A detailed discussion is beyond the scope of this book and hence only the salient features have been addressed :

Before opting for invasive treatment, it is best to analyze what exactly are we going to achieve with invasive treatment. One should take into account the pros and cons and factors in the risk and benefit ratio. This is particularly applicable to patients in our country. If these invasive methods were as far as getting a tooth removed or getting one’s appendix taken out there would be no controversy. However each invasive option has got its own risks including the risk of death and other procedural complications. The problem of relapse and its relative benefit has also to be accepted. Basic consideration should be given to the patient’s symptoms, and his life style and that should be the main factor in justifying such an approach. These procedures are mainly meant for better symptomatic relief of pain rather than for altering the future course of an unpredictable disease. In general, the principle of 4 A’s - Activity, Associated diseases, Attitude and Age may be taken into account for a proper decision.

Other important factors to be generally remembered before running or rushing for Invasive treatment
They are :

1. In two-thirds of patients the acute problem arises from the rupture of a Soft fatty plaque known as vulnerable plaque which is less than 50% blocked rather than in a fibrosed, hard, organized and calcified atheroma which may be even 90% blocked. The occurrence of plaque rupture may start a clotting cascade, resulting in formation of a blood clot that progressively gets larger and larger until it finally occludes the lumen of the artery, completely obstructing blood flow. This can happen in a matter of just few hours so as to lead to the syndrome of an "acute Heart attack. "
   
   
   
2. The logic of saving of the heart muscle due to a chronically obstructed artery is also not sound. Natural collaterals do form in an artery with gradual but progressive obstruction. This compensation can minimize a sudden severe heart muscle damage inspite of severe degree of observed blockade. A good myocardial salvage is possible, however, in the setting of an acutely obstructed artery causing acute anterior infraction.
   
   
   
3. In an asymptomatic or a minimally symptomatic patient the significant chronic obstruction can be dealt with either surgically or medically depending upon many other factors such as genetic history, hyperlipidemia, age, sex, objective evidence of significant ischemia, life style etc. The mind-set to "attack " early because the blocks are major is not logical. A systematic analytical approach is required. The presence of symptoms limiting life style and or the presence of significant objective ischemia, does favour consideration for interventional or surgical treatment.
   
   
   
4. Generally there is no particular rush or emergency to " fix " the blockages once they have been detected. No matter how severe the blockage or how many are detected one can wait, unless there are active symptoms of chest pain. In most instances intervention or surgery can be scheduled electively. The concept of Myocardial salvage - it is not likely to hold much water for a chronically occluded artery because of the presence of previously developed collateral channels. This is indirectly suggested by a good Left Ventricular Ejection Fraction. (E.F.).
   
   
   
5. All said and done, coronary artery disease is an unpredictable disorder and no one can accurately predict its course by any of the methods available today. A panicky approach does not help the patient and in fact may hurt him. The severity of his present symptoms become the most important criteria for immediate Invasive approach. The natural body defence mechanisms may salvage myocardium better. The temptation to look at mere blocks mechanically and hope to achieve a lot by tackling the blocks is rather an exaggerated claim. Modern medicine in spite of the advances still has its short comings which must be understood and acknowledged. At present we seem to be "obsessed " in trying to work around the blockages of only large epicardial coronary arteries. Recent development of molecular biology of the terminal small arteries, capillaries and myocardial cells have helped our understanding. After all, these are the final or terminal pathways for the ultimate delivery of blood to the cells. Their health is most important. No amount of opening up of the larger tubes would work unless the terminal supply channels are healthy. This concept definitely deserves more thought.
   
   
   
6. There is no doubt that modern techniques like Bypass surgery and angioplasty are highly effective for the relief of anginal discomfort or pain. However, they are by no means a cure for the disease. A survival benefit from surgery has been shown in 15% to 20% of patients where the arterial blocks are specifically located in the Left Main Artery or in the Proximal segments of all three arteries. This survival benefit applies only to that subgroup of patients and definitely does not apply to all patients. The rest of the benefit is derived from favourable natural forces of blood, nervous system, artery endothelium, health of the terminal delivery channels and the cellular metabolic response.
   
   
   
7. Every procedure has its own risks, however small. There could be immediate and late complications. Moreover there is the rate of relapse of the original blockage. Finally the results from surgery are not permanent. There can be degeneration of the bypass graft. All the pros and cons must be carefully considered. The only preventive methods known to-date are a proper diet, age-related moderate exercise, control of body weight, abstinence from all forms of tobacco, adequate control of high blood pressure, diabetes, cholesterol and some modifications of life-style.
   

