here is how i see it, there are several areas where you will be judged:
pedigree (college, med school, residency and so forth)
academic potential (research, papers, posters)
fame (Who do you know aka Letters of Rec)
how good are your clinical-cardiology instincts/knowledge/execution (sorry, not part of the equation unfortunately... yeah, yeah, people can talk about it in your letters but everybody's letter of rec say this guy/girl is a clinical wiz kid and we all can't be that so anyways ;-)
of the three main areas your weakness is your pedigree, your academic potential is decent but not good enough to make up for the first part. you need couple of circulation/JACC papers before it can over come it.
soooo, what you can work on for future sake is your fame buddy, pretty much what i'm saying is finding the biggest fat cat in the world of cards and kiss his/her ass to no end, do research with them, wash their car, whatever it takes for them to write you some good letters and when the time is right make some phone calls for you.
in the end i know quite a few kids that had pretty much no academia potential (abstract here, poster there... pure BS in my mind), decent pedigree (IVY league, top tier residency) and pretty good fame (letters from fat cats) and they hit the jackpot with more interviews than they knew what to do with.
good luck,
OP