Methods for optimizing an atrioventricular (AV) pacing delay interval based upon ECG-based optimization such that an AV pacing delay interval value can be dynamically adjusted in an ambulatory subject. Ends of P-waves are determined. An operating atrioventricular interval is modified to maintain intervals between the determined ends of P-waves and beginnings of corresponding following QRS complexes above a predetermined certain value. The value may be between 30 and 60 milliseconds.
