Consensus statement on indications, guidelines for use, and recommendations for follow-up of implantable cardioverter defibrillators. North American Society of Electrophysiology and Pacing

Estimation of Central Venous Pressure by Pacemaker Lead Impedances in Left Ventricular Assist Device Patients

Volume status assessment in left ventricular assist device (LVAD) patients remains challenging. Cardiac resynchronization therapy (CRT) devices are common in LVAD patients, and the impedance across the CRT leads may be associated with hemodynamics and serve as a tool for noninvasive estimation of volume status. Ninety-one sets of measurements including cardiac filling pressures and lead impedances were prospectively obtained during ramp tests from 11 LVAD patients (65.5 ± 9.7 years old; nine male) with CRT devices. Right atrial (RA), right ventricular (RV), and left ventricular (LV) lead impedances were all significantly associated with central venous pressure (CVP) (p < 0.05). We derived the following equation: estimated CVP = 47.90-(0.086 × RA lead impedance) + (0.013 × RV lead impedance)-(0.020 × LV lead impedance). The estimated CVP had a significant correlation (r = 0.795) and good agreement with the measured CVP (mean difference -0.14 ± 1.77 mmHg). Applying the above equation on the validation cohort of twenty-one patients also maintained a strong association with measured CVP (r = 0.705). In conclusion, we have derived a novel equation to estimate CVP using lead impedance measurements. This finding may allow noninvasive monitoring of volume status in LVAD patients.

ISHNE/EHRA expert consensus on remote monitoring of cardiovascular implantable electronic devices (CIEDs)

We are in the midst of a rapidly evolving era of technology-assisted medicine. The field of telemedicine provides the opportunity for highly individualized medical management in a way that has never been possible before. Evolving medical technologies using cardiac implantable devices with capabilities for remote monitoring permit evaluation of multiple parameters of cardiovascular physiology and risk, including cardiac rhythm, device function, blood pressure values, the presence of myocardial ischaemia, and the degree of compensation of congestive heart failure. Cardiac risk, device status, and response to therapies can now be assessed with these electronic systems of detection and reporting. This document reflects the extensive experience from investigators and innovators around the world who are shaping the evolution of this rapidly expanding field, focusing in particular on implantable pacemakers, implantable cardioverter defibrillators, devices for cardiac resynchronization therapy (both with and without defibrillation properties), loop recorders, and hemodynamic monitoring devices. This document covers the basic methodologies, guidelines for their use, experience with existing applications, and the legal and reimbursement aspects associated with their use. To adequately cover this important emerging topic, the International Society for Holter and Noninvasive Electrocardiology and the European Heart Rhythm Association combined their expertise in this field. We hope that the development of this field can contribute to improve care of our cardiovascular patients.

Early detection of adverse events with daily remote monitoring versus quarterly standard follow-up program in patients with CRT-D

BACKGROUND

A relative high rate of clinical and device-related adverse events (AE) is generally reported in patients with implantable defibrillators for cardiac resynchronization therapy (CRT-D). Aim of this study was to compare a daily remote monitoring (RM) to a standard program of in-office visits.

METHODS AND RESULTS

We retrospectively analyzed RM database and hospital files of 99 CRT-D consecutive patients who were visited in the out-patient clinic every 3-4 months; thirty-three patients were in addition controlled remotely with RM (RM group). Kaplan-Meier curves of clinical or device-related AE-free rates were obtained. During a median follow-up of 7 months, clinical AEs were: ventricular and atrial arrhythmias in 14 and 11 patients, low CRT pacing in nine, heart failure, strokes, or death in 15. Device-related AEs were: insufficient pacing/sensing performances in nine patients, lead dislodgement in five. As comparing the RM group with the remaining patients, Kaplan-Meier curves of clinical AEs diverged to significantly different rates: 23.8% (confidence interval [CI] 0.1%-47.5%) in the RM group and 48.7% (21.6-75.7%) in the remaining patients (P = 0.00002), with a hazard ratio of 0.14 (CI 0.06-0.37). Nondivergent Kaplan-Meier curves were obtained for device-related AE-free rates.

