The number of patients waiting more than six weeks for a heart scan has nearly reached 5,000 in Cambridgeshire and West Essex.
Government data shows that, in September 2021, 1,092 patients waited more than six weeks for an echocardiogram in the NHS West Essex Clinical Commissioning Group area, covering Uttlesford, Harlow and Epping Forest.
A further 3,848 patients waited more than six weeks for an echocardiogram in the NHS Cambridgeshire and Peterborough CCG area.
The data suggests that West Essex patients faced the third-longest waiting lists in the East of England, behind the Norfolk and Waveney area.
Patients in Cambridgeshire and Peterborough faced the longest waiting lists.
A hospital in West Essex confirmed all immediately urgent treatment and surgery has gone ahead.
But BHF experts fear long wait times could have a "domino effect" on care and patient safety.
Dr Sonya Babu-Narayan, associate medical director at the BHF, said: “Waiting lists for heart treatments were too long before the pandemic began, and they are now rising to record levels.
“Without an echocardiogram, doctors can’t see how well the heart is working.
“This matters because the long delays we now see for heart imaging tests create a domino effect of disruption to heart care and treatment that ultimately puts lives at risk.
"This is tragic when effective heart treatments exist."
The BHF compared the September 2021 dataset with figures from February 2020, when 15 patients waited more than six weeks for an echocardiogram in West Essex.
In Cambridgeshire and Peterborough, this figure stood at just 10.
Princess Alexandra Hospital in Harlow cares for some West Essex cardiology patients.
Stephanie Lawton, chief operating officer at PAH NHS Foundation Trust, said: "Our echocardiogram services have been impacted by the pressures of the Covid-19 pandemic, which is an issue nationally.
“We have a range of measures in place to reduce the number of patients who are waiting for investigations, including recruiting additional specialist clinicians to review patients on the waiting list."
She said patients are always treated in the order of clinical need.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here