WHAT IS CORONARY ARTERY?
The blood vessels of the heart are called coronary arteries. Blood vessels are the all prevasive channels, cummunication pathways across all organs of the body and it can be said blood vessels are the largest organs in the body both in terms of volume as well as weight. There are two coronary arteries for the heart, left and right. Usually left coronary artery is the dominant one supplying the front,side and back of the heart. The right one supplies the inferior surface of the heart as well as the right ventricle. In certain individuals ,coronary circulation is said to be right dominant when the right coronary artery supply extend to posterior surface of the heart. On an average both the coronaries carry about 250 ml of blood to heart muscles in each minute.
WHAT IS CORONARY ARTERY DISEASE?
When coronary arteries are affected by the degerative disease called atherosclerosis ,small lumps occur on internal lining of these blood vessels. These lumps keep increasing in size over a period of time slowly reducing the effective blood reaching the heart muscles. The effect of this decreased flow is gradual dysfunction of heart muscles and sensitisation of pain fibres when sufficient blood flow is adequately met rulting in what is known as anginal pain. When such a block reches hundred percent, or when a blood clot is formed just before a ninenty percent block or when a smaller looking block suddenly ruptures, an area of the heart muscle supplied by that blood vessel suddenly suffers damge resulting in sudden suffocating chest pain and breath lessness which we call as heart attack or scientifically as myocardial infarction.
CORONARY ARTERY DISEASE
WHAT IS THE STRUCTURE OF BLOOD VESSELS?
Blood vessls are networks of communication channels of the body, just like our road networks carrying goods to and fro. However body being a dynamic structure, these communication channels also adapted itself to be dynamic. Sometimes, you have to slow don, other times to speed up, sometimes declare a block,etc. For this purpose blood vessels are equipped with minute smooth muscles along its entire body which are under the controll of nerves and hormones. The have the ability to constrict which is called vasoconstriction and dilate when it is called vasodilatation
WHAT IS ATHEROSCLEROSIS?
Atherosclerosis is the wear and tear degeneration of the largest organ in the body called blood vessel organ. Though it look like a process of programmed cell death as a part of ageing, many factore are discovered to exagerate this wear and tear process. Those factors are thought to be High blood pressure, uncontrolled blood sugar, Habit of using tobacco, prolonged stress, lack of physical activity, high unhealthy fat consumtion, obesity, heredity.
WHAT ARE THE CAUSES OF HEART BLOCKS?
HOW HIGH BLOOD PRESSURE CAUSES HEART BLOCKS?
Blood pressure is the pressure excerted on the walls of blood vessels due to the hydrodynamics of blood flowing through it. Blood is a complex fluid with its mesurable physical properties like, molarity,viscosity,chemical composition,etc
Blood pressure is denoted with a nominator and denominator.Nominator is the function of the kinetic energy imparted to the blood due to contraction of the heart and diastolic pressure is the function the neuro muscular tone existing in the blood vessel wall.
Normal blood pressure is around 120/80, which can vary throughout the day depending largely on our physiological state ( excercise,etc) or mental state like extreme emotions.
On bouts of physical excercise or emotional outbursts or stressful situations, blood pressure can shoot significantly. This physiological changes can vary from person to person normally or may be affected by diffent pathological states.
If the blood pressure levels are not within the physiological limits, or if its fluctuations are beyond acceptable physiological range , it is likely to cause mechanical injury to the delicate internal lining of blood vessels. Body when try to heal these mechaical disruptions will never be able to do it perfectly, often leading to scars like humps which later invite other components of blood like excess fat droplets,calcium and platelets. Meanwhile repeated mechanical truma can take place in the same sites. Ultimately these humps keep increasing in size and develop into a full blown block.
HOW DIABETES CAUSES HEART BLOCKS?
Blood is a complex suspension with its normal range of chemical components and properites . Variation from normal of any of its components from thier normal range can have undesirable effects. When the concenteration of glucose in the blood goes beyond normal it facilitate abnormal depositions in the already damaged sites of endothelium in addition to causing intrinsic damage to the blood vessel wall.
