IDE-ALERTS Continued Access Study

Inclusion Criteria (all must be true): * Subject previously participated in the ALERTS study and currently has either a Guardian System IMD plus IS-1 lead or IS-1 lead still in place and hasn't developed exclusion criteria. * Subject (men or women) is at least 21 years of age. * Women of childbearing age must have a negative pregnancy test or confirmation of one of the following: 1. Post-menopause or amenorrhoeic during the past year 2. Surgical sterilization 3. Use of effective contraceptive method Exclusion Criteria: * In the investigator's opinion, subject lacks ability to respond appropriately to alarms, e.g., illiteracy, poor memory or cognitive function, dementia or other condition affecting memory function, etc. * Known compromised tissue at the site of lead implantation in the apex of the right ventricle, e.g., prior infarct affecting the RV apex location. * A permanent pacemaker or ICD is already in place or the patient is indicated for ICD or pacemaker implantation based on the guidelines published by the American College of Cardiology as Class I and IIa recommendations. Class IIb recommendations are at the investigator's discretion. * Subject cannot feel the IMD vibration when placed on top of the skin on the left pectoral side of the chest. * Subject has recurrent or persistent atrial fibrillation. * Subject has recurrent or persistent non-sinus cardiac rhythm, second- or third-degree atrioventricular blocks, QRS duration greater than 120 ms, Benign Early Repolarization (BER), Brugada Syndrome, (LBB, BBB, RBB) or Rate Induced BBB. * Subject has left ventricular hypertrophy evidenced by EKG criteria. * Subject has any condition preventing the subcutaneous implantation of the Guardian System in a left pectoral pouch, such as: 1. superior vena cava thrombosis, 2. subcutaneous tissue deemed inappropriate for the procedure 3. prior central venous access via portacath, Hickman, Groshong, or similar placed in a left pectoral location or left side PICC line. * Extremely heavy alcohol consumption (participates in binge drinking that leads to alcohol intoxication) or has history of alcohol or illicit drug abuse within past 5 years. * Evidence of unresolved infection (fever \> 38o C and/or leukocytosis \> 15,000). * History of bleeding disorders or severe coagulopathy (platelets \< 100,000 plts/ml; APTT or PT \> 1.3 x reference range). * Subject has had a hemorrhagic stroke or transient ischemic attack (TIA) in the past 6 months. * Subject has other severe diseases, such as cancer or refractory congestive heart failure, associated with limitation of life expectancy (less than 1 year), which may lead to inadequate compliance to the protocol or confusing data interpretation. * Subject has clinical conditions such as heart diseases, difficult-to-control blood pressure, difficult-to-control insulin-dependent diabetes or serious prior infections attributed to the diabetes, or others that, at the investigator's discretion, could seriously affect the subject's current clinical condition during study procedures. * Subject has current participation or previous participation in another drug or device study in the past 30 days that conflicts with this study as determined by the study sponsor. * Gastro-intestinal hemorrhage in the past 6 months. * Subject has any situation in which the use of aspirin is contraindicated for at least 6 months. * Subject has epilepsy * Subject has known severe allergies, e.g., peanut, bee sting.