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Cancer treatments can be very effective, but some of these treatments may occasionally affect the heart, by putting it under extra strain. 

This strain can impact the heart in different ways, it may reduce how hard it can pump, it might change the rhythm of the heart (see Arrythmias), it might affect the blood pressure or inflame the heart muscle (this is known as myocarditis). These problems might be temporary or long term, some of these problems may develop years later. 

If you are having a treatment that might affect your heart, before starting treatment, your oncology team may arrange baseline heart checks, to help identify your individual risk and to guide how you are monitored during treatment.  

These tests can include: 

  • A review of your medical history 
  • Physical examination 
  • An ECG (electrocardiogram) 
  • An echocardiogram (heart scan) 
  • Blood tests for heart markers (troponin and natriuretic peptides) 

Looking After Your Heart During Cancer Treatment 

There are many ways to support your heart health while undergoing cancer treatment: 

  1. Lifestyle Measures
  • Eating a heart‑healthy diet (see Nutrition) 
  • Staying active with gentle exercise (see Physical Activity) 
  • Avoiding smoking (see Smoking) 
  • Managing stress (see Stress) 
  1. Medications for Heart Protection

For people at higher risk, your doctor may suggest medicines that help protect your heart, such as beta‑blockers, ACE inhibitors, or statins. These are used when appropriate to reduce the chance of heart problems developing. 

When to ask for help 

Contact your healthcare team if you notice any of the following: 

  • New or worsening breathlessness 
  • Swelling in your legs or feet 
  • Chest discomfort 
  • Irregular heartbeat or palpitations 
  • Unusual tiredness 

These symptoms can have many causes, but it’s important to get them checked. 

Further Information 

Heart health and cancer treatment 

MAC14637 Heart health and cancer treatment E04 

British Heart Foundation (BHF) The biggest independent funder of heart and circulatory research in the UK – BHF 

Cardiac Arrhythmias in Cancer Patients

Types of Cardiac Arrhythmias in Cancer Patients

Cardiac arrhythmias are changes in the normal rhythm of your heartbeat. Your heart may beat too fast, too slow, or irregularly. In people with cancer, arrhythmias can be caused by the cancer itself, certain treatments, changes in electrolytes, infections, anaemia, or stress.

  1. Atrial Arrhythmias (Upper Heart Chambers)

Atrial Fibrillation (AF) 

What it is: An irregular and often fast heartbeat.
Common symptoms: Palpitations, tiredness, breathlessness, dizziness.
Possible causes in cancer: 

  • Chemotherapy (e.g., anthracyclines, 5-FU) 
  • Radiotherapy to the chest 
  • Surgery and post-operative stress 
  • Electrolyte imbalance, anaemia, infection 

Why it matters: AF increases the risk of stroke. Some people may need blood-thinning medicines. 

Atrial Flutter 

What it is: A fast, regular rhythm.
Symptoms: Palpitations, tiredness, dizziness.
Causes: Similar to AF; may also occur after surgery or due to some medicines. 

Supraventricular Tachycardia (SVT) 

What it is: Sudden episodes of a very fast heartbeat starting above the ventricles.
Symptoms: Palpitations, chest discomfort, shortness of breath.
Causes: Some anti-nausea or cancer medicines, stress, electrolyte imbalance. 

  1. Ventricular Arrhythmias (Lower Heart Chambers)

These arrhythmias can be more serious. 

Premature Ventricular Contractions (PVCs) 

What it is: Extra heartbeats that may feel like a skipped beat or flutter.
Symptoms: Usually mild; occasional palpitations.
Causes: Electrolyte imbalance, chemotherapy, stress.
Why it matters: Frequent PVCs can sometimes lead to more serious arrhythmias. 

Ventricular Tachycardia (VT) 

What it is: A fast, regular heartbeat from the ventricles.
Symptoms: Palpitations, dizziness, chest pain, fainting.
Causes: Cardiotoxic chemotherapy, heart muscle damage, electrolyte imbalance.
Why it matters: VT can be life-threatening and needs urgent medical attention. 

Ventricular Fibrillation (VF) 

What it is: A chaotic, ineffective heartbeat where the heart cannot pump blood.
Symptoms: Collapse or sudden cardiac arrest.
Causes: Severe heart damage or advanced cardiotoxicity.
Why it matters: Medical emergency requiring immediate defibrillation. 

  1. Bradyarrhythmias(Slow Heart Rhythms) 

What they are: Heartbeats that are slower than normal (below 60 beats per minute). 

Types 

  • Sinus bradycardia: A slow but regular heartbeat, sometimes caused by medication. 
  • Heart block: A delay or blockage in the heart’s electrical signals. 

Possible causes in cancer 

  • Some chemotherapy drugs (e.g., paclitaxel) 
  • Electrolyte imbalance 
  • Damage from chest radiotherapy 

Why it matters: Can cause tiredness, dizziness or fainting; some people may need a pacemaker. 

