Before you start breaking down the rhythm strip, take a few seconds to formulate a general impression of what is happening and what is the main problem. Is the main problem with the strip a single event? Multiple events? Are you dealing with more than one rhythm, as occurs in AV blocks? Do you get a benign feel from the strip or is it a scary one?
Many times, what happens is that you get caught up in the minutiae of interpreting a strip and forget to formulate this overall impression. In other words, you pick up all of the little findings on the strip, but you miss the obvious diagnosis. You can’t see the forest for the trees. Formulating an original impression will let you first see that there is a forest, and then you can go in and see if it is made up of pine trees, oaks, or birches.
Formulating an original impression does not mean that the thoughts are set in stone. The overall impression is basically that—an impression. An impression can change with the data that you will obtain from your more sequential analysis, or it can be verified by the same information.
First, ask yourself: Is this a patient I have to see emergently? By this point, you should have a fair idea of a dangerous rhythm versus a rhythm that is probably not so dangerous by simply glancing over the strip. Do you need to get additional leads? If you have no clue as to what the rhythm is, call for help. It pays to call for help early. If you can figure the strip out while help is arriving, so much the better. Remember, the seconds pass by very, very slowly if you wait too long before calling for help. Those seconds can seem like an eternity. Know your limitations and don’t be afraid to ask for help!
Secondly, mentally compare the strip you are analyzing with a mental picture of a perfect normal sinus rhythm. Focus on the differences. If you see problems with the P waves, you need to focus on that part of the analysis and should start thinking about some supraventricular pathology. If the problem is with wide QRS complexes, you need to think about ventricular rhythms or supraventricular rhythms with preexisting conditions (such as bundle branch blocks), electrolyte abnormalities, or aberrancy (for example Ashman’s phenomenon). Then you can ask some secondary questions, like: If it looks like a bundle branch block, which one is it? If you are thinking aberrancy, is it rate-related aberrancy or is there something particular about those complexes? (Right bundle branch blocks are more commonly seen in aberrancy-related blocks.)
Lastly, compare the strip mentally again, but this time to a perfect example of the arrhythmia that you are suspecting. For example, suppose you thought that the rhythm abnormality was an atrial flutter with 2:1 conduction. Mentally compare your strip to some of the atrial flutters with 2:1 conduction that you have studied so far. What is the rate? Do they look similar? Do you see buried F waves?
Now that you have formulated your general impression, you can begin to get down to specific questions. Let’s move on to them at this point.