Potential role of home monitoring to reduce inappropriate shocks in implantable cardioverter-defibrillator patients due to lead failure Free

Abstract

Aims

Lead dysfunctions in implantable cardioverter-defibrillator (ICD) patients can lead to inappropriate shocks or even complete loss of function of the device. Home monitoring (HM) systems are capable of daily data transmissions regarding the device and the lead integrity as well as information concerning anti-arrhythmic therapies. We therefore analysed the data from the Biotronik HM system whether it enables physicians to react quickly on serious ICD malfunctions and to avoid inappropriate shocks.

Methods and results

Fifty-four patients who had to undergo resurgery due to malfunctions of the ICD lead were included. Eleven of them were on HM interrogating the device every night at 3 am. If any adverse event was detected, a fax alert was sent to the clinic and the patients were asked for in-hospital ICD interrogation. The rate of inappropriate shocks and symptomatic pacemaker inhibition due to oversensing was compared with the 43 patients without remote surveillance. HM sent alert messages in 91% of all incidents. All lead failures became obvious because of oversensing of high frequency artefacts. Only in 18%, changes in the pacing impedance were noticed, in all cases preceded by oversensing. Eighty per cent of the patients were asymptomatic at the first onset of oversensing. Only one patient suffered an inappropriate shock as first manifestation of lead failure. Compared with the patients without HM, inappropriate shocks occurred in 27.3% in the HM group vs. 46.5% ( P = n.s.). This trend gains statistical significance, if the compound endpoint of symptomatic lead failure consisting of inappropriate shocks and symptomatic pacemaker inhibition due to oversensing is focused: 27.3% event in the HM group vs. 53.4% in the group without HM ( P = 0.04). Event messages were despatched in a mean of 54 days after the last ICD interrogation and 56 days before next scheduled visit. Thus, 56 days of reaction time are gained to avoid adverse events.

Conclusion

In 91% of all lead-related ICD complications, the diagnosis could be established correctly by an alert of the HM system. Mostly, the first incident sent was oversensing of artefacts, falsely detected as ventricular fibrillation—the VF zone. The automatic HM surveillance system enables physicians to detect severe lead problems early and to react quickly; thus, it might have a potential to avoid inappropriate shocks due to lead failure and T-wave oversensing.

Introduction

Implantable cardioverter-defibrillator (ICD) leads are complex structures of different conductors for sensing/pacing and high energy delivery with isolation in between. Severe lead dysfunctions in ICD patients are feared to cause inappropriate shocks or even a potential loss of function with possible fatal outcomes as in the case of malignant arrhythmia. A recently published study by Kleemann et al . ¹ showed lead failure rates of 15 and 40% after 5 and 8 years, respectively.

In a large number of patients, lead failure is symptomatic for the delivery of inappropriate shocks. These are fairly uncomfortable for the patients and carry a risk of life-threatening pro-arrhythmic effects. ² Therefore, the early detection of lead failure is crucial in the care of ICD patients. To analyse the system integrity, arising arrhythmias, and symptoms of heart failure, most ICD patients are in close follow-up programmes including quarterly outpatient clinical visits. In a time of restricted resources, the growing number of appointments in the ICD clinics is becoming an increasing challenge.

Home Monitoring™ (HM) (Biotronik GmbH & Co. KG, Berlin, Germany) is a remote surveillance system capable of automatic daily data transmission, focusing on system integrity as well as on information concerning arrhythmias with the resulting therapies, including the transmission of stored intracardiac electrograms (IEGMs). System-related information include sensing amplitudes, lead impedances, and battery capacity. Information regarding the arrhythmias includes a detection counter for SVT, VT, and VF. The reliability of this system regarding data transmission and its clinical impact have been shown in previous reports. ^3–7 The main focus in clinical trials was the impact of HM on medical treatment and on the management of heart failure including atrial fibrillation. ^4–6 In some patients, the alert by HM at an early stage has enabled the detection of a lead failure and the device’s problem could be solved before the patient had to suffer an inappropriate shock. ^{8 , 9}

The rationale of this analysis is to clarify the reliability of HM in a large real-life cohort of patients and to verify the system’s capability to enable physicians to react quickly to lead failure, thus avoiding the occurrence of potentially life-threatening events.

Methods

We analysed all lead revisions that were performed in our institute between January 2002 and December 2007. Patients with HM were put on remote surveillance directly after hospital discharge. These devices are equipped either with the first (Belos ^® or Lexos ^® ), second (Lumos ^® ), or third generation of the HM system (Lumax ^® ).

