clinical applications of remote implantable cardioverter

DEVICE THERAPY

REVIEW ARTICLE

Clinical Applications of Remote ImplantableCardioverter-Defibrillator Monitoring: CurrentStatus and Future Directions1JACOB C. JENTZER, MD and 2JOHN H. JENTZER, MD

1Duke University Medical Center, Durham, NC2Dixie Regional Medical Center, St. George, UT

ABSTRACT. Implantable cardioverter-defibrillator and cardiac resynchronization devices areintegral for reducing mortality in many heart failure patients. Monitoring of these devices can befacilitated using wireless remote transmission. Remote monitoring can lead to early detection ofimportant events such as device or lead malfunction, pacing abnormalities, arrhythmias, anddevice-delivered antiarrhythmia therapy. Studies of remote monitoring show a reduction in theresponse time to clinical events. Remote monitoring may safely reduce the need for frequent officedevice checks and facilitate triage of device-detected events. Monitoring of several device-detectedparameters can predict heart failure decompensation, and interventions based on this informationmay prevent heart failure hospitalization. Ongoing clinical studies will further elucidate thebenefits of an expanding array of remote monitoring possibilities.

KEYWORDS. ambulatory monitoring, artificial cardiac pacing, cardiac arrhythmias,implantable defibrillators, heart failure.

ISSN 2156-3977 (print)ISSN 2156-3993 (online)

’ 2011 Innovations in Cardiac

Rhythm Management

Introduction

Implantable cardioverter-defibrillators (ICDs) reduce all-cause mortality by preventing sudden death in patientswith a history of sustained ventricular arrhythmias1 andin patients with left ventricular (LV) systolic dysfunctionat high risk of ventricular arrhythmias.2 Addition ofcardiac resynchronization therapy (CRT) to ICDs (CRT-D)via biventricular pacing provides a further reduction inmortality in populations with LV systolic dysfunction,QRS prolongation and moderate-to-severe heart failure(HF) symptoms.3,4 In patients with LV systolic dysfunc-tion, prolonged QRS and mild-to-moderate HF symp-toms, CRT-D therapy reduces the incidence of HFhospitalizations, improves indices of LV function andremodeling, and may reduce mortality beyond ICD

alone.5 In 2007, over 234,00 ICDs and over 148,000 CRT-Ds were implanted in North America.6 Monitoring ofthese devices has placed an increasing burden on theelectrophysiology device community due to regularlyscheduled in-office ICD follow-ups which usually do notresult in clinical intervention.7–9 Expert consensus recom-mends ICD follow-up every 3–6 months,6 but clinicallyimportant events between clinic visits may be silent untilthe next scheduled device interrogation. Remote monitor-ing (RM) via periodic wireless downloading of devicedata can provide more frequent surveillance of devices,allowing for early problem identification and clinicalintervention.10 RM may safely allow reduced frequency ofin-office device checks,9 which could translate intoreductions in healthcare costs.11–14

Remote monitoring basics

RM of ICD and CRT-D devices has become an accepted6

and evolving strategy for device surveillance since itsclinical introduction by Biotronik in 2000.15–17 Each majordevice manufacturer has a proprietary wireless RM

The authors report no conflicts of interest for the published content.Manuscript submitted May 23, 2011, final version accepted June 6,2011.Address correspondence to: John Jentzer, MD, SouthwestCardiology Associates, Dixie Regional Medical Center, 1380 EastMedical Center Drive, St. George, UT 84790. E-mail: [email protected]

