GUARDIAN the world's first and only heart attack warning system

Information for healthcare professionals


We have put together some commonly asked questions about the GUARDIAN. If you have a question you can not find the answer to please get in touch with us via our contact page.

The GUARDIAN® is the world’s first and only FDA-approved implantable cardiac monitor and patient alerting system for detection of Acute Coronary Syndrome (ACS) events, including heart attacks or unstable angina. The GUARDIAN has been proven to detect ACS events with or without symptoms and is able to detect other serious medical conditions such as atrial fibrillation, bundle branch blocks, and arrhythmias by monitoring the heart’s electrical signal 24 hours a day, 7 days a week.

The primary benefit of the GUARDIAN is its ability to alert a patient to a potential life-threatening event, as stated below by the FDA:

“An important consideration is that the device fills an unmet medical need by providing more effective diagnosis of a life-threatening condition compared to relying on patient symptoms alone.”

Additionally, the FDA found,

  1. The GUARDIAN is a more accurate predictor of ACS events when compared to symptoms alone.
  2. Clinical study data indicated that the GUARDIAN alert with accompanying symptoms proved twice as accurate as symptoms alone for predicting real ACS events.
  3. The GUARDIAN has been proven to detect silent ACS events i.e. silent MI’s. This is the first time a device has been proven capable of addressing the huge problem of asymptomatic ACS events.

Immediately after implant, the GUARDIAN device is designed to learn what is “normal” for each patient by analysing thousands of heartbeats over a 7-to-14-day period. The result is the patient’s baseline electrogram. Once that baseline is in place, the GUARDIAN continuously collects a 10 second electrogram every 90 seconds, analyses it, and compares the result to the baseline segment. An Emergency Alarm will sound when 3 consecutive segments are significantly different from the baseline.

When the patient experiences changes in their electrogram one of two types of warnings will occur:

  • Emergency Alarm – This is the most serious warning, indicating the GUARDIAN has detected the electrogram changes to the ST segment associated with an ACS event. The patient is notified using 3 different modalities – tactile (vibration), auditory (beeping), and visually (blinking LED). The patient is trained to call emergency services immediately.
  • See Dr. Alert – This is a less urgent warning indicating the GUARDIAN has detected a condition that the patient’s doctor should evaluate. These changes are typically related to heart rate (fast or slow) or heart rhythm (irregular beat to beat) disturbances. The patient is notified using the same 3 methods as the Emergency Alarm but with a distinctly different pattern. The patient is trained to call and make an appointment with their doctor.

The GUARDIAN implant procedure is identical to that of the very well-known and understood single chamber pacemaker implant procedure. It is an outpatient procedure taking approximately 30-minutes under local anesthesia.

The FDA independently determined that the GUARDIAN is safe and effective. The FDA-approved labelling indicates the GUARDIAN:

  • Detected Silent ACS Events including heart attack – A First in Man
  • Provided a clear Improvement over symptoms in identifying ACS events (Positive Predictive Value)
  • Provided a clear reduction in causing False Positive emergency department visits when compared to symptoms
  • Caused a significant reduction in Time to Door for real ACS events when compared to the Time to Door for symptoms-only ED presentations
  • Captures electrograms used to diagnose new onset serious medical conditions including atrial fibrillation, bundle branch blocks, and arrhythmias.
  • Measurable improvements in patient Quality of Life
  • Documented low complication rate for well understood implant procedure

The GUARDIAN is yet to be approved by the TGA in Australia

The GUARDIAN is contraindicated in patients with any of the following:

  • Cognitive impairment that would prevent recognition of alarms.
  • Unable to feel the vibration from the IMD.
  • Patient has an implanted pacemaker, implantable cardioverter defibrillator (ICD) or cardiac resynchronisation therapy (CRT) devices.
  • A pacemaker lead cannot be placed safely.

The fundamental physics behind the measurement of the electrical signals of the heart is the same as that used by a traditional ECG machine. However, the GUARDIAN is measuring this electrical activity from inside the heart – so the fidelity and clarity of the signals are much better than those seen with a traditional surface ECG. In addition, since the device is permanently implanted, the device makes continuous monitoring of ambulatory patients possible without interruption regardless of where the patient is located and what the patient is doing – something external leads and devices are not capable of providing. The GUARDIAN leverages the IP of 58 issued US patents covering how to use Artificial Intelligence machine learning to do this.

No other device in the world is approved to detect the onset of ACS events. Devices without leads (such as loop recorders) are not capable of reliably detecting the subtle changes to the ST segment that is required for ACS event detection. Those devices are limited to detecting things related to heart rate and heart rhythm anomalies such as atrial fibrillation, syncope, etc. The GUARDIAN can detect all those conditions as well as the most life-threatening condition – heart attacks.

  • The GUARDIAN is not designed to detect Type 2 MIs since they are not associated with an acute coronary occlusion but rather are secondary to some other serious medical condition (such as pneumonia).
  • The GUARDIAN may also miss occlusions of bypass grafts due to the presence of some flow in the native vessel or occlusions of a prior stenosis (vessel narrowing) where collateral flow has developed.

Yes. Our experience with our patients confirmed that a coronary occlusion typically causes clear and obvious changes in the ST segment within 90 seconds when monitored from inside the heart as the GUARDIAN does.

At that point, there is no way to know which will become STEMI, or NSTEMI, or Unstable Angina. The goal of the GUARDIAN is to detect this change and get the patient to the ED as quickly as possible so that the standard methods for MI diagnosis can be applied. Early detection leads to early diagnosis and early treatment.

The simple answer is YES for ICDs, but more difficult to do for pacemakers. Since only 10% of heart attack survivors indicate for a pacemaker or ICD, putting the technology into those therapeutic devices would exclude the remaining 90% of patients from getting access to this technology.

The GUARDIAN technology provides the most benefit when used in a stand-alone device targeted for the largest group of a very high-risk patient population.

The ability to detect an ischemic heart region with an intracardiac electrode depends on the distance between that electrode and that ischemic region. If the electrode is within the ischemic region, ischemic detection is highly likely. If the electrode is outside of the ischemic region, detection sensitivity decreases as the distance between the electrode and the region increases. Therefore, to detect ischemia throughout the entire heart, the sensing electrode should be placed in a central location, which is the apex of the heart or the septal region adjacent thereto.


1. Gibson, M., Holmes, D., Mikdadi, G., et al. Implantable Cardiac Alert System for Early Recognition of ST-Segment Elevation Myocardial Infarction. JACC. 2019; 73(15):1919-1927.

2. Holmes, D.R., Krucoff, M.W., Mullin, C., et al. Implanted Monitor Alerting to Reduce Treatment Delay in Patients with Acute Coronary Syndrome Events. JACC. 2019; 74(16):2047-2055.

The GUARDIAN is not available for supply in Australia and is currently not included on the Australian Register of Therapeutic Goods.