Sinus Bradycardia

Preparation: Plan to spend 5-10 minutes familiarizing yourself with the animations of the PowerPoint and the key findings of this ECG.

Presentation Instructions: Present the image either by expanding the window (bottom right) in a browser or downloading the PowerPoint file (downloading is recommended).  Have the image pulled up in presenter mode before learners look at the screen to avoid revealing the diagnosis.  Ask a learner to provide an overall interpretation.  Then advance through the animations to prompt learners with key questions and reveal the associated graphics and teaching points. You can go back to prior graphics and questions by using the back arrow or scrolling back on the mouse wheel.

Official ECG Read: Sinus bradycardia at a rate of 35-40bpm with non-specific T-wave changes, likely “U” waves

Diagnosis: Sinus bradycardia likely attributable to hypokalemia and hypoglycemia in setting of insulin overdose. 

Teaching:

1. The best method for calculating the ventricular rate for irregular rhythms or with severe bradycardia is to count the total number of QRS in a 10-second strip and multiply by six.   
2. Sinus rhythm is defined by “a P before every QRS and a QRS after every P”.  If you have a QRS without a P there are premature ventricular contractions (PVCs) or ventricular escape.  If you have a P without a QRS there is a second or third-degree AV block. 
3. A ‘U' wave is a small deflection following a T wave, often best seen in anterior precordial leads (V2-4).  Prominent U waves are most commonly seen in bradycardia and hypokalemia but could be due to multiple other causes.