Understanding Premature Atrial Complex (PAC)

23 Questions

What is a Premature Atrial Complex (PAC)?

A single ECG complex occurring before the next normal impulse of the sinus node

Which of the following may cause a Premature Atrial Complex (PAC)?

Caffeine and alcohol consumption

What effect does a Premature Atrial Complex (PAC) have on the atrial rate?

Depends on the underlying rhythm

How does a Premature Atrial Complex (PAC) affect the ventricular and atrial rhythm?

Irregular due to early P waves

What is the QRS shape and duration following a Premature Atrial Complex (PAC)?

Usually normal, but may be abnormal

Which of the following is a potential cause of Premature Atrial Complex (PAC)?

Hypokalemia (low potassium level)

Which diagnostic test can identify the presence of valvular heart disease and provide information about left ventricular and right ventricular size and function?

Transesophageal echocardiogram (TEE)

Which arrhythmia is characterized by a rapid, regular atrial impulse at a rate between 250 and 400 bpm?

Atrial flutter

What is the important feature of atrial flutter that prevents it from causing ventricular fibrillation?

Presence of AV node block

What is the usual ventricular rate range in atrial flutter?

75-150 bpm

Which test may be performed to exclude myocardial ischemia or reproduce exercise-induced atrial fibrillation?

Exercise stress test

What is the purpose of electrical cardioversion in the treatment of atrial flutter?

To restore normal sinus rhythm

What is the main cause of atrial fibrillation?

Structural or electrophysiologic abnormalities in the atria

Where do hyperactive autonomic ganglia, involved in initiating impulses for atrial fibrillation, predominantly reside?

In the pulmonary veins

What is the range of the irregular, rapid atrial rate in atrial fibrillation?

300-600 bpm

What is the risk associated with a rapid ventricular response in atrial fibrillation?

Smaller stroke volume

Which cardiac structure is most often responsible for the origin of embolisms in nonvalvular atrial fibrillation?

Left atrial appendage

What is the role of the extrinsic and intrinsic cardiac autonomic nervous systems (CANS) in atrial fibrillation?

They regulate heart rate and rhythm

What effect does atrial fibrillation have on ventricular ejection?

Altered ventricular ejection

What determines the ventricular rate of response in atrial fibrillation?

Conduction through the AV node

What risk does atrial fibrillation pose to patients?

Heart failure, myocardial ischemia, and embolic events such as stroke

What is the role of the QRS shape and duration in atrial fibrillation?

Their shape and duration can be normal or abnormal

What impact does a rapid ventricular response have on cardiac output?

Reduces cardiac output due to smaller stroke volume and loss of atrial kick

Study Notes

Atrial fibrillation is a common arrhythmia, affecting 2.7 to 6.1 million Americans.
It is caused by abnormal impulse formation in the atria due to structural or electrophysiologic abnormalities.
The extrinsic and intrinsic cardiac autonomic nervous systems (CANS) are involved in the initiation and continuance of atrial fibrillation.
Hyperactive autonomic ganglia in the CANS, particularly in the pulmonary veins, initiate impulses and conduct them through the AV node to the ventricles.
The ventricular rate of response depends on conduction through the AV node, presence of accessory conduction pathways, and medications.
Atrial fibrillation is characterized by an irregular, rapid atrial rate (300-600 bpm) and a variable ventricular rate (120-200 bpm).
There is no discernible P wave and the QRS shape and duration are often normal but can be abnormal.
Patients with atrial fibrillation are at risk of heart failure, myocardial ischemia, and embolic events such as stroke.
A rapid ventricular response reduces ventricular filling time, resulting in a smaller stroke volume and a loss of atrial kick (25-30% of cardiac output).
The erratic nature of atrial contraction, altered ventricular ejection, and atrial myocardial dysfunction promote the formation of thrombi, especially in the left atrium, increasing the risk of embolic events.
The origin of embolisms for nonvalvular atrial fibrillation is most often the left atrial appendage.

Test your knowledge on Premature Atrial Complex (PAC) with this quiz that covers its causes, ECG characteristics, and associated conditions.

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