cardiac pacemaker(n = noun.body) pacemaker, sa node, sinoatrial node - a specialized bit of heart tissue that controls the heartbeat;
is a kind of cardiac muscle, heart muscle

area of cardiac dullness, artificial pacemaker, cardiac, cardiac arrest, cardiac arrhythmia, cardiac cycle, cardiac glucoside, cardiac glycoside, cardiac insufficiency, cardiac massage, cardiac monitor, cardiac murmur, cardiac muscle, cardiac output, cardiac plexus, cardiac resuscitation, cardiac rhythm, cardiac sphincter, cardiac tamponade, cardiac valve, pacemaker