Method for assessing a mortality risk of a cardiac patient based on respiratory sinus arrhythmia, said method comprising the following steps: a. Step A: Computing the mean respiratory sinus arrhythmia during inhalation and/or exhalation for a plurality of breathing cycles of said patient. b. Step B: Assessing the mortality risk of said patient based on said computation, said Step A further comprising at least the following sub-step: Step A4: Obtaining a time series representing the respiratory activity or chest movement of said patient by high-pass filtering of electrocardiogram-recordings of said patient, wherein the time series is preferably obtained in digital form and/or covers a period of time of at least 30 minutes. said Step B further comprising the following sub-steps: a'. Step B1: Allocating said patient to a low-mortality-risk group in case the mean respiratory sinus arrhythmia calculated for said patient indicates that the heartbeat intervals are decreasing during inhalation and/or increasing during exhalation. b'. Step B2: Allocating said patient to a high-mortality-risk group in case the mean respiratory sinus arrhythmia calculated for said patient indicates that the heartbeat intervals are increasing during inhalation and/or decreasing during exhalation. c'. Step B3: Outputting the result of risk stratification based on the results of Step B1 and/or Step B2. a. Step A: Computing the mean respiratory sinus arrhythmia during inhalation and/or exhalation for a plurality of breathing cycles of said patient. b. Step B: Assessing the mortality risk of said patient based on said computation, said Step A further comprising at least the following sub-step: Step A4: Obtaining a time series representing the respiratory activity or chest movement of said patient by high-pass filtering of electrocardiogram-recordings of said patient, wherein the time series is preferably obtained in digital form and/or covers a period of time of at least 30 minutes. said Step B further comprising the following sub-steps: a'. Step B1: Allocating said patient to a low-mortality-risk group in case the mean respiratory sinus arrhythmia calculated for said patient indicates that the heartbeat intervals are decreasing during inhalation and/or increasing during exhalation. b'. Step B2: Allocating said patient to a high-mortality-risk group in case the mean respiratory sinus arrhythmia calculated for said patient indicates that the heartbeat intervals are increasing during inhalation and/or decreasing during exhalation. c'. Step B3: Outputting the result of risk stratification based on the results of Step B1 and/or Step B2. said Step A further comprising at least the following sub-step: Step A4: Obtaining a time series representing the respiratory activity or chest movement of said patient by high-pass filtering of electrocardiogram-recordings of said patient, wherein the time series is preferably obtained in digital form and/or covers a period of time of at least 30 minutes. said Step B further comprising the following sub-steps: a'. Step B1: Allocating said patient to a low-mortality-risk group in case the mean respiratory sinus arrhythmia calculated for said patient indicates that the heartbeat intervals are decreasing during inhalation and/or increasing during exhalation. b'. Step B2: Allocating said patient to a high-mortality-risk group in case the mean respiratory sinus arrhythmia calculated for said patient indicates that the heartbeat intervals are increasing during inhalation and/or decreasing during exhalation. c'. Step B3: Outputting the result of risk stratification based on the results of Step B1 and/or Step B2. a'. Step B1: Allocating said patient to a low-mortality-risk group in case the mean respiratory sinus arrhythmia calculated for said patient indicates that the heartbeat intervals are decreasing during inhalation and/or increasing during exhalation. b'. Step B2: Allocating said patient to a high-mortality-risk group in case the mean respiratory sinus arrhythmia calculated for said patient indicates that the heartbeat intervals are increasing during inhalation and/or decreasing during exhalation. c'. Step B3: Outputting the result of risk stratification based on the results of Step B1 and/or Step B2.