Back to the Future

Figure 1

This is the ECG tracing of a retired doctor with a past history of hypertension and an irregular heart rhythm. He presented with hemiplegia and neglect of the right side of his body.

+ Describe the main findings

The patient's age of 103 years is remarkable, and inevitably we think about the world into which he was born and the changes that have occurred during his lifetime. More on this later.

The main ECG findings are:

  • Atrial fibrillation is present: the heart rhythm is slightly irregular, the ventricular rate is between 80 - 100 beats per minute, and P waves are not seen. Low amplitude "f" (fibrillation waves) are seen in some Leads e.g. Leads I and aVL.
  • Left axis deviation
  • U waves are present in the V leads
  • There are no (definite) ST-T abnormalities.

We could stop our analysis now with the conclusion that the patient's acute symptoms are (most likely) due to a cerebral embolus from the left atrium, with the atrial fibrillation predisposing to the formation of intra-atrial clots. However, to paraphrase a famous nineteenth century intellectual this ECG case "...certainly presents some [other] features of interest".

Transition Zones and Poor R Wave Progression

In a normal ECG:

  • the QRS complex is predominately below the isoelectric line in Lead V1 i.e. the complex has a rS shape (Lead V1 may or may not have an R wave, but one should appear by Lead V2)
  • the amplitude of the R-wave gradually increases between leads V1-V4, reaching its maximum height in lead V4 or V5
  • the QRS complex is above the isoelectric line in Lead V6 i.e. V6 will have a R(s) shape.
  • between V2 and V5 the amplitude of the R upstroke becomes greater than the amplitude of the S downstroke i.e R > S. This is called the transition (or transition zone).

The alterations in the QRS configuration are termed R-wave progression.

Figure 2: Precordial leads in a normal ECG. The transition zone is between Lead V3 and Lead V4

The transition usually occurs in Lead V3 in a normal ECG, but the location of the transition can be altered by changes in the placement of the precordial leads.

When the transition happens in lead V1 or V2 the complexes in Leads V1/V2 to V6 have a Rs configuration.

Figure 3: Precordial leads in right bundle branch block. The bundle branch block has produced tall R waves in V1-V3, and there is no transition zone. The presence of a upright (R) wave in all the precordial leads is called positive concordance.

When the transition zone shifts to Lead V5 or V6 the complexes in Leads V1 to V5/V6 have a rS configuration i.e. the complexes in Leads V1 to V5/V6 have a small amplitude "r" wave and a deep S wave. This is sometimes called "poor R wave progression".

The precordial complexes in this case have prominent S waves, with Leads V1 to V4 having a rS configuration and Leads V5 to V6 having a RS configuration (Figure 1). The transition zone is in Lead V6.

Here are some parting words from Chou’s Electrocardiography in Clinical Practice (Fifth Edition, 2001 Saunders) on poor R wave progression: “The widely used term “poor R wave progression” is not helpful. In many cases the abnormally low R amplitude extending from the right into the mid or left precordial leads indicates myocardial infarction of the anterior wall. Such a pattern occurs also in the presence of left ventricular hypertrophy and in normal subjects without cardiac or pulmonary disease. It may be caused by a shift of the transitional zone to the left or by an atypical (abnormally high) placement of the mid-precordial chest electrodes. For this reason it is advisable to report the most likely cause of “poor R wave progression” in each case.”

+ Does this ECG have changes due to ventricular hypertrophy?

There are different ECG scoring methods for left ventricular hypertrophy. The following (based on voltage criteria derived by Sokolow and Lyon) are from Chou’s Electrocardiography in Clinical Practice Sixth Edition 2008 Saunders Elsevier):

Limb Leads

  1. R wave in Lead I + S wave in Lead III > 2.5 mV (> 25 mm)
  2. R wave in aVL > 1.1 mV (> 11 mm)
  3. R wave in aVF > 2.0 mV (> 20 mm)
  4. S wave in aVR > 1.4 mV (> 14 mm)

Precordial Leads

  1. R wave in V5 or V6 > 2.6 mV (> 26 mm)
  2. R wave in V6 + S wave in V1 > 3.5 mV (> 35 mm)
  3. Largest R wave and largest S wave in the precordial leads > 4.5 mV (> 45 mm)

The ECG in figure 1 does not have left ventricular hypertrophy according to the Sokolow-Lyon criteria.

