CAD vs. CHD
There are semantic subtleties between terms for coronary artery disease and coronary heart disease:
- Coronary artery disease (CAD): is often used synonymously with coronary heart disease (CHD), but CHD includes both the pathologic process (the atherosclerosis in CAD) and the angina, ischemia, myocardial infarction, and mortality that come from CAD.
- Cardiovascular disease (CVD): implies disease in the entire arterial circulation, and as such, includes stroke, claudication, and limb ischemia.
Causes of and Risk Factors for CAD
- Obesity/metabolic syndrome
- Sedentary lifestyle
- Chronic renal disease
Family history is an independent risk factor for CAD, but when combined with any of the above provocations, augments the total, global risk exposure.
When there is atherosclerotic narrowing of the coronary arteries, there is reduced blood flow (oxygenation) to heart tissue. The energy demands of the heart are large, and any decrease in the blood supply can outpace the energy needs, causing ischemia.
Ischemia Can Occur Due to:
- Decreased supply of blood (atherosclerotic coronary narrowing):Atherosclerotic obstruction (the most common cause), coronary artery vasospasm, embolism, and arteritis. Less common causes are anemia, hypotension/shock, and postprandial “steal” angina (redistribution of blood away from diseased coronary arteries to those that are normal).
- Increased demand (exertion): Vigorous exertion/exercise, increased sympathetic tone (stress), tachycardia, hypertension, or ventricular hypertrophy.
Ischemia in any muscle, including the heart, causes pain. Such pain from coronary artery disease is called angina pectoris:
- Stable angina: chest discomfort that is predictable and reproducible with exertion and can be relieved with rest (decrease in energy demand) or nitroglycerin (vasodilator–increase in blood supply).
- Unstable angina: does not follow the typical stable angina patterns. It occurs more frequently and is more severe, can occur at rest, and is not relieved by rest or nitroglycerin.
Angina without chest pain, but with other symptoms, is called “anginal equivalent,” and includes exertional shortness of breath, nausea, diaphoresis, and fatigue. Angina without either chest pain or anginal equivalent symptoms is called “silent angina”. In transitioning from stable angina to unstable angina, a CAD patient has clearly crossed a dividing line into the Acute Coronary Syndrome.
Acute Coronary Syndrome (ACS)
Acute Coronary Syndrome is a spectrum of three types of coronary artery disease:
- Unstable angina (UA)
- Non-ST segment (ECG) elevation myocardial infarction (NSTEMI heart attack)
- ST segment (ECG) elevation myocardial infarction (STEMI heart attack)
The severity of CAD is a continuum in the intolerance of heart muscle to provocations from decreased supply and/or increased demand. At some point, ischemia will become unstable (stable angina to unstable angina) and infarction will occur with or without ST elevations on ECG (indicators of cell death).
How Is Coronary Heart Disease Diagnosed?
Coronary artery disease (CAD), from atherosclerotic narrowing of the coronary arteries and coronary heart disease (CHD), which includes the progression of angina and signs and symptoms of ischemia or worse, are first suspected with a history and physical.
A history can glean a family tendency toward heart disease and explore the patient’s response to exertion, stress, and other challenges. It can also identify comorbidities that tend to make CAD worse: hypertension, smoking, diabetes, renal disease, medications, and illicit IV drug abuse.
It can also render the pertinent negatives: a history of chest pain must exclude other conditions that can mimic CAD, such as gastritis, esophagitis, pleuritic pain and pneumonia, and diaphragmatic hernia. It is not only important to list the positives, but these negatives, as well, to give an inclusive and complete perspective.
A CAD patient will require additional considerations in the physical exam than others without a cardiac history or cardiac symptoms. Vital signs will identify hypertension, pulse can determine arrhythmias, examination of the jugular veins in the neck can identify heart disease originating from lung conditions, etc.
The familiar wave pattern of an ECG can be assessed. Ischemia renders identifiable patterns in the ECG recording. The 12-lead ECG, which gives a 360° view of the heart, can identify where ischemia is located and can even assign a patient to which part of the acute coronary syndrome he or she is in.
Cardiac ultrasonography can identify structural qualities of the heart as well as the flow dynamics. The presence of thrombi that can predict the risk of stroke or peripheral ischemia can be established and valvular heart disease can be identified.
Stress testing is a way of evaluating the delicate balance between decreased supply (atherosclerotic narrowing) and increased demand (exertion) and at which point a patient is at risk for ischemia. It can be done mechanically with a treadmill or chemically with medication. It uses concomitant use of ECG and possibly echocardiography to complement its accuracy.