  1. Mixed or Complex Arrhythmias

Patients may experience combinations of arrhythmias (e.g., AF with PVCs).
Symptoms may worsen with: 

  • Stress 
  • Fever 
  • Anaemia 
  • Infection 
  • Electrolyte imbalance 

Key messages about arrythmias 

  • Look out for new or worsening symptoms. 
  • Keep a record of when symptoms happen and any triggers. 
  • Take your heart and cancer medicines exactly as prescribed. 
  • Report symptoms promptly to your healthcare team. 

Symptoms to Watch For 

  • Palpitations (racing, fluttering, or skipped beats) 
  • Dizziness or fainting 
  • Shortness of breath 
  • Chest discomfort 
  • Fatigue 

Preventing and Managing Heart Arrhythmias 

Lifestyle changes that support heart health can also help reduce the risk of heart arrhythmias. Consider these strategies: 

  • Avoid smoking. 
  • Eat a healthy diet with less salt and saturated fat. 
  • Stay active, aiming for at least 30 minutes most days of the week. 
  • Maintain a healthy weight (BMI). 
  • Manage stress through relaxation techniques or mindfulness with relaxation, breathing exercises, or hobbies you enjoy. 
  • Control health conditions such as high blood pressure, high cholesterol, and diabetes. 
  • Get enough sleep, ideally 7–9 hours each night. 
  • Limit caffeine and alcohol. 

Self-Management Tips 

  • Monitor your heart rate and symptoms, keeping a record to notice any patterns. 
  • Stay well-hydrated and maintain a healthy balance of electrolytes; your healthcare team may check these with blood tests. 
  • Take medications as prescribed—do not stop or adjust doses without consulting your team. 
  • Stay in regular contact with both your oncology and cardiology specialists. 

When to Seek Help Immediately 

Call your healthcare team or emergency services if you experience: 

  • Sudden, severe palpitations or very irregular heartbeat 
  • Fainting, dizziness, or chest pain 
  • Shortness of breath or swelling in legs 
  • Any new symptoms during chemotherapy or radiotherapy 

Factors That May Increase the Risk of Arrhythmias 

Certain health conditions and lifestyle factors can make arrhythmias more likely. These include: 

  • Existing heart disease
    Conditions such as coronary artery disease,previous heart attacks, heart valve problems, cardiomyopathy, heart failure, or a history of heart surgery can all affect the heart’s electrical system. It is important to keep your cardiology team updated on any ongoing oncology care. 
  • High blood pressure
    Over time, high blood pressure can cause the heart muscle to stiffen or thicken, which may disrupt normal electrical signals. Maintaining good blood pressure control is therefore important.  

Factors that can help reduce high blood pressure include: 

  • Reducing salt intake 
  • Maintaining a healthy weight 
  • Regular physical activity 
  • Limiting alcohol intake 
  • Stopping smoking 
  • Managing stress 
  • Taking prescribed blood pressure medicines as directed 
  • Congenital heart conditions
    Heart problems present from birth can sometimes affect the heart’s rhythm.
  • Thyroid disorders
    Both an overactive (hyperthyroidism) and underactive (hypothyroidism) thyroid gland can trigger irregular heart rhythms. This can be investigated by your cardiology or oncology team, as well as your GP.
  • Obstructive sleep apnoea
    Breathing pauses during sleep can lower oxygen levels and place strain on the heart, increasing the risk of slow or irregular rhythms. Your GP can arrange further assessment if this is suspected.
  • Electrolyte imbalance
    Low orhigh levels of electrolytes such as potassium, sodium, calcium and magnesium can interfere with the heart’s electrical activity. It is important to have these checked by a healthcare professional before taking any supplements.
  • Certain medications or supplements
    Some prescription medicines, over-the-counter treatments (including some cold and flu remedies), and supplements may increase the risk of arrhythmias.
  • Excessive alcohol intake
    Excessive alcohol consumption can interfere with cardiac electrical activity and increase the likelihood of atrial fibrillation. Adopting a balanced lifestyle and limiting alcohol intake can support better heart health.
  • Stimulants such as caffeine,nicotineor recreational drugs
    These can make the heartbeat faster or irregularly. Drugs such as cocaine or amphetamines can be particularly dangerous and may cause severe, life-threatening arrhythmias like ventricular fibrillation. 

Useful Resources  

British Heart Foundation (BHF): Information about arrhythmias and heart health. The biggest independent funder of heart and circulatory research in the UK – BHF  

Macmillan Cancer Support: Guidance on cancer treatment and heart effects. Macmillan Cancer Support | The UK’s leading cancer care charity 

Arrhythmia Alliance: Patient support and educational information. Home – Arrhythmia Alliance – UK