SECTION 4 Self-Test

Test ECG-1

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-2

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-3

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-4

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-5

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-6

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-7

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-8

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-9

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-10

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-11

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-12

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-13

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-14

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-15

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-16

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-17

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-18

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-19

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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Test ECG-20

A rhythm strip.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

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SECTION 4 Self-Test Answers

Test ECG-1

A rhythm strip from lead 2 shows a sharp peak of the QRS complex and a curved peak of the T wave. The complexes occur at high frequency and low amplitude.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 115 BPM

PR intervals: Not applicable

Regularity: Regular

QRS width: Normal

P waves: None

Morphology: None

Axis: None

Grouping: None

Dropped beats: None

P:QRS ratio: Not applicable

Rhythm: Junctional tachycardia

Discussion:

Test ECG-1 shows a rapid narrow-complex tachycardia at a rate of 115 BPM. There are no P waves noted on the strip. An argument can be made for the presence of pseudo-S waves, and this possibility can be verified or rejected by looking at the morphology of the lead II complexes in an old ECG or once the patient is back in sinus rhythm. The QT interval is prolonged on this strip, and a full 12-lead ECG should be considered to evaluate this issue further. The regular cadence, the lack of P waves, the narrow complexes, and the rate of 115 BPM all point to the diagnosis of a junctional tachycardia.

Test ECG-2

A rhythm strip from lead 2 illustrates sinus arrythmia.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Description

Rate: About 50 BPM

PR intervals: Normal

Regularity: Regularly irregular

QRS width: Normal

P waves: Present

Morphology: Upright

Axis: Normal

Grouping: None

Dropped beats: None

P:QRS ratio: 1:1

Rhythm: Sinus arrhythmia

Discussion:

Test ECG-2 shows an irregular rhythm with a gradual decrease in the R-R intervals. There are P waves in front of each QRS complex with nearly identical morphology. The last P wave has a different appearance on this strip but the PR interval is the same. The difference is probably due to the slight bump in the baseline. A longer strip taken on this patient verified the presence of the rhythmical slowing and speeding up, which is classic for a sinus arrhythmia.

Test ECG-3

A rhythm strip from lead 2 shows a sharp peak of the QRS complex, a small dip of the pseudo S wave, and a broad and curved peak of the T wave. The complexes occur at high frequency.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: Atrial: 135 BPM

PR intervals: Not applicable

Regularity: Regular

QRS width: Normal

P waves: Present, pseudo-S

Morphology: Inverted

Axis: Abnormal

Grouping: None

Dropped beats: None

P:QRS ratio: 1:1

Rhythm: AVNRT

Discussion:

Test ECG-3 shows a rapid, regular, narrow-complex tachycardia. There are no P waves before the QRS complexes, but there are obvious pseudo-S waves visible at the end of the QRS complexes. As mentioned, these pseudo-S waves (blue arrow) represent the retrogradely conducted, inverted P waves that are formed due to the microreentry circuit of AVNRT. There is some variation in the amplitude of the complexes due to the electrical alternans pattern, which is typically seen in very fast tachycardias.

Test ECG-4

A rhythm strip from lead 2 shows a sharp peak of the QRS complex and a wide, small, and curved peak of the T wave.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 50 BPM

PR intervals: None

Regularity: Regular

QRS width: Normal

P waves: None

Morphology: None

Axis: None

Grouping: None

Dropped beats: None

P:QRS ratio: None

Rhythm: Junctional rhythm

Discussion:

Test ECG-4 shows a slow ventricular rhythm with no associated P waves. The narrow complexes are consistent with a supraventricular origin and conduction through the normal electrical conduction system. These findings and the rate of approximately 50 BPM are all consistent with a junctional rhythm. If you want to be more specific, the diagnosis is a junctional escape rhythm.

