Acute coronary syndrome
Plaque erosion occurs more frequently in younger women than in men. Unlike in plaque rupture, the plaque in erosion has a thickened fibrous cap and minimal calcification.Women present more often than men with NSTEMI, rather than STEMI
Microvascular coronary dysfunction
Typical angina with positive ischemic stress testing in the absence of significant epicardial disease. Independently associated with acute cardiovascular events
Stress cardiomyopathy
Cardiac event mimicking AMI in the absence of obstructive CAD, typically with mid- and distal left ventricular akinesis. Predominant in postmenopausal women
Spontaneous coronary artery dissection
Up to 30 % of cases are peripartum, thought to be related to increased hemodynamic stress on coronary arterial wall
Pregnancy-related MI
Pregnancy increases risk of AMI by three- to fourfold. Most common causes are coronary artery dissection, atherosclerosis, and thrombus
Combined oral contraception and CHD
COC is contraindicated in women with known ischemic coronary disease, current smokers of >15 cigarettes/day, uncontrolled hypertension, and those with multiple risk factors for CHD
Atherosclerosis and acute coronary syndrome: Atherosclerotic heart disease is initiated by chronic minimal injury to the arterial endothelium due to patterns of blood flow. Over time there is subintimal and medial accumulation of macrophages and lipids. This leads to alterations in platelet function, growth factor release, smooth muscle cell proliferation, and the development of arterial plaques [34]. Established risk factors for CHD potentiate the initial endothelial injury and increase the rapidity of progression of atherosclerotic plaques [35]. These plaques can cause stable ischemic heart disease or the more abrupt phenomenon of acute coronary syndrome (ACS), comprised of unstable angina, AMI, and sudden coronary death (Chaps. 19 and 25).
Most cases of ACS are due to sudden luminal thrombosis, which in up to 70 % of cases is due to plaque rupture [36–38]. The primary features of a plaque vulnerable to rupture are a large lipid core, a high macrophage content, and a thin fibrous cap [35]. In 25–30 % of ACS, the thrombosis is due to superficial erosion of a plaque that is rich in smooth muscle cells and proteoglycans with a thickened fibrous cap and minimal calcification [39, 40]. Plaque erosion is more common in women than men and is the primary cause of acute coronary thrombosis in women less than 50 years of age with sudden coronary death. In women older than age 50, plaque rupture remains the dominant mechanism [39].
It is unknown why younger women are more prone to plaque erosion. It has been proposed that estrogen plays a role in stabilizing atherosclerotic plaques via changes in the fibrous cap and the composition of the plaque core, leading to less vulnerable plaques in younger women [41]. The mechanism that leads to plaque erosion is unknown; theories include coronary vasospasm as an inciting event [36] and a higher thrombogenic potential in women. Smoking is an independent risk factor for plaque erosion [40, 42].
Microvascular coronary dysfunction: There are also sex differences in the coronary microvasculature. The phenomenon of typical anginal symptoms with positive ischemic stress testing in the absence of significant epicardial disease has been described as early as the 1960s [43]. Labeled “syndrome X” in 1973 [44], this entity has become further defined as microvascular angina or microvascular coronary dysfunction (MCD) when there is evidence of vasomotor abnormalities. In MCD the coronary microcirculation, which regulates myocardial perfusion, does not adequately respond to changes in myocardial oxygen requirements [45] due to altered endothelial tone, altered response to vasodilator stimuli, and adverse structural changes [46].
Women referred for coronary angiography for evaluation of chest pain are more likely than men to have angiographically normal epicardial coronary arteries [47]. In the National Heart, Lung, and Blood Institute (NHLBI) Women’s Ischemia Syndrome Evaluation (WISE) study, up to half of such women had evidence of microvascular dysfunction [48]. Once thought to be a benign diagnosis, coronary endothelial dysfunction is independently associated with acute cardiovascular events [49], with an annual adverse cardiac event rate of 2.5 % [46].
The sex difference in MCD is not well understood. Hypotheses include relative estrogen deficiency in the perimenopause and menopausal periods and higher levels of chronic inflammation in women as causes of endothelial dysfunction [50].
Stress cardiomyopathy: Also referred to as takotsubo cardiomyopathy, transient apical ballooning, or broken heart syndrome, stress cardiomyopathy is a cardiac event mimicking AMI in the absence of obstructive atherosclerotic coronary artery stenosis. The distinctive and most common contraction abnormality is mid- and distal left ventricular akinesis or dyskinesis with preserved basilar function, but alternate wall motion abnormalities including right ventricular dysfunction have been described [51]. There is commonly a stressful trigger, either emotional or physical, though infrequently no trigger is identified. The incidence is estimated to be 1–2 % of patients presenting with AMI [52]. Case series document up to a 90–96 % female predominance with a mean age of 68 years [51].
