Clinical Results

Clinical data has been accumulated to characterize utility of the Telemetry@Home system. In the Fall of 1997, a multi-center clinical trial was instituted by the Cardiothoracic Service Line, the Department of Thoracic & Cardiovascular Surgery, St Francis Hospital; the Cardiac Arrhythmia Center, Department of Cardiovascular Disease, Washington Hospital Center, and Cardiac Telecom Corporation. The two center’s IRB’s and the Food and Drug Administration (FDA) approved a clinical trial to compare the usability of the HEARTLink II Telemetry@Home Monitoring System to standard event recorders. Patient outcomes were also tracked at one site, St. Francis Hospital, and are reported first, while the usability data is presented under the section Comparison to Event Recorders.

During a seven month period from November of 1997, through June 1998, a total of sixteen patients successfully completed the clinical trial. Sixteen patients were discharged to home on either an event recorder or the HEARTLink II device, and then subsequently switched to the other device. Patients were randomized utilizing the last digit of their social security number to determine what device would be used first.

100% of the patient population on the Cardiothoracic Service Line has their outcomes reviewed, analyzed, and measured via a Variance Monitoring Methodology (VMD). Variance Monitoring measures demographic data, resource utilization, and outcome measures for all patients undergoing surgical interventions. Currently, this monitoring methodology separates patients into major clinical pathway categories such as patients undergoing open heart surgery, thoracic surgery procedures, major vascular and peripheral vascular procedures. The historical data gathered by VMD can be used as a control group to compare outcomes of patients using HEARTLink II and those not.

The following charts compare demographic and outcome information for the HEARTLink II patient population and the general Variance Monitoring Data (VMD) patient population. The first tables indicate the two groups being approximately the same age with the HEARTLink II patients only slightly older.

 Table 1. - Gender/Age Data

The mean number of grafts per case for those patients on the HEARTLink II study was 3.73. The mean number of grafts for each of the patients during the Clinical Trial for the VMD patient population graft/patient ranged from 3.05 - 3.72. Graft numbers are similar in the two populations of patients.

Table 2. Mean # of Grafts/Case

The following data represents the mean length of stay for patients undergoing open heart surgery. Unlike the HEARTLink II Patient Protocol, where, only coronary artery bypass patients were included, the Variance Monitoring Data (VMD) includes patients undergoing coronary artery bypass procedures, valve procedures, combined procedures, emergent procedures, redo procedures, etc... The VMD does exclude outlier patients (defined as LOS > 32 days). The length of stay for the HEARTLink II patients was between 2 to 3 days less than the patients tracked by VMD.

Table 3. Length of Stay Data

The fifth postoperative day (5POD) represents the targeted day of discharge for the Cardiothoracic Service Line Open Heart Surgery Clinical Pathway patients. The overall postoperative LOS for the HEARTLink II patients was 4.87 days which represents a 100% compliance with the Clinical Pathway. The range of LOS was discharge on the 3rd postoperative day to as late at the 7th post operative day of discharge. The rates of compliance per month for all patients monitored through VMD were as shown in the VMD Data Table, but all were less than 100%.

Table 4. Compliance with 5th Operative Day Discharge (5POD)

Comparison to Event Recorders:

Along with the clinical outcome data, during the multi-center trial, data to support a 510(k) submission for the HEARTLink II system and to compare it to currently marketed cardiac Event Recorders was also gathered. These studies were to test the effect of home environmental factors on the HEARTLink II’s ability to monitor patients’ heart signal data and the utilization of commercial communications networks to transmit this data to a central monitoring system. The accuracy of transmitted data (whether or not the event is transmitted and received correctly), had been previously verified in laboratory testing and in the hospital environment.

Two areas of comparison were to be evaluated. The first area tested the usability of the HEARTLink II system. The second area determined the equivalence of the HEARTLink II system’s and the Event Recorder’s transmitted data. These areas formulated two hypotheses that would be tested in both clinical and healthy volunteer trials.

