This document provides guidance on electrocardiogram (ECG) interpretation for primary care physicians. It outlines the 6 key steps to analyze an ECG: rate, rhythm, axis, intervals, hypertrophy, and infarction/ischemia. Specific abnormalities that may indicate conditions like sinus tachycardia, atrial fibrillation, left ventricular hypertrophy, myocardial infarction, and heart block are described. Diagnosis of cardiac issues is aided by identifying changes in various leads that correspond to specific areas of the heart.

1. ECG Interpretation for Primary Care Physician Aamir A. Cheema M.D.

3. ECG Grid

5. Rate 300-150-100-75-60-50 300-150-100-75-60-50

6. What if rate is <50/min or rhythm is irregular ? Count the number of R waves in a 6 second strip and multiply by 10. For example, if there are 7 R waves in a 6 second strip, the heart rate is 70 (7x10=70).

10. Axis

11. Intervals PR interval: <200 msec (one big box) QRS complex:<100 msec (2½ small boxes) ST segment: evaluate for elevation or depression below baseline QT segment: roughly less than half of R-R interval At high or low heart rates, calculate corrected QT interval QTc = QT interval ÷ square root of the RR interval (in sec) The normal value for the QTc is <440 msec (2½ big boxes)

13. Normal ECG

15. Diagnosis?

16. One or more of the precordial leads (V1-V6) and leads I and aVL suggest anterior wall ischemia or infarction Leads V4 to V6 suggest apical or lateral ischemia or infarction

17. Diagnosis?

18. Leads V1 to V3 suggest anteroseptal ischemia or infarction.

21. Diagnosis?

22. Leads II, III, and aVF suggest inferior wall ischemia or infarction

24. Diagnosis?

28. Diagnosis?

30. Diagnosis?

31. New LBBB: Treat as ST Elevation MI i.e. rush to cath lab for PCI LBBB Diagnosis: Slurring of S wave in V5 and V6 and QRS duration > 100 msec (i.e more than 2½ small squares)

33. Diagnosis?