Fluid Index Threshold Crossings Research Articles

Remote Monitoring With Appropriate Reaction to Alerts Was Associated With Improved Outcomes in Chronic Heart Failure: Results From the OptiLink HF Study.

Impedance-based remote monitoring (RM) failed to reduce clinical events in the OptiLink heart failure (HF) trial. However, rates of alert-driven interventions triggered by intrathoracic fluid index threshold crossings (FTC) were low indicating physicians' inappropriate reactions to alerts. We separated appropriate from inappropriate contacts to FTC transmissions in the OptiLink HF trial (Optimization of Heart Failure Management Using OptiVol™ Fluid Status Monitoring and CareLink™). Appropriate contacts had to meet the following criteria: (1) initial telephone contact within 2 working days after FTC transmission, (2) follow-up contacts according to study protocol, and (3) medical intervention initiated after FTC due to cardiac decompensation. We compared time to cardiovascular death or HF hospitalization between RM patients contacted appropriately or inappropriately and patients with usual care. In the RM group, at least one FTC alert was transmitted in 356 patients (70.5%; n=505). Of note, only 55.5% (n=758) of all transmitted FTCs (n=1365) were followed by an appropriate contact. While 113 patients (31.7%; n=356) have been contacted appropriately after every FTC, in 243 patients (68.3%; n=356) at least one FTC was not responded by an appropriate contact. Compared with usual care, RM with appropriate contacts to FTC alerts independently reduced the risk of the primary end point (hazard ratio, 0.61 [95% CI, 0.39-0.95]; P=0.027). RM appropriate reactions to FTC alerts are associated with significantly improved clinical outcomes in patients with advanced HF and implantable cardioverter-defibrillators.

Adequate contacts after remote monitoring alerts were associated with improved outcomes in chronic heart failure: results from the OptiLink HF study

Abstract Aims To investigate the effects of adequate reactions to telemedicine alerts triggered by fluid index threshold crossings (FTC) on clinical outcomes in the OptiLink HF trial. Methods We separated adequate from inadequate reactions to FTC transmissions in patients with remote impedance-based monitoring (RM) of fluid status in the OptiLink HF trial. Adequate contacts had to meet the following criteria: i) initial telephone contact within 2 working days after FTC transmission, ii) follow-up contacts according to study protocol, and iii) medical intervention initiated after FTC due to true fluid overload. We compared time to cardiovascular (CV) death or heart failure (HF) hospitalization and all CV- and HF-hospitalizations at follow-up between RM patients contacted adequately or inadequately and patients with usual care (UC). Results In the RM group, transmission of at least one FTC alert occurred in 356 patients (70.5%; n=505). While 113 patients (31.7%; n=356) have been contacted adequately after every FTC, in 243 patients (68.3%; n=356) at least one FTC was not responded by an adequate contact. Adequate responses to RM significantly reduced risk of the primary endpoint (hazard ratio (HR), 0.68; 95% confidence interval (CI) 0.48–0.95; p=0.025, figure 1), and led to a significantly lower number of CV (52.1±7.5 vs. 99.9±19.8; p=0.007) and HF hospitalizations per 100 patient years when compared with UC (26.1±4.4 vs. 67±15.2; p=0.007). Conclusion RM with adequate reactions to FTC alerts significantly reduced total number of both CV and HF hospitalizations and improved clinical outcomes in patients with advanced HF and implantable cardioverter defibrillator (ICD). Funding Acknowledgement Type of funding source: None

Handling of remote monitoring alerts according to the weekday of transmission: results from the OptiLink HF study

Abstract Background Remote monitoring of patients suffering from heart failure (HF) did not result in improved clinical outcomes in the OptiLink-HF trial. However, initiation of medical intervention after transmission of telemedicine alerts triggered by fluid index threshold crossings (FTCs) was low. The relation between weekday of transmission of FTC and subsequent patient contact is unknown. Methods Patients enrolled in the intervention arm of the OptiLink HF trial (n=505, age 66.1±10.1, male 77.2, EF 26.7±6.1%) were analyzed according to the weekday of transmission of FTC. Transmissions of FTC on Mondays to Thursdays were categorized as TD1, Fridays to Sundays as well as bank holidays as TD2. Primary endpoint was time between transmission and telephone contact; secondary endpoints were subsequent medical intervention and hospitalizations. Results During a follow-up of 18 months, 1364 FTC (866 (63.5%) categorized to TD1, 498 (36.5%) to TD2) alerts occurred in 356 patients. In 46.2% of FTC same day telephone contact was performed in group TD1 compared to 18.3% in group TD2 (p<0.001). Accordingly, the median time to contact was significantly longer in TD2 compared to TD1 (2 (1–3) vs. 0 (0–1); p<0.001). Rates of no telephone contact were not different between the groups (12.1% vs. 12.4%; p=0.866). Although, signs of worsening HF were prevalent in 32.4% in TD1 vs. 32.1% in TD2 (p=0.996), initiation of a pharmacological intervention was more likely in TD1 compared to TD2 (27.9% vs. 22.9%; p=0.041). No differences existed concerning hospitalization for HF within 30 days after FTC (3.9% vs. 3.4%; p=0.636). Conclusion Transmission of FTC alerts during weekends and on bank holidays were less likely associated with timely patient contacts and initiation of pharmacological intervention than during the week. Telemedical centers providing 24/7 remote monitoring service might help to optimize patient care. Funding Acknowledgement Type of funding source: None