The pathophysiology is not well understood. Proposed mechanisms include catecholamine toxicity and excessive sympathetic stimulation, but elevation in circulating catecholamines has not been a consistent finding. Other potential mechanisms include an increased density of sympathetic nerve endings at the LV apex, multivessel epicardial spasm, or microvascular dysfunction, possibly related to sympathetic hyperactivity. As stress cardiomyopathy is predominant in menopausal women, it has been theorized that estrogen plays a protective role on coronary vasoreactivity, in part via vasodilatory properties, and the decrease of estrogen in menopause leaves the myocardium more susceptible to endothelial dysfunction [52].
Spontaneous coronary artery dissection (SCAD): SCAD is another cause of ACS occurring primarily in young, healthy women. First described in 1931, it is a rare clinical phenomenon, its incidence ranging from 0.1 to 1.1 % [53, 54]. The mean patient age is 35–45 years, and over 70 % of cases occur in women. SCAD can be categorized as nonatherosclerotic or atherosclerotic in origin. Nonatherosclerotic associations include the peripartum state, extreme exercise, connective tissue disease such as fibromuscular dysplasia, Marfan’s syndrome and Ehlers-Danlos syndrome, various vasculidities, and idiopathic [38, 55, 56].
Up to 30 % of cases occur peripartum, most frequently in women without risk factors for CHD. It is proposed that peripartum SCAD is due to the normal physiology of pregnancy, in which cardiac output and total blood volume are elevated and estrogen levels are higher. The increased estrogen causes hypertrophy of smooth muscle cells with loosening of the intercellular matrix, which in the setting of increased cardiac output and blood volume places increased stress on the coronary arterial wall [57].
Pregnancy-related AMI: Pregnancy increases the risk of AMI by three- to fourfold in age-matched women, though it remains a rare event, occurring in 3–10 per 100,000 deliveries [58]. The anterior wall of the left ventricle is most commonly affected in pregnancy-associated AMI; serious complications such as cardiogenic shock and ventricular arrhythmias are not uncommon.
The most common etiology of AMI in pregnancy is coronary artery dissection (up to 43 %), followed by atherosclerotic disease (27 %) and thrombus without underlying atherosclerosis. Vasospasm and stress cardiomyopathy are other presenting causes [59]. Women tend to present with AMI in the third trimester or postpartum period, though atherosclerotic-related AMI can occur any time during pregnancy.
The pathophysiology of coronary dissection in pregnancy is thought to be due to hormonal changes, which lead to alterations in the endothelium, compromising the integrity of the arterial wall while under the hemodynamic stresses of pregnancy. The increased risk of coronary thrombosis in the absence of atherosclerosis is attributed to the hypercoagulable state of pregnancy. Vasospasm is theorized to be secondary to increased catecholamine release and an increase in vascular reactivity to angiotensin II [59, 60] (Chaps. 60 and 61).
Combined oral contraceptive (COC) use and CHD: COC with estrogen and progesterone causes an increased risk of AMI. A recent Danish cohort study based on data from national registries shows a relative risk for myocardial infarction of up to 4.3 for the highest doses of estrogen. This risk declines with lower doses of estrogen and rises dramatically with age and for women with other risk factors for CHD [61, 62]. The risk to young, healthy women, especially at the lower doses of estrogen currently used, is negligible. Due to this link, COC is contraindicated in women with known ischemic coronary disease, current smokers of >15 cigarettes/day, uncontrolled hypertension, and those with multiple risk factors for CHD [63].
The link between COC and AMI is not well understood. Newer data show the increased risk does not persist when the use of COC is stopped, suggesting that atherosclerosis is not the mechanism of increased risk [64], but rather that a thrombotic predisposition is at play.
21.3 Coronary Heart Disease in the Elderly
21.3.1 Background Information
Cardiovascular disease is the major cause of morbidity, mortality, and health-care utilization for the elderly [65]. The burden of CHD rises with the age of a population, both in prevalence and severity of disease. By age 80 men and women have a similar prevalence of symptomatic CHD, up to 20–30 % [66]. While men and women over the age of 80 years comprise only 5 % of the population, 20 % of MI-related hospitalizations and 30 % of MI-related hospital deaths occur in this population. Elderly adults have more left main coronary disease, multivessel disease, and coronary calcification compared to younger patients [67]. Despite this increased burden of CHD, elderly persons are significantly underrepresented in cardiovascular research studies. Limited trial data leads to uncertainty of the benefits and risks of pharmacologic and invasive treatments for elderly CHD patients, resulting in a disproportionately low use of modern cardiovascular advances in this population.
