Method and system for characterizing supraventricular rhythm during cardiac pacing

#The present invention relates generally to implantable medical devices and, more particularly, to generating, with an implantable medical device, a characterization of a patient's supraventricular cardiac rhythm while the heart is being paced.

#The healthy heart produces regular, synchronized contractions. Rhythmic contractions of the heart are normally controlled by the sinoatrial (SA) node, specialized cells located in the upper right atrium. The SA node is the normal pacemaker of the heart, typically initiating 60-100 heart beats per minute. When the SA node is pacing the heart normally, the heart is said to be in normal sinus rhythm (NSR).

#If heart contractions are uncoordinated or irregular, the heart is denoted to be arrhythmic. Cardiac arrhythmia impairs cardiac efficiency and can be a potential life threatening event. Cardiac arrythmias have a number of etiological sources including tissue damage due to myocardial infarction, infection, or degradation of the heart's ability to generate or synchronize the electrical impulses that coordinate contractions.

#FIG. 1 is a partial view of one embodiment of a single chamber implantable cardioverter/defibrillator with an endocardial lead system extending into the right ventricle of a heart;

#FIG. 2 is a partial view of one embodiment of a dual chamber implantable cardioverter/defibrillator with an endocardial lead system extending into right atrial and right ventricular chambers of a heart;

#FIG. 3 is a partial view of one embodiment of an implantable cardioverter/defibrillator with an endocardial lead system extending into the right atrium and the right and left ventricles of a heart;

#While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail below. It is to be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.

#In the following description of the illustrated embodiments, references are made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration, various embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized, and structural and functional changes may be made without departing from the scope of the present invention.

#A proper characterization of a patient's supraventricular conducted rhythm (SVR) requires detection of unpaced or intrinsic heartbeats. Although various methods have been proposed for characterizing a patient's SVR, these characterization methods are often dependent upon acquiring a sufficient number of intrinsic beats. One such method is described in commonly owned U.S. patent application Ser. No. 09/845,987, filed Apr. 30, 2001, and entitled “Normal Cardiac Rhythm Template Generation System and Method,” which is hereby incorporated herein by reference. Another method is described in commonly owned U.S. patent application entitled “Method and System for Characterizing a Representative Cardiac Beat Using Multiple Templates,” identified under Attorney Docket No. GUID.041 US01, filed Mar. 25, 2002, which is hereby incorporated herein by reference.