No clinical info. What is the rhythm?
Image 1 long lead II
This is an irregular narrow complex tachycardia. Can this be atrial fibrillation (AF)? AF cannot create equal RR intervals. If you use a caliper, you will see that some RR intervals are the same. AF is generally irregular unless there is complete heart block or entrance block and the depolarization of the ventricles is by an AV junctional pacemaker. So, what is this?
Image 2 - Full disclosure strips
Some telemetry systems probably the older generations cannot generate the 7 leads in screen or page. If you are in that situation, it means it is time to upgrade your system.
Here in full disclosure you can see distinct + P waves in V1 and you can simultaneously compare it in II, III and aVF (+ P). The computed atrial rate is about 230 bpm (1500/6.5 small squares). There is also group-beating. Indicative of a Wenckebach phenomenon.
During my early blogging days, I interpreted this as atrial tachycardia (AT) for the sole reason that the atrial rate is about 230 bpm. Several textbooks that you will read will say that AT will have an atrial rate of about 150-250 bpm and atrial flutter (AFl) will have flutter rates of about 250-350 bpm.
The chapter on atrial tachycardia (AT) from the book by Das and ZIpes (Electrocardiography of Arrhythmias, 2012) will make you consider AT vs AFl. AT it defined as a regular atrial rhythm originating from the atrium at 100-240 bpm and previous classification was based in ECG that it has a constant rate and isoelectric line between two consecutive P waves . AT can have a reentrant mechanism around a scar in the atrium. This can mimic the pattern of atypical atrial flutter (noncavotricuspic dependent).
AFl is also typically a reentrant arrhythmia that is regular (tachycardia) with rates above 240-340 bpm and without an isoelectric baseline. However, AFL can also show isoelectric intervals between flutter waves in diseased atrial, or in the presence of antiarrhythmic drug therapy. AFl rate can slow with progression of atrial myopathy or with use of antiarrhythmic drugs such as amiodarone.
With this reasoning it is sensible to label this strip as AT vs AFl until proven by electrophysiology study.
Interpretation: AT with a block vs AFl with variable block
Das and Zipes. 2012. Electrocardiography of arrhythmias : a comprehensive review. Elsevier PA