Isaac's Heart

Isaac's Heart is an unlockable passive item.

Effects

 * Isaac's body becomes immune to all damage.
 * A heart familiar appears and closely follows Isaac. If the heart is hurt, Isaac is hurt.
 * The heart tries to position itself in the opposite direction of where Isaac is shooting.
 * The heart charges up as Isaac fires. At full charge, upon releasing the fire button, it knocks back nearby enemies and tears, creates a small puddle of red creep on the ground, and releases blood shots in 8 directions that deal 8 damage.
 * Enemies that come in contact with Isaac take 7 damage over 2-3 ticks per second.
 * Most enemies now target the heart instead of Isaac. Eyes and other similar enemies, however, will still target Isaac.

Items / Trinkets

 * Items that activate on contact with enemies retain their ability, allowing Isaac to use them without suffering collision damage.
 * Items that hurt Isaac on activation, such as and  no longer do so, allowing infinite uses for free.
 * Get 5 cents as soon as possible so an Arcade can show up, Blood Donation Machines and are the best and most common ways to win Isaac's heart run.
 * If Lucky Pennies are unlocked, it may be beneficial to immediately try to gain 10 luck or more via the IV Bag to maximize room drops and enhance tear effects.
 * Speed up items are invaluable when having Isaac's heart since the delay between the player moving away and the heart moving as well gets drastically reduced. Avoid speed down items early in the run.
 * Orbital familiars are invaluable as Isaac can get extremely close to the enemy without fear of contact damage.
 * Flight items are invaluable as the heart can be placed over a rock and Isaac can stick out enough to shoot at enemies without needing spectral tears.
 * Angel Rooms are safer bets for items than Devil Rooms.

Combat and Damage

 * Hug obstacles to avoid taking damage. Look out for enemies that fly or can jump over rocks, and make sure enemies don't push Isaac far away from his heart to expose it.
 * When dodging, Isaac must move in semi-straight lines as the heart only follows Isaac's movements when he is at a certain distance away, for example, moving in a circle would pull the heart in and make it stay in place in the middle of the arc as Isaac would no longer be moving away from the heart. Moving in a triangle formation would allow the heart to move more.
 * Enemies that fly and charge like One Tooth are extremely hard to dodge and should be killed as soon as possible, take caution since they can appear as early as /.
 * Enemies can be pushed away with Isaac's body, while not recommended, it can be used as a last resort.

Synergies

 * : Box of Friends does not duplicate the heart, making it safe to use.
 * : Isaac can be infinitely invulnerable, as invincibility carries out to the heart without hurting the player. Note that the item needs to be activated for longer than one second for the invulnerability to kick in, however.
 * Duct Tape: Makes dodging significantly easier.
 * : Isaac can turn enemies into poop without taking damage.
 * : Invincibility carries over to the heart.
 * : The shield effect carries over to the heart.
 * : Can be used without taking damage, resulting in an infinite amount of coins.
 * : As long as the heart is away from the blast radius, no damage is taken. The character must be at high enough speed for this.
 * : Isaac cannot take damage from the Razor Blade, allowing for infinite uses of the item.
 * : Can remove the Isaac's Heart familiar while the item remains, making Isaac invulnerable. Sacrificial Altar now doesn't remove Isaac's heart and does not give a familiar.

Interactions

 * : Fires additional shots in random directions, and leaves larger puddles of creep.
 * / : If you have picked up either of the babies into the first familiar spot before Isaac's Heart, they will block enemy shots before they can hit the heart. Enemies touching the heart can still do damage, and picking up the babies after the heart will cause the heart's hitbox to be checked first against shots.
 * Gigante Bean: Increases the knockback amount and radius of the heart when fully charged. Highly useful.
 * : The Heart will follow King Baby. This makes it much harder to avoid damage, but also makes other synergies like much easier to use.
 * You can no longer pick up collectibles in the Store.
 * : Sharp Plug can no longer be used.
 * : Isaac's body repels projectiles, but Isaac's Heart doesn't.
 * Baby-Bender: The heart's tears do not gain homing.
 * : Not recommended. The heart follows Tainted Forgotten. Tainted Soul does not deal collision damage and can still be hurt by enemies. The heart will still damage Tainted Forgotten if hit by an enemy, effectively giving it two hitboxes.

Trivia

 * Isaac's Heart while it's following Isaac fittingly shares the same sprite as Child's Heart.
 * The nature of the item is similar to that of a Mask + Heart enemy.
 * This item is used in (challenge #30).

Seeds
TPWZ 7CVR (Treasure Room below of spawn) PCJZ 03TG 7BH9 T4DJ (Treasure Room adjacent to spawn) Y8V7 7K4F (Treasure Room adjacent to spawn) W1TD 0BJN (Treasure Room south of spawn)