ectopy and abbarency

Question 1

Premature atrial contraction

Answer 1

Rate: determine underlined rate.
Rhythm: irregular.
P wave: Present, may be different w/ PAC.
P:QRS ratio is 1:1
PR-interval: Normal, may vary /w PAC.
QRS width- below 120ms.

An abnormal (non-sinus) P wave is followed by a QRS complex.

The P wave typically has a different morphology and axis to the sinus P waves.

The abnormal P wave may be hidden in the preceding T wave, producing a “peaked” or “camel hump” appearance — if this is not appreciated the PAC may be mistaken for a PJC.

PACS arising close to the AV node (“low atrial” ectopics) activate the atria retrogradely, producing an inverted P wave with a relatively short PR interval ≥ 120 ms (PR interval < 120 ms is classified as a PJC).
PACs that reach the SA node may depolarise it, causing the SA node to “reset” — this results in a longer-than-normal interval before the next sinus beat arrives (“post-extrasystolic pause”). Unlike with PVCs, this pause is not equal to double the preceding RR interval (i.e. not a “full compensatory pause”).

PACs arriving early in the cycle may be conducted aberrantly, usually with a RBBB morphology (as the right bundle branch has a longer refractory period than the left). They can be differentiated from PVCs by the presence of a preceding P wave.

Similarly, PACs arriving very early in the cycle may not be conducted to the ventricles at all. In this case, you will see an abnormal P wave that is not followed by a QRS complex (“blocked PAC”). It is usually followed by a compensatory pause as the sinus node resets.

rate

Question 2

PJC

Answer 2

Rate: determine underlined rhythm.
Rhythm: irregular.
P wave: none, antegrade, or retrograde.
P:QRS ratio is 1:1 or retrograde
PR-interval: none, short or retrograde
QRS width- below 120ms.

arrow QRS complex, either (1) without a preceding P wave or
(2) preceded by an abnormal P wave with a PR interval of < 120 ms (these “retrograde” P wave are usually inverted in leads II, III and aVF).
Occurs sooner than would be expected for the next sinus impulse.
Followed by a compensatory pause.

PJCs that arrive early in the cycle may be conducted aberrantly, most commonly with a RBBB morphology.

Question 3

PVC

Answer 3

Rate: determine underlined rhythm.
Rhythm: irregular.
P wave: none with PVC
P:QRS ratio is none
PR-interval: none
QRS width- above 120ms WIDE.

**Compensatory pause is seen.

Broad QRS complex (≥ 120 ms) with abnormal morphology.
Premature — i.e. occurs earlier than would be expected for the next sinus impulse.
Discordant ST segment and T wave changes.
Usually followed by a full compensatory pause.
Retrograde capture of the atria may or may not occur.

PVCs may be either:

Unifocal — Arising from a single ectopic focus; each PVC is identical.
Multifocal — Arising from two or more ectopic foci; multiple QRS morphologies

PVCs often occur in repeating patterns:

Bigeminy — every other beat is a PVC.
Trigeminy — every third beat is a PVC.
Quadrigeminy — every fourth beat is a PVC.
Couplet — two consecutive PVCs.
Triplet — three consecutive PVCs.

Question 4

Escape beats- junctional escape beat

Answer 4

Rate: determine underlined rhythm.
Rhythm: irregular.
P wave: none, antegrade or retrograde
P:QRS ratio is 1:1 or retrograde
PR-interval: none, short or retrograde
QRS width- below 120ms.

Question 5

ventricular escape beat

Answer 5

Rate: determine underlined rhythm.
Rhythm: irregular.
P wave: none with VEB
P:QRS ratio is 1:1 none
PR-interval: none 
QRS width- wide

Question 6

Ashman phenomenon

Answer 6

Ashman phenomenon, also known as Ashman beats, describes a particular type of wide QRS complex, often seen isolated that is typically seen in atrial fibrillation.
** It is more often misinterpreted as a premature ventricular complex.

Ashman beats are described as wide complex QRS complexes that follow a short R-R interval preceded by a long R-R interval.[3] This wide QRS complex typically has a right bundle branch block morphology and represents an aberrantly conducted complex that originates above the AV node, rather than a complex that originates in either the right or left ventricle.