Dynamically accessing columns from a row type in a trigger

Greetings all,

I am writing a trigger and would like to know how to dynamically
access a column from the "OLD" variable. pk_col is the column name
from the table.

I've come up with either doing this:
EXECUTE format('SELECT $1.%1$I', pk_col) INTO pk_val USING OLD;

which looks a bit excessive, or this

pk_val = to_jsonb(OLD.*)->pk_col

which looks cleaner, but then I am having to incur a little overhead
by using the to_jsonb function. Ideally, something like this would be
great:

pk_val = OLD[pk_col]

but evidently we can't subscript ROW types.

Am I missing out on a simpler or more elegant solution?

Rhys
Peace & Love | Live Long & Prosper