Although a relationship between periodontitis and myocardial hypertrophy has been reported, the precise mechanism has not been clarified. The purpose of this study was to investigate the association between periodontal infection and myocardial hypertrophy. Transverse aortic constriction (TAC) was performed. Mice were injected with Aggregatibacter actinomycetemcomitans (A.a.) (0.1 mL of 10(8) CFU/mL) in the infected group and PBS in the control group. Echocardiography, histopathology, and immunohistochemistry were performed. Echocardiography indicated that left ventricular fractional shortening had decreased in the infected group compared to the control group on day 28. Heart to body weight ratio increased in the infected group compared to the control group. Histopathologically, A.a.-infected mice showed markedly enhanced cardiac hypertrophy, fibrosis and arteriosclerosis 4 weeks after TAC operation. Immunohistochemistry revealed that expression of MMP-2 in the interstitial tissue was enhanced in the infected group. These results suggested that the periodontal pathogen caused a deterioration of pressure overload-induced myocardial hypertrophy through MMP activation.