All devices have an integrated antenna in the header, enabling an automatic and patient-independent, remote, and wireless telemetry to a transmitter device [CardioMessenger™ (CM)]. Data transmission is initiated once a day during night-time. The CM forwards all retrieved data via the GSM (Global System for Mobile Communication) network to the HM Service Centre (HMSC) where all data are decoded, stored, and placed on a password-protected internet platform, to which the physician has access. Apart from this standard daily data transmission, several event triggers may be pre-defined. If any event occurs, an additional message (CardioReport™) is displayed and an event message is sent by fax, SMS, or email directly to the responsible physician. The first generation of devices with HM displays technical details of the ICD (e.g. lead impedances, sensing amplitudes, and battery capacity) on the internet and gives information about occurring arrhythmias (VT, VF, and SVT), the ICD therapy, and the success note. The event triggers used in all patients of the study are categorized into two groups. One group regarding the system integrity [ventricular pacing impedance <250 or >1500 ohm, impedance of last shock <25 or >110 ohm, elective replacement indicator, special implant status (incl. VT/VF detection inactive)] and one group addressing therapy and diagnostics (VT1 detected, VT2 detected, VF detected, SVT detected and 30J shock ineffective).

The second generation additionally transmits a compressed IEGM of the arrhythmic episode up to 7 s before its detection by the device. The third generation is able to display a longer IEGM strip, including the resulting rhythm after therapy delivery (30 s pre-detection and 15 s pre-termination IEGM) and gives detailed information about heart failure parameters and atrial fibrillation.

All patients who underwent resurgery due to failure of the ICD lead or T-wave oversensing were included in the analysis. The study focuses on the correctness of the information sent by the HM system as well as on the value of HM for early detection before inappropriate therapies are delivered. The results are compared with patients with lead failure and the need for operative revision without remote surveillance system ( n = 43).

Statistics were performed using the SPSS 12.0 for Windows software (SPSS Institute, Chicago, IL, USA). Qualitative data are presented as mean value ± SD. They are compared using Student’s t -test or the Mann–Whitney U test if they had no normal distribution. Quantitative data are presented as frequencies and compared by the Pearson χ ² test. P < 0.05 was considered as statistically significant.

Results

From January 2002 to December 2007, operative lead revisions had to be performed in 54 patients. Eleven of them have been equipped with HM and 43 without. The baseline characteristics of the patient groups are shown in Table  1 .

As HM is available since 2001, the group without HM shows a significantly more advanced lead age with a mean of 44.3 ± 27.7 months at the time of resurgery. Nine patients in this group had the ICD implanted abdominally. The devices were manufactured by three different companies: Medtronic ( n = 16; 37.2%), Guidant ( n = 13; 30.2%), and Biotronik ( n = 14; 32.6%). Each ICD has been implanted with a lead manufactured by the device’s company ( n = 37; 86% as passive fixation leads with single coil). According to the device’s age, a lower incidence of primary prophylaxis is found in these patients.

The majority of the home-monitored patients received an ICD for primary prophylaxis according to the rationales of the MADIT II and the SCD-HeFT trials. ^{10 , 11} In four patients, the implantation was carried out because of hypertrophic cardiomyopathy with a positive family history for sudden cardiac death and suspected rhythmogenic syncope (non-sustained VT in Holter recording). In 73.7% ( n = 8) of the patients, a device of the second and third generation of HM was provided (Lumos ^® or Lumax ^® ). In 27.3% ( n = 3) of the patients, the first generation was used (Belos ^® or Lexos ^® ). Dual-chamber ICDs were implanted in five patients. All ventricular leads had passive fixation and were manufactured by Biotronik ^® . Dual coil leads were used in the majority ( n = 9) and two patients had single coil leads.

In the HM group, the incident leading to the operative revision occurred in a mean of 15.4 ± 14.9 months after implantation. Six patients underwent resurgery earlier than 8 months after implantation (3.5 ± 2.2 months) and five patients had late lead malfunctions (29.6 ± 8.9 months).

Table  2 shows a trend regarding the delivery of inappropriate shocks between the two groups. Taken all symptomatic lead failures (inappropriate shock and failure of ventricular pacing due to oversensing) together, significantly less symptomatic lead failures were observed in the HM group ( Figure  1 ).

An overall burden of 228 messages according to the event triggers was reviewed. Related to the system integrity were 19 messages (12.7%) regarding impedance changes in two patients. One hundred and ninety-nine messages (87.3%) were related to therapy and diagnostics, mostly arrhythmia detection.