CONCLUSION

CRT-D patients followed with quarterly in-office visits without a daily RM system had an 86% higher risk of delayed detection of clinical AEs, during a median follow-up of 7 months.

Design of the evolution of management strategies of heart failure patients with implantable defibrillators (EVOLVO) study to assess the ability of remote monitoring to treat and triage patients more effectively

Background

Heart failure patients with implantable defibrillators (ICD) frequently visit the clinic for routine device monitoring. Moreover, in the case of clinical events, such as ICD shocks or alert notifications for changes in cardiac status or safety issues, they often visit the emergency department or the clinic for an unscheduled visit. These planned and unplanned visits place a great burden on healthcare providers.

Internet-based remote device interrogation systems, which give physicians remote access to patients' data, are being proposed in order to reduce routine and interim visits and to detect and notify alert conditions earlier.

Methods

The EVOLVO study is a prospective, randomized, parallel, unblinded, multicenter clinical trial designed to compare remote ICD management with the current standard of care, in order to assess its ability to treat and triage patients more effectively.

Two-hundred patients implanted with wireless-transmission-enabled ICD will be enrolled and randomized to receive either the Medtronic CareLink^® monitor for remote transmission or the conventional method of in-person evaluations. The purpose of this manuscript is to describe the design of the trial. The results, which are to be presented separately, will characterize healthcare utilizations as a result of ICD follow-up by means of remote monitoring instead of conventional in-person evaluations.

Trial registration

ClinicalTrials.gov: NCT00873899

Assessment of a remote monitoring system for implantable cardioverter defibrillators

We conducted a multicentre study in five Italian hospitals to assess the feasibility of a remote monitoring service for the follow-up of implanted cardiac devices. The system was designed to monitor device performance as well as physiological aspects of the patient's condition. Sixty-seven patients (mean age 64 years) affected by chronic heart failure and with a biventricular implantable cardioverter defibrillator for cardiac re-synchronization therapy (CRT-D) were enrolled for a three-month observation period. A total of 267 device recordings were transmitted through the ordinary telephone network, with a success rate of 99%. The telemonitoring service was more efficient than conventional face-to-face follow-up in terms of the time savings: both for physicians (4.7 minutes versus 15 minutes for remote and conventional monitoring) and for patients (6.6 minutes versus 116.3 minutes). In addition, a total of 23 clinical events occurred during the study, but only two cases required a clinic visit, thus reducing inappropriate hospital admissions. Finally, the service was well accepted by all the users.

Remote monitoring of CRT-ICD: the multicenter Italian CareLink evaluation--ease of use, acceptance, and organizational implications

PURPOSE

The Medtronic CareLink allows remote implantable device follow-up. In this first European experience with CareLink, we assessed the ease of use of the system, the acceptance, and satisfaction of patients and clinicians.

METHODS

Patients implanted with biventricular defibrillators for more than 6 months received the CareLink monitor and were trained to perform home device interrogation and transmission. Patient and clinician experience and preference were evaluated through specific questionnaires.

RESULTS

Sixty-seven patients were enrolled and were able to perform data transmissions during the 3-month study duration. The overall duration of interrogation procedure was 7 +/- 5 minutes, and frequently the procedure did not require the assistance of a caregiver. Patients reported a general preference for remote versus in-clinic follow-up and described a sense of reassurance created by the remote monitoring capability.In the centers, the review procedure was successful; its mean duration was 5 +/- 2 minutes per transmission and the users indicated that the access and navigation of the review website were easy. At the end of the evaluation, the data available for remote review were judged complete and adequate to provide almost the same standard of care as that offered in traditional in-clinic visit. In general, the remote monitoring was seen as a potential tool to improve the clinical management of patients with device.

CONCLUSIONS

The ease of use, satisfaction, and acceptance of the CareLink Network in European clinical practice appears elevated both for patients and for clinicians.

