Obese, Short of Breath, and Rationing Meds
ANSWER
The correct interpretation is sinus rhythm with a first-degree atrioventricular (AV) block, right superior axis deviation, and low voltage QRS complexes. The measured PR interval of 360 ms is correct!
The P waves are best seen in precordial leads V1 to V3. Notice that the P waves fall between the QRS complex and the T wave. The P wave is upright and not inverted, so it is not occurring retrograde from the preceding QRS complex. The sinus node depolarizes, and a long delay occurs within the atria and AV node before conducting down the normal conduction system in the ventricles. This conduction delay is so long that the preceding beat (QRS complex) is still repolarizing (T wave) by the time the sinus node depolarizes again. Thus, the P wave is responsible for the next QRS complex after duration of 360 ms.
A right superior axis deviation, also known as an extreme right axis deviation, is evidenced by an R-wave axis of 192°. Low-voltage QRS complexes are due to the patient’s body habitus. Morbid obesity significantly diminishes the electrical vectors measured by the surface ECG electrodes.
Finally, extra credit is due if you recognize the long QTc interval as well. The maximum normal QTc adjusted for a heart rate of 100 beats/min in men is 310 ms. This ECG barely meets that criteria; in this case, the prolonged QTc interval is of no significance.