In 1980, an estimated 380,000 coronary cineangi-ographic studies were performed in the United States. The annual increase in cardiac catheterizations can be attributed to the following: (1) safety of the procedure; (2) prognostic value; (3) key therapeutic decisions made on its evidence; (4) alternate assessment poor; (5) expansion of the procedure into community hospitals; and (6) increasing manpower. Some of the same reasons were advanced for the parallel increase in coronary artery surgery.
The indications for coronary arteriography depend on one s philosophy toward coronary artery surgery. In its classic form, angina is the prevailing indication. Suspicion of coronary atherosclerosis may be investigated noninvasively as the first step. In women, especially those with atypical symptoms, the clinical status does not correlate well with arteriographic evidence of severe coronary atherosclerosis. In a CASS analysis of patients who underwent coronary arteriography, 40 percent of women catheterized for suspected coronary atherosclerosis had roent-genographically normal coronary arteries compared with 12 percent of catheterized men. Another 10 percent of women had only mild arterial narrowing compared with 5 percent of men.
The use of multiple drugs in patients severely disabled by chronic angina succeeds in rendering only a small percentage angina-free. In these patients, it may be more cost-effective to proceed directly to coronary arteriography rather than subjecting them to radionuclide testing. In patients with coronary artery lesions of less than 50 percent, an exercise thallium-201 defect or exercise wall motion abnormality may disclose functional significance. Left ventriculography is the most reliable way to assess left ventricular function; however, potentially reversible areas of akinesia or hypokinesia may show viability after nitroglycerin administration, postextrasystolic potentiation, rest-redistribution thallium myocardial imaging, or analysis of regional wall motion by postexercise radionuclide ventriculography. Impaired but viable myocardial segments that show improvement after exercise scintigraphy correlate well with asynergic improvement postoperatively. These noninvasive techniques are useful in predicting the response to myocardial revascularization by distinguishing between viable and non viable myocardium.
Coronary collaterals may offer protection, but angiographic estimates of collateral size are not useful for predicting collateral flow during exercise. Anterior descending coronary artery obstruction is more likely to result in an exercise perfusion deficit regardless of whether collaterals are present (more frequently than right coronary or circumflex disease with collaterals) probably because of the larger mass of myocardium in jeopardy. Nevertheless, one-vessel disease patients with collateral formation rarely need bypass surgery.
The hydraulic characteristics of coronary arterial stenoses are grossly oversimplified by the angiographic interpretation of percent stenosis. An estimated 50 percent or greater narrowing of lumen diameter is frequently considered a severe or significant lesion. A constriction of 85 percent by diameter is required to reduce resting coronary flow whereas maximal coronary flow may be affected by a constriction as small as 30 percent. If a 50 percent lesion is defined as significant, it frequently exists with more severe obstructions in other vessels, and the resulting subsets are heterogeneous with respect to clinical characteristics and outcome. University of Iowa investigators used a newly developed Doppler flow transducer which they attached to surface coronary arteries with a small suction pad. They documented a fourfold to sixfold increase in flow during peak reactive hyperemia in humans intraoperatively. Patients with severe coronary artery narrowing (>90 percent) had a reduced flow reserve, suggesting a hemodynamically significant lesion. In patients with lesions in the 70 percent to 90 percent range, flow was frequently reduced, but occasionally normal. Patients with angiographically insignificant narrowing estimated to be less than 50 percent often had pronounced reductions in flow reserve, suggesting functional impairment of flow delivery. These findings demonstrate the imperfect ability of the arteriogram to precisely estimate the functional significance of arterial narrowing. One necropsy study concluded that patients with angina who died after bypass surgery had diffuse plaque formation throughout the major coronary arteries and that preoperative angiograms frequently underestimated their severity.