HOW STRESS CAUSES HEART BLOCKS?
Stress is a complex neuro-hormonal response from body to many adverse situations which body,mind or intellect faces. To the body it may be some sort of pain ,for mind it may be a bout of negative emotion and for intellect it may be a setback in profession. Body reacts to these adverse experiences by a set of neural and hormonal responses. Externally a stiffness of either a single group or entire muscles of body, an increase in heart rate,increase in BP,an increase in breathing rate, increased acidity or increase in bowel movements.
Internally many of our blood vessels go into a phase of vasoconstriction acted upon by a set of hormones called stress hormones mainly Adrenalin. These hormones also increase the heart rate and blood vessel tone and often result in a higher BP.
Normally body soon overcomes these temporary normal fluctuations, however in certain situations they stay longer,named chronic stress often resulting in mechanical stress in the inner lining of blood vessels much like persistent high blood pressure. Like the case of an uncontrolled hypertensive state,a hump is formed which later develop into a full blown block.
HOW TOBACCO CAUSES HEART BLOCKS?
The acidic nature of Nicotin when it enter into the blood can cause chemical injury to the internal lining of vessels. The chemical injury invite the healing process, further depositions and blocks.
HOW HIGH BLOOD LIPIDS CAUSE HEART BLOCKS?
Blood lipids are suspended particles in the complex emulsion called blood. An increase in the concenteration of these suspended particles naturally make it more prone for deposition in possible areas. An already damaged inner lining of vessel from mechanical stress of high pressure, chemical damage of nicotine or metabolic damage of diabetes make the deposition of these suspended particles more easy.
HOW LACK OF EXCERCISES CAUSE HEART BLOCKS?
Lack of excercises is mostly associated with obesity, pot belly, abnormal response of heart rate and BP to excercise,etc. All contribute in a multitude of ways for the formation of initial endothelial injury and its progression.
WHAT ARE THE SYMPTOMS OF CORONARY ARTERY DISEASE?
Severe coronary artery diseases can be notoriously till a sudden heart attack. More often it can be chest pain called angina on exertion which progress to rest angina,which is often a prelude to acute heart event. When a sudden bout of acute chest pain occurs when a blood vessel got suddenly blocked, it is now a days called acute coronary syndrome and previously called unstable angina.
WHAT IS ANGINA?
Angina is the chest pain arising from decreased blood flow to the heart muscles.However there is no muscle damage in this situation,ECG changes may or may not be there, cardiac enzymes are not elevated.
WHAT IS HEART ATTACK?
Heart attack,myocardial infarction or acute coronary syndrome ,all these are same and is due to sudden complete occlusion of a blood vessel leading to death of muscle fibres in that particular area of supply. This sudden loss of function of a near dead group of muscles lead to reduction in puping function of heart, stagnation of blood in lungs called Pulmonary congestion, drop in blood pressure, decrease in tissue blood perfusion, excruciating chest pain,sweating due to inceases nervous activity and a feeling of near death. The heart attack is suspected from the symtoms and ECG changes and confirmed by the presence of cardiac enzymes.
WHAT ARE CARDIAC ENZYMES?
These are the biomolecules which are normally present inside the myocardial cells,and get liberated in to the circulation in case of cell death as occurs in myocardial infarction.
Some of these enzymes are Trop-T, Trop-I,cpk(creatine phosphokinase),etc
WHY BREATHLESSNESS IN HEART ATTACK?
Death of certain heart muscle lead to sluggishness in heart contractility, with effective failure of heart as a forward pump as well as stagnation of blood behind the heart which is in lungs. This stagnation in the lung lead to congestion which make it needing more effort to expand.
WHAT HAPPEN TO HEART RATE IN ATTACK?
Heart rate can either go up or go down. Normal heart rate is about 50 to 80 in the resting phase which can go up to 120 in a phase of emotional excitement or physical exertion. In certain heart attacks, there is a complication called heart block where heart rate can go as low as 20 to 30 and subsequent hypotention needing an urgent procedure called Pacemaker insertion to increase the heart rate by electronically giving impulses to the heart muscle. While in certain other complications called arrhythmias with varieing names like sinus tachycardia,atrial fibrillation,ventricular tachycardia, the heart rate can go very high beyond the normal range.
