Effect of spironolactone on diastolic function in hypertensive left ventricular hypertrophy.

We have previously shown rapid reversal of left ventricular hypertrophy (LVH) with 6 months of spironolactone therapy in patients with resistant hypertension (HTN), preserved left ventricular ejection fraction and no history of heart failure. In this substudy, we investigated the effect of mineralocorticoid receptor blockade with spironolactone on pre-clinical diastolic dysfunction. Thirty-four patients (19 with high and 15 with normal aldosterone levels) were treated with spironolactone and followed with cardiac magnetic resonance with tissue tagging at baseline, 3 and 6 months of treatment. Serum markers of collagen turnover (C-propeptide of type-I procollagen and carboxy-terminal telopeptide of type-I collagen) were measured at baseline and at 6 months. At baseline, patients demonstrated reduced E/A ratio (volumetric normalized peak early filling rate/late filling rate, normalized to left ventricular end-diastolic volume), lower peak early-diastolic mitral annular velocity and lower peak early-diastolic circumferential strain rates compared to the reference values obtained from 45 normal controls without HTN or cardiac disease (all comparisons, P<0.01). No significant change occurred in diastolic filling, relaxation parameters or collagen markers with spironolactone therapy at 6 months irrespective of aldosterone status despite significant reduction in left ventricular mass index in both high- and normal-aldosterone groups. In conclusion, resistant HTN patients with LVH demonstrate significant pre-clinical diastolic dysfunction. Short-term spironolactone therapy may not lead to improvement in diastolic function despite rapid reversal of LVH.

Left ventricular motion reconstruction from planar tagged MR images: a comparison.

Through recent development of MR techniques, it is now possible to assess regional myocardial wall function in a non-invasive way. Using MR tagging, space is marked with planes which deform with the tissue, providing markers for tracking the local motion of the myocardium. Numerous methods to reconstruct the three-dimensional displacement field have been developed. The aim of this article is to provide a framework to quantitatively compare the performance of four methods the authors have developed. Five sets of experiments are described, and their results are reported. Instructions are also provided to perform similar tests on any method using the same data. The experiments show that some characteristic properties of the methods, such as sensitivity to noise or spatial resolution, can be quantitatively classified. Cross-comparison of performances show what range values for these properties can be considered acceptable.

Estimation and detection of myocardial tags in MR image without user-defined myocardial contours.

Magnetic resonance (MR) tagging has been shown to be a useful technique for noninvasively measuring the deformation of an in vivo heart. An important step in analyzing tagged images is the identification of tag lines in each image of a cine sequence. Most existing tag identification algorithms require user defined myocardial contours. Contour identification, however, is time consuming and requires a considerable amount of user intervention. In this paper, a new method for identifying tag lines, which we call the ML/MAP method, is presented that does not require user defined myocardial contours. The ML/MAP method is composed of three stages. First, a set of candidate tag line centers is estimated across the entire region-of-interest (ROI) with a snake algorithm based on a maximum-likelihood (ML) estimate of the tag center. Next, a maximum a posteriori (MAP) hypothesis test is used to detect the candidate tag centers that are actually part of a tag line. Finally, a pruning algorithm is used to remove any detected tag line centers that do not meet a spatio-temporal continuity criterion. The ML/MAP method is demonstrated on data from ten in vivo human hearts.

Model-free reconstruction of three-dimensional myocardial strain from planar tagged MR images.

A technique is presented for reconstructing a three-dimensional myocardial strain map from a set of parallel-tagged MR images. Radial strains were reconstructed from in vivo data from an anesthetized dog with values between .05 and .1 with a precision of +/- .003 for a tag detection accuracy of .1 mm and a tag spacing of 2.5 mm. The reconstruction spatial resolution was demonstrated by reconstructing a localized displacement abnormality. In the circumferential direction, the abnormality that resulted in 50% displacement attenuation had a full width at half maximum of 5.4 +/- .4 mm (mean +/- SD). Graphs are presented showing the relationship between the size of an abnormality and the ability of the method to reconstruct that abnormality. The combination of high resolution parallel-tagged MR images and the model-free, coordinate system-free strain reconstruction technique presented in this paper is capable of producing accurate, high resolution strain maps of the myocardium.