STEPUP Cardiovascular System: Arrhythmias - Premature Complexes

Question 1

What are premature atrial complexes (PAC)? What are causes?

Answer 1

1) This early beat arises within the atria, firing on its own
2) Causes include adrenergic excess, drugs, alcohol, tobacco, electrolyte imbalances, ischemia, and infection

Question 2

What should you look for on ECG that is indicative of a PAC? What about the QRS complex?

Answer 2

1) On ECG, look for early P waves that differ in morphology from the normal sinus P wave (because these P waves originate within the atria and not the sinus node)
2) QRS complex is normal because conduction below the atria is normal. There is usually a pause before the next sinus P wave

Question 3

How often do PACs occur and are they significant?

Answer 3

PACs are found in more than 50% of normal adults who undergo Holter monitoring and are of no significance in a normal heart, but may be a precursor of ischemia in a diseased heart

Question 4

What may PACs cause?

Answer 4

May cause palpitations or give rise to PSVTs

Question 5

Are PACs usually symptomatic and do they require treatment? Should you monitor them? What treatment may be helpful, if symptomatic?

Answer 5

1) Usually asymptomatic and do not require treatment
2) Monitor for increased frequency
3) If symptomatic (e.g., palpitations), beta-blockers may be helpful

Question 6

What is a premature ventricular complex (PVC)? In which patients do they occur? What are causes?

Answer 6

1) This early beat fires on its own from a focus in the ventricle and then spreads to the other ventricle
2) PVCs can occur in patients with or without structural heart disease
3) Causes include hypoxia, electrolyte abnormalities, stimulants, caffeine, medications, and structural heart disease

Question 7

What are PVCs conducting through in the heart and what does this cause on EKG?

Answer 7

Since conduction is not through normal conduction pathways, but rather through ventricular muscle, it is slower than normal, causing a wide WRS

Question 8

What do QRS complexes look like on EKG for a PVC? What do P waves look like on EKG for a PVC?

Answer 8

1) Wide, bizarre QRS complexes followed by a compensatory pause are seen
2) A P wave is not usually seen because it is “buried” within the wide QRS complex

Question 9

How often to PVCs appear in men undergoing 24-hour Holter monitoring?

Answer 9

PVCs appear in more than 50% of men who undergo 24-hour Holter monitoring

Question 10

Are most patients symptomatic with PVCs? What are symptoms? What treatment can be used for symptoms?

Answer 10

1) Most patients are asymptomatic
2) Some patients may have palpitations and dizziness related to PVCs
3) If symptomatic, beta-blockers may be used

Question 11

What is the presence of PVCs in patients with normal hearts associated with?

Answer 11

Increased mortality

Question 12

If a patient is found to have frequent PVCs, what should be done?

Answer 12

Workup for underlying structural heart disease should be initiated which may require specific treatment

Question 13

If patients have frequent, repetitive PVCs and underlying heart disease, what are they at increased risk for? What test should you order and why?

Answer 13

1) Sudden death due to cardiac arrhythmia (especially VFib)

2) Order an electrophysiologic study because patients may benefit from an ICD

Question 14

What did the Cardiac Arrhythmia Suppression Trial (CAST) I and CAST II studies show?

Answer 14

They showed that the use of antiarrhythmic drugs to suppress PVCs after MI increases the risk of death

Question 15

What are three types of PVCs?

Answer 15

1) Couplet: Two successive PVCs
2) Bigeminy: Sinus beat followed by a PVC
3) Trigeminy: Two sinus beats followed by a PVC