ECG Blog #373 — 86yo and this Rhythm ...

The 12-lead ECG and long lead II rhythm strip in Figure-1 was obtained from an 86-year old man — who presented to the ED (Emergency Department) with presyncope. No chest pain. The patient was hemodynamically stable in association with this rhythm.

• How would YOU interpret the ECG in Figure-1?
• What is the rhythm?

Figure-1: The initial ECG in today's case — obtained from an 86-year old man with presyncope, but no chest pain. (To improve visualization — I've digitized the original ECG using PMcardio).

MY Thoughts on the ECG in Figure-1:

The overall rate of the rhythm in Figure-1 is not fast. Knowing that this patient is hemodynamically stable provides us with some time to carefully consider the etiology of the rhythm before turning our attention to findings on the 12-lead ECG.

• PEARL #1: When your patient is stable in a rhythm that is not overly fast — I favor starting with assessment of the long lead rhythm strip before going into detail about findings on the 12-lead ECG. As will soon become apparent — the reason for this is that knowing which beats are ventricular vs supraventricular will be critical for assessing the likelihood of acute ST-T wave changes.

The Long Lead II Rhythm Strip:

As always — I favor a systematic approach to rhythm interpretation, using the Ps, Qs, 3R memory aid (See ECG Blog #185).

• Regarding QRS width — there are 2 different QRS shapes in the long lead II rhythm strip in Figure-1: i) Beats #1,2,3,4; and beats #8,9,10 are wide; and, ii) The remaining QRS complexes are narrower.
• P waves are present in today’s tracing! In Figure-2 — I’ve highlighted with RED arrows those P waves that I can be certain about. 
• Note that each of the 4 RED arrows in Figure-2 — appear with a constant (and normal) PR interval before narrow-QRS complex beats that manifest a similar morphology. This tells us that there is an underlying sinus rhythm in today's tracing, here with a heart rate of ~70/minute (ie, the R-R interval between beats #5-6; 6-7; and between beats #11-12; and #12-13 — is just over 4 large boxes in duration, which corresponds to a rate of ~70/minute).

Are there Additional P Waves?

• The easiest way to find out if there are additional P waves in Figure-2 — is to use calipers. Setting your calipers to the P-P interval defined by 2 consecutive P waves about which I am certain (ie, I set my calipers to the P-P interval between beats #6-7) — it can be seen that the “next walk” of the calipers using this P-P interval will fall right on the PINK arrow in Figure-2.
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• PEARL #2: Identifying additional atrial activity is the KEY to interpreting today’s rhythm. Note that the very small initial triangular deflection under the PINK arrow in Figure-2 — is wider than the small initial r wave in front of all other beats in this tracing. This confirms that after the first 2 RED arrows in Figure-2 — the next on-time sinus P wave lies directly under the PINK arrow.
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• PEARL #3: The fact that the PR interval that begins from the PINK arrow (and extends until the QRS of beat #8) is too short to conduct — indicates that at least for this beat, there is AV dissociation (because this PINK arrow P wave is not Related to its neighboring QRS). This very short PR interval means that "something else" must have occurred before the PINK P wave has a chance to conduct — which confirms that the wide and different-looking beat #8 must be a ventricular beat!

PEARL #4: Is Beat #8 a PVC or an “Escape” Beat?

It is important to clarify distinction between a "PVC" vs an "escape" beat. By definition — a PVC is “Premature" (ie, occurs earlier-than-expected). In contrast — an "escape" beat occurs later in the cycle. 

• Instead of occurring “early” — beat #8 in Figure-2 occurs relatively late in the cycle. As a result — beat #8 is best classified as a ventricular "escape" beat.
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• Since beats #1-thru-4; and #9,10 all look the same in QRS morphology as beat #8 — these are all ventricular beats. And since each of these ventricular beats is separated by a similar R-R interval (that is ~4 large boxes in duration) — these beats constitute 2 short runs of AIVR (Accelerated IdioVentricular Rhythm) at a rate of ~75/minute.
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• NOTE: As discussed in detail in ECG Blog #108 — "AIVR" is an "enhanced" ventricular ectopic rhythm that occurs faster than the intrinsic ventricular escape rate (which is typically between 20-40/minute) — but slower than hemodynamically significant Ventricular Tachycardia (ie, VT at rates >130-140/minute).

Putting It All Together:

To emphasize — It should take you no more than seconds to complete the above rhythm analysis steps. These steps strongly suggest the following regarding the rhythm in Figure-2:

• That there is an underlying sinus rhythm at ~70/minute.
• This underlying sinus rhythm is interrupted by short runs of AIVR that occur at a slightly faster rate (ie, of ~75/minute).

Figure-2: I've highlighted with RED arrows the 4 P waves in today's rhythm that I can be certain about.

Remaining Questions about Today's CASE:

A few questions remain regarding the ECG in today's case:

• Are there more "hidden" P waves?
• What is the etiology of beats #5 and #11 in Figure-2?
• Is the overall rhythm in today's case related to the presyncopal episode that prompted this 86-year old man to present to the ED?

