CONGENITAL HEART BLOCK WITH DEXTROCARDIA BY DUNCAN LEYS Fl-om t h e Highlands a n d Islands Medical Service Received July 1 2 , 1942 Stein a n d U h r (1941), describing congenital heart block in a girl of 3 , bring t h e total o f reported cases t o 5 5 . Apparently t h e number that are recognized a n d reported i s still n o t great, since Campbell a n d Suzman (1934) analysed 5 3 which they accepted a fulfilling t h e criteria of diagnosis. Associated anatomical defects of t h e heart always seem t o b e present, and, a s might b e expected, septal defects ar e common, i f n o t invariable. I t ha s n o t been suggested that a n y case o f incomplete heart block i s congenital: a n d transient heart block i s, o f course, common enough i n t h e acute infections, b u t i f i t should become complete, th e patient usually dies. Fishberg (1940) s aw one patient w h o survived with complete block that w a s apparently d u e t o diphtheria, a n d quotes Stechner's study of 1 9 others, a l l o f whom died. White (1937) thinks acquired cases apart from coronary disease are rare. Th e a g e o f t h e patient i s therefore a fair indication of t h e etiology o f complete heart block that persists, i.e. coronary disease i n middle a ge a n d congenital defect i n childhood a n d early adult life, a nd this rule will b e subject t o f e w exceptions. Writers have rather tended t o insist that t h e cause o f complete heart block i n children young adults should be assumed to b e infection unless there i s proof o f its congenital origin, a n d Yater (1939) gives several criteria f o r t h e diagnosis. I t seems likely, however, that most, i f no t all, cases of complete heart block in children a n d young adults ar e congenital, a n d t h e mere history o f a severe infectious disease i s no proof o f oetiology. There must be few children i n whom a history o f o n e o r other of t h e infectious diseases cannot b e discovered, a n d one would need t o have seen t h e appearance of block during h e course o f t h e infection t o assume that this h a d been responsible. Such a n observation, o f course, ha s often been made i n diphtheria, b u t survival after i t s appearance must be rare. T h e existence of any other evidence o f congenital heart disease would b e strong presumptive evidence that t h e heart block w a s also con- genital. F o r example, Bower (1939) reports t w o cases as discovered after severe measles, bu t both h ad systolic murmurs that were probably d u e t o septal defect. A case of congenital heart block, with dextrocardia a s part o f a complete transposition o f viscera, i s here reported; s h e ha d t h e further peculiarity that s h e came under m y notice with a n acute primary tuberculous infection, a n d later developed extensive pulmonary tuberculosis, which, however, shows a strong tendency t o heal. Th e association of complete heart block with dextrocardia must b e very rare; I have only found reference t o o n e other case (Yater, 1929). My patient h a d also t h e signs o f septal defect. Brown (1939), making a rather narrower selection o f cases o f complete heart block than that o f Campbell a n d Suzman (1934), accepts 4 4 a s being congenital, o f which 27 h a d clear signs o f a septal defect, confirmed i n 5 b y autopsy. H e considers t h e rarity o f congenital complete heart block fully explained b y t h e fact that the A- V bundle develops i n t h e feetus before t h e formation o f t h e septum, s o that a defective septum i s unlikely t o interfere with conduction. Th e heart rate is n o t s o slow as it i s i n adult acquired block, an d ma y increase t o 8 0 under certain conditions. Th e ordinary ventricular rate a t rest i s usually about 5 0 ; i t i s more easily increased by stimuli than acquired heart block, a n d this explains why, unless a special search i s being made f o r such cases, t h e condition ma y easily b e overlooked. T h e subjects o f congenital heart block ma y pass through a medical examination without t h e block being discovered. Case Notes. H . G . , aged 2 0 , w a s admitted to the Royal Northern Infirmary o n July 1 1 , 1939. Three weeks before, there h a d been a n eruption o n t h e legs described a s " a few small hard r e d tender spots," a n d at t h e same time s h e h a d pain in t h e legs o n movement; a week after this s h e h a d a succession o f rigors a n d a pain i n h er chest with some shortness o f breath. I t h a d been known f o r some years that s h e h ad dextrocardia, an d exertion h a d always made h e r breathless a n d cyanosed. There w a s n o history o f a n y relative having been affected i n t h e same way. T h e parents were n o t related a n d h a d neither dextrocardia n o r heart block. Information about other sibs w a s merely second-hand from t h e girl's mother, i.e. s h e h a d never heard of a n y congenital heart peculiarity. 8
