AV Blocks First-Degree AV Block PR interval >0.21 seconds Second-Degree AV Block (Mobitz I) Progressive delay until conduction blocked Second-Degree AV Block (Mobitz II) Conduction of selected impulses through the AV node Third-Degree AV Block No atrial impulses are conducted through the AV node Atria and ventricles fire at their intrinsic rates
Bundle Branch Blocks Right Bundle Branch Block
The Turn-Signal Rule QRS >0.12 seconds throughout the ECG Look at the QRS in V1 Identify the J point Draw a horizontal line Triangle pointing up indicates RBBB Triangle pointing down indicates LBBB
Hemiblocks Left Posterior Hemiblock Principal finding is a rightward shift in the QRS axis
Hemiblocks Left Anterior Hemiblock Principal abnormality is a shift in the QRS axis far to the left
Left Bundle Branch Block
Right Bundle Branch Block
Chamber Enlargement Atrial Enlargement Ventricular Hypertrophy Causes Right-sided enlargement and hypertrophy Secondary to long-term pulmonary disease Left-sided enlargement and hypertrophy Secondary to long-term hypertension
Right Atrial Enlargement
Left Atrial Enlargement
Right Ventricular Hypertrophy
Left Ventricular Hypertrophy
Cardiac Conductive System ECG Recording ECG Leads Mean QRS Axis Determination The Normal 12-Lead ECG Disease Findings Conduction Abnormalities Prehospital ECG Monitoring