Heart Surgery Centre Most
patients have symptoms prior to an actual heart attack - generally a
"tightness" behind the breastbone, which generally is caused by an
increase in heart rate. The coronary arteries fill in between heart beats
therefore anything which increases your heart rate will reduce the time your
coronary arteries have to provide blood flow to the heart muscle- the
myocardium. Once the heart muscle is deprived of oxygen it becomes irritable
leading to palpitations and, if not relieved, death of the muscle.
Surrounding the dead muscle is a variable sized area of
heart muscle at risk of dying because of inadequate oxygen supply - this
condition is known as myocardial ischaemia.
The heart rate is under the control of the autonomic nervous
systems, which, in the case of the heart, is driven by adrenaline the so-called
"flight or fight" hormone.
Adrenaline acts at various sites of the body
- On the sinus node in the heart which controls rate to
increase heart rate
- On the bronchial tubes in the lung to cause them to dilate
allowing greater flow of air into the lungs
- On the small arteries in the skin and gut to constrict
(narrow) reducing blood flow to these areas and making more blood available to
the muscles- to fight or fly
- Increases the blood sugar by increasing breakdown of
glycogen to glucose, important food for the muscles to contract better.
Whilst increased adrenaline production is common with
exercise it also occurs in states of shock, fear, or anger producing gooseflesh
and sweating (remember the first time you saw the shower scene in the Hitchcock
Movie Psycho).
As well as increasing the heart rate adrenaline may cause
cardiac irregularity, increased blood pressure, or palpitations. It is this
irregularity which may lead the heart to chaotic beats and finally fibrillation
and death.
This is the first symptom of a heart attack in about 20% of
people - sudden death - the victim just collapses to the ground. Whilst he may
gasp a few breaths he has no cardiac output- no blood is leaving his heart- he
is pulseless.
This terminal condition (ventricular fibrillation) is very
easily treated by first aid measures and cardiac shock- termed defibrillation.
Nowadays many areas which have high populations (or as in aeroplanes, confined
areas) have people friendly defibrillators available which only shock patients
who have rhythms which are treatable by shock. These machines have easy
instructions and any bystander who can read can apply the electrodes and save
the patient's life.
Often people wrongly refer to this cause of death as a
massive heart attack- it takes some time (often up to an hour) to die from a
massive heart attack. In this case the heart attack causes such significant
damage to the main ventricle of the heart as to reduce blood pressure to
critically low levels and death results.
Cause of Heart Attacks
The pathological cause of heart attacks is a clot of blood,
which forms over an area on the lining of a coronary artery which, is
"ready" for a clot to form - this area is termed a vulnerable plaque.
It was previously thought that clots developed on the lining
of arterial walls that had become calcified and thickened - it is now known
that rarely are these areas the sites of clots.
Calcification and deposition of cholesterol within the
arterial wall reduces the lumen size and therefore flow of blood through this
section of the artery is likewise reduced. This reduced flow may be sufficient
to provide enough oxygen to the heart muscle during rest or light work. However
once the heart is required to work harder the blood flow is insufficient to provide
enough oxygen to the heart muscle and symptoms follow.
Angina- Pectoris and Decubitus
When the heart muscle receives insufficient oxygen it
produces lactic and pyruvic acids and these produces the tightness in the chest
known as angina the type of angina which occurs during exercise is termed
Angina Pectoris.
The obvious treatment is to reduce the heart work by ceasing
whatever activity has caused the heart rate to rise.
Whilst typically angina pectoris occurs as tightness in the
chest it may move up into the throat or down one or both arms. Occasionally it
may only occur in the teeth or in the back between the shoulder blades.
Patients may describe it as a "weight on my chest" or
"constriction". Occasionally the only symptom may be acute
breathlessness.
The cardinal feature is the relation to increased heart work
and its relief by stopping activity. In addition one should use a trintrin
preparation. If pain is present use another dose after five minutes or so and
repeat twice.
The treatment of angina is beyond the scope of this article
however drugs which reduce the work the heart has to do (like putting a
governor on your heart) are most effective and as they block the action of
adrenaline are termed betablockers.
Drugs, which dilate the coronary arteries (trintrins), are
also helpful. These come as patches, tablets for sucking, sprays for inhalation
or as solutions for intravenous use in hospital. These should be used only when
the tightness is present and not when you feel giddy or weak as they will
reduce blood pressure and may cause you to faint. These also dilate all
arteries and therefore may cause headache.