To evaluate patient usability, the same patients as in the clinical study were utilized. Each patient was randomly assigned to one of two groups. The first group consisted of patients who wore the HEARTLink II system at the start of the study (Trial 1). The second group consisted of patients that wore the Event Recorder at the start of the study (Trial 1). After three days, the patients were “crossed over” to the alternate monitoring system for an additional three days (Trial 2). At the end of each three-day segment, it was noted if the patient was able to complete that particular segment of the study.

A total of 19 patients were to be remotely monitored in their home environments. The outcome to be measured will be the number of patients that complete each segment of the study with either the HEARTLink II system or the Event Recorder. Each study segment, for every patient, is represented by either a “Yes” or a “No”.

Of the 19 patients that were included in the data analysis, 94 percent (17 patients) were able to complete the study with the HEARTLink II system. One patient (Patient #9) was unable to complete the HEARTLink II system study segment because the patient’s home was located in an area that required the hospital Central Station to dial a newly assigned area code (724 instead of 412) to complete the long distance phone call. This fact had not been determined until the patient was disconnected from the device and the study segment classified as a “No” (unable to complete study). The HEARTLink II system, however, responded with an appropriate error message that the patient was not being monitored. To correct future occurrences of this operator error, all hospital personnel were trained on how to successfully detect and correct this situation. Another patient, who was initially connected to the HEARTLink II, developed atrial fibrillation after less than an hour and was subsequently hospitalized. The HEARTLink II System correctly detected this arrhythmia from this patient and transmitted the alarm and the ECG data to the central station. Arrangements were made to have this patient treated at a local hospital after the patient’s physician was notified of this arrhythmia.

Of the 19 included patients, 82 percent (15 patients) were able to complete the study with the Event Recorder system. One patient (Patient #3) was sent home with a defective Event Recorder. Another patient (Patient #10) was unsuccessful at downloading the data from the event recorder over the phone in spite of the verbal instructions given to the patient by the Central Monitoring station staff. Only a total of three events were properly initiated and transmitted by this patient to the Event Recorder Central Monitoring station. The third patient (Patient #15) appeared to be unable to understand the concept of the operation and download procedures of the Event Recorder. This patient’s device was also suspected of having an intermittent problem that affected the patient’s ability to utilize it. The fourth patient never reached the event recorder phase, having been hospitalized.

The data presented above suggest that the success rate using an Event Recorder and HEARTLink II systems does not significantly differ. The number of patients who completed the study segment using an Event Recorder is comparable to the number of patients who completed the study segment using HEARTLink II. Successful completion of the study with either the Event Recorder or HEARTLink II systems required the patient to perform all tasks associated with the maintenance of recording electrodes, battery changes, activation of events and in the case of the Event Recorder, successfully but manually downloading the data to the central monitoring facility over the telephone. Patients using the HEARTLink II system were equally as successful at the performance of all these associated tasks as with the Event Recorder system.

Cardiac Telecom also performs an Event Recorder service and has compared data regarding symptomatic and asymptomatic transmissions from event recorders to Telemetry@Home. In all these cases Cardiac Telecom has actually conducted the service.

Table 5. Results of Cardiac Telecom’s Event Recorder Service

The results of this tabulation based on 59 patients show that the vast majority of transmissions made by the patients (117 out of a total 177) were NSR and yet these are “symptomatic” in the sense that the patient “felt” something before initiating the transmission.

In addition, we have pulled a subset of patients that were on Cardiac Telecom’s Telemetry@Home service this year and analyzed the results of the transmissions received from those on-service patients. It is interesting to note that in contrast to the results of transmissions received from event recorders, the vast majority of the true events detected and transmitted to the lab were asymptomatic (greater than 95%). That is the events that triggered a transmission to our lab at the time of transmission were not felt or reported as symptomatic by the patients. Note that the patients themselves were not asymptomatic, e.g. they were on service for a specific complaint such as Syncope, but rather the events were not felt by the patients. Therefore it is believed that none of these transmitted events would have been transmitted to a lab had the patient been using an event recorder. Furthermore, it is believed that these asymptomatic events contributed to the patient being symptomatic.

