1. Variance electrocardiography is a new resting procedure for the detection of ischaemia-induced variability in the electrical expression of the depolarization phase. The analysis is performed on 220 cardiac cycles using high-fidelity ECG signals from 24 leads, and the electrical variability is expressed as an electrical variability index ranging from 1 to 150. In this study, variance electrocardiography was employed to detect cardiac involvement in 23 patients with cystic fibrosis.

2. Patients with cystic fibrosis presented a significantly higher mean electrical variability index than control subjects, and their index values correlated inversely with the arterial oxygen partial pressure and forced expiratory volume in 1.0 s. Patients with a high electrical variability index (> 75) displayed a lower clinical score (Shwachman score) and a longer duration of chronic colonization with Pseudomonas aeruginosa. Patients with conduction disturbances and patients with echocardiographic right ventricular pathology presented higher indices than those without.

3. Electrical variability index is increased in cystic fibrosis and correlates with other signs of cardiac and pulmonary derangement. Variance electrocardiography may therefore have the potential to be a sensitive and simple method for monitoring cardiac involvement in this disease.

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