[ath.pantelis]

I'm not 100% sure, but I think that nifedipine (I suppose that by SSBs you mean dihydropyridines, not verapamil/diltizem) exerts its effect mainly on arteries (not the veins, as nitrates do). Thus, when there is already a compromise to a coronary branch due to ACS, adding an arterial dilator will evoke coronary steal phenomenon.

 

[ath.pantelis]

2)Nitrates ---> potent venodilator---> decrease the preload ---> decresed
demand + also it is coronary dilator-- > increased supply

We have to mention, though, that the caronary dilatory effect of nitrates is exerted only on normal coronaries. If there is damage on the endothelium (like when there is a stable or unstable atheromatic plaque), this effect is rather negative, because the normal coronaries dilate and increase blood supply to their assigned myocardial area in the detriment of non-responding damaged coronaries.