- Transthoracic Echocardiography (TTE): Evaluation of Left Ventricular Systolic Function. TTE is the usual method of evaluating left ventricular function. This can be used to determine what type of medical therapy is best, whether interventional or surgical therapy is warranted, or to make recommendations about activity level, efforts at rehabilitation, or employment restrictions.
Coronary angiography is an invasive radiological procedure with risks, so is used when the benefits clearly outweigh these risks. Is indicated for patients whose angina symptoms interfere with their lifestyle or patients who satisfy high-risk criteria:
- Previous cardiac arrest
- Previous life-threatening ventricular arrhythmia with heart failure
- Decreased left ventricular systolic function
- Unsatisfactory quality of life due to angina
The results of coronary angiography allow a risk-vs-benefit decision into the prudence of revascularization via bypass or angioplasty.
How Can I Manage Coronary Artery Disease?
The management and treatment of coronary artery disease is dependent on several factors:
- Patient quality of life
- Risk of progression that can include sudden cardiac death
- Amount of ischemia
- Amount of cardiac reserve
- Exercise via a gradual introduction and supervised increase will improve exercise tolerance as well as the psychological well-being that comes from it to counter depression associated with disability
- Stress reduction
For those with stable angina and stable ischemic heart disease, medical treatment consists of:
- Beta blockers, which reduce heart rate and contractility to lessen, delay, or avoid anginal symptoms or the crossing over the threshold of ischemia into acute coronary syndrome
- Calcium channel blockers, in combination with beta blockers or instead of failed beta blockers, to cause coronary vasodilation and reduce contractility (work demand) of the heart
- Nitrates, the first-line therapy for acute angina and which can also be used preventatively
- Sodium channel blockers, to reduce ventricular tension and myocardial oxygen consumption, producing myocardial relaxation that lessens the severity and frequency of anginal symptoms
The ischemia that results from decreased blood supply to the myometrium and one’s vulnerability to increased demand can affect one’s quality of life enough to warrant revascularization. Indications include activity limitations from CAD or with anatomical abnormalities for which medical therapy is ineffective.
Revascularization can be done via:
- Coronary artery stenting via percutaneous coronary intervention (PCI) for single-vessel disease. Pre-stent dilation may be indicated depending on the type of stent(s) used. Adjunctive therapy requires anticoagulation therapy
- Balloon angioplasty PCI, less used due to its need for repeated applications
- Coronary artery bypass grafting (CABG), used for multi-vessel disease and in diabetics
Prevention of Coronary Artery Disease
The concept of prevention in coronary artery disease (CAD) involves two general considerations:
- Prevention of CAD by preventing the conditions that promote atherosclerosis of the coronary arteries
- Prevention of CAD progression, quality of life impairment, and sudden cardiac death
Prevention of CAD
Prevention of the causes of CAD, usually atherosclerosis, is prevention of:
- Hypertension: Diet and weight management will improve hypertension, and, if necessary, antihypertensive medication can be added.
- Dyslipidemia: Elevations in LDC-cholesterol or lower HDL-cholesterol, and elevated triglyceride levels, contribute to the plaque formation of atherosclerosis, so using statin drugs are very helpful in preventing both the dyslipidemia and the CAD it promotes, as well as preventing peripheral arterial disease that can jeopardize lower extremity and another systemic perfusion.
- Smoking cessation: The causative relationships between smoking and atherosclerosis, smoking and CAD, and atherosclerosis and CAD is well established. Smoking may not be the sole cause of CAD, but it is a major cause of it, as well as a significant risk for COPD, emphysema, malignancies, and hypertension, all of which can contribute to CAD independent of the smoking factor.
Prevention of CAD Progression
The time to pursue prevention strategies in CAD is before it ever develops. Routine cardiac exams, especially for the elderly, diabetics, and those with concerning symptoms (chest pain, presyncope, or syncope), should be part of everyone’s “well care” maintenance.
Once CAD is diagnosed, it is important to determine whether the angina is stable or unstable. Stable angina can benefit from medical therapy and from lifestyle changes that impact atherosclerosis favorably (diet, weight management, exercise). Unstable angina crosses a threshold into an acute coronary syndrome, and with it, a higher risk for serious life-threatening developments. If medical management alone does not suffice, revascularization interventions are indicated to optimize one’s chance of long-term survival.