Table V.

Selected outcome studies with impedance measurement in heart failure

Study	Patient target group	Objective	Results
ED-IMPACT72	Emergency department, age >65 y, dyspnea, heart failure, pulmonary disease	Determine changes in diagnosis and therapy with ICG hemodynamic data compared with the ED physician diagnosis	ICG data changed diagnosis in 5.4%, medication in 23.6%, and dosage in 25% of patients.
ESCAPE BIG substudy73	NYHA class IV, LVEF<30%, symptoms for congestion, prior hospitalization, systolic BP <125 mm Hg, and stable enough to not require catheterization	Evaluate changes in therapy with and without hemodynamic data from ICG and catheterization, determine deaths and days needed for hospitalization as a result of therapy decisions	No significant correlation between ICG measurement and hemodynamics measured from catheterization.
PREDICT74	Chronic heart failure, prior heart failure hospitalization, NYHA class II-IV	Analyze ICG data to determine low, average, or high risk for heart failure symptom, and to predict death and hospitalization	High risk for heart failure event within 14 d for patients with low stroke index <34 mL/m2 and high thoracic fluid >32 k Ω−1.
MIDHeFT50	Critically ill chronic heart failure requiring implanted investigational pacemaker	Determine timeframe for automated early detection of fluid, outcome of early hospitalization and therapy	Algorithm calculates impedance threshold to predict 12 of 14 hospitalizations, predicts fluid overload on average 18 d early.
European InSync Sentry Observational study49	Subjects with chronic heart failure with implanted CRT devices and audible alerts	To evaluate the utility of intrathoracic impedance monitoring for detecting heart failure deterioration in patients with an implanted cardiac resynchronization/defibrillation device	Adjusted for multiple events per patient, the alert detected clinical HF deterioration with 60% sensitivity and with a positive predictive value of 60%.
PARTNERS-HF52	Subjects with chronic heart failure with impedance-enabled CRT implanted devices	To determine the value of intrathoracic impedance and other diagnostic data to evaluate cardiovascular and heart failure–related adverse events and health care utilization	Patients with a fluid index crossing the predefined threshold in the 21-d evaluation period were twice as likely to have subsequent heart failure event (at 100-Ω d cut-off, 3.5 times higher risk).
Italian OptiVol-CRT Clinical Service Observational Group75	Subjects with chronic heart failure with impedance-enabled implanted CRT devices	To determine the association between device-determined diagnostic indices and heart failure hospitalization	Threshold crossing (>60-Ω d cut-off) resulted in 36% increased probability of heart failure hospitalizations.

ED-IMPACT, Emergent Dyspnea Impedance cardiography-aided Assessment Changes Therapy; ESCAPE BIG, Evaluation Study of Congestive Heart Failure and Pulmonary Artery Catheterization Effectiveness Bioimpedance cardiography substudy; PREDICT, Prospective Evaluation and Identification of Decompensation by ICG Test; MIDHeFT, Medtronic Impedance Diagnostics in Heart Failure Patients; EU Registry, European Observational InSync Sentry Study; PARTNERS-HF, Program to Assess and Review Trending Information and Evaluate Correlation to Symptoms in Patients with Heart Failure; BP, blood pressure; CRT, cardiac resynchronization therapy; HF, heart failure; ED, emergency department.