Medical Oncologist
HER2-positive breast cancer
What happens if your heart function drops during treatment?
If a heart scan shows a drop during trastuzumab, treatment is usually paused, the scan repeated and heart medicines sometimes started. In most people heart function recovers, and many restart and finish their course. This page explains, in general terms, what usually happens and what to watch for.
NG
Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
On this page
- What happens if my heart scan shows a drop?
- What usually happens after a drop is found
- How things often turn out, in general terms
- Symptoms to report straight away
- The vocabulary, in plain language
- What to expect honestly
- What restarting treatment usually looks like
- Managing anxiety about your heart
- Other reasons a heart result can change
- What people assume about a heart function drop
- Common questions after a heart function drop
The short answer
What happens if my heart scan shows a drop?
Usually, your team pauses the HER2-targeted treatment, repeats the scan after a few weeks, and may start heart medicines to help the heart recover. In most people whose heart function falls during trastuzumab, it improves once treatment is paused, and many are able to restart and finish their planned course. A drop is a reason for careful action, not a reason to panic.
Why it is usually reversible
Trastuzumab affects how heart muscle cells work rather than destroying them. Once the drug is paused, the cells can recover their pumping strength, often within weeks to a few months.
What decides the response
How far the result has fallen, whether it is still within the normal range, whether you have symptoms, and how important continued HER2 treatment is for your cancer.
When stopping for good is considered
If heart function does not recover, falls again after restarting, or you develop significant heart failure, your team may decide the risk of continuing outweighs the benefit.
This page gives general information only. Decisions about your treatment are made by your oncology and cardiology team.Step by step
What usually happens after a drop is found
Your oncologist reviews the result
They compare it with your baseline and earlier scans, and ask about breathlessness, swelling or palpitations.
Treatment is paused if needed
For a significant fall, the next HER2-targeted doses are held. Hormone therapy and radiation can often continue.
A cardiology opinion
A cardiologist may check your heart, blood pressure and medicines, and look for other causes of the change.
Heart medicines may be started
Medicines that ease the strain on the heart are often used to help recovery, sometimes continued for a while afterwards.
A repeat scan
Usually after a few weeks. If heart function has recovered enough, HER2 treatment is restarted, with closer monitoring.
Possible outcomes
How things often turn out, in general terms
Situation
Usual path
Small fall, no symptoms
Often continue with an earlier repeat scan
Larger fall, recovers on repeat scan
Restart treatment with closer monitoring
Fall with symptoms
Pause, heart medicines, cardiology care
Does not recover after a pause
Stopping HER2 treatment may be discussed
Falls again after restarting
Risks and benefits reviewed afresh
Warning signs
Symptoms to report straight away
Many drops cause no symptoms, which is why scans matter. But these signs need prompt attention.
Breathlessness
Especially on light activity, when lying flat, or waking at night short of breath.
Swelling
Swollen ankles or legs, or sudden weight gain over a few days, can mean fluid is building up.
Weigh yourself if your team asks.A racing or irregular heartbeat
Palpitations, or a heartbeat that feels uneven, are worth reporting promptly.
Unusual tiredness or dizziness
Tiredness out of proportion to your usual pattern, or feeling faint, should be mentioned.
Seek urgent help if
- You have chest pain
- You are breathless at rest
- You faint
Words you will hear
The vocabulary, in plain language
- Ejection fraction
- The share of blood pumped out of the main heart chamber with each beat.
- Treatment hold
- A pause in HER2-targeted doses while the heart recovers.
- Rechallenge
- Restarting treatment after heart function has recovered.
- Cardioprotective medicines
- Heart medicines used to help the heart recover and protect it.
- Heart failure
- When the heart does not pump well enough, causing breathlessness or swelling.
- Cardio-oncologist
- A heart specialist focused on people receiving cancer treatment.
Talk to our team
Have a question about your situation?
Call the helpline or leave your details, and someone will help you arrange a consultation at the CION centre nearest you. One helpline serves every CION centre.
Call 1800 202 8726
Helpline open 24/7
Being straight with you
What to expect honestly
Hearing that your heart has been affected is frightening, especially in the middle of cancer treatment. The reassuring truth is that most falls in heart function on trastuzumab are mild and recover, and many women complete their planned treatment.
