Heart-related diseases and disorders are abundant in the western world. Around 500,000 cases of sudden cardiac death, over three million patients with atrial fibrillation and about 600,000 heart attacks are a significant factor in the cost structure of the European healthcare system every year.
The Need for a Cardiological Home Monitoring System
Effective therapy in
this area is usually no longer the problem. Defibrillators and sufficient
medication have had revolutionary success in saving the lives of patients with
heart disorders. Crucially, the biggest issue is the lack of diagnosis. So far,
the standard is that even high risk patients only visit their physician every
six months for a check-up. If the health situation worsens between visits, problems
will not be identified until the symptoms become acute. Due to a prevalent fear
of hospitals, many patients wait until their health condition develops into an
unbearable situation. It is at this point that they would call the emergency
service and be brought to the hospital, normally needing to remain there for
days before becoming healthy enough to return home, thus costing the healthcare
system a great deal.
Different programmes to
circumvent these problems have been carried out with patients for the first
symptoms of heart-related diseases. These programmes have proved to be
successful. However, for more effective prevention, the best solution would be
a continuous monitoring of the relevant vital parameters, especially the
electrocardiogram (ECG). The monitoring in hospitals is very effective but also
very expensive. Furthermore, most patients prefer to remain at home in their
place of comfort, where they have the support of their family and friends. In
contrast to the often very sterile atmosphere in hospitals, from a
psychological point of view, the home is a much better surrounding for treating
patients. Obviously, it is also much more cost effective if patients do not
have to stay in a hospital or can leave the hospital as early as possible. To
give the necessary medical security at home, a monitoring system for the
homecare area must be the goal.
There have been many
attempts to find a practical and efficient way to monitor patients with
heart-related problems at home. Recent approaches rely on the interaction of
the patient. In the event that symptoms arise, the patient has to apply an ECG
recorder or, as a minimum precaution, has to activate a recorder that he is
wearing. Afterwards, the ECG is transmitted via the telephone line or a mobile
phone. Some downsides are that often this procedure is not possible because the
patient either does not feel any symptoms or it is an acute situation where he
is unconscious within seconds and therefore unable to activate the device.
The Proposed System
An innovative system has
been developed which overcomes these disadvantages. The central part of this
monitoring system is a mobile sensor, an ECG chest strap, which is worn by the patient
and analyses the patient's ECG. When an event is detected, an automatic wireless
connection is activated to a relay station, which receives the message from the
ECG chest strap and sends it via the mobile telephone network to a central
internet-based Electronic Health Record (EHR). This EHR automatically informs a
care giver via fax. The care giver logs in the EHR, checks what happened and
initiates the appropriate help.
In this scenario, the
patient is monitored with a small and light ECG chest strap, which is worn in a
way similar to the pulse watches familiar from the field of sports. The chest
strap contains an integrated ECG sensor, which continuously analyses the
patient's ECG readings. A one-lead ECG is picked up with dry stainless steel
electrodes, further adding to the comfort. The ECG is filtered to a bandwidth
of 0.5 to 60 Hz and sampled with a rate of 200 Hz. If the analysis identifies a
tachycardia including ventricular fibrillation, a bradycardia including an
asystole, or an arrhythmia absoluta, a message is automatically sent to the
relay station via a wireless data transmission. The message, includes an
indicator for the detected event and two minutes of ECG. The transmitted ECG
starts one minute before the detected event and ends one minute afterwards. To
enable this, the ECG chest strap always has the last minute of ECG stored in
its memory. Testing has shown that the settings for the detection need to be
adapted to the individual patient, and is now possible via the EHR.
Once the ECG reading has
been transmitted, the relay station switches the wireless near-field
communication from the ECG chest strap to the wireless far-field communication
and then to the EHR. For near and far-field communications, bluetooth and
General Packet Radio Service (GPRS), respectively, are applied. The relay
station is a mobile phone with an integrated application for data handling.
Once the data is in the EHR, it is stored in a database and, depending on the
prior setting, a message is sent to a care provider. This can be via fax, SMS, email
or voice call. The EHR is especially adapted to the needs of a telemonitoring
system. To ensure data security, the EHR complies with high security standards
for EHRs such as tripple DES incryption and XPath compatible access rights
managed. The care provider has to log in via a secure internet connection and
can then access the ECG and any additional data from the medical history of the
patient. On this basis, he can make a qualified decision as to what actions
should be taken. In less acute cases, it is sufficient to make an appointment
with the family physician. In acute cases the emergency medical service is sent
to the patient to guarantee prompt assistance.
Results of the System Implementation
The described system and
its parts were tested in detail and proved to be reliable. Although dry
electrodes were used, the ECG signal in this long-term application showed no
significant differences to standard Holter ECGs. The system was tested with a
dozen patients suffering from persistent atrial fibrillation, tachycardia and
bradycardia. All the pathologies were identified correctly. The patients were
questioned about the application and the benefit of the system and the overall
impression was a remarkable 1.6 average score (1 best; 6 worst), with comfort,
simple application and handling especially being mentioned. The algorithm tests
with different databases showed both a sensitivity and a specificity of over
88%. Further extensive tests are currently being conducted.
Scenarios of Application
There are different
circumstances in which the system can be applied. The most important may be for
hospitals to save costs in diagnostic related group (DRG) surroundings. With
such a system, patients can leave the hospital much earlier without the risk of
unnoticed medical complications. At home they profit from a more comfortable atmosphere.
Furthermore, patients hooked up to an expensive monitoring unit can be moved to
a normal ward when they are equipped with this system.
Other scenarios would be
the temporary monitoring of pre-operative patients who could stay at home instead
of waiting for the operation in the hospital.
Another interesting area
is the preventative monitoring of high-risk patients, e.g. in disease
management programmes, where the option to extend the ECG system by other
relevant sensors (see Table 1) is an advantage. This allows an adaptation of the
system to the specific needs of the patient.
This monitoring system meets current and future demands of the healthcare sector, which is more and more aiming at the ambulatory area. This system provides the necessary security for patients and their relatives to live without the threat of an unnoticed cardiac event. The ECG chest strap is the first device that can summon help to the patient’s home automatically without the necessity that the patient himself has to be active, and is an available CE certified medical product. This system, which can be combined with other vital sensors, provides an ideal platform for hospitals, disease management programs and many other homecare applications.