PubMed1980
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 .