Heart attack survivors who carry excess fat around their waist are at increased risk of repeat cardiac episodes, according to the largest-ever study of its kind.

Previous studies have shown that abdominal obesity is an important risk factor for having a first heart attack.

However, the association between abdominal obesity and the risk of a subsequent heart attack, or stroke was unknown till now.

"Patients are typically put on a stringent medical treatment regimen after their first attack to prevent second events -- called secondary prevention," said Hanieh Mohammadi from the Karolinska Institute in Sweden.

"Secondary prevention works through reducing risk factors associated with heart attack, and stroke such as high blood sugar, lipids and blood pressure," Mohammadi said in a statement.

The study, published in the European Journal of Preventive Cardiology, followed over 22,000 patients in Sweden after their first heart attack.

The researchers investigated the relation between abdominal obesity -- measured by waist circumference -- and the risk for repeat cardiovascular disease events.

They specifically looked at events caused by clogged arteries, such as fatal and non-fatal heart attack, and stroke. Patients were followed for a median of 3.8 years.

Most patients -- 78 per cent of men and 90 per cent of women -- had abdominal obesity, with waist circumference of 94 centimetres (cm) or above for men, and 80 cm or above for women.

Increasing abdominal obesity was independently associated with fatal and non-fatal heart attacks, and strokes, the researchers said.

This was regardless of other risk factors -- such as smoking, diabetes, hypertension, blood pressure, blood lipids and body mass index (BMI), and secondary prevention treatments.

Waist circumference was a more important marker of recurrent events than overall obesity, the researchers said.

"The reason abdominal obesity is very common in patients with a first heart attack is that it is closely linked with conditions that accelerate the clogging of arteries through atherosclerosis," Mohammadi said.

These conditions include increased blood pressure, high blood sugar and insulin resistance (diabetes) as well as raised blood lipid levels," she said.