The heart: central to health

Celebrating the Heart by Making Connections

Prophets from several ancient religions taught that when the heart is well, the entire body is well, and that when the heart is sick, the human is sick.

Long before English physician William Harvey published his breakthrough understanding of how the heart and circulatory system work (1628), people worldwide revered this organ as both vital and central to the human condition.^[1] The Egyptians, Aztecs, and Indian Hindus all believed that the soul resided in it. Greek philosopher Aristotle imagined that thoughts were formed in the heart. The ancient Chinese agreed, which is why the word xin actually means both "heart" and "mind" in Mandarin.

Although these conclusions were not born of the scientific method, many would agree there is a definite truth to them: that the heart is central to human health and existence. Similarly, cardiology is central to the practice of medicine, with important clinical connections to nearly every other specialty. From the dermatologist to the radiologist, physicians across the board play a role in the cardiovascular health of patients.

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Age-related macular degeneration may be associated with heart disease

The Eyes: A Window to the Heart

A cardiac exam does not usually involve the eyes, but it certainly could.

Because blood vessels in the eyes can be easily visualized, ophthalmologists may be the first physicians to spot cardiac issues. When long-term vessel damage occurs in the body, it is rarely limited to one location. Hypertension can damage the sensitive ocular vessels, causing hypertensive retinopathy. Through funduscopic examination, a doctor may discover vascular wall changes, arteriolar constriction, optic disc edema, arteriovenous nicking, cotton-wool spots, flame-like hemorrhages, or hard yellow exudates, all of which can be telltale signs that a patient needs to see a cardiologist.^[2]

Cataracts are more common among those with coronary artery disease (CAD), says the American Academy of Ophthalmology. Even mild age-related macular degeneration is more prevalent in patients with CAD,^[3] so it may be wise for this group to have a cardiac check-up as well.

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Earlobe creases are negatively associated with cardiac health

What Ears Tell Us About the Heart

Not far from the eyes, another easy-to-spot indication of cardiac risk may show up on a patient's ears. As discussed in an earlier Medscape article, earlobe creases are negatively associated with cardiac health. These creases extend diagonally from the tragus to the auricle in an enfolding manner. Although some studies have questioned how strong the association is, others have established a definitive link, and one found that 71% of participants with an earlobe crease also had heart disease.^[4]

But that's not all. According to the American College of Cardiology, tinnitus, or ringing in the ears, can result from hypertension, arteriovenous malformations, carotid atherosclerosis, or other vascular problems, all of which could signal coronary heart disease. Even hearing loss, says the Better Hearing Institute, often corresponds with cardiac degeneration.

As a precaution, ENTs and otologists who observe these markers or impairments of any kind may want to provide a referral to a cardiologist.

On the flip side, ears may have a role in cardiac treatment because of their shared connection with the vagus nerve. In the past, the nerve could only be stimulated through surgery, but its cutaneous auricular branch, in the external ear, is being explored for noninvasive electrical stimulation to treat heart failure.^[5]

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Gingival plaque and receding, white gums tell a dark tale that may translate to poor heart health

What the Mouth Says About Cardiac Health

Clues in a patient's oral cavity may require a bit more intentional observation than those in the eyes or ears, but when it comes to heart disease risk, the mouth has a lot to say.

Gingivitis and periodontal decline—evidenced by pale, inflamed, or receding gums—correlate with higher levels of bacteria that are associated with increased cardiovascular disease, in part because they can raise levels of C-reactive protein, an inflammatory marker associated with arterial thickening. Scientists know that oral bacteria travel through the cardiovascular system and cause damage because they have isolated and identified those bacteria in atherosclerotic plaques.^[6] Open wounds and weak, fragile membranes in the mouth are also less resistant to other pathogens or toxins that can be transported through the blood and contribute to inflammation or cause endocarditis. The green mucus and phlegm that sometimes appear during a cold have also been linked to cardiovascular disease.^[7]

Patients who tend to their dental and periodontal health are more likely to have a strong and healthy heart. For patients who are not motivated by the promise of a gleaming smile, understanding the cardiac connection could provide that extra motivation.

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Cardiac hypertrophy in hyperthyroidism

Hormones and the Heart

Hidden from the physician's naked eye, the human endocrine system involves a delicate hormonal balancing act deep within the body, and it is intimately connected with cardiovascular health. In addition to problems associated with fluctuating sex hormones, an imbalance in the pancreas or thyroid glands can be a serious threat.

