Myocardial late gadolinium enhancement cardiovascular magnetic resonance in hypertrophic cardiomyopathy caused by mutations in troponin I

A Case Report on Diagnostic Approach of a Complex Clinical Scenario: Differentiation Between Coronary Artery Disease and Apical Hypertrophic Cardiomyopathy as a Cause of Recurrent Debilitating Angina

Apical hypertrophic cardiomyopathy (ApHCM) is a clinical challenge when presenting with symptoms of angina plus shortness of breath. An appropriate diagnosis of concurrent coronary artery disease (CAD) is needed for proper diagnosis, risk stratification, and management. We present a case of a 64-year-old gentleman with a history of ApHCM and CAD with previous percutaneous intervention presenting with recurrent angina. A repeat coronary angiography showed no new obstructive lesions. A stress cardiac magnetic resonance imaging was performed, which showed perfusion defect in the apex with apical scarring likely secondary to microvascular disease. The patient was managed medically with the improvement of symptoms. Diagnosis and management of CAD in patients with ApHCM are challenging. Multiple diagnostic modalities may be required for delineating the underlying pathology. Patients should be managed initially with medications. If symptoms are not controlled with medical management, a heart team approach with referral to an advanced center experienced in apical myectomy should be considered.

A case report: Twin sisters with restrictive cardiomyopathy associated with rare mutations in the cardiac troponin I gene

Restrictive cardiomyopathy (RCM) is a rare cardiomyopathy in children, and its prognosis until now, has been poor. Recently some sarcomeric mutations have been reported as disease-causing genes of RCM. However, the genotype-phenotype correlation is not fully understood. Additionally, prognostic factors including sudden death in patients with RCM have not been elucidated. We report our experience in treating twin sisters with RCM or hypertrophic cardiomyopathy with RCM phenotype, both carriers of the same mutation in TNNI3, which encodes one of the major sarcomeric proteins in myofibrils. They were both diagnosed with RCM by cardiac catheterization at the age of 11 years. Despite appropriate follow-up and medical treatment, one died suddenly at the age of 11 years and the other also died at the age of 15 years due to heart failure while awaiting heart transplantation. In addition to our cases, other reports of younger fatal cases with RCM carrying TNNI3 mutations may suggest it as one of the prognostic factors. Genetic diagnosis is important in the clinical diagnosis, management, and treatment of cardiomyopathy. <Learning objective: Our cases involved twin sisters diagnosed with restrictive cardiomyopathy (RCM) with rare mutations in the cardiac troponin I. Based on their clinical course, this mutation appears to have a poor prognosis. It was reported that RCM was caused by sarcomere gene mutations, however, the relationship between genotype and phenotype is not clearly defined. To elucidate the prognosis of this rare disease not only the genetic mutations but the accumulation of various clinical outcomes is important.>.

Regional myocardial function at preclinical disease stage of hypertrophic cardiomyopathy in female gene variant carriers

We recently showed more severe diastolic dysfunction at the time of myectomy in female compared to male patients with obstructive hypertrophic cardiomyopathy. Early recognition of aberrant cardiac contracility using cardiovascular magnetic resonance (CMR) imaging may identify women at risk of cardiac dysfunction. To define myocardial function at an early disease stage, we studied regional cardiac function using CMR imaging with tissue tagging in asymptomatic female gene variant carriers. CMR imaging with tissue tagging was done in 13 MYBPC3, 11 MYH7 and 6 TNNT2 gene carriers and 16 age-matched controls. Regional peak circumferential strain was derived from tissue tagging images of the basal and midventricular segments of the septum and lateral wall. Left ventricular wall thickness and global function were comparable between MYBPC3, MYH7, TNNT2 carriers and controls. MYH7 gene variant carriers showed a different strain pattern as compared to the other groups, with higher septal peak circumferential strain at the basal segments compared to the lateral wall, whereas MYBPC3, TNNT2 carriers and controls showed higher strain at the lateral wall compared to the septum. Only subtle gene-specific changes in strain pattern occur in the myocardium preceding development of cardiac hypertrophy. Overall, our study shows that there are no major contractile deficits in asymptomatic females carrying a pathogenic gene variant, which would justify the use of CMR imaging for earlier diagnosis.

Progression of myocardial fibrosis in hypertrophic cardiomyopathy: mechanisms and clinical implications

Aims

Myocardial fibrosis as detected by late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) is a powerful prognostic marker in hypertrophic cardiomyopathy (HCM) and may be progressive. The precise mechanisms underlying fibrosis progression are unclear. We sought to assess the extent of LGE progression in HCM and explore potential causal mechanisms and clinical implications.

