If you are an instructor, or a fairly new student, you don’t always need to see “challenging” ECGs. But, you may not want to see “standard” ECGs from an arrhythmia generator, either. Every ECG contains subtle and not, so subtle characteristics of the person it belongs to. Take a minute to look at this ECG before reading the discussion, and ask yourself what you might surmise about the patient.
The Patient: We don’t know much about the actual patient this ECG came from. What we do know is that he is an elderly man with a history of heart disease who was hospitalized sometime in the past with an acute M.I. He is now on beta blocker medication and is on a diet, as he is approaching the “morbidly obese” classification. He is now in the ER with shortness of breath and mild chest pain. What does his ECG tell us?
The ECG: The rhythm is sinus at a rate of 60 bpm. Not quite “sinus brady”. His PR interval is 273 ms, or .27 seconds: first-degree AV block. Both of these findings can be attributed to the beta blocker, which slows the heart rate and slows conduction through the AV node. His QRS is slightly widened, at 106 ms, or .11 seconds. Not wide enough for a diagnosis of bundle branch block, but indicative of some delay through the interventricular conduction system. This could be due to multiple causes, including, but not limited to, his medication or his previous M.I. The QRS axis is -16 degrees, or very slightly to the left, which is normal. The R wave progression in the chest leads is appropriately from negative in V1 to positive in V6. However, he has lost the usual “RS” pattern in V2 and V3. The normal small “r” waves have gone, leaving pathological Q waves, a sign of the permanent damage done by his previous anterior-septal wall M.I. There is no ST elevation or depression, and his T waves are upright except in aVR, a normal finding. A perfectionist might not find the shapes of all of the ST segments to be perfect, but he does have coronary artery disease and advanced age. His QTc is within normal limits. The voltage in almost all leads is low. When not localized to one area, this can be a sign of excess tissue in between the heart and the ECG electrodes, which this man did have.
While the ECG does not tell us everything we need to know about this patient, it is able to point us in the direction of what questions to ask and what other tests to do. And it shows us a rate and rhythm that do not require immediate intervention.