The Centerline method provides a model of regional wall motion for use in clinical research and patient care. Its design avoids sources of variability such as reliance on a coordinate system based on identifying the apex.
Instead, a centerline is constructed midway between the traced endocardial LV contours at end diastole and end systole. Motion is measured along 100 chords drawn orthogonal to and evenly spaced along the centerline. Distances are normalized for heart size via the end-diastolic perimeter length, and converted to units of standard deviations from the mean of a normal reference population.
The average territories of the three major coronary arteries have been defined from population studies. Hypokinesis due to stenosis of one of these arteries is computed as the mean motion of chords lying within the most poorly contracting 50% of that artery's territory. Hyperkinesis can similarly be measured by focusing on the most energetically contracting chords. Thus the dysfunction is measured where it occurs, rather than in terms of predefined segments that may not fit the patient's pattern of disease. Furthermore the analysis of motion over regions of the LV rather than at points on the contour reduces variability in the measurement. No realignment is performed to correct for translational artifact, because this tends to worsen variability.
Another parameter of regional dysfunction, in addition to its severity, is the circumferential extent of hypo- or hyperkinesis. This can be measured by counting the number of chords whose motion falls beyond the selected threshold. For example, the one trial of thrombolytic therapy for acute myocardial infarction found that both the severity of hypokinesis and the number of chords showing displacement >2 standard deviations greater or less than the normal mean correlated with prognosis.
Due to its flexibility, the centerline method has been used for analysis of not only left ventricular angiograms in both the 30-degree RAO and 60-degree LAO views, but also right ventricular studies, and for borders traced from ultrasound and magnetic resonance images as well. From tomographic images the centerline method is used to measure regional wall thickening rather than wall motion, since the latter is more subject to artifact due to cardiac translation.
For more information on the Centerline software, please contact Florence Sheehan, MD at the University of Washington.