Shock Tactics

13 July 2008 (Last Updated July 13th, 2008 18:30)

For many patients with heart disease, wireless monitoring could allow on-the-spot diagnosis and early intervention. Lorrie Kelly talks to Fred Colen of Boston Scientific about the next generation of cardiac resynchronisation devices.

Shock Tactics
Next-generation CRT-D devices allow remote monitoring of patients.

For heart failure (HF) patients, frequent visits to a clinic are a regular part of treating their disease and unexplained symptoms can often lead to costly hospital stays.

Traditional methods for treating HF patients can place an enormous financial burden on patients and healthcare systems alike. But according to Fred Colen, president of the CRM group at Boston Scientific, this may soon change with next-generation CRT-D devices.

A CRT-D (cardiac resynchronisation therapy – defibrillator) is an implantable device designed to synchronise the contraction of right and left heart chambers as well as provide a "life-saving shock" when needed. They are a significant evolution from early-model pacemakers that focused impulses exclusively on the right ventricle, assuming that controlling one side would result in normal sinus rhythm.

Boston Scientific began working with key physicians who were involved in developing this pacing technology early on, in particular the pioneering clinic at Johns Hopkins University.

"Implementation of these new devices has decreased the number of sudden cardiac deaths by almost 30%."

"We had very good cooperation with many physicians in this area and we started a small clinical feasibility study with an early pacing device, where the output was not run to just the right ventricle but also to the left," explains Colen. "So, when you received the impulse on the right ventricular side, you also got the same impulse on the left side.

"The feasibility trial involved 50–60 patients. It was very successful and led to broader clinical trials."

Since then, implantable devices have evolved further, with CRT-D devices providing advanced functions such as independent timings for the contraction of left and right ventricles combined with defibrillation capability in the event of cardiac crisis. Studies have shown that implementation of these new devices has decreased the number of sudden cardiac deaths by almost 30%.

Today, there are two types of CRT devices:

  • CRT-D devices that pace both ventricles in synchrony with the capability of defibrillation
  • CRT-P devices that pace both ventricles but do not have the defibrillation shock option – a sophisticated pacemaker

"It has turned out during clinical practice, that with the HF patient population, it makes more sense to give them CRT-D devices because many of these patients are prone to fibrillation and are, therefore, in need of life-saving shocks as well," says Colen. "So, that is how the market has developed over time."

"If you look at the predecessors, these devices would give pacing pulses for the left and right side simultaneously and that was it," he explains. "Now, you can optimise the therapy to each individual patient's needs. So the heart can beat in synchrony at the best rate for the patient as observed by the doctor through ultrasound."

New-generation CRT-D devices such as Livian and Cognis include a feature called SmartDelay™ AV. Through this feature, the device does a series of measurements and then proposes how to programme the time between atrial contraction and ventricular pacing, known as the AV delay.

"The physician can then either accept the recommendation or override it," says Colen. "But the reaction from many physicians on this feature has been very positive. Sometimes they are surprised by the AV delay settings recommended by the device but when they try it, they can see a narrower QRS width on EKG."

REMOTE MONITORING

Boston Scientific's next-generation CRT-D devices include wireless capability that can interact with hospital equipment, peripherals or transmit data via a communication device kept in the home. The collected data can then be viewed by attending physicians, with an aim to improving early intervention timelines as well as monitor patient progress during the course of prescribed treatment.

The implications of these capabilities are huge for patients, physicians and healthcare systems alike. Remote monitoring of HF conditions could prove to be very cost effective over the course of a patient's life.

For the patient, the ability to send their relevant data remotely to their doctor could be a far better option, especially for those who live in remote locations or elderly patients without access to transportation.

For healthcare systems, early intervention can significantly reduce the overall cost of HF patient care. Data collected from the CRT-D implant would allow doctors to obtain a much more accurate picture of a patient's health at the moment of symptom onset, allowing them to act accordingly.

Boston Scientific's next-generation CRT-D devices such as Cognis/Telegen, scheduled for release later in 2008, are already capable of performing many of these functions. However, cost effectiveness is not the only focus, says Colen. The end objective is to further improve patient quality of life with cost benefits being a welcome by-product.

Recently released in the US, the Confient/Livian systems have been well received. "In the European environment, where RF different frequencies have to be used and where there is other general equipment and clinical equipment on the market, we have further optimised the RF capability in the presence of noise interference." says Colen.

According to Colen, Boston Scientific is also making major investments in creating remote monitoring capability within the European market, a feature already available in the US. This capability should be available in the large European countries by around the middle of next year.

"Data collected from the CRT-D implant would allow doctors to obtain a much more accurate picture of a patient's health at the moment of symptom onset.

