The implantable antitachycardia therapy device,17, wherein the threshold detection means includes means for detecting in which of {HEAD ~ a plurality} of {TAIL ~ rate zones} the heart rate lies 
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The implantable antitachycardia therapy device,17 , wherein the threshold detection means includes means for detecting in which of { HEAD ~ a plurality } of { TAIL ~ rate zones } the heart rate lies
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH