is it possible for me to improve my heart rate recovery? am i screwed?

[xstalkrx]

21 year old male.  I used to smoke and do drugs for about 2 years.  I have quit all of that.

I went to a cardiologist...normal echocardiogram and he said I did good on the treadmill stress test.  BUT, he said my heart did not recover as fast as he would have liked.

What can I do to improve my recovery rate?  Or is it not possible for someone like me to improve it?  Have I screwed myself?  Please help.  I've been running on the treadmill for 4 days and have yet to see an improvement in recovery time.

I am on 180mg of cardizem la to relieve heart palpitations.  my cardiologist says I should only have to take this medication for about 3-6 months.  My heart rate doesnt speed up suddenly like it used to...but I can feel my pulse every now and then in my chest.

I have ran for 30 minutes at a 9 minute mile pace the last 4 days.  My pulse will reach 160.  When I am done exercising it will drop to 120 in about 4 minutes.  It will take about 25 minutes for it to come all the way down to resting again though.

Please tell me how bad of shape I am in and if I am doing the right thing to correct it.  Should I get my heart rate up to 170 so that I am within 85 percent of my max heart rate?