A pause rarely changes the outcome much
A short break to protect your heart is unlikely to make a large difference to how well treatment works. Your oncologist weighs both concerns carefully.
Sometimes treatment does stop early
For a minority, heart function does not recover enough to continue safely. In that case your team explains what the treatment you have already had is likely to have achieved, and what other options there are.
Your heart may need follow-up
After a drop, you may be asked to have further scans or continue heart medicines for a while after treatment ends.
What this page cannot tell you
It cannot predict how your heart will recover. Ask your team what your results show and what the plan is if they change again.
Going back on treatment
What restarting treatment usually looks like
If your heart recovers, restarting HER2-targeted treatment is common. Most women who restart go on to complete their course without another significant drop.
Closer monitoring
Scans are often repeated more frequently after restarting, so any new change is picked up quickly. Keep every appointment, even when you feel well.
Heart medicines may continue
If you were started on heart medicines, you may be asked to keep taking them while treatment continues. Do not stop them on your own.
Timing of the remaining doses
The pause shifts your finishing date. Your team will explain how many doses remain and set new dates.
Coping with the worry
Managing anxiety about your heart
After a heart scan change, every flutter or breathless moment can feel alarming. That is a natural response, and there are ways to make it easier.
Know your warning signs
Having a clear written list of symptoms that need a call helps you tell the difference between everyday sensations and signs that need action.
Ask for your results in plain terms
Understanding whether your heart is recovering, stable or needs more attention reduces uncertainty. Ask your team to explain each scan.
Share the load
Talking with family, a counsellor or others who have been through heart changes during treatment can ease the worry.
Not always the drug
Other reasons a heart result can change
A lower result is not always caused by HER2 treatment. Your team will usually look for other explanations before deciding what to do.
Earlier chemotherapy
Some chemotherapy drugs given before trastuzumab can affect the heart in a different and less reversible way, so your full treatment history matters.
Blood pressure, infection and low blood counts
Uncontrolled blood pressure, a recent infection, a low haemoglobin or thyroid problems can all make the heart work harder and lower a result.
Differences between scans
A scan done at a different centre, or by a different method, may give a slightly different number without any real change in your heart.
Commonly believed
What people assume about a heart function drop
A drop means permanent heart damage.
Trastuzumab's effect on the heart is usually reversible. Most people recover heart function once treatment is paused.
Once paused, HER2 treatment can never restart.
Many women restart after their heart recovers and go on to complete their planned treatment.
The pause will let my cancer come back.
A short pause is unlikely to make a large difference to the outcome. Protecting your heart is part of good cancer care.
Heart medicines mean I now have heart disease for life.
These medicines are often used to support recovery and may be stopped later. Your cardiologist will advise how long they are needed.
Questions we are asked
Common questions after a heart function drop
How long does the heart take to recover?
Often within a few weeks to a few months after pausing treatment. Your team will repeat the scan to check, and the timing varies from person to person.
Can I continue hormone therapy during the pause?
Usually yes. Hormone therapy does not typically affect heart pumping in the same way. Your oncologist will confirm what continues.
Will I need to see a heart specialist?
Often yes, especially if the fall is significant or you have symptoms. Many centres work closely with cardiologists.
Can I exercise?
Gentle activity is often encouraged, but ask your team first after a drop. They will advise what level is safe while your heart recovers.
Does pertuzumab or T-DM1 affect the heart too?
They can, in a similar way. Monitoring continues whichever HER2-targeted drugs you receive.
Should I cut salt from my diet?
Reducing very salty foods can help if fluid is building up. Ask your team for specific advice.
What if I feel breathless at night?
Contact your team the same day. If you are very breathless at rest or have chest pain, seek emergency help.
Where can I read about my own treatment?
Your oncology team will give you written information about your HER2 treatment and heart monitoring. Use that as your main reference.
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Talk to our team
Speak to a breast cancer specialist
Call the helpline or leave your details, and someone will help you arrange a consultation at the CION centre nearest you. One helpline serves every CION centre.
Call 1800 202 8726
Helpline open 24/7
Sources
- European Society of Cardiology — Guidelines on cardio-oncology
- American Society of Clinical Oncology — Prevention and monitoring of cardiac dysfunction in survivors of adult cancers
- Cancer Research UK — Trastuzumab (Herceptin)
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.