Determination of myocardial energetic output for cardiac rhythm pacing

This research is aimed to the determination of the changes in the cardiac energetic output for three different modes of cardiac rhythm pacing. The clinical investigation of thirteen patients with the permanent dual-chamber pacemaker implantation was carried out. The patients were taken to echocardiography examination conducted by way of three pacing modes (AAI, VVI and DDD). The myocardial energetic parameters—the stroke work index (SWI) and the myocardial oxygen consumption (MVO2) are not directly measurable, however, their values can be determined using the numerical model of the human cardiovascular system. The 24-segment hemodynamical model (pulsating type) of the human cardiovascular system was used for the numerical simulation of the changes of myocardial workload for cardiac rhythm pacing. The model was fitted by well-measurable parameters for each patient. The calculated parameters were compared using the two-tailed Student’s test. The differences of SWI and MVO2 between the modes AAI and VVI and the modes DDD and VVI are statistically significant (P < 0.05). On the other hand, the hemodynamic effects for the stimulation modes DDD and AAI are almost identical, i.e. the differences are statistically insignificant (P > 0.05).

What evidence do we have to replace in-hospital implantable cardioverter defibrillator follow-up?

INTRODUCTION

Due to the increasing number of patients with an implantable cardioverter defibrillator (ICD), new options for ICD patient follow-up management are required.

METHODS

Patients with ICD indication according to the guidelines received an ICD with Home Monitoring technology. The devices enabled the transmission of the relevant episode, therapy, and system integrity data. Patients were followed for 12 months with routine controls every 3 months. The physician analyzed the Home Monitoring data before the routine follow-up visit (FU) and gave a forecast on the necessity of the pending FU, which was compared with the evaluation after the FU. Based on the derived forecast reliability, a patient management scheme was developed and its impact on patient safety was assessed retrospectively.

RESULTS

A total of 271 patients were enrolled (40 f, mean age 62+/-12 years, mean LVEF 39+/-15%, 65% ischemic heart disease, 20% cardiomyopathy) and followed for 339+/-109 days. Of 908 pairs of Home Monitoring data and FU data evaluation, 129 there were false negative results for 92 patients. Safety concerns from false negative forecasts can be minimized with a patient management scheme containing the following elements: 1) never skip the first routine FU; 2) never skip a routine FU for a patient having already shown pacing threshold problems; 3) perform FU following hospitalizations; 4) perform FU following episode detection by the ICD; and 5) perform a routine FU if the patient reports symptoms. The retrospective analysis showed, that if the patients had been managed using this scheme, 503 of 1079 routine FU could have been skipped with only one safety concern, a three month delay in the detection of silent paroxysmal atrial fibrillation in one patient.

CONCLUSIONS

Home Monitoring in ICD therapy over 12 months is feasible. The data transmitted relevantly contribute to a remarkable reduction of follow-up burden and enable the individualization of routine follow-up.

Indications for predismissal testing with arrhythmia-induction in patients receiving an implantable cardioverter defibrillator

Arrhythmia induction during implantation of cardioverter defibrillators (ICD) is a standard procedure. However, controversy exists regarding the need for routine arrhythmia induction before discharge from hospital (pre-hospital discharge (PHD) test). In order to reduce the number of tests we identified risk factors that predict relevant ICD malfunction.

METHODS AND RESULTS

965 patients receiving a first device implantation (n=724) or device/system replacement (n=241) between 1998 and 2004 were analysed. During implantation 176 (18%) complications (intraoperative undersensing of induced arrhythmias, unsuccessful arrhythmia-therapy or low DFT safety margin) occurred. Frequent (>4 times) intraoperative lead repositioning due to low sensing values was present in 44 patients (5%). 9% of the patients with first ICD implantation, 21% with device replacement and 27% with system replacement developed complications during PHD testing with arrhythmia induction. Intraoperative complications, although corrected during implantation, were independent risk factors for malfunction during PHD testing (p<0.05). Additional predictors for malfunction were intraoperative lead repositioning (>4 times) and a history of both VF and VT (p<0.05). Patients without intraoperative complications rarely developed malfunction during PHD testing (3.7% first device, 6.25% system replacement). Only in patients undergoing device replacement was a higher risk for failure (13%) evident. No risk factors could be identified for these subgroups.