It is widely known that diabetes, caused by impaired insulin production and resistance to the hormone, makes patients much more likely to develop heart disease. In one study, those with severe diabetes (372,330 [10.7%]) had risks similar to those with prevalent coronary heart disease (182,760 [5.8%]).^[8]

This interrelationship can create a vicious cycle when patients develop pancreatitis stemming from the low-grade inflammation typical of cardiovascular disorders. Hypertension and ischemic heart disease in particular appear to increase the risk for acute pancreatitis.^[9]

In hyperthyroid patients, risks include sinus tachycardia and atrial fibrillation, whereas thyrotoxicosis can lead to pulmonary artery hypertension.^[10] Hypothyroid patients, though, often have much higher low-density lipoprotein (LDL) cholesterol levels, proportionate to their increased serum levels of thyroid-stimulating hormone (TSH). This is because both LDL-receptor expression and biliary excretion are altered by TSH.^[11]

If a patient is urinating more often than usual, feeling lethargic and gaining weight, experiencing palpitations or sweating, or has a rapid pulse or uncomfortable body changes, a hormonal panel may be in order to help detect associated heart disease.

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High blood pressure is a risk factor for both renal and heart disease

Interplay Between Kidneys and the Heart

Because the kidneys rely on a sufficient and uninterrupted blood supply in order to function normally, poor kidney function is sometimes the first indication of heart failure. Gradual decreases in the estimated glomerular filtration rate, for instance, may be a clue.^[12]

According to the National Institute of Diabetes and Digestive and Kidney Diseases, renal artery stenosis also has cardiovascular origins; it is typically caused by atherosclerosis. (Because smoking is a serious risk factor for atherosclerosis and heart failure, physicians who wish to might consider the evidence for how they can help patients quit tobacco use.)

As nephrologists strive to maintain renal function or reverse failure, they can weigh the possibility that underlying cardiac issues may be present, especially in patients who report a lower output of urine, edema, nausea, shortness of breath, or overall fatigue.

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Corresponding heart disease and allergic symptoms in men and women

Sneezing, Wheezing, and the Heart

Another subject worth exploring is the potential connection between allergies and coronary heart disease (CHD). In one study, Dr Jongoh Kim and colleagues^[13] discovered that people with wheezing had a 2.6-fold increased risk for heart disease compared with those who had no known allergies. Patients who reported rhinoconjunctivitis had a 40% greater risk. Although other studies have found an association between asthma and heart disease, this was the first significant research to link specific allergic symptoms to CHD risk.

Several mechanisms could be at play; allergic sensitivities are mediated by mast cells, histamines, leukotrienes, cytokines, and eosinophils, all of which correlate to some extent with either atherosclerosis specifically or CHD in general. Overall, the authors hypothesized that inflammation during the body's allergic response may thicken artery walls over time, eventually leading to heart disease.^[13]

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Cutaneous lesions of sarcoidosis (lupus pernio) may coincide with intrathoracic disease states

Dermatology and Heart Disease

As a Medscape review of dermatologic manifestations of cardiac disease points out, cardiovascular disorders as well as certain therapies for cardiac disease are associated with many cutaneous responses. Two of the five criteria for rheumatic fever in patients with acute carditis are skin-related, including subcutaneous nodules and chorea.

More generally, yellow fatty plaques that often appear on the inner eyelids (xanthelasma) can predict cardiovascular disease and death in the general publication, independent of other factors.^[14] Most patients visit a dermatologist seeking only cosmetic relief from these deposits, because they do not seem to cause any overt health problems. But dermatologists who understand the risks can be instrumental in identifying a relatively high risk for coronary heart disease, referring patients for diagnosis and treatment by a specialist.

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Cholesterol < 200 mg/dL, blood pressure < 120/80 mm Hg + glucose < 100 mg/dL = significantly lower cancer risk

Cancer and the Heart: Strongly Linked

It is broadly accepted that a healthy lifestyle will reduce both cancer and heart disease risk. A growing number of scientists are exploring whether cancer increases the risk of developing heart disease, and vice versa. Interest may have been piqued when scientists began to observe that the use of daily low-dose aspirin reduced the incidence of both cancer and heart disease.

In one study, biomarkers of heart health were strongly correlated with lower cancer rates: Patients who were not receiving treatment to alter these numbers, and who had a total cholesterol level < 200 mg/dL, blood pressure < 120/80 mm Hg, and a fasting serum glucose < 100 mg/dL, had a significantly lower cancer risk.^[15]

One study out of Austria revealed that cancer itself may damage the heart, even before the administration of treatments that are known to do so.

