Sorry for the delay in getting back. I was on call until 0800 this morning then had to get the vaccine, do the week's shopping and sorting out general things before having a snooze. Back up now.
The aim of aeromedical testing is to a) ensure that people meet certain standards (e.g. vision) and b) that their risk of incapacitation is sufficiently small.
The most consistent indicator to judge risk of cardiac events against by far is age. Just age. Cardiac events at a young age are very rare and rise from middle age onwards for ever more:
https://www.ahajournals.org/cms/asset/b ... /24ff6.jpgIn order to stratify the risk of incapacitation due to an acute cardiac event all aviation authorities use a variety of tests and a commonly accepted test for this purpose is the ECG.
a) it is quite sensitive, if someone has coronary artery disease or a cardiac rhythm disorder it is likely to pick it up
b) it is quite specific, if it shows an abnormality it is commonly a fair indication that there is something going on
b) it is easy to apply
c) it is easy to interpret
d) it is cheap
e) there are no side-effects
f) there is no morbidity or mortality associated with the test
Some of the things it isn't
Perfect:
a) there are stories galore that people had a normal ECG and stepped off the couch only to have a fatal event - these of course 'popular' for the drama - in reality these is extremely rare - I must have done a few thousand of them and never ever had it happen even though I have done them on loads of people
b) a fair few people have an abnormal ECG only to be found not to have cardiac disease after a whole host of further involved and costly investigations
c) guarantees - the positive predictive value is not great; a normal ECG is no guarantee there is no cardiac disease or that cardiac disease will not develop.
Taking that into account the ECG can and is used as a screening tool and attached to it are periods of validity,
Remember what I wrote about risk of incapacitation?
Therefore for
a) a LAPL medical no ECG is required to meet the acceptable risk of incapacitation due to a cardiac event for LAPL medical certification.
b) for people who have a Class 2 medical at the initial medical there is no need to repeat that ECG, in the absence of symptoms, before they hit 50.
After that you need an ECG every 2 year.
c) for Class 1 Medical certification - which has a much lower acceptable risk of incapacitation that means they need an ECG after the initial one much more frequently - see the table below:
Does the current system work.
The aviation authorities would argue it does - and I would agree with that, yes there are fatalities associated with cardiac events but they are rare and definitely below the accepted risks.
Could it be improved no doubt but not with the current state of medical science.
Yes you can put everyone on the treadmill but:
It is costly both in time, resource and money; it is also not a perfect test with another number for false positive and false negative tests and there is a definite morbidity and mortality associated with it.
Yes you can let everyone have an angiogram (looking into arteries to see if there is any arteriosclerosis - furring up of the arteries) of the coronary arteries but what goes for the treadmill test goes for the angiogram too.
There are still false negatives and false positives and it is even more resource intensive procedure and now you are looking at a mortality of about 1% and a morbidity of about 1% - these are people who are going to be ill after one or don't get off the table at all. All for a test that is still not perfect.
So how about the 'Gold Standard' the stress echo or stress MRT - there are very few false positives and false negatives - so very much WYSIWYG but you are now looking at £800 to £1200.
There is not the capacity to undertake these at the intervals required to meet the incapacitation prevention numbers and at those prices the number of pilots is going to be vanishingly small.
It is also worth to realise that the opportunity cost at those levels are very much at a level that the money, invested at other areas in aviation would prevent a lot more accidents and fatalities. The whole GA fleet can probably be fitted with the latest kit and TCAS, and free flying to avoid LOC accidents at the value of the budget required.
I hope that goes some way to explain what a non-perfect test can bring to aviation safety.
If there are any comments or questions, feel free to fire away.