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The aim of inotropic pacemakers is to restore the missing rate adaption of the heart in chrontropic incompetent patients. The input for these systems is the contractile status of the myocard (inotropy). There are different approaches of measuring the inotropic status which were compared in this study. One commercial pacemaker determines the inotropy by measuring the impedance between the tip of the pacemaker electrode and the pacemaker housing. Another pacemaker uses a specific electrode which measures the acceleration of the myocard during the contraction of the heart. The third analyzed system is a new development which uses a fiberoptic system to detect the flection of the myocardial wall. All three devices were tested on isolated beating pig hearts. The rate control of the pacemaker, the change of the measured acceleration and the amplitude of the fiberoptic sensor signal were analyzed while changing the preload and during application of positive inotropic drugs such as dopamine and noradrenaline. During the experiment the aortic pressure, flow and the signal of the fiberoptic sensor were recorded simultaneously and the measurands of the pacemakers and the inotropic parameter dP/dt were put in relation to these signals. The calculated pacing rate of the impedance sensing pacemaker and the fiberoptic system showed good correlation to dP/dt. This indicates a good adaption to the changed parameters of the heart. The pacemaker which senses the myocard acceleration also showed a good correlation but the adaption to the changed inotropy was delayed.