Atrioventricular nodal function inprogressive systemic sclerosis: electrophysiolog

dataconsistent withatrioventricular nodaldysfunction were obtained in10outof19patients withprogressive systemic sclerosis (scleroderma). Conducting system studies werecarried outinafurther sevenpatients withprogressive systemic sclerosis. Ineachtheproximal portion oftheatrioventricular node wasconsistently found tobesmaller andmore slender. It is postulated thatthere isa relation between proximal atrioventricular nodalstructural alterations andimpaired atrioventrPcular nodal function. Conducting systemdisorders arefoundinprogressive systemic sclerosis.'-3 First degree atrioventricular blockoccurred inasmanyas20per centofpatients inoneofthese series2 andinall three series there wasatleast onecase withcomplete atrioventricular block. Inanadditional caseof progressive systemic sclerosis withcomplete heart block, atnecropsy theatrioventricular nodewas foundtobefused withthecentral fibrous bodyof theheart. Atthebifurcation ofthebundle there wasanacutedegenerative change andthere was fibrosis oftheright bundle.4 Inanecropsy study of eight further patients James5 observed thatbefore deathatleast fiveofthemhadhadsignificant conducting systemdisease localised attheatrioventricular nodeorbundle ofHis, asjudged bythe electrocardiogram, andthatineachtherewere severemorphological abnormalities present at these sites andatthesinus node.Hefelt thatthe normal difference incollagen content between the sinus nodeontheonehandandtheatrioventricular nodejunctional tissues ontheother maypartially explain whyfibrosis wassomuchmoreconspicuous intheformer. Heconcluded that acombination of sinusnodedestruction andexcessfocal fibrotic partitioning intheatrioventricular junction was thelikely basis forahighfrequency ofparoxysmal supraventricular tachycardia, theelectrophysiological consequences beingfailure ofnormal automaticity together withtheavailability of multiple anatomical routesforatrioventricular junctional re-entry. Thoughtheseries ofRidolfi