The Journal of Innovations in Cardiac Rhythm Management, 2 (2011), 430–441

The Journal of Innovations in Cardiac Rhythm Management, August 2011 430

system: Biotronik (Lake Oswego,OR) Home Monitoring,Boston Scientific (St. Paul, MN) Latitude, Medtronic(Mounds View, MN) CareLink, and St. Jude (St. Paul,MN)Merlin.net (previously HouseCall Plus). These sys-tems share the capability to transmit device diagnosticinformation automatically to a local receiver which sendsthis information transtelephonically to a central server,allowing access by providers who can receive clinicalalerts.15–17 Depending on the system, device data can bedownloaded automatically each day or downloads mayonly occur when triggered by the patient or a devicealert.16 Remote device reprogramming is not currentlyavailable on any of these systems. Further details regardingthe technical specifications of the different RM systems arereviewed elsewhere.15–17 Patterned after remote pacemakermonitoring of battery voltage, magnet rate, and currentheart rhythm, modern ICD and CRT-D devices monitor amuch broader array of parameters. Pacing and shock leadimpedance, device-triggered alerts, sensing function, pro-grammed device parameters, percent pacing and sensingin each chamber, and review of detected arrhythmias andtherapies with stored or real-time electrograms can bemonitored (Table 1).15 Device-based parameters and algo-rithms for HF monitoring are being developed forincorporation into clinical decision making.18 We hopethat this evolving RM armamentarium may translate intobetter patient outcomes and health care savings.

Remote monitoring of ICD and CRT-Dpacemaker function

Analogous to standard pacemaker evaluation, RM canconfirm proper pacing function of ICD and CRT-D devicesand can identify the need for in-office reprogramming

to optimize device function. Abnormal pacing function cancontribute to worsening HF in ICD and CRT-D patients,and remote monitoring will disclose the amount of rightventricular (RV) pacing or biventricular pacing. ExcessiveRV pacing (above 40%) is associated with increasedmortality and HF events in patients with ICDs19 andmay predispose to ventricular arrhythmias20 and attenu-ated ICD benefit.21 Excessive RV pacing can often beminimized by lengthening the programmed AV delay oruse of pacing-minimization device algorithms, but mayrequire device upgrade to include CRT, particularly inpatients who become pacing dependent.22

Inadequate percentage of biventricular pacing (below93%) can eliminate the clinical benefits of CRT.23,24 RMcan detect drops in percent biventricular pacing, warrant-ing a full evaluation to identify the etiology.25 Loss of LVpacing capture in CRT-D devices due to LV leadmalfunction is suggested by a dramatic change in theLV pacing resistance, which must be confirmed withformal pacing threshold testing in a device clinic. Anexcessively long programmed AV delay may allow in-trinsic conduction through the native conduction systemto pre-empt biventricular pacing, especially during exer-tion. Evaluation of electrograms with their markerchannels will disclose ventricular sensing rather thanbiventricular pacing. Atrial tachyarrhythmias (ATs),supraventricular tachyarrhythmias (SVTs) or sinus tachy-cardia with ventricular rates exceeding the upper ratelimit of the pacemaker will inhibit biventricular pacing,25

as can frequent ventricular premature beats. In CRT-Dpatients with atrial fibrillation, AV nodal ablation may berequired to yield the full benefit of biventricular pacing.26

Remote monitoring of ICD lead integrity

Oversensing of non-physiological signals is an importantnon-arrhythmic cause of inappropriate ICD shocks,generally due to lead fracture, insulation breaks, orlead–header connection problems.27 The majority of ICDsystem complications are related to lead integrity failure,which continues to be a significant clinical problem.28

Rates of modern ICD lead failure are relatively low (0.6%/year), but can be higher with certain high-risk ICD leadssuch as the Medtronic Sprint Fidelis lead (3.8%/year,hazard ratio 6.4);29,30 yearly lead failure rates appear to

accelerate over time.31 Changes in lead impedance andshort sensing intervals from lead fracture can be identifiedearlier with RM, allowing timely clinical intervention.32,33

Figure 1a illustrates an abrupt increase in ICD lead pacingimpedance due to a lead fracture. Electrograms and theirmarker channels downloaded remotely from Latitude(Figure 1b) reveal oversensing of noise and confirm thediagnosis. Changes in lead impedance alone are notadequately sensitive for lead fracture,33–35 because over-sensing is often the first manifestation of lead fracture.35–37

Device reprogramming with a downloadable lead integ-rity algorithm may improve lead fracture detection byidentifying oversensing and increases in impedance.33

This algorithm can prevent many inappropriate ICDshocks in patients with Sprint Fidelis leads,33 but remains

