Apex domains cannot have CNAME records.
Question and response
Question
dig ohioheartandvascular.com. NS
Answer
ohioheartandvascular.com. 5 NS ns-1070.awsdns-05.org.
ohioheartandvascular.com. 5 NS ns-782.awsdns-33.net.
ohioheartandvascular.com. 5 NS ns-1799.awsdns-32.co.uk.
ohioheartandvascular.com. 5 NS ns-1147.awsdns-15.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0