Methods and results

Seventy-two HCM patients had two CMR (CMR1-CMR2) at an interval of 5.7 ± 2.8 years with annual clinical follow-up for 6.3 ± 3.6 years from CMR1. A combined endpoint of heart failure progression, cardiac hospitalization, and new onset ventricular tachycardia was assessed. Cine and LGE imaging were performed to assess left ventricular (LV) mass, function, and fibrosis on serial CMR. Stress perfusion imaging and cardiac energetics were undertaken in 38 patients on baseline CMR (CMR1). LGE mass increased from median 4.98 g [interquartile range (IQR) 0.97–13.48 g] to 6.30 g (IQR 1.38–17.51 g) from CMR1 to CMR2. Substantial LGE progression (ΔLGE ≥ 4.75 g) occurred in 26% of patients. LGE increment was significantly higher in those with impaired myocardial perfusion reserve (<MPRI 1.40) and energetics (phosphocreatine/adenosine triphosphate <1.44) on baseline CMR (P ≤ 0.01 for both). Substantial LGE progression was associated with LV thinning, increased cavity size and reduced systolic function, and conferred a five-fold increased risk of subsequent clinical events (hazard ratio 5.04, 95% confidence interval 1.85–13.79; P = 0.002).

Conclusion

Myocardial fibrosis is progressive in some HCM patients. Impaired energetics and perfusion abnormalities are possible mechanistic drivers of the fibrotic process. Fibrosis progression is associated with adverse cardiac remodelling and predicts an increased risk of subsequent clinical events in HCM.

The Role of Cardiovascular Magnetic Resonance in Sports Cardiology; Current Utility and Future Perspectives

Purpose of review

Cardiovascular magnetic resonance (CMR) is frequently used in the investigation of suspected cardiac disease in athletes. In this review, we discuss how CMR can be used in athletes with suspected cardiomyopathy with particular reference to volumetric analysis and tissue characterization. We also discuss the finding of non-ischaemic fibrosis in athletes describing its prevalence, distribution and clinical importance.

Recent findings

The strengths of CMR include high spatial resolution, unrestricted imaging planes and lack of ionizing radiation. Regular physical exercise leads to cardiac remodeling that in certain situations can be clinically challenging to differentiate from various cardiomyopathies. Thorough morphological assessment by CMR is fundamental to ensuring accurate diagnosis. Developments in tissue characterization by late gadolinium enhancement and T1 mapping have the potential to be powerful additional tools in this challenging clinical situation. Using late gadolinium enhancement, it is also possible to detect non-ischaemic fibrosis in athletes who do not have overt cardiomyopathy. The mechanisms of this fibrosis are unclear; however, it does appear to be clinically important. We also review data on the prevalence of non-ischaemic fibrosis in athletes.

Summary

CMR is a powerful tool to aid in the diagnosis of cardiomyopathy in athletes. It may also have a future role in assessing fibrosis related to long-term participation in sport.

Delayed Myocardial Enhancement in Pediatric Hypertrophic Cardiomyopathy: Correlation with LV Function, Echocardiography, and Demographic Parameters

Our aim was (1) to detect the presence of fibrosis by Cardiac magnetic resonance imaging (CMR) in the pediatric age group. (2) Correlate CMR findings with demographic data, LV function, and other echocardiographic parameters. We studied 40 pediatric patients diagnosed as HCM by echocardiography. All patients were subjected to clinical examination (in which the NYHA classification was determined for each patient), echocardiography, and CMR. CMR was done on a 1.5T Philips Achieva scanner in SSFP with delayed myocardial enhancement (DE-MRI). All demographic and functional parameters as well as pressure gradient across left ventricular outflow tract (LVOT) were correlated with the percentage of myocardial enhancement. We studied 13 female and 27 male patients from 45 days up to 18 years. The mean percentage of DE-MRI was 9.7 ± 9%. We found significant correlation between the NYHA classification and the pressure gradient across the LVOT (P = < 0.001) as well as the percentage of DE-MRI (P = 0.004). The percentage of DE-MRI showed positive correlation with LV myocardial mass index (P = 0.042). It didn't correlate with any other demographic or LV functional cardiac parameters. A good positive correlation was detected between the percentage of DE-MRI and the severity of pressure gradient across LVOT measured by echocardiography (r = 0.69 and P = <0.001). We found a significant correlation between the percentage of DE-MRI in children with HCM and the pressure gradient across LVOT, NYHA classification, and LV myocardial mass. This may help in the further management of those patients, planning for follow-up, and prognosis of the disease.