Atrial Tachyarrhythmias Temporally Precede Fluid Accumulation in Implantable Device Patients

The complex relationship between heart failure and atrial tachyarrhythmias (AT/atrial fibrillation [AF]) is not well understood. We examined the temporal association between changes in intrathoracic impedance, suggesting thoracic fluid accumulation, and AT/AF occurrence in cardiac resynchronization therapy-defibrillator and implantable cardioverter defibrillator (ICD) patients. A retrospective analysis was conducted on stored implantable device data to identify patients with automatic monitoring of daily AT/AF burden and intrathoracic impedance. Daily population trends in AT/AF burden before and after a fluid index threshold crossing (FIC) were determined. A total of 73,018 patients (68 ± 12 years, 51% ICD, 75% male) were evaluated over 18.6 ± 11.5 months. Kaplan-Meier analysis indicated a significantly higher probability of FIC events in the first month following the onset of persistent AT/AF when compared to a matched group without persistent AT/AF (hazard ratio [HR] 1.65, 95% confidence interval [CI] [1.58, 1.72], P < 0.001). Conversely, patients were significantly more likely to experience an episode of persistent AF in the first month after the FIC event (HR 1.32, 95% CI [1.08, 1.63], P = 0.008). The probability of a fluid index crossing within 30 days of the onset of persistent AT/AF was significantly lower in a subgroup of patients with adequate rate control (35.8% [34.3-37.4%] vs 42.0% [39.6-44.6%]; HR 1.24 [1.13-1.36]). Thoracic fluid accumulation, as indicated by decreasing intrathoracic impedance, was more likely to occur immediately after the onset of persistent AT/AF, especially in the presence of inadequate rate control. Likewise, the onset of persistent AT/AF was more likely following a decrease in intrathoracic impedance.

ICD and CRT-D Heart Failure Patients with an Intrathoracic Impedance Fluid Index Threshold Crossing Have Significantly Increased Risk of Ventricular Tachyarrhythmias

The association between intrathoracic impendence (IP) and nonsustained (NSVT) and sustained (VT/F) ventricular arrhythmia occurrence in heart failure (HF) patients is not fully understood. We investigated the relationship between VT/VF and threshold crossings of an intrathoracic impedance-derived fluid index (FTC) in HF patients with ICD/CRT-D devices.

A Critical Link Between Heart Failure Self-care and Intrathoracic Impedance

Effective self-care is regarded as essential to the management of heart failure (HF). The influence of self-care on HF decompensation, however, is not well understood. Accordingly, we examined the relationship between self-care and fluid accumulation accompanying worsening HF as indexed by decreasing intrathoracic impedance (Z). Z data were collected from 58 HF patients with OptiVol enabled devices (Medtronic Inc, Minneapolis, Minnesota). Heart failure self-care was measured with the European Heart Failure Self-care Behaviour Scale. Regression modeling was used to describe the influence of HF self-care on the likelihood of a fluid index (FI) threshold crossing, the number of threshold crossings, and number of days spent above threshold. Patients were elderly (74.98 [SD, 8.12] years), with a mean left ventricular ejection fraction of 26.21% (SD, 9.77%), and 63.7% had class New York Heart Association III HF. Patients were followed up for 317 (SD, 96) days; 65.5% had FI threshold crossings (mean 1.45 [SD, 1.56] crossings), spending an average of 33.8 (SD, 42.4) days above FI threshold. Controlling for age, sex, left ventricular ejection fraction, functional class, and duration of follow-up, each additional point on the European Heart Failure Self-care Behaviour Scale was associated with an increase in the odds of having had an FI threshold crossing (adjusted odds ratio, 1.201; 95% confidence interval, 1.013-1.424; P<.05) and more days spent above FI threshold (incidence rate ratio, 1.051; 95% confidence interval, 1.002-1.102; P<.05). Intrathoracic impedance measurements obtained from implantable devices provide important information regarding the influence of self-care on fluid accumulation in patients with HF.