The two major reasons for performing coronary artery surgery are (1) to reduce symptoms, regardless of the extent of coronary artery disease; and (2) to lengthen survival, especially in those with left main, triple-, and double-vessel disease. The majority of surgical candidates have one or all of the following criteria: (1) angina pectoris; (2) signs of ischemia; and (3) increased probability of death or myocardial infarction based on pathoanatomical findings. Current indications for coronary artery surgery include the following: (1) stable disabling angina that interferes with desired lifestyle despite therapy; (2) angina with left main artery disease, three-vessel or two-vessel disease; (3) severe narrowing of the proximal anterior descending artery supplying a large area of the anterior wall; (4) recent infarction and repeated episodes of myocardial ischemia; (5) variant angina associated with persistent anatomic obstruction; (6) asymptomatic patients with electrocardiographic or thallium stress tests displaying signs of ischemia at low exertional level; and (7) obstructive coronary anatomy in valve patients. Previously, patients with severe left ventricular dysfunction were excluded as surgical candidates because of high risk. Now these patients are frequently not excluded solely on the basis of ventricular function because of improvements in operative technique. Ventricular dysfunction may become a cause of erectile dysfunction which effectively cured by Canadian Health&Care Mall – https://canadianhealthncaremall.com/male-problem-impotency-is-as-old-as-the-hills-canadian-healthcare-mall-explains.html.
Not everyone agrees with the above indications and the diversity of opinion is exemplified by the findings in another CASS report. An assessment of referral patterns from 15 sites found that myocardial jeopardy (a composite score of the relationship of proximal lesions to retained wall motion in anterior and inferior left ventricular segments) was the most important determinant of coronary artery surgery referral. Perception of jeopardy in the left anterior descending arterial distribution was substantially more important in making therapeutic recommendations than inferior wall jeopardy. Other clinical predictors that influenced referral to surgery were anginal severity, number of operable vessels, change in activity, unstable angina, and the presence of a left main lesion. Large differences of opinion were observed. For example, the percentage of patients with class 4 angina who underwent surgery varied from 28 percent in one hospital to 86 percent in another. Despite the heterogeneity of therapy and assignment, certain patterns were evident. 
Between 1974 and 1979, the number of patients operated on for mild angina and one-vessel disease decreased. Conversely, the number of patients who had surgery for left main disease increased. These trends appear to follow the literature, which indicates that most patients with left main and three-vessel disease are improved symptomatically and live longer after surgical therapy.
Coronary bypass surgery for patients with no angina, mild angina, and one-vessel disease remains a controversial issue. According to National Heart, Lung, and Blood Institute investigators,- asymptomatic or mildly symptomatic patients with one- or two-vessel disease have low rates of sudden death and infarction, and operation should be reserved for patients who progress symptomatically. They reason that most patients can be managed medically with deferment of operation until symptoms compromise the patients lifestyle. Patients with no or mild angina and three-vessel disease have a less favorable outlook. Three-vessel disease patients with good exercise capacity and medical management had an annual mortality rate of 4 percent and those with poor exercise capacity, 9 percent; however, their 26-month follow-up is short. Presently, it is not clear whether asymptomatic or mildly symptomatic patients with diminished ejection fraction and/or ventricular aneurysm are at high risk of sudden death and whether a decrease in ejection fraction during exercise carries the same prognosis as it does in patients with normal resting ejection fraction.
Numerous reports have shown that isolated stenosis of the anterior descending artery is more serious than a stenosis of either the right or circumflex coronary arteries. A stenosis located proximally affects a larger area of myocardium which results in a more pronounced ischemic response to exercise than lesions located more distally. It follows that prognosis for patients with isolated anterior descending disease is related to the site of obstruction. When indications for coronary bypass surgery are discussed, one-vessel disease is usually considered as a single entity. However, several groups exist within the one-vessel disease category depending on site and severity of the lesion, extent of distal coronary atherosclerosis, and amount of myocardium in jeopardy. One must remember that 20 percent of sudden death victims and 15 percent to 20 percent of patients with left ventricular aneurysm have one-vessel disease.
