Progression of coronary atherosclerosis. Clues to pathogenesis from serial coronary arteriography

Risk factors for cardiovascular disease and death: a clinical perspective

Coronary artery disease has been demonstrated to conform to the principles of an epidemic disease. Therefore, the incidence of the occurrence of the disease is dependent in large part on "disturbances of human culture." These primarily include a cholesterol-rich diet, obesity, cigarette smoking, elevated blood pressure and sedentary life-style. It is gratifying that during the last quarter of a century, large segments of society in the United States have modified many of their adverse patterns of living. As a result, there has been a striking decline in both the incidence of the diagnosis of coronary artery disease and the frequency of premature death due to the disease process. Sudden cardiac death is frequently an unexpected first clinical manifestation of coronary artery disease and, despite heroic efforts, treatment of sudden death victims is frequently unsuccessful. Furthermore, progression of coronary artery disease, even in patients who present with angina pectoris or acute myocardial infarction, is unpredictable. Coronary arteriography, the "gold standard" used for evaluation, gives insight primarily into anatomy and ventricular function (under experimental conditions) existing at a given instant in time. Which lesions are serious and likely to progress are usually unknown, even to the most experienced angiographer. Therefore, surgical and catheter-directed therapeutic approaches are at best only "shotgun" or partial techniques. For these reasons, the principal and continuing therapeutic efforts to reduce the occurrence and control the ravages of coronary artery disease should be directed toward prevention. Such efforts should begin in early childhood and become a lifelong practice, one that all physicians, including the most procedure-dominated specialists, should personally adopt and teach.(ABSTRACT TRUNCATED AT 250 WORDS)

The pathological basis of angina pectoris

Coronary stenoses may be either concentric without any potential for variation in the degree of obstruction to flow or eccentric, where the cross-sectional area of the lumen can alter with vasomotor tone. Variable obstruction at eccentric stenoses is due to the retention of an arc of normal vessel wall opposite the plaque. Abnormal vasomotor responses are a feature of both human and experimental atheromatous coronary arteries; such an abnormality is likely to reflect endothelial dysfunction with loss or neutralization of endothelial-derived relaxant factor (EDRF). Structural studies show that superficial intimal injury, with migration of monocytes and focal endothelial denudation leading to deposition of small numbers of platelets on the exposed intimal collagen, is found in both experimental and human atheroma. Such endothelial changes may be responsible for arterial constriction leading to transient myocardial is-chemia in both patients with stable exertional angina and in those without overt ischemic heart disease. Larger coronary thrombi are associated with deep intimal tears or fissures that extend into the lipid pool of an atheromatous plaque. The resultant thrombi, large enough to be seen angiographically, project into the arterial lumen and are associated with un-stable angina of the abrupt-onset crescendo type. Nonoccluding mural thrombi in a coronary artery are a source of distal microemboli into the myocardium.

Morphologic features of unstable atherothrombotic plaques underlying acute coronary syndromes

Unstable angina appears to be a good clinical marker for rapidly progressing coronary artery disease. Pathologically, an unstable atherothrombotic coronary lesion, represented by a raised atherosclerotic plaque with ruptured surface causing variable degree of hemorrhage into the plaque and luminal thrombosis (rapid plaque progression), usually is present in patients at autopsy after a period of unstable angina. The thrombus at the rupture site may be mural and limited (just sealing the rupture) or occlusive, depending on the degree of preexisting atherosclerotic stenosis. An occlusive thrombus is seldom seen over ruptured plaques causing less than 75% stenosis (histologic cross-sectional area reduction), but it is found with increasing frequency when severity of stenosis increases beyond 75%. Most occlusive thrombi have a layered structure with thrombus material of differing age indicating an episodic growth by repeated mural deposits, and microemboli/microinfarcts are frequently found in the myocardium downstream to coronary thrombi, indicating intermittent thrombus fragmentation with peripheral embolization. Such a "dynamic thrombosis" (with or without a concomitant focal vasospastic phenomenon) at the site of an unstable (ruptured) atherosclerotic lesion obviously may lead to the other thrombus-related acute coronary events: myocardial infarction or sudden death. Accordingly, progression of unstable angina to myocardial infarction or sudden death should, in principle, be preventable by the correct timing of current available therapies aimed to prevent or eliminate (1) the chronic atherosclerotic obstruction, (2) the acute plaque disruption, (3) luminal thrombosis, and (4) vasospasm.

