subcutaneous space where the s icd of the present invention will lie 0072 fig1 is a graph that shows an embodiment of the example of a biphasic waveform for use in antitachycardia pacing applications in subcutaneous implantable cardioverter defibrillators u201c s icd u201d in an embodiment of the present invention as shown in fig1 the biphasic waveform is plotted as a function of current versus time in an embodiment the biphasic waveform 1902 comprises a positive portion 1904 a negative portion 1906 and a transition portion 1908 in an embodiment both the positive portion 1904 and the negative portion 1906 are substantially rectangular in shape the positive portion 1904 of the biphasic waveform 1902 comprises an initial positive current 1910 a positive fixed current 1912 and a final positive current 1914 the negative portion 1906 of the biphasic waveform 1902 comprises an initial negative current 1916 a negative fixed current 1918 and a final negative current 1920 in an embodiment the polarities of the biphasic waveform 1902 can be reversed such that the negative portion 1906 precedes the positive portion 1904 in time as shown in fig1 the biphasic waveform 1902 is initially at zero current upon commencement of the anti tachycardia pacing a current of positive polarity is provided and the biphasic waveform 1902 rises to the initial positive current 1910 next the current of the biphasic waveform 1902 remains at a constant level along the positive fixed current 1912 the positive portion 1904 of the biphasic waveform 1902 is then truncated and a negative current is provided the biphasic waveform 1902 then undergoes a relatively short transition portion.