MECHANOELECTRICAL INTERACTION IN TETRALOGY OF FALLOT - QRS PROLONGATION RELATES TO RIGHT-VENTRICULAR SIZE AND PREDICTS MALIGNANT VENTRICULAR ARRHYTHMIAS AND SUDDEN-DEATH

Background Life-threatening ventricular arrhythmia and sudden death re main serious late complications after tetralogy of Fallot repair. Neve rtheless, 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 Fallo t repair who were currently attending our clinic. Mechanoelectrical re lations were sought in 41 of the patients (mean follow-up, 23.6 years) who were operated on by one surgeon and who were prospectively studie d with a 12-lead EGG, chest radiography, and two-dimensional and Doppl er echocardiography. Nine patients (mean follow-up, 17 years) from the total group of 178 were identified as having had sustained ventricula r 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 postope rative sudden cardiac death also were available for review. QRS durati on in the 41 patients in whom mechanoelectrical interaction was sought ranged between 90 and 200 milliseconds and correlated with cardiothor acic ratio (CTR) on chest radiography (r=.64, P<.001) and with right v entricular size on echocardiography (r=.43, P<.02). Twenty of the 41 p atients had restrictive right ventricular Doppler physiology (reduced ventricular compliance) with mean QRS duration of 129.3+/-20 milliseco nds and mean CTR of 0.51+/-0.03. The remaining 21 patients with no evi dence of right ventricular restriction had prolonged QRS duration of 1 57.5+/-13.2 milliseconds (P<.001) and CTR of 0.55+/-0.04 (P<.04) compa red with the restrictive. In the 9 patients with ventricular tachycard ia, 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 witho ut life-threatening arrhythmias). All patients with documented sustain ed ventricular tachycardia and the 4 patients with sudden death had a QRS duration of greater than or equal to 180 milliseconds (100% sensit ivity). Conclusions Chronic right ventricular volume overload after te tralogy of Fallot repair is related to diastolic function and correlat es with QRS prolongation. The risk of symptomatic arrhythmia is high w hen marked right ventricular enlargement and QRS prolongation develop. A QRS duration on the resting ECG of greater than or equal to 180 mil liseconds is the most sensitive predictor of life-threatening ventricu lar arrhythmias yet described.