Another method for evaluating ECG’s for left ventricular hypertrophy is the point scoring system of Romhilt and Estes (Romhilt DW, Estes EH. A point-score system for the ECG diagnosis of left ventricular hypertrophy. Am Heart J 1968; 75:752-758). This is more cumbersome than the Sokolow-Lyon criteria (or other voltage based criteria) but has greater sensitivity and specificity (Buchner S, Kurt Debl K, Haimerl J et al. Electrocardiographic diagnosis of left ventricular hypertrophy in aortic valve disease: evaluation of ECG criteria by cardiovascular magnetic resonance. Journal of Cardiovascular Magnetic Resonance 2009, 11:18 doi:10.1186/1532-429X-11-18)

Figure 4: Romhilt & Estes point scoring system for left ventricular hypertrophy

Application of the Romhilt & Estes point scoring system

  • The amplitude of the S wave in Lead V2 - using the second QRS complex for this measurement - is 30 mm (the amplitude of the other complexes in Lead V2 is slightly less than this): 3 points
  • Left axis deviation of -33 degrees: 2 points
  • The QRS width is 116 msec (computer measurement): 1 point

The total-point score in this case is 6, suggesting left ventricular hypertrophy.

+ What is an Intrinsicoid Deflection? (Geek alert).

The Romhilt & Estes point scoring system introduces the term "intrinsicoid deflection". This is an ECG "unknown unknown", to quote Donald Rumsfeld who in 2002 said "There are things we know that we know. There are known unknowns. That is to say there are things that we now know we don't know. But there are also unknown unknowns. There are things we do not know we don't know".

The term intrinsic deflection was introduced in 1914 by Thomas Lewis. Consider a electrode that is on the surface of the heart; the electrode is attached to a recording device. As a depolarization wave approaches the electrode an upward deflection is inscribed by the recording device. When the depolarization wave passes under the electrode a sharp downward defection is recorded; this is called the intrinsic deflection. This term has been replaced by “intrinsicoid deflection”, which indicates that the recording electrodes are on the body surface and record variations in the electric field surrounding the heart rather than the potential difference at the heart’s surface. The intrinsicoid interval is not routinely measured, so in most cases it can remain a "unknown unknown".

The onset of a intrinsicoid deflection in the precordial leads corresponds to the peak of the (tallest) R wave, or the nadir of the (deepest) S wave. The time to the (start of the) intrinsicoid deflection can be measured; the upper limit of normal in the right precordial leads is 0.035 seconds and in the left precordial leads it is 0.045 seconds.

Figure 5: Measurement of the interval to the onset of the intrinsicoid deflection in Lead V2 and Lead V6. The interval is slightly prolonged in V2 and is normal in V6

The time interval to the onset of the intrinsicoid deflection is increased in bundle branch block and in ventricular hypertrophy.

Figure 6: Precordial leads in right bundle branch block, with a prolonged interval to the intrinsicoid deflection in Lead V1 and a normal interval in Lead V6

Figure 7: Time to onset of intrinsicoid interval in Lead V6 in two patients. The interval is normal in A-V6, and in the second patient with left ventricular hypertrophyit is at the upper limit of normal in one tracing (B-V5) and prolonged in another (B-V6)

Summary Learning Points

  • Atrial fibrillation associated with a cerebral embolus
  • R wave progression and transition zone in the precordial leads
  • ECG criteria for assessment of left ventricular hypertrophy
  • Left ventricular hypertrophy (based on the Romhilt_Estes point scoring system)
  • Concept of intrinsicoid deflection 

 

Additional Historical Comments

25th April 1912

The patient is 103 years old, having been born  on 25th April 1912. The birth date is a poignant one for Australians; it was exactly 3 years before the 25th April 1915 landing of Commonwealth troops at Anzac Cove, as part of the Gallipoli campaign.

The Gallipoli campaign was an attack by England and France against the Ottoman Empire during World War I. Soldiers from Australia, New Zealand, India and Canada helped the forces from the United Kingdom, while France's force included troops from French West Africa.