Diagnostic disparity and identification of two TNNI3 gene mutations, one novel and one arising de novo, in South African patients with restrictive cardiomyopathy and focal ventricular hypertrophy

INTRODUCTION

The minimum criterion for the diagnosis of hypertrophic cardiomyopathy (HCM) is thickening of the left ventricular wall, typically in an asymmetrical or focal fashion, and it requires no functional deficit. Using this criterion, we identified a family with four affected individuals and a single unrelated individual essentially with restrictive cardiomyopathy (RCM). Mutations in genes coding for the thin filaments of cardiac muscle have been described in RCM and HCM with 'restrictive features'. One such gene encodes for cardiac troponin I (TNNI3), a sub-unit of the troponin complex involved in the regulation of striated muscle contraction. We hypothesised that mutations in TNNI3 could underlie this particular phenotype, and we therefore screened TNNI3 for mutations in 115 HCM probands.

METHODS

Clinical investigation involved examination, echocardiography, chest X-ray and an electrocardiogram of both the index cases and close relatives. The study cohort consisted of 113 South African HCM probands, with and without known founder HCM mutations, and 100 ethnically matched control individuals. Mutation screening of TNNI3 for diseasecausing mutations were performed using high-resolution melt (HRM) analysis.

RESULTS

HRM analyses identified three previously described HCM-causing mutations (p.Pro82Ser, p.Arg162Gln, p.Arg170Gln) and a novel exonic variant (p.Leu144His). A previous study involving the same amino acid identified a p.Leu144Gln mutation in a patient presenting with RCM, with clinical features of HCM. We observed the novel p.Leu144His mutation in three siblings with clinical RCM and varying degrees of ventricular hypertrophy. The isolated index case with the de novo p.Arg170Gln mutation presented with a similar phenotype. Both mutations were absent in a healthy control group.

CONCLUSION

We have identified a novel disease-causing p.Leu144His mutation and a de novo p.Arg170Gln mutation associated with RCM and focal ventricular hypertrophy, often below the typical diagnostic threshold for HCM. Our study provides information regarding TNNI3 mutations underlying RCM in contrast to other causes of a similar presentation, such as constrictive pericarditis or infiltration of cardiac muscle, all with marked right-sided cardiac manifestations. This study therefore highlights the need for extensive mutation screening of genes encoding for sarcomeric proteins, such as TNNI3 to identify the underlying cause of this particular phenotype.

From Left Ventricular Hypertrophy to Dysfunction and Failure

Left ventricular hypertrophy (LVH) is growth in left ventricular mass caused by increased cardiomyocyte size. LVH can be a physiological adaptation to strenuous physical exercise, as in athletes, or it can be a pathological condition, which is either genetic or secondary to LV overload. Physiological LVH is usually benign and regresses upon reduction/cessation of physical activity. Pathological LVH is a compensatory phenomenon, which eventually may become maladaptive and evolve towards progressive LV dysfunction and heart failure (HF). Both interstitial and replacement fibrosis play a major role in the progressive decompensation of the hypertrophied LV. Coronary microvascular dysfunction (CMD) and myocardial ischemia, which have been demonstrated in most forms of pathological LVH, have an important pathogenetic role in the formation of replacement fibrosis and both contribute to the evolution towards LV dysfunction and HF. Noninvasive imaging allows detection of myocardial fibrosis and CMD, thus providing unique information for the stratification of patients with LVH. (Circ J 2016; 80: 555-564).

Targeted Next-Generation Sequencing Reveals Hot Spots and Doubly Heterozygous Mutations in Chinese Patients with Familial Cardiomyopathy

As a common cardiac disease mainly caused by gene mutations in sarcomeric cytoskeletal, calcium-handling, nuclear envelope, desmosomal, and transcription factor genes, inherited cardiomyopathy is becoming one of the major etiological factors of sudden cardiac death (SCD) and heart failure (HF). This disease is characterized by remarkable genetic heterogeneity, which makes it difficult to screen for pathogenic mutations using Sanger sequencing. In the present study, three probands, one with familial hypertrophic cardiomyopathy (FHCM) and two with familial dilated cardiomyopathy (FDCM), were recruited together with their respective family members. Using next-generation sequencing technology (NGS), 24 genes frequently known to be related to inherited cardiomyopathy were screened. Two hot spots (TNNI3-p.Arg145Gly, and LMNA-p.Arg190Trp) and double (LMNA-p.Arg190Trp plus MYH7-p.Arg1045His) heterozygous mutations were found to be highly correlated with familial cardiomyopathy. FDCM patients with doubly heterozygous mutations show a notably severe phenotype as we could confirm in our study; this indicates that the double mutations had a dose effect. In addition, it is proposed that genetic testing using NGS technology can be used as a cost-effective screening tool and help guide the treatment of patients with familial cardiomyopathy particularly regarding the risk of family members who are clinically asymptomatic.

