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

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

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

In the normal heart, at the beginning of ventricular depolarization, the QRS axis is oriented to the right because of left-to-right depolarization of the septum. This produces a small R wave in lead V1. Immediately following septal depolarization, the left and right ventricles depolarize. The size of the left ventricle results in a predominantly leftward axis for the remainder of the QRS complex.

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