Discussion
We present original data on IE, with long-term outcome measures, in a group of islands in the Pacific. The main underlying heart condition was rheumatic heart disease. The majority of patients presented with complicated IE. Barely half the surgical candidates were deemed fit for surgery. Access to emergent or urgent surgery is limited in this remote area. Mortality was extremely high (>40%) at long-term follow-up ∼2.5 years.
Clinical characteristics
Patterns of IE in New Caledonia, a high-income country, resemble those of many emerging market-economies with an on-going epidemiological transition.18 ,19 Although we focused our study on adults, patients were relatively young (mean age ∼53 years). Our patients are younger by 10 years when compared to a recent survey conducted in France.2 In the USA, patients with IE are increasingly older; 36% of patients are over 69 years of age.3
As in Europe and North America, the most frequent pathogen in IE was S. aureus.1–3 However, S. viridans remains the second leading pathogen in our series (15.7%), whereas it has almost disappeared in the USA.3 ,20 In our study, the microbiological profile reflects the emergence of healthcare-related bacteraemia and the persistence of poor dental health.18 Healthcare-associated IE was, however, present in a minority of our patients (13.7%). This finding differs from the epidemiology of IE in Western countries, where healthcare-associated IE accounts for over a third of cases.21
Rheumatic heart disease remains a major predisposing factor of IE, the condition being highly prevalent among Oceanic populations in New Caledonia.12 Although rheumatic heart disease still prevails in most of the developing countries and among indigenous populations,22 the importance of rheumatic heart disease as an underlying condition for IE is highly variable across other tropical or subtropical countries. The disease remains the main predisposing factor for IE in countries where a large proportion of the population lives in poverty,19 whereas its significance has diminished elsewhere over the past decade.18
Investigations, complications, treatment
Blood cultures and echocardiography were performed in all patients. However, advanced techniques for the diagnosis of blood culture negative endocarditis were not systematically performed.4 As in other series, approximately one-third of patients presented with heart failure and/or severe valve regurgitation,2 with neurological complications collected in almost half the cases,23 and a significant proportion (∼50%) being admitted to the intensive care unit.24
Management of IE is challenging,25 especially in non-surgical centres. Access to surgery, in our study, was relatively limited since barely 55% of patients with a theoretical indication for surgery were deemed fit for intervention.17 Of note, no patient underwent emergency surgery and only a minority of surgical candidates (3.9%) had surgery within 7 days after admission. Although comorbidities and neurological complications accounted for main reported reasons for denying surgery, no contraindications were identified in the remaining 7 of 18 surgical candidates not operated on. Remoteness may have contributed to favour medical treatment in patients with theoretical indications other than heart failure. Our study highlights the difficulties in applying current guidelines in remote locations,5 which may be even greater in poorly resourced settings.26 Of note, underuse of heart valve surgery is not restricted to IE or remote locations.27
Outcomes
Although the crude in-hospital case fatality rates observed are apparently similar to other reports, our patients were markedly younger.2 ,28 Early mortality was mostly IE related due to cardiogenic shock and/or neurological complications. Mortality almost doubled at long-term follow-up, reaching 42.9%. These findings highlight the severity of the condition and the need for longer follow-up periods to estimate the true impact of the disease.29 Factors associated with in-hospital and long-term mortality varied, as previously described by Bannay et al.29 Previously described factors, such as older age,30 ,31 comorbidities,32 microorganisms (S. aureus infection being of poor prognosis)31 ,33 and use of cardiac surgery,6 were associated with long-term outcomes in our study. The mortality rate is extremely high considering the young and relatively comorbid-free population affected by IE in our series. In addition, the rate of complications was similar to what has been described elsewhere.1 ,2 ,24 Reportedly, only patients admitted to intensive care experience higher case fatality rates after a similar follow-up period.34 Several hypotheses can be raised to explain our findings. Rapid diagnosis is key to early antibiotic treatment that impacts on the advent of complications, especially neurological emboli.35 Time from onset of symptoms to hospital admission varied, and there may still be room for improvement in the rapid diagnosis of IE through early referral from primary care centres. The higher than expected in-hospital mortality in our study may also be potentially and partly explained by the difficulties to access urgent cardiac surgery (ie, within the first 7 days), especially for those in cardiogenic shock.
Almost 1 of 10 patients experienced a relapse or reinfection during the follow-up period. This finding is a novelty in the field, seldom reported in the literature.10
In addition to high case fatality rates, only a third of survivors resumed their normal activities, albeit the majority did not experience cardiovascular symptoms. Of note, the mean unemployment rate in New Caledonia is 6%.11 Our results suggest that IE, a curable disease, may lead to long-term individual loss of income.
Ways of reducing the burden and mortality of IE
Prevention of rheumatic heart disease may diminish the incidence of IE in our population.22 Our findings should also promote periodontal health. Prophylaxis before oral procedures should be addressed in countries where the incidence of streptococcal IE remains high.36 Urgent referral to the hospital with echocardiography facilities may reduce the delay between the onset of symptoms and diagnosis, thereby preventing the advent of complications. Access to urgent heart surgery should be facilitated to prevent complications and decrease early mortality in patients with IE in countries with no on site surgical facilities.
Strengths and Limitations
This is, to the best of our knowledge, the first report on IE from a tropical Pacific Island. Our study suffers, however, from several limitations. It lacked power to assess factors associated with long-term outcomes given the sample size precluding multivariate analysis. Survivor selection bias prevents from drawing conclusions from the higher fatality rates among patients treated medically. Our results should foster further prospective studies to confirm our findings, find ways to increase access to surgery, and guide prevention programmes.
Conclusion
In New Caledonia, a high-income country located in the Pacific, IE still remains a disease of relatively young patients with underlying rheumatic heart disease. Almost half the surgical candidates are not deemed fit for cardiac surgery, and long-term mortality remains dramatically high. Ways to decrease the burden of IE and improve its management in remote locations need further assessment.