Cardiac MRI: a central prognostic tool in myocardial fibrosis

Fibrotic remodelling of the extracellular matrix is a healing mechanism necessary immediately after myocardial injury. However, prolonged increase in myocardial fibrotic activity results in stiffening of the myocardium and heralds adverse outcomes related to systolic and diastolic dysfunction, as well as arrhythmogenesis. Cardiac MRI provides a noninvasive phenotyping tool for accurate and easy detection and quantification of myocardial fibrosis by probing the retention of gadolinium-contrast agent in myocardial tissue. Late-gadolinium enhancement (LGE) cardiac MRI has been used extensively in a large number of studies for measurement of myocardial scarring. T1 mapping, a fairly new technique that can be used to identify the exact T1 value of the tissue, provides a direct measurement of the extracellular volume fraction of the myocardium. In contrast to LGE, T1 mapping can be used to measure diffuse myocardial fibrosis and differentiate between disease processes. In this Review, we describe the basic principles of imaging myocardial fibrosis using contrast-enhanced MRI and summarize its use for prognostic purposes.

Predictive value of myocardial delayed enhancement in Duchenne muscular dystrophy

In other cardiomyopathies, cardiac magnetic resonance imaging (CMR)-derived myocardial delayed enhancement (MDE), a marker of myocardial fibrosis, is a risk factor for sudden cardiac death (SCD). In Duchenne muscular dystrophy (DMD), the prognostic value of MDE for ventricular arrhythmias and death is unknown. This study aimed to evaluate associations between MDE and electrocardiographic (ECG) changes, ventricular remodeling, risk of arrhythmias, and death in DMD. This retrospective study included all subjects with DMD who had undergone a CMR between January 2006 and December 2011 and had available ECG and 24-h Holter records from the same period. Left ventricular (LV) MDE was semiquantitatively graded from 0 to 4. Comparisons of demographic and clinical characteristics between MDE and no-MDE groups were made. Cox regression analysis was performed to assess factors associated with death. This study investigated 32 boys with a median age of 13.8 years (range, 7.2-17.4 years) and found MDE present in 25 (78 %) of the boys. Compared with the no-MDE subjects, the MDE subjects were older (15.7 ± 3.3 vs 12.1 ± 4.8 years) and had a wider QT dispersion (QTd: 74 ± 30 vs 55 ± 33 ms), a higher incidence of ventricular tachycardia (40 vs 0 %), a lower LV ejection fraction (46 ± 12 vs 56 ± 9 %), a larger LV end-diastolic volume (124 ± 58 vs 68 ± 14 ml/m(2)), and a larger end-systolic volume (57 ± 29 vs 28 ± 10 ml/m(2)) (p < 0.05 for all). During the study period, six of the subjects (19 %) died. The factors associated with mortality were increased age, advanced grade of MDE, higher LV end-systolic volume, lower LV ejection fraction, use of beta-blockers, and ventricular tachycardia. Myocardial fibrosis detected by CMR is an independent predictor of adverse cardiac remodeling, ventricular arrhythmias, and death in DMD. Cardiac MRI using MDE can be applied as a screening tool to detect patients at risk for ventricular arrhythmias, more advanced disease, adverse LV remodeling, and death.

Role of late gadolinium enhancement cardiovascular magnetic resonance in the risk stratification of hypertrophic cardiomyopathy

OBJECTIVE

Myocardial fibrosis identified by late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) in patients with hypertrophic cardiomyopathy (HCM) is associated with adverse cardiovascular events, but its value as an independent risk factor for sudden cardiac death (SCD) is unknown. We investigated the role of LGE-CMR in the risk stratification of HCM.

METHODS

We conducted a prospective cohort study in a tertiary referral centre. Consecutive patients with HCM (n=711, median age 56.3 years, IQR 46.7-66.6; 70.0% male) underwent LGE-CMR and were followed for a median 3.5 years. The primary end point was SCD or aborted SCD.

RESULTS

Overall, 471 patients (66.2%) had myocardial fibrosis (median 5.9% of left ventricular mass, IQR: 2.2-13.3). Twenty-two (3.1%) reached the primary end point. The extent but not the presence of fibrosis was a significant univariable predictor of the primary end point (HR per 5% LGE: 1.24, 95% CI 1.06 to 1.45; p=0.007 and HR for LGE: 2.69, 95% CI 0.91 to 7.97; p=0.073, respectively). However, on multivariable analysis, only LV-EF remained statistically significant (HR: 0.92, 95% CI 0.89 to 0.95; p<0.001). For the secondary outcome of cardiovascular mortality/aborted SCD, the presence and the amount of fibrosis were significant predictors on univariable but not multivariable analysis after adjusting for LV-EF and non-sustained ventricular tachycardia.

