mitral valve prolapse ( mvp ) , responsible for most of the symptoms which had previously been interpreted as being due to neurocirculatory disorders or cardiac neurosis , is being recognised more often and has an incidence of about 6-8 % in an unselected population . although this condition was considered for a long time to be a benign auscultatory abnormality , it may be the cause of serious cardiac complication . arrhythmias predominate with an incidence of 60 to 80 % on continuous electrocardiography . in a series of 245 patients with mitral valve prolapse confirmed on echocardiography , 52 patients chosen at random were studied to determine the incidence pf st changes , disturbances of heart rate , qt interval , changes of qrs , arrhythmias with resting , exercise and continuous ecg over 24 hours ( hms = holter monitoring system ) . abnormalities of ventricular repolarisation , especially flattening of the t wave and , less commonly , st depression were observed in about one third of the patients . these changes were more common in the inferior but were also found in the left precordial leads . 73 % of the 52 patients had a heart rate of 75/mn and their qt intervals showed the following changes : 30.7 % had a duration greater than the 120 th percentile ; 19.2 % had a duration greater than the upper limit of normal . the other 50 % had a qt interval of around the 100 th percentile . none had a duration of less than the 90 th percentile . in 22.5 % patients , qrs changes due to conduction defects were recorded ( 15 % right bundle branch block - rbbb - , 7.5 % incomplete rbbb ) . hms is the method of choice for detection of arrhythmias . resting ecg only showed premature ventricular contractions ( pvcs ) in 12.5 % , compared to 32.5 % on exercise ecg and 62.5 % on hms . 50 % pvcs were monomorphic , 5 % polymorphic , 7.5 % in salvos and 7.4 % supraventricular in origin . the circadian variation of pvc was striking with a high incidence during periods of activity . there was no statistical correlation between the incidence of pvcs , age , sex , type of mvp and the symptoms and auscultatory findings . the theories on the pathogenesis of the arrhythmias are divided between that based on an underlying cardiomyopathy ( confirmed by the presence of degenerated myocytes on electron microscopy ) and the mechanical hypothesis ( chordae tendinae irritating the endocardium or traction on the papillary muscle with resulting ischaemia ) which provide a better explanation of the clear predominance of monomorphic pvcs . the treatment of barlow 's syndrome is discussed . in our opininon , therapy is only required for ventricular arrhythmias detected by a sufficiently sensitive method such as hms . most authors use beta blockers , eventually in association with quinidine therapeutic successes have also been observed with mexiletine , amiodarone , aprindine and less commonly with disopyramide .
C0003811
arrhythmias
C0085612
ventricular arrhythmias