CONCLUSION

Routine arrhythmia induction during PHD is recommended in ICD patients with intraoperative complications, although corrected during implantation, as well as frequent intraoperatives lead repositioning. Patients undergoing device/system replacement uncomplicated implantation are not generally at low risk for device failure.

Remote Active Monitoring in Patients With Heart Failure (RAPID-RF): Design and Rationale

BACKGROUND

Heart failure (HF) ambulatory disease management programs appear to offer the greatest benefit to HF patients at highest risk, defined as having New York Heart Association (NYHA) functional Class III or IV symptoms. The Latitude Patient Management System is the first HF management tool to use wireless telemetry present in a cardiac resynchronization therapy defibrillator (CRT-D) device that is linked to remotely collect blood pressure and weight measures, permitting a single transmission reporting device data. Potential advantages of this system include ease of data transmissions, correlation among measures of HF status, arrhythmic events, and device performance. However, the use and ultimate utility of these combined features for patient management are untested.

METHODS AND RESULTS

The Remote Active Monitoring in Patients with Heart Failure (RAPID-RF) study is a multicenter registry that will enroll up to 1000 patients on the Latitude Patient Management System from approximately 100 centers. The primary objective is to examine physician responses to Latitude Active Monitoring data alerts by assessing alert-related medical interventions. Minimum follow-up will be 3 months after implant with a maximum follow-up time of 24 months after implant.

CONCLUSIONS

The RAPID-RF study will provide important preliminary data on how remotely collected HF and arrhythmic surveillance data alter the management of HF patients with CRT-D devices.

Clinical Experience with Tiered Atrial Therapies and Atrial Arrhythmia Prevention Algorithms in a Dual Chamber Cardioverter Defibrillator

INTRODUCTION

The acceptance of atrial arrhythmia features in implantable cardioverter defibrillators (ICDs) will depend on their ability to appropriately discriminate atrial tachyarrhythmias/atrial fibrillation (AT/AF). This study tested the effectiveness of an atrial/ventricular ICD with advanced atrial detection and new algorithms designed to prevent atrial arrhythmias.

METHODS AND RESULTS

Ninety-five patients were implanted with a dual chamber ICD (Model 1900, Guidant Corporation, MN, USA) at 25 US centers. Ten patients received a coronary sinus (CS) lead allowing a defibrillation vector for AT/AF cardioversion. Follow-up was 12.2 months. The addition of new atrial features designed for detection, discrimination, and prevention of AT/AF had no adverse effect upon detection of induced ventricular fibrillation (VF) (mean detection time with new features ON was 2.22 seconds vs 2.19 seconds with features OFF). A total of 100% of the induced and spontaneous ventricular and atrial arrhythmias receiving shock therapy were reviewed as appropriate detection. Atrial shock conversion efficacy for spontaneous and induced AT/AF episodes was 83% and 96%, respectively (144 spontaneous, 162 induced episodes). A 3-month randomized crossover trial of atrial preventative pacing features did not result in adverse effects, but there was no clinical efficacy for prevention of AT/AF.

CONCLUSION

Enhanced atrial detection and discrimination features combined with tiered atrial therapies did not adversely impact the ability of the ICD (Model 1900) to appropriately detect and treat ventricular tachyarrhythmias.

IEGM-online based evaluation of implantable cardioverter defibrillator therapy appropriateness

Appropriate and inappropriate therapies of implantable cardioverter defibrillators have a major impact on morbidity and quality of life in ICD recipients. Intracardiac electrograms (IEGMs) stored in the ICD have been shown to be essential for differentiating appropriate and inappropriate ICD therapies. The recently introduced third generation of ICD Home Monitoring offers remotely transmitted IEGMs (IEGM-online). Hence, the appropriateness of ICD therapies might be remotely assessed. Validation of these electrograms is currently being performed in the RIONI study. A total of 210 episodes will be collected by about 40 European clinical centers. The study primarily investigates whether the IEGM-online based evaluation of the appropriateness of the ICD's therapeutic decision following a tachyarrhythmia episode detection is equivalent to the evaluation based on the complete ICD episode holter. The evaluation is independently performed by an expert board of three experienced ICD investigators. The equivalence of the two methods is accepted if the conclusions deviate for less than 10% of all evaluated IEGMs. Secondary endpoints investigate the IEGM-online usefulness in more detail. The conclusion of the study is expected by mid of 2007. RIONI has successfully been started for proving the reliability of IEGM-online. The expected results will significantly influence the efficacy of Home Monitoring based patient management.

