EMS 12-Lead: No, doubling the paper speed will not reveal hidden P-waves

Apparently I went to the Rick Bukata School of Titling Articles.

A 22-year-old male presents with agitation and delirium after smoking an unknown substance that an equally unknown person on the street offered him. You note a rapid radial pulse at around 150 bpm and attach him to the cardiac monitor:

Figure 1. Initial rhythm at normal paper speed.

Figure 1. Initial rhythm at normal paper speed (25 mm/s).

Well now we’re in a tough spot. It’s difficult to tell whether Fig. 1 shows sinus tachycardia or some non-sinus narrow-complex tachycardia (we’ll use the colloquial shorthand of “SVT” to include all those other options on the differential, including AVNRT, AVRT, ectopic atrial tachycardia, junctional tachycardia, etc…). If it is indeed sinus tach, then the requisite P-waves must be those upright deflections in II and III and superimposed on the T-waves.

Is there something we could do to see if those really are P-waves buried in the T-waves?

If you’re like me, you were probably taught that it would be a clever move to double the paper speed in a situation like this to separate the P’s from the T’s, revealing the diagnosis of sinus tachycardia. Let’s see what happens when we do that.

For the rest of this case and discussion please follow this link or click on the rhythm strip above.

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