Seven Dwarfs Undetected

Report:

Sinus rhythm

Ventricular tachycardia (non-sustained, 7-beat run) 138-142/min

1:1 retrograde conduction

Atrial escape beat

Comment:

The ectopic QRSs are so small that the monitor alarmed because of the low heart rate. At least it did alarm, one of the nurses said, rightly. It did the right thing for the wrong reason.

The ectopic morphology is convincingly ectopic, with slurred S descent and a puny R wave to clinch it (LBBB has no such thing in V1; if it does, one should look for a superimposed flutter or some such wave).

The retrograde P waves would be expected to produce regular cannon waves in the jugular venous pulse. They are rarely observed clinically, but may be recorded in a CVP readout. Electrocardiographically, the suppression of the sinus node output confirms their presence – it is a proof that the sinus node does not go on beating – yes, beating35 - undisturbed during the VT. The first beat to emerge after the VT paroxysm is an atrial escape, whose P wave is clearly different from the sinus P waves.

Not all the VEBs in this patient were dwarfs: below (Fig 34a) is a recording about an hour previously, with seven (relative) giants in sinus tachycardia on nitroglycerin drip. The confusing thing was that the giants have the same rate as other beats. Still, they are clearly fusion beats, in fusion tachycardia36.