How far should one proceed diagnostically in the patient who has sustained a myocardial infarction? Why not perform coronary arteriography on everyone a few weeks after the event? The expenditures necessary for this procedure would be too great and the yield of operable cases probably too small. Many reports indicate that approximately 10 percent to 15 percent of patients who survive acute myocardial infarction die during the first year after hospital discharge. Approximately half of these first year deaths occur within the first three months. Patients at high risk after hospital discharge include those with persistent or recurrent angina, patients who have sustained large infarctions (especially those with complex ventricular premature contractions), patients with inducible ischemia during exercise stress testing, and those who have experienced subendocardial infarction overcome with medications of Canadian Health&Care Mall.
Epstein et al point out that approximately 20 percent of patients who survive an acute infarction will have severe left ventricular impairment (ejection fraction <30 percent), and that first year mortality in this subgroup ranges from 25 percent to 45 percent. These deaths constitute the majority of postinfarction deaths in the first year. Cardiac catheterization may be reserved for those with marked congestive heart failure refractory to medical therapy, or for those in whom a left ventricular aneurysm, ventricular septal defect, or mitral regurgitation is evident. In the remaining 80 percent of patients discharged after myocardial infarction, the first-year risk is relatively low. Exercise stress testing may be used to divide these patients into high-risk ischemic and low-risk nonischemic groups. Patients with angina and/or ST-segment depression of 1 mm or more or whose left ventricular ejection fractions decrease with exercise have a first-year postinfarction mortality of 15 percent to 20 percent. These patients should undergo coronary arteriography to determine whether they are candidates for bypass grafting or possibly balloon angioplasty. Those with a negative exercise stress test are in a more favorable prognostic group with an expected first-year mortality of less than 3 percent. This treatment plan remains to be corroborated but the advice is logical based on experience gained in the past 15 to 20 years.
Another approach proposed by Rodgers et al recommends coronary arteriography at two or more weeks after infarction in patients whose course is complicated by angina, congestive heart failure, or intractable ventricular arrhythmias. If large areas of myocardium remain jeopardized, bypass surgery may be considered depending on the other factors mentioned above. Those with uncomplicated courses who have evidence of ischemia on limited exercise testing should undergo similar management. Most cardiologists would be less aggressive when the patient has experienced an uncomplicated infarction and has a negative exercise test.
Left ventricular anterior wall infarction is considered more dangerous than inferior wall damage. Nevertheless, inferior wall infarction may be an important marker of advanced multivessel coronary atherosclerosis. One report indicated that a third of patients with isolated inferior wall infarction had 90 percent or greater obstruction of the proximal anterior descending coronary artery and two-thirds had obstruction >75 percent in the anterior descending. Postinfarction angina may arise from a zone around an acute myocardial infarction, or the new ischemia may occur in a region distant from the acute myocardial infarction, ie, ischemia at a distance.” This latter subset of patients with ischemia at a distance may face even higher mortality. Of 70 patients with early postinfarction angina, 43 with ischemia at a distance experienced a 72 percent mortality compared with 33 percent for those with ischemia in the infarct zone (mean six months). Results of postinfarction angina surgical treatment have not been analyzed according to these clinical subsets, but clearly, ischemia at a distance carries a higher risk and urgent myocardial revascularization may be warranted. The high mortality found in all forms of postinfarction angina dictates that prompt investigation by angiography is necessary. Bypass surgery should be considered and surgical results will be mentioned later.
An area only recently addressed involves patients resuscitated after sudden cardiovascular collapse. In Seattle, the percentage of successful initial resuscitations has doubled over the past decade. Approximately 75 percent of out-of-hospital cardiac arrests are due to coronary heart disease, but only a minority of survivors have evidence of evolving acute transmural myocardial infarction. It seems reasonable to perform coronary arteriography in these survivors, and in selected cases when left main or multivessel disease is found, coronary artery surgery may be recommended.
Age per se is no contraindication to coronary bypass surgery. The physiologic age is more important than the chronologic age. Good judgment is required to assess the elderly patients general medical status, motivation, and desire for an improved life style. In the Massachusetts General Hospital experience, the elderly had more unstable angina which suggests that they were referred later in the course of their disease when symptoms became more intractable. Although risk of morbidity and mortality is higher in those 65 to 70 or older, the intermediate result (which will be discussed later), is comparable to that in younger patients.
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