Three facets of the study need attention

BMJ 1996; 313 doi: https://doi.org/10.1136/bmj.313.7064.1081d (Published 26 October 1996) Cite this as: BMJ 1996;313:1081
  1. Krishna Prasad, Clinical research fellow,
  2. Marek Malik, Professor of biomathematics,
  3. Boaz Mendzelevski
  1. Department of Cardiological Sciences, St George's Hospital Medical School, London SW17 0RE
  2. Department of Cardiology, Royal Brompton Hospital, London

    EDITOR,—Darwood Darbar and colleagues showed the predictive value of QTc dispersion (>/=60 ms) in patients with peripheral vascular disease,1 but we think that three parts of this paper need attention.

    The first is the patient population. This small, retrospective study was not controlled for risk factors, which introduces significant selection bias. Patients with peripheral arterial disease have a higher incidence of coronary artery disease and its complications. Ischaemic burden (symptomatic or asymptomatic) and the severity of coronary stenosis influences prognosis.2 Mean ejection fraction is useful, but in individual patients the above …

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