The RIONI study rationale and design: validation of the first stored electrograms transmitted via home monitoring in patients with implantable defibrillators

Appropriate and inappropriate therapies of implantable cardioverter defibrillators (ICDs) have a major impact on morbidity and quality of life in ICD recipients. The recently introduced home monitoring of ICD devices is a promising new technique which remotely offers information about the status of the system. Stored intracardiac electrograms (IEGMs), which are essential for correct classification of appropriate and inappropriate ICD discharges, have until now not been available with ICD home monitoring on a day-by-day basis because of limitations of transferable data. We demonstrate the first compressed IEGMs daily transferable via home monitoring (IEGM-online). Validation of these electrograms will be performed in the Reliability of IEGM-Online Interpretation (RIONI) study. A total of 210 episodes of stored IEGMs will be collected by at least 12 European centres. The primary endpoint of this study is to investigate whether the IEGM-online based evaluation of the appropriateness of the ICDs therapeutic decision following episode detection is equivalent to the evaluation based on the complete ICD episode Holter extracted from the IEGM stored. The evaluation is independently done by an expert board of three experienced ICD investigators. The equivalence of the two methods is accepted if the evaluations yield a different conclusion for <10% of all evaluated IEGMs. The conclusion of the study is expected at the beginning of 2007. If RIONI successfully validates IEGMs transmitted via home monitoring, a strong basis for the use of this promising technique will be established.

[Efficiency potential in the pacemaker/implantable cardioverter defibrillator outpatient clinic]

The aim of the present study was to elucidate whether the duration of a technical follow-up (FU) of a pacemaker (PM)/implantable cardioverter defibrillator (ICD) has an impact on cost-effectiveness in the outpatient clinic. We determined the time required for a complete FU of devices from three different manufacturers. In 130 patients (70 VVI/DDD-PM, 60 VVI/DDD-ICD) with either a PM (Phylos, Chorum/Talent, Kappa, EnPulse) or an ICD (Belos, Alto or GEM) the time was recorded for a complete FU including determination of lead impedance, sensing and pacing threshold. The time for activation of individual menue buttons was excluded. On the basis of time required for FU, cost-units (CU) were calculated for 2000 FU/year and for a presumed device longevity (PM 7 years, ICD 5 years). For VVI-PM, the duration of FU was almost identical for devices from different manufacturers (105+/-11 s to 125+/-8 s; p=n.s.). However, analysis of DDD-PM revealed marked differences (140+/-25 s vs 282+/-23 s, p<0.05). Time for FU of ICDs varied between 108+/-5 s and 207+/-21 s (p<0.05) in VVI-ICDs and between 129+/-8 ms and 225+/-23 s (p<0.05) in DDD-ICDs. The total savings could be 55 000 CU in VVI- and 53 333 CU in DDD-ICDs. For full automatic DDD-pacemakers (EnPulse) time for FU could be reduced to 58+/-3 s (p<0.05). Differences in FU times were caused by problems with telemetry, delay during booting of the programmer, interrogation at the beginning and at the end of FU and for sensing tests. Improving not only programmers and devices but also test automaticity could significantly increase cost-efficiency in the outpatient clinic.

Implantable cardioverter defibrillator (ICD) in children

BACKGROUND

Implantable cardioverter defibrillators (ICD) proved to be effective in the prevention of sudden cardiac death in adults. In children, the experience of ICD therapy is limited. This retrospective study was undertaken to review our experience with ICD implantation in children with special consideration of psychosocial impact of this therapy.

