Step 2: Measure important intervals

Analysis and Interpretation of the Electrocardiogram

How to use this module

The 12 lead ECG

Waves and complexes

Intervals and segments

Approach to the ECG

Step 1: Determine the heart rate

Step 2: Measure important intervals

Step 3a: Calculate the electrical axis

Step 3b: Calculate the electrical axis

Step 3c: Calculate the electrical axis

Step 4: Evaluate the cardiac rhythm

Step 5: Inspect P waves for atrial enlargement

Step 6: Inspect QRS complexes for ventricular hypertrophy or low voltage

Step 7a: Inspect QRS complexes for bundle branch block or fascicular block

Step 7b: Inspect QRS complexes for bundle branch block or fascicular block

Step 7c: Inspect QRS complexes for bundle branch block or fascicular block

Step 7d: Inspect QRS complexes for bundle branch block or fascicular block

Step 7e: Inspect QRS complexes for bundle branch block or fascicular block

Step 8: Assess Q waves and determine significance

Step 9: Assess ST segments and T waves

Step 10: Measure QT interval for specific diagnoses

Printable version

Step 2: Measure important intervals

The measurement of important electrocardiographic intervals usually includes the PR interval, the QRS interval and the QT interval. At a standard paper speed of 25 mm/second, the width of each small square (1mm) represents 0.04 seconds. One large square (5mm) represents 0.2 seconds.

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