INITIAL EXPERIENCE WITH AN IMPLANTABLE HEMODYNAMIC MONITOR

Background Measurement of intracardiac hemodynamic parameters has been limited to brief periods in the acute care setting. We developed and evaluated an implantable hemodynamic monitor that is capable of measur ing chronic right ventricular oxygen saturation and pulmonary artery p ressure. Methods and Results The device consists of an electronic cont roller placed subcutaneously and two transvenous leads placed in the r ight ventricle (reflectance oximeter) and pulmonary artery (variable c apacitance pressure sensor). Implantation was performed in 10 patients with severe left ventricular dysfunction. Average implant pulmonary a rtery pressures were systolic, 52 +/- 16 mm Hg; diastolic, 29 +/- 11 m m Hg; and mean, 40 +/- 12 mm Hg. The mean right ventricular oxygen sat uration at implant was 51%. Provocative maneuvers, including postural changes, sublingual nitroglycerin, and bicycle exercise, demonstrated expected changes in measured oxygen saturation and pulmonary artery pr essures over time. At follow-up of 0.5 to 15.5 months, there were no s ignificant differences between pulmonary artery pressures or oxygen sa turation values transmitted from the device and simultaneous measureme nt with balloon flotation catheters. Four of the pulmonary artery lead s dislodged and three demonstrated sensor drift, whereas two of the ox ygen saturation sensors failed. Four patients died and four received t ransplants. Pathological study did not demonstrate injury to the right ventricular outflow tract or pulmonic valve. Conclusions Chronic meas urement of hemodynamic parameters in the outpatient setting with impla ntable sensor technology appears to be feasible. The devices are well tolerated without significant untoward effects, and the sensors genera lly function well over time, providing reliable information. Clinical usefulness remains to be established.