De or het hartbeklemming?

The correct Dutch article is:

de hartbeklemming

Rule Words ending in -ing: almost always de. See the rule

How to use hartbeklemming

the hartbeklemmingde hartbeklemming
this hartbeklemmingdeze hartbeklemming
that hartbeklemmingdie hartbeklemming
our hartbeklemmingonze hartbeklemming
your hartbeklemmingjouw hartbeklemming
every hartbeklemmingelke hartbeklemming
which hartbeklemming?welke hartbeklemming?
a big hartbeklemming / the big hartbeklemmingeen grote hartbeklemming, de grote hartbeklemming