Introduction: Who Should Undergo Diagnostics

Not everyone receiving cancer treatment needs the same level of heart monitoring, but certain groups face higher risks and should undergo cardiovascular diagnostics before, during, and after chemotherapy. People who are receiving anthracyclines—powerful chemotherapy drugs like doxorubicin used to treat breast cancer, lymphoma, leukemia, and sarcomas—are particularly vulnerable to heart damage. These medications are known to cause cardiotoxicity, which means damage to the heart muscle that can lead to serious complications.^[1]

Patients treated with trastuzumab, a targeted therapy commonly used for breast cancer and stomach cancer, also need careful heart monitoring. This drug can cause a decline in the heart’s pumping ability in approximately 7% to 19% of patients, and when combined with anthracyclines, the risk of heart problems can climb as high as 27%.^[4] Anyone receiving radiation therapy to the chest—such as those being treated for breast cancer or leukemia—should also be monitored, as radiation can damage heart structures over time.^[2]

Certain personal characteristics increase the likelihood of developing chemotherapy-induced heart damage. Adults who received cancer treatment during childhood should seek cardiovascular evaluation, as up to 20% of childhood cancer survivors may develop heart problems later in life, with 7% to 10% experiencing cardiomyopathy or heart failure.^[2] Elderly patients, those with pre-existing heart conditions, high blood pressure, or other cardiovascular risk factors should also undergo diagnostic testing before starting chemotherapy.

It is advisable to seek diagnostics when any symptoms of heart trouble appear during or after cancer treatment. These warning signs include chest pain, unusual shortness of breath, heart palpitations (feeling your heart racing or fluttering), dizziness, swelling in the legs or abdomen, or reduced ability to perform daily activities. However, one of the challenges with chemotherapy-related heart damage is that it can develop without any symptoms at all, sometimes appearing years after treatment has ended.^[2]

Diagnostic Methods for Identifying Cardiotoxicity

Several well-established diagnostic tools help doctors detect and monitor heart damage in cancer patients. The most fundamental measurement is left ventricular ejection fraction, or LVEF, which tells doctors how well the heart’s main pumping chamber is working. LVEF measures the percentage of blood that leaves the lower left chamber of the heart (the left ventricle) with each contraction. A healthy heart typically pumps out 55% to 70% of the blood in this chamber. When chemotherapy damages the heart, this percentage drops.^[2]

Doctors define cancer therapy-related cardiac dysfunction as a decrease in LVEF of at least 10 percentage points, dropping to a value below 50%.^[4] This specific definition helps identify patients whose hearts have been significantly affected by treatment and who may need medication or changes to their cancer therapy regimen.

The echocardiogram, often simply called an “echo,” is the most commonly used imaging test to detect cardiotoxicity. This non-invasive procedure uses ultrasound waves—the same technology used to view babies during pregnancy—to create moving pictures of the heart. During an echocardiogram, a technician places electrodes on your chest and moves a special probe across your skin. The sound waves bounce off your heart structures and return to create detailed images showing how your heart chambers are moving and how well blood is flowing through your heart valves.^[2]

Cardiac MRI, or magnetic resonance imaging of the heart, is considered by many experts to be the most accurate method for detecting cardiotoxicity. This technology uses powerful magnets, radio waves, and computer processing to create extremely detailed three-dimensional images of the heart’s structures. Cardiac MRI can measure heart function with great precision and can detect even subtle changes in heart muscle tissue. Some specialists view it as the gold standard for identifying chemotherapy-induced heart damage, though it is more expensive and time-consuming than echocardiography.^[2]

A cardiac stress test measures how your heart responds when it has to work harder. During this test, you might walk on a treadmill or pedal a stationary bicycle while connected to monitoring equipment. The test reveals whether your heart can meet the increased demands of physical activity, something that might be compromised if chemotherapy has weakened the heart muscle. This helps doctors understand how your heart functions under real-world conditions, not just when you’re at rest.^[2]

Blood tests measuring specific proteins released by damaged heart cells provide another layer of diagnostic information. Troponin-I is a protein that leaks into the bloodstream when heart muscle cells are injured. Elevated troponin levels can signal that the heart is under stress or being damaged by chemotherapy. Similarly, B-natriuretic peptide, or BNP, is a hormone released by the heart when it’s working too hard or when the heart muscle is stretched. Rising BNP levels can indicate developing heart failure or worsening cardiac function.^[4]

