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 oneís 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 patientís 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 Aís - 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 :
(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 patientís 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 :
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" :
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 :
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.