Implantable cardioversion device with automatic filter control

An implantable cardioversion device for detecting and reverting ventricular fibrillation in a patient's heart, the device comprising:

• a ventricular sensor for sensing intrinsic ventricular activity and generating a corresponding sense signal;
• the ventricular sensor including:
• a filter for filtering the sense signal to generate a filtered signal, wherein the filter has an adjustable center frequency;
• a detector for detecting ventricular fibrillation or normal sinus rhythm based on the filtered signal;
• and
• a controller for adjusting the center frequency to a value corresponding to the most recently detected normal sinus rhythm;
• and
• a therapy generator for generating a prescribed therapy in response to the detector detecting ventricular fibrillation in the patient's heart.

A method of applying cardioversion therapy to a patient with an implantable cardioversion device coupled to the patient's heart, the method comprising the steps of:

• sensing an intrinsic signal in a cardiac chamber of the patient's heart to obtain a sensed signal;
• bandpass filtering the sensed signal to generate a filtered signal using a filter having a center frequency adjustable between a first frequency value corresponding to a normal sinus rhythm and a second frequency value corresponding to an abnormal cardiac condition;
• analyzing the filtered signal to detect a normal sinus rhythm condition;
• adjusting the center frequency toward the second value if a normal sinus rhythm is not detected to facilitate detecting the presence of an abnormal cardiac condition;
• and
• applying therapy in the presence of a detected abnormal cardiac condition.

A method of applying cardioversion therapy to a patient's heart with an implantable cardioversion device having an input bandpass filter with a center frequency adjustable between first and second frequency values, the method comprising the steps of:

• sensing an intrinsic signal in a chamber of the patient's heart to obtain a sensed signal;
• filtering the sensed signal with the input bandpass filter set at a first center frequency value corresponding to a normal sinus rhythm to generate a filtered signal;
• determining the presence of a normal sinus rhythm based on the filtered signal;
• adjusting the center frequency toward the second center frequency value corresponding to an abnormal cardiac condition if a normal sinus rhythm is not detected at the first center frequency value;
• determining the presence of an abnormal cardiac condition or a normal sinus rhythm;
• and
• changing the center frequency back to the first center frequency when a normal sinus rhythm is detected.