What is the aortic valve ?
Aortic valve is a valve between the heart and the blood going into the rest of the body. This valve faces high pressure oxygenated blood being ejected into the body. The pressure is equal to the blood pressure (upper no., systolic blood pressure). The lower number is affected significantly by several things including how well this valve closes. If the aortic valve leaks, the blood pressure (lower number, diastolic) will be lower.
What is the normal aortic valve like ?
A valve is made of cusps which are like petals (usually as soft as rose petals). There are 3 such leaflets or cusps in a normal valve. Opening of the valve allows blood to flow ahead and closing prevents blood from leaking back into the pump.
What is a bicuspid valve ?
About 1% of the population has a bicuspid (2 cusps instead of 3) valve. A bicuspid valve is more likely to narrow down at the junction points where the cusps meet at the corners (called commisures). Usually the fusion at these corners causes narrowed opening (called Doming) of the valve.
When does an aortic valve need to be ballooned ?
When the stenosis gets to be severe, the valve needs ballooning. The severity of the narrowing is decided by the pressure difference across the valve. Narrower the valve, more the pressure difference; when the peak pressure (peak gradient ) crosses 60 mmHg, the valve needs to be ballooned. This number may vary between centers. Your interventionist will advise you when the intervention is needed.
How is the ballooning done?
The principle of ballooning remains the same as mentioned under FAQ. There are significant differences between balloon dilatation of the aortic and the pulmonary valve. In Pulmonary valve dilatation, the valve is crossed from below the valve, and the wire over which the balloon will be taken, has to move along the flow of the blood. With aortic valve, usually, valve is not crossed from below (that just how the arterial entry is made, it does not allow entry into the ventricle); but, it is crossed from above the valve against the flow of blood. Infact when the valve is severely narrowed, a jet of blood with a high velocity comes out of the valves tiny opening; this makes the procedure more challenging.
Is there a possibility when the valve cannot be crossed from above (retrograde-referring to the flow against the blood)?
Yes, there is a good possibility that the valve cannot be crossed if it is too narrow.
How is the procedure performed if the valve cannot be crossed retrogradely?
The valve then has to be crossed from below. To do that, one has to enter the ventricle and the only other way (other than across the aortic valve) to enter the ventricle is from the atrium. This would mean across the wall (septum separating the atria. If there is a tiny (normal) hole which allows entry, it can be done through that, otherwise using a transeptal needle a hole would need to be made to allow the access.
How is a balloon selected size selected ?
Balloon size is decided by and limited to the annulus (ring size on which the valve is mounted). In pulmonary valve, one is allowed to use a balloon upto 120% or even 140% of the annulus size. This is because the pulmonary valve leakage is well tolerated as compared to aortic.
In the aortic valve, dilating it even 110% of the annulus would result in valve leak which over decades may cause more harm and may not be tolerated. So, as a thumb rule, the ballooning is started from 80 or 90% of the annulus size and increased to but never more than 100%.
What are the side effects of aortic valve balloon dilatation ?
One of the major issues with aortic ballooning is that the valve leaks after ballooning. If the valve leaks more than mild, it is likely the patient will end up with surgery after several years or decades. Rarely, extremely rarely, a valve may tear to a point that it leaks completely during the ballooning and the patients blood pressure falls too much.
In addition, the artery which has been entered is the sole supply of blood to the lower limb on the side it has been entered. This can actually try and close down after the procedure has been done and that can cause risk to the limbs viability. This is important.