Lead I, but slightly toward it.

The machine mistakenly gives us a reading for PR interval and P wave axis, even though there are no P waves.  The QRS is on the wide side without being abnormal at .10 seconds (100 ms). The QTc is within normal limits, although it might be considered “borderline”, with 431-450 usually considered borderline.

ECG Glossary from Dr. Ken Grauer

Sat, 06/08/2019 - 14:16 -- Dawn

Are you looking for a comprehensive ECG glossary that goes beyond simply defining words? Dr. Ken Grauer, who is the ECG Guru's Consulting Expert, has a Glossary available on his website that explains the terms.  Instructors and students alike will benefit from having this glossary readily available.  The glossary is exerpted from his e-Publication, "A 1st Book On ECGs - 2014", available on Amazon.

ECG Basics: 2:1 AV Block

Fri, 06/07/2019 - 15:48 -- Dawn

Second-degree AV block can either be Type I (Wenckebach) or Type II.  In either case, some P waves are conducted to the ventricles, and some are not. Type I blocks usually occur in the AV node, and are often benign. Type II blocks are more often "sub-Hisian", or fascicular blocks, and are more likely to progress to higher levels of AV block and bradycardia.  When a second-degree AVB is conducted in a 2:1 ratio, it is difficult to differentiate Type I from Type II.  Features that favor the diagnosis of Type I are narrow QRS complex and the non-conducted P waves land on the previous T waves - during the refractory period of the ventricles.

Type II blocks are more likely to have a wide QRS with a bundle branch block morphology.  That is because Type II blocks often reflect serious fascicular disease.  A typical Type II block is a persistent bifascicular block (ex: RBBB and left anterior hemiblock)) with an intermittent block in the third fascicle.  Another way to think of it is an intermittent tri-fascicular block. If that one remaining fascicle stops conducting, the patient will be in complete heart block.

Signs of Type II blocks include the wide QRS and also two or more non-conducted P waves in a row.  Also, P waves that are "out in the open", away from the refractory period, but fail to conduct are an ominous sign.

One strategy for reacting to a 2:1 block is to first assess the ventricular rate (54 bpm in this example).  Determine if it is adequate for the patient's hemodynamic stability.  If not, act to increase the rate.  Otherwise, it may be prudent in the stable patient to watch the rhythm strips for a while.  Sometimes, two p waves in a row will conduct - unmasking either progressive prolongation of the PR interval (Type I) or stable PR intervals (Type II). 

The patient in this example was having an inferior wall M.I.  The ST elevation will not always show up on a monitor strip, as it does here.  A 12-lead ECG is the minimum standard for evaluating for coronary artery disease and acute M.I.  It is possible that the 2:1 block will disappear when the atrial rate (about 108 here) is slowed.

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1924:  Willem Einthoven wins the Nobel prize for inventing the electrocardiograph.

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