A human MYBPC3 mutation appearing about 10 centuries ago results in a hypertrophic cardiomyopathy with delayed onset, moderate evolution but with a risk of sudden death.

BACKGROUND: Hypertrophic Cardiomyopathy (HCM) is a genetically heterogeneous disease. One specific mutation in the MYBPC3 gene is highly prevalent in center east of France giving an opportunity to define the clinical profile of this specific mutation. METHODS: HCM probands were screened for mutation in the MYH7, MYBPC3, TNNT2 and TNNI3 genes. Carriers of the MYBPC3 IVS20-2A>G mutation were genotyped with 8 microsatellites flanking this gene. The age of this MYBPC3 mutation was inferred with the software ESTIAGE. The age at first symptom, diagnosis, first complication, first severe complication and the rate of sudden death were compared between carriers of the IVS20-2 mutation (group A) and carriers of all other mutations (group B) using time to event curves and log rank test. RESULTS: Out of 107 HCM probands, 45 had a single heterozygous mutation in one of the 4 tested sarcomeric genes including 9 patients with the MYBPC3 IVS20-2A>G mutation. The IVS20-2 mutation in these 9 patients and their 25 mutation carrier relatives was embedded in a common haplotype defined after genotyping 4 polymorphic markers on each side of the MYBPC3 gene. This result supports the hypothesis of a common ancestor. Furthermore, we evaluated that the mutation occurred about 47 generations ago, approximately at the 10th century.We then compared the clinical profile of the IVS20-2 mutation carriers (group A) and the carriers of all other mutations (group B). Age at onset of symptoms was similar in the 34 group A cases and the 73 group B cases but group A cases were diagnosed on average 15 years later (log rank test p = 0.022). Age of first complication and first severe complication was delayed in group A vs group B cases but the prevalence of sudden death and age at death was similar in both groups. CONCLUSION: A founder mutation arising at about the 10th century in the MYBPC3 gene accounts for 8.4% of all HCM in center east France and results in a cardiomyopathy starting late and evolving slowly but with an apparent risk of sudden death similar to other sarcomeric mutations.

Immediate improvement in coronary flow reserve after alcohol septal ablation in patients with hypertrophic obstructive cardiomyopathy.

OBJECTIVES: To examine whether percutaneous alcohol septal ablation affects coronary flow reserve (CFR) in patients with hypertrophic cardiomyopathy (HCM). METHODS: CFR was measured immediately before and after septal ablation in patients with symptomatic obstructive HCM. CFR was also obtained in normal subjects (NL) for comparison. RESULTS: Patients with HCM (n = 11), compared with NL (n = 22), had a lower mean (SD) baseline CFR (1.96 (0.5) vs 3.0 (0.7), p<0.001), a lower coronary resistance (1.04 (0.45) vs 3.0 (2.6), p = 0.002), a higher coronary diastolic/systolic velocity ratio (DSVR; 5.1 (3.0) vs 1.8 (0.5), p = 0.04) and a lower hyperaemic coronary flow per left ventricular (LV) mass (0.73 (0.4) vs 1.1 (0.6) ml/min/g, p = 0.007). Septal ablation in the HCM group (n = 7) reduced the outflow tract gradient but not the left atrial or LV diastolic pressures. Ablation resulted in immediate normalisation of CFR (to 3.1 (1), p = 0.01) and DSVR (to 1.9 (0.8), p = 0.09) and an increase in coronary resistance (to 1.91 (0.6), p = 0.02). This was probably related to an improvement in the systolic coronary flow. CONCLUSIONS: This study demonstrates that successful septal ablation in patients with symptomatic HCM results in immediate improvement in CFR, which is reduced in HCM partly because of the increased systolic contraction load.

Developing clinical indication for multisite pacing.

The artificial activation of the heart modifies the mechanics of contraction and relaxation. While only little basic research has been addressed to this question, clinical observations showed that for hypertrophic as well as dilated cardiomyopathies appropriate pacing techniques can be useful. Pacing can influence the activation sequence. The spread out from a single site is slow, and so hypercontractility deminshed. With the use of multiple electrodes, two atrial and/or two ventricular, conduction delays in the atria or ventricles can be eliminated. Synchronisation of the cardiac activation has an anti-arrhythmic and positiv inotropic effect. This may lead to new indications for pacemakers or better to be named cardiac synchronisers.

L'autopsie moléculaire de la mort subite cardiaque: de la salle d'autopsie au cabinet du praticien [Molecular autopsy of sudden cardiac death: from postmortem to clinical approach]

Sudden cardiac death is one of the most prevalent cause of death in developed countries. Its aetiology varies according to the age. Some cardiac diseases may explain sudden death with minimal or no anatomic findings. However, many cardiac diseases, as for example channelopathies and hypertrophic cardiomyopathy have a genetic basis. Therefore genetic analyses (molecular autopsy) are becoming a useful tool in forensic medicine to identify the cause of sudden cardiac death and to improve the early diagnosis of asymptomatic carriers among relatives.

Current variables, definitions and endpoints of the European cardiovascular magnetic resonance registry.

BACKGROUND: Cardiovascular magnetic resonance (CMR) is increasingly used in daily clinical practice. However, little is known about its clinical utility such as image quality, safety and impact on patient management. In addition, there is limited information about the potential of CMR to acquire prognostic information. METHODS: The European Cardiovascular Magnetic Resonance Registry (EuroCMR Registry) will consist of two parts: 1) Multicenter registry with consecutive enrolment of patients scanned in all participating European CMR centres using web based online case record forms. 2) Prospective clinical follow up of patients with suspected coronary artery disease (CAD) and hypertrophic cardiomyopathy (HCM) every 12 months after enrolment to assess prognostic data. CONCLUSION: The EuroCMR Registry offers an opportunity to provide information about the clinical utility of routine CMR in a large number of cases and a diverse population. Furthermore it has the potential to gather information about the prognostic value of CMR in specific patient populations.

Quantification of the local heartwall motion by magnetic resonance myocardial tagging.

Sophisticated magnetic resonance tagging techniques provide powerful tools for the non-invasive assessment of the local heartwall motion towards a deeper fundamental understanding of local heart function. For the extraction of motion data from the time series of magnetic resonance tagged images and for the visualization of the local heartwall motion a new image analysis procedure has been developed. New parameters have been derived which allows quantification of the motion patterns and are highly sensitive to any changes in these patterns. The new procedure has been applied for heart motion analysis in healthy volunteers and in patient collectives with different heart diseases. The achieved results are summarized and discussed.

Pathologic ventricular hypertrophy in the offspring of diabetic mothers: a retrospective study.

AIMS: Diabetes in pregnant women is increasing and with that the complications in their offspring. We studied our population of diabetic mothers (2003-2005) for pathologic ventricular hypertrophy (PVH). METHODS AND RESULTS: In our retrospective study of all 87 diabetic pregnancies (92 neonates), 16 were type 1, 17 were type 2, and 54 were gestational diabetes (GD). Haemoglobin glycated (HbA1c) median was 5.8% (5.3-6.5): 17 with HbA1c above normal 2 with congenital heart disease (CHD) and six with PVH. A total of 75 neonates were normal, five had CHD, and 12 had PVH (1/12 died post-natally, 1/12 stillborn, 2/12 required premature delivery, 8/12 normal). The 16 type 1 pregnancies resulted in three neonates with CHD and in 50% PVH, including one death, one premature Cesarean section because of PVH. The 17 neonates of type 2 pregnancies showed in one CHD and in 25% PVH. Of the 54 GD pregnancies, one had CHD and one had PVH. CONCLUSION: Pregnancies of both type 1 and 2 diabetes carry an increased risk for foetal development of PVH compared with those with GD. The insufficient effect of preventive glycaemia controls leads to conclude that although no definite predictive parameters for malignant outcome can be presented, close monitoring of these pregnancies may prevent perinatal catastrophes.

Altered high-energy phosphate metabolism predicts contractile dysfunction and subsequent ventricular remodeling in pressure-overload hypertrophy mice.

To study the role of early energetic abnormalities in the subsequent development of heart failure, we performed serial in vivo combined magnetic resonance imaging (MRI) and (31)P magnetic resonance spectroscopy (MRS) studies in mice that underwent pressure-overload following transverse aorta constriction (TAC). After 3 wk of TAC, a significant increase in left ventricular (LV) mass (74 +/- 4 vs. 140 +/- 26 mg, control vs. TAC, respectively; P < 0.000005), size [end-diastolic volume (EDV): 48 +/- 3 vs. 61 +/- 8 microl; P < 0.005], and contractile dysfunction [ejection fraction (EF): 62 +/- 4 vs. 38 +/- 10%; P < 0.000005] was observed, as well as depressed cardiac energetics (PCr/ATP: 2.0 +/- 0.1 vs. 1.3 +/- 0.4, P < 0.0005) measured by combined MRI/MRS. After an additional 3 wk, LV mass (140 +/- 26 vs. 167 +/- 36 mg; P < 0.01) and cavity size (EDV: 61 +/- 8 vs. 76 +/- 8 microl; P < 0.001) increased further, but there was no additional decline in PCr/ATP or EF. Cardiac PCr/ATP correlated inversely with end-systolic volume and directly with EF at 6 wk but not at 3 wk, suggesting a role of sustained energetic abnormalities in evolving chamber dysfunction and remodeling. Indeed, reduced cardiac PCr/ATP observed at 3 wk strongly correlated with changes in EDV that developed over the ensuing 3 wk. These data suggest that abnormal energetics due to pressure overload predict subsequent LV remodeling and dysfunction.