Test ECG-5

A rhythm strip from lead 2 shows a sharp dip of the QRS complex, a depressed and rising ST segment, and a short and curved peak of the T wave. The complexes occur at high frequency with very short QRS interval.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 215 BPM

PR intervals: None

Regularity: Regular

QRS width: Normal

P waves: None

Morphology: None

Axis: None

Grouping: None

Dropped beats: None

P:QRS ratio: None

Rhythm: AVRT (orthodromic)

Discussion:

Test ECG-5 shows a very fast narrow-complex tachycardia. There appears to be some pretty significant ST depression (blue arrow), which is probably due to the tachycardia, but could be the result of an underlying relative or actual ischemia. A case could be made for a very fast AVNRT or an AVRT. The rapid rates favor the presence of an accessory pathway. On clinical correlation, the patient did have a history of Wolff-Parkinson-White (WPW) syndrome and an accessory pathway. The 12-lead ECG after the patient was converted did show the presence of a delta wave, which is typically found in WPW syndrome. If you remember, there are two kinds of conduction in AVRT: orthodromic and antidromic. This is an example of orthodromic AVRT because of the narrow complexes associated with the tachycardia.

Test ECG-6

A rhythm strip from lead 2 shows a sharp peak of the R wave, a small dip of the S wave, a concavely curved ST segment, and a curved peak of the T wave.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 190 BPM

PR intervals: None

Regularity: Regular

QRS width: Normal

P waves: None

Morphology: None

Axis: None

Grouping: None

Dropped beats: None

P:QRS ratio: None

Rhythm: AVNRT

Discussion:

Test ECG-6 is an example of a rapid AVNRT. It shows a narrow-complex supraventricular tachycardia with associated ST depression. What makes this an example of AVNRT and Test ECG-5 an example of AVRT? The clinical scenario and the appearance of the 12-lead ECG after the rhythm is broken. Morphologically, it would be difficult to tell from the strips, and both strips could be either AVNRT or AVRT on surface examination. In Test ECG-5, the fact that the rate is over 200 BPM is the only thing that would favor AVRT, but that could also occasionally be seen in AVNRT. The reason we bring this up is that you need to have a high index of suspicion when approaching these rapid tachycardias and use all the tools you have available to effectively make your diagnosis.

Test ECG-7

A rhythm strip from lead 2 shows a fluctuating dip of the P wave, pointed by an arrow, and a sharp peak of the QRS complex.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 210 BPM

PR intervals: None

Regularity: Regular

QRS width: Normal

P waves: Present

Morphology: Inverted

Axis: Abnormal

Grouping: None

Dropped beats: None

P:QRS ratio: 1:1

Rhythm: AVRT (orthodromic)

Discussion:

Test ECG-7 is another tough diagnostic case, which could represent either AVNRT or AVRT. There is one finding, however, that helps make your decision a little easier. T waves can either be inverted, upright, or biphasic. However, they are typically smooth, gradually changing waves. Sharp changes along their lines are not typically seen in T-wave morphologies. On our strip, there appears to be a fairly sharp negative deflection on the downward slope of the T wave (blue arrow). These sharp, negative waves are actually inverted P waves associated with prolonged RP intervals. Long RP intervals are consistent with AVRT. Hence, this is an orthodromic AVRT. Clinical correlation and a 12-lead ECG verified the diagnosis.

Test ECG-8

A rhythm strip from lead 2 shows an inverted P wave, a sharp and narrow peak of the QRS wave, and a small dip of the T wave between fluctuating baseline, marked by asterisks.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 64 BPM

PR intervals: Normal

Regularity: See discussion below

QRS width: Wide

P waves: Present

Morphology: Inverted

Axis: Abnormal

Grouping: None

Dropped beats: None

P:QRS ratio: 1:1

Rhythm: Ectopic atrial rhythm

Discussion:

Test ECG-8 presents some interesting dilemmas. First of all, the rhythm is slightly irregular. Could the irregularity be caused by premature complexes? Not really, because all of the P waves are exactly identical and the PR intervals remain the same. Could this be a straight sinus arrhythmia? No, because the P waves are inverted, meaning that they originate in either an ectopic atrial or a junctional site. The normal PR intervals favor an ectopic rhythm. This is an ectopic atrial rhythm with some irregularity, probably due to a respiratory variation of a sinus arrhythmia. Secondly, there are some slight abnormalities noted along the baseline due to artifact (blue asterisks). Lastly, the blue arrow points to an S wave at the end of the QRS complex (verified by a 12-lead ECG), which could easily be mistaken for a blocked inverted P wave.

