Influence of doxycycline on clinical and angiographic outcome following percutaneous coronary intervention

Infection with Chlamydia pneumoniae may be involved in atherosclerosis. Neointima proliferation after percutaneous coronary intervention (PCI) could be aggravated by proinflammatory action of chronic vascular chlamydial infection. We investigated the influence of doxycycline therapy on restenosis rate and adverse clinical event rates after PCI.

We followed 1,019 consecutive patients in a single center nonrandomized observational study. During a 3-month period, all patients having PCI (n = 541; treatment group) received oral doxycycline 100 mg/day for 50 days starting from the day of the procedure. A control group (n = 478) consisted of consecutive post-PCI patients recruited from immediately preceding (n = 250) and ensuing periods. Event rates were gained by questionnaires after 259 +/- 57 days. Restenosis rate was derived from the routine angiographic restudies after 172 +/- 15 days.

No significant differences between treatment and control group were found in adverse clinical event rates (myocardial infarction: 0.7% vs 1.3%; repeat-PCI: 24.0% vs 20.9%; coronary bypass grafting: 5% vs 3.9%; overall death after 6 months: 3.5% vs 2.1%) and overall restenosis rate (21.6% vs 23.4%). A subgroup analysis of nondiabetic male smokers revealed a lower restenosis rate in the treatment group (10.9% vs 30.9%; P = 0.0195).

Doxycycline therapy for 50 days following PCI does not appear to have a substantial influence on the clinical and angiographic outcome in unselected patients. The observed reduction in restenosis rate among nondiabetic male smokers defines a new hypothesis that should stimulate further investigations.