MICROVASCULAR ANGINA
Microvascular angina is angina in the presence of "normal coronaries" (no arteriosclerotic cholesterol plaque evident on coronary arteriography).
It is also called Syndrome X.
It is attributable to "small vessel disease" which affects the arterioles, vessels too small to see on arteriograms.
The middle layer of the arteriole, the media, which is comprised of muscle becomes thickened.
The arterioles constrict abnormally, sometimes as a direct result of excess adrenalin (epinephrine).
Angina is defined as any abnormal feeling resulting from decreased blood flow to some portion of heart muscle (myocardial ischemia). It is often described as discomfort, pressure, tightness or squeezing, and less often as a pain.
It may occur in the chest, upper abdomen, neck, jaw, back, shoulder, or arms.
It may be provoked by exercise, activity (mental or physical), emotion or stress.
It is generally helped or relieved by nitroglycerin (NTG) under the tongue (SL) in a few minutes.
Microvascular angina most often occurs at rest and is relieved by NTG.
Stress testing may demonstrate an abnormal ECG with ST depression.
Nuclear stress scans (Thallium, Sestamibi) usually do not demonstrate an abnormal area of perfusion.
Stress Echoes usually do not show abnormal contraction (wall motion) of the left ventricle.
Cardiac catheterization demonstrates "normal coronaries" as far as arteriosclerotic plaque is concerned; however, there is often a visible delay in blood flow from the beginning of the coronary arteries to the tip of th heart on coronary arteriograms. Also, the diastolic blood pressure in the left ventricle is usually elevated above 12 mmHg. This elevated pressure at a time when the heart has finished contracting and is relaxed is called "diastolic dysfunction" or "stiff left ventricle."
Resting echocardiograms often demonstrate a pattern of diastolic dysfunction.
Helpful medications may include vasodilators such as ACE inhibitors, ARB's, or calcium channel blockers.
Beta blockers counteract adrenalin and may help.
Esophageal spasm or gastroesophageal reflux secondary to a hiatal hernia may cause chest discomfort that mimics angina. This is often associated with belching, nausea, vomiting, drinking cold drinks, or lying down after eating.
Patients with microvascular angina often complain of inappropriate coldness of the hands or feet during, for example, the summer.
Regular exercise may alleviate the condition by dilating the arterioles.
REFERENCES:
1. Cannon, R.O. Cardiovascular Syndrome X. Women's Health in Primary Care, June 99; II 6, 455-462.
2. Cannon, R.O. et al. Chest Pain in Women with Normal Coronary Angiograms. NEJM March 23, 2000; 342:885-887.
3. Chauhan, A. Syndrome X: Natural History and Possible Pathophysiologic Mechanisms. Primary Cardiology Dec 95; 21:8-14.