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Chapter 35 — 6
Aspiration
Aspiration of seawater
– always a possibility in diving – can cause immediate cardiac
effects by a mechanism akin to the diving reflex (see above), It can also be followed by
delayed effects due to hypoxia as the lungs are involved, as in the salt water aspiration
syndrome (see Chapter 26).
Drug Effects
A large variety of drugs have arrhythmic and other effects on the heart, which may
predispose to sudden death. Many can be purchased 'over-the-counter' in pharmacies or
supermarkets. Some are contained in 'cold cures' and 'cough mixtures' and may be
inadvertently used by divers. Some of these drugs include:
• Alcohol
• Nicotine – cigarette smoking
• Caffeine – coffee and tea, stimulant drugs to overcome sleepiness
• "Social" drugs such as cocaine, weight reducing and stimulant drugs such as
amphetamines
• Blood pressure controlling drugs (e.g. calcium channel blockers, beta blockers)
• Drugs used to suppress arrhythmias (e.g. beta blockers)
• Drugs that change electrolyte concentrations in the blood – diuretics and electrolytes
• Sympathomimetic drugs (e.g. decongestants such as pseudoephedrine, anti-asthma
medications such as salbutamol, and some anti-seasick drugs).
• Others that may cause arrhythmias –antidepressants, digoxin, some anti-malarials, local
anaesthetics.
Cardiac Disease
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Coronary artery disease or CAD.
This heart disease (causing narrowing or obstruction of the coronary arteries), while
considered to be a disease of middle and older age, is probably present to some degree even
in some young adults.
It would appear from post-mortem studies done during the Korean and Vietnam wars that
coronary artery disease begins in early adulthood, but usually only causes symptoms and
death from heart attack after 40 years of age. The older the diver, the more significant this is
likely to be. Divers with this disease are more prone to sudden death due to arrhythmias or
myocardial infarction secondary to impaired blood supply to the heart muscle.
!
Coronary artery bypass grafts.
Some blockages of the coronary arteries can be bypassed by blood vessel grafts – usually
using arteries or veins. This reduces cardiac pain and improves cardiac performance but
does not cure the underlying disease, which affects the many coronary arteries not improved
with the by-pass. People with such grafts are still more prone to arrhythmias and cardiac
dysfunction and should not dive, unless proven to be cured. A similar situation exits in
those people who have already suffered a myocardial infarction or "heart attack" and those
needing or possessing pacemakers