Three-dimensional myocardial strain analysis based on short- and long- axis magnetic resonance tagged images using a 1D displacement field

A robust algorithm to estimate three-dimensional strain in the left- ventricular heart wall, based on magnetic resonance (MR) grid-tagging in two sets of orthogonal image planes, is presented. Starting-point of this study was to minimize global interpolation and smoothing. Only the longitudinal displacement was interpolated between long-axis images. Homogenous strain analysis was performed using small tetrahedrons. The method was tested using a stack of short-axis images and three long-axis images in six healthy volunteers. In addition, the method was subjected to an analytical test case, in which the effect of noise in tag point position on the observed strains was explored for normally distributed noise (0.5 mm RMS). In volunteers, the error in the longitudinal displacement due to interpolation between the long- axis image planes was -0.10 ± 0.48 mm (mean ± SD). The resulting error in the longitudinal strain ε1 was -.003 ± 0.02. The analytical test case was used to quantify the effects of three sources of errors on the observed strain. The SD of the difference between homogeneous strain and true strain was 0.06 for ε1. The error due to the 3-D reconstruction was 0.004 for ε1. The error in ε1 resulting from simulated noise in the tag point position was 0.10. Equivalent results were obtained for all other strain parameters; thus, the error resulting from noise in the tag point position dominates the error introduced by approximations in the method. Because the proposed method uses a minimum of global interpolation and smoothing, it offers the prospect to detect small regions of aberrant contraction. (C) 2000 Elsevier Science Inc

Three-dimensional myocardial strains at end-systole and during diastole in the left ventricle of normal humans

This paper presents the three-dimensional strains in the normal human left ventricle (LV) at end-systole and during diastole. Magnetic resonance tissue tagging was used to measure strain in the left-ventricular heart wall in 10 healthy volunteers aged between 28 and 61 years. The three-dimensional motion was calculated from the displacement of marker points in short- and long-axis cine images, with a time resolution of 30 msec. Homogeneous strain analysis of small tetrahedrons was used to calculate deformation in 18 regions of the LV over a time span of 300msec starting at end systole. End-systolic radial strain was largest near the heart base, and circumferential and longitudinal strains were largest near the apex. During diastole, the circumferential-longitudinal shear strain (associated with LV torsion) was found to recover earlier than the axial strains. Assessment of three-dimensional diastolic strain is possible with MR tagging. Comparison of patient strain against normal strain may permit early detection of regional diastolic dysfunction

Loss of capture of conduction system pacemaker caused by fibrosis surrounding the lead: a case report

Abstract Background Conduction system pacing (CSP) is a novel technique that involves pacing the His-Purkinje system instead of the traditional right ventricular (RV) apex. This technique aims to avoid the adverse effects of RV apical pacing, which can lead to ventricular dyssynchrony and heart failure over time. CSP is gaining popularity but its long-term efficacy and challenges remain uncertain. This report discusses a case where CSP was initially successful but faced complications due to an increasing pacing threshold. Case presentation A 65-year-old female with total atrioventricular block was referred for brady-pacing. Due to the potential for chronic RV pacing, CSP was chosen. The CSP implantation involved subcutaneous device placement, with a CSP lead in the left bundle branch area (LBBA) and an RV backup lead. A year after successful implantation, the LBBA pacing threshold progressively increased. Subsequent efforts to correct it led to anodal capture and battery depletion. Cardiac magnetic resonance imaging (CMR) revealed mid-septal fibrosis at the area of LBBA lead placement and suggested cardiac sarcoidosis as a possible cause. Conclusion CSP is a promising technique for treating bradyarrhythmias, but this case underscores the need for vigilance in monitoring pacing thresholds. Increasing thresholds can render CSP ineffective, necessitating alternative pacing methods. The CMR findings of mid-septal fibrosis and the potential diagnosis of cardiac sarcoidosis emphasize the importance of pre-implantation assessment, as CSP may be compromised by underlying structural abnormalities. This report highlights the complexities of pacing strategy selection and the significance of comprehensive evaluation before adopting CSP

Magnetic resonance and nuclear imaging of the right ventricle in pulmonary arterial hypertension

Many clinicians have recognized the unique possibilities of magnetic resonance imaging (MRI) for the study of right ventricular (RV) anatomy. Especially for the assessment of the RV in pulmonary hypertension, MRI has been proven to be of clinical importance. It is, however, less well known that if MRI measures of volume and flow are combined with pressure measurements, accurate description of RV function in relation to its afterload is possible. Furthermore, nuclear imaging techniques offer the opportunity to study the altered RV metabolism and to elucidate the possible contribution of ischaemia to RV failure in pulmonary hypertension. Since RV failure in pulmonary hypertension is the result of the complex interaction between geometry, structure, function, perfusion, and metabolism, MRI and nuclear imaging are promising techniques to study these mechanisms and to evaluate the effects of therapy aimed at improving RV function in pulmonary hypertension

