Posted in Uncategorized on June 30, 2015 |
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We know right from our pathology days in medical school , Atherosclerosis , the killer human vascular disease has a predilection for branch points. It’s no surprise around 30-40% of coronary stenosis has some degree of involvement of branch points .
PCI essentially involves palliative metal bracketing of this inflammatory cum degenerative process of the vessel wall.Tackling bifurcation lesions (BFL) requires special expertise , hardware and technique as carina and two ostia (In fact three !) are exposed to complex hemo-rheological stress de-nova and more so after the metal invasion.
The complication rate as well as long- term patency are considerably more in BFL than regular lesions. This is why a “4S strategy “ (simple single stent strategy ) is the preferred default strategy in most BFL.
There are about dozen strategies to tame the BFL with stents.One such modality is dedicated BFL stent.Various designs have been proposed in both balloon and self expansion platform.
The ACCSEES is a prototype dedicated BFL stent with DES and a self expanding system
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Degenerative Aortic stenosis occur with either normal or congenitally malformed/ bicuspid valve.This contributes to the major chunk of aortic valve surgeries and interventions (TAVR) in elderly population . The optimal timing of aortic valve replacement in patients with AS is debatable inspite of well formed guidelines.
Three factors determine it .Symptoms , severity of aortic valve narrowing and the tactness of LV function .The last parameter is a tricky one .We used to think in the past , severe LV dysfunction is a contraindication to aortic valve surgery. Now we realise ,however severe the LV dysfunction may be , relieving the obstruction will benefit the patient and the LV function is also likely to improve.
Cardiac physicians face a dilemma when confronted with a patient with low gradient and severe LV dysfunction .In this situation they are advised to do doubtamine stress Echo and watch for the gradient .If the gradient increases that would imply true fixed stenosis . (In pseudo aortic stenosis increased contractility opens the aortic valve and gradient will fall )
While this concept appears simple .There are few important issues that goes unaddressed as we have not yet fully understood the mechanism of LV dysfunction in aortic stenosis .(Link to mechansim of LV dysfunction in Aortic stenosis.)
At what degree of aortic stenosis LV goes down fighting and fail to generate the required gradient ?
Myocardial function and behaviour at times of hemodynamic stress can be highly variable and most of us believe it is determined primarily by the genetic switches of myosin and other contractile elements .This is naturally proven at times of hypertensive left ventricular failure (Only in a fraction of the hypertensive population LV is set to fail when BP acutely raises.)
Considering the complexities in cardiac mechanics , hemodynamics (and not to forget the vast control exhibited by genetic imprints over the hemodynamic behavior of LV) , it seems highly plausible even mild degrees of Aortic stenosis can inflict significant myocardial dysfunction in certain patients . Hence the phenomenon of pseudo aortic stenosis needs further critical analysis If this is proven to be true there could be a realistic indication for aortic valve intervention even in patient with low gradient / true Mild AS with LV dysfunction.
A word of caution is required .Relying too much (Which we often do ) on gradients in the assessment of aortic stenosis has skewed our common sense. Its wiser to have a meaningful look at the valve morphology . A normal appearing valve in 2D can never cause significant stenosis. Pressure recovery phenomenon also is to be given due respect as it over estimates gradient .This will effectively avoid surprises and guilt on table when we find a relatively good looking valve posted for AVR /TAVI
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An attempt is made to look for individual components of cell viability .See the table below. It is a generalized statement for understanding purpose only. Various imaging modalities assess the overall physiology of myocyte function (however they test an individual component of a cell more than the other) We may believe an unit of cell would die in “one-go” at times of ischemic injury.Reality is much complex.There is considerable variation in intracellular survival mechanisms . A cell can die in a regional fashion with residual signs of life scattered across among the different organelles. The quantum of damage to Nucleus /mitochondria may appear determine the recovery . The reverse can also happen .What is the purpose of mitochondria respiring if contractile element is totally damaged ? It becomes a “vegetative cell”. The gross discrepancy we are witnessing in myocyte cell function recovery with reference to both acute and chronic reperfusion is attributable to this gap in our knowledge.
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It is believed (assumed ?), medical science is propelled by constant quest for knowledge and improvement in basic and clinical science that eventually would transform into better patient care and favorably impact global health standards. We know the field of medicine is growing in an unimaginable pace.It’s obvious any growth if uncontrolled or not properly guided is at risk of deviation from the main goal and ultimately turn malignant and destroy the system which it’s supposed to guard.
How many times we realise the current treatment we administer would soon become obsolete and even become dangerous ? What is the point in replacing treatment A by B , and then B is pulled over by C or D and suddenly finding A is better than either C or D (and still we hesitate to fall back on A because its an oldie!)
Still ,this is what we call as practicing ” State of the art medicine” How about a person who defies state of the art , and able to fore- see the futility which is threatening to be the norm in modern medicine. Then,who is really Ignorant ?
I stumbled upon this wonderful writing on this issue by ex BMJ editor by Richard Smith. Mind you , this was published way back in 1992, when the boom of futile ” Human Health shopping” was just about to explode !
Link to The ethics of Ignorance
Don’t get confused .Noble professionals are licensed to practice with whatever is published as science as long as their intentions are deemed to be genuine .Harm arising out of practicing what’s considered best as on today is acceptable in the court of law.
Meanwhile , its a tragic truth, If you do not follow the herd , you are at risk of being punished even for goodness committed by you. Wisdom and conscience can never win a legal battle ! If you have the courage try practice them !
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