pathological ECG 

Pathological changes in an electrocardiogram (ECG) can provide valuable information about various cardiac conditions. Interpretation of ECG findings requires a comprehensive understanding of normal and abnormal electrical patterns in the heart. Here are some pathological ECG findings associated with specific cardiac conditions. 

As I  told  befor the purpose of using ECG is: 

• Heart rate

•  The origin of the impulse and its propagation (conduction) through the mass of the myocardium

•  The size of the heart cavities

•  The position of the heart

•  Extension and localization of an acute myocardial infarction (AMI)

•  Effects of changes in electrolyte concentration on myocardial properties

•  The effects of some drugs on the activity of the heart

•  Operation of an artificial pacemaker implanted in a patient

•  It does NOT provide data on myocardial contractility and pump function. This information can be obtained by cardiac catheterization or echocardiography

•  Represents the "gold standard" for the diagnosis of rhythm and driving disorders

Abnormal ECG, how can I read it?

First of all you have to know that we are looking for abnormalities of the wave and intervals, the rhythm and Axis. 

you have to check on: 

1. Heart rate: form RR interval 

HR = 300 \ R_R large squares 

if irregular Rythm HR= no. of cardia cycle in 6 x 10 ! 

2. The leads: 

 Leads 1 , 2 , aVL for the lateral surface. 

Leads 3 , aVF for the inferior surface. 

Leads aVR for the right atrium. 

Chest leads: 

V1 , V2 for the right ventricle 

Lead V3 , V4 for the ventricle septum and anterior wall of left ventricle 

Leads V5 , V6 for anterior and lateral wall of ventricle. 

Abnormalities of PR interval:

1st degree heart block: 

prolonged PR > 1 large box + fixed 

Normal = 200 ms , prolonged >200 ms 

second degree heart block : on 1 and 2lead , progressive prolonged PR then dropped QRS complex (Wenckebach phenomenon )

Third degree heart block :

A-V dissociation , abnormal QRS coplex. 

Abnormlities of the QRS complex : 

A axis deviation : 

B voltage: check lead V1, V6 for ventricular hypertrophy 

C Bundle Branch block : wide QRS complex 

D abnormal Q wave 

Q wave >1 small square width and deep indicate old transmural infraction 

Lead                            site 

1,2, aVF                     inferior 

1,aVL,V5, V6            lateral 

V3, V4 anterior 

V1, V2 septum 

St segment abnormalitis 

Elevated ST segment 

inverted T wave 

pathological Q 

Transmural infraction 

Depressed ST segment :

inverted T wave , subendocardial ischemia.

Abnormalitis of T wave :

inverted : 

Normal in aVR ,V1 

Ventricular Hypertrophy 

Ischemia 

Hypokalemia 

Hyperacute: recent transmural infraction, hyperkalemia 

Rythm : if regular or not . the distance between QRS should be equal. 

A look if you have sinus : Lead 2 and aVR (p wave negativ at aVR !)

if the rate more than 100 bit per sec , consider Tachycardia ,regular, rapid and normal QRS.

if the rate less than 60 , consider sinus bradycardia , regular , slow , normal QRS.

If you do not have a sinus : 

The Irregular rythem : the distance between QRS not equal , we consider :

Extral systole : abnormal p wave determine Atrial extrasystola 

abnormal QRS copmlex + abnormal T wave determine ventricular extrasystole 

Atrial flutter : 

Atrial fibrillation : no p wace , irregular QRS + F wave 

Ventricular tachycardia : no p or T wave , broad QRS