An implantable medical device for use in assessment of one or more conditions of a patient comprising: sensing apparatus configured to monitor physiological parameters of the patient, wherein the physiological parameters comprise the patient's posture and ejection time, wherein the patient's ejection time comprises at least one of the patient's left ventricular ejection time and right ventricular ejection time; a sensing module coupled to the sensing apparatus and configured to receive the monitored physiological parameters; and a control module coupled to the sensing module and configured to: detect a change in the patient's posture between a lying position and an upright position using the monitored physiological parameters, determine a posture-induced change to the patient's ejection time using the monitored physiological parameters, wherein the posture-induced change to the patient's ejection time comprises a difference between the patient's ejection time before the detected change in the patient's posture and the patient's ejection time after the detected change in the patient's posture, store the difference between the patient's ejection time before the detected change in the patient's posture and the patient's ejection time after the detected change in the patient's posture, and analyze the difference between the patient's ejection time before the detected change in the patient's posture and the patient's ejection time after the detected change in the patient's posture to provide an assessment of one or more conditions of the patient, characterized in that the one or more conditions of the patient comprise fluid overload. sensing apparatus configured to monitor physiological parameters of the patient, wherein the physiological parameters comprise the patient's posture and ejection time, wherein the patient's ejection time comprises at least one of the patient's left ventricular ejection time and right ventricular ejection time; a sensing module coupled to the sensing apparatus and configured to receive the monitored physiological parameters; and a control module coupled to the sensing module and configured to: detect a change in the patient's posture between a lying position and an upright position using the monitored physiological parameters, determine a posture-induced change to the patient's ejection time using the monitored physiological parameters, wherein the posture-induced change to the patient's ejection time comprises a difference between the patient's ejection time before the detected change in the patient's posture and the patient's ejection time after the detected change in the patient's posture, store the difference between the patient's ejection time before the detected change in the patient's posture and the patient's ejection time after the detected change in the patient's posture, and analyze the difference between the patient's ejection time before the detected change in the patient's posture and the patient's ejection time after the detected change in the patient's posture to provide an assessment of one or more conditions of the patient, characterized in that the one or more conditions of the patient comprise fluid overload. detect a change in the patient's posture between a lying position and an upright position using the monitored physiological parameters, determine a posture-induced change to the patient's ejection time using the monitored physiological parameters, wherein the posture-induced change to the patient's ejection time comprises a difference between the patient's ejection time before the detected change in the patient's posture and the patient's ejection time after the detected change in the patient's posture, store the difference between the patient's ejection time before the detected change in the patient's posture and the patient's ejection time after the detected change in the patient's posture, and analyze the difference between the patient's ejection time before the detected change in the patient's posture and the patient's ejection time after the detected change in the patient's posture to provide an assessment of one or more conditions of the patient, characterized in that the one or more conditions of the patient comprise fluid overload.