1. An instrument for continuously monitoring the condition of a patient who has a cardiovascular disease, said instrument comprising: an electrocardiograph which during use is connected to the patient; a waveform analyzer which analyzes a current segment of an ECG waveform for the patient from the electrocardiograph; a computer receiving output from the waveform analyzer, said computer programmed to complete a monitoring cycle in which the computer uses the output from the waveform analyzer to compute a probability of a life threatening cardiac condition based upon the current segment of the patient's ECG waveform; and a control module causing said computer to periodically repeat the monitoring cycle and for each repetition of said monitoring cycle to compute a change-of-condition measure, wherein said change-of-condition measure is calculated by subtracting a computed probability for a previous monitoring cycle from the computed probability for the current monitoring cycle, said computer further programmed to compare during each monitoring cycle the computed change-of-condition measure for that monitoring cycle to a threshold value and if in excess of said threshold value to generate an alarm notification.