WHAT IS HEART ARREST?(CARDIAC ARREST)
In complications of heart attack like, asystole,ventricular fibrillation,etc there wont be sufficient forward flow from the heart to sustain the vital organs. If the condition is not reverted in
in five minutes the vital organ brain can die. This is a dire emergency situation where the rescucitative technique called CPR should be initiated as quickly as possible.
WHAT IS DEFIBRILLATOR?
When the heart run into the high rate complication called Ventricular fibrillation, the forward flow is insufficient to sustain vital organs. This situation is treated by giving Direct current electric shock through paddles applied on the chest wall.
WHY SOME PEOPLE DIE SUDDENLY?
A major heart attack with complications of cardiac asystole, ventricular fibrillation, massive pulmonary edema,etc are one of the commonest causes of sudden cardiac death.
WHAT IS HEART FAILURE?
When heart fails in its function of pumping the blood ahead,it is said to be failing. This happens acutely in a case of massive heart attack, where the manifestations will be flooding of lungs with blood and reduced tissue perfusion and hypotention from lack of adequate flow.
If a heart attack is not treated properly in the first hour(golden hour),a portion of the myoacardium is likely to die. If that is the case the heart function called ejection is likely to drop from its normal 70% to say around 30 to 40 percent. If another heart attack occurs and this time also if the heart didnt recieve adequate treatment,few more heart muscles will die and result in furthur reduction in heart function. When the heart function drop to 20% or less, predominantly breathless which is the sign of lung congestion and heart failure supervene.Activities will be severely limited. This state is called heart failure.
HOW CAN YOU DIAGNOSE HEART BLOCKS BEFORE GETTING HEART ATTACKS?
The blocks causing heart attacks usually starts in a much young age like late childhood or early adulthood. They progress to symptoms and attacks only by fourth or fifth deccade of life. Blocks are usualy harmless till they progress to a significant degree so as to impede the flow of blood to a significant level. Only after 70 to 80% they produce any symptoms. Sometimes no symptoms even up to 90 to 100.
Only an excercise ECG or otherwise called TMT test can show some evidence which point to the possibility of having an asymptomatic block. Before an angiogram the person has to undergo an echocardiogram and a rest ECG.
WHAT IS AN ECHOCARDIOGRAM?
An echocardiogram is an imaging test of the heart using the soundwaves much like an ultrasonogram used for the abdomen. Clear images can be obtained to see the contractions of the all walls of the heart ,size of the heart chambers, inside of the heart as well as the nature of the heart valves. In case of any significant blocks that portion of the heart affected by the blocks wont show any movement all.
WHAT IS AN ECG?
Electrocardiogram or otherwise known as ECG records the electric activity of heart by placing few electrodes on the wall of the chest. While an ECG is very usefull to diagnose a heart attack in its acute phase, it is not very usefull to predict a heart attack. Even a person with 90% block and going to get heart attack tomorrow can have normal ECG today.
WHAT IS A TMT TEST?
TMT test is the taking of continous ECG while the person is continously excercising on the TMT machine. While the person is excercising , the heart is stressed and inadequate blood supply is shown in the ECG. Probably this is the best test to detect asymptomatic blocks.
If the changes are there the TMT test is said to be positive,and if changes are not there the test is said to be negative. If the changes are significant enough , the person has to undergo an coronary angiogram.
WHAT IS CORONARY ANGIOGRAM?
Coronary angiogram is an invasive test whereby a catheter is introduced to the artery of the heart via the groin or hand and a dye is injected and an x-ray is taken which will clearly show the image of coronary arteries. The coronary angiogram will clearly show all the blocks. This is done with the help of an equipment called Cath-lab.
WHAT IS CT CORONARY ANGIOGRAM?
CT means,computarised tomography. By giving the dye via vein without entering the heart ,a reasonable image of the coronary arteries can be obtained, though not very accurate. However this test is not widely used because of the test false positivity and false negativity.
