A study in mice by Ritzman (et al, 2010) found that those animals most susceptible to Lyme disease arthritis and carditis had more pronounced upregulation of the expression of a particular chemokine reception (CXCR2) at the site of infection. The CXCR2 ligand KC (CXCL1) plays a role in recruiting neutrophils (immune system cells) into the tissues of the body and the resulting inflammation. Those mice lacking this particular chemokine receptor (it having been deleted) did not experience the same degree of Lyme carditis or arthritis but clearance of Borrelia spirochaetes was the same in both sets of mice.
This type of research may allow for the experimental induction of Lyme carditis in animals in order to study the pathology at work and develop possible treatments. It may also provide an indication as to which patients may be more susceptible to the symptoms of Lyme arthritis and Lyme disease heart complications such atrioventricular block in order to provide better monitoring and disease management.
Lyme Disease in Children – Heart Symptoms
Lyme disease symptoms in children may also include Lyme carditis, with a review of cases by Costello (et al, 2009) finding a 16% incidence of the condition amongst more than 200 children with Lyme disease. Of those children affected, 42% had advanced heart block, with 27% suffering complete heart block. None of the children required a permanent pacemaker however, and the median recovery time for a healthy sinus rhythm in the children was three days, although some patients recovered more quickly (1 day) and others took a week for sinus rhythm restoration. The researchers also found that carditis was more likely to occur in children over ten years of age, those children with arthralgias, and those with cardiopulmonary symptoms.
Lyme disease heart complications may only occur in a small percentage of those suffering from Lyme disease but overlooking these symptoms can be fatal. Men are thought to suffer from heart complications associated with Lyme disease at three times the rate as women but, as men are more likely to have cardiovascular issues, this may further confuse diagnosis (van der Linde, 1991). Lyme carditis appears to be fully reversible for the majority of patients, with no need for permanent pacemakers. Where the condition goes undiagnosed, or is misdiagnosed as a chronic heart condition rather than a short-lived Lyme disease heart complication there is a risk of the inappropriate fitting of a permanent pacemaker and a failure to address systemic infection.
Steere, A.C., Batsford, W.P., et al, (1980). Lyme Carditis: Cardiac Abnormalities of Lyme Disease, Annals of Internal Medicine, 93, 1, pp.8-16.
Ritzman, A.M., Hughes-Hanks, J.M., Blaho, V.A., Wax, L.E., Mitchell, W.J., Brown, C.R., (2010). The Chemokine Receptor CXCR2 Ligand KC (CXCL1) Mediates Neutrophil Recruitment and Is Critical for Development of Experimental Lyme Arthritis and Carditis, Infection and Immunity, 78, 11, pp.4593-4600.
Lo, R., Menzies, D.J., Archer, H., Cohen, T.J., 2003, Complete heart block due to lyme carditis. J Invasive Cardiol., 15, 6, pp.367-9.
McAlister, H.F., Klementowicz, P.T., Andrews, C., Fisher, J.D., Feld, M., Furman, S., 1989, Lyme Carditis: An Important Cause of Reversible Heart Block, Annals of Internal Medicine, 110, 5, pp.339-345.
van der Linde MR, 1991, Lyme carditis: clinical characteristics of 105 cases. Scandinavian Journal of Infectious Diseases. Supplement, 77, pp.81-4.
Costello, J.M., Alexander, M.E., Greco, K.M., Perez-Atayde, A.R., Laussen, P.C., Lyme Carditis in Children: Presentation, Predictive Factors, and Clinical Course, Paediatrics, Vol. 123 No. 5 May 1, 2009, pp. e835 -e841.