Chapter 15: Complex Cornucopia

INTRODUCTION

In normal sinus rhythm the heart is depolarized in a sequential, predictable fashion. From the sinoatrial (SA) node, the impulse first depolarizes the atria on its way to the AV node and then travels through the specialized conduction system to ultimately activate the ventricles. Each cell of the heart is depolarized on time, recorded on the ECG as the P wave, PR interval, and QRS complex, something that we can display graphically with a ladder diagram (Figure 15-1). But to liberally paraphrase Scottish poet Robert Burns, “The best laid plans of mice and men and the sinus node go oft awry.” With that introduction, let’s now discuss the subject of ectopic complexes.

Terminology of Ectopy

Any electrocardiographic complex that originates from a focus outside of the SA node may be termed ectopic. This is a large subject that is made more difficult by a lack of uniformity in nomenclature. But fear not, because I’m going to help you simplify the process. I recommend you follow a convention that describes the complexes by (1) the site of origin, (2) the timing relative to the native rhythm, and (3) with additional descriptors as needed. Depending on the situation, the modifiers may be placed either before or after you name the complex by origin and timing. The three-step method is summarized as follows:

• Step one: Identify the site of origin.

  • Atrial.

  • AV junctional.

  • Ventricular.

• Step two: Analyze the timing.

  • Premature (early).

  • Escape (late).

• Step three: Add descriptors as required.

  • Normally conducted.

  • Nonconducted (blocked).

  • Aberrantly conducted.

  • Retrograde conduction.

  • Interpolated.

  • Late (end) diastolic.

  • Fusion.

  • Concealed.

  • Reciprocal (echo).

  • Uniform/Multiform.

  • Repetitive or in a pattern.

For example, we can use the convention above to describe an ectopic complex that originates in the ventricles and occurs earlier than the next expected sinus complex as a ventricular premature complex (VPC). We first name the site of origin (the ventricles) and then the timing (premature). That was easy! In many texts, you will find the same complex described as a premature ventricular complex (PVC) instead of a VPC. It’s perfectly reasonable to identify the timing first and the origin second because both VPC and PVC are equivalent. But the “origin first-timing second” naming convention is something we can use consistently for both early and late complexes and the one I think is best.

Ectopy Schmectopy, What’s in a Name?

Even when using the recommended order, you are going to encounter many other ways to describe the same VPC. These include ventricular premature beat (VPB), ventricular premature contraction (VPC), ventricular premature systole (VPS), and ventricular premature depolarization (VPD). All of these terms are flawed. The ECG records electrical ...