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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Contributors GFLK: conceived and designed the research, acquired data, performed statistical analysis, drafted the manuscript, made critical revision of the manuscript for intellectual content, responsible for the overall content as guarantor, submitted the study. SL: conceived and designed the research, acquired data, performed statistical analysis, made critical revision of the manuscript for intellectual content. NAB and MGH: conceived and designed the research, made critical revision of the manuscript for intellectual content. MJS: made critical revision of the manuscript for intellectual content. MMB: conceived and designed the research, acquired data, made critical revision of the manuscript for intellectual content. MRMJ and KZ: conceived and designed the research, performed statistical analysis, drafted the manuscript, made critical revision of the manuscript for intellectual content, handled supervision, responsible for the overall content as guarantor.
Funding The Department of Cardiology Leiden receives unrestricted research and fellowship grants from Edward Lifesciences, Boston Scientific, Medtronic and Biotronik.
Competing interests None declared.
Ethics approval This study was undertaken in accordance with the local ethics committee and the Dutch regulation for the proper use of human tissue for medical research purposes.
Provenance and peer review Not commissioned; externally peer reviewed.
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