Cardiac Conduction System Normal Waves of EKG ECG

ECG Waves n P wave : the sequential activation (depolarization) of the right and

ECG Waves n P Wave It is important to remember that the P wave

ECG Waves n QRS Complex simultaneous activation of the right and left ventricles, although

ECG Waves n Normal q-waves reflect normal septal activation n they are narrow (<0.

ECG Waves n R waves - normal septal r wave in Rt. precordial leads

ECG Waves n T wave usually in the same direction as the QRS except

Interval & Duration n PR interval: from onset of atrial depolarization (P) to onset

Interval & Duration n PR Interval : 0. 12 - 0. 20 sec n

Major ECG Abnormalities n Cardiac Enlargement & Hypertrophy n Bundle Branch Block n Myocardial

Cardiac Enlargement & Hypertrophy n RAE n Increase in P wave amplitude (>2. 5

Cardiac Enlargement & Hypertrophy n RVH n n Tall R in V 1(R/S>1) RAD

Bundle Branch Block n RBBB n n QRS vector toward Rt. QRS-T wave discordance

Myocardial Ischemia & Infarction n Factors n Nature of process : reversible vs irreversible

Myocardial Ischemia & Infarction n Ischemia Resting membrane potential decreaed n Shortening of action

Myocardial Ischemia & Infarction ST depression

Myocardial Ischemia & Infarction Exercise ECG

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Cardiac Conduction System

Normal Waves of EKG

ECG Waves n P wave : the sequential activation (depolarization) of the right and then left atria n QRS complex : 1 st phase – Dep. of IVS from Lt. to Rt 2 nd phase- Simultaneous Dep. of RV & LV n T wave : ventricular repolarization n U wave : origin for this wave is not clear the probably represents "afterdepolarizations" in ventricles

ECG Waves n P Wave It is important to remember that the P wave represents the sequential activation of the right and left atria, and it is common to see notched or biphasic P waves of right and left atrial activation. n P duration < 0. 12 sec P amplitude < 2. 5 mm Frontal plane P wave axis: 0 o to +75 o May see notched P waves in frontal plane

ECG Waves

ECG Waves n QRS Complex simultaneous activation of the right and left ventricles, although most of the QRS waveform is derived from the larger left ventricular musculature. n QRS duration < 0. 10 sec QRS amplitude variable 2 determinates of QRS voltages are: Size of the ventricular chambers (i. e. , the larger the chamber, the larger the voltage) n Proximity of chest electrodes to ventricular chamber (the closer, the larger the voltage) n

ECG Waves n Normal q-waves reflect normal septal activation n they are narrow (<0. 04 s duration) and small (<25% the amplitude of the R wave). n Should not confused with path` Q wave n

ECG Waves n R waves - normal septal r wave in Rt. precordial leads - normal R wave progression - tall R wave in Lt. precordial leads n S wave decrease progressively from Rt. to Lt n Transition zone - V 3 or V 4

ECG Waves

ECG Waves n T wave usually in the same direction as the QRS except in the right precordial leads(reversed direction of Rep. ). n In the normal ECG, the T wave is always upright in leads I, II, V 3 -6, and always inverted in lead a. VR. n n U wave Small(<1 mm), round deflection following T wave n Same polarity as T wave n Abnormal inc. in hypokalemia or drug(quinidine, procainamide, disopyramide) n Marker of inc. susceptibility to torsades de pointes n Best seen in Rt. precordial lead / slow HR n

ECG Waves

Interval & Duration

Interval & Duration n PR interval: from onset of atrial depolarization (P) to onset of ventricular depolarization (QRS) n QRS duration: duration of ventricular muscle depolarization n QT interval: duration of ventricular depolarization and repolarization n RR interval: duration of ventricular cardiac cycle (an indicator of ventricular rate) n PP interval: duration of atrial cycle (an indicator or atrial rate)

Interval & Duration n PR Interval : 0. 12 - 0. 20 sec n QRS Duration : 0. 06 - 0. 10 sec n QT Interval (QTc < 0. 40 sec) n Bazett's Formula: QTc = (QT)/Sq. Root RR

Rate

Axis

Axis Unipolar leads

Major ECG Abnormalities n Cardiac Enlargement & Hypertrophy n Bundle Branch Block n Myocardial Ischemia & Infarction

Cardiac Enlargement & Hypertrophy n RAE n Increase in P wave amplitude (>2. 5 mm) n LAE n Biphasic P wave in V 1 broad (-) component n Broad(>120 ms) notched P wave in limb leads

Cardiac Enlargement & Hypertrophy RAE

Cardiac Enlargement & Hypertrophy LAE

Cardiac Enlargement & Hypertrophy n RVH n n Tall R in V 1(R/S>1) RAD RV strain pattern LVH n n SV 1 +(RV 5 or RV 6)>35 mm RV 5 or RV 6>25 mm LV strain pattern Ra. VL>11~13, Ra. VF>20 mm

Cardiac Enlargement & Hypertrophy RVH

Cardiac Enlargement & Hypertrophy LVH

Bundle Branch Block n RBBB n n QRS vector toward Rt. QRS-T wave discordance Cong. Ht. dis, VHD, IHD LBBB n n n QRS vector toward Lt. Septal Dep. from Rt. to Lt. IHD, HTN, AV dis. CMP

Bundle Branch Block RBBB

Bundle Branch Block LBBB

Myocardial Ischemia & Infarction n Factors n Nature of process : reversible vs irreversible n Extent : trnasmural vs subendocardial n Duration : acute vs chronic n Localization n Underlying abnormalities

Myocardial Ischemia & Infarction n Ischemia Resting membrane potential decreaed n Shortening of action potential à voltage gradient betw. normal & ischemic zone à Current à ST segment deviation n n T wave inversion n n Repolarizaion prolonged a/w QT lengthening

Myocardial Ischemia & Infarction ST depression

Myocardial Ischemia & Infarction Exercise ECG

Myocardial Ischemia & Infarction