Improved Algorithm to Detect Fluid Accumulation via Intrathoracic Impedance Monitoring in Heart Failure Patients With Implantable Devices

Background Intrathoracic impedance fluid monitoring has been shown to predict worsening congestive heart failure (CHF) in patients with implantable devices. We developed and externally validated a modified algorithm to identify worsening heart failure (HF) by using intrathoracic impedance. Methods and Results The modified algorithm was developed by using published data from 81 CHF subjects averaging 259 days of follow-up. Device-measured daily impedance was input to both the existing and the modified intrathoracic impedance fluid monitoring algorithms to determine a reference impedance and a fluid index (FI). Separate validation sets included 326 cardiac resynchronization therapy device (CRT-D) patients with an average 333 days of follow-up (group 1) and 104 CRT-D/implantable cardioverter/defibrillator (ICD) patients followed for an average of 520 days (group 2). Clinicians and patients in group 2 were blinded to impedance and FI data. HF events included adjudicated HF hospitalizations or emergency room visits. Sensitivity was defined as the percentage of HF events preceded by FI exceeding the predefined threshold (60 Ω-d) within the last 2 weeks. Unexplained detections were FI threshold crossing events not followed by a HF event within 2 weeks. The modified algorithm significantly decreased unexplained detections by 30% ( P = .01; GEE) in the development set, 30% ( P < .001) in the group 1 validation set, and 43% ( P < .001) in group 2. Sensitivity did not change significantly in any group. Simulated monthly review of FI threshold crossings identified subjects at significantly greater risk of worsening HF within the next 30 days. Conclusions A modified intrathoracic impedance based fluid detection algorithm lowered the number of unexplained FI threshold crossings and identified patients at significantly increased immediate risk of worsening HF.

Significant Increase in the Incidence of Ventricular Arrhythmic Events After an Intrathoracic Impedance Change Measured With a Cardiac Resynchronization Therapy Defibrillator

Cardiac resynchronization therapy defibrillator (CRT-D) devices are now capable of monitoring changes in intrathoracic impedance. Intrathoracic impedance monitoring resulting in a fluid index threshold crossing has been proven to predict heart failure (HF) exacerbations. We retrospectively investigated the relationship between changes in intrathoracic impedance and the occurrence of arrhythmic events. From 282 patients with New York Heart Association class III or IV HF who were implanted with a CRT-D device with a fluid index feature based on intrathoracic impedance monitoring capabilities, arrhythmic events were retrospectively analyzed in terms of the threshold crossings. The patients were divided into 2 groups: those with fluid index threshold crossings and those without threshold crossings. A total of 4,725 tachyarrhythmic events were reported in 129 patients (46%), and there were 221 fluid index crossing events in 145 patients (51%) during 10.0 ± 3.2 months. Tachyarrhythmic events were more frequently recorded in patients with threshold crossing events than in those who did not experience a threshold crossing (3,241 vs. 1,484 events, P<0.0001). Ventricular tachyarrhythmic events mainly occurred within the first 30 days after the threshold crossing event; however, a similar trend was not observed for the atrial tachyarrhythmic events. Intrathoracic impedance monitoring may predict arrhythmic events, especially ventricular arrhythmias, in patients with HF and provides an additional management tool.

Insights From Internet‐Based Remote Intrathoracic Impedance Monitoring as Part of a Heart Failure Disease Management Program

Changes in intrathoracic impedance (Z) leading to crossing of a derived fluid index (FI) threshold has been associated with heart failure (HF) hospitalization. The authors developed a remote monitoring program as part of HF disease management and prospectively examined the feasibility and resource utilization of monitoring individuals with an implanted device capable of measuring Z. An HF nurse analyzed all transmitted data daily, as they were routinely uploaded as part of quarterly remote device monitoring, and called the patient if the FI crossed the threshold (arbitrarily defined at 60 Omega) to identify clinically relevant events (CREs) that occurred during this period (eg, worsening dyspnea or increase in edema or weight). A total of 400 uploads were completed during the 4-month study period. During this period, 34 patients (18%) had an FI threshold crossing, averaging 0.52 FI threshold crossings per patient-year. Thirty-two of 34 patients contacted by telephone (94%) with FI threshold crossing had evidence of CREs during this period. However, only 6 (18%) had HF hospitalizations, 19 (56%) had reported changes in HF therapy, and 13 (38%) reported drug and/or dietary plan nonadherence. The average data analysis time required was 30 min daily when focusing on those with FI threshold crossing, averaging 8 uploads for review per working day and 5 telephone follow-ups per week. Our pilot observations suggested that Internet-based remote monitoring of Z trends from existing device interrogation uploads is feasible as part of a daily routine of HF disease management.

