Determination of upper limit of vulnerability using a variable number of shocks

An implantable medical device, comprising:

• electrodes for sensing a cardiac electrical signal and for delivering a shock pulse to a patient's heart;
• a sensing module coupled to the electrodes for receiving the cardiac signal and analyzing the sensed signal for determining a signal quality parameter of the cardiac electrical signal;
• a shock pulse generating module coupled to the electrodes for delivering the shock pulse;
• and
• a control module coupled to the sensing module and the shock pulse generating module and configured to automatically determine a number of shock pulses to be delivered to the patient's heart in response to the signal quality parameter;
• the control module, sensing module, and shock pulse generating module configured to cooperatively deliver the scheduled number of shock pulses.

A computer readable medium for storing a set of instructions which when implemented in a medical device system cause the system to:

• analyze a cardiac electrical signal;
• determine a signal quality parameter of the cardiac electrical signal;
• determine a number of shock pulses to be delivered to a patient's heart in response to the signal quality parameter;
• and
• schedule the determined number of shock pulses to be delivered.