Heart problems

Some types of cancer treatment can damage the heart. These treatments include chemotherapy, targeted therapy, immunotherapy, hormone therapy and radiation therapy. Heart damage caused by cancer treatment is also called cardiotoxicity.

Heart problems can develop during treatment or years later. Cancer treatment doesn’t often cause heart damage in children, but they may develop problems as adults.

Some heart problems go away once you change or stop treatment. Others may be permanent.

The heart is a part of the cardiovascular system, which is made up of the heart, blood and blood vessels. Blood vessels are long, elastic hollow tubes that carry blood, oxygen and nutrients to and from the heart. The heart pumps blood back and forth around the body.

The heart is a muscular organ surrounded by a thin membrane. It consists of 4 chambers, valves and blood vessels.

• The right atrium and the left atrium are the 2 upper chambers of the heart (called atria). They collect the blood that is being carried into the heart.
• The right ventricle and the left ventricle are the 2 lower chambers. They pump the blood out of the heart into the body.
• The pericardium is a thin membrane that surrounds the heart, protecting and anchoring it in the chest.
• Valves in the heart open and close as the heart pumps. They keep the blood flowing in one direction. 
• Blood vessels carry blood with oxygen to and from the heart muscle.

Veins and arteries are different types of blood vessels that transport blood to and from the heart. They also carry waste products away from cells and organs.

Veins bring blood that is low in oxygen to the heart. The heart pumps the blood to the lungs, where it gets more oxygen. The blood then travels back to the heart. Veins also have valves to keep the blood flowing in the right direction.

Arteries deliver blood with oxygen from the heart to the rest of the body. The heart has its own arteries (called the coronary arteries) that carry blood and oxygen to the heart muscle.

The heart receives electrical signals that tell it when to beat.

The sinus node is a group of cells in the heart that control the rhythm and rate of heartbeats, or contractions. The sinus node sends electrical signals through the heart to start each heartbeat.

A normal resting heart rate for an adult is between 60 and 100 beats a minute. It may be lower in adults who are in very good physical condition, like athletes. C hildren have higher heart rates than adults.

Your heart rate can be affected by factors including age, smoking tobacco, weight, medicines and stress. If your heart rate is too high or too low, you are at a greater risk of heart problems.

The following cancer treatments can damage the heart.

Heart problems are often linked to the total dose of the chemotherapy drug you are given. The higher the dose, the more likely the drug is to cause heart damage. Your risk of heart problems also increases if your treatment includes a combination of chemotherapy drugs or chemotherapy combined with targeted therapy.

Lower doses of drugs can also damage the heart if you’ve previously had radiation therapy to the chest.

Chemotherapy drugs that can cause heart damage include:

• anthracycline drugs such as doxorubicin, daunorubicin and epirubicin
• cyclophosphamide

• fluorouracil (also called 5-fluorouracil or 5-FU)

Targeted therapy drugs that can cause heart damage include:

• trastuzumab (Herceptin and biosimilars)
• pertuzumab (Perjeta)
• sunitinib (Sutent and biosimilars)
• sorafenib (Nexavar and biosimilars)
• bevacizumab (Avastin and biosimilars)
• carfilzomib (Kyprolis)
• ponatinib (Inclusig)
• dasatinib (Sprycel)
• bosutinib (Bosulif)

Because immunotherapy is a newer treatment, researchers are still studying how these drugs can affect the heart. Immunotherapy drugs that can cause heart problems include:

• nivolumab (Opdivo)
• pembrolizumab (Keytruda)
• atezolizumab (Tecentriq)
• avelumab (Bavencio)
• durvalumab (Imfinzi)
• ipilimumab (Yervoy)
• tremelimumab (Imjudo)

Luteinizing hormone–releasing hormone (LHRH) agonists are hormone therapy drugs that stop the testicles from making testosterone. They are also called gonadotropin–releasing hormone (GnRH) agonists. These drugs are used to treat prostate cancer.

LHRH agonists that increase the risk of heart problems include:

• leuprolide (Lupron, Lupron Depot, Eligard)
• goserelin (Zoladex)
• triptorelin (Trelstar)

Other types of hormone therapy for prostate cancer do not increase the risk as much as LHRH agonists.

External radiation therapy to the chest, abdomen or spine or total body irradiation can cause heart problems.

The risk of heart damage increases based on the total dose of radiation to the chest and amount of heart tissue in the radiation treatment field. Heart problems linked to external radiation therapy are less common than in the past because of changes in treatment methods and doses of radiation. Treatment can now deliver very precise radiation beams and protect the surrounding tissues. Heart problems are more common when the left side of the chest is given radiation therapy, as there is a larger area of the heart in the area that is being given radiation.

The risk of heart problems is higher when radiation is given with chemotherapy drugs that can also damage the heart.

