The role of magnetic resonance imaging in hypertrophic cardiomyopathy

Hypertrophic obstructive cardiomyopathy-left ventricular outflow tract shapes and their hemodynamic influences applying CMR

Hypertrophic cardiomyopathy (HCM) is one of the most common genetic cardiac disorders and is characterized by different phenotypes of left ventricular hypertrophy with and without obstruction. The effects of left ventricular outflow tract (LVOT) obstruction based on different anatomies may be hemodynamically relevant and influence therapeutic decision making. Cardiovascular magnetic resonance (CMR) provides anatomical information. We aimed to identify different shapes of LVOT-obstruction using Cardiovascular Magnetic Resonance (CMR). The study consisted of two parts: An in-vivo experiment for shape analysis and in-vitro part for the assessment of its hemodynamic consequences. In-vivo a 3D depiction of the LVOT was created using a 3D multi-slice reconstruction from 2D-slices (full coverage cine stack with 7 slices and a thickness of 5-6 mm with no gap) in 125 consecutive HOCM patients (age = 64.17 +/- 12.655; female n = 42). In-vitro an analysis of the LVOT regarding shape and flow behavior was conducted. For this purpose, 2D and 4D measurements were performed on 3D printed phantoms which were based on the anatomical characteristics of the in-vivo study, retrospectively. The in-vivo study identified three main shapes named K- (28.8%), X- (51.2%) and V-shape (10.4%) and a mixed one (9.6%). By analyzing the in-vitro flow measurements every shape showed an individual flow profile in relation to the maximum velocity in cm/s. Here, the V-shape showed the highest value of velocity (max. 138.87 cm/s). The X-shape was characterized by a similar profile but with lower velocity values (max. 125.39 cm/s), whereas the K-shape had an increase of the velocity without decrease (max. 137.11 cm/s). For the first time three different shapes of LVOT-obstruction could be identified. These variants seem to affect the hemodynamics in HOCM.

A Rare Case of Mass-Like Hypertrophic Cardiomyopathy

Mass-like hypertrophic cardiomyopathy (HCM) is a unique variant of HCM. HCM predominantly causes mid-ventricular, concentric hypertrophy, and asymmetric septal hypertrophy; however, focal hypertrophy mimicking a cardiac fibroma is rare. A 29-year-old female with a past medical history of recurrent orthostatic hypotension and syncope presented to the emergency department (ED) complaining of lightheadedness, dizziness, and generalized weakness associated with a syncopal episode. The patient reported a history of recurrent pre-syncope and syncope since her teenage years, as well as a family history of sudden cardiac death. Three years prior to her current presentation, the patient had an exercise stress test, 24-hour Holter monitor, and two echocardiograms that were unremarkable. Three weeks prior to presentation, the patient had a cardiac MRI that revealed focal mass hypertrophy of the basal anterior to mid anterior wall measuring up to 2.5 cm. In the ED, the patient was treated with intravenous fluid and beta-blockers; however, beta-blocker therapy had to be discontinued because the patient was experiencing presyncopal episodes and orthostatic hypotension. The patient was started on midodrine with partial improvement lightheadedness, dizziness, and presyncope. The patient was transferred to a tertiary center with the plan to do serial imaging and place an implantable cardioverter-defibrillator (ICD) if the focal mass thickness reached 3 cm and explore surgical intervention if symptoms worsened. Identifying and reporting anomalous variants of HCM is critical for optimal management of patient care and to improve outcomes.

Ventricular diastolic dimension over maximal myocardial thickness is robust landmark of systolic impairment in patients with hypertrophic cardiomyopathy

Background

The effects of focal hypertrophy on geometry of the left ventricle and systolic function have not been studied in patients with hypertrophic cardiomyopathy (HCM), despite the fact that the former is the most prominent disease characteristic. The aim of our study was to analyze systolic function over ventricle geometry, generating a functional index made from left ventricle end diastolic dimension (LVEDD) divided by end diastolic thickness of the region with maximal extent of hypertrophy and interventricular septum.

Material/Methods

Our hospital database of cardiac magnetic resonance was screened for HCM. Geometric functional index (GFI) was calculated for LVEDD over maximal end diastolic thickness (MaxEDT) giving GFI-M, while LVEDD over interventricular septum was expressed as GFI-I. There were 55 consecutive patients with HCM.

