Feasibility of Using Intracardiac Impedance Measurements for Capture Detection

Abstract

Energy consumption and longevity of modern pacemakers are determined by the controlling electronic circuitry and by the stimulation energy. While with technological progress the electronics' energy consumption has been reduced significantly, clinical practice shows that many cardiac pacemakers are programmed to suboptimal settings with regard to minimization of pacing energy consumption. Several methods for optimizing pacemaker output settings have been proposed in the past. The most promising concept is an output parameter optimizing pacemaker with automatic capture detection. We examined whether it is possible to distinguish between effective and ineffective pacemaker stimulus capture by analyzing high pass filtered intracardiac impedance signals that are derived from standard bipolar pacing leads. In one series of 11 patients undergoing replacement or implantation of chronic bipolar pacemakers, four patients during electrophysiology studies, and eight volunteers undergoing invasive electrophysiology trials, we examined intracardiac impedance signals obtained with various stimulation rates and output parameter settings. Additionally we analyzed a series of five patients with implanted pacemakers that can measure and telemeter intracardiac impedance signals. Several evaluation concepts have been analyzed regarding their ability to discriminate between effective and ineffective stimuli. We developed an adequate algorithm that detects capture or loss of capture at different output parameter settings based on intracardiac impedance analysis. The sensitivity is 98.5% and specificity is 91% to loss of capture for the currently investigated algorithm and this can be used to determine the optimal setting of pulse width and amplitude with regard to energy consumption. This concept is currently under realization in the external programmer and in the future an implementation of these algorithms within the pacemaker itself is intended.

Algorithm for ventricular capture verification based on the mechanical evoked response

“…These results are somewhat less favourable than those achieved in the only other publication implementing impedance-based capture verification (ALT et al, 1992). However, the authors of that paper provided no information regarding either their algorithm or their sampling technique, and their work was pursued no further.…”

“…This approach was first used by ALT et al (1992) with only preliminary results and was not further investigated. To the best of our knowledge, this publication, which did not disclose any detailed information on its algorithm, is the only one in the literature to date.…”

Reduction of Pacing Output Coupling Capacitance for Sensing the Evoked Response

“…Different methods for autocapture have been explored by researchers in the implantable pacemaker industry. Among various capture verification schemes, [3][4][5] automatic detection of the evoked response (ER) has drawn the most attention since it may be achieved with standard pacing electrodes. A major obstacle for autocapture by ER detection is the pacing induced afterpotential (AP).…”

Intrathoracic and Ventricular Impedances are Associated with Changes in Ventricular Volume in Patients Receiving Defibrillators for CRT

“…2 Moreover, cardiac impedance as a measure of volumes has been theorized in clinical pacing, and has been proposed as part of capture detection and rate response algorithms. 3,4 Some modern implantable cardioverter defibrillators (ICDs) are able to monitor intrathoracic impedance to detect pulmonary fluid overload. [5][6][7] Assessment of intrathoracic impedance is achieved by measuring impedance between the device case and the lead in the right ventricle (RV).…”