September 24, 2013 By Jill Margo
The figures look worrying. Could it be true that one in 11 patients having a major operation in hospital will have a small, hidden heart attack?
Researchers from the prestigious Cleveland Clinic in Ohio suggest this is the case among patients having major non-cardiac surgery.
Their heart attacks are silent with no signs or symptoms to show they have occurred.
More worrying is the suggestion that one in 10 of those who have such a silent event will die within 30 days of their operation.
The data was presented in Dublin at the recent annual congress of the Association of Anaesthetists of Great Britain and Ireland.
It showed 80 per cent of post-operative heart attacks were silent and only detected through testing blood for a marker called troponin.
Troponin is the best indicator of a post-surgical heart attack and although it is a quick, cheap test, few have it following their operation.
The conference was told more should have it so they can receive timely treatment, should they need it.
No clinical symptoms
In Australia, troponin testing is widely performed but not necessarily routinely around the time of surgery.
After surgery, while many patients appear outwardly to be recovering well, four of five who have a post-operative heart attack will show no clinical symptoms. They will have no chest pain and no shortness of breath.
Their electrocardiograms and echocardiograms will be normal too, says professor Daniel Sessler, chair of the department of outcomes research at the Cleveland Clinic, who addressed the conference.
Thus, he says, doctors miss most of these events unless they do the test.
If a silent heart attack is discovered, he says there are different ways of treating it but, at very least, the patient should be started on aspirin.
Other options include angiography, stenting or treatment with anticoagulant drugs.
Preventing silent heart attacks
The real issue is how to prevent the silent heart attack in the first place.
Sessler said low blood pressure during surgery is strongly associated with both kidney injury and heart attacks.
Of the estimated 240 million non-cardiac surgeries performed globally each year, it is thought one-third are moderate to high-risk surgeries.
These are defined as surgeries on people 45 and older which require at least one night in hospital.
Professor Garry Jennings, director of the Baker IDI Heart and Diabetes Institute in Melbourne, says it has always been known that heart attack rates are higher around the time of major surgery.
“However, the availability in recent years of high-sensitivity troponin measurements has increased detection rates,” he says.
“The question is whether small rises in troponin always indicate whether a heart attack has occurred, given that there are many other things happening at the time that might cause troponin to be present in a blood sample.
Jennings says the 10 per cent death rate cited in this study seems high.
The authors were wise to draw attention to the lack of clarity on effective preventive measures and treatment when a silent heart attack has occurred.
However, avoiding low blood pressures and major haemorrhage during or immediately after surgery is important, he says.
So is taking the right steps before surgery such as ensuring that cardiac risk factors – high blood pressure, cholesterol, diabetes and smoking – are well controlled .