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A hydraulic calcium phosphate cement having dicalcium phosphate dihydrate (DCPD) as end-product of the setting reaction was implanted in a cylindrical defect in the diaphysis of sheep for up to 6 months. The composition of the cement was investigated as a function of time. After setting, the cement composition consisted essentially of a mixture of DCPD and β-tricalcium phosphate (β-TCP). In the first few weeks of implantation, the edges of the cement samples became depleted in DCPD, suggesting a selective dissolution of DCPD, possibly due to low pH conditions. The cement resorption at this stage was high. After 8 weeks, the resorption rate slowed down. Simultaneously, a change of the color and density of the cement center was observed. These changes were due to the conversion of DCPD into a poorly crystalline apatite. Precipitation started after 6–8 weeks and progressed rapidly. At 9 weeks, the colored central zone reached its maximal size. The fraction of β-TCP in the cement was constant at all time. Therefore, this study demonstrates that the resorption rate of DCPD cement is more pronounced as long as DCPD is not transformed in vivo. [Copyright &y& Elsevier]

We studied 38 patients (mean age 32 +/- 14 years) with arrhythmogenic right ventricular cardiomyopathy (ARVC) to evaluate the clinical significance of histologic features on endomyocardial biopsy specimens as related to signal-averaged electrocardiography (SAECG), spontaneous ventricular arrhythmias, and hemodynamic features. Fifteen patients presented with ventricular tachycardia or fibrillation (sustained ventricular arrhythmias), 23 with other minor arrhythmias. SAECG variables and right ventricular ejection fraction (RVEF) were statistically correlated with the extent of myocardial fibrosis on biopsy in ARVC. An increased percentage of fibrous tissue (> or = 30%) was a significant univariate predictor of late potentials (p = 0.004) and reduced RVEF (p = 0.02). The 18 patients with late potentials had an increased percentage of fibrous tissue (p = 0.01), a reduced RVEF (p = 0.0004), and a higher risk for sustained ventricular arrhythmias (p = 0.05) than the 20 patients without late potentials. RVEF was the most powerful predictor of late potentials (p = 0.004) at multivariate analysis. Moreover, RVEF < or = 50% was associated with an increased risk for development of sustained ventricular arrhythmias (p = 0.02). A SAECG parameter, namely the root-mean-square voltage of the terminal 40 ms at 25 Hz, was an independent predictive factor for the occurrence of sustained ventricular arrhythmias (p = 0.02). Although fibrous tissue may contribute to delayed myocardial activation in ARVC, a reduced RVEF plays an essential role for spontaneous manifestation of sustained ventricular arrhythmias. [ABSTRACT FROM AUTHOR]