Two- to eight-year survival rates in patients who refused coronary artery bypass grafting

One hundred and fifty patients with coronary artery disease (CAD) who refused bypass grafting were followed prospectively from 2 to 8 years. Mean age was 57 +/- 8 (standard deviation) years. Ejection fraction averaged 70 +/- 14%. Eight percent of patients had 1-vessel CAD and 92% had multiple-vessel CAD. Medical treatment included propranolol, nifedipine, isosorbide dinitrate, dipyridamole and aspirin. Annual mortality was 0% for 1- and 2-vessel CAD and 1.3% for left main equivalent disease, 3-vessel and left main CAD. Treatment significantly reduced the incidence of stable and unstable angina. Fifty-two patients (34%) had a second hemodynamic study 4.2 +/- 1.3 years after initial evaluation. Stenosis progression or new significant obstructions (greater than or equal to 70%) in previously normal coronary arteries occurred in 61% of 123 arteries studied, whereas new occlusions were observed in 12% of the arteries. Nonfatal acute myocardial infarction incidence was 8%. No significant changes occurred in ejection fraction. In conclusion, proper medical treatment in selected patients with advanced CAD but preserved ventricular function is associated with good long-term survival and remission of symptoms, although progression of coronary atherosclerosis does occur in some patients.

Can coronary angiography predict the site of a subsequent myocardial infarction in patients with mild-to-moderate coronary artery disease?

To help determine if coronary angiography can predict the site of a future coronary occlusion that will produce a myocardial infarction, the coronary angiograms of 42 consecutive patients who had undergone coronary angiography both before and up to a month after suffering an acute myocardial infarction were evaluated. Twenty-nine patients had a newly occluded coronary artery. Twenty-five of these 29 patients had at least one artery with a greater than 50% stenosis on the initial angiogram. However, in 19 of 29 (66%) patients, the artery that subsequently occluded had less than a 50% stenosis on the first angiogram, and in 28 of 29 (97%), the stenosis was less than 70%. In every patient, at least some irregularity of the coronary wall was present on the first angiogram at the site of the subsequent coronary obstruction. In only 10 of the 29 (34%) did the infarction occur due to occlusion of the artery that previously contained the most severe stenosis. Furthermore, no correlation existed between the severity of the initial coronary stenosis and the time from the first catheterization until the infarction (r2 = 0.0005, p = NS). These data suggest that assessment of the angiographic severity of coronary stenosis may be inadequate to accurately predict the time or location of a subsequent coronary occlusion that will produce a myocardial infarction.

Development of significant coronary artery lesions in areas of minimal disease. A common mechanism for coronary disease progression

In 62 patients with coronary disease who had serial arteriograms without intervening coronary artery bypass graft (CABG) or percutaneous transluminal coronary arteriography (PTCA), progression was seen in 48 (77 percent). Progression from a normal or minimally narrowed lumen diameter to narrowing greater than or equal to 75 percent (to greater than or equal to 90 percent) in 21 patients) occurred in at least one vessel in 33 patients (69 percent) (group A, type I progression). Less striking progression and progression of initially more severe lesions was seen in 15 of 29 patients without type 1 progression (Group B) and in other vessels in 12 group A patients. Improvement in at least one vessel was seen in eight patients. There was no difference between groups A and B in the incidence of risk factors, intervening myocardial infarction, or recent unstable angina. It is concluded that progression of occlusive coronary disease occurs as commonly in areas of the coronary tree that are minimally diseased as in segments that are initially severely narrowed. Methods to stabilize the endothelium may prevent progression of coronary artery disease.