METHODS AND RESULTS

Sixteen children (f:5, m:11, median age 12.2 years, range 4-15.9 years) received an ICD. Eleven patients had survived sudden cardiac death with documented ventricular fibrillation (VF) and five patients had sustained ventricular tachycardia (VT) with hemodynamic significance. The underlying heart disease was congenital in 5, hypertrophic cardiomyopathy in 2, myocarditis in 2 and primary electrical in 7 patients. All leads were implanted transvenously. Mean follow up was 43.1 months (range 1-105 months). All patients are alive. In 7 patients, a total of 387 sustained VT episodes were detected by the ICD. At follow-up, 10 inappropriate shocks were delivered in four patients. One early and six late lead revisions were done in seven patients. 12/16 (75%) patients had concomitant antiarrhythmic drug therapy. About half of the adolescents showed signs of depression and/or anxiety.

CONCLUSION

ICD therapy via transvenous access for prevention of sudden cardiac death is feasible and effective even in small children. However, the occurrence of lead complications is significant. Since about half of the adolescents showed signs of depression and/or anxiety, professional psychological surveillance should be considered in these patients.

A Latin American registry of implantable cardioverter defibrillators: the ICD-LABOR study

OBJECTIVE

Despite the progress that has been reached in emergency medical systems and resuscitation, sudden cardiac death (SCD) continues to be the major cause of the death, and remains a significant public health problem. In this publication we are reporting our Latin American experience in the secondary prevention of SCD, by means of an ongoing registry involving seven Latin American countries and 770 patients.

METHODS

Every individual within the present registry to date has presented with antecedents of aborted sudden death or cardiac arrest due to ventricular tachycardia or ventricular fibrillation. Patients included have fulfilled the Class I indication for implantable cardioverter defibrillator (ICD) and they were implanted with a Biotronik ICD (all models). The study was not sponsored by Biotronik, nor did they have access to the data. A specific protocol was designed for implantation and follow-up of patients. The database was completely registered through the Internet and a personal password was assigned to each group of investigators. The primary end point was death from all causes. Secondary end points were SCD and death due to congestive heart failure (CHF).

RESULTS

The etiology of cardiac disease was found to be predominantly coronary artery disease (CAD) 39.7% (306 patients), followed by Chagas disease (ChD), 26.1% (201 patients), and idiopathic dilated cardiomyopathy (DCM), 17% (131 patients). Any remaining pathologies were included as miscellaneous 13.2% (101 patients). In 31 patients (4%) the etiology was unknown. The age did not differ within the principal pathologies, but was significantly older than the miscellaneous group (62.0 +/- 11.3 years vs 48.2 +/- 18.9 years, P < 0.0001). The follow-up period was 27 +/- 25 months (1-113 months) for the whole group. The mortality in functional classes I-II was significantly lower than mortality for functional classes III-IV (relative risk 1.46, CI 95%, P < 0.0001). Mean left ventricular ejection fraction (LVEF) for the whole group was 37.7 +/- 14.3%. Male LVEF was 36.1 +/- 14.1% and female LVEF was 42.2 +/- 13.8% P < 0.0001. During the follow-up period, 130 deaths were reported (global mortality 16.9 +/- 9.7%), out of which 84 (64.6%) were attributed to cardiac causes (10.9 +/- 5.1% of the total population). The annual adjusted cardiac mortality was 5.2 +/- 1.72% (range 3.5-7.0%). Among cardiac deaths the most common cause was progressive heart failure, 48 patients (57%) including 3 patients with pulmonary embolism. The second main cause of cardiac death was SCD, 36 patients (43%), including 4 patients with electrical storm and 3 patients with electromechanical dissociation after multiple shock therapy treatments.

CONCLUSIONS

Despite the differences in terms of pathologies between the ICD-LABOR (Latin American bioelectronic ongoing registry) and randomized ICD trials, a parallel evolution in all cause mortality and cardiac mortality was observed. Independent risk factors for mortality included age >70 years, male gender, NYHA III/IV, and ejection fraction <0.30. The etiology of heart disease (Chagas vs Coronary Disease) was not found to be a risk factor.