(A) Coronary Artery Bypass Surgery in Coronary Artery Disease :

A brief description of the surgical treatment of ischemic heart disease is presented. The role of the so called " bypass " or graft surgery is mainly for the relief of symptoms. It is not a cure. The natural progression of disease may continue unabated in spite of Bypass surgery. It has been shown to prolong life in a small select sub group of patients ( 15020% ) as mentioned earlier. The blocked segment of the artery or arteries can be "bypassed " by with a vein or artery graft. The graft connects the aorta to the coronary artery beyond the area of block. One could look upon this as a diversion or side road that allow blood from the aorta to enter the coronary artery beyond the blockage. This is a kind of a "plumbing" operation. The live veins for the purpose of grafting are obtained from the patient’s own leg. It is now standard procedure to use an arterial graft, Left Internal Mammary Artery ( LIMA) especially to bypass the left anterior descending artery. LIMA grafts have far superior longevity than vein grafts. The use of other arterial grafts have so far not proved their superiority.

This procedure often gives better relief of symptoms. It has no control over the progress of underlying disease of atherosclerosis which can continue at its own pace. This type of surgical treatment can at best improve the quality of life of a patient but not the quantity in terms of span of years in the great majority of the operated patients. The chances of subsequent or future attacks are not necessarily minimized.

One has also to understand the other limitations of bypass surgery :

1. The average mortality from this kind of surgery is about 2 percent. It may be 0.5 percent in a volume loaded more experienced center with a superb infrastructure.
   
   
   
2. Graft failure of vein grafts occurs at a rate of 10% per year. Therefore at the end of 4 to 5 years there is an average 40% chance that symptoms may recur.
   
   
   
3. The incidence of a fresh heart attack ( myocardial infarction ) during and immediately after surgery is about 2 to 5 percent - "Perioperative Infarction".
   
   
   
4. Complete relief from anginal pains is obtained immediately after the operation in about 85% of patients. About 15% do not obtain relief from anginal pains.
   
   
   
5. This type of surgery is likely to give better results in only those patients with a near-normal sized heart. A grossly dilated heart or a weakly pumping heart is less likely to improve in its function by this surgical procedure. The operative mortality in such cases would be decidedly high.

The above statistics can be improved in heart centers where there is a good infrastructure. The experienced and well organized medical team along with specially trained nursing staff would help a lot in minimizing surgical mortality, morbidity and complications.

The following groups of patients can be selected for the benefit of surgical "bypass" :

1. Patients with intractable anginal pains who do not respond to medical treatment and where anginal pains become a regular handicap in their day-to-day lives.
   
2. Patients with proximal triple vessel disease.
   
3. Patients with significant disease of the left main coronary artery with more than 50% blockage.

As mentioned earlier, even in such patients, it may be better to avoid surgery if the heart is markedly dilated or if the muscle pump is very weak. Surgical risk will be high and the result of the operation is not likely to be satisfactory.

In a patient who has a ventricular bulge or aneurysm, the surgical removal of the bulge, if successful, can be a rewarding operation.

(B) Newer Methods of Interventional Treatment (Balloon Angioplasty, Stents).

These newer techniques are less invasive than surgery, hence a great increase in their popularity. The basic aim is the same in all interventional techniques, to distend the lumen of the coronary arteries either by inflating a balloon in the narrowed segment of the artery, or by developing a metal stent which distends the blood vessel from the inside and hence increases lumen diameter. This increase in lumen diameter permits increased blood flow, allowing for more oxygen and nutrients to reach the heart muscle. These procedures are done under local anesthesia, the post procedure recovery period is shorter and therefore they are becoming increasingly popular.

Although this sounds like a relatively simple procedure it has several limitations, complications and occasionally may even aggravate a stable situation into a life threatening problems. The limitations must be understood before getting entirely sold on this method. The important points to consider are :

1. The relapse rate of reobstruction with the use of stent is reduced but is not completely eliminated. The best figures of the most well organized centres of the world unfortunately are often quoted by each and every centre around, even with poor infrastructure. The rate of reocclusion at six month period quoted now a days is around 10 to 15% in an artery which was more than 3 mm. in its internal diameter. The serious complica- tions of " Sub acute thrombosis " has been brought down from 5% to 2 to 3%.
   
