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ECG Challenge: Wide-complex Rhythm

Wed, 02/15/2017 - 22:20 -- Dawn

This ECG Challenge is taken from a 95-year-old man.  We do not know his clinical information, except that he called 911 for assistance.  We also do not have information on his past medical history.  The QRS complexes are wide, and there are P waves present.  What do you think the etiology of this rhythm is?

Feb. 22, 2017 UPDATE:  The wide complexes in this ECG indicate an intraventricular conduction defect.  The most likely IVCD at this man's age is left bundle branch block.  However, the morphology of the QRS complexes in V5 and V6 are NOT typical of LBBB.  Usually, there is very little or no S wave in those leads.  We cannot confirm that lead placement is correct, and failing to place the left sided electrodes (V4 through V6) correctly can affect the transition of the R waves in the precordial leads.  It would be SO helpful to know more about this patient, of course, but a lot is possible by age 95.

For a more in-depth look at this ECG, please refer to the Comments below.

ECG Basics: Onset of Atrial Fibrillation

Fri, 12/16/2016 - 19:44 -- Dawn

This strip shows the onset of atrial fibrillation.  A fib can be "paroxysmal," meaning that it has a sudden onset, but then stops spontaneously, usually within 24 hours to a week.  A fib can also be classified as "persistent", meaninging that the a fib lasts more than a week.  It can stop spontaneously, or be halted with medical treatment.  "Permanent" a fib is a fib that is resistent to treatment.  

The first three beats in this strip represent sinus rhythm at 75 beats per minute.  At the onset of atrial fibrillation with beat number four, the rhythm becomes irregularly irregular, and the rate is around 140-150 bpm. We can expect new-onset a fib to have a fast ventricular rate, as the atria are sending hundreds of impulses to the AV node every minute. The AV node will conduct as many of those impulses as it can to the ventricles.  Most AV nodes can easily transmit 130-160 bpm.  In a fib, the atria are quivering, not contracting. Because of this fibrillation of the atrial muscle, a fib has no P waves, and therefore, no "atrial kick".  The contribution of the atria to cardiac output (25-30%) is lost. An extremely fast rate can also lower output and overwork the heart, so one treatment goal for a fib is to lower the rate.  This can be done independently of attempts to convert the rhythm.

During a fib, blood clots can form in parts of the atria, especially the left atrial appendage.  If sinus rhythm is restored after these thrombi form, they can embolize and travel to the brain, causing stroke.  Before electively converting atrial fib to a sinus rhythm, the patient may need to be anticoagulated.

 

Instructors' Collection ECG of the WEEK: Incorrect Machine Interpretation

Wed, 03/01/2017 - 23:07 -- Dawn

This ECG is presented as an example of INCORRECT MACHINE INTERPRETATION.  While there are many abnormalities in this ECG, it does not represent a paced rhythm. While there are exceptions, most paced rhythms represent either AV sequential pacing, right ventricular pacing, or bi-ventricular pacing.

RECOGNITION OF A PACED RHYTHM

Recognizing a paced rhythm can be difficult in some cases. Because pacemakers now have so many programmable features, there is a wide variety of ECG changes associated with them.  Pacer “spikes” can be difficult to see in all leads.  Finding evidence of the device on the patient’s chest or via patient history is a big help in reminding us to scrutinize the ECG for paced rhythm.

An AV sequential pacemaker or a right ventricular pacemaker will pace the ventricles via the right ventricle.  This produces a WIDE QRS and a leftward axis, often causing Leads II, III, and aVF to be negative and aVL and aVR to be positive.  Along with the wide QRS, we will see DISCORDANT ST CHANGES.  That is, there will be ST depression and T wave inversion in leads with positive QRS complexes and ST elevation and upright T waves in leads with negative QRS complexes.

Bi-ventricular pacing can be a little more complicated to recognize, as the QRS can be narrow, with signs of fusion between the wave produced by the LV electrode and the RV electrode.

The frontal plane axis is usually far right – aVR will be positive.  Lead I will be negative.

