MEDICINES FOR HEART – PART 2

THE CALCIUM CHANNEL BLOCKERS

This is yet another medicine which is used to decrease the oxygen requirement of the heart. Let us see how it works. The muscle cells of the heart and blood vessels have channels through which calcium ions leak in. This leakage of calcium is necessary for the muscles to contract and when they contract it leads to contraction of heart as a whole or constriction (narrowing) of blood vessels (arteries).

If somehow this leakage of calcium is stopped or slowed then the arteries will relax. The relaxed vessels allow the blood to flow more easily through them; thereby the requirement of heart is decreased. Also the blood pressure is lowered.

Smoking interferes with calcium channel blockers and decreases their effect.

OTHER USES                                                   

They have also been used extensively in the treatment of increased blood pressure, Arrhythmias (irregular heart beat). They have also been tried in premature labour, and nocturnal (night) leg cramps.

THE ACE-INHIBITORS-HOW DO THEY DECREASE THE LOAD ON THE HEART?

This is yet another group of medicines which decreases the requirement of the heart by decreasing the amount of load on the heart.

To understand them let us expand the term ACE first. It stands for ANGIOTENSIN CONVERTING ENZYME. Angiotensin is made up of 2 words Angio (blood vessels) and Tensin (pressure). This is a substance which constricts the blood vessels and thus increases the blood pressure. Increased blood pressure means increased work load on heart. If production of Angiotensin is blocked, then it will prevent the rise in blood pressure. ACE-inhibitor is a chemical which blocks the action of the enzyme which forms Angiotensin from its raw material (Angiotensinogen).

When arteries are relaxed they allow the blood to flow easily and also when veins are relaxed they hold more blood to themselves rather than carrying it to the heart, thus reducing the load on the heart and thereby reducing the requirement of the heart.

ACE-inhibitors also lower the amount of water and salt in body, which also helps to lower the blood pressure.

They can interact with Diuretics and Alcohol. One of the troubling side effects of ACE Inhibitor is an irritant dry cough , which if it becomes intolerable needs to be changed. But this occurs in only a few.

They have also been shown to have a protective effect on the heart muscles and limit the damage to the heart muscles after a heart attack.

Other Uses: They have been extensively to prevent certain kinds of damage to the kidneys, which is prevalent in diabetics called as Diabetic Nephropathy.

There is another sister group of ACE inhibitors called as Angiotensin II receptor blockers which block the action of Angiotensin, the chemical responsible for constriction of blood vessels. It has been used in place of ACE inhibitors when they lead to a dry irritant cough in a few patients.

DIURETICS – HOW DO THEY HELP?

Also sometimes referred to as “water pills”, this is a group of medicine which leads to increased passage of urine and thus lowers the total volume of circulating blood inside the body. This lowers the load which heart has to handle and make things easy for the heart i.e. decrease the requirement (work load) of the heart.

They are very helpful when the pumping power of the heart has decreased.

Other Uses: In high blood pressure or edema (water retention) as in kidney disease or tuberculosis etc.

They interact with Digitalis, and antidepressants and increase levels of uric acid in the blood.

                                                                                                                                                               

ASPIRIN, THE BLOOD THINNER – HOW DOES IT HELP?

How, does a heart attack take place?

Whenever the internal membrane covering the blockage ruptures (due to increasing size of blockage), it leads to a series of chemical reactions which finally leads to clotting of blood inside the blood tube. This lead to obstructing the path completely i.e. cutting of blood supply totally (100% blockage).

This, if allowed to persist for a longer duration, can lead to a permanent damage to heart muscles, leading to decreased pumping capacity of the heart.

If somehow, this tendency of blood clotting is decreased then it will save so many lives and this is exactly what is being done by the blood thinners. They decrease the blood’s ability to clot. Actually inside the blood vessels there are always a few reactions going on which lead to clotting of blood and to counter them, there are some reactions which dissolve different mechanisms.

1.       To inhibit reactions which lead to clotting.

2.       To promote reactions which dissolve the clot.

Mechanism no. 2 has been explained in an entirely separate topic on the next page.

In mechanism no. 1 platelets, a type of blood cell, stick to each other and the damaged blood vessel (ruptured membrane). This initiates the clotting of blood. “Aggregation” of platelets can be inhibited by the age old aspirin/disprin in low doses. That is why they are also used in the treatment of TIA (mini stroke) 

They can interact with antidepressants, sleeping pills and certain antibiotics.

This group of medicines should be avoided in case of bleeding stomach ulcers, bleeding piles, non healing ulcers. They can themselves lead to acidity or gas formation which can be countered by medicines in a few cases.

Hope you liked this article!

This article is written by Dr. Bimal Chajjer (India’s Best Heart Doctor)

To read part 1 of Medicines for Heart, please click on the link.