Apparatus comprising an ultrasound ablation system, which comprises a reflection-facilitation element, configured to be placed at an extramyocardial site of a subject, and to provide an extramyocardial reflective region and an ultrasound tool, which comprises at least one ultrasound transducer configured to be positioned within a heart chamber of the subject. The ultrasound transducer is configured to ablate myocardial tissue by applying ultrasound energy to the myocardial tissue such that at least a portion of the transmitted energy is reflected by the reflective region onto the myocardial tissue. Other embodiments are also described.
