What is agonal Rhythm ?

An agonal rhythm is a slow ventricular rhythm.  , characterized by unusually wide and bizarre ventricular complexes, often seen in moribund patients.
Agonal rhythm is a bizarre wide QRS rhythm, often seen pre-terminally during cardiac resuscitation. It is an extremely slow ventricular rhythm and often indicates dismal outcome. No P waves are seen preceding the QRS complexes. The wide bizarre QRS indicates severe myocardial damage.

If you see  any rhythm that is …prior to the heart giving out or going into Asystole or ‘flat line’.

It is the last stage before asystole and could be considered to be asystole with occasional beats.  It often has no pulse or blood pressure because the heart is so weak that it cannot contract with enough force to generate a palpable pulse.  This rhythm has similarities to an idioventricular rhythm.  The differences are that an idioventricular rhythm is not a dying heart and can sometimes produce a strong pulse.

 An idioventricular rhythm will occur at a rate that is equal to the intrinsic rate of the ventricular pacemaker, which is 20-40 while an agonal rhythm can be much slower and even less than 10 beats per minute.  The QRS complex of an agonal rhythm is usually very wide and could be wider than an idioventricular rhythm.    An agonal rhythm is from a dying heart and is 99+% of the time, not recoverable.