Heart is monosyllabic.
one
1
The word 'heart' has one syllable.
The word "hearts" has one syllable.
whole-heart-ed 3 syllables
Since the word heart has only one syllable, the concept of an accented syllable does not apply. You can only accent a syllable by giving it a greater emphasis than some other syllable or syllables in the same word, which means that you have to have at least two syllables.
Heart mainly has one syllable. If you find that it has two, then you're putting too much stress on its pronunciation.
The word 'answer' has 2 syllables. An-swer.
There are three syllables in the word syllables.
There are four syllables in the word "usually".
The word annoy has two syllables. The syllables of the word are an-noy.
The word pilot has two syllables. The syllables in the word are pi-lot.