This means that what wasn’t emergency surgery may well be the cause of emergency surgery.

Many of the risks are due to specific conditions or poor health in general. Previous or current heart disease, diabetes and kidney disorders all increase the risk of heart complications around the time of surgery (see box below) (Mt Sinai J Med, 2005; 72: 185-92).

Other factors contributing to cardiovascular surgical complications and mortality include high blood pressure (hypertension), poor physical fitness and older age. Further problems pertain to the surgery itself - for example, complications are more likely to stem from procedures requiring blood transfusion or a prolonged stay in hospital such as vascular surgery and other high-risk surgery (Br J Nurs, 2005; 14: 718-24).

Coronary artery disease is a major risk factor for a heart attack around surgery. In a study of 1487 men, aged over 40 and undergoing major elective operations, those with heart disease had a 4.1 per cent incidence of heart attack, compared with just 0.8 per cent for those with peripheral vascular disease, but no heart disease. Patients with no atherosclerosis risk factors and no clinical vascular disease had no incidence - and no cardiac deaths - at all (Ann Intern Med, 1993; 118: 504-10).

Long-term heart complications When elderly patients were followed up for 10 years after elective surgery, heart attack and death were common complications, occurring on average in about one out of every 36 cases of hospitalisation (BMJ, 2005; 331: 932).

But ‘long-term cardiac complications’ may be a misleading phrase. It appears that at-risk patients are most likely to die within six months to two years post-op. Of 1622 patients with cardiac risk factors who had elective surgery, 11 per cent died within a year. The majority of heart-related deaths occurred within six months, and those with angina had a nearly 60 per cent greater risk of death (Br J Nurs, 2005; 14: 718-24).

Patients who don’t die require more hospitalisation. A study of 444 patients with a high risk for coronary artery disease (or the disease itself) who had elective surgery found that 11 per cent had major cardiovascular complications during a follow-up of nearly two years. Of these, 24 died of a heart-related cause, 11 had a non-fatal heart attack, six had progressive angina that required further surgery and a further six were hospitalised because of new unstable angina.

Patients lucky enough to survive a heart attack while in hospital had a 28-fold increase in the rate of further cardiac incidents within six months of surgery, a 15-fold increase within a year and a 14-fold increase within two years (J Am Med Assoc, 1992; 268: 233-9).

However, patients facing the greatest risk include those with acute circulatory problems around the time of surgery. In the study mentioned above, nearly three-quarters of patients who developed long-term heart complications had preexisting circulatory problems. However, congestive heart failure or tachycardia (rapid heartbeat) during hospitalisation did not pose the same risk (J Am Med Assoc, 1992; 268: 233-9).

The hypertension hurdle Hypertension is the most common of the cardiovascular diseases, and is the most frequent medical reason for postponing elective surgery. It affects more than 60 million people in the US alone, and contributes to nearly 250,000 deaths a year. But it’s still not certain whether deferring surgery due to high preoperative blood pressure will reduce the risk of developing heart problems around the time of surgery.