The machine is wrong:  there is no indication of a pacemaker, and P waves are present, even though they are not noted in the "PR Interval" or "P Axis".

SO, THIS IS NOT A PACED RHYTHM – WHAT IS IT?

There are many abnormalities in this ECG, and they can be due to many different conditions. All ECGs should be evaluated in a clinical setting, with the patient’s symptoms, signs, and medical history all considered.  That being said, I will point out what I see to be abnormal, and await our readers’ and experts’ opinions.

The rhythm is sinus, at a rate of 62 bpm.  The PR interval is not given by the machine, but P waves are very obvious, and the PR interval is about .24 seconds, a first-degree AV block.  The QRS complex is measured by the machine as 114 ms wide (.11 seconds).  This is barely under the 120 ms usually required for diagnosis of wide-complex rhythm, and many would consider it adequate for a wide QRS.  If we accept that this is a wide-complex QRS, then we should look for the ECG criteria for RIGHT BUNDLE BRANCH BLOCK and  LEFT BUNDLE BRANCH BLOCK. In RBBB, there will be an rSR’ pattern in V1 and a small s wave in Leads I and V6.   In LBBB, Leads I, V5 and V6 should have a broad, monomorphic, upright QRS.  In this ECG, V5 and V6 have small s waves that contribute to the total width of the QRS, while the R waves are narrow in appearance. The term for a wide-complex, supraventricular rhythm that does not meet the criteria for either right or left BBB is INTRAVENTRICULAR CONDUCTION DELAY. (IVCD)

The frontal plane axis is -17 degrees, which is normal, but slightly to the left.  That would be typical of left bundle branch block.  However, the pronounced S wave in Lead II and the deep S wave in Lead III are not typical.  In a study of S waves in these two leads, they have been found to be very rare in healthy hearts, and often associated with M.I. and cardiomyopathy.  The abnormal S waves studied were deeper than the R wave was tall, however. S waves can be seen in Leads II and III in ventricular conduction defects that cause wide QRS – like LBBB and IVCD .

The ST segments and T waves in this ECG are clearly abnormal. T waves are inverted in Leads II, III, aVF; Lead I; Leads V4, V5, and V6; and they are biphasic in V3 as they transition from V2 (positive) to V4 (negative).  The inverted T waves are very shallow in most leads, so it is hard to determine if they are symmetrical (indicating ischemia) or asymmetrical (with many causes).   In cases of wide QRS, we expect to see DISCORDANT ST AND T WAVE CHANGES.  That is, the ST and T waves will go opposite the main direction of the QRS.  Right chest leads like V1 and V2, which have negative QRSs will have some ST elevation and upright T waves.  The opposite is true over the left side, where we expect upright QRS complexes (I, aVL, V5, V6) and, in the case of wide QRS, depressed ST segments with inverted T waves.  This is seen for the most part in this ECG, but Leads III and aVF seem to have CONCORDANT STs.  It would be very helpful to know this patient’s current symptoms and recent medical history.

There are also Q waves in V1 and V2 that meet the criteria for "pathological Q waves", a sign of necrosis.  However, large Q waves (or more accurately, loss of initial R waves) are common in V1 and V2, and may not be related to acute M.I.  This is where knowing the patient's presentation and history would be very helpful. 

As stated, the MAIN REASON for posting this ECG is to show students, beginners and advanced alike, that the machine’s interpretation should be taken with a “grain of salt”, and the interpreter should never rely solely on that interpretation.  But we must also make the point that every ECG should be interpreted, when possible, in the setting of the patient’s presentation.

 

 

 

Ask the Expert

Thu, 10/27/2016 - 15:33 -- Dawn

Question:

 

Dr. Jones,

I am confused about the repolarization abnormalities that occur in conditions other than acute M.I. (Bundle branch block and hypertrophy, for example). I have been taught that the repolarization abnormalities should point opposite the MAIN part of the QRS, but also I have been told that they should point opposite the TERMINAL deflection of the QRS.  Which is right?