Dilated cardiomyopathy and impaired cardiac hypertrophic response to angiotensin II in mice lacking FGF-2.

FGF-2 has been implicated in the cardiac response to hypertrophic stimuli. Angiotensin II (Ang II) contributes to maintain elevated blood pressure in hypertensive individuals and exerts direct trophic effects on cardiac cells. However, the role of FGF-2 in Ang II-induced cardiac hypertrophy has not been established. Therefore, mice deficient in FGF-2 expression were studied using a model of Ang II-dependent hypertension and cardiac hypertrophy. Echocardiographic measurements show the presence of dilated cardiomyopathy in normotensive mice lacking FGF-2. Moreover, hypertensive mice without FGF-2 developed no compensatory cardiac hypertrophy. In wild-type mice, hypertrophy was associated with a stimulation of the c-Jun N-terminal kinase, the extracellular signal regulated kinase, and the p38 kinase pathways. In contrast, mitogen-activated protein kinase (MAPK) activation was markedly attenuated in FGF-2-deficient mice. In vitro, FGF-2 of fibroblast origin was demonstrated to be essential in the paracrine stimulation of MAPK activation in cardiomyocytes. Indeed, fibroblasts lacking FGF-2 expression have a defective capacity for releasing growth factors to induce hypertrophic responses in cardiomyocytes. Therefore, these results identify the cardiac fibroblast population as a primary integrator of hypertrophic stimuli in the heart, and suggest that FGF-2 is a crucial mediator of cardiac hypertrophy via autocrine/paracrine actions on cardiac cells.

Long-term miR-669a therapy alleviates chronic dilated cardiomyopathy in dystrophic mice.

BACKGROUND: Dilated cardiomyopathy (DCM) is a leading cause of chronic morbidity and mortality in muscular dystrophy (MD) patients. Current pharmacological treatments are not yet able to counteract chronic myocardial wastage, thus novel therapies are being intensely explored. MicroRNAs have been implicated as fine regulators of cardiomyopathic progression. Previously, miR-669a downregulation has been linked to the severe DCM progression displayed by Sgcb-null dystrophic mice. However, the impact of long-term overexpression of miR-669a on muscle structure and functionality of the dystrophic heart is yet unknown. METHODS AND RESULTS: Here, we demonstrate that intraventricular delivery of adeno-associated viral (AAV) vectors induces long-term (18 months) miR-669a overexpression and improves survival of Sgcb-null mice. Treated hearts display significant decrease in hypertrophic remodeling, fibrosis, and cardiomyocyte apoptosis. Moreover, miR-669a treatment increases sarcomere organization, reduces ventricular atrial natriuretic peptide (ANP) levels, and ameliorates gene/miRNA profile of DCM markers. Furthermore, long-term miR-669a overexpression significantly reduces adverse remodeling and enhances systolic fractional shortening of the left ventricle in treated dystrophic mice, without significant detrimental consequences on skeletal muscle wastage. CONCLUSIONS: Our findings provide the first evidence of long-term beneficial impact of AAV-mediated miRNA therapy in a transgenic model of severe, chronic MD-associated DCM.

Characterization of the role of AKAP-Lbc/p38 complex in the hypertrophic response of the heart

In response to chronic stress the heart undergoes an adverse remodeling process associated with cardiomyocyte hypertrophy, increased cellular apoptosis and fibrosis, which ultimately causes cardiac dysfunction and heart failure. Increasing evidence suggest the role of scaffolding and anchoring proteins in coordinating different signaling pathways that mediate the hypertrophic response of the heart. In this context, the family of Α-kinase anchoring proteins (AKAPs) emerged as important regulators of the cardiac function. During my thesis work I have conducted two independent projects, both of them aiming at elucidating the role of AKAPs in the heart. It has been shown that AKAP-Lbc, an anchoring protein that possesses an intrinsic Rho- specific exchange factor activity, organizes a signaling complex that links AKAP-Lbc- dependent activation of RhoA with the mitogen activated protein kinase (MAPK) p38. The first aim of my thesis was to study the role of this novel transduction pathway in the context of cardiac hypertrophy. Here we show that transgenic mice overexpressing in cardiomyocytes a competitor fragment of AKAP-Lbc, which specifically disrupts endogenous AKAP-Lbc / p38 complexes, developed early dilated cardiomyopathy in response to two weeks of transverse aortic constriction (TAC) as compared to controls. Interestingly, inhibition of the AKAP-Lbc / p38 transduction pathway significantly reduced the hypertrophic growth of single cardiomyocytes induced by pressure overload. Therefore, it appears that the AKAP- Lbc / p38 complex is crucially involved in the regulation of stress-induced cardiomyocyte hypertrophy and that disruption of this signaling pathway is detrimental for the heart under conditions of sustained hemodynamic stress. Secondly, in order to identify new AKAPs involved in the regulation of cardiac function, we followed a proteomic approach which allowed us to characterize AKAP2 as a major AKAP in the heart. Importantly, here we show that AKAP2 interacts with several proteins known to be involved in the control of gene transcription, such as the nuclear receptor coactivator 3 (NCoA3) or the ATP-dependent SWI/SNF chromatin remodeling complex. Thus, we propose AKAP2 as a novel mediator of cardiac gene expression through its interaction with these transcriptional regulators.

