Recognition of Clinical Subsets

Walk through angina pectoris
In majority of patients with obstructive atherosclerotic CAD, the intensity of angina increases with continued physical activity. A subset has so called walk through angina. In this clinical situation, the patient experiences angina at the beginning of physical activity (e.g. walking, gardening, climbing, and short running) but the angina then disappears despite continuation of the activity. The precise underlying mechanism of walk though angina remains unclear, although an increase in coronary vascular tone and therefore a spontaneous reduction in coronary blood flow at the beginning of the exercise have been implicated. Opening of collaterals might also play a role in this situation.

Mixed (Variable Threshold) Angina Pectoris
The essential clinical feature of mixed angina is a substantial variation in the degree of physical activity that induces angina. These group of patients may also experience rest or nocturnal angina on certain occasions. Angina may also occur on exposure to cold, during emotional stress, or after meals. Dynamic vasoconstriction which superimposed on fixed atherosclerotic coronary artery obstructions has been postulated as the mechanism for the variable exercise threshold.

Nocturnal Angina Pectoris
In clinical practice, two types of nocturnal angina are observed. Some patients experience angina within an hour or two after sleeping. The mechanism of angina in this group of patients is likely to be an increase in venous return and hence increased intra cardiac volume with a resulting increase in myocardial oxygen requirements. Other group of patients with nocturnal angina experience chest discomfort much later, in the early hours of the morning. In this group of patients, a primary reduction in coronary blood flow owing to increased coronary vascular tone, more likely related to different stages of sleep, has been postulated as the potential underlying mechanism.

Postprandial Angina Pectoris
Angina can occur after meals without any ordinary physical activity because of increased coronary vascular tone and a primary decrease in coronary blood flow. However, postprandial angina may occur only during physical activity after meals because of an associated increase in myocardial oxygen demand. Postprandial angina is almost always associated with significant atherosclerotic coronary artery disease.

The Metabolic Syndrome (Syndrome X)
Syndrome X is defined as the presence of typical anginal chest pain with angiographically normal coronary arteries. Although the syndrome originally referred to patients in whom the chest pain was due to noncoronary causes, the current, stricter definition limits it to those patients who appear to have true myocardial ischemia despite epicardial coronary arteries that are normal or nearly so on coronary angiography.

To establish the diagnosis, patients must have evidence of myocardial ischemia by exercise ECG, stress scintigraphy, or stress echocardiography in conjunction with anginal chest discomfort. Some of these patients have documented reductions in coronary vasodilator reserve presumably due to abnormalities in the coronary microcirculation and can be shown to have true ischemia because their myocardium produces rather than removes lactate during stress.

The syndrome may be more common in patients with hypertrophied myocardium of any cause. Although the symptoms of metabolic syndrome (syndrome X) do not respond well to medical management, the prognosis in terms of major coronary events appears to be benign.

The prognosis of patients with metabolic syndrome (Syndrome X) is excellent, and myocardial infarction and cardiac death are extremely rare. Similarly, the natural history of atypical chest pain is often confused with that of patient’s with Syndrome X who have normal coronary angiography.


 * The metabolic syndrome is characterized by a group of metabolic risk factors in one person. They include:


 * Abdominal obesity (excessive fat tissue in and around the abdomen)
 * Atherogenic dyslipidemia (blood fat disorders; high triglycerides, low HDL cholesterol and high LDL cholesterol that foster plaque buildups in artery walls)
 * Elevated blood pressure
 * Insulin resistance or glucose intolerance (impaired glucose metabolism)
 * Pro thrombotic state (e.g., high fibrinogen or plasminogen activator inhibitor–1 in the blood)
 * Pro inflammatory state (e.g., elevated C Reactive Protein in the blood)

People with the metabolic syndrome are at increased risk of coronary heart disease and other diseases related to plaque buildups in artery walls (e.g., stroke and peripheral vascular disease) and type 2 diabetes mellitus. The metabolic syndrome has become increasingly common in the United States. It’s estimated that over 50 million Americans have it.

The dominant underlying risk factors for this syndrome appear to be abdominal obesity and insulin resistance. Insulin resistance is a generalized metabolic disorder, in which the body is unable to use insulin efficiently. Hence, the metabolic syndrome is also called the insulin resistance syndrome.

Other conditions associated with the syndrome include physical inactivity, aging, hormonal imbalance and genetic predisposition.

Some people are genetically predisposed to insulin resistance. Acquired factors, such as excess body fat and physical inactivity, can elicit insulin resistance and the metabolic syndrome in these people. Most people with insulin resistance have abdominal obesity. The biologic mechanisms at the molecular level between insulin resistance and metabolic risk factors aren’t fully understood and appear to be complex.


 * Diagnosis of the metabolic syndrome

There are no well-accepted criteria for diagnosing the metabolic syndrome. The criteria proposed by the National Cholesterol Education Program (NCEP) Adult Treatment Panel III (ATP III), with minor modifications, are currently recommended and widely used. The American Heart Association and the National Heart, Lung, and Blood Institute (AHA / NHLBI) recommend that the metabolic syndrome be identified as the presence of three or more of these components:


 * Elevated waist circumference:
 * Men: ≥40 inches = 102 cm
 * Women: ≥35 inches = 88 cm
 * Elevated triglycerides:
 * ≥150 mg/dL
 * Reduced HDL cholesterol:
 * Men < 40 mg/dL
 * Women < 50 mg/dL
 * Elevated blood pressure:
 * ≥130/85 mm Hg
 * Elevated fasting glucose:
 * ≥100 mg/dL