Binary vascular system A binary vascular system was a type of circulatory system in which the blood vessels led to two heart s . Time Lord s had a binary vascular system . ( TV : " Spearhead from Space " , et al ) Characteristics . According to the Twelfth Doctor , a binary vascular system led to extremely high blood pressure in comparison to single - hearted species like human s . ( TV : " Smile " ) The Dominator Rago once told Jamie McCrimmon that beings with single hearts were physically weaker than those with two hearts . ( TV : " The Dominators " ) When the Fifth Doctor was stabbed in the chest , he survived because his human , single - hearted attacker aimed for the spot where the human heart would be , but the Doctor ' s two hearts were in a slightly different location . ( AUDIO : " Son of the Dragon " ) Scans of the Ninth Doctor ' s hearts and later the Eleventh Doctor ' s hearts showed that the hearts changed position during regeneration at some point . ( TV : " Dalek " , " The Power of Three " ) A Gallifreyan in cardiac arrest needed CPR on both hearts ; otherwise , it would prove ineffective . ( TV : " Smith and Jones " ) Amy Pond used a defibrillator to restart one of the Eleventh Doctor ' s hearts . ( TV : " The Power of Three " ) Cybermen could detect a binary vascular system , prompting them to take the subject for further analysis , which at least delayed cyber - conversion . ( TV : " The Age of Steel " ) In Time Lords . A Time Lord ' s regenerative process was intimately linked to his or her hearts . Time Lords from Oldblood House s had only one heart until they regenerated for the first time ; ( PROSE : " The Man in the Velvet Mask " , " Christmas on a Rational Planet " , AUDIO : " Time in Office " ) the First Doctor was seen to have one heart . ( TV : " The Edge of Destruction " ) In contrast , members of Newblood Houses were Loom ed with both hearts . ( PROSE : " Christmas on a Rational Planet " ) Regeneration could be completely stopped — and the Time Lord therefore killed immediately , regardless of how many lives they had left — if both hearts were pierced or shot simultaneously . Andred and Serena were both killed in this manner , ( AUDIO : " Imperiatrix " , PROSE : " World Game " ) while Cavis was permanently killed when , during regeneration , her enemy stabbed both her original heart and the place where the second one would grow . ( PROSE : " The Shadows of Avalon " ) Brooke of the Kovarian Chapter carried a regeneration inhibitor firearm capable of producing double blasts to take out a binary vascular system , which she used to kill H - One . ( AUDIO : " The Furies " ) recommended eight sniper s , with three trained on each of her hearts and two for her brain stem , so that Clara Oswald could feel safe while speaking to her , noting that they ' d have to " switch [ her ] off fast " before she could regenerate . ( TV : " The Magician ' s Apprentice " ) A Gallifreyan could survive with only one heart , though he or she would be weakened greatly . ( PROSE : " Managra " , TV : " The Shakespeare Code " , AUDIO : " City of Spires " ) When one of the Third Doctor ' s hearts momentarily stopped , warned him he was " within an inch of dying . " ( TV : " The Mind of Evil " ) After the Eighth Doctor ' s second heart was extracted from his chest , he was unable to process drug s or use his respiratory bypass system , and to compensate , his remaining heart had to beat at a worryingly rapid pulse and was prone to fatigue . ( PROSE : " The Adventuress of Henrietta Street " , " Hope " , " Anachrophobia " ) During the Last Great Time War , at least one Time Lord spy had her second heart removed from her body . ( AUDIO : " A Heart on Both Sides " ) One of the Tenth Doctor ' s hearts stopped beating while he was recovering from regeneration , ( TV : " The Christmas Invasion " ) and the Eleventh Doctor claimed that he wouldn ' t survive much longer after one of his hearts was stopped by a Shakri cube . ( TV : " The Power of Three " ) When Sabbath implanted the Eighth Doctor ' s second heart in his own chest , it endowed him with the ability to penetrate " deep time " ( ie , travelling further away from his homeworld than should be possible ) , simultaneously creating a link between the Doctor and Sabbath that meant that the Doctor would survive grievous wounds as his heart was still beating in Sabbath , until Sabbath tore the heart out of his own chest , its ' death ' allowing the Doctor to grow a new one . ( PROSE : " The Adventuress of Henrietta Street " , " Hope " , " Camera Obscura " ) In other species . As Time Lords from an alternate timeline , the Word Lord s also had a binary vascular system . ( AUDIO : " The Word Lord " ) In the Mutter ' s Spiral galaxy , a few monopod species and a drone species had two hearts . ( PROSE : " Tragedy Day " ) The Second Doctor once encountered another double - hearted humanoid species called the Dulcian s . His own binary vascular system led the Dominator s to believe he was a Dulcian . ( TV : " The Dominators " ) Later , the Eighth Doctor met the Kulan , another race whose overall stamina seemed to be improved over human s by their two hearts . ( PROSE : " Escape Velocity " ) The Kirithon s were genetically engineered by the Panjistri to have two hearts . ( PROSE : " " ) The Apalapucian s , residents of Apalapucia , had two hearts . Chen - 7 , also known as the 1 Day Plague , only affected species with binary vascular systems . ( TV : " The Girl Who Waited " ) The inhabitants of Skale had two hearts . ( PROSE : " Parallel 59 " ) When Henry van Statten performed an invasive scan of the Ninth Doctor in 2012 , he marvelled at the design and enthusiastically announced he was going to patent it . ( TV : " Dalek " ) Humans genetically introduced a second heart many Segments prior to circa 10 , 000 , 000 . ( PROSE : " The Ark " ) Baris , a fan of the Tenth Doctor , had a second heart fitted so he could resemble him more . ( PROSE : " The Doctor Trap " )