Angiographic progression of coronary artery disease and the development of myocardial infarction

There are few data on angiographic coronary artery anatomy in patients whose coronary artery disease progresses to myocardial infarction. In this retrospective analysis, progression of coronary artery disease between two cardiac catheterization procedures is described in 38 patients: 23 patients (Group I) who had a myocardial infarction between the two studies and 15 patients (Group II) who presented with one or more new total occlusions at the second study without sustaining an intervening infarction. In Group I the median percent stenosis on the initial angiogram of the artery related to the infarct at restudy was significantly less than the median percent stenosis of lesions that subsequently were the site of a new total occlusion in Group II (48 versus 73.5%, p less than 0.05). In the infarct-related artery in Group I, only 5 (22%) of 23 lesions were initially greater than 70%, whereas in Group II, 11 (61%) of 18 lesions that progressed to total occlusion were initially greater than 70% (p less than 0.01). In Group I, patients who developed a Q wave infarction had less severe narrowing at initial angiography in the subsequent infarct-related artery (34%) than did patients who developed a non-Q wave infarction (80%) (p less than 0.05). Univariate and multivariate analysis of angiographic and clinical characteristics present at initial angiography in Group I revealed proximal lesion location as the only significant predictor of evolution of lesions greater than or equal to 50% to infarction. This retrospective study suggests that myocardial infarction frequently develops from previously nonsevere lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Prediction of risk of anterior myocardial infarction by lesion severity and measurement method of stenoses in the left anterior descending coronary distribution: a CASS Registry Study

To assess the 3 year risk of anterior myocardial infarction in patients with left anterior descending coronary artery territory disease (30 to 100% stenosis), National Heart, Lung, and Blood Institute (NHLBI) Coronary Artery Surgery Study (CASS) registry patients were identified who were 1) medically treated, and 2) had evidence of viable anterior myocardium at the time of baseline angiography. Prospectively, 118 patients having an anterior infarction within 3 years of baseline angiography were identified from annual follow-up of 4,535 medically treated patients who had left anterior descending coronary artery disease and viable anterior myocardium. From the large residual pool of patients without infarction, 141 were randomly selected from a stratified matrix to represent the entire group. The maximal percent stenosis was estimated by the CASS multiple angiographers, by a current single observer rereading and by contemporary computer measurement techniques. Absolute lumen dimension was assessed by computer measurement. The 3 year risk of anterior infarction was 2% for patients with their most severe left anterior descending stenosis less than 50%, 6% for patients with one such stenosis greater than or equal to 50% and 11% for patients with two or more such stenoses greater than or equal to 50% (p less than 0.02). Stenoses of 90 to 98% had the highest (15%) 3 year risk of anterior myocardial infarction. The three methods used to measure maximal percent stenosis differed little with regard to their predictiveness. Absolute lumen dimension was less predictive of risk. These results may provide a more rational basis on which to base coronary revascularization decisions.

Relationship of angiographically defined coronary artery disease to serum lipoproteins and apolipoproteins in young survivors of myocardial infarction

The relationship of serum lipoprotein and apolipoprotein concentrations to angiographically determined coronary artery disease was investigated in 105 consecutive male survivors of myocardial infarction under the age of 45. Concentrations and composition of lipoproteins, lipid indexes, and nonlipid risk factors (tobacco consumption, hypertension, reduced glucose tolerance, and obesity) were related to a recently developed scoring system for semiquantitative estimation of diffuse coronary atheromatosis, as well as to the number and severity of significant coronary artery stenoses. The concentrations of cholesterol in very low-density lipoprotein (VLDL), low-density lipoprotein (LDL), and high-density lipoprotein (HDL), in combination with serum triglyceride or VLDL triglyceride level, comprised the best set of independent discriminatory lipid variables between patients and control subjects. In the patients, LDL cholesterol and apolipoprotein B levels showed strong relationships to the extent and severity of coronary atheromatosis but not to the number and severity of distinct coronary stenoses. HDL2 cholesterol concentration correlated inversely with the coronary atheromatosis score, whereas other variables reflecting HDL concentration and composition or VLDL lipids were not independently related to any of the coronary scores. The LDL triglyceride level, an index of intermediate-density lipoprotein (IDL) accumulation, was significantly correlated to the coronary atheromatosis score in univariate analysis. Nonlipid risk factors were correlated neither to coronary atheromatosis nor to severity of stenoses. Stepwise multiple regression analyses of data adjusted for age, cumulative tobacco consumption, and weight indicated that 18% of the variation in the coronary atheromatosis score could be accounted for by levels of apolipoprotein B. Addition of other lipoprotein variables or the nonlipid variables hypertension and glucose tolerance did not significantly increase the value of R2. When ratios of lipoprotein lipids and apolipoproteins were included in the regression model, the highest multiple correlation coefficient was obtained with the LDL/HDL cholesterol ratio alone (R2 = .22). The present data demonstrate the importance of elevated LDL cholesterol and apolipoprotein B concentrations for the development of coronary atheromatosis in young male survivors of myocardial infarction. The lack of correlations between the levels of lipoprotein lipids and serum apolipoproteins and the severity of coronary stenoses suggests that mechanisms other than disturbances of lipoprotein metabolism may be involved in the progression of more advanced coronary lesions.

