Patent ID: 8280507

Claim:
An implantable cardiac stimulator ( 10 ) including: a. a defibrillation shock generator ( 50 ) in communication with a ventricular defibrillation electrode ( 38 , 40 ), b. a right ventricular sensing unit ( 58 ) configured to receive electric signals of a right ventricle from a right ventricular sensing electrode ( 18 , 20 ), c. at least one of: (1) an atrial electrode line ( 14 ) extending to an atrial sensing electrode ( 22 , 24 ), the atrial electrode line ( 14 ) being configured to convey signals indicative of atrial events, and (2) a left-ventricular electrode line ( 30 ) extending to a left-ventricular sensing electrode ( 32 , 34 ), the left-ventricular electrode line ( 30 ) being configured to convey signals indicative of left-ventricular events, d. a control unit ( 54 , 54 ′) in communication with the right ventricular sensing unit ( 58 ) and the defibrillation shock generator ( 50 ), the control unit ( 54 , 54 ′) being configured to: (1) monitor the right ventricular rhythm from the right-ventricular sensing electrode ( 18 , 20 ), (2) detect ventricular fibrillation therein, and (3) trigger the defibrillation shock generator ( 50 ) to deliver a defibrillation shock via the ventricular defibrillation electrode ( 38 , 40 ) if ventricular defibrillation is detected, e. a evaluation unit ( 280 , 460 , 470 ) in communication with the control unit ( 54 , 54 ′), wherein the evaluation unit ( 280 , 460 , 470 ) is: (1) configured to derive the right ventricular rhythm independently of the right ventricular rhythm monitored from the right-ventricular sensing electrode ( 18 , 20 ) on the basis of at least one of (a) left-ventricular events, and (b) atrial events, and (2) configured to suppress the delivery of a defibrillation shock upon detection of a normal right ventricular rhythm.