Remote Monitoring of Implantable Cardioverter Defibrillators:. A Prospective Analysis

A prospective study evaluating the functionality and ease of use of the Medtronic CareLink Network, "CareLink," was conducted at ten investigational sites. This internet-based remote monitoring service allows clinicians to remotely manage their patients' implantable cardioverter defibrillators (ICDs) and chronic diseases. The network is comprised of a patient monitor, a secure server, and clinician and patient websites. Under clinician direction, patients interrogated their ICDs at home, and transmitted data to secure servers via a standard telephone line. Comprehensive device data and a 10-second presenting rhythm electrogram were captured by the monitor and available for access and review on the clinician website. The information could also be printed using a standard desktop computer with internet access. During this study, patients were asked to transmit device data twice, at least 7 days apart, as scheduled by the clinic. Monitor functionality was assessed, and ease of using the system components was evaluated via questionnaires completed by patients and clinicians following each data transmission and review. Fifty-nine patients (64 +/- 14 years, range 22-85 years) completed 119 transmissions with only 14 calls to the study support center. Clinician review of data transmissions revealed several clinically significant findings, including silent AF discovery, assessment of antiarrhythmic drug efficacy in a previously diagnosed AF patient, previously unobserved atrial undersensing, and ventricular tachycardia. ICD patients found the monitor easy to use. Clinicians were pleased with the performance of the network and the quality of the web-accessed data, and found it comparable to an in-office device interrogation. CareLink is a practical tool for routine device management and may allow timely identification of clinically important issues.

Apparent protective effect of increased left ventricular wall thickness in an ICD population

BACKGROUND

Expanding indications for the implantable cardioverter defibrillator (ICD) call for further enhancement of patient selection for optimization of use. Because a subgroup of patients who receive ICDs may not receive therapies, we sought to identify clinical predictors of therapy-free survival in ICD patients.

METHODS

We performed an analysis of a single-center, 13-year ICD implantation experience (1990-2002). The association between therapy-free survival and several clinical variables was evaluated.

RESULTS

From a total of 562 patients included in the database, 98 patients (17%) received no shock therapies or antitachycardia pacing (group A). When compared with a randomly selected sample of 131 patients who did receive ICD therapies (group B), there were no significant differences in age, gender, frequency of coronary artery disease, or extent of left ventricular (LV) dysfunction. However, left ventricular hypertrophy (LVH; increased wall thickness by echocardiography) was significantly more common in group A versus group B (30% versus 18%; Pearson's chi-square=4.69, P=.03). The odds of patients in group A having LVH were 1.98 times higher versus group B (95% confidence interval for odds ratio: 1.06-3.71). Comparisons of calculated mean LV mass between the 2 groups were not significantly different (group A 283+/-112 gm versus group B 271+/-108, P=.58). The overall mortality rate was 17% in group A and 22% in group B (P=.29).

CONCLUSIONS

Increased LV wall thickness was a significant, independent predictor of therapy-free survival in this ICD population. Because LV mass was unchanged, this finding may reflect the importance of LV dilation and wall thinning (ie, eccentric remodeling) as a risk factor for recurrent ventricular arrhythmia in ICD patients.

The effects of age on quality of life in implantable cardioverter defibrillator recipients

BACKGROUND

The implantable cardioverter defibrillator shows superiority over conventional pharmacological therapy. The implantable cardioverter defibrillator has been implanted with increasing frequency in patients who are either at risk for or have experienced a life-threatening dysrhythmia. Implantable cardioverter defibrillator recipients experience a myriad of physical, emotional and social adjustments, with little being known about the impact of age on trajectory. AIMS, OBJECTIVES AND DESIGN: Therefore the purpose of the study is to examine the effects of age on health status, quality of life, and mood states of implantable cardioverter defibrillator recipients during the first year after implantation using a repeated measures design.

METHODS

A comparison of implantable cardioverter defibrillator patients' scores with other samples, both ill and well, are discussed to see how the two implantable cardioverter defibrillator age groups compare on the various measures. Human subjects approval was obtained from the institutional review board.

RESULTS

Seventy subjects, 51 males and 19 females, were recruited. There were 31 subjects between the ages of 21 and 62 years, mean age of 51 years, that comprised the younger age group, and 39 subjects between the ages of 67 and 84 years, mean age of 74 years, that comprised the older age group. Each subject completed the Medical Outcomes SF-36, the Ferrans and Powers Quality of Life Index, and the Profile of Moods States at time of implantable cardioverter defibrillator implantation, and 6 and 12 months later.

