Download File - Developing Anaesthesia

TRIFASCICULAR HEART BLOCK
Extinct Auroch, Cave Painting from the Hall of the Bulls, iron and manganese oxides and
charcoal; Lascaux Caves Bordeaux France; Ice Age: Magdalenian period, c. 17,000 BC. Is this
the origin of the Constellation of Taurus?
The origin of human art, in terms of the human life span, is very ancient, but in terms of
geological history it originated very suddenly in the blink of a geological eye, in the period of the
great Ice Age around 30-40 thousand years ago. In the geological terms of deep time, the events
of the appearance of cave art and the footprint of Neil Armstrong appearing on the moon are
virtually part of the same event! Just as the Cambrian fossil record of macroscopic life opens
very suddenly, so too does the recorded history of Homo Sapiens. This suddenness of
appearance strongly suggests a revolutionary change in the evolutionary history of humanity of
a most profound nature. So revolutionary was this change that anthropologists, archeologists,
and evolutionary biologists think of this event as, in Jared Diamond’s term, “the great leap
forward”.
Why was the sudden appearance of cave art so revolutionary? Earlier than “the great leap
forward”, homo genus made artifacts had hardly changed for one million years! Then all of a
sudden the most intricate and brilliant art appears on the walls of caves from Europe to Arnhem
land in Australia. Homo sapiens anatomically indistinguishable from modern day humans go
back to around 100,000 years ago, so that humans of 40,000 years ago, would be pretty much
the same in regards to looks as modern day humans. There must have some new change within
the internal wiring of the brain which suddenly put Homo Sapiens above every other animal on
the planet. Just exactly what this change was, is one of the great holy grails of those who
investigate the evolutionary history of humanity. At present the nature of the change is unknown.
Many anthropologists have surmised that it was the development of language which ignited the
“great leap forward”. The human brain at this time had the potential - but potential only - for
this capacity. Something happened around 40,000 years ago that allowed Homo Sapiens to fully
utilize this capacity and it sparked a cultural event that streaked across the globe like a lightning
bolt. Aurochs and Irish Elk are depicted in caves in Europe, Thylacines are depicted in caves in
Arnhem land and in the next moment Aurochs roaming Ice Age plains evolve into to the “Last
Judgment” of the Sistine Chappell.
And yet many, preeminent and brilliant evolutionary scientists such as Richard Dawkins and
linguists such as Steven Pinker believe that the origin of human language is probably much older
than 40,000 years. So if not language itself, what exactly was it that sparked, in the words of
Richard Dawkins, the “Upper Paleolithic flowering of human consciousness”. One theory holds
that although the full capacity for language already existed at this point in time, it reached a
critical threshold that allowed the expression of complex symbolic ideas. Perhaps this threshold
that was crossed 40,000 years ago, and once crossed allowed the full potential of the human
mind to be communicated from one individual to another.
Whilst we can establish the origins of art, at around 40,000 years ago, the exact meaning of
what this cave art was meant to express is tantalizingly uncertain. The human written record
opens about 5,000 years ago and so the meanings of most cave art is lost to us in the mists of
pre-history. Asides from the sheer aesthetic beauty of some of the most stunning examples of
cave art, found for example at the Altamira caves in Spain and the Lascaux caves in France, the
art also provides us with unparalleled science in the form of visual images of a lost prehistoric
world. As Stephen Jay Gould pointed out in his essay “A Lesson from the Old Masters”, we have
a direct visual record of some animals such as the Irish Elk, just as they were in real life.
Features such as fur markings and soft tissue humps are shown to us in prehistoric photographs,
that give us information about these magnificent animals that would have been forever hidden
from us if all we had were their fossilized bones. Gould wrote in tribute to an anonymous
prehistoric painter of the Elk, “...You’re a better man than I am...For I can only report and
interpret, but you salvaged (for us) a real and true item of Earthly beauty...”
But apart from the aesthetic beauty and scientific value of the images, the art has another value,
a cryptic glimpse into the minds of our distant ancestors at a crucial time of our evolutionary
history. Although ultimately we can never know the true meaning of many of the cave images,
Anthropologists who study this ancient art can make quite reasonable guesses about their
possible purposes or meanings. Most interpretations believe that the art most often represents a
belief in the magical powers of the images. They show an intimate relationship with the land and
environment in which the artists lived. They struggled to understand the forces of nature around
them and the images they produced were thought to hold supernatural powers that would protect
them against the terrifying forces of nature and ensure the precarious food supply of their hunter
gather existence. Some also perhaps relate to fertility. Perhaps cave art represents the very
earliest forms of organized belief systems that would evolve into religions.
Whilst a belief in the magical power of images being able to influence survival in the form of
enhanced fertility, protection against the elements and the terrifying predators of the Ice Age,
and the securing of uncertain food supplies, are all one aspect of interpretation, another more
sophisticated one has been put forward by Dr Michael Rappenglueck of the University of
Munich. He believes that at least in regard to the cave art seen at the most famous site of all at
Lascaux in France, some of the images are in fact Ice Age star maps, humanity’s first attempt to
understand the cosmos! Humanity has always had a deep respect for and interest in the cosmos.
