RingTag: ring-shaped tagging for myocardial centerline assessment.

Abstract

Although endocardial ejection indexes lead to overestimation of contractility in hypertrophied hearts, circumferential fiber shortening at the mid wall (cFS) is less affected by wall thickness. In this study magnetic resonance tagging is exploited to assess directly cFS in normal and hypertrophied hearts. A novel tagging procedure generates freely definable, convex ring saturation bands. Data acquisition during the cardiac cycle is achieved with a fast, single breath-hold echo-planar imaging measurement that is combined with a slice-following approach and a navigator-guided breath-holding technique to improve reproducibility of breath hold positions. The procedure is able to create variably shaped convex saturation structures on the myocardium that can be tracked automatically throughout the cardiac cycle. Circumferential shortening at the endocardial border (FSendo) obtained in 6 healthy volunteers and in 6 patients with hypertensive cardiomyopathy suggested hypercontractility of hypertrophied hearts (30.7 +/- 4.1% vs. 43.9 +/- 4.4% respectively; P < 0.002), whereas shortening at the level of the myofibers assessed as cFS was not different (17.2 +/- 1.4% vs. 18.1 +/- 2.8% respectively; P = 0.49). The presented approach allows for assessment of midwall myocardial mechanics and may become a useful tool to study contractile function in hypertrophied hearts.