The ECG in the figure below was obtained from a 43-year-old man who presented to his primary care physician because he “wasn’t feeling well.” His symptoms suggested an influenza-like syndrome. The ECG was ordered because of some associated and atypical chest discomfort.
- Are you concerned about the ST-T wave changes on this tracing?
- Any other findings of note?
Interpretation: The reason we selected this tracing was not because of the ST-T wave changes. Instead, our focus was on the cardiac rhythm. This is not a sinus rhythm. It can’t be since there is no upright P wave in lead II. In fact, no P wave at all is seen preceding any of the 15 QRS complexes in the long lead II rhythm strip at the bottom of the tracing. That said, atrial activity is seen in several other leads. Specifically, there is a small but upright P wave with fixed PR interval preceding each QRS complex in leads I and aVL. There is also a small negative P wave preceding each beat in lead III, and tiny upright P waves are seen in leads V1 and V2. This is a low atrial rhythm at a rate slightly less than 100/minute. Otherwise, intervals and the mean QRS axis are normal. There is no chamber enlargement, and there are nonspecific ST-T wave changes in multiple leads that do not appear to be acute.
As stated, the reason this ECG was obtained was the patient’s description of atypical chest discomfort. While ultimate decision-making depends on clinical assessment of the patient, this ECG should be reassuring in that at least there are no acute changes. The presence of nonspecific ST-T wave abnormalities and a non-sinus (low atrial) rhythm are not pathologic per se and may simply reflect that the patient was not feeling well with an influenza-like illness. Whether to repeat the ECG if the patient’s clinical course is otherwise uneventful is a determination that can be decided in follow-up.
Take-Home Point: Assuming no dextrocardia or lead misplacement, if there is no upright P wave in lead II then the rhythm is not sinus. Other leads may sometimes visualize atrial activity not seen in lead II. This is especially true when the rhythm is non-sinus. Therefore, be sure to survey each of the other 11 leads before concluding that no atrial activity is present.