Complete Heart Block (CHB) ? Think Again


No clinical hx. Is this complete heart block (CHB)?


Image 1

This is sinus rhythm (SR) at about 88 bpm, first degree AV block, second degree advanced heart block or high-degree AV block, right bundle branch block.

It is very tempting to call this CHB. However, the clue that a sinus P wave is conducted is the irregularity of RR interval. There is sudden shortening of the RR interval (R4R5) vs the rest of the RR interval. If this is CHB the RR interval would be the same in all because in CHB the ventricles will be under the control of an ectopic junctional or ventricular focus. So, it would beat like clockwork. If there was shortening or difference in the RR interval, this means that a sinus impulse was conducted.

A simple trick to differentiate CHB from advanced heart block is the regularity of the RR interval. 



AT Will Look Like ST



Vignette: A 60 yo with h/o HTN, HLD, hyperthyroidism is admitted for sepsis. 

Cardiac telemetry showed event of tachycardia (~130 bpm).


Image 1

This will look like sinus tachycardia (ST). However, carrefull examination of initiation and termination would argue against ST. In ST thre is a gradual warm-up and cool-down in rate. In here there is "abrupt" or sudden increase and decrease in rate. Thus, this is paroxysmal atrial tachycardia (PAT)


Image 2


It is even better viewed by a heart rate histogram or trend.


Image 3



Looked Like Pacemaker Malfunction But Not


Vignette: A patient s/p pacemaker implantation was being monitored in the unit. The primary RN was notified of this event? Is this a pacemaker malfunction?


Image 1 - ECG case


Junctional Tachycardia: True or False



Vignette: A 67 yo with history of Diabetes Mellitus, Coronary Artery Disease, S/P CABG, Heart Failure with reduced Ejection Fraction (HFrEF), peripheral artery disease, s/p stenting is admitted due to sepsis. In telemetry, the several premature ventricular complexes (PVC's), couplet and nonsustained ventricular tachycardia (VT's) were noted. Aside from that the ventricular rate would jump from 60's to 100's (Image 1).


Image 1 - Heart Rate Trend or Heart Rate Histogram

When the patient is in the 100's, the telemetry strip would look like this (Image 2):


Image 2 - ECG case

Q: This is junctional tachycardia (True or False)

The Fusion is the Clue


A 30 yo with no known significant PMHx is c/o of SOB. This telemetry strip is:



Image 1 -  Fusion beat is marked with a red arrow which means the wide QRS complexes are ventricular ectopics (VT)

There are 3 QRS morphologies on this rhythm strip. QRS #4 is a sinus beat. QRS #5 is a fusion beat and the rest are VT in morphology. A fusion beat (aka "Dressler beat") is a QRS that has a morphology that is INTERMEDIATE between a sinus QRS and that of a ventricular complex. This intermediate QRS morphology is due to the simultaneous ventricular myocardial activation by a supraventricular impulse (sinus) and a ventricular ectopic.

Thus, this telemetry strip is SR with ventricular tachycardia (VT).

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