• June 12, 2024

Heart conditions from ECG for Clinical Nurses

Identifying specific heart conditions from an electrocardiogram (ECG or EKG) reading requires expertise in cardiology and a careful analysis of the ECG waveform patterns. However, there are some common ECG findings that can suggest the presence of certain heart conditions. Here are a few easily recognizable heart conditions based on ECG readings:

Normal ECG

normal ecg

A normal electrocardiogram (E.C.G) waveform consists of several key components:

P-Wave: Represents atrial depolarization, or the contraction of the atria. It appears as a small, upright wave.

QRS Complex: Indicates ventricular depolarization, the contraction of the ventricles. It consists of a Q-wave, R-wave, and S-wave. QRS complexes are typically narrow and well-defined.

T-Wave: Represents ventricular repolarization, when the ventricles relax. It is a slightly asymmetric, usually upright wave.

PR Interval: Measures the time between the P-wave and the start of the QRS complex, reflecting the electrical conduction from atria to ventricles.

QT Interval: Represents the duration of ventricular depolarization and repolarization.

Atrial Fibrillation

Atrial fibrillation

Atrial fibrillation occurs when there is,

– Irregularly irregular rhythm with no distinct P waves.

– Rapid, irregularly spaced QRS complexes.

  • May show fibrillatory (f) waves.

Atrial Flutter

Atrial Flutter

In atrial flutter there will be,

– Sawtooth pattern (sawtooth waves) of atrial activity (F waves) between QRS complexes.

  • A regular ventricular response.

Ventricular Tachycardia

ventricular tachycardia

In Ventricular Tachycardia, there is

– Wide QRS complexes (greater than 0.12 seconds).

  • Usually a rapid, regular rhythm originating in the ventricles.

Ventricular Fibrillation

ventricular fibrillation

In Ventricular Fibrillation, there is

– Chaotic, irregular waveform with no organized QRS complexes.

  • Often associated with an emergency situation.

Bundle Branch Blocks

There are two types of Bundle branch blocks, left bundle branch block (L.B.B.B) and right bundle branch block(R.B.B.B).

In L.B.B.B.,


QRS duration greater than 120 milliseconds

Dominant S wave in V1

Broad monophasic R wave in lateral leads (I, aVL, V5-6)

Absence of Q waves in lateral leads

Prolonged R wave peak time greater than 60ms in leads V5-6

Where as in R.B.B.B,


QRS duration greater than 120milliseconds

RSR’ pattern in V1-3 (“M-shaped” QRS complex)

Wide, slurred S wave in lateral leads (I, aVL, V5-6)

ST Elevation

st elevation

The ST segment is the flat, isoelectric section of the ECG between the end of the S wave (the J point) and the beginning of the T wave.

The ST Segment represents the interval between ventricular depolarization and repolarization.

The most important cause of ST segment abnormality (elevation or depression) is myocardial ischaemia or infarction.

You can see various ST segment elevation in various leads during an MI in this picture

ST-segment elevation is a significant deviation from the baseline in an electrocardiogram (ECG) where the ST segment, the portion between the S-wave and T-wave, is elevated above the isoelectric line. This finding typically indicates myocardial injury or infarction, commonly referred to as a heart attack. ST-segment elevation in specific leads can provide information about the location of the damage in the heart. It’s a critical sign that demands immediate medical attention. The degree of elevation, along with clinical symptoms, helps clinicians assess the extent of the injury and guide treatment decisions, such as reperfusion therapy or angioplasty to restore blood flow to the affected area of the heart.

ST Depression

st depression

ST-segment depression is an abnormal finding on an electrocardiogram (ECG) where the ST segment, which lies between the S-wave and T-wave, is shifted below the baseline. This deviation typically signifies myocardial ischemia, a condition in which the heart muscle isn’t receiving enough blood and oxygen due to narrowed or blocked coronary arteries. It can result from conditions like angina, coronary artery disease, or atherosclerosis.

The depth and duration of ST depression, as well as the presence of associated symptoms like chest pain or shortness of breath, provide valuable information to healthcare professionals. It’s an essential diagnostic tool in identifying cardiac conditions and assessing the risk of a heart attack. Continuous or recurrent ST-segment depression may suggest unstable angina or a non-ST-segment elevation myocardial infarction (NSTEMI). Early recognition of ST depression is crucial for prompt medical intervention, which may include medications, lifestyle changes, or invasive procedures like angiography and angioplasty to improve blood flow to the heart muscle.

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