Is it possible to have heart disease and yet appear to have healthy coronary arteries?  The surprising answer is a resounding "yes." 

Up until about a decade ago, patients with cardiovascular disease symptoms, but with no evidence of blockages in their larger coronary arteries, posed a medical mystery for doctors.  Thanks to advances in diagnostic tools, researchers discovered the problem with these patients occurred not because of coronary artery disease (CAD) in the larger coronary arteries, but rather in the smaller coronary arteries.  "Coronary microvascular disease" or "coronary MVD" was born.

Your body needs a flow of oxygen-rich blood to nourish it and your heart muscle is no exception.  When the heart doesn't get enough oxygen to meet its needs (myocardial ischemia) one of two things can happen.  If the deprivation is limited, chest pain or pressure called angina may occur.  If the flow of blood is cut off, the result is a heart attack (myocardial infarction or heart muscle death).

Blood flows to the heart muscle first through three large coronary arteries, then through branches of thousands of smaller arteries called arterioles.  Healthy arteries are hollow tubes and the inner lining is smooth and elastic, allowing blood to flow freely.  When you exercise, a healthy artery can stretch to let more blood flow to your body's tissues.  The transition from artery to arteriole is a gradual one, marked by a progressive thinning of the vessel wall and a decrease in the size of the passageway. The job of the larger arteries is the distribution of blood.  They range from 1.0 - 4.0 millimeters in size.  The job of the arterioles is both blood distribution and resistance (pressure and flow regulation).  Think of the arterioles as "taps" for circulation, turning the flow up or down to match the needs of your body.  They range from 0.1 to 0.5 millimeters in size.

The symptoms of heart disease, in both men and women, often result from traditional coronary artery disease (CAD).  With CAD, the trouble begins when the inner walls of the larger coronary arteries are damaged from issues such as high blood pressure, high cholesterol, smoking and diabetes.  When this happens, plaque (a substance made up of excess cholesterol, calcium, and other substances in the blood) starts to build up (atherosclerosis).   Plaque can slow and completely block the flow of blood to the heart muscle.  It can also crack, causing blood cells called platelets to clump together and form blood clots.  This type of heart disease can be seen with tests such as coronary angiograms and with noninvasive tests such as special CT and MRI scans.  (For more information about CAD, see the Second Opinion episode on Heart Attack )
 
Coronary microvascular disease is an elusive disease.  It doesn't show up on many standard tests.  When a doctor sees an angiogram with wide open arteries, he or she may assume that symptoms like chest pain, shortness of breath, light-headedness, diffuse discomfort in the chest or unusual exhaustion are caused by something other than heart disease.  If the doctor isn't familiar with coronary MVP, it's unlikely that additional tests will be ordered.    

Even if the large coronary arteries are clear, coronary MVD can still be present.  The angiograms of 50% to 60% of women and 20% of men with symptoms of heart disease show clear arteries on an angiogram.  Medical experts believe that the majority of those have coronary MVD, a disease that's just as dangerous as CAD.  Just like CAD, it increases the risk of heart attacks and heart failure. 

The characteristics of microvascular dysfunction include:

• A build-up of plaque that spreads evenly throughout the walls of the small arteries.  So while there may be no obvious blockages, blood flow to the heart is still low.  (Coronary MVD is also called non-obstructive CAD.)     
• Vessels that don't expand or dilate properly during physical or emotional stress.
• Vessels that spasm (contract) abnormally.

Coronary MVD has some other unique features.  Symptoms of angina with coronary MVD may or may not be the typical chest pain seen in CAD.  Plus, CAD symptoms often first appear while a person is being physically active, for example while jogging or going up stairs, and coronary MVD signs are often first noticed during routine daily activities and during times of mental stress.

Doctors are refining their methods for diagnosing coronary MVD and research is ongoing to find the best preventive strategies and treatments.  In the meantime, doctors are following similar approaches to those used to prevent and treat CAD.   

Diagnosis remains the biggest hurdle for people with coronary MVD.  Many people spend years going undiagnosed and some never are.  If you have recurrent chest pain and your doctor says you're fine because you have clear coronary arteries, don't give up.   Sometimes doctors get it wrong.  Seek a second opinion and if that doesn't help, seek a third.  You're the expert on your own body.  When it's trying to tell you something, listen. 

Most importantly, if you think you're having a heart attack call 9–1–1. Acting fast at the first sign of heart attack symptoms can save your life and limit damage to your heart. Treatment is most effective when started within 1 hour of the beginning of symptoms.  (Learn about heart attack symptoms in the Second Opinion episode on Heart Attack.)

Several other episodes of Second Opinion also explore various aspects of heart disease. You'll find valuable information at

         Second Opinion, Heart Failure (Cardiomyopathy), Episode 102

         Second Opinion, Heart Rhythm Disorder (Arrhythmia), Episode 110

         Second Opinion, Women's Cardiac Health, Episode 209

         Second Opinion, Depression and Heart Disease, Episode 302

         Second Opinion, Cardiac Breakthroughs, Episode 407

         Second Opinion, Stroke, Episode 205 

Learn more about Coronary Microvascular Disease:

Key Point 1: When it comes to heart disease, not only are the symptoms sometimes different for men and women – but the disease itself may be different. 
 
Key Point 2:  Coronary microvascular disease is tough to diagnose.  If you are experiencing symptoms that concern you, don't ignore them.  You need to continue a dialogue with your doctor until you're both satisfied.

Key Point 3: If you've been diagnosed with coronary microvascular disease, getting adequate blood flow to your heart is critical.  Lifestyle changes are the most effective treatment.