CONCLUSIONS

The amount of myocardial fibrosis was a strong univariable predictor of SCD risk. However, this effect was not maintained after adjusting for LV-EF. Further work is required to elucidate the interrelationship between fibrosis and traditional predictors of outcome in HCM.

Fibrosis markers and CRIM1 increase in chronic heart failure of increasing severity

BACKGROUND

Fibrosis suppressors/activators in chronic heart failure (CHF) is a topic of investigation.

AIM

To quantify serum levels of fibrosis regulators in CHF.

METHODS

ELISA tests were used to quantify fibrosis regulators, procollagen type-(PIP)I, (PIP)III, collagen-I, III, BMP1,2,3,7, SDF1α, CXCR4, fibulin 1,2,3, BMPER, CRIM1 and BAMBI in 66 CHF (NYHA class I, n = 9; II, n = 34; III n = 23), and in 14 controls.

RESULTS

In CHF, TGFβR2, PIPIII, SDF1α and CRIM1 were increased. PIPIII correlated with CRIM1.

CONCLUSIONS

The BMPs inhibitor CRIM1 is increased and correlates with higher levels of serum PIPIII showing an imbalance in favor of pro-fibrotic mechanisms in CHF.

Comparison of echocardiographic and cardiac magnetic resonance imaging in hypertrophic cardiomyopathy sarcomere mutation carriers without left ventricular hypertrophy

BACKGROUND

Left ventricular hypertrophy (LVH) typically manifests during or after adolescence in sarcomere mutation carriers at risk for developing hypertrophic cardiomyopathy. Guidelines recommend serial imaging of mutation carriers without LVH (G+/LVH-) to monitor for phenotypic evolution, but the optimal strategy is undefined. Compared with echocardiography (echo), cardiac MRI (CMR) offers improved endocardial visualization and potential to assess scar. However, the incremental advantage offered by CMR for early diagnosis of hypertrophic cardiomyopathy is unclear. Therefore, we systematically compared echo and CMR in G+/LVH- subjects.

METHODS AND RESULTS

A total of 40 sarcomere mutation carriers with normal echo wall thickness (<12 mm or z score <2.5 in children) underwent concurrent CMR. Mean age was 21.7±11.1 years, 55% were female. If left ventricular wall thickness seemed nonuniform, the size and location of relatively thickened segments were noted. Late gadolinium enhancement was assessed with CMR. Diagnostic agreement between echo and CMR was good (90%), although CMR measurements of left ventricular wall thickness were ≈19% lower than echo. Four subjects had mild hypertrophy (12.6-14 mm; ≤2 segments) appreciated by CMR but not echo. No subjects had late gadolinium enhancement. During median 35-month follow-up, 2 subjects developed overt hypertrophic cardiomyopathy, including 1 with mild LVH by CMR at baseline.

CONCLUSIONS

Echo is unlikely to miss substantial LVH; however, CMR identified mild hypertrophy in ≈10% of mutation carriers with normal echo wall thickness. CMR may be a useful adjunct in hypertrophic cardiomyopathy family screening, particularly in higher risk situations, or if echocardiographic images are suboptimal or suggest borderline LVH.

Myocardial extracellular volume fraction from T1 measurements in healthy volunteers and mice: relationship to aging and cardiac dimensions

OBJECTIVES

This study aimed to test the characteristics of the myocardial extracellular volume fraction (ECV) derived from pre- and post-contrast T1 measurements among healthy volunteers.

BACKGROUND

Cardiac magnetic resonance (CMR) T1 measurements of myocardium and blood before and after contrast allow quantification of the ECV, a tissue parameter that has been shown to change in proportion to the connective tissue fraction.

METHODS

Healthy volunteers underwent standard CMR imaging with administration of gadolinium. T1 measurements were performed with a Look-Locker sequence followed by gradient-echo acquisition. We tested the segmental, interslice, inter-, intra-, and test-retest characteristics of the ECV, as well as the association of the ECV with other variables. Juvenile and aged mice underwent a similar protocol, and cardiac sections were harvested for measurement of fibrosis.

RESULTS

In healthy volunteers (N = 32, 56% female; age 21 to 72 years), the ECV averaged 0.28 ± 0.03 (range 0.23 to 0.33). The intraclass coefficients for the intraobserver, interobserver, and test-retest absolute agreements of the ECV were 0.94 (95% confidence interval: 0.84 to 0.98), 0.93 (95% confidence interval: 0.80 to 0.98), and 0.95 (95% confidence interval: 0.52 to 0.99), respectively. In volunteers, the ECV was associated with age (r = 0.74, p < 0.001), maximal left atrial volume index (r = 0.67, p < 0.001), and indexed left ventricular mass. There were no differences in the ECV between segments in a slice or between slices. In mice (N = 12), the myocardial ECV ranged from 0.20 to 0.32 and increased with age (0.22 ± 0.02 vs. 0.30 ± 0.02, juvenile vs. aged mice, p < 0.001). In mice, the ECV correlated with the extent of myocardial fibrosis (r = 0.94, p < 0.001).

