Date Published: 16 March 2009
International study reveals new findings on serious disease
A definitive international study led by New Zealand clinicians and scientists has shed new light on the potentially fatal disease, infective endocarditis (IE).
Endocarditis is an infection of a heart valve and has an 18% in-hospital mortality rate; a rate that has not changed in the last 25 years. The one-year mortality rate is even worse, approaching 40%. It also has other serious health impacts such as stroke, blood clots, heart failure and other ongoing complications.
Lead researcher, Professor David Murdoch from the University of Otago Christchurch, says this is the first major international study which has examined the presentation, causes and outcome of infective endocarditis. It is the largest ever study of IE, with 2781 patients from 58 hospitals in 25 countries, and may never be repeated.
"What this study does is that it enables us to be much more definitive about the contemporary causes of this serious disease and how to better treat it and reduce the stubbornly high mortality rate," he says.
"In particular it has shown that infective endocarditis is often an acute and serious illness that needs to be diagnosed and treated quickly with antibiotics and often surgery in order to save lives. Today it's probably more of an acute disease than it used to be."
About 300 people are hospitalised in New Zealand every year with infective endocarditis and the study shows that internationally 50% undergo heart valve replacement surgery.
The study reveals that the bacterium Staphylococcus aureus is the most common cause of IE in much of the world, and that IE commonly follows degeneration of the heart valves with aging. This is in contrast to earlier studies that linked it to heart valve damage following rheumatic fever in younger age groups.
The study concludes that some of the classical clinical features of IE that are taught to all medical students now only occur in a minority of patients. Professor Murdoch says this means that clinicians will have to reassess how they diagnose and treat this acute disease following this study, and that medical guidelines and education will have to be adjusted.
One of the more interesting findings is that 25% of patients with IE contracted the bacterial infection following health care, or after invasive medical care, particularly in the USA.
This is relevant in New Zealand with an ageing population which is likely to be exposed to more hospital care. Other factors linking IE with in-hospital death are increasing age, pulmonary oedema and other heart valve complications. An important finding is that early surgery is associated with a decreased risk of dying.
The research is published in the Archives of Internal Medicine. The New Zealand arm of the study involved hospitals in Auckland, Wellington and Christchurch.