As a medical professional with expertise in cardiology, I can provide you with an understanding of the factors that can cause a prolonged QRS complex on an electrocardiogram (ECG).

The QRS complex represents the depolarization of the ventricles, which is the electrical activity that causes the heart muscle to contract and pump blood. A normal QRS duration is typically between 0.06 to 0.10 seconds. A prolonged QRS complex, which is longer than 0.10 seconds, can be caused by several conditions:


1. Bundle branch block: This is the most common cause of a prolonged QRS. It occurs when there is a delay or block in the electrical conduction system of the heart, specifically in the left or right bundle branches.


2. Myocardial infarction (heart attack): Damage to the heart muscle from a heart attack can disrupt the normal electrical conduction, leading to a prolonged QRS.


3. Cardiomyopathy: This is a disease of the heart muscle that can cause the heart to become enlarged, thick, or stiff, affecting its ability to contract and pump blood efficiently, which may result in a prolonged QRS.


4. Electrolyte imbalances: Abnormal levels of electrolytes such as potassium, calcium, or magnesium can affect the electrical activity of the heart.


5. Drugs and medications: Certain medications, particularly those that affect the heart's electrical activity, can prolong the QRS complex.


6. Hyperkalemia: High levels of potassium in the blood can cause a variety of ECG changes, including a prolonged QRS.

7.
Hypokalemia: Low levels of potassium can also affect the QRS complex.

8.
Myocardial fibrosis: The presence of fibrous tissue in the heart muscle can alter electrical conduction.

9.
Infiltrative diseases: Conditions such as amyloidosis, where abnormal proteins build up in the body's tissues, can affect heart function and the ECG.

10.
Congenital heart block: This is a condition present from birth where the electrical impulses that coordinate heartbeats are blocked.

1
1. Tachycardia-bradycardia syndrome: This is a condition where the heart experiences both rapid and slow heart rates, which can affect the QRS duration.

1
2. Sarcoidosis: This is a disease that forms tiny lumps of inflammation called granulomas, which can affect multiple organs including the heart.

It's important to note that a prolonged QRS complex can be a sign of serious heart conditions and should be evaluated by a healthcare professional.

read more >>

Rationale. The QRS complex duration is wide (>0.12 seconds or 3 small boxes) in every lead. Causes of a widened QRS complex include right or left BBB, pacemaker, hyperkalemia, ventricular preexcitation as is seen in Wolf-Parkinson-White pattern, and a ventricular rhythm.read more >>