Chapters 11, 12, 13 Electrocardiogram Dr. Marko Ljubković Department of Physiology
Normal EKG
EKG – Principle of Detection
AP vs. EKG
EKG Leads Standard leads Precordial (chest) leads
Current Flows during Ventricular Depolarization
Cardiac Current Vectors Axes of the leads Average cardiac electrical axis (mean of all instantaneous vectors) Resultant (instantaneous) vector
Vectorial Analyses Determination of projected vectors with standard leads
Vectorial Analysis of the Normal EKG Instantaneous vectors during atrial depolarization (similar to average vector)
Instantaneous vectors during ventricular depolarization Q wave – left part of the septum depolarizes first Vectorial Analysis of the Normal EKG
Ventricular repolarization Vectorial Analysis of the Normal EKG
Average Cardiac Electrical Axis Constructed from QRS complexes of standard leads Indicates the mean direction of depolarization spreading through the ventricle Normally around 59º May be pathologically altered (axis deviation)
Ventricular Hypertrophy Left ventricular hypertrophyRight ventricular hypertrophy
Bundle Branch Block Blok lijeve grane snopa Vector directed to the side of the block QRS prolonged
Arrhythmias Abnormal sinus rythms: Tachycadia (fever, sympathetic stimulation) Bradycardia (athletes, carotid sinus syndrome)
Atrioventricular Block Possible causes: AV node ischemia AV node or bundle compression Myocarditis Excessive vagal stimulation First degree block Second degree block Complete AV block
Premature Contractions (Extrasystolae) Atrial extrasystole AV nodal extrasystole Ventricular extrasystolae
Paroxysmal Tachycardia Supraventricular (atrial and AV nodal) Common in young, healthy individuals Ventricular Often caused by ischemia May precede ventricular fibrilation
Ventricular Fibrillation Electric shock to the heart (alternating current ~ 60 Hz) Pathological cardiac alterations Dilatation Reduced velocity of conduction
Atrial Fibrillation Common in dilated atria Lack of P waves QRS-T complexes preserved Irregular rhythm