A combustor for a gas turbine engine includes an annular shell, an annular bulkhead connected to the shell, and a heat shield panel. The heat shield panel has a first surface facing a combustion chamber and a second surface opposite the first surface. The heat shield panel is mounted to the bulkhead and defines a cooling chamber between the bulkhead and the heat shield panel. The heat shield panel has a wall extending from the heat shield panel toward the bulkhead around at least a portion of a periphery of the heat shield panel. The wall includes a circumferential wall portion including at least one cooling air passage extending between the cooling chamber and a cavity defined between the circumferential wall portion and the shell. The at least one cooling air passage is configured to purge the cavity by directing a first cooling air stream from the cooling chamber into the cavity.