Cardiotoxicity refers to damage to the heart muscle or its ability to pump blood effectively. It arises from exposure to certain substances, impairing heart function and leading to various forms of cardiac dysfunction. This condition is a potential side effect associated with diverse medical treatments and external agents. Understanding this damage is important, as it directly impacts cardiovascular health.
Causes of Cardiotoxicity
Cardiotoxicity often results from specific medical treatments, particularly those used in cancer therapy. Anthracyclines, such as doxorubicin and daunorubicin, are chemotherapy agents known to cause dose-dependent, and often irreversible, damage to heart muscle cells, primarily through oxidative stress. Another targeted therapy, trastuzumab (Herceptin), used for HER2-positive cancers, can also lead to heart dysfunction, though its effects are more reversible and not cumulative dose-dependent. Combining anthracyclines with trastuzumab significantly increases the risk of cardiotoxicity, with cardiac event rates potentially reaching 27%.
Radiation therapy directed at the chest area, commonly used for breast cancer, lung cancer, or lymphomas, can also harm the heart. Radiation can cause fibrosis, or scarring, of heart tissues, affecting the myocardium, pericardium, valves, coronary arteries, and the electrical conduction system. This damage can manifest years or even decades after treatment.
Beyond cancer treatments, other medications may contribute to cardiotoxicity. Certain antipsychotic drugs, like clozapine, have been linked to myocarditis and cardiomyopathy, with myocarditis often occurring within the first two weeks of treatment. Some antibiotics, such as erythromycin and levofloxacin, can prolong the QT interval, affecting the heart’s electrical rhythm. Non-steroidal anti-inflammatory drugs (NSAIDs) and some calcium channel blockers can exacerbate heart failure.
Substances of abuse also pose a significant risk to heart health. Cocaine, for example, can cause sudden increases in blood pressure and heart rate, leading to heart attacks, arrhythmias, and cardiomyopathy. It can constrict blood vessels around the heart, limiting blood flow to the muscle. Excessive alcohol consumption is a known cause of alcoholic cardiomyopathy, where the heart muscle weakens and enlarges. The combined use of alcohol and cocaine further increases the risk of heart damage.
Signs and Symptoms
Recognizing the signs of cardiotoxicity is important for early intervention. Individuals may experience persistent fatigue and general weakness, which can be subtle. Shortness of breath, especially during physical activity or at rest, is a common symptom, signaling decreased heart pumping efficiency.
Swelling, or edema, in the legs, ankles, and feet is another physical manifestation, resulting from fluid retention. Patients might also notice an irregular or rapid heartbeat, known as palpitations, reflecting electrical disturbances. A persistent cough or wheezing, sometimes mistaken for respiratory issues, can also be a symptom of fluid buildup in the lungs due to impaired heart function. These symptoms can emerge during or shortly after exposure, or they may develop months to many years later, especially in those treated for cancer during childhood.
Diagnosis and Monitoring
Detecting cardiotoxicity involves a systematic approach to assess heart function both before and during potentially damaging treatments. A baseline evaluation of heart health is performed before starting therapies known to cause cardiac damage. This initial assessment helps establish a reference point for future comparisons.
Echocardiography is a primary diagnostic tool, utilizing sound waves to create images of the heart. This non-invasive ultrasound provides detailed information about the heart’s pumping strength, including the left ventricular ejection fraction (LVEF), which measures the percentage of blood pumped out with each beat. A significant decrease in LVEF indicates cardiotoxicity. Electrocardiograms (EKGs or ECGs) are also used to record the heart’s electrical activity, identifying any irregular rhythms or other electrical abnormalities.
Blood tests play a complementary role by checking for specific cardiac biomarkers. High-sensitivity cardiac troponins (cTnI and cTnT) are useful as they are released into the bloodstream when heart muscle cells are injured. Elevated troponin levels can indicate myocardial damage, even before symptoms appear or significant changes are visible on imaging. Other markers like B-type natriuretic peptide (BNP) or N-terminal pro-B-type natriuretic peptide (NT-proBNP) may also be monitored.
Management and Treatment Strategies
Once cardiotoxicity is identified, management focuses on supporting heart function and mitigating further damage. Medications prescribed to improve heart performance include angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs). These drugs help relax blood vessels, reduce the heart’s workload, and can prevent further deterioration of heart function. Beta-blockers are also used to slow the heart rate and improve pumping efficiency.
Diuretics are administered to help the body eliminate excess fluid, reducing swelling and improving breathing. This helps to alleviate symptoms related to fluid retention and congestion. In some cases, mineralocorticoid receptor antagonists (MRAs) may be added to a regimen to manage fluid balance and support heart health.
Adjustments to the original causative treatment may be necessary to balance cancer treatment efficacy with cardiac safety. Doctors might reduce the dose of the cardiotoxic medication, temporarily pause treatment, or switch to an alternative therapy with a lower risk of heart damage. This decision involves careful consideration of the patient’s overall health, the severity of cardiotoxicity, and the progression of the primary illness. Lifestyle modifications also contribute to heart health, including a balanced diet, regular physical activity, and avoiding tobacco and excessive alcohol.