Table 1: Remotely monitored device parameters

System statusP and R wave sensing and sensing integrityPacing thresholdsLead impedanceBattery status (voltage and charge time)Rhythm statusPercentage paced and sensed events

Right ventricular pacing percentageBiventricular pacing percentage

Average heart rate (day and night)Intrinsic heart rate and AV interval

Tachyarrhythmia burdenMode switch episodesAtrial/ventricular high rate episodesDuration/percentage of time in ATVentricular rate during AT

Device-delivered therapyAntitachycardia pacingShocks (cardioversion, defibrillation)

Device electrogramsHeart failure status (selected devices)Heart rate variabilityPatient activity levelIntrathoracic impedance

Adapted from reference 12. AT, atrial tachyarrhythmia.

J C Jentzer and J H Jentzer

431 The Journal of Innovations in Cardiac Rhythm Management, August 2011

unable to completely prevent inappropriate ICD shocks inpatients with fractured leads.36 Further analysis of down-loaded device data can differentiate lead fracture fromconnection problems and normal lead function in patientswith high-impedance lead integrity algorithm alerts.37

Lead malfunction may also cause ventricular under-sensing, which can prevent delivery of appropriatetherapy for a ventricular arrhythmia. RM may detectmore than 90% of lead-related complications and reducesymptomatic lead failure episodes by half,32 whilereducing the time to recognition of lead complications.38

Continuous follow-up in a device clinic plus RM isrecommended for patients implanted with a high-risklead.39 Oversensing of physiologic signals, such as T-waveoversensing (Figure 2) or sensing of myopotentials40 may

be corrected with a change in device sensitivity or mayrequire lead repositioning or implantation of a new lead.

Remote monitoring of arrhythmias

RM provides an effective means to evaluate device-detected arrhythmias and device-delivered therapy suchas antitachycardia pacing (ATP), low-energy cardiover-sion, and defibrillation. RM systems allow accurateevaluation of stored electrograms taken during sympto-matic or asymptomatic episodes of arrhythmias ordevice therapy.41 Electrogram analysis helps determinethe appropriateness and effectiveness of device-deliveredtherapy and can identify device or lead malfunctions and

Right Ventricular

A

B

Pace Impedance

Shock

Shock

(AS)

VT RVP-VF

VF

VF LVS LVS LVSRVS

VTVF

V-DurV-Detect

RVS488

193

160643

645

LVS VF VT VFVF128 215

308 300

320

320

320 320 320 320

3 0 0 0 0 0

300 198293 208163

1380 155 445

PVP

PVC VT VT LVS

PVP

RVP

LVP LVP LVP LVP LVP

RVP RVP RVP RVP

PVP

605 245LVP-Tr VF

350

PVP

(AS) (AS) AS AS AS ASβ48β58β23β25β25β30β20

A

RV

1,6001,3401,080

820560300

0

0 Nov 2010

Nov 2010

Dec 2010

Dce 2010756555453525

Shock Impedance

Figure 1: (a) Ventricular pacing impedance histogram downloaded from Boston Scientific Latitude showing an abrupt rise inright ventricular (RV) pacing impedance (top) in November 2010 at the time of lead fracture. (b) Electrograms downloadedfrom Boston Scientific Latitude showing right atrium (top), right ventricle (middle) and far-field right ventricle (bottom). Noiseon the RV sensing electrogram (middle) is indicative of RV lead fracture, leading to oversensing interpreted by the device asventricular tachyarrhythmias and treated by antitachycardia pacing (V-Detect, end of strip).

Clinical Applications of Remote Implantable Cardioverter-Defibrillator Monitoring


adverse effects related to device therapy. If device therapywas not effective, a change in device programming,medications, or hardware configuration may be neces-sary. Changes in ICD programming or antiarrhythmicmedication may require formal in-hospital evaluation ofcardioversion and defibrillation thresholds and ATPefficacy, such as with device-based non-invasive pro-grammed stimulation.

