Canadian Journal of Cardiology



      Congenital long QT syndrome (LQTS) is a channelopathy associated with syncope, polymorphic VT, and rarely, sudden arrhythmic death. While often detected by QT prolongation on the resting ECG, half of patients have a normal or borderline QT interval, necessitating further investigations (i.e. exercise treadmill and genetic testing). We aimed to develop a deep neural network for identification of congenital LQTS and differentiate LQTS genotypes using both the resting single-lead and 12-lead ECGs.

      Methods and Results

      Patients with LQTS type 1, type 2, and unaffected family members were prospectively enrolled in a national LQTS registry. For each patient’s ECG, normalized voltages for the 8 non-augmented leads were down-sampled to 102.4 Hz over 10 seconds. Lead I was evaluated independently, followed by a combined analysis using the 8 non-augmented leads. For each task, we trained convolutional neural networks (Scikit-Learn v1.0.1, Keras v2.6.0, TensorFlow v2.6.0, Figure 1). Data was split into a training (80%) and testing dataset (20%). Model performance was assessed on an independent dataset to which the models were blinded during training. 149 LQTS (Type 1 n=105, Type 2 n=44) and 74 control patients were included, with a mean age of 47±18 years, 57% female. On resting ECG, the heart rate and corrected QT interval was 66±13 bpm and 468±36 msec in LQTS patients, and 74±15bpm and 423±24 msec in control patients. After training, the model was able to identify congenital LQTS with an area under the curve (AUC) of 0.71, sensitivity 53%, and specificity 83% using lead I alone. Using the full ECG (8 non-augmented leads combined), the model identified congenital LQTS with an AUC of 0.83, sensitivity 87%, and specificity 73% (Figure 2A-B). For patients with normal baseline QTc ( < 480 ms in females and < 470 ms in males, n=30), the model had comparable performance with an AUC of 0.85, sensitivity 87%, and specificity 80% (Figure 2C). Additional analyses demonstrated moderate accuracy in differentiating LQTS genotypes (AUC 0.76, sensitivity 57%, specificity 100%; Figure 2D).


      Deep neural networks can be employed for the detection of congenital LQTS on ECG with moderate accuracy using a single-lead ECG alone, and good accuracy with a full 12-lead ECG (8 non-augmented leads). Future work includes developing a model to incorporate additional demographics and to effectively distinguish between LQTS. Deep neural networks are promising methodology for identifying LQTS and differentiating LQTS genotypes using ECG alone.
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