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Periodic breathing patterns known as Central Sleep Apnea (CSA) are often observed in congestive heart failure. This phenomenon is associated with increased risk of sudden cardiac death, but the mechanism for that outcome has not been exposed. Endocardial electrograms were recorded during spontaneous episodes of CSR and PB in patients in conscious and unconscious states. Analysis exposed a regular bidirectional phase-walk in the relationship between respiration and arterial blood pressure. Recently developed signal processing techniques revealed that respiration also modulates cardiac repolarization properties at multiple simultaneous frequencies, and the effect was heterogeneous across measurement sites in both ventricles. These measurements offer unique evidence of the electro-physiological manifestations of these breathing patterns. Analysis of phase relationships suggested a mechanism by which the behavior may predispose patients to cardiac arrhythmias. Such predisposition would be easily measured to direct treatment priorities and improve risk stratification.