WHAT ARE THE TREATMENTS OF CORONARY ARTERY DISEASE?
HOW A HEART ATTACK IS TREATED?
A heart attack can be of varying severity from a mild attack to a life threatening severity.
A severe heart attck needs resuscitation which means ,the victim is in a bad shape and need stabilisation of oxygen level, blood pressure ,heart rate . Sometimes oxygenation needs ventilatory support and BP stabilisation need artificial heart support,etc.
Once the condition is stabilised the focus is shifted to removing the block it caused. If the treatment facility has a cath-lab set-up, patient is taken to the cath-lab ,angiogram done,block located and if feasible the block is removed by what is known as primary angioplasty.
If the blocks are not suitable for angioplasty or if too many blocks are there, patient is subjected to bypass surgery.
If cath-lab facility is not available in the treatment facility, another treatment option called thrombolysis is used where the clot forming 100% block is lysed with medicines called thrombolytic agents. The commonly used thrombolytic agents are thrombokinase,urokinase or tissue thromboplastin activator.
WHAT ARE THE MEDICAL OPTIONS FOR CORONARY ARTERY DISEASES?
Aspirin and Clopidogrel are the commnly used anti-platelet agents. They thin the blood and prevent platelets from getting deposited on the blocks furthur.
Of this Aspirin is highly gastric irritant and best taken at Lunch time after food.
Nitrates are potent antianginal drugs which relieve the anginal pain by dilating coronary arteries. Commonly prescribed drugs are sorbitrte ,glyceryl trinitrate,etc
These are a group of medicines which block the beta receptors present on the heart as well as blood vessels. The commonly used ones are Metoprolol, Atenelol, Bisaprolol,etc
The reduce the contractility of the heart, rate of heart,reduce the myocardial oxygen demand and reduce the BP.
4.Calcium Channel blockers.
The poular medicines of this group are Amylodipine, Diltiazem,etc which also reduce the myocardial oxygen demand,reduce blood pressure and heart rate and relieve angina.
WHAT IS THROMBOLYSIS?
Thrombolysis is the treatment option given to heart attack victims,if cath-lab facility is not available or if not feasible. In this treatmet option clot busting agents like thrombokinase,urokinase or tissue thromboplastin actvator are used to bust the clots which is causing 100% block resulting in myocardial cell death.
WHAT IS GOLDEN HOUR TREATMENT?
In a heart attack maximum cell death happen in the first hour of the attack. Maximum death happen in this period. If the block or clot causing 100 % compromise can be removed in the first hour, the entire affected myocardium can be recovered completely without any damage. However after this period, myocardium may get damaged permanently and replaced by fibrous tissue.
WHAT IS ECCP?
Extra-corporeal counter pulsation therapy. This is a treatment where the body parts are compressed intermittently with the idea of improving blood circulation to the coronary vessels. This is a FDAapproved treatment for resistant anginas where angioplasty and bypass surgeries are ruled out.
WHAT IS CHELATION THERAPY?
This is a treatment where a chemical called EDTA, is injected hoping that this EDTA,will chelate the calcium present among the blocks therby reducing the percentage. However there is no evidence to back its usage and hence not recomended.
WHAT IS ANGIOPLASTY?
Angioplasty is a treatment option in many coronary blocks wherby a guide-wire is negotiated across the block and a balloon is inflated at the block,therby dilating it and leaving a metal or drug eluting or biological stent there to prevent furthur blockage.
ANGIOPLASTY OR BYPASS SURGERY BETTER?
Both has its own advantages and disadvantages. In bypass surgery ,there have to be a cut on the body,possibility of blood loss,pain and a small chance of infection, all blocks can be corrcted by if necessary by arteries itself. Both mammary arteries and radial arteries can be used to get complete artereal revascularisation. The hospital stay is around 7 days.
In angioplasty,there is no need to cut on the body, no blood loss, no chance of infection and minimal hospital stay. There is a small chance of stents getting re-stenosed.
Generally if blocks are less in number or less complicated ,Angioplasty is used and if blocks are complex and multiple,bypasssurgery is used.