PurposeTo determine whether the midrange ejection fraction (mrEF)is associated with increased risk of deterioration of cardiac function (DCF) after dual chamber permanent pacemaker (PPM) implantation.MethodsWe performed a prospective cohort study of relevance in patients with EF >= 40% and indications for PPMs. Patient characteristics were recorded at baseline and 1day, 1month, 3months, and 6months after PPM implantation with leads placed in the right ventricular apex. These included clinical symptoms, signs, biochemical parameters, BNP, echocardiography and ECG parameters, and pacing-related parameter changes. The patients were followed-up for 6months. Univariate and multivariable Cox regression analyses were performed.ResultsA total of 879 patients were included, aged 35 to 88years (mean age 67.29.6); a total of 81 patients (9.2%) developed DCF after PPM implantation, including LVEF <40% (57 cases) and increased NYHA class (24 cases). Cox models demonstrated that age >= 75years (HR 2.273 [95% CI, 1.541-3.626]), OMI (HR 2.078 [95% CI, 1.275-3.604]), mrEF (HR 2.762 [95% CI, 1.558-4.769]), moderate mitral regurgitation (HR 2.819 [95% CI, 1.604-4.153]), and right ventricular pacing >= 50% (HR 2.311 [95% CI, 1.478-3.937]) were strong predictors for DCF, and NT-proBNP >1000ng/L and paced QRS duration >= 180ms were also the independent predictors of DCF.ConclusionsMrEF was associated with increased risk of deterioration of cardiac function after PPM implantation. Moderate mitral regurgitation and increased NT-proBNP levels are also potential independent predictors for deterioration of cardiac function after PPM implantation.