Begin by laying the pretzels in a single layer onto wax paper.  Melt almond bark in the microwave.  Start with 1 minute, stir and continue with 30 second intervals until completely melted.  Fill the middle of each pretzel with melted chocolate using a piping bag {or Ziploc bag} or small spoon, being careful to get the heart shape and sprinkle with heart sprinkles.  Work on no more than 5 pretzels at a time so that chocolate doesn't set up before adding sprinkles.  Let pretzels set at room temperature for 20-30 minutes or until chocolate is completely set up.  Serve or store in an air-tight container at room temperature.