Described embodiments include a system, including sample-and-hold circuitry, configured to sample a plurality of intracardiac electrocardiographic (ECG) signals acquired by respective electrodes disposed within a heart of a subject, and a processor. The processor is configured to receive, from one or more contact-indicating sensors, contact-indicating signals that indicate respective likelihoods of the electrodes being in contact with tissue of the heart, and, in response to the likelihoods being different from each other, cause the ECG signals to be sampled, by the sample-and-hold circuitry, at different respective sampling frequencies. Other embodiments are also described.
