Arrhythmia Recognition: The Art of Interpretation

A rhythm strip from lead 2 shows a curved, fluctuating, short peak wave and a sharp peak of the QRS complex, that falls with mild fluctuations and rises to a curved peak of the T wave midway. — From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: 50 to 60 BPM	PR intervals: Normal, consistent
Regularity: Regularly irregular	QRS width: Normal
P waves: Present Morphology: Normal Axis: Normal	Grouping: None
P waves: Present Morphology: Normal Axis: Normal	Dropped beats: None
P:QRS ratio: 1:1	Rhythm: Sinus arrhythmia

Discussion:

ECG 11-1 is classic for the respiratory variant form of sinus arrhythmia. Note the rhythmical speeding up and slowing of the rate throughout the strip (to fully appreciate the respiratory variation completely, a longer strip would be necessary). Note the slight irregularities in the appearance of the P waves throughout the strip. This is commonly seen in sinus arrhythmia, and can sometimes be confused with other rhythm abnormalities.

ECG 11-2

A rhythm strip from lead 2 shows a tall, sharp peak of the QRS complex between two curved peaks of the narrow P wave and the wide T wave. — From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: Around 60 BPM	PR intervals: Normal, consistent
Regularity: Regularly irregular	QRS width: Normal
P waves: Present Morphology: Normal Axis: Normal	Grouping: None
P waves: Present Morphology: Normal Axis: Normal	Dropped beats: None
P:QRS ratio: 1:1	Rhythm: Sinus arrhythmia

Discussion:

Once again, ECG 11-2 is classic for the respiratory variant form of sinus arrhythmia. In this case, the gradual slowing and speeding up of the heart rate is very obvious at first glance. Notice that we are stating that this rhythm strip is regularly irregular. The reason is that the rhythmical changes in heart rate are continuously recurring and predictable. Hence, the rate changes are regular and very much associated with the normal breathing cycles.

ECG 11-3

A rhythm strip from lead 2 shows a curved and imperceptible peak of the P wave, a sharp dip of the QRS complex, and a tall, curved peak of the T wave. An arrow points at fluctuations between the complexes. — From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: Around 65 BPM	PR intervals: Normal, consistent
Regularity: Regularly irregular	QRS width: Normal
P waves: Present Morphology: Normal Axis: Normal	Grouping: None
P waves: Present Morphology: Normal Axis: Normal	Dropped beats: None
P:QRS ratio: 1:1	Rhythm: Sinus arrhythmia

Discussion:

By this time, you should easily be able to identify ECG 11-3 as a respiratory variant sinus arrhythmia. There are some other interesting things to be concerned about on this strip, however. For example, the ST segments are very elevated and very flat. This could possibly represent an inferior wall myocardial infarction (MI). If you ever see a strip like this one, make sure that you get a full 12-lead ECG to evaluate the possibility of injury or infarction. Remember, using a strip to make a diagnosis about anything but the rhythm is dangerous. Always obtain a full ECG!

Another interesting point to make about this ECG is the small wave right under the green arrow. There are a few more similar waves after some of the other complexes. What are they? Are they another P wave that is not conducted? The answer is no. Those are U waves, which can occur normally in some patients. Ischemia also causes them to occur and is probably the cause in this patient. Notice that you can only see them between the complexes that are fairly far apart. They are still there on the other complexes but are not visible because they are buried in the P wave of the subsequent complex.

ECG 11-4

A rhythm strip from lead 2 shows a tall, sharp peak of the QRS complex between two curved peaks of the narrow P wave and the wide T wave. Their rate increases and then decreases. — From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: Around 55 BPM	PR intervals: Normal, consistent
Regularity: Regularly irregular	QRS width: Normal
P waves: Present Morphology: Normal Axis: Normal	Grouping: None
P waves: Present Morphology: Normal Axis: Normal	Dropped beats: None
P:QRS ratio: 1:1	Rhythm: Sinus arrhythmia

Discussion:

ECG 11-4 also shows the rhythmical and gradual slowing and speeding up of a respiratory variant sinus arrhythmia. Notice the longer pause that is present near the middle of the strip. It is common in sinus arrhythmia to have longer pauses than usual. This is all part of the rhythm and is not an indication for a pacemaker unless the patient is symptomatic or if the pauses are too long. How long is too long? That is a clinical decision you will have to make based on your patient and his or her presentation.

This strip shows some slight depressions on the ST segments, and the depressions are flat. Flat ST changes, either elevations or depressions, can be ischemic. Once again, it would be a good idea to obtain an ECG to evaluate the problem further.

ECG 11-5

A rhythm strip from lead 2 shows a small, curved peak of the P wave, a tall, sharp peak of the R wave, and a sharp dip of the S wave, which rises to a plateau of the T wave with fluctuations. — From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: Around 60 BPM	PR intervals: Normal, consistent
Regularity: Regularly irregular	QRS width: Normal
P waves: Present Morphology: Normal Axis: Normal	Grouping: None
P waves: Present Morphology: Normal Axis: Normal	Dropped beats: None
P:QRS ratio: 1:1	Rhythm: Sinus arrhythmia

Discussion:

ECG 11-5 is a little tougher to spot by just a quick eyeballing of the rhythm. Here is one place where calipers would come in very handy to spot the gradual slowing and speeding up of the heart rate. This is, however, respiratory variant sinus arrhythmia.

These ST segments are cause for concern. They are depressed, flat, and just plain ugly. A full 12-lead ECG would really be helpful in evaluating this patient further. Be very careful with this patient, who could be having a large MI.

ECG 11-6

A rhythm strip from lead 2 shows a sharp peak of the QRS complex between imperceptible and curved peak of the P wave and dip of the T wave. The peaks occur at irregular intervals. — From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: Around 50 BPM	PR intervals: Normal, consistent
Regularity: Regularly irregular	QRS width: Normal
P waves: Present Morphology: Normal Axis: Normal	Grouping: None
P waves: Present Morphology: Normal Axis: Normal	Dropped beats: None
P:QRS ratio: 1:1	Rhythm: Sinus arrhythmia

Discussion:

ECG 11-6 is a really tough rhythm to figure out! Let’s approach it logically, and you’ll see that you can do it. It is definitely slow. If you take the number of beats in a 12-second strip and multiply it by 5, you get about 50 BPM. The rhythm is regularly irregular because, if you use your calipers, you have many P-P intervals that are the same throughout the strip (see Figure 11-7).

A rhythm strip shows complexes with the P-P interval labeled. — Figure 11-7 P-P intervals are marked by the blue stars.

© Jones & Bartlett Learning.
Description

Next, look at the P waves. Are they all the same? Yes, they are all the same. This removes multiple PACs as an option. What about the PR intervals? They are all the same. That means that all of the complexes originated in the same pacemaker. The P waves are upright in lead II, so it is less likely that the pacemaker is ectopic.

The irregularity, the same P waves, a normal P wave axis, and the same PR intervals all point to the only possibility: nonrespiratory sinus arrhythmia.