Premature ventricular contractions (PVCs) on an EKG strip

How to identify PVCs in five steps

Ask the same five questions of every strip. The right-hand column is what each one finds on the strip above.

1. 1Rate

   That of the underlying rhythm. Count every QRS, including the PVCs, for the rate on the monitor.

   ~70 bpm

2. 2Rhythm

   An even sinus rhythm broken by a wide early beat and the long pause that follows it.

   Regular, with early beats

3. 3P waves

   Normal on the sinus beats. None before the PVC.

   None on the early beat

4. 4PR interval

   Normal on the sinus beats. Not measurable on the PVC.

   0.13 s on sinus beats

5. 5QRS

   Narrow on the sinus beats. 0.12 s or wider and bizarre on the PVC.

   0.08 s; early beat 0.15 s

What is happening in the heart

An irritable spot in the ventricular muscle fires on its own. The impulse spreads from cell to cell across the ventricles instead of down the fast conduction pathway, which takes longer and produces a wide, distorted QRS. The SA node is not disturbed and keeps its own time, but its next impulse arrives while the ventricles are still recovering and is wasted. The beat after that comes exactly on schedule, so the gap spanning the PVC equals two normal cycles.

More PVC strips: no two are the same

A rhythm is a set of rules, not a picture. These three strips all meet the rules for PVCs, with different numbers.

What PVCs get mistaken for

PVCs vs. premature atrial contractions (PACs)

A PAC is early too, but it has a P wave and a narrow QRS that looks like the patient’s other beats, and the pause after it is shorter. A PVC is wide and has no P wave.

PVCs vs. ventricular bigeminy

Isolated PVCs come now and then with several normal beats between them. If every second beat is a PVC, the rhythm is ventricular bigeminy.

PVCs vs. ventricular tachycardia

One PVC is one wide beat. Three or more in a row at a rate over 100 is ventricular tachycardia.

Causes of PVCs

• Hypoxia
• Myocardial ischemia and infarction
• Low potassium or low magnesium
• Caffeine, nicotine, alcohol and other stimulants
• Stress, anxiety and lack of sleep
• Heart failure and cardiomyopathy
• Digoxin toxicity
• Sometimes no cause at all, in a healthy heart

Why it matters

Occasional PVCs occur in healthy people and are usually harmless. They matter when they signal an irritable ventricle that could go on to ventricular tachycardia or fibrillation. The warning signs are PVCs that are frequent or increasing, that come in pairs or runs, that have more than one shape, that fall on the T wave of the beat before, or that appear during a heart attack.

What is done for PVCs

• Assess the patient, and check a pulse: a PVC may not produce one, so the pulse can be slower than the monitor rate.
• Check oxygen saturation, and potassium and magnesium results.
• Count how many occur per minute and note whether they are alike or of different shapes.
• Report new, frequent, paired or multiform PVCs, and any that land on a T wave.
• Treatment is aimed at the cause. Antiarrhythmic drugs are not given routinely for PVCs alone.

Study summary, not a protocol. Follow current American Heart Association guidelines and your facility’s policies. See the medical disclaimer.

Common mistakes with PVCs

• Ignoring the pattern. One PVC is rarely a problem; the trend over minutes and hours is what matters.
• Calling a wide early beat a PAC without checking for a P wave.
• Taking the heart rate from the monitor alone when many beats are PVCs that may not perfuse.

Questions about PVCs