LONG-TERM RECORDING OF CARDIAC-OUTPUT VIA AN IMPLANTABLE HEMODYNAMIC MONITORING DEVICE

Long-term monitoring of central haemodynamics with implanted monitorin g systems might be valuable in managing heart failure patients. Such s ystems offer an opportunity for repeated 'semi-invasive' cardiac outpu t determinations according to the Fick principle. Five patients, four with chronic heart failure and one with chronic pulmonary disease, und erwent supine exercise testing during cardiac catheterization at 0, 2, 6 and 11 months after implantation of a right ventricular mixed venou s oxygen saturation sensor connected to an implantable haemodynamic mo nitor. The monitor provided a continuous measure of oxygen saturation via a radio-telemetry link to a metabolic cart capable of measurement of breath-by-breath oxygen consumption. Cardiac output was computed us ing oxygen consumption, mixed venous oxygen saturation, arterial oxyge n saturation by pulse oximetry and haemoglobin oxygen capacity. Biosen sor-derived oxygen saturation compared to blood samples from the pulmo nary artery showed an excellent correlation over time, r(2)=0.94 (impl ant), r(2)=0.91 (6-11 months). There was a strong correlation between semi-invasive-determined cardiac output using the biosensor and the in vasive technique, which persisted over the entire follow-up period. Re peated semi-invasive cardiac output measurements using an implanted ha emodynamic monitoring system in chronic heart failure patients is feas ible and the data may be of value for optimizing therapy.