[Natural history of mitral valve prolapse with respect to the heart size and ventricular arrhythmias]. 
To evaluate the evolution of mitral valve prolapse (MVP) with increasing age, 158 patients were studied by two-dimensional echocardiography and 24-hour ambulatory electrocardiography (Holter monitoring).  The patients were divided into seven age groups (25 patients ranging in age from 12 to 14 years, 21 from 15 to 17, 24 from 18 to 20, 24 from 21 to 30, 37 from 31 to 50, 8 from 51 to 60 and 19 older than 61).  Each patient was echocardiographically graded as mild, moderate and severe MVP.  Ventricular arrhythmia by Holter monitoring was graded as I, II, III and IV according to Lown et al.  The following results were obtained.  1.  Incidence of moderate and severe MVP was less than 10% in patients younger than 20 years, but increased with age.  Incidence of left ventricular dilatation (left ventricular end-diastolic dimension less than or equal to 55 mm) and left atrial dilatation (left atrial dimension greater than or equal to 40 mm) were minimal in patients younger than 20 years, but increased with age, especially in patients older than 51 years.  2.  Ventricular couplets or triplets (Lown grade IV) were found in less than 10% in patients in age from 15 to 17 years, 33% in patients from 18 to 20 years and showed no increase with age.  The rate of ventricular tachycardia was over 150 beat per min (bpm) in five of nine patients (56%), and the sinus rate preceding ventricular tachycardia was from 65 to 140 bpm.