CONCLUSIONS

In healthy volunteers, the myocardial ECV ranges from 0.23 to 0.33, has acceptable test characteristics, and is associated with age, left atrial volume, and left ventricular mass. In mice, the ECV also increases with age and strongly correlates with the extent of myocardial fibrosis.

T1 measurements identify extracellular volume expansion in hypertrophic cardiomyopathy sarcomere mutation carriers with and without left ventricular hypertrophy

BACKGROUND

Myocardial fibrosis is a hallmark of hypertrophic cardiomyopathy (HCM) and a potential substrate for arrhythmias and heart failure. Sarcomere mutations seem to induce profibrotic changes before left ventricular hypertrophy (LVH) develops. To further evaluate these processes, we used cardiac magnetic resonance with T1 measurements on a genotyped HCM population to quantify myocardial extracellular volume (ECV).

METHODS AND RESULTS

Sarcomere mutation carriers with LVH (G+/LVH+, n=37) and without LVH (G+/LVH-, n=29), patients with HCM without mutations (sarcomere-negative HCM, n=11), and healthy controls (n=11) underwent contrast cardiac magnetic resonance, measuring T1 times pre- and postgadolinium infusion. Concurrent echocardiography and serum biomarkers of collagen synthesis, hemodynamic stress, and myocardial injury were also available in a subset. Compared with controls, ECV was increased in patients with overt HCM, as well as G+/LVH- mutation carriers (ECV=0.36±0.01, 0.33±0.01, 0.27±0.01 in G+/LVH+, G+/LVH-, controls, respectively; P≤0.001 for all comparisons). ECV correlated with N-terminal probrain natriuretic peptide levels (r=0.58; P<0.001) and global E' velocity (r=-0.48; P<0.001). Late gadolinium enhancement was present in >60% of overt patients with HCM but absent from G+/LVH- subjects. Both ECV and late gadolinium enhancement were more extensive in sarcomeric HCM than sarcomere-negative HCM.

CONCLUSIONS

Myocardial ECV is increased in HCM sarcomere mutation carriers even in the absence of LVH. These data provide additional support that fibrotic remodeling is triggered early in disease pathogenesis. Quantifying ECV may help characterize the development of myocardial fibrosis in HCM and ultimately assist in developing novel disease-modifying therapy, targeting interstitial fibrosis.

The diagnosis of hypertrophic cardiomyopathy by cardiovascular magnetic resonance

Hypertrophic cardiomyopathy (HCM) is the most common genetic disease of the heart. HCM is characterized by a wide range of clinical expression, ranging from asymptomatic mutation carriers to sudden cardiac death as the first manifestation of the disease. Over 1000 mutations have been identified, classically in genes encoding sarcomeric proteins. Noninvasive imaging is central to the diagnosis of HCM and cardiovascular magnetic resonance (CMR) is increasingly used to characterize morphologic, functional and tissue abnormalities associated with HCM. The purpose of this review is to provide an overview of the clinical, pathological and imaging features relevant to understanding the diagnosis of HCM. The early and overt phenotypic expression of disease that may be identified by CMR is reviewed. Diastolic dysfunction may be an early marker of the disease, present in mutation carriers prior to the development of left ventricular hypertrophy (LVH). Late gadolinium enhancement by CMR is present in approximately 60% of HCM patients with LVH and may provide novel information regarding risk stratification in HCM. It is likely that integrating genetic advances with enhanced phenotypic characterization of HCM with novel CMR techniques will importantly improve our understanding of this complex disease.

Recurrent and founder mutations in the Netherlands: cardiac Troponin I (TNNI3) gene mutations as a cause of severe forms of hypertrophic and restrictive cardiomyopathy

BACKGROUND

About 2-7% of familial cardiomyopathy cases are caused by a mutation in the gene encoding cardiac troponin I (TNNI3). The related clinical phenotype is usually severe with early onset. Here we report on all currently known mutations in the Dutch population and compared these with those described in literature.

METHODS

TheTNNI3 gene was screened for mutations in all coding exons and flanking intronic sequences in a large cohort of cardiomyopathy patients. All Dutch index cases carrying a TNNI3 mutation that are described in this study underwent extensive cardiological evaluation and were listed by their postal codes.