Variance components of two-dimensional strain parameters in the left-ventricular heart wall obtained by magnetic resonance tagging

This study quantifies variance components of two-dimensional strains in the left-ventricular heart wall assessed by magnetic resonance (MR) tagging in 18 healthy xxvolunteers. For a 7-mm tagging grid and homogeneous strain analysis, the intersubject variability and measurement error were estimated, as well as the intra- and interobserver variability. The variance components were calculated for the mean strain of a circumferential sector. The results show that the measurement error was almost equal to the intra-observer variability. With four circumferential sectors of 90° each, approximately 65% of the total variance in ε r and ε c was due to intersubject variability, the remaining 35% was due to measurement error. With 12 sectors of 30° each, the intersubject variability and measurement error both contributed 50% to the total variance. With 18 sectors of 20° each, only 40% of the total variance was due to intersubject variability. The total variability increased with the number of sectors and therefore the number of sectors used in a study will be a trade-off between segment size (defining spatial resolution) and variability

Differences between gap-related persistent conduction and carina-related persistent conduction during radiofrequency pulmonary vein isolation

Background: During pulmonary vein isolation (PVI), nonisolation after initial encircling of the pulmonary veins (PVs) may be due to gaps in the initial ablation line, or alternatively, earliest PV activation may occur on the intervenous carina and ablation within the wide-area circumferential ablation (WACA) circle is needed to eliminate residual conduction. This study investigated prognostic implications and predictors of gap-related persistent conduction (gap-RPC) and carina-related persistent conduction (carina-RPC) during PVI. Methods and Results: Two hundred fourteen atrial fibrillation (AF) patients (57% paroxysmal, 61% male, mean age 62 ± 9 years) undergoing first contact force-guided radiofrequency PVI were studied. Preprocedural cardiac computed tomography imaging was used to assess left atrial and PV anatomy. PVI was assessed directly after initial WACA circle creation, after a minimum waiting period of 30 minutes, and after adenosine infusion. Persistent conduction was targeted for additional ablation and classified as gap-RPC or carina-RPC, depending on the earliest activation site. The 1-year AF recurrence rate was higher in patients with gap-RPC (47%) compared to patients without gap-RPC (28%; P =.003). No significant difference in 1-year recurrence rate was found between patients with carina-RPC (37%) and patients without carina-RPC (31%; P =.379). Multivariate analyses identified paroxysmal AF and WACA circumference as independent predictors of gap-RPC, whereas carina width and WACA circumference correlated with carina-RPC. Conclusions: Gap-RPC is associated with increased AF recurrence risk after PVI, whereas carina-RPC does not predict AF recurrence. Moreover, gap-RPC and carina-RPC have different correlates and may thus have different underlying mechanisms

Perfusable tissue index as a potential marker of fibrosis in patients with idiopathic dilated cardiomyopathy

A varying degree of interstitial and perivascular fibrosis is a common finding in idiopathic dilated cardiomyopathy (DCM). The perfusable tissue index (PTI), obtained with PET, is a non-invasive tool for assessing myocardial fibrosis on a regional level. Measurements of the PTI in DCM, however, have not been performed yet. This study was undertaken to test the hypothesis that the PTI is reduced in patients with DCM. Methods: Fifteen patients with an advanced stage of DCM (New York Heart Association class III or IV and left ventricular ejection fraction [LVEF] < 35%) and 11 healthy control subjects were studied. PET was performed using H2 15O and C15O to obtain the perfusable tissue fraction (PTF) and the anatomic tissue fraction (ATF), respectively. Results: The PTI (=PTF/ATF) was reduced in DCM compared with control subjects (0.91 ± 0.12 vs. 1.12 ± 0.10; P < 0.01). Heterogeneity of the PTI, expressed as the coefficient of variation, was increased in DCM versus that of healthy control subjects (0.18 ± 0.07 vs. 0.13 ± 0.06; P < 0.05). There was no correlation between the PTI and echocardiographically derived LVEF in both groups. Conclusion: The PTI was reduced in patients with an advanced stage of DCM. Interstitial and perivascular fibrosis may be responsible for this reduction. Furthermore, the degree of the PTI reduction was variable in DCM patients, both on a regional level and between patients. Noninvasive assessment of fibrosis with the PTI offers the opportunity to evaluate the effects of fibrosis on regional myocardial function, correlate fibrosis with prognosis, and monitor pharmaceutical intervention