Thousands of heart patients in England could be at increased risk of stroke or bleeding as a result of their medical treatment not being managed effectively by their local NHS trust, a charity has warned.
Anticoagulation UK said it has revealed a range of deficiencies in care and monitoring for patients with atrial fibrillation (AF), a common condition which causes an irregular and often abnormally fast heart rate.
Patients require long-term treatment with a particular type of medicine known as an anticoagulant to reduce their risk of stroke.
Warfarin is the most frequently prescribed anticoagulant and the charity said regular monitoring of its levels via blood tests was regarded as essential, since there was a only a small therapeutic window in which the medicine was effective.
If there is too little of the medicine in the body it does not reduce the risk of stroke, and if there is too much it increases the risk of haemorrhage or bleeding.
Anticoagulation UK said it submitted Freedom of Information (FoI) requests to NHS Trusts in England and found more than 37,000 warfarin patients were experiencing inadequate anticoagulation control.
It also found more than 29,000 warfarin patients were recorded as spending less than two thirds (65%) of the time in the correct therapeutic range (TTR), putting them at an increased risk of stroke or bleeding.
Meanwhile up to 42% of trusts do not routinely collect data on the time a patient spends in therapeutic range (TTR) and the international normalised ratio (INR) of patients taking warfarin, so are potentially unaware of the number of patients in their care who are at risk.
The charity's chief executive, Eve Knight, said the results were "extremely concerning".
"Inadequate anticoagulation control and poor monitoring are significant threats to patient safety which requires immediate attention," she added.
"The risks of poor warfarin control have been well known for many decades, so it is especially disappointing to find that so many examples of inadequate practice still exist.
"We know that many trusts did not respond, so the true number of those at risk could be even higher, with this total representing only the tip of the iceberg."
Anticoagulation UK wrote to 149 NHS trusts in England, receiving responses from 91 (61%).
The audit also found that one in 10 trusts provides no information, education or support materials to patients taking anticoagulation, and 62% had no written systems in place for reassessing AF patients with poor anticoagulation control.
AF is the most common heart rhythm disturbance, affecting around one million people in the UK, according to NHS Choices.
Dr David Hargroves, consultant physician and clinical lead for stroke at East Kent Hospitals University NHS Foundation Trust, said: "It is critical that NHS Trusts collect and are able to access data that enables them to identify areas for improvement in patient safety and care.
"It is also important that information and support is in place to help patients make informed decisions about the treatment and care that is right for their needs.
"As part of this, all patients should have the opportunity to discuss their anticoagulation treatment options with a healthcare professional as part of their regular reviews to ensure they are getting the intended benefits from their current treatment."