Ventricular arrhythmias and ICD shocks

Although ICDs reduce mortality by preventing death dueto ventricular arrhythmias,42 patients receiving ICD shockhave a higher risk of both arrhythmic and pump failuredeath than patients without ICD shocks.43 Patients withmore frequent ICD shocks have a higher mortality thanpatents with fewer ICD shocks.44 The mortality risk is

greater for appropriate ICD shocks (treated ventriculararrhythmias) than for inappropriate ICD shocks,43,45

which are most often due to AT or other SVTs and lessoften due to ventricular oversensing (typically from leadfailure).35 Inappropriate ICD shocks due to lead complica-tions may not pose an excess mortality risk.7 Earlydetection is paramount because ICD shocks correlate withHF instability, often requiring adjustment of medications,clinical assessment and/or device reprogramming.46

Strategies to avoid inappropriate ICD therapy due toSVT include antiarrhythmic agents, catheter ablation, ordevice programming of atrial fibrillation and sinustachycardia discriminators.35,47 ATP can be effective inmore than 70% of ventricular tachycardia (VT) episodes,safely preventing unnecessary ICD shocks.48,49 UnlikeICD shocks, VT episodes terminated by ATP may notconfer an adverse prognosis.44 ATP can occasionally beassociated with proarrhythmia such as acceleration of VT

Figure 2: Electrograms from Biotronik Home Monitoring showing far-field ventricular (top), right atrium (middle) and rightventricle (bottom). VF markers overlie the T wave, indicating T wave oversensing. VS indicates ventricular sensing; VF indicatesventricular sensing in the ventricular fibrillation zone; Det VF indicates ventricular fibrillation detection.



rate,49 in which case ATP should be eliminated. Frequentepisodes of VT may require pharmacologic or ablativeintervention, particularly when device therapy is ineffec-tive.50,51 Figure 3 shows electrograms from an episode ofunsuccessful ATP therapy for sustained VT, whichprompted referral for VT ablation that successfullyeliminated most of the patient’s ventricular arrhythmiaburden.

Atrial arrhythmias

Symptomatic and asymptomatic AT are common in HFpatients, and may be identified during the first post-implant year in up to one-fourth of CRT-D recipients whoare in sinus rhythm at the time of implantation.52,53

Knowledge regarding the incidence, duration, frequency,and ventricular rate response of AT can be gleaned easilyusing RM (Figure 4).52 AT episodes are one of the mostcommon clinical alerts identified by RM,10,54 and device-detected AT episodes predict worse outcomes in ICDand CRT-D patients.55 AT can interfere with properdevice functioning by preventing optimal biventricularpacing25,26 or causing inappropriate ICD shocks.35 RMmay allow earlier intervention for new or worseningdevice-detected AT,56 but it remains unclear if earlydetection of asymptomatic AT improves clinical out-comes. Device-detected atrial high-rate episodes corre-spond to AT and predict increased stroke risk.57

Mathematical modeling suggests that early initiation ofanticoagulation based on asymptomatic device-detectedAT could prevent embolism and stroke,58 and an ongoingrandomized trial will directly test this hypothesis.59

Clinical trials of remote device monitoring

Whereas transtelephonic pacemaker monitoring appearsuseful primarily for battery status determination,60

recent clinical trials using RM of ICD and CRT-D devicesdemonstrate earlier identification of clinical events10 andsafe reduction in clinic visits.9 The CONNECT (ClinicalEvaluation of Remote Notification to Reduce Time toClinical Decision) trial randomized 1,997 Medtronic ICDand CRT-D patients to standard in-office assessmentwith or without RM, and showed decreased time toclinical decision making by 17 days (more than 75%)and reduced healthcare utilization days with RM.10