HM sent alert messages in 91% of all incidents ( Table  3 ). In one patient, no alert message was despatched. This patient attended the ICD clinic 4 weeks after implantation because of ‘hiccups’. During the interrogation, a significant increase in the stimulation threshold was found as well as a lead dislocation on the X-ray comparison. Pacing impedance and sensing amplitudes changed as well but remained within the acceptable range, thus explaining the lack of alert message of the surveillance system.

The most frequently received CardioReport gave information about non-sustained detection of VF in the device’s VF zone ( Figure  2 ). An online IEGM was available in eight patients showing oversensing of high-frequency artefacts in 63.6% ( n = 7) and one (9.1%) T-wave oversensing. During outpatient device interrogation, the stored IEGM confirmed the diagnosis by online IEGM as being correct in all cases (100%). A change in the pacing impedance was observed in only 18.1% ( n = 2). In both cases, oversensing was the first ‘symptom’ detected and the change of pacing impedance followed in a later transmission.

Lead fracture causing oversensing of high-frequency artefacts was the final diagnosis in 72.7% of the patients ( n = 8). Two patients (18.1%) suffered a macro-dislocation of the ICD lead. One, as mentioned, with phrenic nerve stimulation, and the second had a complete loss of sensing and capture occurring due to a Twiddler syndrome. In one patient with hypertrophic cardiomyopathy, T-wave oversensing was detected during physical activity. It led to incorrect tachycardia detection in the device’s VF zone. As it was untreatable, despite a change in the device’s program, lead revision was performed.

Three patients suffered inappropriate shocks. In the first patient, a shock occurred directly with the first onset of oversensing. In the second patient with inappropriate shock, the Twiddler syndrome was responsible for the incident. The first occurrence of this manifestation was a Friday afternoon. As described above, messages are sent during night-times and faxes are evaluated only during office hours, so the problem did not become obvious until Monday morning. The first message showed the detection of non-sustained VF caused by artefacts. It was followed by another message reporting approximately seven more incidents of non-sustained VF detection. The third message, 2 days later, showed sustained oversensing in the VF zone leading to an inappropriate shock. The third patient suffered from T-wave oversensing, which was initially treated with a change of the device’s program. Pre-discharge tests revealed no further oversensing during different exercises. Unfortunately, T-wave oversensing reappeared few days later, leading directly to an inappropriate shock.

All patients with CardioReport ( n = 10) were tried to appoint to the clinic urgently. An urgent interrogation was performed in seven patients (63.6%). One patient called the ICD clinic directly after shock delivery, one patient was in Greece on holiday and refused early interrogation, and one patient’s report was sent out of office hours. All successfully contacted patients were hospitalized immediately, the device deactivated, and surgical revision scheduled. The mean time from the first message received until operative revision was 12 days.

Compared with conventional ICD follow-up with regularly scheduled outpatient clinic visits, HM gives a time benefit by early detection of adverse events. In our patients, the first CardioReport was received with an average of 54 days (53.8 ± 45.5 days) after the last ICD interrogation. As visits are scheduled every 3–4 months (110.5 ± 80.5 days), the next visit was with a mean of 56 days ahead. Thus, a considerably long time to take action was gained.

Implantable cardioverter-defibrillator interrogation of the patient group without HM revealed events of non-sustained oversensing before the lead defect became symptomatic as well (16.2 ± 11.8 days before the event leading to unscheduled interrogation). Unfortunately, complete interrogations were not available from all 23 patients; thus, a direct comparison regarding possible time gain and percentage of non-sustained oversensing of both groups is not possible.

Discussion

Lead failure in ICD patients is well known and feared by patients and physicians as it still occurs frequently, is extremely uncomfortable, and potentially life-threatening. A recently published paper by Kleemann et al . ¹ shows lead survival rates of 85% over 5 years. Inappropriate shocks due to noise oversensing are revealed as the most common presentation of lead failure. A minor role for the detection of lead failure played routinely tested parameters such as impedances, pacing thresholds, and sensing amplitudes. These data underline the impact of inappropriate shock delivery as the earliest and most commonly occurring clinical symptom of lead failure. Apart from the discomfort for the patient, inappropriate shocks may be harmful and even fatal with pro-arrhythmic effects. ² On the other hand, shocks might be ineffective, withheld, or not applicable because of lead fracture, leading to a fatal outcome in the case of malignant arrhythmias.