The earliest civilizations all had depictions of Constellations in some form. We do not know the
origin of the ancient Constellations, but Rappenglueck believes that a series of cave drawings at
Lascaux may represent the very earliest depiction of the Constellation of Taurus, the Bull. At
first this seems like a quite long bow to pull, but the more you understand the distinct pattern of
this Constellation and the more you study the depiction of the Auroch, (the evolutionary ancestor
of the modern day Bull), the more interesting his theory becomes. The open star cluster of the
Hyades forms a distinctive V- shape, around the bright star of Aldebaran, (or Alpha Tauri). The
eye of the Auroch shows this pattern. To the right and above this is a group of dots that bear a
striking relationship to the almost exact relative position of the most famous open star cluster of
all, the Pleiades. Any modern day Astronomer instantly recognizes this pattern and when we see
this pattern reproduced within the Auroch the argument that this could be origin of humanity’s
idea of the Constellation of Taurus, becomes intensely compelling. The Constellation of Taurus
is very ancient indeed, perhaps predating the historical record by over 10 millennia. If
Rappenglueck’s theory is correct it shows us that the mind of Homo Sapiens, 17,500 years ago
was probably fully modern, the only thing separating modern humans from the those of the
Upper Paleolithic being the benefit of the accumulated knowledge of the whole of the species
over the subsequent millennia.
A fundamental ability of our species, and one that separates us from all other species is the
unparalleled ability to think - and communicate - in symbolic terms, as Dawkins puts it - the
difference between an earlier ability to merely “observe that watering hole”, to one of “what if a
watering hole lies over the ridge of that hill”. Upper Paleolithic man looked up at the night sky
and saw in it a place where the gods dwelt. The most important aspects of their lives were
represented in the stars, one of which represented a major source of food for a hunter gatherer
society, the giant Auroch, essential to their survival. Their ability to recognize patterns in
symbolic terms led them to recognize in the Hyades and Pleiades star clusters, an animal they
revered, and recognized as crucial to their existence in physical terms, but perhaps also in
spiritual terms as well.
Over 40 millennia on from the “great leap forward” we use our ability to recognize our mental
constructs or symbols in the most sophisticated ways - amoung them the pattern of squiggly lines
we see on the ECG recording of the heart. We recognize typical patterns that alert us to
underlying cardiac pathologies, such as the trifascicular heart block.
TRIFASCICULAR HEART BLOCK
Introduction
Trifascicular Heart Block is when there is a block (of some degree) in all three fascicles of the
conducting tissue of the heart.
If there is complete block in all three fascicles, this results in complete heart block.
Trifascicular Block may take the following forms:
●
RBBB and LAHB and 1st Degree Heart Block
●
RBBB and LPHB and 1st Degree Heart Block
●
LBBB and 1st Degree Heart Block
●
Alternating RBBB and LBBB
Management of the patient who presents with trifascicular block will depend on:
●
The underlying cause
●
The nature of the clinical setting in which the patient presented.
●
If the changes are acute or chronic
Anatomy
Pathophysiology
Causes:
Causes may include:
1.
IHD
2.
Acute Coronary Syndrome
3.
Hyperkalemia
4.
Drug toxicity:
●
Digoxin, beta blockers, calcium channel blockers, sodium channel blockers.
5.
Hypertensive heart disease.
6.
Primary degenerative conductive tissue diseases.
●
Lenegre’s (or Lev’s) disease.
Clinical assessment
The nature of the presentation will determine to a large degree the management of the patient.
Important features to note include:
●
Syncopal episodes:
♥
Episodes of collapse or near collapse, may indicate progression to intermittent
complete heart block.
●
Chest pain:
●
●
The presence of chest pain may indicate an acute coronary syndrome, with
the potential to progression to complete heart block.
Medications:
●
All patients should have their medications reviewed particularly in respect to
those that may predispose to conduction delays.
Investigations
Blood tests:
1
FBE
2
U&Es/ glucose
●
Urgent potassium level.
3.
Magnesium and Calcium levels
4
Troponin level
5.
Digoxin level
ECG features:
Tri- fascicular Block may take the following forms:
●
RBBB and LAHB and 1st Degree Heart Block
●
RBBB and LPHB and 1st Degree Heart Block
●
LBBB and 1st Degree Heart Block
●
Alternating RBBB and LBBB
♥
In this scenario there are dynamic ECG changes, one moment there is a
the next a RBBB.
LBBB,
Above: Typical ECG appearance of a trifascicular block in a 76 year old male, who presented
with syncope. There is a prolonged P-R interval, LAD, and a RBBB pattern in the chest leads.
Above: Another pattern of trifascicular block, prolonged; P-R interval with a LBBB pattern in
the chest leads.
When patients present with the combination of bifascicular block plus 1st (or 2nd degree) AV
block it is usually impossible to tell from the ECG whether the AV block is occurring at the level
of the remaining fascicle (a true trifascicular block) or at the level of the AV node (i.e. not
technically a trifascicular block). For the purposes of management in the ED, however this point
is purely academic.
Management
Although these blocks do indicate advanced organic heart disease, the risk of sudden progression
to complete heart block and sudden death rather surprisingly is not high when they are found as
incidental findings.
However the margin for error is very small and when there is an added pathology that may affect
cardiac conduction, the risk may become much greater.
Management of patient with trifascicular block will therefore depend on:
●
The underlying cause
●
The nature of the clinical setting in which the patient presented.
●
If the changes are acute or chronic
Disposition
Each case needs to be judged on its own merits, but in general terms, patients who:
●
Are symptomatic
●
Have an identifiable and readily reversible cause
●
Have acute onset ECG changes
●
Have an aggravating pathology
should be admitted to a CCU and referred to cardiology
These patients may require temporary or permanent pacemaker placement.
Photograph of main part of the Constellation of Taurus, (from Northern Hemisphere
perspective). The eye of the Auroch (or bull) is the prominent red giant star Aldebaran, part of
the V-shaped Hyades open cluster. To the right and above this cluster is the most famous open
star cluster of all, the Pleiades, or the “Seven Sisters”.
References
1.
Chan et al. “ECG in Emergency Medicine and Acute Care”, Elsevier Mosby, 2005.
Dr J.Hayes
August 2012