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Original research article
Impact of surgery on presence and dimensions of anatomical isthmuses in tetralogy of Fallot

Abstract

Objective In tetralogy of Fallot (TOF), the dominant ventricular tachycardia substrates are slow-conducting anatomical isthmuses. Surgical correction has evolved, which might have influenced isthmus presence and dimensions.

Methods One hundred and forty-two postmortem TOF specimens (84/58 corrected/uncorrected) were studied for isthmus presence. Isthmus 1 is located between the tricuspid annulus and right ventricular (RV) outflow tract (RVOT) patch/RV incision, isthmus 2 between RVOT patch/RV incision and pulmonary valve, isthmus 3 between pulmonary valve and ventricular septal defect (patch), isthmus 4 between ventricular septal defect (patch) and tricuspid annulus. Isthmus width and thickness were measured.

Results Of 84 corrected postmortem TOF specimens (death: 6.6 years (4.0–11.5)), 83 demonstrated isthmus 1 (99%, width=25±10 mm, thickness=5±2 mm), 35 isthmus 2 (42%, width=10±9 mm, thickness=3±2 mm), 83 isthmus 3 (99%, width=10±6 mm, thickness=5±2 mm), and 5 isthmus 4 (6%, width=4±2 mm, thickness=2±1 mm). Transatrial-transpulmonary correction (n=49) as compared with transventricular correction (n=35) prevented isthmus 2 (0% vs 100%, P<0.001). Transatrial-transpulmonary correction at age <1 year (n=7) as compared with ≥1 year (n=42) required a smaller transannular RVOT patch (28±15 vs 45±14 mm, P<0.001). Mode and timing of correction did not influence presence and dimensions of isthmus 3. In corrected and uncorrected TOF specimens (death 1.8 years (0.5–6.6)), the range of isthmus 3 dimensions was broad (width: min=2 mm, max=32 mm; thickness: min=1, max 13 mm) across all ages. Isthmus 3 width and thickness were strongly correlated (r=0.65, P<0.001).

Conclusions In TOF, the current routine use of transatrial-transpulmonary correction prevents isthmus 2. Correction <1 year reduces transannular patch size, which may influence isthmus 1 width later in life. Mode and timing of correction did not change prevalence and dimensions of isthmus 3, in which dimensions varied widely in uncorrected and corrected TOF.

  • congenital heart disease
  • tetralogy of Fallot
  • ventricular tachycardia
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