RESULTS

In 30 families, 14 different mutations were identified. Three TNNI3 mutations were found relatively frequently in both familial and non-familial cases of hypertrophic cardiomyopathy (HCM) or restrictive cardiomyopathy (RCM). Haplotype analysis showed that p.Arg145Trp and p.Ser166Phe are founder mutations in the Netherlands, while p.Glu209Ala is not. The majority of Dutch TNNI3 mutations were associated with a HCM phenotype. Mean age at diagnosis was 36.5 years. Mutations causing RCM occurred less frequently, but were identified in very young children with a poor prognosis.

CONCLUSION

In line with previously published data, we found TNNI3 mutations to be rare and associated with early onset and severe clinical presentation.

New Paradigms in Hypertrophic Cardiomyopathy: Insights from Genetics

Understanding the genetic basis of hypertrophic cardiomyopathy (HCM) provides a remarkable opportunity to predict and prevent disease. HCM is caused by mutations in sarcomere genes and is the most common monogenic cardiovascular disorder. Although unexplained left ventricular hypertrophy (LVH) is considered diagnostic, LVH is not always present. LV wall thickness is often normal until adolescence or later, even in individuals known to carry pathogenic sarcomere mutations. In contrast, genetic testing can identify both individuals who carry pathogenic sarcomere mutations and have a clinical diagnosis of HCM, as well as mutation carriers who have not yet manifest LVH but are at very likely to develop disease. Studying this important new patient subset, designated early or preclinical HCM, allows characterization of the initial consequences of sarcomere mutations, prior to the onset of overt hypertrophic remodeling. Such study has defined novel early phenotypes, including impaired left ventricular relaxation, myocardial energetic deficiencies, and altered collagen metabolism, in mutation carriers with apparently normal cardiac morphology. These results indicate that sarcomere mutations have substantial impact on myocardial function and biochemistry before the onset of frank hypertrophy. Furthermore, animal models of preclinical HCM have identified promising new treatment strategies that may diminish the emergence of overt disease. We can now begin to reshape the paradigm for treating genetic disorders. With improved mechanistic insight and the capability for early diagnosis, genetic advances can lead to new approaches for disease modification and prevention.

Imaging hypertrophic heart diseases with cardiovascular MR

The assessment of ventricular hypertrophy is an increasingly common indication for cardiac MR (CMR) in every day clinical practice. CMR is useful to confirm the presence of hypertrophy and to help to define the underlying cause through a combination of a detailed assessment of ventricular function and tissue characterising sequences. As well as being a useful diagnostic tool, some CMR imaging features are of prognostic significance. In this article, we review the typical appearances of common forms of ventricular hypertrophy, focussing principally on left ventricular hypertrophy, and demonstrate the techniques that can be used to differentiate one form of hypertrophy from another.

Midregional pro-atrial natriuretic peptide: a novel marker of myocardial fibrosis in patients with hypertrophic cardiomyopathy

We aimed to determine the diagnostic performance of biomarkers in predicting myocardial fibrosis assessed by late gadolinium enhancement (LGE) cardiovascular magnetic resonance imaging (CMR) in patients with hypertrophic cardiomyopathy (HCM). LGE CMR was performed in 40 consecutive patients with HCM. Left and right ventricular parameters, as well as the extent of LGE were determined and correlated to the plasma levels of midregional pro-atrial natriuretic peptide (MR-proANP), midregional pro-adrenomedullin (MR-proADM), carboxy-terminal pro-endothelin-1 (CT-proET-1), carboxy-terminal pro-vasopressin (CT-proAVP), matrix metalloproteinase-9 (MMP-9), tissue inhibitor of metalloproteinase-1 (TIMP-1) and interleukin-8 (IL-8). Myocardial fibrosis was assumed positive, if CMR indicated LGE. LGE was present in 26 of 40 patients with HCM (65%) with variable extent (mean: 14%, range: 1.3-42%). The extent of LGE was positively associated with MR-proANP (r = 0.4; P = 0.01). No correlations were found between LGE and MR-proADM (r = 0.1; P = 0.5), CT-proET-1 (r = 0.07; P = 0.66), CT-proAVP (r = 0.16; P = 0.3), MMP-9 (r = 0.01; P = 0.9), TIMP-1 (r = 0.02; P = 0.85), and IL-8 (r = 0.02; P = 0.89). After adjustment for confounding factors, MR-proANP was the only independent predictor associated with the presence of LGE (P = 0.007) in multivariate analysis. The area under the ROC curve (AUC) indicated good predictive performance (AUC = 0.882) of MR-proANP with respect to LGE. The odds ratio was 1.268 (95% confidence interval 1.066-1.508). The sensitivity of MR-proANP at a cut-off value of 207 pmol/L was 69%, the specificity 94%, the positive predictive value 90% and the negative predictive value 80%. The results imply that MR-proANP serves as a novel marker of myocardial fibrosis assessed by LGE CMR in patients with HCM.

