About Looking at an Electrocardiograph: Part 1

Introduction: An Electron Goes for a Walk

This post is based on a talk given to Emergency Department Registrars in August 2016. The theme is "Looking at an Electrocardiograph"

I would like to approach this topic through the works of Paul Klee. Paul Klee (1879-1940) was born to a German father and a Swiss mother. He was a talented musician, painter and draughtsman, and eventually become a painter. His paintings contained letters, numbers, and arrows, often with figures of animals and people (Figure 1).

His work and his teaching at the Bauhaus (the widely influential German art school) between World War 1 and World War 2 explored the links between line and form and colour.

Figure 1

This is a 1925 painting by Klee called "Fish Magic". The painting has a rectangular piece of cloth glued onto the canvas. Lines pass from the canvas to the rectangle. Triangles, rectangles, circles, a clock, flowers and patches of colour are seen in the large rectangle, and fish swim into and out of the cloth.

We could regard the cloth as the heart, and the rest of the canvas as the process of recording and viewing the ECG. A figure with two faces looks towards and away from this "heart". However I want to consider another aspect of Klee: his teaching on the theory and practice of art. His lectures on art were published in English as the Paul Klee Notebooks. Two of his best known quotations are shown in Figure 2.

In 1933 Klee’s work was branded as ‘Degenerate Art’ by the National Socialists and he was dismissed from his professorial post at the Düsseldorf Academy of Fine Arts. He returned to Berne where he found himself in obscurity and isolation.

In 1935 Klee started to suffer from a mysterious disease. The symptoms included changes to the skin and problems with the internal organs. In 1940 Paul Klee died, and 10 years later his illness was diagnosed as ‘scleroderma’ (actually the rarest but most serious form, known as diffuse systemic sclerosis).

Figure 2

Twittering Machine (Die Zwitscher-Maschine) (Figure 2) is a 1922 work by Paul Klee that blends biology and machinery - four birds stand on a sinusoidal wire connected to a hand-crank

The birds and wire and the hand-crank are suspended over a rectangular strip, with a wire connecting the two.

There are many opinions about the meaning of this painting, but here we will regard the painting as linking bio-electricity in the heart and the line inscribed on the ECG paper.

To paraphrase Klee’s famous quote:

“An electrocardiogram is simply a electron going for a walk”

 

How Do We Learn To Interpret an ECG ?

There are four major phases:

  1. Learning the basics (the caterpillar stage) (Figure 3)
  2. Developing competence/confidence in ECG analysis (Text Book or Web-based Learning)
  3. Preparing for a (postgraduate) examination or diploma (Web-based Learning) - this is the stage that most of this audience [of Emergency Medicine trainees] has reached.
  4. "Real world" ECG evaluation 

Figure 3

Figure 3 is my "guess/estimate" about the time devoted to different topics when learning the basics of electrocardiography. In this stage the student usually devours all the available facts, lacking the experience to identify the most important information.

Figure 4

Figure 4 is my "guess/estimate" about the time devoted to different topics (ECGs) as one develops initial clinical competence, and then prepares for a postgraduate examination.

Figure 5

Figure 5 is my "guess/estimate" comparison of the topics studied when preparing for an examination, and the frequency of these findings in a real world setting.

There is often an inverse relationship between the time spent studying a topic and the likelihood of meeting it in a "real world" situation.

Paul Klee said “To emphasise only the beautiful seems to me to be like a mathematical system that only concerns itself with positive numbers”.

We can apply this to teaching and learning about ECGs: “To emphasise only the [most] abnormal [ECGs] is like a mathematical system that only concerns itself with negative numbers”

My aim is to discuss the 'technique' of ECG description, with an emphasis on real world cases. But first some comments on aphorisms.

 

Aphorisms for ECG Evaluation

An aphorism is"a pithy observation which contains a general truth"

Digression: Aphorisms is also an EP released in 2008 by the American group Red Sparowes

The following aphorisms are relevant to this blog:

  1. The answer depends on the question 
  2. We see what we know
  3. We see what we look for

 

The Answer Depends on the Question

Figure 6

In the science fiction comedy series "The Hitchhiker's Guide to the Galaxy" (Figure 6) there is a quest to find the answer to "The ultimate question of life, the universe and everything".  The answer turns out to be "42" - showing the importance of knowing the specific original question.

The cover of the "The Hitchhiker's Guide to the Galaxy" by Douglas Adams

When looking at ECGs (and not the origins of life) the questions that determine the answer are:

  1. Why was the ECG recorded ?
  2. What are the main changes ?
  3. Are the findings relevant ?

Figure 7

We See What We Know

We will illustrate this by looking at the CXR of a elderly man with dyspnoea (Figure 8).