Damage to the heart can develop many years after treatment. Some problems appear as late as 30 years after radiation therapy is finished.

Other factors that can increase the risk of developing heart problems during cancer treatment include:

• age – being younger than 18 or older than 65
• previous cancer treatment with anthracycline drugs or trastuzumab
• a history of heart problems
• having high blood pressure (also called hypertension), which can also be caused by targeted therapy drugs and LHRH agonists
• smoking tobacco
• having high cholesterol
• having overweight or obesity

The following types of heart problems can develop from cancer treatment.

Cardiomyopathy is a disease of the heart muscle that makes it stiff, thick or enlarged. When this happens, the heart has a harder time pumping the blood to the rest of the body.

Reduced left ventricular ejection fraction (LVEF) is a sign of cardiomyopathy. LVEF is a measurement of how much blood is pumped out of the left ventricle of the heart to the body each time it contracts. The left ventricle is measured because it is the main pumping chamber of the heart.

A healthy heart has an LVEF of 50% to 70%. A lower LVEF shows that your heart isn’t pumping blood properly because the heart muscle is damaged. LVEF is usually measured during an echocardiogram, but other imaging tests or a nuclear scan may also be used.

Cardiomyopathy can lead to heart failure. Heart failure happens when the heart doesn’t pump blood very well and it starts to build up in other parts of the body, like the lungs, legs and feet. Without treatment, heart failure can be life-threatening. Heart failure is also called congestive heart failure.

Chemotherapy (especially doxorubicin), targeted therapy, immunotherapy and radiation therapy to the chest can cause cardiomyopathy and other problems that lead to heart failure.

An irregular heartbeat (arrhythmia) is when the heart does not beat normally. It may beat too fast, too slow or in an unsteady rhythm.

Chemotherapy, targeted therapy, immunotherapy and radiation therapy can cause the following types of arrhythmias.

Atrial fibrillation is when the heart beats irregularly due to abnormal electrical signals in the atria. The heart rate may also be too fast. Atrial fibrillation can increase the risk of a stroke.

Ventricular tachycardia is when the ventricles are pumping too fast and blood doesn't get pumped to the rest of the body. It’s caused by abnormal electrical signals in the ventricles.

Long QT syndrome is caused by the heart cells taking longer than normal to recharge and recover in the time between heartbeats. The QT interval is the time between heartbeats.

A heart block happens when the electrical signals that make the heart beat have problems moving from the top of the heart muscle to the bottom. This causes the heart to beat too slowly or skip beats.

Atherosclerosis is a buildup of a fatty substance called plaque on the artery walls.

Atherosclerosis can narrow the artery, which makes it harder for blood to flow through. It can also block an artery or break off the artery wall, which can form a blood clot. A blood clot can cause a heart attack when it blocks blood from getting to the heart. It can also cause a stroke when it blocks the blood supply to the brain.

Immunotherapy, LHRH agonists and radiation therapy can cause atherosclerosis that develops more quickly than normal (called accelerated atherosclerosis).

Atherosclerosis can affect different arteries in the body.

Coronary artery disease is when a buildup of plaque causes the coronary arteries to become blocked or narrowed. This stops the heart from getting oxygen from the blood, which can lead to heart attacks or heart failure. External radiation therapy to the chest and chemotherapy and immunotherapy drugs can cause coronary artery disease.

Carotid artery stenosis affects the carotid arteries, which are the blood vessels that supply blood to the brain. There are 2 carotid arteries, one on each side of the neck. Carotid artery stenosis is when one or both of the carotid arteries become narrow or hardened, making it harder for blood to flow to the brain. If a blood clot forms, it can block the blood supply to the brain for a short time and cause a small stroke (called a transient ischemic attack or TIA). If the blood clot continues to cut off the blood supply to the brain, it is called an ischaemic stroke.

People who have had external radiation therapy to the head and neck have an increased risk of carotid artery stenosis.

Heart valve damage (stenosis) is when the heart valves become stiff or thick. When this happens, the opening of the heart narrows and less blood can flow to the body.

External radiation therapy can damage the heart valves if the radiation is directed at the heart.

A pericardial effusion is a buildup of fluid between the pericardium and the heart muscle. Different cancer treatments can cause a pericardial effusion, including chemotherapy drugs like anthracyclines and cyclophosphamide and targeted therapy drugs such as ponatinib, dasatinib and bosutinib.

Cardiac tamponade is a complication of pericardial effusion. When the pericardium fills with blood or other fluids, it puts pressure on the heart. This pressure stops the heart from pumping properly, making it beat faster to try to pump more blood. Cardiac tamponade is a medical emergency and needs to be treated right away.

Immunotherapy drugs can cause cardiac tamponade.