Results

There were 43 males (78.2%) and 12 females (21.8%). The mean age was 52.3±16.7 years (range: 15.5–76.4 years). A significant difference of GFI was found for preserved versus impaired systolic function of the left ventricle (preserved systolic function); GFI-M 2.28±0.60 versus 3.66±0.50 (p<0.001), and GFI-I 2.75±0.88 versus 3.81±0.87 (p<0.001), respectively. Diagnostic value was tested using receiver operating curve (ROC) analyzes, with GFI-M area under curve (AUC)=0.959 (95% CI: 0.868–0.994); (p<0.001) and GFI-I-AUC=0.847 (0.724–0.930); (p<0.001). GFI-M was superior to GFI-I for appraisal of left ventricle systolic dysfunction in HCM; ΔAUC=0.112 (0.018–0.207); (p=0.020).

Conclusions

GFI is a simple tool, with high sensitivity and specificity for detecting impairment of systolic function in patients with HCM. Further studies would be necessary to investigate its clinical and prognostic impacts, as well as reproducibility with prospective validation.

Left Ventricular Wall Stress Is Sensitive Marker of Hypertrophic Cardiomyopathy With Preserved Ejection Fraction

Hypertrophic cardiomyopathy (HCM) patients present altered myocardial mechanics due to the hypertrophied ventricular wall and are typically diagnosed by the increase in myocardium wall thickness. This study aimed to quantify regional left ventricular (LV) shape, wall stress and deformation from cardiac magnetic resonance (MR) images in HCM patients and controls, in order to establish superior measures to differentiate HCM from controls. A total of 19 HCM patients and 19 controls underwent cardiac MR scans. The acquired MR images were used to reconstruct 3D LV geometrical models and compute the regional parameters (i.e., wall thickness, curvedness, wall stress, area strain and ejection fraction) based on the standard 16 segment model using our in-house software. HCM patients were further classified into four quartiles based on wall thickness at end diastole (ED) to assess the impact of wall thickness on these regional parameters. There was a significant difference between the HCM patients and controls for all regional parameters (P < 0.001). Wall thickness was greater in HCM patients at the end-diastolic and end-systolic phases, and thickness was most pronounced in segments at the septal regions. A multivariate stepwise selection algorithm identified wall stress index at ED (σ_i,ED) as the single best independent predictor of HCM (AUC = 0.947). At the cutoff value σ_i,ED < 1.64, both sensitivity and specificity were 94.7%. This suggests that the end-diastolic wall stress index incorporating regional wall curvature—an index based on mechanical principle—is a sensitive biomarker for HCM diagnosis with potential utility in diagnostic and therapeutic assessment.

The mechanisms, diagnosis and management of mitral regurgitation in mitral valve prolapse and hypertrophic cardiomyopathy

Valvular disease is a frequent cardiac pathology leading to heart failure and, ultimately, death. Mitral regurgitation, defined as the inability of the two mitral leaflets to coapt, is a common valvular disease and a self sustained pathology. A better understanding of the mitral valve histological layers provides a better understanding of the leaflet and chordae changes in mitral valve prolapse. Mitral valve prolapse may occur in myxomatous degenerative abnormalities, connective tissue disorders or in sporadic isolated cases. It is the most common mitral abnormality of non-ischemic cause leading to severe surgery-requiring mitral regurgitation. In addition to standard echocardiographic investigations, newly implemented three-dimensional techniques are being used and they permit a better visualisation, from the so-called ‘surgical view’, and an improved evaluation of the mitral valve. Hypertrophic cardiomyopathy is the most frequent inherited myocardial disease caused by mutations in various genes encoding proteins of the cardiac sarcomere, leading to a marked left ventricular hypertrophy unexplained by other comorbidities. The pathological echocardiographic hallmarks of hypertrophic cardiomyopathy are left ventricular hypertrophy, left ventricular outflow tract obstruction and systolic anterior motion of the mitral valve. The systolic anterior motion of the mitral valve contributes to the development of mitral regurgitation and further narrows the left ventricular outflow tract, leading to more severe symptomatology. Cardiac magnetic resonance imaging accurately measures the left ventricular mass, the degree of diastolic function and it may also be used to distinguish phenotypic variants. The clinical outcome of patients with these pathologies is mostly determined by the selected option of treatment. The purpose of surgical correction regarding mitral valve involvement is to restore valvular competence. Surgery has proven to be the only useful treatment in preventing heart failure, improving symptomatology and reducing mortality. Our approach wishes to enhance the understanding of the mitral valve’s involvement in hypertrophic cardiomyopathy and mitral valve prolapse from genetic, haemodynamic and clinical perspectives, as well as to present novelties in the grand field of treatment.

