Dear Editor,

We read with interest the article by Gervais et al.,1 who compared QT interval length in a group of young subjects who had been born preterm <30 weeks of gestation with that in their healthy peers born full term. Using exercise stress test on a cycle ergometer, they did not found any significant difference in QT tract corrected for heart rate (QTc)—a well established marker of potential development of ventricular arrhythmias—between the two groups. So, in the Authors’ opinion, avoidance of QT-prolonging medications in individuals born preterm is not supported by scientific evidence. These suggestions are decidedly in contrast with those proposed by our research group a few years ago.2 However, in our opinion, several additional issues should be considered when interpreting their results, namely:

  • Marked difference in gender distribution. In our sample size, 83.3% of the recruited patients were female, while only 38.7% in the study by Gervais. This striking difference is likely to have influenced the results. In fact, it is well known that QTc in the female gender is longer than in males. This disparity in recruiting patients was due to the fact that in the initial stages of neonatal intensive care, in Italy a considerably higher number of preterm female infants survived for reasons still to be clarified.2

  • The impact of posture. When an exercise stress test is done on a cycle ergometer, the patient is in a sitting position. It often leads to the appearance of signal artifacts which make the ECG difficult to interpret. Objectively, it is not easy to discriminate the ECG curves and make sophisticated calculation, QTc included. Mistakes are quite frequent.3 Interestingly, the Authors reported the same QTc value in both groups at peak exercise (387 ms) as well as the same standard deviation (34–35 ms) at baseline/peak exercise/post recovery regarding preterm group. Again, the same QTc (409 ms) is at baseline and at minute 3 of recovery in the control group! This sequence of coincidences appears somewhat unlikely from a statistical standpoint and raises serious concerns in relation to the accuracy in measuring QT tract.

  • Different genetic background between the two populations, as honestly pointed out by the Authors. The inhabitants of the island of Sardinia in Italy constitute an “ethnic group” and a genetically determined predisposition to QT prolongation cannot be excluded at all.4

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