Figure 8

The CXR (Figure 8) shows cardiomegaly, pulmonary congestion, a nasogastric tube and a healed fracture of the left clavicle. The CXR also has a linear shadow that passes from the apex of the right lung towards the right hilum, widening as it nears the hilum. The shadow is marked by green arrows in Figure 9.

Figure 9

This linear shadow is next to the right heart border and the superior mediastinum, and is easily overlooked. It is called a azygous fissure, and the lung tissue medial to it is sometimes called an azygos lobe. The azygous fissure/azygous loge is a normal variant that is found in about 1 percent of anatomical specimens and is seen in about 0.4 percent of chest radiographs. It is created when the vein that is a precursor to the azygous vein fails to migrate medially. This produces a deep pleural fissure in the apical segment of the right upper lobe. The azygous lobe is not a true accessory lobe as it does not have its own bronchus.

The correct diagnosis depends on having previously seen an azygous fissure on a CXR. Missing the diagnosis in this case has no clinical consequences. But what about this ECG of a healthy 33 year old man with a radial head fracture after falling off a ladder? 

Figure 10

The ECG resembles right bundle branch block (RBBB): there are S waves in Lead I and Lead V6, and Leads V1 and V2 have a RSR' morphology (Lead V3 has J point and ST segment elevation that does not resemble the findings in RBBR). The shape of the R' wave and the ST segment in Leads V1 and V2 are in fact characteristic (and diagnostic) of Type 1 Brugada pattern that is associated with an increased risk of sudden death.

 

Sometimes We See What We Can't Explain

Figure 11

Figure 11 is the CXR of a woman who has had her oesophagus removed because of cancer. There is an oval opacity next to the right heart border, extending from the hilum to the right diaphragm (and below [or ? behind] the diaphragm). My initial diagnosis was that the opacity was due to recurrence of her cancer. However the "mass" is the patient's stomach (Figure 12).

Figure 12

 

We See What We Look For

Case DB

This 63 year old man came to hospital because of persistent right sided discomfort. Figure 13 shows a CXR from 2012, and the CXR 4 years later.

Figure 13

Figure 13. [A]: This CXR was reported as normal, but the arrow shows a round opacity just above the right hilum; [B]: The anteroposterior CXR shows a large opacity that is immediately lateral to the tracheal bifurcation and overlies the right hilum and the upper right atrium; [C]: The lateral CXR shows that the mass extends from the hilum to the anterior mediastinum

The four year interval between the CXRs suggests that the mass is growing slowly, but malignancy is the main concern. If the mass is malignant its location raises the possibility of spread into the pericardium.

In this case the evaluation of the ECG (Figure 14) include a careful examination for ECG features of pericardial effusion.

Figure 14

Figure 14 is the ECG of Case DB. The rhythm is sinus, the frontal plane axis is normal, the QRS morphology is normal and the QT interval is normal. There are no features of pericardial effusion.

The rhythm strip (apparently) shows an interpolated atrial ectopic. We can use a laddergram to analyze this rhythm more carefully (Figure 15).

Figure 15

The underlying sinus rhythm is identified by black circles (P1 - P6). A conducted atrial ectopic complex (P'1) blocks the conduction of sinus complex P3 and is followed by a short lived cycle of re-entry in the atrioventricular node. This results in two conducted atrial ectopic complexes (P'2 and P'3) and non-conduction of sinus complex P4. Normal conduction of sinus complexes resumes at P5.

 

Case RN

This 43 year old woman had been suffering from back pain and weight loss for several months. A MRI of the lumbar spine showed bony metastases, and a scout film before a CT scan of the chest showed cardiomegaly (Fig 16).

Figure 16

Scout film before a CT scan of the chest and abdomen shows an enlarged heart with a globular shape. The clinical presentation and the shape of the heart suggest a pericardial effusion.

The admission ECG is shown in Figure 17.

Figure 17

The main findings are:

  1. Sinus tachycardia with a heart rate of about 125 beats per minute
  2. Small amplitude QRS complexes
  3. PR segment depression in Lead II and PR segment elevation in Lead aVR (See Figure 18)
  4. Slight beat to beat variation in the amplitude of the QRS complexes (well seen in Lead V4)

Figure 18

Single leads and rhythm strip from the admission ECG of Case RN, showing PR segment depression in Lead II and slight PR segment elevation in Lead aVR

The ECG change are those of pericarditis and pericardial effusion. This was confirmed on CAT scan of the chest (Fig 19) and on echocardiography that demonstrated early signs of pericardial tamponade.

Figure 19