90. A 62-yeаr-оld wоmаn is cоmplаining of palpitations and feeling dizzy. She said this happened yesterday, and she sat down and it went away. She has a history of hypertension and is taking irbesartan (an angiotensin receptor blocker). Her vital signs are as follows: temperature, 98.8 ºF; pulse irregular, 110 beats per minute; respiratory rate, 20 per minute; and blood pressure, 110/70 mm/Hg. An electrocardiogram will likely reveal: