Described embodiments include a system, including sample-and-holdcircuitry, configured to sample a plurality ofintracardiac electrocardiographic (ECG) signals acquired byrespective electrodes disposed within a heart of a subject, anda processor. Theprocessor is configured to receive, from oneor more contact-indicating sensors, contact-indicating signalsthat indicate respective likelihoods of the electrodes being incontact with tissue of the heart, and, in response to thelikelihoods being different from each other, cause the ECGsignals to be sampled, by the sample-and-hold circuitry, atdifferent respective sampling frequencies. Other embodimentsare also described.
