Aspirin vs warfarin: What to prescribe for children post-heart surgery

Morgan Liotta

18/02/2021 4:49:33 PM

New studies have weighed up the benefits of different blood thinning medications for patients who have undergone a specific heart procedure.

Routine monitoring is not required for patients taking aspirin after Fontan surgery, offering considerable benefit, particularly for children.

The research, led by the Murdoch Children’s Research Institute (MCRI) and published in the Journal of Thoracic and Cardiovascular Surgery, has found that despite the benefits of warfarin, aspirin should be offered to prevent blood clotting in children who undergo Fontan surgery.
The procedure is offered to children born with severe heart defects to re-plumb the heart, allowing them to live with one pumping heart chamber instead of two. Most patients are able to live well into adulthood and have relatively normal lives, but may have an increased risk for blood clots – potentially leading to heart failure or stroke.
All patients are given blood thinning medications following Fontan surgery, with warfarin and aspirin the most common.
The study compared the two medications, examining the long-term outcomes of warfarin and the impacts on patients’ bone mineral density (BMD) and risk of bleeding, from 121 patients enrolled in the Australian and New-Zealand Fontan Registry.
Although bleeding rates were high in both groups, they were more frequent in the warfarin group. BMD was reduced in all participants compared with the general population, but also showed weaker levels in the warfarin group.
Lead author of the study, Dr Chantal Attard says the study’s findings are significant for GPs, as they will be continually prescribing the medication to patients.
‘The main thing to keep in mind is where patients don’t have any other underlying conditions – and a large proportion of them will, depending on their cardiac functioning or lung functioning – our studies have shown that there isn’t much of a difference between aspirin and warfarin, so therefore aspirin might be a better choice for those patients,’ she told newsGP.
A considerable benefit for patients – especially younger people – who take aspirin after Fontan surgery, is that routine monitoring is not required.
‘These patients don’t have to be going to get blood tests done or have their INR [international normalised ratio] measured every few weeks, they don’t have to worry so much about interactions with other drugs or certain types of foods,’ Dr Attard explained.
‘So it does have a really important impact on people’s quality of life.’
Warfarin can be affected by food, other medications and conditions, so patients need to have regular blood tests to check their warfarin levels are safe.
‘If you do have a patient who has had Fontan surgery and needs to continue to be on warfarin, it’s really important to be monitoring their BMD over time and making sure it’s not dropping too low,’ Dr Attard said.
Interventions to prevent bone loss for those patients on warfarin include BMD screening using dual-energy X-ray absorptiometry (DXA), recommended from five years of age for children on long-term warfarin, then repeated every 3–4 years if the patient has normal BMD, and every two years where a BMD is considered low.
Dr Attard also recommends monitoring lifestyle factors for BMD, including:

  • 2 –3 serves of dairy a day or supplementation with calcium
  • vitamin D supplementation, at least throughout winter
  • weight-bearing exercise appropriate for individual’s physical ability
  • ensuring puberty is reached at an appropriate time
  • treatment with bisphosphonate should only be considered when fractures and low BMD present together.
Another benefit to consider aspirin over warfarin is the associated costs.
‘When comparing aspirin and warfarin in the Fontan population, for every patient on warfarin, there’s an extra $825 associated cost per year for that patient and about $600 of that actually fell to the patient or their family,’ Dr Attard said.
The study also identified that stroke is common (33%) regardless of which medication the patient took. However, Dr Attard said one of the study’s limitations is that it was cross-sectional, making it difficult to identify when the patient had the stroke.
‘A lot of these strokes are what we call “sub-clinical”, so they were only detected because they were part of our study and [the patient] would come in for an MRI,’ she said.
‘So we don’t know if these strokes had occurred before the surgery. Some of these strokes can even happen in utero, or also because of the surgery.
‘That’s the limitation of doing a cross-sectional study rather than a long-term longitudinal study.’
Along with prescribing appropriate blood-thinning medications as part of their role in delivering preventive care, GPs can ensure these patients are attending regular cardiology appointments and monitoring heart function to prevent risk of stroke, according to Dr Attard.
‘For example, if they are on warfarin, the GP can ensure their INR is an acceptable rate, so they’re not being under-anticoagulated, they’re having enough of the warfarin in their system to actively prevent blood clotting,’ she said.
‘What we’ve found in other [MCRI] studies is that patients who are on warfarin but aren’t adequately anti-coagulated actually have a very similar [stroke] risk to those who don’t take any anticoagulation at all.
‘Some patients, whether they’ve had a Fontan or not, need to be on warfarin for various reasons. So it’s important that if a patient is on warfarin that it’s managed really well.’
Despite the lean towards aspirin for post-Fontan patients, one benefit for using warfarin is the option of INR point-of-care testing, the study found.
The patient or family member/carer measures their INR at home and reports back to a haematology service, which then calculates the warfarin dose for the patient.
‘If patients can measure their INR at home with a special care device, the quality of life for those patients is infinitely better than for those who need to go to their pathology centres or GP clinics to get those blood tests done regularly,’ Dr Attard said.
‘And that’s for a variety of reasons, obviously for convenience, but also it gives those patients a sense of empowerment over their health.’
Quality of life was similar between the warfarin and aspirin study groups, but home INR monitoring was associated with better quality of life scores in the warfarin group.
‘That’s a really important takeaway message for GPs,’ Dr Attard said.
‘If patients do need to be anticoagulated in the long term with warfarin, they should be offering them, or referring them to a service where they can do their own home INR monitoring.’
Around 70,000 post-Fontan patients are alive today, with this number expected to double within two decades. The majority of Fontan procedures are done at Melbourne’s Royal Children’s Hospital – Dr Attard estimates around 50 per year.
‘Although this doesn’t sound like a huge number, it’s actually growing,’ she said
‘As technology and healthcare is improving, a lot of these children who weren’t able to survive previously are now able to survive because of medical advances, such as the Fontan surgery.
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