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“Bystander Coronary Artery Disease” ...

Medico Legal

“Bystander Coronary Artery Disease” at Post Mortem – What does it Mean?

by Dr Duncan Dymond, MD FRCP FACC FESC

Cardiology experts quite commonly receive instructions to provide an opinion on post mortem findings of narrowed coronary arteries, in individuals who either tragically died in an accident where compensation is sought, or when the patient has died of another medical condition and there is a question of clinical negligence.

It is not at all uncommon for the pathologist at post mortem to find that the coronary arteries, which are the blood vessels which supply the heart muscle with blood are narrowed, and the pathologist will usually give an assessment of how severe the narrowing is and how many arteries are actually involved in the process.

In accidental death, even when liability might be admitted, arguments around quantum will arise if it is felt that the deceased prognosis would have been adversely affected by the presence of narrowed arteries and whether the victim might have died sooner than predicted of natural causes had the accident not occurred.

Similarly, someone dying for example of asbestos related lung disease, will face resistance from the defendants representatives on the basis that death was inevitable from coronary artery disease and that the asbestos related lung disease may be less relevant.

So how accurate is the demonstration of post mortem narrowings by pathologists? Cardiologists are used to judging the severity of narrowed arteries on the basis of coronary angiograms performed during life. The coronary angiogram is a specialised technique where iodine containing contrast (commonly called dye) is injected down the arteries by placing a catheter into the origin of the arteries and filming the passage of the contrast through the coronary circulation. Experienced cardiologists are used to comparing what we believe is a normal segment with a narrowed segment and assigning a percentage stenosis.

In general terms, a 50% stenosis may be deemed significant and a 75% stenosis severe and a 90% or greater stenosis deemed critical.

The same degrees of stenoses are often described by pathologists in a post mortem heart but there is a major difference between the assessment of an artery which has no blood flowing through it and which is collapsed in a deceased patient, and the assessment of that artery during life when the artery is full of blood flowing rapidly into the heart muscle and the arteries are fully distended.

This often causes a conflict between experts and requires some explanation.

The process of “furring up of the arteries” known as atherosclerosis is common in the western world particularly in an aging population. During the Vietnam War, fatty streaks and mild fatty deposits in the arteries of young American casualties were noted even in these young men in their teens and early twenties.

However not every person who demonstrates some degree of abnormality in their arteries is going to actually have either clinical coronary disease or suffer a coronary death. The axiom “it is possible to die with coronary artery disease rather than of it” holds true in many patients. Many people can live to a ripe old age without ever having any clinical evidence of coronary disease even though pathological disease may be noticed at autopsy.

The duty of the cardiologist in these circumstances is to point out and to reference the many studies which have shown the discrepancy between degrees of stenosis at post mortem and what the arteries might have actually looked like during life.

The cardiologist must also put together the individual’s risk profile, for example were they heavy smokers, or diabetic, or suffer with high cholesterol or have a family history of heart disease? The cardiologist may also point out the difficulties in relying too much on a pathologists visual inspection of a collapsed and empty artery and try to extrapolate that into what the artery would have looked like when full of blood during life.

There will often be disagreements between cardiology experts as to the relevance of the post mortem findings. Each expert will try and extrapolate what the post mortem findings might have meant during life although this is a difficult exercise and will vary on a patient by patient basis. ?

Dr Duncan Dymond, MD FRCP FACC FESC Consultant Cardiologist