A stimulation device for use in applying His bundle pacing of a patient's heart (12, 1501, 1701), the stimulation device comprising: a housing containing a memory and a controller; a His bundle lead (21, 1502, 1702) coupleable to each of the housing and the patient's heart (12, 1501, 1701) and a His bundle (1504, 1704) of the patient's heart (12, 1501, 1701); and a ventricular lead (24, 30, 1506, 1706, 1720) coupleable to each of the housing and a ventricle (1508, 1708, 1722) of the patient's heart (12, 1501, 1701); wherein the controller is configured to: apply, through the His bundle lead (21, 1502, 1702), a pacing impulse to the His bundle (1504, 1704); and measure, using the ventricular lead (24, 30, 1506, 1706, 1720), a response of the patient's heart (12, 1501, 1701) to application of the impulse, the response including a response of the ventricle (1508, 1708, 1722), characterized in that the controller is also configured to: calculate a ventricular delay, the ventricular delay being a time from application of the pacing impulse to onset of the response of the ventricle (1508, 1708, 1722); and apply, using the ventricular lead (24, 30, 1506, 1706, 1720), a backup impulse to the ventricle (1508, 1708, 1722) when at least the ventricular delay exceeds a delay value stored in the memory. a housing containing a memory and a controller; a His bundle lead (21, 1502, 1702) coupleable to each of the housing and the patient's heart (12, 1501, 1701) and a His bundle (1504, 1704) of the patient's heart (12, 1501, 1701); and a ventricular lead (24, 30, 1506, 1706, 1720) coupleable to each of the housing and a ventricle (1508, 1708, 1722) of the patient's heart (12, 1501, 1701); wherein the controller is configured to: apply, through the His bundle lead (21, 1502, 1702), a pacing impulse to the His bundle (1504, 1704); and measure, using the ventricular lead (24, 30, 1506, 1706, 1720), a response of the patient's heart (12, 1501, 1701) to application of the impulse, the response including a response of the ventricle (1508, 1708, 1722), characterized in that the controller is also configured to: calculate a ventricular delay, the ventricular delay being a time from application of the pacing impulse to onset of the response of the ventricle (1508, 1708, 1722); and apply, using the ventricular lead (24, 30, 1506, 1706, 1720), a backup impulse to the ventricle (1508, 1708, 1722) when at least the ventricular delay exceeds a delay value stored in the memory. apply, through the His bundle lead (21, 1502, 1702), a pacing impulse to the His bundle (1504, 1704); and measure, using the ventricular lead (24, 30, 1506, 1706, 1720), a response of the patient's heart (12, 1501, 1701) to application of the impulse, the response including a response of the ventricle (1508, 1708, 1722), characterized in that the controller is also configured to: calculate a ventricular delay, the ventricular delay being a time from application of the pacing impulse to onset of the response of the ventricle (1508, 1708, 1722); and apply, using the ventricular lead (24, 30, 1506, 1706, 1720), a backup impulse to the ventricle (1508, 1708, 1722) when at least the ventricular delay exceeds a delay value stored in the memory. calculate a ventricular delay, the ventricular delay being a time from application of the pacing impulse to onset of the response of the ventricle (1508, 1708, 1722); and apply, using the ventricular lead (24, 30, 1506, 1706, 1720), a backup impulse to the ventricle (1508, 1708, 1722) when at least the ventricular delay exceeds a delay value stored in the memory.