RESUMEN
BACKGROUND: Septic cardiomyopathy (SCM) with diastolic dysfunction carries a poor prognosis, and the mechanisms underlying the development of diastolic dysfunction remain unclear. Matrix metalloproteinase-8 (MMP-8) is released from neutrophils and degrades collagen I. MMP-8 levels correlate with SCM severity. OBJECTIVES: We scrutinized, for the first time, the direct impact of MMP-8 on cardiac systolic and diastolic functions. METHODS: Isolated rat hearts were perfused with Krebs-Henseleit solution in a Langendorff setup with computer-controlled filling pressures of both ventricles at isovolumetric regime. The end-diastolic pressure (EDP) varied periodically between 3 and 20 mmHg. After baseline recordings, MMP-8 (100 µg/ml) was added to the perfusion. Short-axis views of both ventricles were continuously acquired by echocardiography. RESULTS: MMP-8 perfusion resulted in progressive decline in peak systolic pressures (Psys) in both ventricles, but without significant changes in their end-systolic pressure-area relationships (ESPARs). Counterintuitively, conspicuous leftward shifts of the end-diastolic pressure-area relationships (EDPARs) were observed in both ventricles. The LV end-diastolic area (EDA) decreased by 32.8±5.7%, (p=0.008), at EDP of 10.5±0.4 mmHg, when LV Psys dropped by 20%. The decline of Psys was primarily due to the decrease in EDA and restoring the baseline EDA by increasing EDP recovered 81.33 ± 5.87% of the pressure drops. CONCLUSION: Collagen I generates tensile (eccentric) stress, and its degradation by MMP-8 causes EDPVR leftward shift, resulting in diastolic and systolic dysfunctions. The diastolic dysfunction explains the clinically observed fluid unresponsiveness, while the decrease in EDV diminishes the systolic functions. MMP-8 can explain the development of SCM with diastolic dysfunction.