This ECG is taken from an elderly man with heart failure. 

The ECG   The first feature that might capture your attention is the wider-than-normal QRS complex, which is 160 ms (.16 seconds).  The rate is 58 bpm. We do not know the patient’s medications or baseline rate.  There are P waves present, and so the rhythm is SINUS BRADYCARDIA. The P waves are broad , > 110 ms in Lead II (red lines in close up) and bifid, with greater than 40 ms between the two peaks in Lead II (blue lines).  In V1, the P waves are biphasic, with the terminal negative portion greater than 40 ms duration (red lines). This meets the ECG criteria for LEFT ATRIAL ENLARGEMENT, or preferably, LEFT ATRIAL ABNORMALITY. (https://LITFL.com/left-atrial-enlargement-ecg-library/) ECG criteria are not highly accurate for detecting atrial enlargement, and abnormal findings should be confirmed by anatomic measurement. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2244611/).

The QRS complexes, as mentioned, are wide. Because there is sinus rhythm, we know the delay in conduction is due to interventricular conduction delay, and not to ventricular rhythm.  This ECG meets the criteria for LEFT BUNDLE BRANCH BLOCK. 

·        Supraventricular rhythm 

·        Wide QRS (>.12 seconds)

Today’s ECG is from a 75 year old man who has been experiencing syncope. 

Examination of the ECG shows a sinus bradycardia at just under 40 bpm.  There is a first-degree AV block, with a PR interval of about .28 seconds (280 ms).  There is a right bundle branch block.  The ECG criteria for right bundle branch block are:  supraventricular rhythm, wide QRS (120 ms in this case), rSR’ pattern in V1, and  a small, wide S wave in Leads I and V6.  There is actually a “terminal delay”, or extra wave at the end of each QRS complex, reflecting late repolarization of the right ventricle. 

This ECG also shows a left anterior fascicular block, also called left anterior hemiblock.  The left bundle branch usually has two main branches, the anterior-superior and the posterior-inferior.  ECG criteria for left anterior fascicular block are: left axis deviation with a small r wave in Lead III and a small q waves with tall R waves in Leads I and aVL.  There is also a prolonged R wave peak time (> 45 ms) in aVL. There is usually a slightly prolonged QRS, but in this case, there is widening of the QRS due to the RBBB.   Because the right bundle branch is blocked, and one fascicle of the left bundle is blocked, the patient is said to have a “bifascicular block”.  Only one fascicle remains available for conduction from the atria to the ventricles.

We have no information about what caused the conduction block in these two fascicles, but should the third fascicle fail, the patient will be in a complete AV block.  An AV block at the level of the bundle branches will result in an idioventricular escape rhythm – wide QRS complexes with very slow rates – which is a low-output rhythm.  

This patient has also had syncope, which was determined to be related to his bradycardia.  He had an AV sequential pacemaker implanted and did well.

This ECG is from a 46-year-old woman with diabetes mellitus.  She presented to the Emergency Dept. with a complaint of weakness.  Her BP was elevated at 186/102.  Her blood glucose was 936 mg/dL (normal 70-105). 

So, what does her ECG show?

1) Sinus bradycardia at 55 bpm.  The rhythm is regular, with no extrasystoles.

2) A slightly prolonged PR interval at 218 ms (.218 seconds). Normal is 120-200 ms. 

3) A “wide side of normal” QRS duration at 109 ms. Normal is 70-100, but can be a little longer in normal individuals.

4) A prolonged QTc interval at 520 ms.  Normal QTc is 460 ms or less in women. A helpful rule of thumb is that the QT should be less than half the preceding RR. 

5) Normal P waves.

6) Normal axes of P, QRS, and T waves.

7) A large Q wave in Lead III which is not repeated in aVL.  This can be inconsequential when confined to Lead III, or can be a pathological Q wave, especially if also seen in aVF. 

8) Flat ST segments.  Normal ST segments are convex upward, like a smile.

9) Tall, peaked T waves in precordial leads V₂ through V₆, and in Lead II. 

What does it mean?

Unfortunately, we do not have complete labs for this patient, or any information about her outcome.

We know that patients who have uncontrolled diabetes are at risk for renal failure, so we should consider electrolyte imbalances when we see abnormalities in the ECG. 

This strip shows an underlying sinus bradycardia with a rate less than 40/min.  There is one "premature" beat, which can be considered to be ectopic, because it interrupts an otherwise regular rhythm.  The interesting thing is that the premature beat is not terribly early - it is about 740 ms from the previous beat.  If all the beats were spaced like this, the heart rate would be about 84/min.  There is probably an element of "escape" here, in that the ectopic beat is able to express itself due to the slow rate.  A faster sinus rate would override this ectopic focus.  So, we could view this early beat as a help, rather than a problem.  The most important consideration here is to address the cause of the bradycardia, and treat appropriately.