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Infective endocarditis is "not uncommon" after surgical mitral and aortic valve replacement, as determined by a Danish registry analysis.

The cumulative risk of infective endocarditis over 10 years was 5.2% after both mitral and aortic valve replacement, according to Lauge Østergaard, MB, of Rigshospitalet in Copenhagen, and colleagues.

Their study took records from the Danish National Patient Registry of patients who underwent a surgical left-sided heart valve replacement from 1996 to 2015, they wrote in the .

The cohort t0taled 18,041 individuals, the bulk of whom had undergone an aortic valve replacement. Follow-up lasted a median of 5.6 years.

On multivariable analysis, baseline characteristics associated with infective endocarditis after mitral valve replacement were:

• Male sex: HR 1.68 (95% CI 1.06-2.68)
• Bioprosthetic valve: HR 1.91 (95% CI 1.08-3.37)
• Heart failure: HR 1.69 (95% CI 1.06-2.68)

Those for aortic valve replacement were:

• Male sex: HR 1.59 (95% CI 1.33-1.89)
• Bioprosthetic valve: HR 1.70 (95% CI 1.35-2.15)
• Cardiac implantable electronic device: HR 1.57 (95% CI 1.19-2.06)
• Diabetes: HR 1.45 (95% CI 1.15-1.84)
• Atrial fibrillation: HR 1.34 (95% CI 1.13-1.59)

Østergaard's group cautioned against the finding that bioprosthetic valves were tied to infective endocarditis after both mitral and aortic procedures. "Even though propensity score matching have been carried out, the clinician's choice of prosthesis is made upon a patient identification that can be difficult to assess through registries, and our results may be due to case mix rather than valve specific differences," they said.

"The finding that bioprostheses are associated with a higher risk of prosthetic valve endocarditis is subject to major confounding by indication. Biological prostheses are not only used in those who are older and comorbid, but also in those who are more frail and clinically unsuitable for anticoagulation. Despite rigorous propensity matching, this is difficult to adjust for and there is a likelihood of residual confounding," agreed Thomas Cahill, MBBS, of Oxford University Hospitals in England, and Bernard Prendergast, DM, of St. Thomas' Hospital in London, in an .

Besides its nonrandomized nature, the study relied on a registry that does not differentiate between left-side, right-sided, or prosthesis infective endocarditis, Østergaard's group acknowledged.

Cahill and Prendergast added that "there was no differentiation between early and late prosthetic valve endocarditis, which might have revealed specific risk factors in the post-operative phase compared with late follow-up.

Individuals with a prosthetic valve replacement are the largest high-risk group for infective endocarditis and, given the burden of valvular heart disease, this number is set to skyrocket in the future, the editorialists commented, suggesting that to curb this condition will require efforts from both patients and clinicians.

"Patient knowledge of infective endocarditis is generally poor, and a specific educational programme after valve replacement with yearly recall, follow-up Emails, and dental review might improve awareness, oral hygiene, and earlier diagnosis," according to Cahill and Prendergast. "For clinicians, a particular focus on the group of elderly male patients with bioprosthetic valves is warranted, as they appear to be at particularly elevated risk, although the mechanism remains unclear."