title: Histopathology of the right ventricular outflow tract and its relationship to clinical outcomes and arrhythmias in patients with tetralogy of Fallot.
abstract: OBJECTIVE
  The purposes of this study were to evaluate the myocardial histopathology and ultrastructure in patients with tetralogy of Fallot and to identify the histopathologic characteristics that may predispose patients to postoperative myocardial dysfunction and arrhythmias.
  
  
  METHODS
  Operatively resected crista supraventricularis muscle from 183 patients undergoing intracardiac repair of tetralogy of Fallot aged 12 months to 42 years (mean, 106.84 +/- 79.35 months) were studied by light and electron microscopy. Biventricular function and cardiac rhythm were assessed by 2-dimensional echocardiography and electrocardiography.
  
  
  RESULTS
  The incidence of moderate or severe cellular hypertrophy, endocardial thickening, and interstitial fibrosis was 36%, 68.3%, and 65%, respectively. Logistic regression analysis demonstrated age greater than 4 years, systemic arterial desaturation, higher hematocrit values, and elevated ventricular end-diastolic pressures as the major predisposing risk factors for pathologic changes. Twenty-seven (81.8%) patients more than 15 years of age and 29 (29.3%) patients between 4 and 15 years of age had predominant right ventricular dysfunction and low cardiac output (chi(2) [1 degree of freedom (df)] = 27.95; P < .001; odds ratio [OR] = 10.86 [3.75-33.10]). Ventricular arrhythmia was detected in 11 patients in whom repair was performed between 4 and 15 years of age and in 13 patients whose age at operation was 15 years or older. According to an additive logistic model, the effect of age at repair on the influence of ventricular arrhythmia was significant (chi(2) [1 df] = 24.4; P < .001; OR = 8.21 (2.96-23.11]).
  
  
  CONCLUSIONS
  The great majority of myocardial tissues in cyanotic tetralogy of Fallot indicates pre-existing ultrastructural hypertrophic and degenerative changes. The changes are more pronounced in older patients subjected to long-standing cyanosis and pressure overload and may account for or may coexist with the higher incidence of myocardial dysfunction and ventricular arrhythmia.
authors.affiliation: Cardiothoracic Centre, Department of Cardiothoracic and Vascular Surgery, All India Institute of Medical Sciences, New Delhi, India. ujjwalchow@rediffmail.com
authors.forename: Ujjwal K
authors.initials: UK
authors.lastname: Chowdhury
authors.forename: Siddharth
authors.initials: S
authors.lastname: Sathia
authors.forename: Ruma
authors.initials: R
authors.lastname: Ray
authors.forename: Rajvir
authors.initials: R
authors.lastname: Singh
authors.forename: Kizakke K
authors.initials: KK
authors.lastname: Pradeep
authors.forename: Panangipalli
authors.initials: P
authors.lastname: Venugopal
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D001145:Arrhythmias, Cardiac / Q000473:pathology*; D002303:Cardiac Output, Low / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D004699:Endocardium / Q000473:pathology; D004719:Endomyocardial Fibrosis / Q000453:epidemiology / Q000473:pathology; D005260:Female; D005355:Fibrosis; D006801:Humans; D006984:Hypertrophy; D007223:Infant; D016015:Logistic Models; D008297:Male; D009206:Myocardium / Q000473:pathology* / Q000648:ultrastructure; D032383:Myocytes, Cardiac / Q000473:pathology; D011183:Postoperative Complications / Q000453:epidemiology; D011446:Prospective Studies; D012307:Risk Factors; D013771:Tetralogy of Fallot / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery*; D016896:Treatment Outcome; D014463:Ultrasonography; D018497:Ventricular Dysfunction, Right / Q000473:pathology