ABSTRACT
BACKGROUND: Inappropriate therapies are frequently delivered by implantable cardioverter-defibrillators (ICDs). We have investigated muscle perfusion as a means of augmenting arrhythmia discrimination by using implanted near-infrared spectroscopy. OBJECTIVE: To evaluate hemodynamic stability by monitoring muscle perfusion from within the ICD pocket, in fresh tissue and inside the scar capsule on preexisting ICD generators, during induced cardiac arrhythmias, in humans. METHODS: The sensor was implanted on or under the pectoral muscle, during ICD defibrillation threshold testing. A microvascular oxygenation trend indicator (O2 Index) was computed during 74 induced ventricular fibrillation and 34 normal sinus rhythm episodes in 34 patients and also during 28 atrial and 90 ventricular overdrive pacing episodes as simulations of supraventricular and ventricular tachycardias, respectively. RESULTS: On average, the change in oxygenation, based on the O2 Index, was statistically significant (P <.003) from baseline within 3 seconds following cardiac arrest. An optimized O2 Index, used for detecting the hemodynamic trend, exhibited a decreasing trend during ventricular fibrillation (P <.0001) and was different from that during normal sinus rhythm (P <.0001). The sensitivity for the detection of ventricular fibrillation was 100%, and the specificity for the rejection of normal sinus rhythm was 82% in the presence of scar tissue on the optical sensor. For a 35-mm Hg drop in the mean arterial pressure as the threshold for hemodynamic instability, the specificity for the rejection of hemodynamically stable atrial and ventricular pacing episodes was 93% and 71%, respectively. CONCLUSION: An implantable near-infrared spectroscopic sensor may be useful for hemodynamic monitoring during cardiac arrhythmias to prevent inappropriate therapy.
Subject(s)
Arrhythmias, Cardiac/diagnosis , Arrhythmias, Cardiac/therapy , Defibrillators, Implantable , Hemoglobins/chemistry , Muscle, Skeletal/blood supply , Spectroscopy, Near-Infrared/methods , Adult , Aged , Aged, 80 and over , Female , Hemodynamics , Humans , Male , Middle Aged , Prospective Studies , Sensitivity and SpecificityABSTRACT
Bronchial shunt flows in the recipients of the electrohydraulic AbioCor implantable replacement heart have been measured indirectly. A built-in compliance chamber accommodates the differential flow output required of the two ventricles of the AbioCor. An occluder mechanism regulates the flow differential. For a thoracic unit, given a beat rate, an occluder setting, and the pressure differentials across the replacement heart ventricles, the atrial pressure difference depends only on the level of shunt flow present in the vasculature. For a replacement heart recipient, the bronchial shunt is the dominant shunt flow. For patients implanted with the AbioCor, the beat rates and the occluder settings are known and the pressure differentials across the ventricles are estimated. Atrial pressures were measured using catheters. The bronchial shunt flow was deduced from in vitro characterization data based on these parameters. Available data from five patients in the ongoing clinical trial of AbioCor showed 0-1.4 L/minute bronchial shunt flows. Maximum variation for any individual patient was 1.1 L/minute.
