Adjustable sensing in a his-bundle pacemaker

A system for pacing a patient's heart, comprising:

• an electrostimulation circuit configured to provide electrostimulation energy to an interventricular septum between left and right ventricles of the patient's heart;
• a cardiac event detector configured to:
• receive atrial information and conduction system information sensed from the patient's heart;
• determine a sensing window following atrial activity in the atrial information, the sensing window shorter than a programmed atrial-to-ventricular delay and longer than a patient-specific intrinsic conduction system delay with respect to the atrial activity;
• and
• determine a presence or an absence of conduction system activity in the conduction system information in the determined sensing window;
• and
• a control circuit configured to generate a control signal to the electrostimulation circuit to deliver electrostimulation energy to the interventricular septum in the absence of the conduction system activity in the sensing window, and to withhold delivery of the electrostimulation energy to the interventricular septum in the presence of the conduction system activity in the sensing window.