This is one of five consecutive serial ECGs that I performed several years ago on a patient in our Outpatient ECG Lab.  The patient was asymptomatic and the ECG was ordered as "Routine" by the patient's Primary Care Provider (PCP).  I deliberately "froze" the tracing on the screen and captured this image because I wanted to show a transition on the ECG.

No clinical patient data available.

What does this tracing show?  Choose the correct answer from the list below.

(1.)  Patient with Wolff-Parkinson-White (W-P-W) syndrome and intermittent ventricular preexcitation.  Sinus bradycardia with maximal preexciation on the first 3 beats.  Lesser preexcitation on the 4th beat due to the Concertina effect.  Normal conduction on the last 3 beats.

(2.)  Junctional escape rhythm (i.e., junctional bradycardia) with left bundle-branch block (LBBB) aberrancy dissociated from a sinus bradycardia.  Incomplete LBBB aberrancy on the 4th beat.  Normal conduction on the last 3 beats.

(3.)  Idioventricular escape rhythm on the first 3 beats, presumably originating from the right ventricle (RV) and dissociated from a sinus bradycardia.  Ventricular fusion on the 4th beat.  Normal conduction on the last 3 beats.

(4.)  Ventricular demand pacing (rate about 40/min) from an Implantable Cardioverter-Defibrillator (ICD) and dissociated from a sinus bradycardia on the first 3 beats.  Paced fusion on the 4th beat.  Normal conduction on the last 3 beats. 

(5.)  None of the above.

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