Mechanoelectrical Interaction in Tetralogy of Fallot

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Abstract
Background Life-threatening ventricular arrhythmia and sudden death remain serious late complications after tetralogy of Fallot repair. Nevertheless, there remains no clear way of predicting which patients are at risk. Methods and Results The study population included a total of 178 adult survivors (mean follow-up, 21.4 years) of tetralogy of Fallot repair who were currently attending our clinic. Mechanoelectrical relations were sought in 41 of the patients (mean follow-up, 23.6 years) who were operated on by one surgeon and who were prospectively studied with a 12-lead ECG, chest radiography, and two-dimensional and Doppler echocardiography. Nine patients (mean follow-up, 17 years) from the total group of 178 were identified as having had sustained ventricular tachycardia (8 with near-miss sudden death), and their ECGs, Holter monitor readings, electrophysiological studies, and chest radiographs were reviewed. The case notes of an additional 4 patients with postoperative sudden cardiac death also were available for review. QRS duration in the 41 patients in whom mechanoelectrical interaction was sought ranged between 90 and 200 milliseconds and correlated with cardiothoracic ratio (CTR) on chest radiography ( r =.64, P <.001) and with right ventricular size on echocardiography ( r =.43, P <.02). Twenty of the 41 patients had restrictive right ventricular Doppler physiology (reduced ventricular compliance) with mean QRS duration of 129.3±20 milliseconds and mean CTR of 0.51±0.03. The remaining 21 patients with no evidence of right ventricular restriction had prolonged QRS duration of 157.5±13.2 milliseconds ( P <.001) and CTR of 0.55±0.04 ( P <.04) compared with the restrictive. In the 9 patients with ventricular tachycardia, the QRS duration ranged from 180 to 230 milliseconds (mean, 198.9±17.6 milliseconds), and the CTR ranged from 0.54 to 0.9 (mean, 0.67±0.12) ( P <.0001 and P <.01, respectively, compared with patients without life-threatening arrhythmias). All patients with documented sustained ventricular tachycardia and the 4 patients with sudden death had a QRS duration of ≥180 milliseconds (100% sensitivity). Conclusions Chronic right ventricular volume overload after tetralogy of Fallot repair is related to diastolic function and correlates with QRS prolongation. The risk of symptomatic arrhythmia is high when marked right ventricular enlargement and QRS prolongation develop. A QRS duration on the resting ECG of ≥180 milliseconds is the most sensitive predictor of life-threatening ventricular arrhythmias yet described.