EKG & U

A Christmas Conundrum

George Veenhuyzen, MD

About the Author

George Veenhuyzen is an adult cardiac electrophysiologist at the Libin Cardiovascular Institute of Alberta in Calgary. He is interested in the diagnosis and management of all arrhythmias, particularly using catheter ablation.

An elderly man was admitted to hospital after a fall. He had suffered several falls in the recent past. The electrocardiogram (EKG) shown in Figure 1 was routinely performed while he was resting in bed. What is your diagnosis?

Discussion

At first glance, there appears to be a wide complex tachycardia at approximately 240 bpm. Upon closer inspection, there are narrow QRS complexes marching through the tracing at a rate of approximately 60 bpm. The correct diagnosis is provided by lead I: normal sinus rhythm! With that knowledge, the “wide complex tachycardia” cannot be related to any physiological cardiac activity and must be some sort of artifact. Sources of artifact can be exogenous (electromagnetic interference) or endogenous (originating from muscles other than the heart).

An EKG performed several minutes after a medication was administered is shown in Figure 2. What was the medication?

There appear to be negative, sawtooth flutter waves (at a rate of approximately 240 bpm) most apparent in the inferior leads. However, careful inspection, particularly of leads I, V1, and V2, reveals sinus P waves preceding every QRS complex (arrows), indicating that he is still in sinus rhythm at around 60 bpm. The right atrium cannot be in atrial flutter and sinus rhythm at the same time, so once again, the “flutter waves” must be an artifact. The rate of the artifact has not changed (around 240 cycles per minute), but it has diminished in amplitude compared with the previous EKG. What medication could diminish the magnitude of an electrocardiographic artifact?

The salient clues include his history of falls and the frequency of the artifact (240 cycles per minute, or four cycles per second). Parkinson’s disease frequently produces a tremor with a frequency of four to six cycles per second. If you surmised that the medication administered between the EKGs in Figures 1 and 2 was levodopa, you are correct!

In this case, because lead I is a clean tracing, free of artifact, we can conclude that neither upper limb is involved in the tremor. Both EKGs demonstrate that the artifact has its greatest amplitude in II, III, and aVF, which all share a lower limb electrode. Thus, apart from demonstrating that a parkinsonian tremor can masquerade as wide complex tachyarrhythmias and atrial flutter, these EKGs also remind us that parkinsonian tremors can involve the feet.

Article citation: Veenhuyzen, G. A christmas conundrum. CJGIM 2007;2(4):12-13