Comparing Rate Response With CLS Versus Accelerometer ICD Settings in Heart Failure Patients With BIOTRONIK CRT-Ds (CLASS)

University of California San Diego logo

University of California San Diego




Chronotropic Incompetence
Heart Failure


Device: CLS Mode on Biotronik CRT-D
Device: Accelerometer Mode on Biotronik CRT-D

Study type


Funder types




Details and patient eligibility


Dr. Jonathan Hsu and Dr. Eric Adler are conducting a research study to find out more about how implantable cardiac defibrillator (ICD) settings can be adjusted to improve patient cardiovascular health and quality of life. Patients are being asked to participate in this study if they have a history of heart failure and have or are scheduled to be implanted with a BIOTRONIK ICD that is capable of closed loop stimulation (CLS). CLS is a device setting that works with the cardiovascular system to optimize their heart rate during physical activity. This study is comparing BIOTRONIK's CLS setting to a standard accelerometer setting, which also is able to adjust the heart rate by movement sensors, when necessary. This study has been initiated by Dr. Hsu and Dr. Adler and is financially supported by BIOTRONIK, Inc. There will be approximately 15 participants in this trial.

Full description

This study is a prospective, randomized, single-blind crossover study intended to enroll patients who are implanted or are scheduled to be implanted with a Biotronik CLS and accelerometer capable CRT-D device. Patients will serve as their own control group with regard to modes of rate-adaptive pacing. Patients with a previously implanted Biotronik CRT-D device with CLS-capability will be recruited from health care institutions in San Diego and all dedicated functional testing will be performed at the University of California, San Diego (UCSD). The goal enrollment target for analysis will be 15 patients, with up to 20 patients enrolled to allow for withdrawals. The purpose of this study is to evaluate whether changes to an implanted ICD can improve the functional status of patients with suspected chronotropic incompetence (CI). CI is a condition in which the heart rate is unable to adequately respond to meet the patient's physical demands, such as walking, climbing stairs, or doing household chores. CI is common in patients with cardiovascular disease, particularly in patients with heart failure. Common clinical management of patients with suspected CI is to activate an accelerometer setting in the cardiac resynchronization therapy with defibrillator (CRT-D) device. An accelerometer will adjust the heart rate to fit the physiological circumstances and needs of the patient based on patient movement only. BIOTRONIK is a company that has developed a novel technology included in the settings for CRT-D devices that offers CLS as an alternative to a standard accelerometer. CLS utilizes sensed electrical properties of the heart in order to assess what may be the best heart rate for both physical and mental demands. This study is designed to compare whether patients will benefit from CLS when compared with standard accelerometer technology.


12 patients




18 to 99 years old


Accepts Healthy Volunteers

Inclusion criteria

  • Patients with a BIOTRONIK CRT-D device (capable of CLS and accelerometer rate responsive pacing)
  • Patients at least 18 years old
  • Patients who have plausible symptoms of CI based on previous monitoring and clinical symptoms

Exclusion criteria

  • Pregnant patients
  • Patients who are unwilling/unable to provide informed consent
  • Patients who are unable to complete study related procedures
  • Current persistent atrial fibrillation

Trial design

Primary purpose




Interventional model

Crossover Assignment


Single Blind

12 participants in 2 patient groups

CLS Mode on Biotronik CRT-D
Experimental group
All 15 patients will be randomized to this group. Their device will be set in the CLS mode for 1 week.
Device: CLS Mode on Biotronik CRT-D
Accelerometer Mode on Biotronik CRT-D
Active Comparator group
All 15 patients will be randomized to this group. Their device will be set in the accelerometer rate responsive mode for 1 week.
Device: Accelerometer Mode on Biotronik CRT-D

Trial documents

Trial contacts and locations



Data sourced from

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