Role of risk factor management in progression and regression of coronary and femoral artery atherosclerosis

The results of 3 recently completed studies usher in a new era in the treatment of coronary atherosclerosis and its sequelae. In aggregate, these results show that reductions in low density lipoprotein (LDL) cholesterol or reductions in the ratio of total to high density lipoprotein (HDL) cholesterol by either diet or drugs or both are effective in primary and secondary prevention of coronary artery disease (CAD). In the Lipid Research Clinics' Coronary Primary Prevention Trial, reducing levels of LDL cholesterol, regardless of whether the primary intervention was diet or drug, correlated with a reduction in CAD events. In the National Heart, Lung, and Blood Institute's Type II Coronary Intervention Study, CAD progression at 5 years was inversely related to a change in the ratio of HDL cholesterol to total cholesterol. In the Leiden Intervention Trial, cessation of coronary artery atherosclerotic lesion growth correlated with the ratio of total cholesterol to HDL cholesterol. Several trials now under way will test the effects of much more substantial reductions of LDL cholesterol (up to 50%) and increments in HDL cholesterol (up to 25%) on interrupting the progression or inducing the regression of coronary artery atherosclerosis. Even small reductions in the progression of coronary artery lesions or induction of their regression should produce major reductions in morbidity and mortality from CAD. The importance of secondary prevention also extends to patients after coronary artery bypass surgery, because the likelihood of graft occlusion is likewise related to the patient's lipid profile. Further, the importance of primary prevention of atherosclerosis through modification of lipids and lipoprotein cholesterol in the first-degree relatives of young victims of atherosclerosis cannot be overemphasized.

Angiographic evolution of coronary artery morphology in unstable angina

As previously reported in acute presentations of unstable angina, an identifiable characteristic coronary artery lesion has been found in about 70% of cases at coronary arteriography. This takes the form of an eccentrically placed convex stenosis with a narrow neck due to one or more overhanging edges or irregular, scalloped borders, or both. To study the evolution of lesions responsible for unstable angina, coronary artery anatomy and morphology on angiography were evaluated in patients with stable angina progressing to unstable angina. Group I comprised 25 patients with a history of stable angina who were restudied after an acute episode of unstable angina and Group II comprised 21 patients with little or no change in symptoms between catheterizations. Progression of coronary disease occurred in 19 (76%) of 25 patients in Group I compared with 7 (33%) of 21 in Group II (p less than 0.001). Of the 25 lesions with progression in Group I, 17 progressed to less than 100% and 8 to 100% occlusion. Eighteen of these 25 lesions in Group I were previously insignificant (less than 50% occlusion on the first catheterization). In contrast, of the eight lesions with disease progression in Group II, only two were previously insignificant while six showed at least 50% occlusion on the initial study. The eccentric lesion was seen in 71% of all lesions with progression to less than 100% occlusion in Group I, but it was not seen in any Group II vessel with progression.(ABSTRACT TRUNCATED AT 250 WORDS)

Plaque fissuring--the cause of acute myocardial infarction, sudden ischaemic death, and crescendo angina

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Coronary atherosclerosis and the bypass grafts: twenty-year follow-up of a case

A 44-year-old man was diagnosed as having coronary artery disease (CAD) by arteriography in 1964. In the subsequent 20 years, he has undergone seven angiographic studies and four coronary bypass operations. Close scrutiny of the clinical events and the angiographic studies in this patient offers important clues to the behavior of CAD and the bypass grafts, both internal mammary artery (IMA) and saphenous vein grafts (SVGs).