The majority of remotely detected clinical events inCONNECT were prolonged AT episodes, consistent withprior studies.54 The TRUST (Lumos-T Safely ReducesRoutine Office Device Follow-up) trial randomized 1,339Biotronik ICD patients to standard office-only follow-upevery 3 months or less frequent office visits plus RM anddemonstrated a 45% reduction of in-office visits and areduction in time to respond to clinical alerts using RM,without increasing adverse events.9 TRUST confirmedthe safety of using RM in lieu of more frequent officevisits for device checks, showing that 85% of follow-upsbetween 3 and 12 months after implantation can beaccomplished remotely and that more than 90% ofscheduled clinic device checks did not require interven-tion. These studies confirm the results of smaller studiessuggesting the ability of RM to reduce response time toclinical events54,61 and reduce in-hospital follow-upvisits.14,62 Earlier identification of clinical events by RMdid not translate into an improvement in clinicaloutcomes in either CONNECT10 or TRUST.9 Smallstudies suggest that a reduction in clinic visits by RM

Figure 3: Electrograms (right atrium, top and right ventricle, bottom) downloaded from Medtronic CareLink demonstratingventricular tachyarrhythmia that is not terminated with ATP (VT Rx 1 Burst), indicated by persistent tachycardia sensing afterantitachycardia pacing. TS indicates tachycardia sensing; TP indicates tachycardia pacing.



may reduce healthcare costs,12–14 particularly for patientswith longer driving distances,11 but we await formaleconomic analysis from larger trials for confirmation.Further cost savings are possible if early detection of clinicalevents by RM leads to interventions preventing hospitaliza-tion, as suggested in CONNECT by a reduced number ofhospital days.10 The observational ALTITUDE study com-pared 69,556 Boston Scientific ICD and CRT-D patients whounderwent RM with 116,222 similar patients who receivedin-office device follow-up only, and identified a 50%mortality reduction for those patients undergoing RM, withbetter survival at 1 and 5 years.7 The non-randomizeddesign of ALTITUDE limits conclusions about causality, butbaseline demographics did not differ between the twogroups, so a dramatic imbalance in risk factor burden wouldbe required to explain the survival difference. ALTITUDE isthe only published study showing improved clinical out-comes associated with RM, although smaller studies suggestimprovements in clinical care56,63 or patient satisfaction andquality of life64 without clear outcome benefits.

Remote monitoring of heart failure status

The majority of ICD and CRT-D devices are implantedin patients with HF, a group at high risk of hospitaliza-tion.65 Weight gain and worsening of HF symptomsmay occur late66 and have poor sensitivity for predi-cting HF hospitalization.60,67 Several device-measuredparameters (Table 2) can predict HF decompensation,allowing RM to facilitate early clinical intervention andpotentially avert hospitalization.14,15,18,68 Intrathoracic

impedance (measured between the RV lead and thedevice generator) varies inversely with lung fluidcontent, such that a decline in intrathoracic impedance

suggests worsening pulmonary congestion.69 Intra-thoracic impedance correlates inversely with pulmonary

capillary wedge pressure,70 RV pressures,71 and na-triuretic peptide levels.72 Declines in intrathoracicimpedance can also occur due to device pocket com-plications, pneumonia, or pleural effusion.69 A dec-line in intrathoracic impedance may occur nearly 2weeks before worsening symptoms and weight gainpreceding a HF exacerbation.70 Declines in intrathoracicimpedance may be associated with worsening atrial73

and ventricular arrhythmias.74 Intrathoracic impedanceand AT demonstrate a bidirectional relationship, inwhich reduced intrathoracic impedance predicts moreAT and increasing AT burden predicts a reductionin intrathoracic impedance.73 The Medtronic OptiVolfeature calculates a positive numeric OptiVol indexto facilitate recognition of a sustained reduction inintrathoracic impedance over time, measured in ohm-days (Figure 5a); a remote or audible alert can besent when a preset threshold is crossed.69 Heartrate variability and patient activity level also declineas much as 2 weeks before HF hospitalization(Figure 5b).68,75,76 The Medtronic Cardiac Compass alertfeature integrates the OptiVol index with patientactivity, nocturnal heart rate, and heart rate variabilityas well as clinical events warranting provider notifica-tion such as increasing AT, reduction in biventricular

pacing, or ICD shocks.77

Shock

A

RV

AS

VS

VP-MT VP-MT

VP-MT VP-MT

VP-MT

VP-MT

[AS] [AS] [AS] [AS] [AS] [AS] [AS]

AS428 223

213430

398

428

428

428

VP-MT428

VP-MT428

VP-MT428

438435

428 428

428415

AS AF

AFAS

VS

AS430 430420 423 433

AS AS ASAS

Figure 4: Electrograms downloaded from Boston Scientific Latitude in right atrium (top), right ventricle (middle) andventricular far-field (bottom), showing 2:1 conducted atrial flutter. AS indicates atrial sensing; AF indicates atrial sensing inatrial fibrillation zone; VP-MT indicates ventricular pacing at maximum tracking rate.



