Prevention of Radiation-Induced Cardiomyopathy - Techniques and Precautions

Introduction

Radiation therapy is the main treatment given to individuals with cancer. This therapy uses beams of rays and energy that destroy cancer cells, and receiving this radiation on the chest can damage the heart. This can result in various heart problems, which tend to develop over weeks and years after receiving radiation therapy. Most radiation heart disease occurs in individuals who receive treatment for lung cancer, Hodgkin's lymphoma, esophageal cancer, and breast cancer.

What Is Radiation-Induced Cardiomyopathy?

Cardiomyopathy is common in individuals who receive anthracycline chemotherapy or a high radiation dose. The incubation period of myocardial injury can last as long as ten years. Clinical symptoms of myocardial injury are caused by radiation therapy, which is affected by myocardial fibrosis. Most radiation-induced myocardial injury has no clinical symptoms, and the diagnostic rate is just ten percent. Individuals who receive high doses of radiotherapy are more prone to restrictive myocardial injury, and chemoradiotherapy is prone to diastolic cardiomyopathy.

What Is the Pathogenesis of Radiation-Induced Heart Disease?

The effect of radiation on the heart has a clear effect on radiation-induced heart disease. Many cytokines involve the process, regulation, and control mechanisms affected by various factors. These factors interact with each other and affect the mechanism of radiation-induced heart disease. Radiation-induced heart disease is associated with an inflammatory reaction, endothelial cell injury, mitochondria, oxidative stress, and endoplasmic reticulum injury. Chronic and acute inflammatory changes mostly cause early damage from radiation therapy, and acute and chronic inflammatory changes partly cause toxicity. These changes lead to heart disease. Therefore, the biological mechanism of radiation-induced heart disease is very important to clarify the pathogenesis of the associated disease.

How Does Radiation Therapy Affect the Heart?

Radiation can affect the tissues in and around the heart and cause inflammation. Over time, they can become fibrous and tough and fail to function properly. The heart tissue is mainly affected by radiation therapy are:

• Cells that carry and produce electrical impulses maintain heart rate and rhythm-conduction systems.

• Heart muscle - Myocardium.

• Arteries that carry blood from heart muscle - Coronary arteries.

• Valves that prevent blood flow backward and separate heart chambers.

• Tissue that covers the heart - Pericardium.

What Are the Long-Term Complications of Getting Radiation-Induced Therapy?

The radiation-induced therapy may lead to heart complications like:

• Valvular heart disease.

• Thickening of the pericardium.

• Heart rhythm changes.

• Cardiomyopathy (enlarged heart).

• Congestive heart failure.

• Coronary artery disease.

Who Is at Risk of Getting Heart Disease After Radiation Treatment?

Risk of receiving heart disease after radiation therapy in the chest, especially on the left side. The unit of measurement for radiation is called Gray. A total dose of more than 30 Gy over a series increases the risk of radiation heart disease. Other factors that increase risk are:

• Pre-existing heart disease.

• Young age during radiation treatment.

• Co-treatment with cardiotoxic chemotherapy medication like anthracyclines and Trastuzumab.

Other behaviors and health conditions can also increase risk like:

• Excess alcohol use.

• High blood pressure.

• Carrying excess weight.

• Smoking.

• Unhealthy cholesterol levels.

• Diabetes.

• Physical inactivity.

What Are the Symptoms of Radiation-Induced Cardiomyopathy?

Symptoms of heart disease due to radiation depend on how soon they appear:

• Short term radiation: Lead to pericarditis and pericardial effusion. The main sign of this condition is severe chest pain, which leads to dyspnea.

• Long-term radiation: Radiation-induced heart disease initially does not cause symptoms till they progress. The symptoms are:

  • Chest pain.

  • Nausea.

  • Dry cough.

  • Dizziness.

  • Weakness or fatigue.

  • Shortness of breath.

  • Swelling of ankles, feet, legs, or abdomen.

  • Rapid and irregular palpitations.

  • Severe conditions can also lead to cardiac arrest and heart attack.

What Are the Diagnostic Procedures to Detect Radiation-Induced Cardiomyopathy?

Tests to diagnose heart disease are mainly done by a physical exam and blood tests along with other tests like:

• Chest X-Ray - Images of the heart, lungs, airways, blood vessels, and spine and chest bones can be seen on a chest x-ray.

• Echocardiogram - Sound waves are used in an echocardiogram to produce images of the heart. This basic test can demonstrate how the heart and its valves function.

• Cardiac Catheterization - Cardiac catheterization is a treatment used to detect or treat certain heart diseases, such as clogged arteries or irregular heartbeats, by guiding a thin, flexible tube (catheter) through a blood vessel to the heart.

• Cardiac CT Scan (Computed Tomography) - During a cardiac computed tomography (CT) scan, numerous X-ray beams are used at various angles to produce high-quality, three-dimensional (3D) images of the heart, major arteries, and surrounding structures.

• Electrocardiogram - An electrocardiogram captures the electrical activity of the heart. It is a routine test that is painless and used to swiftly identify heart issues and keep track of the heart's health.

• Holter Monitor - The heart's rhythm is captured by a tiny, wearable device called a Holter monitor. It identifies or assesses the possibility of irregular heartbeats (arrhythmias).

• Exercise Stress Test - A stress test during an exercise reveals how well the heart reacts under the most demanding conditions. It usually entails using a treadmill or a stationary cycle to track the heart's activity while connected to an EKG.

How to Prevent Radiation-Induced Cardiomyopathy?

Preventing radiation-induced cardiomyopathy is primarily achieved by limiting the amount of radiation on the heart. Advanced cancer radiation delivers precise doses of radiation to tumors and reduces the amount of radiation to the surrounding tissue. These are:

• Proton Therapy: This uses high-energy, positively charged particles called protons, and their energy is directed into the tumor.

• Intensity-Modulated Radiation Therapy (IMRT): This uses 3D tumor mapping with highly controlled radiation beams.

Positioning can also help in reducing radiation exposure to the heart while treating breast cancer.

Steps to reduce the risk of radiation heart disease are:

• Leading a healthy lifestyle can lower the risk of developing heart disease.

• Regular exercise.

• Eating a healthy diet.

• Quitting smoking.

• Avoiding alcohol.

• Managing cholesterol levels and blood pressure.

• Routine follow-up care after the cancer treatment can help monitor overall health.

Conclusion

Radiation-induced heart disease is an important source of mortality and morbidity in individuals undergoing thoracic radiotherapy for cardiac surgery. In most cases, the clinical symptoms appear ten years after the end of radiotherapy. Individuals who receive radiation therapy on the chest for treating cancer tend to develop radiation-induced heart disease within a few years of the therapy. By utilizing recent advances in radiation and technology, radiation-induced heart disease can be reduced. The treatment options also improve and allow a better quality of life. A regular overall timely check-up is important to detect symptoms of any heart disease after receiving radiation therapy. Effective approaches for treating radiation-induced heart disease are limited and mainly due to pathogenesis and etiology.