Human feasibility study of hemodynamic monitoring via continuous intrathoracic impedance monitoring

The ultimate hemodynamic sensor for an implantable device would provide information about cardiovascular performance including systolic function, diastolic function, preload, and afterload. We examined the potential clinical utility of simultaneous measurement of left ventricular pressure and continuous intrathoracic impedance in a group of 20 patients undergoing acute intravenous ablation for atrial fibrillation. Following baseline measurements of traditional left ventricular (LV) conductance volume (control), LV pressure and conductance measurement were repeated using alternate impedance stimulation and sensing vectors that encompassed combinations of the lung, left ventricle, right ventricle and left atrium, respectively. Various relative indices of LV function, including end systolic pressure to volume (conductance) ratio, end diastolic pressure to volume (conductance) ratio, and preload recruitable stroke work (analog) were derived by combining real-time pressure and conductance. The raw morphometry of the LV vector seemed to most closely resemble the gold standard LV conductance volume. For this vector, strong linear correlations between LV pressure and end systolic conductance (r = 3D0.84plusmn0.14), end diastolic conductance (r = 3D0.78plusmn0.10) and preload recruitable stroke work analog (r = 3D0.93plusmn0.05) were observed. The LV vector provides a robust continuous intracardiac hemodynamic signal that may be useful for quantifying cardiovascular function.