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Background: Changes in autonomic function have been described in patients with heart failure. However, the relationship of indices of autonomic function with echo markers of systolic and diastolic function is unknown. This study aimed to determine the relationship between heart rate variability (HRV), a marker of autonomic function, and echocardiographic determinants of systolic and diastolic function.Methods: One hundred and fifteen patients (mean age 68 ± 9 years) had full cross sectional imaging with transthoracic echocardiography. Autonomic data were obtained non invasively from beat-to-beat analysis of heart rate using a plethysmographic device, the Task Force® Monitor. From this we determined total power spectral density (PSD) as a marker of HRV.Results: Twenty nine patients had normal left ventricular (LV) systolic function. The numbers with mild, moderate and severely impaired LV systolic function were 32, 29, 25 respectively. Patients with impaired LV systolic function had a significantly reduced PSD (p = < 0.001, for mild, moderate, and severely impaired LV systolic function respectively) compared to normal patients. PSD positively correlated with declining LV ejection fraction (r = 0.89, p = < 0.001) and declining peak systolic velocity (r = 0.72, p = < 0.001). There was a negative correlation between PSD and left atrial size (r = -0.76, p = < 0.001), mitral E/Ea (r = -0.84, p = < 0.001), pulmonary atrial reversal velocity (r = -0.43, p = 0.002), LV end systolic diameter (r = -0.39, p = < 0.04), and LV end diastolic diameter (r = -0.36, p = 0.05). There was no correlation with LV wall thickness or LV mass index. With stepwise multiple regression analysis, peak systolic velocity (β = -7.4 ± 3.9, p < 0.05) and mitral E/Ea (β = 12.2 ± 4.2, p < 0.001) were independently associated with PSD.Conclusion: HRV significantly attenuates as LV systolic and diastolic function declines. Long axis LV systolic function and mitral E/Ea are independently associated with PSD.