General about Heart Conditions
Coronary artery disease is stenotic arteriosclerosis - a narrowing of coronary arteries caused by atherosclerosis. When sufficiently severe this limits blood flow to myocardium (heart muscle). In its most severe form it occludes (blocks) the coronary arteries. Coronary heart disease is caused by a build up of fatty matter in walls of coronary (heart) arteries. These arteries become rough and narrowed on the inside limiting supply of oxygen-rich blood to the heart muscle. This can cause chest pain (angina) or increase the risk of heart attack. The fatty deposit can be removed (coronary angioplasty) or the damaged arteries replaced (coronary bypass surgery). Patients who have coronary angioplasty are able to return to work sooner than CABG.
In coronary angioplasty a tube (inducer catheter or sheath) is inserted into the femoral artery in groin. A dye is used so that the narrowed artery can be viewed on monitor. Thin tube with balloon at tip is carefully threaded to the area of narrowing in coronary artery. Balloon then inflated for several seconds. This splits and compresses the fatty material in the artery wall. Opening in artery enlarged to allow blood to flow more easily. Catheter removed - about three hour op. In 1990 more than 500,000 patients in USA had a revascularisation procedure and about 300,000 underwent percutaneous transluminal coronary angioplasty (PTCA). This increased to 325,000 in 1992 and 362,000 in 1993. Overall about 500,000 angioplasty procedures were performed world wide. Coronary artery bypass graft (CABG) and PTCA are the two most common revascularisation treatments for severe coronary artery disease. About 670,000 revascularisation procedures in 1993 (USA) - 309,000 CABG ($30,000) compared to the 362,000 PTCA ($15,000).
In the early years (1977-81) with primitive equipment and limited operator experience, coronary angioplasty was recommended in symptomatic, clinically stable patients with well-preserved ventricular function who, otherwise, were good candidates for coronary bypass surgery. Coronary angioplasty was indicated in patients with single-vessel disease with stenoses (narrowing) and not occlusions (blockage) that were proximal, discrete and non-calcified and did not involve arterial segments that were angulated or gave rise to major side branches. With evolution of both angioplasty hardware and technique, the clinical and morphological profile (study of structure rather than function) patients acceptable for coronary angioplasty has widened considerably.
With non-occluded coronary arteries the clinical outcome of angioplasty is successful in 90% patients. Angioplasty has lower success rate with stenoses that are long, eccentric, angulated, calcified, ostial or associated with thrombus. The success rate is lower in patients with unstable angina of advanced age. Difficult to manipulate catheter guide wire through an occluded region and lower initial success rate was seen (65-70%) in angioplasty performed on occluded lesions. Chronically occluded lesions are less likely to be successful than recently occluded vessels, in which occlusion is short, tapered, not calcified and not bridged by collateral vessels. Angioplasty of saphenous vein grafts less than 4 years old especially with lesions at distal anastomic sites resulted in favourable outcomes. Success rate and frequency of acute complications are similar among patients with diseased native arteries but incidence of restenosis is higher in patients with diseased vein grafts.
Stable angina pectoris often recurs in a regular or characteristic pattern. Commonly recognise angina only after several episodes have occurred and pattern has evolved. Level of activity of stress that provokes the angina is somewhat predictable. Pattern changes only slowly. This is "stable" angina - the most common variety. Comparing angioplasty (PTCA) with medical therapy in single vessel disease and stable angina revealed PTCA was more effective than medical therapy in relief of angina. PTCA is not recommended as initial therapy for stable symptoms and single vessel disease.
Instead of appearing gradually, "unstable angina" may first appear as a very severe episode or as frequently recurring bouts of angina. Or an established pattern may change sharply. May be provoked by less exercise than before or occur at rest. This needs prompt medical attention. The term "unstable angina" is also used when symptoms suggest heart attack but diagnosis does not support this. May have prolonged chest pain and poor response to rest and medication but no evidence of heart muscle damage either on electrocardiogram or in blood enzyme test. There is no advantage of PTCA over medical therapy in unstable angina.