21.3.2 Risk Factors for CHD in the Elderly
For underlying reasons that are poorly understood, it appears that coronary atherosclerosis is inevitably associated with aging. In the absence of a fatal illness such as infection or malignancy, CHD seems the main determinant of the maximal life span of a human being. This is supported by the results of postmortem examinations of centenarians, all of whom died of cardiovascular causes [68]. The aging process is frequently defined as a progressive decline in the ability of an organism to withstand environmental stressors. Thus, aging of the cardiovascular system likely involves the combination of prolonged exposure to pro-atherogenic factors and a reduction in the anti-atherosclerotic function of the vascular wall. It is recommended to initiate primary prevention of cardiovascular disease early in life for exactly this reason; nevertheless, it is never too late to institute primary or secondary CHD prevention strategies.
Established cardiovascular risk factors for the general population are similarly relevant for risk assessment in the elderly. Modification of the traditional cardiovascular risk factors of cigarette smoking, physical inactivity, diabetes, hypertension, obesity, and abnormal lipids provides benefits of secondary prevention for elderly adults as well as the younger population. Owing to their increased absolute CHD risk, beneficial interventions selectively advantage elderly patients [67]. Primary prevention efforts are likewise similar for elderly patients but with attention to the higher rates of adverse pharmacologic events at elderly ages. For example, the 2014 JNC eight guidelines for hypertension recommend a treatment goal blood pressure of <150 mmHg/90 mmHg for men and women over age 60 given the lack of evidence for a benefit with more aggressive blood pressure reduction and a potential for adverse drug effects with antihypertensive medications [69]. Similarly, the 2013 guidelines on cholesterol management include no definitive recommendations on statin therapy for primary prevention in people over age 75 due to a lack of clinical evidence [70]. These are discussed in Chaps. 2 and 30.
Some age-specific CHD risk factors should be considered when evaluating the elderly population.
Arterial stiffness: Aging is associated with structural and functional changes in the vascular wall. These include degradation of elastin, smooth muscle necrosis, and increases in collagen and calcification, leading to thickening of the arterial wall. The end result is decreased vascular distensibility and elevated arterial stiffness [71, 72]. These changes contribute to the development of systolic hypertension, increased left ventricular afterload, left ventricular hypertrophy, increased myocardial oxygen demand, and impaired coronary perfusion.
The age-related change of arterial stiffness is an independent predictor for CHD events, as well as for other manifestations of cardiovascular disease and mortality [73–75]. Arterial stiffness can be reduced by nonpharmacologic and pharmacologic interventions including exercise, heart healthy dietary changes, and blood pressure control; research is ongoing as to whether reduction in arterial stiffness independently confers CHD event risk reduction [75]. A surrogate for arterial stiffness is aortic pulse wave velocity, which can be measured noninvasively.
Frailty: Frailty is a clinical condition frequently seen in the elderly population. Its estimated prevalence ranges from 10 to 60 % depending on the population studied [76]. While frailty has been increasingly investigated, a universal definition has not been established. It is generally accepted as a syndrome characterized by decreased physiologic reserve and increased vulnerability to stressors, such that even minor stressors can lead to disproportionate declines in health status [77].
Frailty is a risk factor for the development of CHD and for CHD-related mortality; likewise, CHD and even subclinical cardiovascular abnormalities can be associated with frailty and the development of frailty [78]. A common underlying biologic pathway has been proposed linking the disease processes of CHD and frailty. Dysregulation of the hormonal, immune, and endocrine systems with a resulting increase in inflammatory cytokines has been hypothesized as one possible common mediating pathway [76]. Adverse behaviors related to frailty such as physical inactivity can also act as barriers to the promotion of anti-atherogenic lifestyle changes.
Lipids: The effect of lipid profiles on the cardiovascular risk of the elderly appears to differ from that of a younger population. Neither high total serum cholesterol nor high LDL levels predict cardiovascular mortality in the very elderly population (>85 years), but low HDL levels remain a risk factor for CHD death [79, 80]. LDL likely remains a risk factor for CHD in the elderly, but high LDL levels lose predictive value for CHD mortality due to an association between low LDL levels and cancer [81]. This association is not well understood. Research has not implicated statins nor genetically low LDL cholesterol levels as causative of this relationship [82, 83].
The 2013 ACC/AHA guidelines for statin therapy recommend moderate-intensity statin use for those greater than 75 years of age with clinical CHD. Due to limited randomized controlled trial data on patients older than 75 without clinical CHD, no definitive recommendations for statin therapy were made for primary prevention [70].
Depression: Depression is a common illness in the elderly, with depressive symptoms occurring in 19–30 % of elderly people. Depressive symptoms have been identified as an independent risk factor for the development of CHD in elderly Americans, with an increased risk of up to 40 %, as well as an increase in all-cause mortality [84]. Proposed biologic mechanisms include increased sympathetic stimulation, platelet activation and levels of fibrinogen, and adverse changes in lipid metabolism. Other associated behaviors that likely contribute to development of CHD and adverse outcomes include physical inactivity and medication nonadherence, both of which are higher in depressed patients [85].
