Suspicious Index in Lyme Carditis (SILC): Systematic Review and Proposed New Risk Score.

BACKGROUND: Lyme carditis (LC), an early manifestation of Lyme disease that most commonly presents as high-degree atrioventricular block (AVB), usually resolves with antibiotic treatment. When LC is not identified as the cause of AVB, a permanent pacemaker may be inappropriately implanted in a reversible cardiac conduction disorder.

HYPOTHESIS: The likelihood that a patient's high-degree AVB is caused by LC can be evaluated by clinical characteristics incorporated into a risk stratification tool.

METHODS: A systematic review of all published cases of LC with high-degree AVB, and five cases from the authors' experience, was conducted. The results informed the development of a new risk stratification tool, the Suspicious Index in Lyme Carditis (SILC) score. The SILC score was then applied to each case included in the review.

RESULTS: Of the 88 cases included, 51 (58%) were high-risk, 31 (35.2%) intermediate-risk, and 6 (6.8%) low-risk for LC according to the SILC score (sensitivity 93.2%). For the subset of 32 cases that reported on all SILC variables, 24 (75%) cases were classified as high-risk, 8 (25%) intermediate-risk, and 0 low-risk (sensitivity 100%). Specificity could not be assessed (no control group). Notably, 6 of the 11 patients who received permanent pacemakers had reversal of AVB with antibiotic treatment.

CONCLUSION: The SILC risk score and COSTAR mnemonic (Constitutional symptoms; Outdoor activity; Sex = male; Tick bite; Age < 50; Rash = erythema migrans) may help identify LC in patients presenting with high-degree AVB, and ultimately, minimize the implantation of unnecessary permanent pacemakers.