As demonstrated in case reports ⁹ as well as by the analysis of our patients, lead failure does not cause ICD discharge immediately. In up to 90% of our patients, the occurrence of the first inappropriate shock was preceded by non-sustained noise episodes being wrongly detected as VF. These ‘pre-shock’ detections did precede the inappropriate shocks by hours or even days, and they were brought to the physician’s knowledge by using the HM system with daily data transmission.

Lazarus ⁵ retrospectively evaluated more than 3 000 000 transmissions of pacemakers and defibrillators over a period of 49 months, showing that the vast majority of events is disease and not device related (86%). The author demonstrated the events occurring ∼26 days after the last follow-up visit. Thus, the reaction time gained by HM was 64 days for the ICD patients with quarterly scheduled clinic visits in that study. Our analysis stresses that inappropriate shocks due to lead failure or T-wave oversensing will occur after at least one episode of non-sustained oversensing in most patients. If these ‘warning episodes’ are brought into the physician’s knowledge, quick reactions might be possible to avoid adverse events. In our analysis, the time gain of 54 days achieved by HM is well comparable with the data of Lazarus. On the other hand, the reaction time gained by HM is strictly related to the systems implementation into daily routine. As in most hospitals, we check the internet or the fax for event notes once a day during office hours. As shown, this approach provides the opportunity to gain time for a quick reaction to prevent patients from adverse events.

But even if the physician responsible for the HM system would be located on a 24 h duty or even if event messages were sent via SMS to the doctor’s mobile phone, there would still be a problem in reaching the patients on their phone and to get them to the nearest facilitated hospital. This logistic problem is addressed by the latest generation of HM systems with an optional ‘Call back-lamp’ on the CM. If the patients see the lamp flashing, they are supposed to seek for contact with the ICD clinic quickly. However, the HM system is not conceived as a 24 h online surveillance system but may provide the patients with a higher level of comfort and reassurance.

The Home-ICD trial presented by Brugada in 2006 ⁷ demonstrated the capabilities of HM in ∼240 patients during their routine follow-ups over the first 12 months after implantation and retrospectively evaluated the information gained by HM regarding their sensitivity and specificity. Routine ICD interrogation retrospectively revealed to be ‘true negative’ and provided no additional information to HM. But in 14%, the ICD interrogation revealed HM having been ‘false negative’ indicating that problems have been unmasked by interrogations that were not foreseen by the HM surveillance. Reasons for ‘false-negative’ results were in many cases related to clinical patient management and routine changes of the device’s programming (∼13.6% of all false-negative forecasts). Considering the complete patient care, these important features can clearly not be influenced by HM. With respect to the impact of HM on false-negative forecasts, information about an increase in pacing threshold (17.8%), discovery of lead dislodgement (1.6%), and disregarding of arrhythmias and shock (7.8%) are more important. As shown above, lead dislodgement became obvious in one case because of phrenic nerve stimulation without event message and increase in pacing threshold. This kind of event as well as the threshold increases reported by Brugada might be detectable by HM, if the measured values of an automatic capture control are displayed online as it is implemented in the latest generation of HM. As Home-ICD enrolled patients between 2002 and April 2004, misinterpretations of arrhythmias will surely be reduced by the presentation of online IEGM in the newer ICD generations. With respect to the small number of patients and the retrospective character of this analysis, all IEGMs leading to patient contact and lead revision were correctly interpreted as oversensing of artefacts. The true impact of the online IEGM will be addressed by the ongoing RIONI study. ¹²

The comparison of the HM group with the patients without remote surveillance in this retrospective analysis showed less inappropriate shocks and less symptomatic pacemaker inhibitions. This finding stresses the potential of HM to enable physicians to reduce inappropriate therapies by quick reactions as it has been predicted by Res et al . ¹³

Conclusion

The diagnosis of lead failure could be correctly obtained by HM in 91% of our patients. Ninety per cent of the patients were asymptomatic at the time of the first event report. In 87.5% of the devices capable of online IEGM transmission, misdetection of high-frequency artefacts within the VF zone was the first transmission. In only one patient, the first oversensing was followed by an immediate inappropriate shock. In 30%, an inappropriate shock was unavoidable despite preliminary warnings by the HM system due to logistic issues. In the remaining 70%, reactions could be taken and possibly inappropriate therapies were avoided.

In this retrospective analysis, HM proved to be a reliable tool with a strong potential to decrease reaction time in the case of lead failure. Thus, it may be of value for saving patients from potentially life-threatening malfunctions and inappropriate shocks.

Conflict of interest: none declared.

References