Oncologists are often racing against time to halt and eradicate malignancy, making it easy for concerns about cardiac health to take a back seat. It would be a shame, though, if a patient were to survive cancer only to succumb to heart disease.

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Blood and Cardiovascular Disease

Although it may seem obvious that blood and the heart are inextricably linked, the medical field has still not identified all the ways in which pathology and laboratory testing influence the progression of cardiovascular disease, protect patients from it, or help identify it.

When hematologists examine blood to identify biomarkers indicative of cardiovascular events, they typically search for cholesterol, apolipoprotein B, apolipoprotein A/apolipoprotein B ratio, fibrinogen, cardiac troponins I and T, cystatin C, and C-reactive protein.

This list will no doubt become longer as more comorbid disease connections are made, in particular those that are easily identified through blood testing. As a blood disease itself, anemia is one example. Its incidence also corresponds with that of heart disease, and it appears that anemia worsens existing heart failure by interfering with the heart's ability to repair itself. In one study, mortality was 3.9 times higher in anemic patients with heart failure than in those without anemia.^[16]

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Pulmonary Disease and Cardiac Health

It is because pulmonary and cardiovascular disease are so closely related that they are often referred to together as the "cardiopulmonary system." Not only do both systems reside in close proximity, but they have much else in common as well, including many of the same or similar risk factors and symptoms.

Chronic lower respiratory diseases, including chronic obstructive pulmonary disease (COPD), are a leading cause of death in the United States, not far behind cardiovascular disease. Respiratory diseases can often mimic cardiac pathology, sometimes even the pain of myocardial infarction. In addition to physical discomfort and suffering, both conditions can lead to dyspnea.

COPD results in less oxygen distribution to the bloodstream and organs, including the heart. Not surprisingly, one large UK study of patient medical records showed that those with COPD had cardiovascular disease at five times the rate of patients who did not have COPD.^[17]

Patients presenting with exacerbated COPD may be experiencing an atypical presentation of myocardial infarction. Because they tend to see their patients often, pulmonologists can play a significant role in getting patients to visit a cardiologist to improve heart health before a catastrophic event takes place.

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American Academy of Neurology: Patients of neurologists have better prognostic profiles for cardiac comorbidity

Neurology Linked to Cardiac Outcomes

Scientists know that stroke risk is increased by atrial fibrillation, arrhythmias, and other cardiac conditions. Beyond stroke, though, patients with a variety of neurologic disorders (NDs) experience a greater incidence of cardiovascular disease.

In one study, extensive data were gathered through a comprehensive survey of more than 60,000 participants nationwide. Investigators found that subjects with an ND were 1.74 times more likely to have heart disease than those without one.

Heart disease prevalence was 7.53% in patients with an ND, but only 4.48% in those without one (excluding those who had had a stroke).^[18]

As with other specialists who see their patients on a fairly regular basis, this puts neurologists front and center when it comes to making referrals to a cardiologist.

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The Impact of Emotions on Cardiac Health

Emotions can affect cardiac health.

Even if the jury is still out on the depth of physical damage that might be a direct result of stress or anxiety, perpetual adrenaline, rapid breathing, and excessive heart rates are probably not ideal for the heart. What researchers have found is that depression definitely increases the likelihood of coronary artery disease.

In one study of 1494 women older than 18 years, those with depressive feelings faced a threefold increase in the likelihood of a first cardiac event, after adjustment for other risk factors.^[19]

Medscape looked at the disabling and dangerous nature of major depressive disorder, noting that in the United States, the lifetime prevalence of depression is 12%-20%. This means that most physicians will probably encounter patients who are experiencing depressive symptoms. Inquiring about how patients are feeling, how they are choosing to cope with negative emotions, and providing referrals for appropriate treatment may help them with both mental health and heart health.

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Inflammatory factors in both RA and CHD

Rheumatoid Arthritis and Coronary Heart Disease

Rheumatoid arthritis (RA), an autoimmune disease that attacks the joints, is known to have a negative effect on the cardiovascular system. Medscape has discussed this connection at length in the past, including how physicians can coordinate treatment of both conditions.

