Week 8 - Axis Deviation, R-Wave Progression, Bundle Branch Blocks, and Fascicular Blocks PDF

Axis deviation occurs when the electrical current deviates from the normal direction....

Axis deviation occurs when the electrical current deviates from the normal direction. The cardiac axis is the general direction in which electricity is flowing through the What is the Cardiac Axis? heart. To determine the axis, look at leads I and aVF, and possibly lead II. Right ventricular hypertrophy is the most common cause, as the muscle in the ventricle is thicker and requires a stronger electrical signal to be generated by the right side. Wolff-Parkinson-White (WPW) syndrome, Causes of Right Axis Deviation right ventricular strain (e.g., pulmonary embolism) lateral myocardial infarction. Axis Deviation If lead I is positive and aVF is negative, you need to look at lead II. Left Axis Deviation If lead II is positive, the axis is normal. If lead II is negative, you have a left axis deviation. Left ventricular hypertrophy Left bundle branch block Causes of Left Axis Deviation Inferior myocardial infarction Wolff-Parkinson-White (WPW) syndrome Ventricular pacing Causes include ventricular rhythms and Extreme Axis Deviation hyperkalemia. The R-wave is the first upward deflection after the P-wave, signifying the beginning Determining the R-Wave of ventricular depolarization. R-wave progression is the electrical depolarization of the ventricles being seen from lead V1 to V6. R-Wave Progression What is R-Wave Progression? In normal R-wave progression, the R-wave is negative in V1-V2, becomes biphasic in V3-V4, and then positive in V5-V6. Myocardial infarction Cardiomyopathy Causes of Poor R-Wave Progression Right and left ventricular hypertrophy Bundle branch blocks Axis Deviation, R- Wave Progression, Bundle Branch Characterized by a wide QRS due to a delay in conduction, with a predominantly positive QRS in V1 and a W pattern in V6. Blocks, and Fascicular Blocks Causes include right ventricular hypertrophy, pulmonary embolism, Right Bundle Branch Block (RBBB) ischemic heart disease, rheumatic heart disease, congenital heart defects, myocarditis, and cardiomyopathy. LAD occlusion If the rSR' pattern is present in V1 but the QRS is normal, it indicates an incomplete Bundle Branch Blocks Incomplete RBBB RBBB. Characterized by a wide QRS due to a delay in conduction, with a predominantly negative QRS in V1 and a positive M shape in V6. Causes include dilated cardiomyopathy, Left Bundle Branch Block (LBBB) aortic stenosis, ischemic heart disease, hypertension, anterior myocardial infarction, hyperkalemia, and digoxin toxicity. Characterized by LAD, a negative rS complex in inferior leads, a positive qS complex in lateral leads, and increased QRS voltage in limb leads. Causes include myocardial infarction, coronary artery disease, left ventricular Left Anterior Fascicular Block (LAFB) hypertrophy, dilated cardiomyopathy, hypertrophic cardiomyopathy, degenerative disease, hypertension, hyperkalemia, myocarditis, and amyloidosis. Characterized by RAD, a negative rS complex in lateral leads, a positive qS complex in inferior leads, and increased QRS voltage in limb leads. Fascicular Blocks Left Posterior Fascicular Block (LPFB) Causes include ischemic heart disease, hyperkalemia, myocarditis, and cor pulmonale. Bi-Fascicular Block involves two of the three fascicles, either RBBB + LAFB or RBBB + LPFB. Tri-Fascicular Block involves all three fascicles below the AV node, resulting in complete heart block plus RBBB and either Bi-Fascicular and Tri-Fascicular Blocks LAFB or LPFB. Causes include ischemic heart disease, structural heart disease, aortic stenosis, anterior myocardial infarction, congenital heart disease, hyperkalemia, and digoxin toxicity.