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Background & Objectives: Hereditary haemochromatosis (HH) may be associated with an infiltrative cardiomyopathy and atrial arrhythmias. Doppler echocardiogram derived left atrial parameters including the left atrial ejection force (LAEF) were used to evaluate left atrial (LA) systolic function. The relationship between LAEF and left ventricular (LV) function was investigated.Methods: Fourteen subjects with newly diagnosed untreated HH and 14 age and gender matched control subjects were recruited and underwent echocardiography with comprehensive systolic and diastolic functional evaluation. Left and right ventricular (LV & RV) myocardial strain (MS) was measured. LV and right ventricular (RV) myocardial performance index (MPI) and the transit time of the left atrial pressure wave A-Ar interval were measured. Left atrial ejection force, defined as 1/3 X Mitral Valve Area (MVA) X A2 (where A is the atrial flow velocity of transmitral Doppler).Results: In subjects with HH (Mean baseline Ferritin and Brain Natriuretic Peptide levels were 697.46±119.36 ng/ml & 56.08±13.68 pg/ml respectively), LAEF was lower (136.27±7.4%) than control (202.9±7.4%, P<0.001). The peak isovolumic acceleration recorded at the free wall of LV & RV was lower in the HH compared to controls (P>0.0001). The LV & RV MS, A-Ar, and tissue Doppler (TD) E' were reduced in HH subjects compared to controls (P>0.001). Moreover, the MPI of LV and RV was greater in HH subjects than controls (P<0.01). Significant correlation was observed between LAEF and A-Ar, TD E', TD Sm systolic velocity, and LV MPI (r=0.92, 0.89, 0.71, -0.71 & P<0.0001 respectively). In a stepwise regression model, TD E' (P=0.006), emerged as the only independent determinant of LAEF (R2=0.86, P<0.0001).Conclusion: Left atrial ejection force is a novel non-invasive parameter of LA systolic function and is markedly reduced in newly diagnosed heamachromatosis. The additive clinical value of assessing LA systolic function needs further study.