A cardiac rhythm management, CRM, system, comprising: an implantable medical device including: an electrogram sensing circuit to sense an intracardiac electrogram; a wireless electrocardiogram, ECG, sensing circuit to concurrently sense a subcutaneous ECG; a first arrhythmia detection circuit adapted to receive the intracardiac electrogram and to detect an arrhythmia from the intracardiac electrogram; a second arrhythmia detection circuit adapted to receive the subcutaneous ECG and to concurrently detect the arrhythmia from the subcutaneous ECG; an arrhythmia detection confirmation circuit coupled to the first arrhythmia detection circuit and the second arrhythmia detection circuit, the arrhythmia detection confirmation circuit adapted to indicate a detection of the arrhythmia based on whether the arrhythmia is detected by the first arrhythmia detection circuit and whether the arrhythmia is concurrently detected by the second arrhythmia detection circuit; a hermetically sealed can housing the electrogram sensing circuit, the wireless ECG sensing circuit, the first arrhythmia detection circuit, the second arrhythmia detection circuit and the arrhythmia detection confirmation circuit; and a header attached to the hermetically sealed can; and a plurality of implantable subcutaneous electrodes coupled to the wireless ECG sensing circuit and incorporated onto one or both of the hermetically sealed can and the header, wherein the wireless ECG sensing circuit is configured to sense the subcutaneous ECG using the plurality of implantable subcutaneous electrodes. an implantable medical device including: an electrogram sensing circuit to sense an intracardiac electrogram; a wireless electrocardiogram, ECG, sensing circuit to concurrently sense a subcutaneous ECG; a first arrhythmia detection circuit adapted to receive the intracardiac electrogram and to detect an arrhythmia from the intracardiac electrogram; a second arrhythmia detection circuit adapted to receive the subcutaneous ECG and to concurrently detect the arrhythmia from the subcutaneous ECG; an arrhythmia detection confirmation circuit coupled to the first arrhythmia detection circuit and the second arrhythmia detection circuit, the arrhythmia detection confirmation circuit adapted to indicate a detection of the arrhythmia based on whether the arrhythmia is detected by the first arrhythmia detection circuit and whether the arrhythmia is concurrently detected by the second arrhythmia detection circuit; a hermetically sealed can housing the electrogram sensing circuit, the wireless ECG sensing circuit, the first arrhythmia detection circuit, the second arrhythmia detection circuit and the arrhythmia detection confirmation circuit; and a header attached to the hermetically sealed can; and a plurality of implantable subcutaneous electrodes coupled to the wireless ECG sensing circuit and incorporated onto one or both of the hermetically sealed can and the header, wherein the wireless ECG sensing circuit is configured to sense the subcutaneous ECG using the plurality of implantable subcutaneous electrodes. an electrogram sensing circuit to sense an intracardiac electrogram; a wireless electrocardiogram, ECG, sensing circuit to concurrently sense a subcutaneous ECG; a first arrhythmia detection circuit adapted to receive the intracardiac electrogram and to detect an arrhythmia from the intracardiac electrogram; a second arrhythmia detection circuit adapted to receive the subcutaneous ECG and to concurrently detect the arrhythmia from the subcutaneous ECG; an arrhythmia detection confirmation circuit coupled to the first arrhythmia detection circuit and the second arrhythmia detection circuit, the arrhythmia detection confirmation circuit adapted to indicate a detection of the arrhythmia based on whether the arrhythmia is detected by the first arrhythmia detection circuit and whether the arrhythmia is concurrently detected by the second arrhythmia detection circuit; a hermetically sealed can housing the electrogram sensing circuit, the wireless ECG sensing circuit, the first arrhythmia detection circuit, the second arrhythmia detection circuit and the arrhythmia detection confirmation circuit; and a header attached to the hermetically sealed can; and a plurality of implantable subcutaneous electrodes coupled to the wireless ECG sensing circuit and incorporated onto one or both of the hermetically sealed can and the header, wherein the wireless ECG sensing circuit is configured to sense the subcutaneous ECG using the plurality of implantable subcutaneous electrodes.