In one study of 11,782 patients with RA, the prevalence of ischemic heart disease was 16.6%, compared with an incidence of 12.8% in 57,973 age- and gender-matched controls (P < 0.001).^[20] An analysis of several studies showed that patients with RA are at double the risk of experiencing a cardiovascular event when measured against those in the general population.^[21]

The most likely connection is an inflammatory response that affects the circulatory system as well as the joints, but other research has suggested that autoimmunity of all kinds may also raise the risk of developing coronary heart disease.^[22]

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Linked: Gut microbiota, lipid metabolism, and vascular diseases

Nutrition, the Microbiome, and the Heart

Nutritionists and cardiologists alike have long known that nutrition is an important component of heart health, from limiting salt, cholesterol, saturated fat, and calorie intake to eating heart-healthy fats and antioxidants. Fairly new to the scene, however, is science's understanding of the role that the human microbiome plays in heart health.

Millions of microbes are found in the gut, and the latest research estimates that the genome of that microbiota contains many times the number of genes that the human host does. These microbiota have a profound influence on digestion and nutrient absorption, wielding far-reaching influence over many aspects of health and disease—including composition of biofluids, such as the blood plasma that circulates to the heart.

In one of dozens of examples of how the microbiome dramatically influences cardiac and human health, trimethylamine N-oxide, often found in abundance in the digestive tract, is associated with hypertension^[6]; resveratrol, a component of red wine, eliminates this substance, possibly reducing atherosclerosis. The cardiac benefits of resveratrol are well known, but have only recently been understood in the context of the microbiome.

Although the science has a long way to go, some researchers are hopeful that manipulating the microbiota through prebiotics, probiotics, and overall nutrition might be an even more significant means of preventing or treating heart disease in some people.

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One mutated gene, SLCO1B1, has been associated with high levels of blood fatty acid, a significant predictor of future heart failure

Genetics and Genomics in Cardiology

One of the most recent and dramatic advances in cardiology has been the advent of genomic medicine.

Through genetic and genomic research, cardiogenomic profiles of individuals with (and those without) heart disease are growing stronger every day. These disciplines are constantly identifying new genes and genetic combinations that can predict, sometimes with astounding clarity, not only a patient's heart disease risk but also influential cofactors, and the most effective treatments.

Researchers are continuously identifying single-gene mutations that have relatively large effects on individual phenotypes, facilitating therapies for cardiomyopathy, arrhythmias, and aortic diseases that stem from genetic factors.

Genetic mutations may contribute to such diseases as premature myocardial infarction, dilated and hypertrophic cardiomyopathy, heart failure, arrhythmogenic right ventricular dysplasia, the long QT syndrome, and aortic aneurysms.^[23] Although scientists have come a long way in identifying risk factors and biomarkers, with genomic medicine comes the possibility of more accurate predictions and testing for heart attacks before they occur.

There is something to be said for physician awareness of how a patient should be monitored, including in terms of determining dosages or selecting a medication. One case in which genotyping has worked well is with clopidogrel (Plavix®), a drug that prevents clots from forming within a stent. About one third of the population has a gene variant that makes it harder for their livers to activate the drug. These patients must either have a higher dose of clopidogrel or be put on a different antiplatelet medication.^[24]

Similarly, some people carry a gene that causes potentially dangerous muscle reactions after ingestion of statins.^[25] These patients should never take statins and should discuss other cholesterol treatments with their physician.

As genomic medicine continues to advance cardiac care, knowledge will empower physicians in new and unprecedented ways.

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Class II histone deacetylases to regulate gene expression, reprogram heart failure

Epigenetics: The Future of Cardiovascular Treatment?

Although epigenetics is not a brand-new concept, it is not something that all physicians have been long familiar with, and it has evolved from a science of controlling gene expression and signaling pathways to manipulating heritable changes. Epigenetics primarily involves DNA methylation, histone modifications, and micro-RNA–based mechanisms, three distinct but interrelated processes that control gene expression.

Scientists are now looking at how internal and external environments turn human genes on and off to determine whether people have coronary artery disease, heart failure, cardiac hypertrophy, and diabetes, and if so, how they can be most effectively treated.^[26]

Epigenetics has been explored for use in reducing vascular inflammation; moderating the development of cardiovascular disease and its progression; and understanding why certain risk factors, such as smoking and diabetes, affect some patients more than others.

Cardiovascular disease is a worldwide epidemic, both in terms of public health and healthcare costs. Cardiology does not exist in a vacuum, and silos in this field could have tragic results. All body systems may be involved in or provide clues about cardiac function. In the near future, cardiovascular health will depend on the most complex, integrated relationships between medical and scientific disciplines.

In the meantime, physicians from every specialty have a major role to play, in both influencing and identifying this disease and all its manifestations.

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