This ECG belongs to a 56-year-old patient who was admitted by your colleague the previous night with hypercapnic respiratory failure. She was in cardiogenic shock with pulmonary edema. After intubation and mechanical ventilation, she was started on parenteral furosemide infusion and intravenous dobutamine. The ECG shown was obtained prior to the ICU rounds the following day. Are you worried?
Thanks for your interest and queries.
As for the first question. The atrial activity is too erratic, disorganized and inconsistent to result from a macro-rentry, that is atrial flutter. It is due to atrial fibrillation. You may call it coarse, given the fact that the fibrillatory waves are sometimes evident in some leads, not all!
As for the second question, the R wave in aVR is dominant throughout! the slight variation might be related to lead placement.
As for why the QRS is upright. I burrowed a few images from an amazing slide set (courtesy Dr. Sarita Choudhary) to explain the point. In a normal situation, the main vector from cardiac depolarization in directed towards the cardiac apex. However, in a patient with a lead pacing at the RV apex, ventricular depolarization STARTS at the apex and travels towards the base of the heart.
An since aVR (the cavity lead is situated over the base of the heart), it at times records a positive QRS complex (depending on the patient's body habitus, orientation of the heart in the mediastinum, height of the diaphragm ... etc). As you would imagine, a more horizontal position will likely make QRS negative in aVR as opposed to a vertically oriented position.
In a normal situation, because aVR will be looking at right angles to the main ventricular depolarization vector, R/S ratio in aVR tends to be the ~1. The more horizontal the heart, you would appreciate a deeper S wave than R (vector moving away from aVR) and in a more vertical position, the R/A ratio will be >1, as the main depolarization vector migrates closer to aVR.