An implantable medical device comprising: a plurality of implantable electrodes to sense and pace a patient's heart, wherein the plurality of electrodes comprise: a left ventricular electrode (44, 46) positionable proximate the patient's left ventricle; and a cardiac conduction system electrode positionable proximate a portion of the patient's cardiac conduction system; and a computing apparatus comprising processing circuitry, the computing apparatus operably coupled to the plurality of implantable electrodes, wherein the computing apparatus is configured to: initiate delivery of cardiac conduction system pacing therapy to the patient's cardiac conduction system using the cardiac conduction system electrode; monitor local electrical activity of the patient using the left ventricular electrode during the delivery of cardiac conduction system pacing therapy using the cardiac conduction system electrode; and switch to delivery of both cardiac conduction system pacing therapy to the patient's cardiac conduction system using the cardiac conduction system electrode and left ventricular pacing therapy to the patient's left ventricle using the left ventricular electrode in response to the monitored local electrical activity. a plurality of implantable electrodes to sense and pace a patient's heart, wherein the plurality of electrodes comprise: a left ventricular electrode (44, 46) positionable proximate the patient's left ventricle; and a cardiac conduction system electrode positionable proximate a portion of the patient's cardiac conduction system; and a left ventricular electrode (44, 46) positionable proximate the patient's left ventricle; and a cardiac conduction system electrode positionable proximate a portion of the patient's cardiac conduction system; and a computing apparatus comprising processing circuitry, the computing apparatus operably coupled to the plurality of implantable electrodes, wherein the computing apparatus is configured to: initiate delivery of cardiac conduction system pacing therapy to the patient's cardiac conduction system using the cardiac conduction system electrode; monitor local electrical activity of the patient using the left ventricular electrode during the delivery of cardiac conduction system pacing therapy using the cardiac conduction system electrode; and switch to delivery of both cardiac conduction system pacing therapy to the patient's cardiac conduction system using the cardiac conduction system electrode and left ventricular pacing therapy to the patient's left ventricle using the left ventricular electrode in response to the monitored local electrical activity. initiate delivery of cardiac conduction system pacing therapy to the patient's cardiac conduction system using the cardiac conduction system electrode; monitor local electrical activity of the patient using the left ventricular electrode during the delivery of cardiac conduction system pacing therapy using the cardiac conduction system electrode; and switch to delivery of both cardiac conduction system pacing therapy to the patient's cardiac conduction system using the cardiac conduction system electrode and left ventricular pacing therapy to the patient's left ventricle using the left ventricular electrode in response to the monitored local electrical activity.