Changes in Intrathoracic Impedance are Associated With Subsequent Risk of Hospitalizations for Acute Decompensated Heart Failure: Clinical Utility of Implanted Device Monitoring Without a Patient Alert

Background Acute decreases in intrathoracic impedance monitoring have been shown to precede heart failure hospitalization in a limited population of heart failure patients. We evaluated the relationship between changes in intrathoracic impedance with hospitalizations associated with acute decompensated heart failure (ADHF) in patients with cardiac resynchronization therapy plus defibrillator (CRT-D) devices. Methods and Results The study enrolled 326 heart failure patients who had received CRT-D with impedance-monitoring capabilities (InSync Sentry, Medtronic). The date and duration of ADHF hospitalizations were retrospectively identified before device interrogation to obtain device diagnostic information. During 333 ± 96 days of device monitoring, 228 patients experienced 540 intrathoracic impedance fluid index threshold crossings events (TCE) at the nominal threshold value (60 Ω. days). During the initial 4-month evaluation period, 17 subjects experienced 22 ADHF hospitalizations. In the subsequent monitoring period (206 ± 95 days), 18 patients experienced 24 hospitalizations. The occurrence of TCEs during the monitoring period was independently correlated with the subsequent rate of ADHF hospitalization such that each TCE event during the risk stratification period was associated with a 35% increased risk for ADHF hospitalization in the remaining study period ( P = .001). Poisson regression indicated that the subgroup of patients with an annual average rate of more than 3 threshold crossings per year during the monitoring period were significantly more likely to be hospitalized for ADHF than those patients with no TCE during the monitoring period (0.76 [0.20–1.325] vs. 0.14 [0.05–0.23] hospitalizations/subject/y [95%CI]; P = .02). Likewise, Kaplan-Meier analysis revealed that subsets of patients with more than 3 TCEs per year or with more than 30 days per year above threshold during the risk stratification period had significantly higher rates of ADHF hospitalization during the post risk stratification period than subjects with no TCE events, respectively. Conclusions In this multicenter retrospective cohort study, serial decreases in intrathoracic impedance sufficient to generate a fluid index threshold crossing as well as the net duration that the index remained above threshold during a 4-month monitoring period were associated with subsequent risk of ADHF hospitalization.

Thoracic Impedance Measured Via Implantable Devices Provides Advanced Warning of Signs and Symptoms of Worsening Heart Failure in Addition to Hospitalization

Background: Decreasing thoracic impedance (Z) measured via an implantable device (Insync Sentry, Medtronic) has been shown to be associated with heart failure (HF) hospitalization. However, most clinically relevant events (CRE) associated with worsening heart failure do not result in hospital admission. We examined the association of CRE with device-based Z recordings. Methods: Device-recorded Z and health record data from 69 CRT-D patients (73 ± 20 yr, 49 Male) were retrospectively reviewed. The diagnostic fluid index (FI) was automatically derived from consecutive negative deviations in the actual measured daily Z from the calculated basal or reference Z. Fluid Index values higher than the programmed threshold constituted a device classified event. HF hospitalizations, CRE's, (including documented signs and symptoms of worsening HF), acute changes in diuretic therapy (DT), and surgical device or lead revisions (LR) were identified for association with FI threshold crossings. Results: During the mean follow-up of 339 ± 46 days, 81 crossings of the nominal FI threshold (60 Ω·days) occurred in 48 patients. Four of 9 HF hospitalizations were preceded by FI threshold crossing (44%). CREs were correlated with 25 crossings in 19 patients. Ten CREs were not associated with a threshold crossing. Seven additional crossings were due to appropriate reductions in DT. Ten crossings in 6 patients were associated with LR. Thus, 35 crossings (43%) remained unexplained in 23 patients (33%). The average rate of unexplained FI crossings was 0.55/patient·yr (median = 0/patient·yr). Increasing the FI threshold from 60 to 80 Ω·days would have resulted in no loss in sensitivity to HF hospitalization but would have decreased the sensitivity to CREs from 82% to 61%. However, increasing the fluid index threshold to 80 Ω·days would have significantly reduced the number of unexplained crossings by 34% (p < 0.01). Conclusion: Intrathoracic impedance measurements performed via implantable devices provide important diagnostic information regarding clinically relevant events associated with worsening heart failure in addition to heart failure hospitalization. Individual optimization of programmable parameters may further increase the utility of the diagnostic feature.

Surgical Revision of Implantable Device “Pocket” or Lead Can Alter Thoracic Impedance-Based Indices of Worsening Heart Failure

Background: A CRT-D device (Insync Sentry – Medtronic) monitors thoracic fluid accumulation via intrathoracic impedance (Z). The programmable fluid index (FI) is determined by the cumulative consecutive negative deviations in the daily Z from the calculated adaptive reference line. Increased FI is detected by a programmed threshold. Declining intrathoracic Z and FI threshold crossings have been associated with heart failure (HF) decompensation. However, the impact of surgical revisions of the device or lead on the clinical utility of the derived index has not been evaluated.