A patient with P waves more than QRS complexes in his ECG may have ____. a. Short PR interval b. Long PR interval c. long QRS duration d. ST segment shift e. SA Block f. Long QT syndrome
The correct answer and explanation is:
The correct answer is e. SA Block.
Explanation:
In an ECG, the P wave represents atrial depolarization, while the QRS complex represents ventricular depolarization. Normally, for each P wave, there is a corresponding QRS complex. However, in some cases, a patient may present with more P waves than QRS complexes, which could indicate an issue with the conduction of electrical signals from the atria to the ventricles.
One possible cause of this is Sinoatrial (SA) Block. The SA node is responsible for initiating the electrical impulses that regulate the heartbeat. In an SA block, the SA node fails to generate or properly transmit the impulse to the atria, resulting in the absence of a P wave that should correspond to a QRS complex. This leads to a situation where more P waves are seen than QRS complexes.
When there is an SA block, the atria continue to generate P waves, but some of these impulses fail to conduct through the AV node to initiate a ventricular contraction. This results in a delay or absence of the QRS complex after some of the P waves. The underlying problem is related to an interruption in the normal conduction between the atria and the ventricles, particularly in the SA node or the pathway from the SA node to the AV node.
While other conditions like a long PR interval, long QRS duration, or shifts in the ST segment can cause abnormal ECG findings, SA block is the most likely cause of more P waves than QRS complexes. Diagnosing this condition typically involves monitoring the rhythm over time and may require further tests such as an ambulatory Holter monitor to assess the frequency and duration of the block. Treatment may involve the use of a pacemaker if the block is symptomatic or persistent.