Why is Nitroglycerin Contraindicated In Aortic Stenosis?
Patients with Aortic Stenosis (AS) can be effectively treated with nitroglycerine, but it is contraindicated because it carries a risk of hazardous hypotension with it. However, this is quite a traditional and theoretical assumption that nitroglycerine is contraindicated; practically it has shown quite substantial effects in the patients suffering with Aortic Stenosis. Many studies have been conducted to study about the theoretical contraindications of nitroglycerine, but no such evidences or proofs have been found. There was not any precipitation of hypotension in patients with Aortic Stenosis.
What is Aortic Stenosis?
To understand the effect of nitroglycerine on aortic Stenosis, firstly it is important to understand what Aortic Stenosis is and how it is treated. It is a condition in which the aortic valve constricts in size due to which there is insufficient flow of blood from heart to aorta. Aorta is the largest blood vessel of the body and supplies blood to the whole body. If the aortic valve will be defective or won’t function properly, this would exert extra pressure on the heart to pump more blood, ultimately weakening the heart muscles. There is a need of valve replacement for treating the Aortic Stenosis, as only medication cannot treat it completely.
How Does Nitro glycerin works?
If we study the effect of nitroglycerine in terms of cardiac output it can be explained as follows:
Because the aortic valve is constricted in size, the amount of blood pumped from the ventricle is reduced. The drug will reduce the peripheral resistance resulting in the dilating of the vessels and relaxation of the ventricle. The load of the heart remains the same. In the aortic stenosis patients, the after load (pressure of the heart) is not affected by the peripheral resistance, but by the defective valve. This defective valve is not affected by the nitroglycerine. If this is administered in the patient and the vessels are dilated without the changing in the cardiac output, the problem can increase more, the blood can drop and also the capacity to perfuse. This can even cause angina in patients with coronary disease.
What Does A Latest Research Say?
Researchers have conducted a group study on this assumption to check whether the incident of hypotension occurs or not in the patients with severe, average and no aortic Stenosis. Three groups of different age groups were formed. The first group was of the patients with severe AS, the second group was with moderate AS and the third group was of normal people with no AS. All the three groups were administered with nitroglycerine under controlled conditions, from various routes. It was observed that the there was no associated hypotension in the severe and moderate AS patients.
Medication for Aortic Stenosis and Associated Complications
Medicines are given to treat the symptoms and other complications which occur as a result of Aortic Stenosis. Following medications are generally given to control other related complications:
Statins: Previously it was believed that the statins slow down the progression of aortic stenosis, but the latest trials show that there isn’t any such activity; although a considerable reduction in the ischemic cardiovascular proceedings have been observed.
Beta blockers and Calcium Channel blockers: If there is hypertension or angina it has to be treated immediately and aggressively using calcium channel blockers or beta blockers, however the administration of beta-blockers should be done carefully.
Digoxin and Diuretics: They are used in the case of heart failures. If there is no contraindication, careful administration of ACE inhibitors can also be done.
Nitrates: As stated above nitroglycerine is theoretically contraindicated in the patients with aortic Stenosis. The patients are instructed to avoid it because of their dependence on preload and precipitation of sudden hypotension.