How many times does the heart beat in one minute?

$A$: The cardiac impulse which originates from $SA$ node in mammalian heart cannot spread directly from atria to ventricles.
$R$: In mammalian heart there is no continuity between cardiac muscle fibres of atria and those of ventricles except $AV$ bundles.

Average cardiac output is

The cardiac pacemaker in a patient fails to function normally. The doctors find that an artificial pacemaker is to be grafted in him. It is likely that it will be grafted at the site of

If the pacemaker is absent,what will happen?

Chordae tendinae