Mitral valve regurgitation

Ultrastructural Adaptation of the Cardiomyocyte to Chronic Mitral Regurgitation

Introduction: Mitral regurgitation (MR) imposes volume overload on the left ventricle (LV) and elevates wall stress, triggering its adverse remodeling. Pronounced LV dilation, minimal wall thinning, and a gradual decline in cardiac ejection fraction (EF) are observed. The structural changes in the myocardium that define these gross, organ level remodeling are not known. Cardiomyocyte elongation and slippage have both been hypothesized, but neither are confirmed, nor are the changes to the cardiomyocyte structure known. Using a rodent model of MR, we used immunohistochemistry and transmission electron microscopy (TEM) to describe the ultrastructural remodeling of the cardiomyocyte.

Methods: Twenty-four male Sprague-Dawley rats (350–400 g) were assigned to two groups: group (1) rats induced with severe MR (n = 18) and group (2) control rats that were healthy and age and weight matched (n = 6). MR was induced in the beating heart using a 23-G ultrasound-guided, transapical needle to perforate the anterior mitral leaflet, and the rats were followed to 2, 10, and 20 weeks (n = 6/time-point). Echocardiography was performed to quantify MR severity and to measure LV volume and function at each time-point. Explanted myocardial tissue were examined with TEM and immunohistochemistry to investigate the ultrastructural changes.

Results: MR induced rapid and significant increase in end-diastolic volume (EDV), with a 50% increase by 2 weeks, compared with control. Rise in end-systolic volume (ESV) was more gradual; however, by 20 weeks, both EDV and ESV in MR rats were increased by 126% compared with control. A significant decline in EF was measured at 10 weeks of MR. At the ultrastructural level, as early as 2 weeks after MR, cardiomyocyte elongation and increase in cross-sectional area were observed. TEM depicted sarcomere shortening, with loss of Z-line and I-band. Desmin, a cytoskeletal protein that is uniformly distributed along the length of the cardiomyocyte, was disorganized and localized to the intercalated disc, in the rats induced with MR and not in the controls. In the rats with MR, the linear registry of the mitochondrial arrangement along the sarcomeres was lost, with mitochondrial fragmentation, aggregation around the nucleus, and irregularities in the cristae.

Discussion: In the setting of chronic mitral regurgitation, LV dilatation occured by cardiomyocyte elongation, which manifests at the subcellular level as distinct ultrastructural alterations of the sarcomere, cytoskeleton, and mitochondria. Since the cytoskeleton not only provides tensegrity but has functional consequences on myocyte function, further investigation into the impact of cytoskeletal remodeling on progressive heart failure or recovery of function upon correcting the valve lesion are needed.

Congestive heart failure model representing aortic banding induced hypertrophy: A study to analyse extent of pressure overload and alteration in myocardial structure and function

Congestive Heart failure (CHF) is a severe pathology representing a major public health problem in industrialized nations which is increasing in prevalence and incidence. The aortic banding rat model provides steady progression of cardiac dysfunction under chronic pressure overload. Present study evaluated two abdominal aortic constriction techniques including constriction of aorta above renal arteries and between renal arteries. The extent of constriction was varied with 22 G and 24 G needles and the duration for evaluation of CHF was also varied by terminating the banded animals after 6 and 8 weeks of banding. Various hemodynamic, ECG and tissue parameters were evaluated after banding to see the progression of CHF. The findings revealed that the constriction of the aorta above both renal arteries with 24 G needle is a better technique amongst other tested banding techniques as the rate of progression of CHF was found to be maximum with it. On the basis of above study, it was concluded that, aortic banding above both renal arteries with 24 G needle is a better technique for induction of pressure overload and for further observation in transition of the cardiac compensatory to decompensatory phase, the duration of the model needs to be prolonged.

Mitral annular calcification: Can CMR be useful in identifying caseous necrosis?