 

Today’s expert is Dr. Jerry W. Jones, MD, FACEP, FAAEM

Jerry W. Jones, MD FACEP FAAEM is a diplomate of the American Board of Emergency Medicine who has practiced internal medicine and emergency medicine for 35 years. Dr. Jones has been on the teaching faculties of the University of Oklahoma and The University of Texas Medical Branch in Galveston. He is a published author who has also been featured in the New York Times and the Annals of Emergency Medicine for his work in the developing field of telemedicine. He is also a Fellow of the American College of Emergency Physicians and a Fellow of the American Academy of Emergency Medicine and, in addition, a member of the European Society of Emergency Medicine. Dr. Jones is the CEO of Medicus of Houston and the principal instructor for the Advanced ECG Interpretation Boot Camp and the Advanced Dysrhythmia Boot Camp. 

 

Answer:

 

 

Which Direction Should the Repolarization Abnormality Point?

OK. You've got an abnormal QRS complex followed by a repolarization abnormality (RA). Which direction should the repolarization abnormality point? As a young resident, I was taught that the RA should point in the direction opposite the terminal deflection of the QRS complex. But years later, I see other physicians stating that the repolarization abnormality should point opposite the main deflection of the QRS complex. Which is correct?

The answer is both are correct. Why? How?

The reason is that the repolarization abnormality is connected to the ventricle in which the problem is located - not the QRS complex itself. To better understand this, let's look at some of the major causes of repolarization abnormalities (you can find examples in the illustration at the top of this page):

Right Bundle Branch Block (RBBB) - When you look at the QRS complex in V1, you see an R and an R'. The R represents left ventricular activation while the R' represents right ventricular activation. So, the problem lies in the right ventricle represented by the R'. The repolarization abnormality reflects the problem in the RV so it should be opposite the R' which is always the last deflection in V1 in the presence of RBBB. Therefore, in cases of RBBB, the repolarization abnormality is always opposite the terminal deflection of the QRS.

Left Bundle Branch Block (LBBB) - When you look at the QRS complex from V6 which has a LBBB, we see a relatively tall, upright monophasic QRS complex. Part of that QRS represents right ventricular depolarization and part represents left ventricular depolarization. But how much of which? We don't know, but all we need to know is that this is a monophasic complex and it is upright. Therefore, since the repolarization abnormality reflects the problem in the left ventricle, and the LV is represented somewhere in that monophasic R, the repolarization abnormality should be opposite the main deflection. Therefore, in cases of LBBB, the repolarization abnormality is always opposite the main deflection of the QRS.

Left Ventricular Hypertrophy (LVH) - When you look at the QRS complexes from V5 and V6, we see a relatively tall, upright monophasic QRS complex. Part of that QRS represents right ventricular depolarization and part represents left ventricular depolarization. But how much of which? Again, we don't know, but all we need to know is that this is a monophasic complex and it is upright. Therefore, since the repolarization abnormality reflects the problem in the left ventricle, and the LV is represented somewhere in that monophasic R, the repolarization abnormality should be opposite the main deflection. Therefore, in cases of LVH, the repolarization abnormality is always opposite the main deflection of the QRS.

Right Ventricular Hypertrophy (RVH) - The same concept discussed regarding LVH applies in cases of RVH. Therefore, in cases of RVH, the repolarization abnormality is always opposite the main deflection of the QRS.

Ventricular Pre-excitation - Most people reading ECGs don't realize that ventricular pre-excitation can also produce a repolarization abnormality. Just as repolarization abnormalities are not always present in cases of LVH and RVH, they are not always present in cases of ventricular pre-excitation, either. However, the repolarization abnormality IS present in some cases. The RA is connected to the ventricle containing the accessory pathway, but don't worry: you don't have to determine which ventricle that is. If a repolarization abnormality is present in a lead, it should be negative if the delta wave is positive and vice versa. Therefore, the repolarization abnormality points opposite to the direction of the delta wave.

 

So, the question really isn't whether the repolarization abnormality should be opposite the terminal or the main deflection of the QRS. It should be opposite the deflection that represents the involved ventricle.

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

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