Hi Mark
I Imagine that DVLA upon receiving the consultants report with suspend your HGV licence pending further enquiries. This is the standard route that they follow. However it will not mean that you cannot recover your licence at a future date. I had a heart attack in July 2012 , received 4 stents , had my licence suspended but was back driving HGV Class 1 on the 1st November 2012 , a total of 16 weeks later. So it need not be the end of your career.
The minimum criteria that you will face i imagine would be the treadmill test, which consists of you walking on a treadmill at various speeds and gradients for a period of approximatly 12 minutes. Whilst doing this you will be wired up to monitor your heart and blood pressures , providing you dont exceed the recomended heart rate levels and you can complete the treadmill excercise you most likely will retain your licence .
My advice is to listen to your consultant , impress upon him your desire to return to work and continue to make the efforts to get fit. The British Heart Foundation were a terrific source of help and advice in my case , they are accessible on line. Ask your GP to put you in touch will the local Heart Attack / Welfare Group who arrange special excercise classes in local amenities to assist you on your recovery , i found there advice and assistance invaluable.
Dont think that this is the end , it is the beginning , used loved ones and familly as sources of hope and inspiration , think about unfinished bussiness and what you still want to achieve and see and use it to help you through this difficult time.
Dont give up Big Fella , KRO 
John