67 yom presents after syncope (while going to restroom). Mild dyspnea, no CP, BP 110/70

ECG findings

1. Sinus tachycardia with frequent PACs

2. Right axis : net QRS is (-) in lead I; QRS is closest to equiphasic in lead aVF axis close to +180 degrees

3. RAE (by lead II and lead V1 criteria)

4. S>R in V6 + Right axis deviation RVH

5. S1Q3T3 c/w right axis (big S in lead I) and RVH

6. T inversion in V1-V3:

ddx: anterior ischemia vs RV strain

Final dx: PE with signs of RV/RA overload

How to assess QRS axis?

1st step:Look in leads I and aVf, and potentially in lead II if needed

2nd step (not very important for residents): See where QRS is closest to isoelectric, the axis is 90 degrees perpendicular to it in the corresponding quadrant

RV enlargement leads to increased R wave height in the right-sided lead V1 and increased S wave in the left-sided lead V6