The aim of the Gallipoli landing was to capture the heights overlooking the Dardanelles and break the Ottoman lines of communication to the south. Despite terrible casualties on both sides, the Ottomans were unable to drive the attacking force back into the sea, while the attackers made little headway against the Ottomans. On the first day of the landings, roughly two thirds of the Ottoman troops defending the heights were Arabs, mainly from Syria.

 

1912: That was the year that was..

Some of the events during 1912 were:

  • Einthoven addressed the Chelsea Clinical Society in London and described an equilateral triangle formed by his standard leads I, II and III, later called 'Einthoven's triangle'. This was the first reference in an English article to the abbreviation 'EKG'. Einthoven W. The different forms of the human electrocardiogram and their signification. Lancet 1912(1):853-861
  • January 1912: Thomas Lewis published a paper detailing his clinical and electrocardiographic observations on atrial fibrillation. Lewis T.  A lecture on the evidences of auricular fibrillation, treated historically. Br Med J 1912; 1:57-60.
  • January 1912: British explorer Robert Falcon Scott and his expedition reached the South Pole only to find that Norwegian explorer Roald Amundsen had preceded them by just over a month. Scott and his companions died at the end of March
  • March 1912: Captain Albert Berry performed first parachute jump from an airplane.
  • 14th April 1912: RMS Titanic collided with an iceberg and sank 
  •  May 1912: Royal Flying Corps was established in England
  •  June 1912: US army tested the first machine gun mounted on a plane
  •  July 1912: Australia sent women to the Olympic Games for the first time
  •  August 1912: Edgar Rice Burroughs' book Tarzan was published
  •  December 1912: Bust of Queen Nefertete was found in Egypt

 

1911: "The little strips of paper..."

In 1911 Thomas Lewis (Lecturer in Cardiac Pathology, University College Hospital Medical School; Physician to Out-Patients, City of London Hospital for Diseases of the Chest) published a textbook  called "The Mechanism of the Heart Beat" (London: Shaw & Sons) and dedicated  it to James Mackenzie and Willem Einthoven

Extracts from the preface to "The Mechanism of the Heart Beat":

  • Our knowledge of the clinical pathology of the heart has advanced with such rapidity during the last decade, and the subject as a whole has become so technical, that at the present time it is difficult or well-nigh impossible for the general reader to keep pace with its progress.
  • The nature of the subject necessitates abundant reference to graphic records, of which I have endeavoured to give examples in which the analysis will be unquestioned by those familiar with the methods. For the sake of simplicity, the text deals with electrocardiographic curves obtained by means of a single and customary lead.
  • Of the immediate value of graphic methods in the practice of medicine, it is my desire to speak but briefly. They have placed the entire question of irregular or disordered mechanism of the human heart upon a rational basis, so giving to the physician the confidence of real knowledge; .......... they have potentially abolished the promiscuous exhibition of cardiac poisons ..... and have clearly shown the lines which their administration should follow.
  • The records in themselves constitute the most exact signs of cardiac affections which we possess. The little strips of paper, imprinted by the disease itself, form permanent and unquestionable testimony of events which have occurred, and may be placed in the balance, without disquietude, while experiences of a more subjective kind fill the opposing scale.

 

Einthoven's String Galvanometer: 1911

Figure 8: Einthoven's string galvanometer

The shape and parts of the string galvanometer as illustrated in "The Mechanism of the Heart Beat". This devices looks like something from a Steam Punk graphic novel.

 

The Cause and Conduction of the Heart Beat: 1911

"...... the reader will find no reference ... to the still controversial questions of the "neurogenic" or "myogenic" origin and transmission of the heart beat.

......the heart beat may be shown to arise in this [sinoatrial] node, and the contraction travels from it over the walls of the auricle and reaches the structures described in the following paragraphs". From "The Mechanism of the Heart Beat"

Figure 9: The atrioventricular node, the bundle of His and the right bundle branch are shown in a dissection of a human heart. This illustration is from "The Mechanism of the Heart Beat".

Figure 10: The left bundle branch and its divisions are shown in a dissection of a walrus heart. This illustration is from "The Mechanism of the Heart Beat".

Final Comment: The patient's age and his underlying cardiac problem of atrial fibrillation are a direct link to the dawn of modern electrocardiography.