A system improves detection and diagnosis of blood pressure based cardiac function and tissue activities by analyzing and characterizing cardiac blood pressure signals (including non-invasive and invasive blood pressure, discrete values and continuous waveforms) using pressure signal variation and variability calculation and evaluation. The system combines blood pressure analysis with multi clinical related factors and parameters to detect and quantify cardiac health status and arrhythmia severity. The system determines an accurate time, location and severity of cardiac pathology and events by calculating blood pressure variability and statistical variation. The accurately and reliably identifies cardiac disorders, differentiates cardiac arrhythmias, characterizes pathological severity, predicts the life-threatening events, and supports evaluation of drug delivery effects.