Mori Quartet Part 1 - "The Spike"

This is the first of four ECGs that have been kindly provided by Dr Alfredo Mori, an Emergency Physician from Melbourne, Australia.

Figure 1

This is the ECG of a 68 year old woman with a past history of hypertension, diabetes mellitus and severe lower back pain who came to hospital complaining of central chest pain that radiated into the back. 

+ Describe the main findings in this ECG

The main feature is the presence of small spikes that are perpendicular to the ECG tracing (both the baseline and the P-QRS-T complexes); the interval between the spikes is constant at (about) 2 mm.

The frequency of discharge of the spikes is (1500 ÷ 2) i.e. about 750 spikes per minute. The amplitude of the spikes ranges from nearly invisible (Lead I) to 2 mm (Lead V2) to about 5.5 mm (Lead II).

The vertical spikes run along the baseline and through the P wave, PR segment, ST segment and T wave of all the ECG complexes. Careful inspection of the QRS complexes show that some of the spikes are visible in the R wave of the QRS complex (Lead II) and in the downstroke of the S wave in a ventricular ectopic complex in Leads II and III. There is no constant relation between the spikes and the start of the P waves or QRS complexes.

These spikes are due to extra-cardiac activity. The patient does not have a pacemaker, but has a implanted sacral nerve stimulator for her back pain. The spinal stimulator is the cause of these spikes, which are recorded on the ECG tracing but do not affect the cardiac electrical activity ("spinal stimulator - heart dissociation").

Apart from the spikes, the ECG shows sinus rhythm, a ventricular ectopic complex, and ST depression in Leads II, aVF and V4 to V6, and T wave inversion in Lead III.


1. A good review of equipment related artefacts is found in this article: Patel SI, Souter MJ. Equipment-related electrocardiographic artefacts: causes, characteristics, consequences, and correction. Anesthesiology 2008; 108:138 – 48

2. "The Spike" is a 1931 essay by the British writer George Orwell in which he describes the experience of a night spent in the casual ward of a workhouse (colloquially known as a "spike") near London. This episode took place when he deliberately lived as a homeless person as part of the social experiment that was the basis of his book Down and Out in Paris and London.

3. "Cause it makes me feel like I'm a man. When I put a spike into my vein"

Lyrics from the song "Heroin" by the Velvet Underground, an American rock band, active between 1964 and 1973, that was formed in New York City. Its members included Lou Reed and John Cale. The band took its name from a book called "The Velvet Underground", written by Michael Leigh and published in 1963. The book's theme was aberrant sexual behaviour between consenting adults.