Sarcomeric M-band alterations as a marker for human dilated cardiomyopathy

Purpose: The M-band is an important cytoskeletal structure in the centre of the sarcomere, believed to cross-link the thick filament lattice. Its main components are three closely related modular proteins from the myomesin gene family: Myomesin, M-protein and myomesin-3. Each muscle is characterized by its unique M-band protein composition, depending on the contractile parameters of a particular fiber. To investigate the role of the M-band in one of the most relevant and clinically increasing cardiac diseases, we analyzed the expression of myomesin proteins in dilated cardiomyopathy (DCM).Methods: In a previous study we analyzed mouse models suffering from DCM, demonstrating that the embryonic heart specific EH-myomesin splicing isoform was up-regulated directly corresponding to the degree of cardiac dysfunction and ventricular dilation. Based on this study, human ventricular and atrial samples (n=32) were obtained during heart surgery after informed consent and approval by an institutional review board. Patients were aged 30-70 years and suffered from dilated cardiomyopathy (DCM;n=13), Hypertrophic Cardiomyopathy (HCM;n=10) or served as controls (n=9). Patients suffering from DCM or HCM were in endstage heart-failure (NYHA III-IV) and either underwent heart transplantation or Left Ventricular Assist Device (LVAD) implantation. Heart samples from patients who underwent valve surgery or congenital heart surgery served as controls. Heart Samples were analyzed using RT-PCR, Western blot, and immunofluorescence.Results: By investigating the expression pattern of myomesins, we found that DCM is accompanied by specific M-band alterations, which were more pronounced in ventricular samples compared to the atrium. Changes in the amounts of different myomesins during DCM occurred in a cell-specific manner, leading to a higher heterogeneity of the cytoskeleton in cardiomyocytes through the myocardial wall with some cells switching completely to an embryonic phenotype.Conclusions: Here we present that the embryonic heart specific EH-myomesin isoform is up-regulated in human DCM. The alterations of the M-band protein composition might be part of a general adaptation of the sarcomeric cytoskeleton to unfavorable working conditions in the failing heart and may modify the mechanical properties of the cardiomyocytes. We suggest that the upregulation of EH-myomesin might play a pivotal role in DCM and might support classical imagingas a novel sarcomeric marker for this disease.

EH-myomesin splice isoform is a novel marker for dilated cardiomyopathy.

The M-band is the prominent cytoskeletal structure that cross-links the myosin and titin filaments in the middle of the sarcomere. To investigate M-band alterations in heart disease, we analyzed the expression of its main components, proteins of the myomesin family, in mouse and human cardiomyopathy. Cardiac function was assessed by echocardiography and compared to the expression pattern of myomesins evaluated with RT-PCR, Western blot, and immunofluorescent analysis. Disease progression in transgenic mouse models for dilated cardiomyopathy (DCM) was accompanied by specific M-band alterations. The dominant splice isoform in the embryonic heart, EH-myomesin, was strongly up-regulated in the failing heart and correlated with a decrease in cardiac function (R = -0.86). In addition, we have analyzed the expressions of myomesins in human myocardial biopsies (N = 40) obtained from DCM patients, DCM patients supported by a left ventricular assist device (LVAD), hypertrophic cardiomyopathy (HCM) patients and controls. Quantitative RT-PCR revealed that the EH-myomesin isoform was up-regulated 41-fold (P < 0.001) in the DCM patients compared to control patients. In DCM hearts supported by a LVAD and HCM hearts, the EH-myomesin expression was comparable to controls. Immunofluorescent analyses indicate that EH-myomesin was enhanced in a cell-specific manner, leading to a higher heterogeneity of the myocytes' cytoskeleton through the myocardial wall. We suggest that the up-regulation of EH-myomesin denotes an adaptive remodeling of the sarcomere cytoskeleton in the dilated heart and might serve as a marker for DCM in mouse and human myocardium.