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Variations in the PQ interval can be associated with certain medical conditions: Duration A long PR interval (of over 200 ms) indicates a slowing of conduction between the atria and ventricles, usually due to slow conduction through the atrioventricular node (AV node). [1] This is known as first degree heart block. [1]
In the Framingham Heart Study, however, the presence of a prolonged PR interval or first degree AV block doubled the risk of developing atrial fibrillation, tripled the risk of requiring an artificial pacemaker, and was associated with a small increase in mortality. This risk was proportional to the degree of PR prolongation. [7]
On ECG, this is defined by progressive prolongation of the PR interval, with a resulting dropped beat (the PR interval gets longer and longer until a beat is finally dropped, or skipped). [ 4 ] [ 5 ] Some patients are asymptomatic; those who have symptoms respond to treatment effectively.
Hypokalemia; Other names: Hypokalaemia, hypopotassaemia, hypopotassemia: An ECG in a person with a potassium level of 1.1 meq/L showing the classical changes of ST segment depression, inverted T waves, large U waves, and a slightly prolonged PR interval.
Second-degree atrioventricular block (AV block) is a disease of the electrical conduction system of the heart.It is a conduction block between the atria and ventricles.The presence of second-degree AV block is diagnosed when one or more (but not all) of the atrial impulses fail to conduct to the ventricles due to impaired conduction.
A 12-lead ECG of a woman with Ebstein's anomaly: The ECG shows signs of right atrial enlargement, best seen in V1. Other P waves are broad and tall, these are termed "Himalayan" P waves. Also, a right bundle-branch block pattern and a first-degree atrioventricular block (prolonged PR-interval) due to intra-atrial conduction delay are seen.
The P waves with a regular P-to-P interval (in other words, a sinus rhythm) represent the first rhythm. The QRS complexes with a regular R-to-R interval represent the second rhythm. The PR interval will be variable, as the hallmark of complete heart block is the lack of any apparent relationship between P waves and QRS complexes.
Corrected QT interval (QTc) The QT interval is measured from the beginning of the QRS complex to the end of the T wave. Acceptable ranges vary with heart rate, so it must be corrected to the QTc by dividing by the square root of the RR interval. A prolonged QTc interval is a risk factor for ventricular tachyarrhythmias and sudden death.