Diagnostic criteria and problems in infective endocarditis

Few diseases present greater difficulties in the way of diagnosis than malignant endocarditis, difficulties which in many cases are practically insurmountable. It is no disparagement to the many skilled physicians who have put their cases upon record to say that, in fully one-half the diagnosis was made post mortem.— William Osler 1885 Osler’s portentous words are as relevant now as when originally published. Despite improved preventive strategies, rational antibiotic prescribing, advances in imaging, and increasing use of early life saving cardiac surgery, the incidence of infective endocarditis remains high at 1.7–6.2 per 100 000 person years in the USA and Europe, with a one year mortality approaching 40%.1 The classical patient with infective endocarditis described in textbooks no longer represents the majority of cases in practice. The emergence of staphylococcal infection, often associated with indwelling devices, co-existent medical conditions and resistant to conventional antibiotic regimes, a variety of other atypical organisms, and the persistent syndrome of culture negative endocarditis make diagnosis and treatment as great a challenge as ever. The original von Reyn diagnostic criteria for infective endocarditis,2 based upon clinical and microbiological features, have now been surpassed by the Duke criteria3 which emphasise the role of echocardiography, the key imaging tool for both diagnosis and assessment of prognosis. Many studies have now demonstrated the superiority of the Duke criteria and a recent scientific statement of the American Heart Association concluded that they should be adopted as the primary diagnostic schema in the clinical evaluation of patients in whom infective endocarditis is suspected.4 Nevertheless, clear deficiencies remain. Thus, in one series5 of 93 patients with pathologically confirmed infective endocarditis (affecting a native valve in 63 and a prosthetic valve in the remainder), 22 were misclassified as “possible” cases using the Duke criteria, yielding a sensitivity …