QRS

QRS Complex
File:ECG-QRS-Complex.png
Diagram of a typical QRS complex on an ECG
Specialty	Cardiology

The QRS complex is a crucial component of the electrocardiogram (ECG), representing the depolarization of the ventricles of the heart. It is a key indicator of ventricular function and is used extensively in the diagnosis and monitoring of various cardiac conditions.

Structure and Function

The QRS complex is composed of three distinct waves:

• Q wave: The initial negative deflection following the P wave, representing the depolarization of the interventricular septum.
• R wave: The first positive deflection after the Q wave, indicating the depolarization of the main mass of the ventricles.
• S wave: The negative deflection following the R wave, representing the final depolarization of the ventricles at the base of the heart.

The duration of the QRS complex is typically between 0.06 and 0.10 seconds. A prolonged QRS duration may indicate a bundle branch block or other conduction abnormalities.

Clinical Significance

The QRS complex is essential in diagnosing various cardiac conditions:

• Myocardial infarction: Abnormal Q waves can indicate a previous myocardial infarction.
• Bundle branch block: A widened QRS complex suggests a delay in ventricular conduction.
• Ventricular hypertrophy: Increased amplitude of the R wave can indicate hypertrophy of the ventricles.
• Arrhythmias: Abnormal QRS morphology can help identify specific types of arrhythmias.

Interpretation

Interpreting the QRS complex involves analyzing its duration, amplitude, and morphology across different leads of the ECG. The axis of the QRS complex is also assessed to determine the direction of ventricular depolarization.

Pathological Variations

Several conditions can alter the appearance of the QRS complex:

• Left bundle branch block (LBBB): Characterized by a broad, notched R wave in leads I, aVL, V5, and V6.
• Right bundle branch block (RBBB): Identified by an "rSR'" pattern in lead V1 and a wide S wave in lead I and V6.
• Pre-excitation syndromes: Such as Wolff-Parkinson-White syndrome, which can cause a delta wave and a short PR interval.

Also see

• Electrocardiogram
• Cardiac cycle
• Heart conduction system
• P wave
• T wave

Cardiovascular disease A-Z

Most common cardiac diseases

• Cardiac arrhythmia‎
• Cardiogenetic disorders‎
• Cardiomegaly‎
• Cardiomyopathy‎
• Cardiopulmonary resuscitation‎
• Chronic rheumatic heart diseases‎
• Congenital heart defects‎
• Heart neoplasia‎
• Ischemic heart diseases‎
• Pericardial disorders
• Syndromes affecting the heart‎
• Valvular heart disease‎

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

A

• Accelerated idioventricular rhythm
• Acute decompensated heart failure
• Arteriosclerotic heart disease
• Athletic heart syndrome
• Atrial flutter
• Atrioventricular fistula
• Cardiovascular disease in Australia
• Autoimmune heart disease

B

• Brown atrophy of the heart

C

• Ebb Cade
• Cardiac allograft vasculopathy
• Cardiac amyloidosis
• Cardiac asthma
• Cardiac tamponade
• Cardiogenic shock
• Cardiogeriatrics
• Cardiorenal syndrome
• Cardiotoxicity
• Carditis
• Coronary artery aneurysm
• Coronary artery anomaly
• Coronary artery disease
• Spontaneous coronary artery dissection
• Coronary artery ectasia
• Coronary occlusion
• Coronary steal
• Coronary thrombosis
• Coronary vasospasm
• Cœur en sabot
• Coxsackievirus-induced cardiomyopathy

D

• Duke Treadmill Score
• Duroziez's disease

E

• Eisenmenger's syndrome
• Embryocardia
• Endocardial fibroelastosis
• Eosinophilic myocarditis

H

• Heart attack
• Heart failure
• Heart failure with preserved ejection fraction
• Heart to Heart (1949 film)
• High-output heart failure
• Hyperdynamic precordium

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

I

• Idiopathic giant-cell myocarditis
• Interventricular dyssynchrony
• Intraventricular dyssynchrony
• Isolated atrial amyloidosis

K

• Keshan disease

L

• Loeffler endocarditis

M

• Mydicar
• Myocardial bridge
• Myocardial disarray
• Myocardial rupture
• Myocardial scarring
• Myocardial stunning
• Myocarditis

N

• Nonbacterial thrombotic endocarditis

O

• OLR1
• Ostial disease

P

• Papillary fibroelastoma
• Pathophysiology of heart failure
• Postpericardiotomy syndrome
• Pulmonary vein stenosis

R

• Right axis deviation
• Roemheld syndrome

S

• Saturated fat and cardiovascular disease
• SCAR-Fc
• Shone's syndrome
• Strain pattern
• Subacute bacterial endocarditis
• Sudden cardiac death of athletes

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

T

• Traumatic cardiac arrest

V

• Ventricular aneurysm
• Vibroacoustic disease
• Viral cardiomyopathy

W

• Waon therapy