Human use conditions in fatigue of intravenous leads used in cardiac implanted electronic devices.

BACKGROUND

Transvenous lead conductors are subject to fatigue fracture from repetitive bending stresses, which are proportional to alternating curvature. A prerequisite for developing a valid preclinical lead-testing standard is knowledge of the stresses on implanted leads - their fatigue environment, but little is known about it.

OBJECTIVE

The Human Use Condition Study (HUCS) quantified this fatigue environment, including the relationship between lead stiffness and alternating curvature.

METHODS

HUCS was a prospective, observational, multicenter clinical study. Leads from 4 manufacturers were chosen to span the range of stiffness in clinical use. They were imaged using biplane cinefluoroscopy during cardiac motion and in the shoulder region during arm motion. In each image, the lead was traced, and its curvature was calculated as a function of time.

RESULTS

Images were analyzed for 109 subjects. In each region of the lead analyzed, maximum alternating curvature was determined primarily by between-patient differences, not differences in lead stiffness. Across regions, maximum alternating curvature was greatest in the extravenous region (P = .001). In this region, the length of the highly stressed portion of the lead correlated inversely with lead stiffness (P < .001).

CONCLUSION

HUCS is the first study to measure alternating in vivo stresses applied to leads from multiple manufacturers that spanned a range of stiffnesses and thereby enable the development of an evidence-based lead-testing standard. The greatest alternating stress occurs in the extravenous region. There, lead stiffness predicts how much of the lead is highly stressed but does not predict maximum alternating curvature.