About Angina Without Blocked Arteries

Angina that occurs without blocked arteries is known as microvascular angina (a fascinating fact is that it used to be called Syndrome X - what a cool name!).¹ But this begs the question - how is this different from the ‘normal’/’standard’ angina? In this article, we will first understand the signs, symptoms & causes of angina and then discuss the mechanics behind microvascular angina (MVA). 

What is Angina?

Many of us are familiar with the term heart attack or, as the medics and doctors call it, myocardial infarction (it sounds very fancy and makes you feel smart!). In this condition, the blood supply to the heart is instantaneously blocked, and one of the primary reasons for this is blood clots.² Something that sometimes confuses people is how a heart attack relates to angina and how the two are different. Angina is described as chest pain, discomfort, or heaviness/tightness primarily due to reduced blood flow and oxygen supply to the heart. Angina results from narrowing of the coronary arteries that supply oxygenated blood to the heart. In contrast, a heart attack usually entails blockage of coronary arteries. 

Now that we have made this distinction, let’s look at some of the tell-tale signs of angina. 

Signs and Symptoms

As you might have guessed, one predominant sign that someone has an angina is chest pain. But chest pain can also be caused by several other factors, such as heartburn, chest sprain/strain, chest infections (such as pneumonia), anxiety/panic attacks, etc. Therefore, it is essential to know the defining traits of anginal chest pain.⁴

1. Tightness/heaviness 
2. Sharp, stabbing pain
3. Radiates to other areas of the upper body (such as arms, neck, jaws & back)
4. Pain is stimulated by physical stress and relieved a few moments after resting

Apart from chest pain, individuals with angina may also present with shortness of breath, nausea, or fatigue. In some cases, people present with these symptoms without experiencing chest pain.

Causes and Risk Factors

In this section, we will investigate the causes and risk factors that can give rise to angina. Briefly speaking, coronary artery disease is the primary reason behind angina, but its risk can be accentuated by factors such as age, working environment, genetics, lifestyle & other medical conditions. 

Conditions that Cause Angina

At the beginning of the article, we established that angina usually results from narrowed arteries, but there can be other causes. In some cases, there is a mismatch between the demand & supply of oxygen in the body, which inevitably affects the heart. Conditions that may give rise to such a mismatch include: ⁵

1. Anaemia
2. Cardiomyopathy
3. Heart failure, heart valve issues, or high blood pressure
4. Metabolic syndrome

Typically, when you do any physically strenuous activity, your heart (a muscle) relies on the effective supply of oxygenated blood. However, when someone is affected by one of the conditions above, the oxygen demand that the muscles require cannot be met, leading to angina symptoms. 

Role of Coronary Artery Disease

As mentioned before, coronary artery disease is vital in causing angina.⁵ Also known as ischaemic (the phrase refers to a deficiency of blood supply to a body part due to impediment of arterial blood inflow)⁶ heart disease is the most common type of heart illness in the US and affects around 126 million people worldwide (1.72% of the world population).⁷ It is caused by plaque build-up (fat, cholesterol, calcium, cellular waste products, calcium, and other components found in the blood) in the coronary arteries. Over time as plaques build up in the arteries, they can lead to a partial or complete blockage of blood flow - this process is called atherosclerosis.⁸ The partial or complete blockage leads to an inadequate supply of oxygenated blood to the heart, causing symptoms of angina.

Diagnosis and Treatment

Diagnosis of angina would involve a physician taking your medical history to understand your symptoms, presenting complaints, past medical history, family history, current medications, and social circumstances (lifestyle). This will likely be followed by a physical examination involving blood pressure, heart rate, etc. Finally, your doctor will also probably order some diagnostic procedures such as electrocardiogram, echocardiography, and treadmill stress test.

As with many other diseases, the severity of angina in a patient will dictate the type of treatment prescribed. In milder cases, lifestyle changes (such as losing weight or quitting smoking) can help immensely. However, sometimes medications and other procedures may be required.

What is Microvascular Angina?

Finally! After a long read about angina, we arrive at the star and spotlight of this article. MVA, sometimes called Cardiac Syndrome X, is a subtype of angina (or chest pain) that occurs without blockage of coronary arteries by plaque.

Conditions that Cause Microvascular Angina

The disease is mainly a symptom of and is caused by coronary microvascular disease in which the walls of the smallest coronary artery vessels (these branch off from the larger coronary arteries) are damaged. Juan Carlos Kaski, a professor of cardiovascular sciences at St. Georges University of London, explained in an article for the British Heart Foundation that this disease prevents the microvessels from dilating (opening up) or causes these vessels to spasm (vigorous constriction) severely.¹⁰ As you can imagine, this prevents blood flow to the heart on occasions of stress or strenuous physical activity leading to pain in the chest. 

A key point in understanding the difference between ‘regular’ and microvascular angina is that the former lasts for about 5 to 15 minutes. In contrast, the latter usually lasts about 10 minutes and can continue for 30 minutes.¹¹ This type of angina may also cause more pain than the ‘regular’ one.¹¹

Diagnosing Microvascular Angina

The issue with diagnosing microvascular angina lies in that there is a general lack of awareness about it. Furthermore, Professor Kaski asserts that “abnormalities of the coronary microvessels are difficult to spot”, even on angiograms.¹¹ Researchers and physicians have reported that patients with microvascular angina are prone to misdiagnosis. ¹²

The solution therein lies in increasing awareness, a sentiment that Professor Kaski also reinforces in her article for the BHF. She also briefly outlines that procedures such as ‘MRI, stress echocardiography, and acetylcholine prevention provocation’ would be vital in ensuring a correct diagnosis. ¹¹

Current Research

Recently, the Coronary Vasomotion Disorders International Study Group has proposed a systematic set of criteria for diagnosing MVA, which include the following: ischemic symptoms in the absence of obstructive/epicardial coronary artery disease, evidence of myocardial ischemia seen upon stress testing, and functional damage to the coronary microvessels.¹²

In terms of current advancements in treatment, since the pathophysiology of MVA itself has not been completely understood, it has become difficult for physicians to suggest appropriate treatment. That said, management of MVA primarily consists of antianginal medications, changes in lifestyle habits, and control of risk factors.¹³

Summary

In summary, angina is chest pain that results from the narrowing of the blood vessels supplying oxygenated blood to the heart and is usually caused by coronary artery disease. This type of angina is better understood; hence, treatment options are more accurate. On the other hand, MVA occurs as a result of injury to the smallest coronary artery vessels in the heart, usually due to coronary microvascular disease. Since more research is needed to get a lucid picture of this illness, treatment options are not very clear. Nonetheless, the most important thing to remember is that MVA pain is generally more persistent than chronic angina pain. Therefore, the best thing to do if you or your loved one(s) are experiencing symptoms like this is to contact your healthcare provider. This will assuredly help you put your mind at ease.