Test ECG-9

A rhythm strip from lead 2 shows a wide and sharp dip of the QRS complex, a small dip in the ST segment, and a short and sharp peak of the T wave.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 260 BPM

PR intervals: None

Regularity: Regular

QRS width: Wide

P waves: None

Morphology: None

Axis: None

Grouping: None

Dropped beats: None

P:QRS ratio: None

Rhythm: AVRT (antidromic)

Discussion:

Test ECG-9 shows a very dangerous rhythm. The rate of 260 BPM and the wide complexes noted on the tachycardia are consistent with an antidromic AVRT. Antidromic AVRTs are associated with accessory pathways and WPW syndrome. The conduction of the macroreentry electrical circuit is through the accessory pathway into the ventricles, and then retrogradely against the AV node to return to the atria. In this type of AVRT, there is no AV nodal control over the rate, hence the danger. These very rapid rhythms can become so fast as to break down completely, sending the patient into ventricular fibrillation and cardiac arrest. Prompt, focused treatment is indicated in these patients and electrical cardioversion should be emergently performed for any hemodynamic instability.

Test ECG-10

A rhythm strip from lead 2 shows a small and curved peak of the P wave, labeled with a dot, a tall and narrow peak of the QRS complex, and a small and curved peak of the T wave.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 110 BPM

PR intervals: Normal

Regularity: Regular

QRS width: Normal

P waves: Present

Morphology: Upright

Axis: Normal

Grouping: None

Dropped beats: None

P:QRS ratio: 1:1

Rhythm: Sinus tachycardia

Discussion:

Test ECG-10 shows a sinus rhythm with an upright P wave, a normal PR interval, and some slight ST depression. Since the rate is 110 BPM, this makes the rhythm a sinus tachycardia. The PR interval appears short, but measurement with your calipers should show you that it is 0.12 seconds and within the normal range. The QT interval appears prolonged at 0.31 seconds but, when you consider that the ventricular rate is 110 BPM, it is within the normal range. The T wave in this lead is a small, positive deflection, which could be mistaken for another P wave (blue arrow).

Test ECG-11

A rhythm strip from lead 2 shows a tall peak of the QRS complex, an inverted P wave as pseudo S wave, pointed by an arrow, and a wide and curved peak of the T wave.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 125 BPM

PR intervals: Not applicable

Regularity: Regular

QRS width: Normal

P waves: Present, pseudo-S

Morphology: Inverted

Axis: Abnormal

Grouping: None

Dropped beats: None

P:QRS ratio: 1:1

Rhythm: Junctional tachycardia

Discussion:

Test ECG-11 shows a narrow-complex tachycardia at about 125 BPM. There are inverted P waves present, which cause a pseudo-S wave pattern in lead II (blue arrow). If the rate were over 140 BPM, the diagnosis would be consistent with AVNRT. However, since it is 125 BPM, the diagnosis is junctional tach.

Test ECG-12

A rhythm strip from lead 2 shows a small, narrow, and sharp peak of the QRS complex and a wide and curved peak of the T wave.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 45 BPM

PR intervals: None

Regularity: Regular

QRS width: Normal

P waves: None

Morphology: None

Axis: None

Grouping: None

Dropped beats: None

P:QRS ratio: None

Rhythm: Junctional rhythm

Discussion:

Test ECG-12 shows a slow rhythm with no associated P waves noted anywhere along the strip. The S waves at the end of the QRS complexes could represent pseudo-s waves, but you would need other leads or a 12-lead ECG to confirm. The QRS complexes are narrow. This strip is consistent with a junctional (escape) rhythm.