Myocarditis is an inflammation of the heart muscle. It can be caused by immunotherapy drugs.

Pericarditis is an inflammation of the pericardium, the thin lining surrounding the heart. Constrictive pericarditis is a hardening of the pericardium, which occurs when the inflamed lining becomes thicker and stiffer than normal. External radiation therapy to the chest can cause pericarditis and constrictive pericarditis.

Symptoms of heart problems can vary depending on the type of problem. Mild to moderate heart problems may not cause any symptoms. Heart problems may only be found when diagnostic tests are done.

Symptoms of heart problems include:

• shortness of breath
• dizziness, fainting or feeling light-headed
• severe fatigue that prevents exercise or normal life activities
• chest pain
• sweating, nausea or shortness of breath with chest pain
• sharp pain in the centre or left side of the chest (often worsens when taking a deep breath)
• heart racing or throbbing, or feeling like it is skipping beats
• swelling in the feet, ankles or abdomen
• a cough and wheezing that don’t go away
• flu-like symptoms such as headache, fever or joint pain
• enlargement of the veins of the neck

If symptoms get worse or don’t go away, tell your healthcare team or cardiologist right away.

Before you start cancer treatment, the healthcare team usually does tests to check your heart. These tests may check heart rate and rhythm and how well the heart muscle pumps blood. They may also look at your heart valves or how your heart works during exercise. Tests are repeated during and after treatment to look for any changes.

These tests may include:

• an electrocardiogram (ECG)
• an echocardiogram (echo)
• a transesophageal echocardiogram – a flexible tube is placed down the throat and into the esophagus to look closely at the heart valves
• a multigated acquisition (MUGA) scan
• ultrasound
• cardiac catheterization – a long flexible tube is inserted into a blood vessel in the groin and guided through the blood vessel to the heart
• MRI
• a stress test – usually done on a treadmill
• blood chemistry tests to look for certain cardiac biomarkers

Cardiac biomarkers are proteins that are released by the heart into the blood when the heart has been damaged or stressed. When these are found during a blood test, it shows that there may be a problem with the heart. The cardiac biomarkers that may be measured are troponin and natriuretic peptides (NP) such as NT proBNP.

Your healthcare team may refer you to a cardiologist before starting cancer treatment. You may also be referred to a cardio-oncologist, which is a cardiologist who specializes in preventing and treating heart problems caused by cancer treatment.

To prevent heart damage, the healthcare team carefully monitors people who are at risk. If tests show that the heart is damaged, they may lower the dose of the drug or radiation or stop the treatment entirely to prevent further damage.

You may already have certain metal devices placed in your body to treat heart problems. A pacemaker prevents your heart rate from being too slow and an implantable cardiac defibrillator shocks your heart when you have an abnormal and dangerous heartbeat. It’s important to tell your healthcare team if you have one of these devices. Radiation therapy or some diagnostic scans may stop these devices from working properly. Your healthcare team will use diagnostic tests and treatments that don’t affect the device. They will also monitor how well the device is working during your treatment.

If the heart tests show that your heart is healthy but you are having treatment that can damage the heart, your healthcare team or cardiologist may put you on heart medicines to reduce your risk.

If you have high cholesterol before you start treatment, your healthcare team may give you cholesterol-lowering medicines (called statins) to lower your risk of developing heart problems.

You can lower your risk of heart problems by:

• not smoking tobacco, or quitting smoking if you currently smoke
• getting to and staying at a healthy body weight
• eating well
• exercising moderately on a regular basis

If you have heart damage after cancer treatment, your healthcare team will refer you to a cardiologist. Further treatments may include:

• medicines to treat heart problems
• surgery to treat coronary artery disease or replace a damaged heart valve

If treatment causes heart problems, you will need to take precautions to protect your heart for the rest of your life. You will need to do the following:

• Check with your healthcare team before playing sports or beginning any exercise program. Aerobic exercise is generally safe and beneficial for the heart. But some types of exercise are particularly stressful to the heart.

• Avoid recreational drugs that can increase your heart rate and blood pressure and cause an irregular heartbeat, such as marijuana, cocaine, LSD, methamphetamine, ecstasy (MDMA) and sniffing solvents.

If treatment has damaged a heart valve, you may also need to take antibiotics before dental work or invasive surgeries or procedures, like an endoscopy. Your cardiologist may prescribe these medicines to prevent a serious infection of the heart (called endocarditis) that can happen if bacteria enters the bloodstream.

All people who are treated for cancer need regular follow-up. The healthcare team will develop a follow-up plan based on the type of cancer, how it was treated and your needs.

Follow-up may include a physical exam and one or more of the following heart function tests:

• a MUGA scan
• an echocardiogram (echo)
• an electrocardiogram (ECG)
• transesophageal echocardiogram
• ultrasound