a technique is provided for detecting episodes of cardiac ischemia based on an examination of the total energy of t - waves . since cardiac ischemia is often a precursor to acute myocardial infarction or ventricular fibrillation , the technique thereby provides a method for predicting the possible onset of ami or vf . briefly , the technique integrates internal electrical cardiac signals occurring during t - waves and then compares the result against a running average . if the result exceeds the average by some predetermined amount , ischemia is thereby detected and a warning signal is provided to the patient . the maximum slope of the t - wave is also exploited . techniques are also set forth herein for reliably detecting t - waves , which help prevent p - waves from being misinterpreted as t - waves on unipolar sensing channels . the t - wave detection technique may be used in conjunction with ischemia detection or for other purposes .