Negative Concordant Precordial Pattern

Report:

Sinus rhythm 1

Supraventricular ectopic beat 1

AV dissociation 5

Ventricular pacemaker rhythm 75/min with 100% capture 3

Comment:

At first it appears that the large (therefore unipolar) pacemaker spikes track the P waves, but the latter gradually merge into the QRS complexes (best seen in the rhythm strip) and disappear. This is not a “physiological” pacemaker (now usually a universal, or DDD, model).

Sinus P waves disappear after the 6th one, followed by a premature atrial wave; there is no definite atrial activity visible after that.

The paced rhythm has the expected pattern of LBBB with LAD, indicating right ventricular apical position of the pacemaker tip. The V leads are all negative. This constitutes a criterion of the ventricular origin of the rhythm, clearly not diagnostically important in this case (it would be if the spikes were absent). In VT, this is one of the criteria distinguishing it from aberrantly conducted SVT. It is not, however, as specific as its counterpart, the positive concordant precordial pattern.

Reverse pulsus paradoxus? Well, in AV dissociation the inspiration may put the P waves, fortuitously, just before the QRS complexes, bringing into play the atrial transport. It’s as simple as that. A distinction student should be able to adduce at least two further causes of reverse paradox36.