System for detecting atrial fibrillation notwithstanding high and variable ventricular rates

A system for detecting an atrial arrhythmia comprising:

• sensing means adapted to be associated with at least one atrium of a heart to provide a cardiac signal during a plurality of cardiac cycles of the heart;
• means for determining a cardiac interval duration for each of the cardiac cycles;
• and
• an atrial arrhythmia detector for analyzing the cardiac signal provided by the sensing means during selected ones of the cardiac cycles, each one of the selected ones of the cardiac cycles having a cardiac interval greater than a predetermined duration.

An implantable atrial defibrillator for applying cardioverting electrical energy to atria of a heart when the atria are in need of cardioversion, the atrial defibrillator comprising:

• sensing means adapted to be associated with the atria of a heart for sensing electrical activity of the heart during at least one cardiac cycle of the heart and providing a cardiac signal;
• a detector for detecting a cardiac interval associated with the at least one cardiac cycle;
• a timer for timing the duration of the cardiac interval;
• an atrial arrhythmia detector for analyzing the cardiac signal provided by the sensing means during the at least one cardiac cycle when the cardiac interval is greater in duration than a preselected duration to detect an atrial arrhythmia of the heart;
• and
• a cardioverter for applying cardioverting electrical energy to the atria responsive to the atrial arrhythmia detector detecting an atrial arrhythmia of the heart.

An implantable atrial defibrillator for applying cardioverting electrical energy to atria of a heart when the atria are in need of cardioversion, the atrial defibrillator comprising:

• sensing means adapted to be associated with at least one atrium of a heart to provide a cardiac signal during a plurality of cardiac cycles of the heart;
• means for determining a cardiac interval duration for each of the cardiac cycles;
• an atrial arrhythmia detector for analyzing the cardiac signal provided by the sensing means during selected ones of the cardiac cycles, each one of the selected ones of the cardiac cycles having a cardiac interval greater than a predetermined duration;
• and
• a cardioverter for applying cardioverting electrical energy to the atria responsive to the atrial arrhythmia detector detecting an atrial arrhythmia of the heart.