Trintrins are particularly dangerous when used in
conjunction with some of the newer drugs for erectile dysfunction eg viagra and
these must not be used within 24 hours of each other
Spasm of the coronary arteries may also cause reduction in
blood flow to the heart. Everyone has some degree of spasm within their bodies
and angina is generally due to mixture of both atheroma and spasm.
However angina, which occurs at rest particularly at night
around 2.0am waking the patient, is due to vasospasm and is termed angina
decubitus.
The symptoms are similar to angina pectoris but in this case
it is spasm of the artery and the treatment is not betablockade therapy but a
group of drugs called calcium antagonists. These drugs relieve the spasm of the
artery.
Unstable Angina
Should the pain be prolonged and not relieved by rest and trintrin
therapy the term unstable angina is used.
In this case the pain is more severe and often associated
with an increase in sympathetic overactivity. Symptoms such as sweating,
nausea, vomiting, palpitations, faintness or a feeling of wanting to faint (presyncope),
or even syncope are common.
This is a medical emergency and an ambulance should be
called without delay, as it is impossible to differentiate unstable angina from
a heart attack without electrocardiograph and blood studies.
If you believe that you may have this syndrome whilst
waiting for the ambulance chew a whole aspirin tablet.
This condition is generally associated with a clot being
formed within one of the main coronary arteries and hospitalisation is
necessary so that a definitive diagnosis may be made and urgent treatment to
protect the heart from damage instituted.
Differential Diagnosis
Angina is often confused with indigestion and many patients
rationalise that whilst they may consider the pain could be angina it
"simply cannot happen to me' and it is probably only indigestion or just
wind.
One eminent Professor of Cardiology writing in one of the
journals described how he waited for eighteen hours before going to Hospital as
he thought it " was simply bad indigestion". He finished up with
bypass surgery!
Indigestion is generally in the pit of the stomach burning
in nature, often relieved by belching or by drinking a glass of milk or alkali.
It has no relation to exercise, rarely referred to the arms or back, and may
come up into throat as a burning sensation. Trintrins have no effect.
Hiatus hernia or oesophageal reflux may mimic vasospastic
angina as they both occur at night when the patient is prone.
Silent Ischaemia
Some patients, generally those with high pain thresholds,
may have myocardial ischaemia which is entirely asymptomatic.
Rarely patients may be found with classical
electrocardiographic changes of a heart attack without remembering anything
remotely like the symptoms, which are noted above.
On a treadmill exercise test these patients may develop
changes on their cardiograph, which are diagnostic of myocardial ischaemia.
They may develop high blood pressure or more dangerous, a fall in blood
pressure during exercise without any actual pain.
These patients are very difficult to treat, as, unlike most
of us, they do not get chest tightness of pressure before they develop
dangerous cardiac abnormalities. These people require invasive or nuclear
studies to ascertain the workload that causes trouble. They can then be warned
to control their work level.
Heart Failure and Cardiac Irregularities
Patients in their senior years may develop heart failure
without any pain or tightness. The Electrocardiographic changes of a previous
heart attack are found on routine examination.
Atrial fibrillation, a not uncommon rhythm disturbance,
often has myocardial ischaemia as its underlying cause, particularly in the
elderly. This irregularity results in a reduction in the output from the left
ventricle (stroke volume). As blood continues to fill the ventricle from above
the lower output results in the heart becoming distended with blood.
Heart muscle like all other muscles when stretched contracts
with greater strength thereby increasing the output. The patient is unaware of
anything the matter with his heart until an xray is taken showing an enlarged
heart . (Compensated Heart Failure)
However if the reason for the reduction in stroke volume
remains then eventually (when the heart cannot enlarge further) pressure within
the ventricle rises and is passed backwards through the atrium and on into the
pulmonary arterioles causing fluid to move into the air sacs of the lungs and
the patients notices increasing shortness of breath breathlessness.
(Decompensated Heart Failure)
Summary
- Never take chest pain lightly - you might wake up dead!
- Learn a plan and keep to it.
- It is only at an Emergency Centre that you can get
immediate diagnosis.
- Most Heart Attacks who are destined to die do so within
the first few hours. Don't Delay.
- Special Treatment to reduce the residual damage to your
heart is most effective when given early. Particularly within three hours of
the onset of pain.
- You will not be laughed at for going to the Hospital with
indigestion.
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