Role of MRI in Assessment of Valvular Heart Diseases - An Overview

Introduction:

The circulatory system involves primarily the heart, blood vessels, and blood. The heart is the prime organ regulating the circulatory system. The heart comprises four chambers; two upper chambers (right and left atrium) and two lower chambers (right and left ventricles). These chambers are guarded by certain valves that regulate the blood flow. Valves ensure a one-way blood flow from the heart to the rest of the body. There are four valves interconnecting the four chambers of the heart. They are,

1. Tricuspid Valve: Valve between the right atrium and right ventricle.

2. Mitral Valve: Connects the left atrium with the left ventricle.

3. Pulmonary Valve: It connects the right ventricle and the pulmonary artery.

4. Aortic Valve: This is a connection between the left ventricle and the aorta.

These valves are made up of thick fibrous connective tissue that is organized in the form of leaflets. These leaflets open and close, thereby regulating the blood flow. They open so that blood can pass from one chamber to another and close immediately to prevent any back-flow. All valves are composed of three leaflets except the mitral valve, which comprises two.

What Is Valvular Heart Disease?

When any valve of the heart is diseased or damaged, it is known as valvular heart disease. Valvular heart disease can affect any of the four valves; however, the aortic valve is most commonly affected. A diseased heart valve may not be able to function properly, resulting in disrupted circulation. Valvular heart disease could be fatal if not treated, as it may result in cardiac failure. Valvular heart disease is also closely linked to rheumatic heart disease, most commonly affecting the aortic or the mitral valve. Mortality due to valvular heart disease is mainly related to aortic valve conditions.

What Are the Reasons for Valvular Heart Disease?

Valvular heart diseases may occur due to various reasons. A few of them are given below:

• Rheumatic Heart Disease: This is a life-threatening condition due to scarring and damage of heart valves by rheumatic fever. Rheumatic fever results from inadequately treated bacterial infections such as streptococcal throat infections or scarlet fever.

• Endocarditis: It is a bacterial infection affecting the endocardium (lining of the heart) and thereby damaging the heart valves.

• Congenital Defects: Bicuspid aortic valve is the most common congenital malformation resulting in valvular heart disease.

• Genetic Disorders: Certain genetic conditions may result in mitral valve prolapse or aortic valve regurgitation.

• Systemic Diseases: High blood pressure, high blood cholesterol, and atherosclerosis (cholesterol and calcium deposits in vessels supplying the heart) could result in a heart attack, which may damage the muscles controlling the valves.

• Radiation Therapy: Chest radiation therapy for cancer treatment could result in calcium deposits in the valves.

• Age: Aging would result in degenerative changes and increased calcium deposits due to atherosclerotic changes. The valves tend to lose their elasticity, becoming rigid and less functional.

What Are the Symptoms of Valvular Heart Disease?

The symptoms may be sudden onset or may develop progressively as the disease advances. A few of the symptoms are listed below:

• Chest pain.

• Difficulty in breathing.

• Shortness of breath.

• Nausea.

• Dizziness.

• Fever.

• Irregular heartbeat.

• Swelling in the abdomen, ankles, and feet.

What Are the Types of Valvular Heart Disease?

Heart valve disease may occur mainly due to three reasons based on which they are classified into:

• Stenosis: The valve becomes narrow and stiff and opens partially.

• Prolapse: When the valve slips out of place.

• Regurgitation: It is the backward flow of blood through the valve. When the diseased valves do not close completely, the blood flows back to the chamber from where it came. As a result of this, an insufficient quantity of blood is pushed through the heart. This increases the workload of the heart as it may have to pump more to meet the supply-demand. This may result in an enlarged heart or lead to heart failure.

The various types of valvular heart disease are described below:

How Can Valvular Heart Disease Be Diagnosed?

The physical signs and symptoms usually lead to an array of confirmatory diagnostic tests. The diagnostic workup is listed below:

• Physical Examination: A detailed physical examination would include a complete medical history and assessing the heartbeat and heart sounds. An irregular heartbeat or an unusual heart sound may not indicate a disease but may warrant some additional imaging tests.

• Echocardiography: It is the ultrasound examination of the heart. Echocardiography is the imaging modality of choice to detect heart diseases. This test can image the structure, size, and blood flow through the heart.

• Electrocardiogram: Electrocardiogram uses certain sensors that determine the electrical impulses of the heart and thereby detect any irregular functioning or atypical rhythms.

• Chest X-Ray: A chest X-ray may detect an enlarged heart suggesting an underlying heart condition. But to establish the cause, further tests may be needed.

• Stress Test: A stress test may help determine the response of the heart during rest and physical activity. An abnormal response may be suggestive of a cardiac anomaly.

• Cardiac Angiogram: This is an invasive yet conclusive test. A contrast dye is injected through the veins into the heart and imaged using x-ray, computed tomography, or magnetic resonance imaging. This technique gives a detailed picture of the structure of the heart, the valves, and the blood vessels.

What Is the Role of MRI (Magnetic Resonance Imaging) in Diagnosing Valvular Heart Disease?

Magnetic resonance imaging is a non-invasive technique that uses a magnetic field and radio waves to capture images of the body. Cardiac magnetic resonance imaging plays a significant role in assessing valvular heart disease. It is a precise diagnostic tool to detect and evaluate the severity of valvular heart disease. In addition, it is efficient in monitoring the treatment response and prognosis. Cardiac MRI has the advantage of assessing the functioning of the heart and its structure. It is non-invasive, devoid of radiation effects, and does not require any contrast to enhance the image. Cardiac MRI can be used to:

• Diagnose congenital heart defects.

• Detects scar tissue due to a previous heart attack or other conditions.

• Functioning of the heart.

• Aid in a biopsy.

• Assess the treatment option.

• Diagnose cardiac tumors.

• Heart failure.

Conclusion:

Though echocardiography is the standard diagnostic procedure for detecting valvular diseases, cardiac MRI is more efficient and comprehensive. Compared to ultrasound and other imaging techniques, cardiac MRI can precisely delineate the heart anatomy and provide details on the functioning of the heart. In addition, it can diagnose valvular heart disease, determine the severity and assess the treatment options. With the technological advances in the diagnostic field, MRI proves to be a dedicated tool for evaluating cardiac conditions.