MEDICAL INTERVENTIONS OF ANGINA PECTORIS

ANTI ANGINAL DRUGS

Among the three types of angina the classic stable angina which accounts 90% of the incidents and is treatable and reversible.On the other hand the other two types the unsable type,and varient type which are accounting 10% to very rare and are medical emergencies as mostly they are irriversible and can lead to heart attack

The tretments are based on the strategy that the stable angina is always due to the demand of oxygen exceeds the supply.Hence the reatments should be either 1)Increasing the oxygen supply or 2)Decreasing the oxygen demand by the heart muscles

Oxygen Demand

 One must know the fundamental of this strategy.We know our heart is hardly working without rest upto our death.Every time it is contracting and relaxing with an average speed of 70 per minute.Every contractions and relaxes are composed of the following events:-

1.Preload - the diastolic filling pressure.When the blood enters into the chambers the chamber has to expand to accomodate the filling blood.For this its muscles has to relax against an external pressure and need oxygen.

2.Afterload-the systolic ejection pressure against the peripheral or outside vascular resistance pressure,and need oxygen

3.Heart rate-To keep the heart contractions and relaxations at a constant rate per fixed time need oxygen

4.Wall tension

All the above cosequences need oxygen. 

Classes of Anti-Anginal Drugs

1.Nitrates

2.Calcium channel blockers

3.Beta adrenergic blockers

4.Aspirin

Nitrates

Nirates are acting on heart smooth muscles and relax them as follows:

Nitrates releases nitric oxide which increases in the blood an hormone like substance cyclic Guanosine Mono Phosphate (cGMP) which inturn dephosphorylate the myosin content of the heart and vascular muscles and relax them.

Because of this the veins get dilated and relaxed,the venous pressure is diminished and hence there is a reduction in preload pressure.As a result preload and cardiac output are reduced.

On higher doses nitrates dilates arterioles also followed by reduced peripheral resistance and B.P

Examples of Nitrates 

1.Glyceryl trinitrate for sublingual and intra dermal administration on emergencies as the onset of action is immediate and lost immediately

2.Isosorbide Dinitrate-for oral administration and the effect is not immediate but last for longer time

3.Amyl nitrate - same as above

1.Glyceryl trinitrate which should be taken sub lingually to prevent the first pass metabolism by liver if taken orally as the drug will be 90% deactivated by liver.Also this can be taken by skin patches

this medicine is useful for acute anginal attacks and the onset of action is in seconds to minutes.

As a prophylactic we can use the oral and transdermal forms 

Because of tolerance please keep up nitrate free periods for long time use.

Toxicity Side effects mainly due to its vasodilating effects such as

1.Postural hypotention

2.Dizziness

3.Reflux tachycardia

4.Headaches

Calcium Channel Blockers

1.Nifedipine

2.Verapamil

3.Diltiazem

The mechanism of action is blocking the calcium channels of the vascular muscles and thereby preventing the entry of calcium ions and thus relaxing the muscles.

These are the drugs of choice for treating the variant types of angina known as Prinzmetal's syndrome.

Out of the above three verapamil is more cardiac dependant.

It is he powerfull inhibitor of the conduction at AV node.

Nifedipine is acting mostly on arterioles and therefore it much reduces the B.P.It has no effect on AV coduction system.

Diltiazem is having moderate action on arterioles and AV conduction system

They can be taken I.V.;Oral and Sublingual.

Toxicity 

1. headache

2.Dizziness

3.Nausea

4.Vomiting

5.Constipation

More serious Toxicities

1.Congestive Heart Failure 

2.AV node conduction block.

Beta-Adrenergic Blockers

Examples  1.Propranolo

                  2.Atenolol

                  3.Metoprolol

                  4.Carvedilol

                  5.Labetelol 

                  6.Esmolol 

                   7.Pindolol

                 8.Timolol

They are useful in stable anginas by reducing frequencies and severity of the attacks by reducing heart rate,contractility and BP 

They have no much use in variant and unstable anginas

Contraindications

Beta blockers are contra indicated in Asthma,Diabetes,and Peripheral vascular diseases such as leg pains.

Calcium channel blockers are alternative for these patients

Selection Any medicine in this group can be used but atenolol, timolol,and metoprolol are more preferable as they are cardio selective.

They can be used in combination also as per the requirements

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CORONARY ARTERY DISEASE (CAD)

ANGINA PECTORIS

Coronary artery is the arterial blood vessel which is supplying nutritional pure blood to the muscles of the heart (Myocardium).For all actions of heart it need tremendous energy which is provided by the uninterrepted free flow of pure blood through this artery which is branched throughout the heart muscles into capillaries.

Atherosclerosis is a process by any injury on the inner portion of the blood vessels' wall caused by the rupture of LDL and releasing the sharp needle like molecules of cholesterol which make injury on the inner wall of the blood vessel.These injuries produces atherosclerosis and small portions of these sclerosis becomes plaques and shed as small particles causes clots which is a throbus which then shed small embols which will circulate the whole body and which when arrive he delicate coronary blood circulation it causes blockade.

A thrombus can be formed by any means directly at the coronary circulation.Either way if blood flow is blocked at a portion of coronary artery the area of the myocardium which receives blood from it is deprived of nutrition (oxygen) and become blackish and struggle to cooperate with the rhythmical heart contraction.This condition is known as Ischemia.In ischemia there is an insufficient supply of oxygen to the heart muscle so that oxygen demand exceed supply.

The ischemic muscle will produce pain,or discomfort or both on the chest which is known as Angina Pectoris.  
Angina Pectoris is one of the major contributors of Heart Attack and Heart Failure 
The symptoms of Angina is ranges from a mild to moderate pain on the chest.Some times as instead of a pain a heavy weight put on the chest.
When compared with Myocardial Infarction in which cell deaths occur and fatal ventricular fibrillation angina is reversible if properly attended.
The etiology is based on three aspects
1.Decreased blood flow
This is due to reasons like a)Atherosclerosis;
b)Coronary artery spasm.This condition is rare but often induced by external factors like inserting coronary catheter,or internal hemorrhage,exposure to exreme cold or ergot alkaloids.These angina may precipitate Prinzmetal syndrome or heart attack.
c.An severe traumatic impact of an heavy object on the chest like a car steering wheel,causes capillary hemorrhages
d.Entry of an embol into the capillaries can cause the blockade.
2.Oxygen demands exceed oxygen supply caused by
a)Hard exercises
b)Emotions
The above condition may not need medical intervention because it can be releived by sufficient rest and relax.Very rarely it may become pathogenic
3.Reduced blood flow such as in conditions like anaemias  

Types 

1.Classic stable angina,this is usually occurs during heavy work or exercises.

2.Unstable angina,this is pathologic and occur even in rest and suddenly become worse

3.Prizmetal's angina,this form is mostly due to coronary artery spasm and this condition is very rare.