Mitral annular calcification (MAC) can resemble an intracardiac mass and it is defined as a chronic degeneration of the mitral annulus. Often reported is caseous mitral annulus calcification (CMAC), a periannular, extensive calcification resembling a tumor. We report the case of a 68-year-old woman who had been hospitalized for palpitations and dyspnea. The transthoracic and transesophageal echocardiography revealed a non-homogeneous, slightly mobile, round mass, attached to the ventricular side of posterior mitral leaflet, with central echo-lucent area and without acoustic shadowing. Therefore, a cardiac magnetic resonance (CMR) was performed; delayed enhancement sequences showed a non-enhanced central core surrounded by a hyperenhanced rim (fibrous cap). To confirm the diagnosis, a multidetector computed tomography (MDCT) was performed; the MDCT showed a hyperdense mass with a hypodense center and a calcified peripheral rim. The central content had heterogeneous fluid density without significant contrast enhancement. The MDCT findings were considered highly suggestive of CMAC. CMR may be useful for the identification and definition of pericardial and myocardial masses and CMAC.

Phenotyping progression of secondary mitral regurgitation in chronic systolic heart failure

BACKGROUND

Secondary mitral regurgitation (sMR) drives adverse cardiac remodelling in patients with heart failure with reduced ejection fraction (HFrEF). Progression in severity over time contributes to a transition towards more advanced HF stages. Early identification of patients at risk for sMR progression remains challenging. We therefore sought to assess a broad spectrum of neurohumoral biomarkers in patients with HFrEF to explore their ability to predict progression of sMR.

METHODS

A total of 249 HFrEF patients were enrolled. Biomarkers encompassing key neurohumoral pathways in heart failure were sampled at baseline, and sMR progression was assessed over 3 years of follow-up.

RESULTS

Of 191 patients with nonsevere sMR at baseline, 18% showed progressive sMR within three years after study enrolment. Progression of sMR was associated with higher levels of MR-proADM (adj.OR 2.25, 95% CI 1.29-3.93; P = .004), MR-proANP (adj.OR 1.84, 95% CI 1.14-3.00; P = .012), copeptin (adj.OR 1.66, 95% CI 1.04-2.67; P = .035) and CT-pro-ET1 (adj.OR 1.68, 95% CI 1.06-2.68; P = .027) but not with NT-proBNP (P = .54).

CONCLUSION

Increased plasma levels of neurohumoral cardiac biomarkers are predictors of sMR progression in patients with HFrEF and add easily available incremental prognostic information for risk stratification. Importantly, NT-proBNP was not useful to predict progressive sMR in the present analysis. On the contrary, MR-proANP, primarily produced in the atria, copeptin partly triggered by intra-cardiac and intra-arterial pressures and MR-proADM, a marker of forward failure and peripheral released vasoactive CT-proET1, increase based on a progressive loading burden by sMR and may thus serve as better predictors of sMR progression.

Caseous mitral annular calcifications: Multimodality imaging characteristics

The authors report herein a series of 3 patients with caseous mitral annular calcifications (MAC). One of the patients presented with mass-like, caseous MAC as an incidental finding on a staging computed tomography (CT) for metastatic colorectal carcinoma. Another patient presented with a nodule on a chest radiograph, which was later found on CT to be due to caseous MAC. In the third patient, caseous MAC was initially detected on echocardiography, and was further evaluated with CT and cardiac magnetic resonance imaging. In all three patients, the appearances posed a diagnostic dilemma. The appearance of caseous MAC is dissimilar to non-caseous MAC and is usually seen as an ovoid, mass-like structure, with homogeneous hyperattenuation, representing a liquefied form of calcium and proteinaceous fluid. This homogeneous center is surrounded by peripheral, shell-like calcifications. Caseous MAC is likely an under-recognized entity and may present a diagnostic dilemma at CT, magnetic resonance imaging, or echocardiography.

CT angiography of the cardiac valves: normal, diseased, and postoperative appearances

Although echocardiography remains the principal imaging technique for assessment of the cardiac valves, contrast material-enhanced electrocardiographically gated computed tomographic (CT) angiography is proving to be an increasingly valuable complementary modality in this setting. CT angiography allows excellent visualization of the morphologic features and function of the normal valves, as well as of a wide range of valve diseases, including congenital and acquired diseases, infectious endocarditis, and complications of valve replacement. The number, thickness, and opening and closing of the valve leaflets, as well as the presence of valve calcification, can be directly observed. CT angiography also permits simultaneous assessment of the valves and coronary arteries, which may prove valuable in presurgical planning. Unlike echocardiography and magnetic resonance imaging, however, CT angiography requires ionizing radiation and does not provide a direct measure of the valvular pressure gradient. Nevertheless, with further development of related imaging techniques, CT angiography can be expected to play an increasingly important role in the evaluation of the cardiac valves. Supplemental material available at http://radiographics.rsna.org/cgi/content/full/29/5/1393/DC1.

