A neural stimulation system adapted to be coupled to a living subject having a circulatory system, the neural stimulation system comprising: a stimulation output circuit to deliver neural stimulation pulses; an implantable reference signal sensor to sense a reference signal indicative of cardiac cycles each including a predetermined type timing reference event, the implantable reference signal sensor configured to be placed external to the circulatory system and including one or more subcutaneous electrodes adapted to sense a subcutaneous electrocardiogram signal, the predetermined type timing reference event including a predetermined type cardiac event; a reference event detection circuit (234, 334) coupled to the implantable reference signal sensor, the reference event detection circuit adapted to detect the predetermined type timing reference events and including a cardiac event detection circuit adapted to detect the predetermined type cardiac event from the subcutaneous ECG signal; a cardiac parameter measurement circuit coupled to the one or more subcutaneous electrodes and adapted to measure one or more cardiac parameters including an atrioventricular interval from the subcutaneous ECG signal; an arrhythmia detection circuit to detect an arrhythmia from the subcutaneous ECG signal; a stimulation control circuit (236, 336, 436) coupled to the stimulation output circuit, the cardiac parameter measurement circuit, the arrhythmia detection circuit, and the reference event detection circuit, the stimulation control circuit adapted to adjust the delivery of the neural stimulation pulses using the measured one or more cardiac parameters including the atrioventricular interval, the stimulation control circuit further adapted to withhold the delivery of the neural stimulation pulses when the arrhythmia is detected, and including a synchronization module (238, 338, 438) adapted to synchronize the delivery of the neural stimulation pulses to the predetermined type timing reference events; and an implantable medical device (110, 510) including at least the stimulation output circuit, the reference event detection circuit, and the stimulation control circuit, the implantable medical device including a hermetically sealed can to house its circuit and a header attached to the can, wherein the one or more subcutaneous electrodes include one or more header electrodes incorporated into the header. a stimulation output circuit to deliver neural stimulation pulses; an implantable reference signal sensor to sense a reference signal indicative of cardiac cycles each including a predetermined type timing reference event, the implantable reference signal sensor configured to be placed external to the circulatory system and including one or more subcutaneous electrodes adapted to sense a subcutaneous electrocardiogram signal, the predetermined type timing reference event including a predetermined type cardiac event; a reference event detection circuit (234, 334) coupled to the implantable reference signal sensor, the reference event detection circuit adapted to detect the predetermined type timing reference events and including a cardiac event detection circuit adapted to detect the predetermined type cardiac event from the subcutaneous ECG signal; a cardiac parameter measurement circuit coupled to the one or more subcutaneous electrodes and adapted to measure one or more cardiac parameters including an atrioventricular interval from the subcutaneous ECG signal; an arrhythmia detection circuit to detect an arrhythmia from the subcutaneous ECG signal; a stimulation control circuit (236, 336, 436) coupled to the stimulation output circuit, the cardiac parameter measurement circuit, the arrhythmia detection circuit, and the reference event detection circuit, the stimulation control circuit adapted to adjust the delivery of the neural stimulation pulses using the measured one or more cardiac parameters including the atrioventricular interval, the stimulation control circuit further adapted to withhold the delivery of the neural stimulation pulses when the arrhythmia is detected, and including a synchronization module (238, 338, 438) adapted to synchronize the delivery of the neural stimulation pulses to the predetermined type timing reference events; and an implantable medical device (110, 510) including at least the stimulation output circuit, the reference event detection circuit, and the stimulation control circuit, the implantable medical device including a hermetically sealed can to house its circuit and a header attached to the can, wherein the one or more subcutaneous electrodes include one or more header electrodes incorporated into the header.