I just called my vet. They have not seen anything unusual with Heartguard. And, by the way, she told me that Intercepter is not available this year so its not an option anyway. Something to do with manufacturing problems at the company that they hope to solve for next year.
She recommended I keep him on the Heartguard and get tested at the normal time.
DW, 3 Kids and our Goldens
2012 Shamrock 233S
2008 Toyota Sequoia 5.7L 4WD