Clinical studies of remote heartfailure monitoring

A standard OptiVol threshold of 60 ohm-days has up to60–76% sensitivity for detecting future HF hospitaliza-tions in CRT-D patients,67,70,78 and many missed HFevents are associated with a subthreshold decline inintrathoracic impedance. Each OptiVol threshold cross-ing per year predicts a 36% increased risk of HFhospitalization.76 The FAST (Fluid Accumulation StatusTrial) study demonstrated that an OptiVol threshold of60 ohm-days had superior sensitivity (76% versus 23%)and fewer false positives than daily weight monitoringfor prediction of HF worsening in 156 CRT-D patients.67

The SENSE-HF study of 501 ICD and CRT-D patientsshowed low sensitivity (42%) and positive predictivevalue (38%) of the standard 60 ohm-day OptiVolthreshold for predicting HF hospitalizations, especially

within the first 6 months after device implantation.79

False-positive OptiVol threshold crossings occur at a rateof 0.25–1.9 events per year, including episodes in whichmedication titration avoided hospitalization and lesserdegrees of decompensation not leading to hospitaliza-tion.67,68,78 The majority of OptiVol threshold crossingsat 60 ohm-days may not be associated with a clinical HF

event.67,68,76,79 Higher OptiVol thresholds of 100–120 ohm-days have been proposed to improve specificity,77,80 andrefinements in the OptiVol algorithm may increasespecificity, reduce false-positive threshold crossing events,

and improve positive predictive value of OptiVol.81

Given these limitations in sensitivity and specificity,intrathoracic impedance and OptiVol cannot be used as asole means of patient evaluation, but may supplementdaily weight monitoring and standard clinical assessmentto facilitate telemonitoring programs.82,83 The observa-tional DECODE (Decompensation Detection)study of 699Boston Scientific CRT-D patients found that adding heartrate variability and lead (not intrathoracic) impedancemonitoring to standard telemonitoring yielded poorsensitivity (,50%) for predicting HF hospitalizations, withfrequent false-positive alerts (two per patient-year).84 Anobservational study of 532 Medtronic CRT patients showedthat intrathoracic impedance monitoring using OptiVolwas associated with a reduced risk of HF hospitalization.68

The observational PARTNERS-HF (Program to Access and

Review Trending Information and Evaluate Correlation toSymptoms in Patients With Heart Failure) study of 694Medtronic CRT-D patients showed that the remote CardiacCompass alert predicted a fivefold increased 1-month riskof HF hospitalization with improved sensitivity over theOptiVol index alone.77 Further research is needed todemonstrate that RM of intrathoracic impedance and otherparameters can prevent HF events, and ongoing rando-mized studies will help to clarify this question.85

Remote hemodynamic monitoring by devices

Dedicated implantable devices can remotely monitorintracardiac hemodynamics in HF patients. Parallel to

declines in intrathoracic impedance,70 intracardiac pres-sures rise before weight gain or symptom worseningpreceding HF decompensation,86 allowing RM of hemo-dynamic parameters to facilitate early intervention.18

Investigational wireless implantable devices can measurepulmonary artery pressure (CardioMEMS Champion)87

or left atrial pressure (St. Jude HeartPOD),86 or estimatepulmonary capillary wedge pressure from RV hemody-namics (Medtronic Chronicle).88 Physician-directed med-ication titration based on device hemodynamic readingsmay prevent HF hospitalizations.86–88 The randomizedCOMPASS-HF trial of 274 advanced HF patients foundthat Chronicle-guided patient management produced a

non-significant 21% reduction in HF events.88 HeartPOD-guided medication titration increased utilization ofevidence-based HF therapies and improved functionalclass.86 The randomized CHAMPION trial of 550 ad-vanced HF patients showed that Champion-guidedpatient management reduced total HF hospitalizationsby 36%.87 Although not available on current ICD andCRT-D devices, attempts are being made to integrateintracardiac pressure monitoring into the next generationof devices.89

