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The special challenge of left-sided endocarditis
  1. Ann F Bolger
  1. Correspondence to Professor Ann F Bolger, University of California, San Francisco, 1001 Potrero Avenue 5G1, San Francisco, CA 94110, USA; abolger{at}medsfgh.ucsf.edu

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Endocarditis is always bad news. Standard lines of defence include rapid diagnosis, rapid initiation of antibiotic therapy and meticulous vigilance regarding complications. Despite advances in each of these areas, the terrible morbidity of this disease persists. Among our patients with endocarditis, are there those about whom we should worry even more, ones for whom we need to push ourselves, our health systems and colleagues even harder than usual? The answer may be yes.

There is a growing literature that supports early cardiac surgery to improve patient outcomes in high-risk patients with left-sided valve infections.1 2 Factors such as uncontrolled sepsis, paravalvular extension of infection, heart failure and recurrent embolisation have been identified by different groups as predictors of poor outcome during initial hospitalisation or in the first 6 months following discharge. These factors may identify those for whom an aggressive and accelerated treatment plan is appropriate. If a patient is likely to have a complicated course with endocarditis, the benefit of moving to early surgery will be greatest during the earliest days after diagnosis, as the embolic risk falls rapidly over the first 2 weeks of antibiotic therapy.3 High-risk patients should therefore be identified as early in their course as possible, so that if surgery is likely to avoid additional morbidity or mortality, it can be organised expeditiously.

In their paper published in this issue of Heart, Dr Javier López and colleagues4 from four tertiary referral hospitals in Spain propose a prediction model for patients diagnosed with left-sided infectious endocarditis that would help in clinical decision-making within the first 72 h after admission (see page 1138). They found that, in patients with infections of the aortic and/or mitral valves, heart failure resistant to usual diuretic and afterload reduction therapy, staphylococcal infection and paravalvular extension of infection predicted inhospital mortality or urgent surgery, and thereby identified patients likely to receive the greatest benefit from early surgery. They compared the performance of this index in derivation, internal and external patient groups in order to establish its accuracy across institutions with variable patient characteristics, microbiology and willingness to send patients to surgery.

Institutional variability is an extremely important issue in this work, and in the discussion of early surgery overall. Endocarditis is both very rare and very diverse, comprising a spectrum of aetiologies and consequences. Many centres will not have a specific interest or experience in medical and surgical treatment of endocarditis, nor a patient population well matched to published series. The impact of this sort of predictive tool would probably be greatest at such centres, with the greatest opportunities for improvement resulting from better and earlier definition of high-risk endocarditis features, and the promotion of a system strategy that can create an early surgical option if necessary.

Early patient risk stratification relies on the early use of transesophageal imaging (TEE), which is critical to recognising paravalvular infection. In the study by López et al,4 only 73% of patients at the external sites underwent TEE within the first 3 days. A persistent gap in using this familiar and widely available technology may be a hold-over of lessons learned from the early large urban cohorts of endocarditis patients from before 1990.5 Those studies had large numbers of patients who were intravenous drug users (IVDU), and most came from geographical regions (the east coast of the USA, Europe) where the injection drug of choice was powder heroin. Tricuspid valve infections are more often seen in these patients, and their clinical course is often less complicated due to the absence of the risk of embolisation into the systemic vascular bed. This early data bias continues, now years later, to influence some care standards even in areas without similar patient demographics. For example, the expectation that an IVDU patient will probably have tricuspid valve infection, probably will not have systemic embolisation and may be treatable with a shorter course of antibiotics often leads to a resistance to use urgent TEE imaging (‘the tricuspid valve is often seen as well or better from the chest wall, anyway’) and less suspicion for endocarditis-related heart failure or systemic embolisation. In fact, left heart endocarditis associated with illicit IVDU-associated endocarditis is common, especially among users of stimulant drugs such as cocaine or methamphetamine. A retrospective case review from an urban hospital showed that the preponderance of tricuspid endocarditis was seen only in heroin users.6 The demographics of illicit drug use are changing and are regionally variable. Only half of the IVDU patients included in the study by Lopez et al4 were heroin-only users, and 20% were cocaine-only users. More recent and broader patient cohorts have shown that assumptions about preferential right-heart infections and less complicated courses of infective endocarditis in IVDU are neither accurate nor safe, and may delay important imaging and treatment.7 Unlearning these biases in patient care should lead to more rapid and thorough investigation with transesophageal imaging, improving risk stratification in the first days of hospitalisation.

Second, the surgical team at non-referral centres may not be experienced in these cases. Two of the common issues that typically arise when discussing the timing of surgery for actively infected patients have evolved significantly. One such issue is whether it is safe to operate early, before an antibiotic course has been completed. It has been shown that while the length of presurgical antibiotic administration does predict culture-positivity of valve tissues, it does not predict re-infection or poor surgical outcomes.8 While some surgeons describe more friable tissues early in the antibiotic course, others have argued that earlier surgery limits the extent of valvular destruction and infective material that needs to be addressed at operation, preserving more options for repair. Current recommendations for antibiotic administration after prosthetic valve implantation are for 6 weeks of therapy in most patients; the risk of early prosthetic valve infection in such patients is low.9 It is also helpful to remember that, even after medical cure of native valve infections, the majority of patients with left heart endocarditis will eventually require valve surgery. A strategy that delays such surgery at the risk of leaving the patient at risk of embolisation, heart failure, or sudden death may not be in their best interest.

Cerebrovascular embolisation has also been viewed as an impediment to early surgery. Decisions to move to surgery after such events are generally made in concert with neurology or neurosurgery, but increasing data support the theory that early surgery can be performed safely in many instances of non-haemorrhagic emboli.10 Recognition that these ‘impediments’ may not be absolute or even relevant to a given patient can allow those important discussions to start very early in the patient's care.

While current standards of care serve most endocarditis patients well, the sickest of the sick may need more from us. We need to engage our colleagues very early on in considering the need for an expedited route to surgery in hopes of avoiding emboli, heart failure and overwhelming sepsis. Aggressive and early risk stratification and preemptive surgical planning may be one way to move beyond the plateau of clinical outcomes that has accompanied our more familiar ‘wait and see’ care strategies.

References

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Footnotes

  • Linked article 200295.

  • Competing interests None.

  • Provenance and peer review Commissioned; not externally peer reviewed.

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