[Biology Class Notes] on Electrocardiogram Pdf [2024]

What is Electrocardiogram:

An electrocardiogram is a kind of test which looks at your heart beat, rhythm and electrical impulse of heart. They monitor electrical activities of the heart and show it as a graphical representation which is known as electrocardiograph. By monitoring they provide us information if the heat has enlarged due to hypertension i.e high blood pressure or any other kind of myocardial infarction. This test is carried out by a trained healthcare specialist at clinics and hospitals. This test mainly involves attaching a small number of small and sticky sensors i.e known as electrodes to your arms, legs and chest from where these electrodes monitor electrical signalling of the heart.

Why it is Performed:

An Electrocardiogram is often used alongside other tests to help diagnose and monitor conditions affecting the heart. It can detect so many abnormalities of missfunction happening inside our heart. Some of the abnormalities which are detected by electrocardiogram are listed below:

Abnormal heart rhythm (arrhythmias)
If there are any blocked or narrowed arteries in your heart (coronary artery disease) are causing chest pain or a heart attack.
To find weather you have had a previous heart attack or not.
To monitor if the medicines are causing any side-effects to our body system.

Different Types of Electrocardiogram:

There are mainly three different types of ECG is performed:

Resting ECG: when your body is in resting state.under this type machine examine your heart beat during resting condition.
Ambulatory ECG: This type of ECG is conducted for 24 hours. The heart’s electrical impulses are measured by a device called the Holter Monitor.
Cardiac stress test: This test is used to measure ECG when you are on an exercise bike.

Types of Electrocardiogram Waves Produced During Checkup:

1. The P-wave:

It represents the electrical excitation (or depolarisation) of the atria, which leads to the contraction of both the atria.

Features of P- wave:

2. The QRS Complex:

It represents the depolarisation of the ventricles, which initiates the ventricular contraction.

Features of QRS complex:

QRS duration ≤ 0.10 sec

QRS amplitude varies from lead to lead and also from person to person. Two determinants of QRS voltages are:
Size of the ventricular chambers (i.e., the larger the chamber, the larger the voltage)
nearness of chest electrodes to ventricular chamber (the closer, the larger the voltage)

3. T-wave:

It represents the return of the ventricles from excited to normal state (repolarisation) and the end of the T-wave marks the end of systole.

The normal peak of the T wave is usually in the same direction as the QRS wave except in the right precordial leads. In the normal ECG the T wave is always upright.

By counting the number of QRS complexes that occur in a given time period, a person can determine the heart beat rate of an individual.

How to Perform Electrocardiogram:

They have small sticky electrodes attached to the arms, chest, legs.
These electrodes are connected to the ECG machine with the help of wires that help in detecting the electrical impulses occurring at each heartbeat.
These electrodes can detect every minute form of changes happening in heart muscles and draw every depolarising pattern of heartbeat on a graph.

Feature of Normal Electrocardiogram :

Heart beat should be in between 60-90 beats per minute (bpm).
PR Interval: 0.12 – 0.20 sec
QRS Duration: 0.06 – 0.10 sec
QT Interval (QTc ≤ 0.40 sec)

Medical Use of ECG:

The main function of ECG is to obtain information regarding the heart impulse. There is a great medical use of this information regarding your health issues like:

chest pain
shortness of breath
Lightheadedness
Dizziness
fainting spells
It is also required prior to any type of heart surgery, including surgery for pacemaker placement.

Why is an Electrocardiogram Performed:

ECG is done to determine or detect:

Abnormal heart rhythm (arrhythmias)
If there are any blocked or narrowed arteries in your heart (coronary artery disease) are causing chest pain or a heart attack.
To find weather you have had a previous heart attack or not.
To monitor if the medicines are causing any side-effects to our body system.

MCQ Questions on ECG:

1. ECG (Electrocardiogram) Was Developed First By

(a) Wilhelm His

(b) Steward

(d) Willem Einthoven

Answer: (d)

2. This is the Classic ECG Change in MI (Myocardial Infarction)

(a) ST-segment elevation

(b) T-wave inversion

(d) All of
these

Answer: (d)

3. In Which of these Conditions can Widened QRS and Tall-tented T Waves be Observed

(a) Hyponatremia

(b) Hyperkalemia

(d) Hyperphosphatemia

Answer: (b)

4. A Particular ECG Change Observed in Hypokalemia is

(a) ST segment elevation

(b) U wave(a position deflection after the T wave)

(d) Widening of the QRS complex and increased amplitude

Answer: (b)

5. ECG Report Must Consist of the Following Information

(a) Rhythm, cardiac axis

(b) Conduction intervals

(d) All of these

Answer: (d)

6. For the Normal Heartbeat, Depolarization Stimulus Originates in

(a) His-bundle areas

(b) Epicardium

(d) Atrioventricular (AV) node

Answer: (c)

7. The Characteristics – slurring of the Initial QRS Deflection, Shortened PR Interval, and Prolonged QRS Duration are of this Condition

(a) Atrial tachycardia

(b) Left bundle branch block

(d) Myocardial ischemia

Answer: (c)

8. P Wave Indicates

(a) Depolarization of right ventricle

(b) Depolarization of left ventricle

(d) Atrial to ventricular conduction time

Answer: (c)

9. Ventricular Muscle Depolarization is Indicated By

(a) PR interval

(b) P wave

(d) The QRS complex

Answer: (d)

10. ECG Identified By the PR Interval Tends to Become Longer with Every Succeeding ECG Complex Until There is a P Wave Not Followed by a QRS is Observed in

(a) Third-Degree Atrioventricular Block

(B) Second-Degree Atrioventricular Block, Type II

(D) First-Degree Atrioventricular Block, Type II

Answer: (c)

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