21.3.3 Pathophysiology of CHD in the Elderly
The primary etiology of CHD in the elderly is coronary atherosclerotic disease. While the pathophysiology of atherosclerosis is the same at younger and elderly age, particular features contribute to more extensive disease and worse outcomes in the elderly (Table 21.2).
Table 21.2
Unique features of CHD in the elderly
Diagnostic delay of CHD | Atypical symptoms; presence of confounding factors including atypical presentation and multiple comorbidities |
Extent of CHD | Elderly are more likely to have more diffuse and severe atherosclerotic disease and more calcific atherosclerosis. More likely to present with NSTEMI than STEMI |
Pharmacotherapy | Drug-drug interactions and alterations in drug metabolism can limit medical treatment options |
Revascularization | The lack of a large body of evidence for interventions in the elderly and very elderly can lead to a treatment gap |
21.3.3.1 Diagnosis of CHD
The diagnosis of CHD at elderly age can be complicated by atypical presentations of CHD and by other cardiac or noncardiac conditions that can produce myocardial ischemia and angina. Elderly patients with ACS are more likely to present with atypical symptoms including atypical chest pain, dyspnea, diaphoresis, nausea, and syncope [86, 87]. Decreased physical activity, orthopedic ailments, sensory deficits such as hearing and vision loss, cognitive decline, and other chronic diseases such as heart failure, lung disease, cerebrovascular disease, and neuromuscular disorders can all mask or confuse symptoms. While elderly patients develop ACS due to plaque rupture, they are more likely than younger patients to develop ACS due to type II myocardial infarction, i.e. MI due to an ischemic imbalance [88]. Comorbidities that lead to a mismatch between myocardial oxygen supply and demand include aortic valve disease, hypertensive heart disease, cardiac arrhythmias, anemia, and acute illness in the setting of atherosclerotic disease, all of which are more prevalent in an elderly population [89]. Attention to the underlying etiology is crucial in management of type II MI. These factors contribute to a delay in diagnosis of both chronic CHD and acute complications of CHD, which leads to worse outcomes due to the lack of timely and appropriate interventions [88].
21.3.3.2 Treatment Concerns
Pharmacotherapy: Elderly patients have altered pharmacokinetic and pharmacotherapy responses to drugs. This is due to changes in drug distribution, metabolism, and excretion, as well as physiologic changes related to aging that affect end-organ responsiveness to medical treatment [90]. Compounding the altered pharmacology of drugs in the elderly is the frequency of polypharmacy, which can lead to significant drug-drug interactions. While most cardiovascular drugs can be used safely in the elderly, caution must be applied, especially to drugs with a higher adverse effect profile, such as anticoagulant and antithrombotic agents, antihypertensives, and diabetic therapies [90, 91]. While judicious use of cardiovascular drugs in the elderly is imperative, this should not interfere with evidence-based treatments for CHD.
Revascularization: The cumulative burden of more years lived with cardiovascular risk factors is not without consequence. As described above, the elderly are more likely to have more diffuse and severe atherosclerotic disease and more calcific atherosclerosis [92]. While earlier data from the 1980s and 1990s showed that percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG) had significantly higher rates of procedural complications in the elderly with less successful outcomes compared to younger patients [93, 94], more current data show both an increase in rates of revascularization in the elderly and the very elderly and declining interventional risks [95, 96].
Elderly patients can benefit from revascularization compared to medical management in many domains, including survival, major adverse cardiac events, functional capacity, quality of life, and health status [94, 97]. Newer techniques such as the transradial approach for catheterization and hybrid coronary revascularization have been shown to be safe and effective in the elderly, with lower periprocedural complications compared to older interventional techniques [98, 99]. Discussions of treatment strategy in the elderly should utilize a patient-centered team approach with an understanding of patient goals and expectations, and an appreciation that patients with the most severe disease often derive the most benefit from revascularization strategies.
21.4 Concluding Remarks
Heart disease is the leading cause of death in the United States for both men and women. Research in cardiovascular disease has focused mainly on nonelderly men, often excluding women and the elderly and very elderly. We are beginning to appreciate the ways in which these populations differ in both risk factors for and manifestations of CHD. Traditional cardiovascular risk factors are relevant, but there are other risk factors pertaining uniquely to either women or the elderly that must also be investigated when evaluating an individual’s cardiovascular risk. CHD can be manifest as atherosclerosis in women and the elderly but can also present in less common ways, particularly in these populations. An increased awareness of these issues can lead to improvement in diagnosis and treatments and realignments in research to advance our understanding of CHD and eventually improve outcomes for all populations.
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