Anticoagulants that dissolve blood clots. Increasing age strongly associated with denial of this thrombolytic therapy. Elderly have higher risk of bleeding (rare intracerebral haemorrhage - bleeding into brain) with this therapy but there is also the higher risk of dying from acute myocardial infarction. Coronary thrombolysis is a double edged sword - which edge is sharper? Compared to thrombolytic therapy, coronary angioplasty is better at restoring anterograde (previous) flow and less recurrence of ischaemia. Greatest benefit to older patients and those with anterior infarction (blood supply cut off) or persistent tachycardia (abnormally rapid heart beat). PTCA has profound advantages over CABG.
Essentially a non-surgical alternative. Less expensive and less invasive. PTCA is catheter-based procedure that directly dilates the vessel at point of obstruction. Local injury. Discharge within days. CABG is major surgery, requiring opening of the chest wall. New blood circulation channel is provided with a lumen frequently larger than the native diseased lumen. Both alleviate the effects of coronary artery disease but do not correct or alter natural course of the disease. PTCA preferred over CABG. However, revascularisation is incomplete and restenosis occurs with PTCA. CABG addresses a more severe condition compared to PTCA in first time revascularisation. Restenosis remains its Achilles heel.
Subsequent repeat of PTCA or a first time CABG after PTCA within one year of initial PTCA compared to those undergoing CABG surgery as first treatment is 30.5% vs 3.6% in single vessel disease and 34.5% vs 3.2% in multivessel disease. Higher prevalence rates of angina also observed in patients having PTCA compared to CABG (14.6% vs 6.5% for single vessel disease and 17.8% vs 12.1% in multivessel disease). However, incidence of death, non-fatal myocardial infarction or cardiac death within one year are similar for both treatments. Relative merits of PTCA vs CABG difficult to assess. Population, changing techniques, restenosis. In patients with diabetes mellitus (Type I and II) on oral hypoglycemic agents or insulin, CABG has a markedly lower five-year death rate than angioplasty (19% vs 35%).
Higher death rate not due to complications of procedure itself. In patients without diabetes and those with diabetes but not on drug treatment, 5-year mortality rate both at 9%. (It would seem that drug treatment raises death rate from 9% to 19 - 35%.) PTCA still faces several obstacles - despite its success in the intervention of coronary artery disease. The most daunting is restenosis. Development of wide variety of new devices for the improvement of percutaneous coronary intervention. Includes atherectomy catheters, stents, laser devices. Most are used as adjuncts with balloon angioplasty before (predilate), during (as part of procedure) or afterward (to improve luminal diameter and reverse or prevent complications from PTCA). Formidable challenges to coronary interventional procedures - old (impassable) occlusion, abrupt vessel closure from dissection and restenosis. Prevention will require intravascular devices to open obstructed arteries to fullest extent and techniques to inhibit hyperplastic (overgrowth) response. Combined use of pharmacotherapy (antiplatelet and antithrombotic agents) with coronary angioplasty devices needed.
Coronary Artery Bypass Graft
Aortocoronary bypass surgery means that one or more bypass grafts are implanted between aorta and coronary blood vessel. If occlusive vascular disease limits blood flow to heart, bypass graft bridges occluded or diseased heart blood vessel (coronary artery) and brings new blood to the heart. Two types of blood vessel commonly used for bypass graft (CABG) - saphenous veins in legs or left or right internal mammary artery (aka thoracic arteries) of chest wall. Both can be used as there are other pathways that circulate blood to and from the tissues of chest and legs. Type of graft depends on the location and amount of blockage in the coronary arteries.
Saphenous vein surgically removed and graft sewn from aorta (large artery leaving heart) to coronary artery below blockage. Oxygen-rich blood flows from aorta through saphenous vein graft past site of blockage to coronary artery to nourish heart muscle. Mammary artery kept in tact at its origin and sewn to coronary artery beyond blockage site. As it is an artery it does not have to be sewn to the aorta. Arteries have their own oxygen-rich blood supply to offer the heart muscle. After thoracotomy (opening chest) the left IMA (internal mammary artery) is harvested. Simultaneously a segment of the saphenous vein is prepared for the aortocoronary bypass operation. After induction of extra-corporeal circulation the aorta is X-clamped, the coronary arteries are exposed, opened and the IMA is anastomosed (sutured) into the coronary artery. The IMA bypass to the coronary artery now supplies arterial blood to the heart muscle - bypassing the occluded coronary artery. Re-operations (previously undergone CABG already) constitute about 11% of all bypass procedures.