Cardiac Magnetic Resonance and Computed Tomography in Hypertrophic Cardiomyopathy: an Update

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiovascular disease and represents the main cause of sudden death in young patients. Cardiac magnetic resonance (CMR) and cardiac computed tomography (CCT) are noninvasive imaging methods with high sensitivity and specificity, useful for the establishment of diagnosis and prognosis of HCM, and for the screening of patients with subclinical phenotypes. The improvement of image analysis by CMR and CCT offers the potential to promote interventions aiming at stopping the natural course of the disease. This study aims to describe the role of RCM and CCT in the diagnosis and prognosis of HCM, and how these methods can be used in the management of these patients.

Myocardial triglyceride content in patients with left ventricular hypertrophy: comparison between hypertensive heart disease and hypertrophic cardiomyopathy

Proton magnetic resonance spectroscopy (¹H-MRS) enables the assessment of myocardial triglyceride (TG) content, which is reported to be associated with cardiac dysfunction and morphology accompanied by metabolic disorder and cardiac hemodynamic status. The clinical usefulness of myocardial TG content measurements in patients with left ventricular hypertrophy (LVH) has not been fully investigated. We examined whether myocardial TG content assessed by ¹H-MRS was useful for diagnosis in patients with LVH. To quantify myocardial TG content, we conducted ¹H-MRS in 35 subjects with LVH. Left ventricular function was measured by cardiac magnetic resonance imaging. Patients were assigned to a hypertensive heart disease (HHD, n = 10) or hypertrophic cardiomyopathy (HCM, n = 25) group based on the histology and/or late gadolinium enhancement pattern. The myocardial TG content was significantly higher in the HHD group than in the HCM group (2.14 ± 1.29 vs. 1.09 ± 0.72 %, P < 0.001). Myocardial TG content were significantly and negatively correlated with LV mass (r = -0.41, P < 0.04) and stroke volume (r = -0.64, P < 0.05) in the HCM group and HHD group, respectively. In a multivariate analysis, LV mass volume and diagnosis of HCM or HHD were independent factors of the myocardial TG content. The results suggest that myocardial metabolism may differ between HCM and HHD patients and that measurement of myocardial TG content by ¹H-MRS may be useful for evaluating the myocardial metabolic features of LVH.

Real-time free-breathing cardiac imaging with self-calibrated through-time radial GRAPPA

PURPOSE

Real-time free-breathing cardiac imaging with highly undersampled radial trajectories has previously been successfully demonstrated using calibrated radial generalized autocalibrating partially parallel acquisition (rGRAPPA). A self-calibrated approach for rGRAPPA is proposed that removes the need for the calibration prescan.

METHODS

To investigate the effect of various parameters on image quality, a comprehensive imaging study on one normal swine was performed. Root mean squared errors (RMSEs) were computed with respect to gold standard acquisitions, and several acquisition/reconstruction strategies were compared. Additionally, the method was tested on 13 human subjects, and RMSEs relative to standard through-time radial GRAPPA were computed.

RESULTS

Real-time images with high spatiotemporal resolution were obtained. Image quality was comparable to calibrated through-time rGRAPPA with endocardial and epicardial borders clearly delineated. In the swine, the average RMSE between self-calibrated and gold-standard calibrated images was 5.18 ± 0.84%. In normal human subjects, the average RMSE between self-calibrated and calibrated through-time rGRAPPA was 3.79 ± 0.64%. For lower accelerations rates (R = 6-8) image quality was similar to comparable calibrated scans though RMSE increased for higher degrees of undersampling (R = 12-16).

CONCLUSION

Highly accelerated real-time imaging with undersampled radial trajectories without additional calibration data is feasible. Image quality was acceptable for real-time cardiac MRI applications demanding high speed. Magn Reson Med 77:250-264, 2017. © 2016 Wiley Periodicals, Inc.