Several patient alarms were transmitted to the lab in this subset when the patient believed they were experiencing cardiac symptoms. In every case those specific patient activated transmissions on our Telemetry@Home service showed the patient in normal sinus rhythm.

Discussion

The clinical data suggests that the length of stay may be reduced in post-bypass patients with the HEARTLink II system and that the desired clinical pathway for that patient is more likely to be met. This may be due to the attending physician’s increased confidence that post-discharge patient problems are more likely to be identified and dealt with quickly as illustrated by the following clinical vignette:

 Patient # 1, 66 year old male underwent a coronary artery bypass times three, in November of 1997. He was discharged to home on his fifth postoperative day. which complied with the Clinical Pathway goals. His postoperative course was uneventful. He was discharged to home on the HEARTLink II device.

Routine review of trended HEARTLink II strips indicated an excessive number of PAC’s. Viewed by themselves they did not warrant an alarm situation, however, when an eight hour trend was reviewed it was believed the patient was on the verge of converting to atrial fibrillation. The cardiologist was contacted and oral anti-arrhythmic medications were initiated. The patient was monitored 48 additional hours during which time the PAC’s stopped. Both the nurse and cardiologist believed this patient would have converted to atrial fibrillation requiring a higher level of intervention if the preventive action had not occurred.

Patients should find it at least as easy if not easier to use than an event recorder. For example some patients, particularly several with dementia, are unable to use conventional event recorders because of the complexity involved but can use Telemetry@Home since it is fully automatic. Another patient, a deaf mute, was also unable to use an event recorder since usage involves responding to beeps and talking on the phone.

Additionally, there may be value in detecting asymptomatic events in otherwise symptomatic patients. ECG rhythm abnormalities may not correlate well with actual perception of symptoms, resulting in many Event Recorder transmissions of normal sinus rhythm at least for those patients placed on an Event Recorder service at Cardiac Telecom. A difficult to obtain symptom-rhythm correlation has been reported during spontaneous syncope .

The table below enumerates the differences among the various technologies, HEARTLink II, Holter Monitors, and Looping event recorders and should aid the clinician in choosing a suitable modality for his patient.

1 - if symptomatic & responsive near time of arrhythmia
2 - in seven day increments/script

 Table 6. Comparison of Several Device Technologies

Uses

Telemetry@Home has been very successfully used with post-surgical coronary artery bypass graft (CABG) patients who have experienced post-procedure periods of atrial fibrillation, often asymptomatic but potentially harmful. Timely identification allows interventions preventing greatly increasing risk of stroke. Patients are usually on the system from 5 to 10 days and though they must stay home to be monitored this is not a serious inconvenience for these patients. The patients may leave the home from time to time for short periods (e.g. for a doctor’s appointment), but will not be monitored once they go beyond a maximum 500 foot range.

The system has also been used very successfully with difficult to diagnose arrhythmias or when the patient is undergoing either drug titration at home or there has been a change in medication with potential pro-arrhythmic side effects where the nearest competing technologies, event recorders and Holter Monitors, could not be used or have been used with negative yields. Many patients have had failed Holters, but arrhythmias were still suspected, which Telemetry@Home often quickly identified. These patients clearly benefited from the advantages of the system. An additional advantage is the system’s ability to identify artifact on call in, allowing the operator to advise the patient to re-apply electrodes. On a conventional Holter it is possible to record an entire tape of artifact should there be an electrode problem, the problem being identified only after the fact while the tape is being scanned.

Telemetry@Home gives the physician the data required, when it occurs (real-time) to allow for timely intervention. Some case study data suggests that Telemetry@Home is keeping patients out of the emergency room and is helping to reduce readmissions for lengthy stays, which also accounts for significant cost savings. The service is also proving efficacious in assisting physicians to determine quickly the need for pacemakers where that device is indicated. The system has also helped intervene very quickly when medical attention has been required and has assisted in saving several patient lives. It is of interest to note that several patients have only been on service for a matter of hours when a timely and potentially lifesaving intervention has been facilitated or initiated by the Telemetry@Home service.