What about Beats #5 and #11?

For clarity — I show only the long lead II rhythm strip in Figure-3. Note that I have now added 3 additional PINK arrows (ie, over the small "hump" that appears just after the QRS of ventricular beat #9 — and at the peak of the T waves that precede beats #5 and 11).

• Isn't it logical to propose that the PINK arrow I have added just after the QRS of beat #9 must represent another on-time sinus P wave?
• And — Aren't the T waves that precede beats #5 and #11 in Figure-3 ever-so-slightly taller than T waves of the other ventricular beats in this tracing?
• Isn't it logical to therefore propose that the PINK arrows I have added before beats #5 and #11 — are likely to represent additional on-time sinus P waves that are conducted to the ventricles (albeit with a slightly prolonged PR interval) to produce beats #5 and #11?

Figure-3: For clarity — I focus on the long lead II rhythm strip. Note that I've added 3 additional PINK arrows since Figure-2 (ie, over the small "hump" that appears just after the QRS of ventricular beat #9 — and at the peak of the T waves that precede beats #5 and #11).

What is the Clinical Significance of AIVR in this Case?

As discussed in ECG Blog #108 — AIVR generally occurs in one of the following Clinical Settings: i) As a rhythm during cardiac arrest; ii) In the monitoring phase of acute MI (especially with inferior MI); or, iii) As a reperfusion arrhythmia (ie, following thrombolysis, acute angioplasty, or spontaneous reperfusion). It may also occur in patients with underlying coronary disease, cardiomyopathy, and/or with digoxin toxicity. 

• On rare occasions — AIVR may occur intermittently in otherwise healthy subjects without underlying heart disease. If such subjects are asymptomatic during episodes — then no treatment is needed.
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• Regarding Today's CASE: The patient is elderly (86 years old) — and he presented following a presyncopal episode. The patient may have SSS (Sick Sinus Syndrome) as the reason for presyncope. The other main consideration — is to take another look at the 12-lead ECG, and assess this for recent ischemia or infarction.
• Assessment for QRST morphology is best accomplished by looking at sinus-conducted beats — since Q waves and ST-T wave changes are often difficult to evaluate for ventricular beats. To facilitate this assessment in Figure-4 — I've enclosed within dotted RED rectangles the QRST complexes to be evaluated within various leads on the 12-lead tracing for sinus-conducted beats #5,6,7; and #11,12,13. These suggest that there is some QRS widening for these sinus-conducted beats (ie, a nonspecific IVCD), with some nonspecific ST-T wave flattening — but nothing that looks acute.

Figure-4: Taking another look at the 12-lead tracing in today's case. I've enclosed within dotted RED rectangles — the QRST complexes to be evaluated within various leads on the 12-lead tracing for sinus-conducted beats #5,6,7; and #11,12,13 (See text).

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LADDERGRAM Illustration:

Clarification of the mechanism in today's arrhythmia is best explained by laddergram illustration (Figure-5).

• As I have often emphasized — it takes a little time to get good at drawing laddergrams (See ECG Blog #188). In contrast — It is not difficult to learn how to read laddergrams!
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• In Figure-5 — Regular sinus P waves are seen conducting in the Atrial Tier, except for the first 4 beats for which I don't see evidence of atrial activity.
• The wider beats in Figure-5 that are not preceded by P waves  are ventricular. In the laddergram — these beats originate from the Ventricular Tier — and conduct to some degree beyond the AV node. These ventricular beats constitute 2 short runs of AIVR (ie, beats #1,2,3,4; and #8,9,10).
• Retrograde conduction from ventricular beats #8 and 9 prevents forward conduction of the on-time sinus P waves that are seen just before the onset of beat #8 — and just after the QRS of beat #9.
• Retrograde conduction from ventricular beats #4 and #10 results in "concealed" conduction — and slows forward conduction of the next on-time sinus P waves that are hidden within the T waves of beats #4 and #10 (dotted RED lines seen within the AV Nodal Tier).
• Beats #6,7; and 12,13 — are normally conducted sinus beats.
• Presumably — the run of AIVR from beats #1-thru-4 inhibited the SA node from firing during this period.

Figure-5: Laddergram illustration of today's arrhythmia.

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Acknowledgment: My appreciation an anonymous clinician for the case and these tracings.

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Relevant ECG Posts to Today's Case:

• ECG Blog #185 — Reviews the Ps, Qs & 3Rs Approach to systematic rhythm interpretation.
• ECG Blog #210 — Reviews the every-other-beat Method for estimating the rate of regular rapid rhythms.
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• ECG Blog #188 — Reviews the essentials for reading (and/or drawing) Laddergrams, with LINKS to numerous Laddergrams I’ve drawn and discussed in detail in other blog posts.
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• ECG Blog #108 — Reviews the concept of AIVR.
• Riera ARP, et al: AIVR: Chronology and Main Discoveries: Indian Pacing and EP Journal 10: 40-48, 2010.
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• ECG Blog #68 — Reviews the concept of "concealed" conduction.