The timing of these diagnostic tests matters enormously. Baseline testing before starting chemotherapy gives doctors a reference point to understand your heart’s normal function. Regular monitoring during treatment—the frequency depends on which drugs you’re receiving and your personal risk factors—allows early detection of problems. Follow-up testing after chemotherapy completion is crucial because heart damage can appear months or even years after the last treatment dose.^[6]

Advanced Diagnostic Techniques

Beyond standard echocardiography, doctors increasingly use a more sophisticated measurement called global longitudinal strain, which assesses how well heart muscle fibers are stretching and contracting. This technique can detect subtle changes in heart function before the ejection fraction drops, potentially allowing even earlier intervention. Global longitudinal strain essentially provides a more sensitive early warning system for cardiotoxicity.^[10]

Some cancer patients may undergo an electrocardiogram, or ECG, which records the electrical activity of the heart. This simple, painless test involves placing small electrodes on the chest, arms, and legs to detect the electrical signals that control heartbeat rhythm. While an ECG cannot directly measure pumping function like an echocardiogram, it can reveal irregular heart rhythms (arrhythmias) or other electrical problems that sometimes result from cardiotoxic chemotherapy.^[2]

Diagnostics for Clinical Trial Qualification

When researchers design clinical trials to test strategies for preventing or reducing chemotherapy-induced heart damage, they establish strict criteria for which patients can participate. These enrollment standards typically center on objective measurements of heart function and specific risk factors that make cardiotoxicity more likely to develop.

Clinical trials evaluating cardioprotective drugs—medications intended to shield the heart from chemotherapy damage—generally require baseline LVEF measurements to ensure participants start with adequate heart function. Researchers commonly set a minimum LVEF threshold, often around 50% or higher, to include patients whose hearts are functioning normally or near-normally at the start of the study.^[4]

Baseline blood tests measuring troponin-I and BNP levels are standard requirements in many cardio-oncology trials. These measurements establish each participant’s starting point and allow researchers to track changes over time. Studies investigating medications like statins, aldosterone receptor antagonists (such as spironolactone), ACE inhibitors (like enalapril), and beta-blockers (such as nebivolol) typically monitor these biomarkers throughout the trial to assess whether the cardioprotective intervention is working.^[4][7]

Many trials require serial echocardiograms or cardiac MRI scans at predetermined intervals—perhaps before chemotherapy begins, at the midpoint of treatment, immediately after treatment completion, and at various follow-up points extending months or years afterward. This schedule allows researchers to identify precisely when heart function changes occur and whether the intervention being studied successfully prevents or reduces those changes.

Patient eligibility for cardio-oncology trials often depends on the specific chemotherapy regimen planned. Trials focused on anthracycline-related heart damage specifically recruit patients scheduled to receive doxorubicin or similar drugs. The cumulative dose of anthracyclines—measured in milligrams per square meter of body surface area—is carefully documented because cardiotoxicity risk increases with higher total doses.^[1]

Some clinical trials specifically enroll high-risk populations, such as patients receiving both trastuzumab and anthracyclines simultaneously, elderly patients, those with diabetes or hypertension, or individuals who have already experienced a decline in heart function. Other studies might exclude patients with pre-existing significant heart disease to focus on prevention rather than treatment of established cardiac problems.

Research Requirements and Data Collection

Clinical trials examining chemotherapy cardiotoxicity attenuation must collect comprehensive data beyond simple heart function measurements. Researchers document all cardiovascular symptoms participants experience, track medication dosages and timing precisely, and monitor for potential drug interactions between cardioprotective medications and chemotherapy agents. Quality-of-life assessments help determine whether interventions improve not just objective measurements but also how patients actually feel.

Recent network meta-analyses—sophisticated statistical methods that compare multiple different interventions across numerous clinical trials—have analyzed data from 33 randomized controlled trials involving 3,285 patients. These analyses require standardized diagnostic criteria across studies to make meaningful comparisons. When trials use different definitions of cardiotoxicity or measure outcomes at different time points, comparing results becomes challenging.^[4][7]

Biomarker-driven intervention studies represent an emerging approach in clinical trial design. In these trials, diagnostic test results—such as rising troponin levels or decreasing LVEF—trigger the start of cardioprotective treatment rather than waiting for symptoms to develop. This strategy attempts to identify the optimal window for intervention, catching heart damage early when it might still be reversible.^[6]