Test ECG-13

A rhythm strip from lead 2 shows a small and sharp peak of the QRS complex, a sharp dip of the P wave as pseudo S wave, and a wide and curved peak of the T wave. The baseline falls.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 145 BPM

PR intervals: None

Regularity: Regular

QRS width: Normal

P waves: Present, pseudo-S

Morphology: Inverted

Axis: Abnormal

Grouping: None

Dropped beats: None

P:QRS ratio: None

Rhythm: AVNRT

Discussion:

Test ECG-13 and Test ECG-14 are both from the same patient, but in different leads. Test ECG-13 shows lead II and Test ECG-14 shows lead V1. The reason we put these next to each other is to reinforce the need to look for the pseudo-S wave in lead II (blue arrow) and pseudo-R’ waves in lead V1 of any patient in AVNRT. Multiple leads or a full 12-lead ECG are invaluable tools in verifying these two findings, which clinch the diagnosis of AVNRT as the cause of a narrow-complex tachycardia.

Test ECG-14

A rhythm strip from lead V1 shows a sharp dip of the QRS complex and an indiscernible and curved peak of the P wave as pseudo R prime wave.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 145 BPM

PR intervals: None

Regularity: Regular

QRS width: Normal

P waves: Present, pseudo-R’

Morphology: Upright

Axis: Unclear

Grouping: None

Dropped beats: None

P:QRS ratio: None

Rhythm: AVNRT

Discussion:

Test ECG-14 shows a lead V1 rhythm strip of the same patient as in Test ECG-13. Both of these strips show AVNRT. Note the presence of the pseudo-R’ wave on this strip (blue arrow). Make it a habit to always check the lead that you are using to view a strip. The orientation and the appearance of the complexes will change drastically, depending on the lead that is being viewed.

Test ECG-15

A rhythm strip from lead 2 shows a sharp dip of the QRS complex and a curved and wide peak of the T wave.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 120 BPM

PR intervals: None

Regularity: Regular

QRS width: Normal

P waves: None

Morphology: None

Axis: None

Grouping: None

Dropped beats: None

P:QRS ratio: None

Rhythm: Junctional tachycardia

Discussion:

Test ECG-15 shows a rapid, regular narrow-complex tachycardia. The heart rate is 120 BPM and there are no visible P waves on the strip. These findings are consistent with a junctional tachycardia.

Test ECG-16

A rhythm strip from lead 2 shows a curved peak of the P wave, a sharp peak of the R wave, a sharp dip of the S wave, and a curved peak of the T wave. The complexes occur at long intervals. However, the third complex occurs immediately after the second.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 34 BPM

PR intervals: Normal, except in event

Regularity: Regularly irregular

QRS width: Normal

P waves: Present

Morphology: Upright

Axis: Normal

Grouping: None

Dropped beats: None

P:QRS ratio: 1:1

Rhythm: Sinus bradycardia with a PAC

Discussion:

Test ECG-16 was taken from a patient with a very slow sinus bradycardia. The third complex arrives prematurely and has a different morphology and PR interval than the others on the strip. By definition, this makes the third complex a PAC. The PAC is probably a protective event by the heart, as it is trying to compensate for the severity of the underlying bradycardia. The patient has very significant ST depressions in lead II. The ST changes could be due to direct inferior wall ischemia or could represent reciprocal changes of an acute lateral wall MI. A full 12-lead ECG would be invaluable on this patient. Clinical correlation and evaluation for an AMI should also be emergently undertaken. Temporary pacemaker placement may be indicated if this patient is hemodynamically unstable.

Test ECG-17

A rhythm strip from lead 2 shows a wide and indiscernible peak of the P wave, a small and narrow peak of the QRS complex, and a wide and curved peak of the T wave.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 55 BPM

PR intervals: Prolonged

Regularity: Regular

QRS width: Normal

P waves: Present

Morphology: Upright

Axis: Normal

Grouping: None

Dropped beats: None

P:QRS ratio: 1:1

Rhythm: Sinus bradycardia with a PAC, first-degree AV block

Discussion:

Test ECG-17 shows a rhythm with a P wave before each QRS complex with a prolonged PR interval of 0.21 sec at a rate of 55 BPM. This is consistent with a sinus bradycardia with first-degree AV block. The last complex represents an event that occurs prematurely with a different P-wave morphology and PR interval, making this a PAC.