Current models of Confient/Livian and Cognis/Teligen already have RF telemetry capability built-in. "So when the remote monitoring system becomes available next year in Europe, these patients will be able to participate," says Colen.

Test results from the remote monitoring function within the US have proven the extent of the implant's data capture and reporting capabilities. For example, one physician reported seeing a spike in their patient's blood pressure and called the next morning to discover they had been eating Chinese takeaway shortly before.

"It is a system which will notify the physician according to parameters they can set for individual patient events and allow them to intervene early to find out why their patient's blood pressure is spiking, thereby allowing them to work with the patient to find solutions," says Colen.

The new generation devices have also seen improvements in longevity to ensure more consistent battery performance. "We have been able to make the spread of the battery longevity and performance a lot narrower," says Colen. "We can now, for a much larger population, say devices such as Livian will last five years. Cognis will last around seven years, nearly a twofold gain in longevity compared to earlier models."

Although Cognis/Teligen devices last longer, they are thinner, smaller and easier to implant than their predecessors. And longer battery life combined with shrinking size has not come at the expense of intelligent features. The latest implants are more feature rich than ever and now include safety back-up systems.

"CRT-D devices are essentially microprocessor devices which run on firmware," explains Colen. "Though it is a rare occurrence, there is always a small probability that the firmware code might become corrupted which in turn might again in rare circumstances result in therapy not being available to the patient. Because of this, we have put SafetyCore into our Cognis/Teligen devices.

"SafetyCore is a separate, independent pacemaker and defibrillator which is hardwired to the circuitry and does not rely on software," he continues. "It is capable of pacing the heart and defibrillating in the event of software failure. Though it doesn't provide all of the optimisation intelligence that physicians like to use, it is a safety back-up system that, in the unlikely event something should happen, will ensure the patient is still protected and will continue to
receive therapy. I believe it is a powerful feature for the safety of the patient."

IMPLANTABLE INNOVATION

Looking to the future, Boston Scientific and Surgi-Vision Inc. have launched an agreement to develop "MRI-safe" technology for implantable cardiology devices. The agreement allows Boston Scientific access to Surgi-Vision's development capabilities as well as the benefit of licensing and future use of the technology in their implants.

"Patients who use these devices typically have other health issues and are quite often patients who would benefit from using diagnostic technology such as MRI scans," says Colen. "Today, all implantable systems are contraindicated to go through an MRI procedure due to the potential of heat damage to both the implantable device as well as to surrounding tissue."

The primary focus of modifications is centred on the leads which attach the implantable device to the heart. These leads can act as an antenna for the MRI signal and generate heat during a scan. "We are working on new technology to avoid this issue in the future," says Colen. "This would apply to all implantable cardiology devices from pacemaker to defibrillator."

"For next-generation CRT-D devices, we believe the earlier physicians can intervene on the downward health spiral that would end with a patient in hospital from decompensation of the heart, the more powerful this technology will become as a diagnostic tool," he continues. "Outside of weight and blood pressure, which are currently measured externally by the patient, we are looking at what other information we have built in to the device that we can make available to
physicians."

For example, Cognis/Teligen has sensors which can monitor a patient's respiratory rate. This feature will be made available to physicians in the near future. And Colen states the next step will be to monitor the patient's depth of breathing. "If the patient is experiencing very fast and shallow breathing, this will tell the doctor something isn't right," he says.

"So you can imagine, in that sense, there is a lot of data you can generate from the device that can be made available to doctors through this remote monitoring system. This information can further enhance the physician's ability to diagnose going into the future."

Last summer, Boston Scientific made a technology acquisition which will enable the company to measure pressure from inside the pulmonary artery. "It is a very small device which is implanted into the pulmonary artery of the patient and is envisaged to work with our existing implantable systems," says Colen.

"Patients who use these devices typically have other health issues and are quite often patients who would benefit from using diagnostic technology such as MRI scans."

"So, you can monitor the pressure in the pulmonary artery of a patient on a daily basis and see how that internal pressure is developing over time. This removes the burden from the patient of having to monitor their own blood pressure with an arm cuff, which isn't as accurate.

"We are gearing up to do another clinical study to demonstrate that once you make these additional parameters available, and make the pressure in the pulmonary artery available in the future, it will reduce the number of times that the patient ends up in hospital," he explains. "That is our aim.

"We want to make sure we keep HF patients stable and help them move on an improvement track instead of only monitoring them for deterioration.

"We believe there is a strong argument to be made that we can avoid future hospitalisations through this more sophisticated technology being utilised in patients compared to those without it.

"The feasibility studies for these additional features will probably begin next year," Colen concludes. "If the results work out as we hope, then there will be bigger studies to follow. And the technology might see commercial application around 2010–2012."