Integrating remote monitoring intoclinical practice

A number of potential logistical and technical pitfalls limitthe clinical application of RM.16 Currently available RMsystems generally transmit via telephone landline only, butmobile phone compatibility is available for some models.Transmission failure can occur, but technical success ratesgenerally exceed 90%.9 Patients must be actively involvedin RM for best results, and device manufacturer represen-tatives can often facilitate patient training and enrollment.Remote device alerts may occur in the majority of patientswithin 18 months after implantation,90 and frequent alertsfor non-critical events may add to physician workload.Remote alert management may require individualizedpatient alert settings and/or a nurse-run triage system, anda specific plan for device alert management is recom-

mended,16,62 This approach may reduce the number ofalerts reaching the responsible physician by 90%, leading toa minimal increase in physician workload estimated atapproximately 15 min per week per 100 patients.62,90,91

Table 2: Device parameters predicting heart failuredecompensation

Decreased intrathoracic impedanceElevated OptiVol index

Increased nocturnal heart rateDecreased heart rate variabilityDecreased patient activity levelIncreased atrial tachyarrhythmia burdenDecreased biventricular pacing percentageIncreased right ventricular pacing percentageIncreased intracardiac pressures

Right ventricular pressuresPulmonary artery pressureLeft atrial pressure

Adapted from reference 12.



Physicians could potentially be liable if critical RM data arenot acted on in a timely manner, so direct-to-physicianalerts for critical events may be preferred. False-positive

OptiVol alerts can occur at a rate approaching two perpatient per year,67 but OptiVol monitoring can be success-fully integrated into a multidisciplinary heart failure

Figure 5: (a) Remote monitoring of OptiVol using Medtronic CareLink. Intrathoracic impedance (bottom) declines in mid-June,leading to a OptiVol (top) threshold crossing event in late June, successfully treated by uptitration of diuretics. A similarepisode occurs at the beginning of August, leading to hospitalization. (b) Remote monitoring of patient activity level (top) andheart rate variability (third from top) downloaded from Medtronic CareLink. Patient activity and heart rate variability declinecoincident with decline in intrathoracic impedance and OptiVol threshold crossing.



disease management program without excessive providerburden.83 Integrating RM data into electronic medicalrecords facilitates documentation and coordination ofclinician responses to remote alerts, and this capability isavailable on some systems.12,13,16 Reimbursement can beavailable for RM encounters as often as every 3 months inplace of reimbursement for an office visit; more frequentRM encounters are generally not reimbursed unless achange in therapy occurs. RM may allow a reducedfrequency of scheduled in-office device checks, but itcannot currently replace all in-office device checks orobviate the need for patient–clinician encounters. Whilethe majority of routine device checks do not yield relevantfindings requiring intervention,7,9 unscheduled visits aremuch more likely to require intervention or hospitaliza-tion.8,62 RM provides an opportunity for early triage ofclinically relevant events, allowing prompt in-officefollow-up for significant events and allowing fewercritical alerts to be managed without face-to-face contactunless necessary.

Conclusion

With the proliferation of ICD and CRT-D devices and theexpanding HF population, RM of these devices maybecome increasingly important for patient care. RM canallow early warning of lead malfunction, pacing abnorm-alities, arrhythmias, and HF deterioration to allow timelyintervention. RM may safely allow less frequent in-officedevice checks, facilitating care of patients living far awayfrom their providers and potentially reducing healthcarecosts. The evolving HF monitoring features of ICD andCRT-D devices are an exciting advance that may simplifyclinical management of a complicated and challengingpatient group. We hope that ongoing clinical studies ofRM will clearly document clinical benefits and costsavings to justify the widespread proliferation of thistechnology.

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