Doença crônica da valva mitral em cães: avaliação clínica funcional e mensuração ecocardiográfica da valva mitral

Foram descritos os achados do exame físico em cães com degeneração mixomatosa crônica da valva mitral e mensurado o comprimento e a espessura das cúspides da valva mitral pelo exame ecocardiográfico. Utilizaram-se 81 cães de diferentes raças de pequeno a médio porte, com idade de 11,12± 2,51 anos e peso de 6,24kg± 3,19, dos quais 20 eram clinicamente normais (grupo-controle) e 61 apresentavam evidências clínicas de cardiopatia. Os animais foram distribuídos em três classes distintas segundo a insuficiência cardíaca congestiva (grupos I, II e III), de acordo com os dados do histórico e dos sinais clínicos apresentados. Ao exame ecocardiográfico, avaliaram-se as medidas das cúspides da valva mitral, que não apresentaram diferença entre os cães do grupo I e II, embora estivessem anormais se comparadas às dos cães do grupo-controle. Nos animais do grupo III, as medidas das valvas avaliadas foram maiores que as dos cães dos grupos I e II. Foram observados nódulos com formato arredondado e, nos cães do grupo III, as cúspides estavam bastante alongadas e espessadas.

Computed tomography assessment of valvular morphology, function, and disease

Recent advancement in computed tomography angiography (CTA) has enabled the noninvasive delineation of cardiac valves using this method. Although echocardiography is the current standard, CTA is a valuable complementary imaging method to evaluate valvular morphology and function. In addition, CTA may contribute to the assessment of both congenital and acquired valvular heart disease, infectious endocarditis, and postsurgical complications of valve replacement.

Pimobendan in heart failure therapy--a silver bullet?

Pimobendan is a novel agent with properties that are highly desirable in the clinical management of congestive heart failure (CHF) secondary to both dilated cardiomyopathy (DCM) and chronic degenerative valvular disease in dogs. Review of available data suggests that pimobendan is safe, well tolerated, and leads to enhanced quality of life in dogs with CHF secondary to DCM or chronic valvular disease when used in combination with furosemide or other conventional therapies (e.g., angiotensin-converting enzyme inhibitors, digoxin). Pimobendan leads to a reduction in mortality from CHF associated with DCM, and ongoing studies are evaluating its effects on mortality associated with chronic valvular disease.

Mitral annulus calcification is associated with valvular and cardiac structural abnormalities

Introduction

Mitral annulus calcification (MAC) is a common finding on echocardiographic examination. The goal of this study was to evaluate associations between MAC and cardiac abnormalities using a large echocardiographic database.

Methods

For this study we retrospectively reviewed 24,380 echocardiograms performed for clinical reasons between the years 1984 and 1998.

Results

MAC was reported in 1,494 (6.1%) subjects. Using multivariate analysis, age, left ventricular hypertrophy (LVH), mitral regurgitation (MR), tricuspid regurgitation (TR), aortic stenosis (AS), left atrial (LA) enlargement and reversed E/A ratio were independently associated with MAC.)MAC was noted in 11.7 % of patients with MR vs. 4.3% without MR (OR: 2.0, CI 1.6–2.6, p < 0.0001), in 13.9% of those with TR vs. 4.5% without TR (OR: 3.8, CI 2.9–4.8, p < 0.0001), in 10.6% with LVH vs. 4.2% without LVH (OR: 1.9, CI 1.5–2.4, p < 0.0001), in 14.8% with AS vs. 5.5% without AS (OR: 1.4, CI 1.08–1.9, p = 0.01), in 9.4% with reversed E/A ratio vs. 3.8% without reversed E/A ratio (OR: 1.7, CI 1.4–2.2, p < 0.0001) and in 8.2% with LA enlargement vs. 4.8% without LA enlargement (OR: 1.3, CI 1.06–1.7, p = 0.02).

Conclusion

In our study, MAC independently correlated with significant structural heart abnormalities. This suggests that identification of MAC may serve as a marker for other cardiac structural disorders.