August 25, 2017Open Access
View Full PaperLong-term impact of intrathoracic impedance findings on survival and heart failure hospitalizations after cardiac resynchronization therapy in ICD Registry patients
Key Result
Having >15.1% of days above the OptiVol threshold was associated with increased mortality compared to <4.1% of days above threshold (HR 4.2; 95% CI 3.3-5.3).
Study Design
Type
Cohort (n=1,565)
Multicenter
Yes
Structured PICO
Do intrathoracic impedance threshold crossings predict mortality and heart failure hospitalizations in heart failure patients with CRT-D devices?
P
Population
1,565 heart failure patients with Medicare coverage and OptiVol-enabled CRT-D devices, followed for a median of 6.3 years.
E
Exposure
High burden of intrathoracic impedance threshold crossings (>15.1% of days above OptiVol threshold, highest quartile) or a single OptiVol crossing.
C
Comparator
Low burden of intrathoracic impedance threshold crossings (<4.1% of days above threshold, lowest quartile) or no crossings.
O
Outcome
Mortality and heart failure-related hospitalizations (HFH).hard clinical
Intrathoracic impedance threshold crossings are strongly associated with increased long-term mortality and heart failure hospitalizations in patients with CRT-D devices.
Main Result
Hazard Ratio: 4.2 (95% CI 3.3–5.3)
Abstract
Aims: To determine adjusted associations among OptiVol® threshold crossings, long-term survival, and hospitalizations among heart failure (HF) patients with Medicare coverage in the United States. Methods and results: A cohort with OptiVol®-enabled cardiac resynchronization therapy defibrillators (CRT-D) devices from the Implantable Cardioverter Defibrillator Registry was linked to both Medicare claims/summary data and Medtronic's CareLink® Network data. An extended multivariable Cox model was used to analyse associations among OptiVol® threshold crossings (treated as time-dependent covariates), mortality, and HF-related hospitalizations (HFH). We analysed N = 1565 patients with OptiVol®-enabled CRT-D devices (mean age 72.8, 28% women). The median follow-up was 6.3 years. Patients with >15.1% of days above OptiVol® threshold (highest quartile) had more than a 4-fold increase in mortality hazard ratio (HR) 4.2, 95% confidence interval (CI): 3.3-5.3 and more than a 3-fold increase in HFH (HR 3.2, 95% CI: 2.4-4.2) compared with patients having <4.1% of days above threshold (lowest quartile) after adjustment for key covariates. In addition, a single OptiVol® crossing was associated with significantly increased rates of both mortality (HR 1.87, 95% CI: 1.27-2.75) and HFH (HR 1.70, 95% CI: 1.28-2.27). Conclusion: In a CRT-D cohort with over 6 years of follow-up, both single OptiVol® crossings and time above OptiVol® threshold were associated with increased rates of mortality and hospitalization, which has important implications for clinical care. This is the first study integrating device data with Medicare outcomes to validate the long-term significance of OptiVol® findings.