Okay, (rubs hands together)... ready for an answer. I'll try to combine information from the comments (and will happily edit based on feedback if I've misconstrued anything).
To your question specifically. The T101 blades (or a similar generic) will turn tight curves because of its thin back and cut fairly cleanly. Don't worry about the supposed 15mm depth restriction -- the blade is long enough to go through 18mm. (It won't cut quite as cleanly as the fleam cut teeth of the 308, but not far off in MDF. The 308, by the way won't turn tight curves easily because of the thick back of the blade.) The T244 will be a rougher cut due to the nature of the teeth.
The bad thing about the T101 and T244 blades is that they won't track straight lines as nicely as a more typical (thicker) blade. One might want to cut curves with the thin blade and then switch.
You could also get away with using a normal 'clean for wood' blade with a thick back, and simply going back and forth to nibble up to the line. Just be sure to make enough room in the kerf that you can pivot the blade for a tight curve.
Depending on the jigsaw, blades can skew off vertical when cutting tight curves. Be sure to do a test piece and see that the front and back are lined up to your needs. If you find too much skew, then slow down and do more back and forth nibbling, rather than straight ahead cutting. (The downside to the nibbling is that it'll take more cleanup afterwards.)
Alternately, you could drill the round parts with a forstner bit (sometimes called sawtooth, though there are slight technical differences) or a holesaw.
A large forstner bit is non-cheap and ideally would be used in a drill press. Lacking a drill press, one would make a guide template with the same size hole and clamp it on your finish piece to constrain the forstner. (To make the first hole in the template, tack 3 strips of anything up against the sides of the forstner bit. The first template can be used to create an additional template that has two or four perfectly spaced holes.)
The holesaw is cheaper, though slower. Again, a drill press would be ideal, but because the holesaw has a pilot bit, it's a little easier to drill accurate holes handheld. A guide template would guarantee that you didn't skitter off and mess up your final product. Tip: clean the mdf dust off the holesaw teeth regularly... the dust clogs the gullets, which creates heat, which leads to premature dulling of the holesaw teeth. Tip 2: drill a hole in the rim of the holesaw's cutting path (inside the heart where it'll be waste) to help sawdust get knocked off the teeth.
To be very clear: using a handheld drill and either the forstner or holesaw isn't ideal. Take it slow and position yourself in a way that doesn't get your arm ripped off when the bit binds. You also need to be perfectly perpendicular.
If you go the round hole route, then cutting the straight lines down to the bottom point of the heart can be done with any old 'clean for wood' blade.
As a complete aside, if I had 20 of these to do, I'd readily justify the purchase of a router and a template setup, but I understand that not everyone is as addicted to power tools as me.
Thanks @Graphus and @SaSSafraS1232 for comments.