CONCLUSIONS

The older age group was as expected less physically active, less satisfied with their physical functioning, and had slightly more anxiety at 6 and 12 months than the younger counterparts. The younger implantable cardioverter defibrillator recipients demonstrated some improvements over time in the perception of their physical adjustment and anxiety.

RELEVANCE TO CLINICAL PRACTICE

Comparison of the SF-36 with other populations with or without a medical condition revealed scores below norms in physical health for both groups, and only slightly higher than patients with heart failure for the older group.

Analysis of electrocardiograms for subcutaneous monitors

We are developing a subcutaneous cardiac arrest monitor and alarm with electrodes that have spacing of a few centimeters. We hypothesize that closely spaced bipolar electrodes that provide QRS amplitudes of a millivolt or more in sinus rhythm (SR) will not provide similar amplitudes during ventricular tachyarrhythmia (VT/VF), and that an orthogonal set of electrode pairs in diagonal is necessary to produce signals of sufficient amplitude in order to distinguish these rhythms.

METHODS

Forty patients were studied during ICD implantation in the clinical electrophysiology laboratory. A square array of 9 electrodes with 4- to 10-cm spacing between adjacent electrodes was placed on the patient's anterior chest over the left heart. The center electrode in the left most column is located in the 5th intercostal space at the left sternal border. Eight-channel recordings were made in SR and during induced VT/VF from the 8 peripheral electrodes referenced to the central member of the array. From these recordings all 20 bipolar ECGs of adjacent (including diagonally adjacent) electrodes were constructed algebraically. QRS peak-peak amplitudes in SR and VT/VF were measured in each bipolar lead and in the spatial vector formed by summing the squares of each adjacent and orthogonal pair of these leads.

RESULTS

Electrode pairs that yielded optimal ECG amplitudes in SR were not always the pairs that yielded optimal amplitudes in VT/VF. But in every patient two orthogonal pairs could be found whose QRS vector amplitude is sufficient in both SR and VT/VF to separate the rhythms.

CONCLUSIONS

A patient-defined set of bipolar electrode pairs is suitable for automatic separation of SR and VT/VF by rate in subcutaneous ambulatory monitoring.

Are electrophysiological studies needed prior to defibrillator implantation?

At present, patients with documented sustained VT or resuscitated cardiac arrest (CA) are treated with ICDs. The aim of this study was to retrospectively evaluate if a routine electrophysiological study should be recommended prior to ICD implantation. In 462 patients referred for ICD implantation because of supposedly documented VT (n = 223) or CA (n = 239), electrophysiological study was routinely performed. In 48% of the patients with CA, sustained VT or VF was inducible. Electrophysiological study suggested conduction abnormalities (n = 11) or supraventricular tachyarrhythmias (n = 3) in conjunction with severely impaired left ventricular function to have been the most likely cause of CA in 14 (5.9%) of 239 patients. Likewise, sustained VT was only inducible in 48% of patients with supposedly documented VT. Of these inducible VTs, nine were diagnosed as right ventricular outflow tract tachycardia or as bundle branch reentry tachycardia. Supraventricular tachyarrhythmias judged to represent the clinical event were the only inducible arrhythmia in 35 (16%) patients (AV nodal reentrant tachycardia [n = 7], AV reentry tachycardia [n = 4], atrial flutter [n = 19], and atrial tachycardia [n = 5]). Based on findings from the electrophysiological study, ICD implantation was withheld in 14 (5.9%) of 239 patients with CA and in 44 (19.7%) of 223 patients with supposedly documented VT. During electrophysiological study, VT or VF was only reproducible in about 50% of patients with supposedly documented VT or CA. Electrophysiological study revealed other, potentially curable causes for CA or supposedly documented VT in 12.6% (58/462) of all patients, indicating that ICD implantation can potentially be avoided or at least postponed in some of these patients. Based on these retrospective data, routine electrophysiological study prior to ICD implantation seems to be advisable.