High Service Broker queue
TRY TOP 10000 INSTEAD of 1 to quickly read messages from Queue that will clean the queue faster

WAITFOR ( RECEIVE TOP ( 10000) 
                   CONVERT(XML, CONVERT(NVARCHAR(MAX), message_body))                  
                  FROM dbo.[EventNotificationQueue] 

&gt; --into @message_body

                  ), TIMEOUT 1000