   
   
2. The technique has a reputation of being safety in contrast to surgical cutting with risk of major anesthesia. The safety, how ever, is relative and not absolute. About 5-10% of patients do have problems of bleeding and fresh thrombosis within 2 to 3 days. There is a 1% chance of the patient being immediately wheeled in for emergency bypass surgery. Such an emergency operation almost carries double the usual operative risk.
   
   
   
3. A competent backup cardiac surgeon and his team should be kept ready " in waiting " , to immediately tackle such a complication, should it arise. Other methods such as Atherectomy, Rotors, Laser, etc. as a routine are quite disappointing so far. They are used selectively Until today, each method has certain advantages but at the same time every method also carries some problems of complications and relapse.
   
   
   
4. The popular stent angioplasty is costly. In fact, it is as costly as C.A.B.G. surgery. Should there be a complication, the cost can escalate to almost double. For good results, the internal diameter of the artery to be stented should be more than 3 mm. With less lumen, the stent results are not so good.
   
   
   
5. The obstructive atheroma or a crack can develop in future in any other uninvolved or native coronary artery.
   
   
   
6. Hence its risk : benefit must be discussed with the patient.
   
   
   
7. The efficacy of primary or emergency angioplasty and its possible help, possible complications, its limitation, etc. should be properly discussed with the family before their consent is taken. It can be alleged as "emotional blackmail " if myocardial salvage success rate is overstated.
   

   In spite of everything, there is no doubt that new generation stent, balloon or similar techniques to clear the obstructed coronary artery can be considered as the major scientific advances of today. They offer better future promise.
   

The natural pacemaker is situated in the right atrium which is the upper chamber of the right heart. That location where impulse forming centre generates electrical impulses is technically known as the Sinoatrial node. The function of this pacemaker is to regularly provide a stimulus which goes along to excite the whole heart. The pathways for conducting this stimulus is well charted out in both the upper and lower chambers. The lower conducting pathways are comprised of the A.V. node, bundle of His and bundled branches.

As the stimulus spreads within the four cardiac chambers, it activates them to contract. Normally, the automatic stimulus ( sinoatrial node ) produces the impulse at a regular rate and rhythm. The rate varies from person to person and even in the same person, depending on so many day-to-day factors such as emotion, exercise, fever, etc. The usual rate is from 60 to 100 per minute with a rhythm which is regular.

There are, of course, still some wider limits which can be considered normal. IN some diseased conditions, there may be failure in impulse generation at the natural pacemaker site, or a problem in the conduction or spread of the impulse through the specialized conduction pathways. In such diseases conduction or spread of the impulse is formed by the natural subsidiary centers such as A.V. node. It generates impulses at unusually slow rate of 45 or below per minute.

The heart contracts at a very slow rate and therefore the pulse is similarly slow. The patient gets symptoms of temporary spells of dizziness or unconsciousness, as sufficient blood does not reach the brain. The disease when advances, can be life-threatening. IN order to treat such a group of diseases with an unusually slow rate, a device called an Artificial Pacemaker is available.

These are small electronic instruments with fixed wires, which can be so introduced and implanted in the body and the heart that they are capable of producing the rate which is more or less similar to that of the natural pacemaker. They need to be introduced either temporarily for a few days when they are known as Temporary Pacemakers. More often they are needed lifelong and are called Permanent Implantable Cardiac Pacemakers. An average life of a permanent pacemaker battery is about 10 years and this can be replaced whenever necessary. There are rate responsive pacemakers available nowadays. They can be programmed and modified from outside, when it is necessary to change the rate, voltage , etc. The implantation of the pacemaker can be done under local anesthesia and it is a relatively minor surgical procedure. The modern rate responsive pacemaker is even capable of adjusting the heart rate according to the body demands by sensing the blood temperature, respiratory rate, muscle movement, etc. The newest device is Dual Chamber Pacemaker where the electrodes are fixed in both right atrium and right ventricle. Pacemaker therapy is generally useful for those heart diseases with an unusually slow heart rate. It does not help in giving more power and hence it does not help a flabby dilated heart or a heart muscle with a weak contraction. The latest development in this field is the implantation of what is known as A.I.C.D. - Automatic Internal Cardiovertor and Defibrillator. This is done in a heart patient who gets repeated attacks of life threatening fast and irregular heart rate such as ventricular tachycardia, ventricular fibrillation. This device is basically a computer chip that constantly monitors the heart rhythm and when it sees a derangement it follows an algorithmic approach and provides minor electrical shock for fast rhythm to disappear.