Test ECG-18

A rhythm strip from lead V1 illustrates focal atrial tachycardia with 2 to 1 conduction.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Description

Rate: Atrial: 260 BPM;
Ventricular: 130 BPM

PR intervals: See discussion below

Regularity: Regular

QRS width: Normal

P waves: Present

Morphology: See discussion below

Axis: See discussion below

Grouping: None

Dropped beats: None

P:QRS ratio: See discussion below

Rhythm: Focal atrial tachycardia with 2:1 conduction

Discussion:

Test ECG-18 can be quite troubling. We can all clearly see the first P wave right before the QRS complexes. However, many people miss the other P wave buried in the T wave right after the QRS complex (see pink arrows), thinking that this second peak is the T wave. It isn’t. Here is the proof: Use your calipers to measure the distance between the peaks that are obviously P waves. Next, divide that distance in half. Now, place your calipers over the obvious P wave and you will see that the other pin falls directly on top of the second peak—the buried P wave.

This extra P wave makes this rhythm either a focal atrial tachycardia with block (2:1 conduction) or an atrial flutter with 2:1 conduction. What is the deciding factor? The space between the P waves. If there is a constantly undulating saw-tooth pattern, then the rhythm is atrial flutter. If there is a return to an isoelectric baseline between the P waves, then it is an atrial tachycardia with block. A 12-lead ECG on this patient, including lead II, verified the diagnosis of focal atrial tachycardia with block.

Test ECG-19

A rhythm strip from lead 2 shows a small and curved peak of the P wave, a sharp peak of the QRS complex, and a wide and curved peak of the T wave. The consecutive R-R interval periods in seconds are 1.44, 1.27, 1.15, 1.29, and 1.42.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: About 45 BPM

PR intervals: Normal

Regularity: Regularly irregular

QRS width: Normal

P waves: Present

Morphology: Upright

Axis: Normal

Grouping: None

Dropped beats: None

P:QRS ratio: 1:1

Rhythm: Sinus arrhythmia

Discussion:

Test ECG-19 shows a regularly irregular rhythm with narrow QRS complexes. Each QRS complex has its own P wave, and both the P-wave morphology and the PR intervals throughout the strip are identical. The rhythm strip has a regularly irregular pattern due to a gradual narrowing and widening of the P-P intervals. The difference between the widest and the narrowest P-P interval is greater than 0.16 seconds, clinching the diagnosis of a sinus arrhythmia. Normally, sinus arrhythmia occurs at rates between 60 and 100 BPM, but exceptions do exist. Many times, the slower rates in these patients are due to the presence of drugs like the beta-blocking agents.

Test ECG-20

A rhythm strip from lead 2 shows a sharp peak of the R wave, a wide and curved dip of the S wave, and a small and curved peak of the T wave.

From Arrhythmia Recognition: The Art of Interpretation, courtesy of Tomas B. Garcia, MD.

Rate: Atrial: 200 BPM

PR intervals: None

Regularity: Regular

QRS width: Wide

P waves: None

Morphology: None

Axis: None

Grouping: None

Dropped beats: None

P:QRS ratio: None

Rhythm: AVRT (antidromic)

Discussion:

Test ECG-20 shows a wide-complex tachycardia at 200 BPM. There are no obvious P waves noted throughout the strip. These findings are consistent with an antidromic AVRT. The presence of an accessory pathway should be evaluated further.

As a side note, could this strip represent an AVNRT in someone with a preexisting bundle branch block? The answer is yes. Always remember to obtain clinical correlation and to obtain multiple leads or a full 12-lead ECG to help in your decision making. An old ECG or rhythm strip will also prove invaluable in evaluating any complex rhythm. Finally, for completeness, just as in every wide-complex tachycardia, you need to think of and rule out the possibility of a ventricular tachycardia.