Left Main Coronary Artery Disease: Symptoms and Treatment

Introduction

The heart muscles receive blood from the coronary arteries. The heart muscle requires oxygen-rich-blood to operate, just like all other body structures do. Blood that lacks oxygen must also be transported away from the heart. The coronary arteries encircle the heart and branch out into smaller blood vessels to supply the heart muscle with blood. Any dysfunction within the coronary arteries can have catastrophic consequences since it limits the delivery of oxygen and nutrients to the heart muscle. This eventually leads to cardiac arrest. The most common cause of heart disease is atherosclerosis, a buildup of plaque in the inner lining of the artery (blood vessel) that causes it to narrow or obstruct.

What Is Left Main Coronary Artery Disease?

Left main coronary artery disease, also known as the left main disease and LM disease, is a medical condition characterized by stenosis of the left main coronary artery. The left main coronary artery is narrowed by more than 50 percent when seen on an angiogram. It is relatively uncommon but is an important etiological factor for symptomatic coronary disease.

What Is the Left Main Coronary Artery?

Primarily, there are two main types of coronary arteries - the right coronary artery (RCA) and the left main coronary artery (LMCA). The left main coronary artery is typically larger than the right coronary artery. It has two offshoots, each of which supplies a more significant portion of the heart, including most of the left ventricle (left lower heart chamber), interventricular septum, and left atrium (left upper heart chamber). The two offshoots of the left main coronary artery are -

• The Left Anterior Descending Artery - It supplies blood to the anterior aspect of the left heart.

• Circumflex Artery - It splits and surrounds the heart, providing blood to the posterior aspect of the left heart.

What Are the Different Types of Left Main Coronary Artery Disease?

There are two types of coronary artery disease, namely -

• Protected Left Main Disease - It is a disease in which there is a patent bypass graft present in at least one of the two branches of the left main coronary artery's circulation.

• Unprotected Left Main Disease - Also referred to as ULMD, it is a disease in which either of the left main coronary artery branches does not have a patent graft.

What Are the Signs and Symptoms Associated With Left Main Coronary Artery Disease?

The occlusion of the left main coronary artery compromises more than 75 percent of blood flow to the left ventricle. Hence, patients are usually symptomatic. The following signs and symptoms are associated with left main coronary artery disease -

• Angina (chest pain).

• Dyspnea (shortness of breath).

• Arrhythmias (irregular heartbeats).

• Fatigue.

• Weakness.

• Retrosternal discomfort (chest discomfort in the form of pain that can be constricting, suffocating, crushing, heavy, or squeezing and is located behind the sternum or breastbone).

• Crushing or piercing chest pain that radiates and extends to the shoulders, back, neck and jaw.

• Dizziness.

What Causes Left Main Coronary Artery Disease?

The primary cause for the stenosis (narrowing) of the left main coronary artery is atherosclerosis. Atherosclerosis is the hardening and narrowing of the arteries (blood vessels) due to plaque formation. Plaque is a waxy substance that is predominantly made up of fats. The other causes of the left main coronary artery disease are categorized as non-atherosclerotic etiologies, including -

• Aortic dissection.

• External compression that results from an aortic aneurysm or tumor.

• Accidental injuries resulting from coronary procedures.

• Vasospasm.

• Irradiation.

• Syphilitic aortitis.

• Rheumatoid arthritis.

• Aortic valve disease.

What Are the Risk Factors Associated With Left Main Coronary Artery Disease?

The risk factors include -

• Smoking.

• High levels of bad cholesterol or LDL (low-density lipoprotein).

• High levels of triglycerides.

• Low levels of good cholesterol or HDL (high-density lipoprotein).

• Hypertension (high blood pressure).

• Diabetes (increased levels of blood sugar).

• Obesity.

• Diet having high levels of saturated fats.

• Family history of coronary artery disease.

Which Tests Are Involved in the Diagnosis of Left Main Coronary Artery Disease?

The physician conducts the following tests for the diagnosis of left main coronary artery disease-

• Coronary Angiography - Also known as cardiac catheterization, is an x-ray examination of the heart's chambers. It is often done to identify narrowed or clogged coronary arteries preventing blood from reaching the myocardium (heart muscle). It is also done to assess the size and function of the heart chambers and valves. It is the gold standard test for diagnosing left main coronary artery disease.

• Fractional Flow Reserve (FFR) - Although coronary angiography gives a visual representation of the severity of the stenosis, it does not imply the actual functional significance of the stenosis in terms of blood flow. Fractional flow reserve is a test that helps decide the lesions which limit blood flow.

• Intravascular Ultrasound Imaging (IVUS) - This intracoronary imaging technique allows a 360-degree visualization of the vascular lumen. It also helps in identifying the nature of plaque. Compared to coronary angiography, intravascular ultrasound imaging offers additional information about plaque, such as minimal and maximal diameters and the cross-sectional area.

• Electrocardiogram (ECG or EKG) - An electrocardiogram helps record the heart's electrical activity.

• Coronary Vasodilatory Reserve (CVR) - It is a diagnostic test assessing blood flow resistance in the blood vessels.

• Cardiac Computed Tomography (CT) - It is a test that helps visualize the patency of the heart tissue and its associated blood vessels.

• Cardiac Magnetic Resonance Imaging (MRI) Test - This is a non-invasive, painless imaging test that creates detailed images of the heart and its associated structures and uses magnetic and radio waves.

What Is the Treatment for Left Main Coronary Artery Disease?

Left main coronary artery disease can be managed in the following ways -

1. Preventive Therapy

Preventive measures such as lifestyle modification, smoking cessation, dietary modifications, and incorporating more physical activity can help tremendously reduce the risk of further cardiac events.

2. Drug Therapy

Patients are prescribed medications to lower sugar levels, blood pressure, and lipid levels.

3. Surgical Intervention

Surgical interventions such as coronary artery bypass graft (CABG) and percutaneous coronary intervention (PCI) are considered when the patient is critical and other therapies fail to produce results. Percutaneous coronary interventions refer to a group of minimally invasive surgical procedures used to remove obstruction present with coronary arteries. A few examples of percutaneous coronary intervention include balloon angioplasty, rotational atherectomy, and stent placement with angioplasty.

Conclusion

Left main coronary artery disease, also known as the left main disease or LM disease, is a cardiac disease characterized by extensive stenosis or narrowing of the left main artery and is relatively uncommon. The left main artery supplies blood to a significant part of the heart. Although left-main coronary artery disease is uncommon, it needs immediate intervention since it can lead to cardiac arrest and death. The left main artery supplies blood to a significant part of the heart. Treatment options include preventive measures, drug therapy, and surgical intervention. People are diagnosed with this disease when the blood supply to the heart has been severely compromised. Hence, routine health check-ups can help doctors detect such diseases early and make timely interventions.