Tricky ticks: the importance of Lyme carditis recognition

Hofhuis et al. performed a broad survey on physicianreported incidence of different Lyme disease associated manifestations [5], of which the results on Lyme carditis are presented in this issue of the Netherlands Heart Journal [6]. The authors leveraged the fact that every person in the Netherlands is registered with only one general practitioner (GP). In daily practice, a GP consultation is required for a patient to be referred to a medical specialist in the hospital and the specialist will report back to the GP. Taking this into account, Hofhuis et al. first sent a retrospective questionnaire about Lyme borreliosis diagnoses in the years 2009 and 2010, including clinical diagnoses of Lyme carditis, to all GPs in the Netherlands. The response rate to the question on Lyme carditis was 33 % among GPs, representing 46 % of the Dutch population, and yielded 39 reported cases of Lyme carditis. This accounts for 0.2 % of all GP-reported Lyme borreliosis related diagnoses [5]. Since the diagnosis of both Lyme borreliosis and Lyme carditis can be rather complex, the next step of the study consisted of a systematic review of the medical records of the reported Lyme carditis cases. Not all GPs, however, were able to cooperate with this step and ultimately only 11 medical records were available for review. Of these, 2 records were mistakenly marked as Lyme carditis by the GPs and another single record was reported twice by 2 GPs working in partnership. Finally, the diagnoses of the 8 remaining cases were evaluated by excluding other possible causes for the cardiac symptoms and by categorisation into various degrees of likelihood of Lyme carditis, based on self-designed diagnostic criteria. This way, the authors found that 6 of the reviewed medical records satisfied their criteria for a very likely Lyme carditis diagnosis, 1 satisfied their criteria for a likely Lyme carditis diagnosis and 1 was categorised as not Lyme carditis. Then, taking into account only the very likely and likely diagnoses, the crude Lyme disease, or Lyme borreliosis, is caused by spirochetes of the Borrelia burgdorferi sensu lato species and is the most common tick-borne infectious disease in Europe and North America [1]. A characteristic early presentation of the disease is erythema migrans, an expanding erythematous skin lesion, which typically occurs days to weeks after the tick bite. Without early treatment, the Borrelia spirochete can disseminate leading to infection of other parts of the skin, joints, nervous system and heart. Lyme carditis, which results from direct invasion of the heart by spirochetes, can lead to conduction disturbances and possibly myocarditis and pericarditis [2]. The most frequent clinical manifestation is atrioventricular (AV) block of varying degrees, which can fluctuate and progress rapidly from firstto third-degree block [3]. Third-degree AV block, or complete heart block, is the most severe form, in which AV electrical dissociation leads to a slow ventricular rhythm. If not managed and treated appropriately, this can trigger life-threatening ventricular tachycardia and ventricular fibrillation. Although temporary cardiac pacing may be required in up to a third of Lyme carditis patients, rushing the implantation of a permanent pacemaker is not recommended as treated patients usually show complete recovery [2]. Obviously, it is of great importance to properly diagnose Lyme carditis. This is especially relevant since there is a continuing increase in tick bites and Lyme disease in the Netherlands [4].