Ambulatory ECG Monitoring (Holter recording) is one of the mostly used cardiac examinations to detect different abnormalities like: arrhythmias, silent or symptomatic ischemia, and abnormal variations in heart rate (abnormal heart rate variability). This work evaluates and discusses the prevalence and prognostic value of each abnormality and the combination of these abnormalities. The focus is on middle-aged and elderly subjects with no apparent heart disease in whom these abnormalities may be the first signs of cardiovascular disease or susceptibility.