Myocardial fibrosis as an early manifestation of hypertrophic cardiomyopathy

BACKGROUND

Myocardial fibrosis is a hallmark of hypertrophic cardiomyopathy and a proposed substrate for arrhythmias and heart failure. In animal models, profibrotic genetic pathways are activated early, before hypertrophic remodeling. Data showing early profibrotic responses to sarcomere-gene mutations in patients with hypertrophic cardiomyopathy are lacking.

METHODS

We used echocardiography, cardiac magnetic resonance imaging (MRI), and serum biomarkers of collagen metabolism, hemodynamic stress, and myocardial injury to evaluate subjects with hypertrophic cardiomyopathy and a confirmed genotype.

RESULTS

The study involved 38 subjects with pathogenic sarcomere mutations and overt hypertrophic cardiomyopathy, 39 subjects with mutations but no left ventricular hypertrophy, and 30 controls who did not have mutations. Levels of serum C-terminal propeptide of type I procollagen (PICP) were significantly higher in mutation carriers without left ventricular hypertrophy and in subjects with overt hypertrophic cardiomyopathy than in controls (31% and 69% higher, respectively; P<0.001). The ratio of PICP to C-terminal telopeptide of type I collagen was increased only in subjects with overt hypertrophic cardiomyopathy, suggesting that collagen synthesis exceeds degradation. Cardiac MRI studies showed late gadolinium enhancement, indicating myocardial fibrosis, in 71% of subjects with overt hypertrophic cardiomyopathy but in none of the mutation carriers without left ventricular hypertrophy.

CONCLUSIONS

Elevated levels of serum PICP indicated increased myocardial collagen synthesis in sarcomere-mutation carriers without overt disease. This profibrotic state preceded the development of left ventricular hypertrophy or fibrosis visible on MRI. (Funded by the National Institutes of Health and others.)

Prognostic significance of myocardial fibrosis in hypertrophic cardiomyopathy

OBJECTIVES

We investigated the significance of fibrosis detected by late gadolinium enhancement cardiovascular magnetic resonance for the prediction of major clinical events in hypertrophic cardiomyopathy (HCM).

BACKGROUND

The role of myocardial fibrosis in the prediction of sudden death and heart failure in HCM is unclear with a lack of prospective data.

METHODS

We assessed the presence and amount of myocardial fibrosis in HCM patients and prospectively followed them for the development of morbidity and mortality in patients over 3.1 +/- 1.7 years.

RESULTS

Of 217 consecutive HCM patients, 136 (63%) showed fibrosis. Thirty-four of the 136 patients (25%) in the fibrosis group but only 6 of 81 (7.4%) patients without fibrosis reached the combined primary end point of cardiovascular death, unplanned cardiovascular admission, sustained ventricular tachycardia or ventricular fibrillation, or appropriate implantable cardioverter-defibrillator discharge (hazard ratio [HR]: 3.4, p = 0.006). In the fibrosis group, overall risk increased with the extent of fibrosis (HR: 1.18/5% increase, p = 0.008). The risk of unplanned heart failure admissions, deterioration to New York Heart Association functional class III or IV, or heart failure-related death was greater in the fibrosis group (HR: 2.5, p = 0.021), and this risk increased as the extent of fibrosis increased (HR: 1.16/5% increase, p = 0.017). All relationships remained significant after multivariate analysis. The extent of fibrosis and nonsustained ventricular tachycardia were univariate predictors for arrhythmic end points (sustained ventricular tachycardia or ventricular fibrillation, appropriate implantable cardioverter-defibrillator discharge, sudden cardiac death) (HR: 1.30, p = 0.014). Nonsustained ventricular tachycardia remained an independent predictor of arrhythmic end points after multivariate analysis, but the extent of fibrosis did not.

CONCLUSIONS

In patients with HCM, myocardial fibrosis as measured by late gadolinium enhancement cardiovascular magnetic resonance is an independent predictor of adverse outcome. (The Prognostic Significance of Fibrosis Detection in Cardiomyopathy; NCT00930735).

Cardiac magnetic resonance in hypertrophic cardiomyopathy: current state of the art

Hypertrophic cardiomyopathy is a complex disorder with significant heterogeneity in clinical characteristics and natural history. Traditionally, the diagnosis has been based on clinical assessment and echocardiography; however, persistent challenges in its noninvasive evaluation remain. Hence, improved diagnostic techniques could lead to better risk stratification of patients, which would potentially identify patients likely to benefit from effective therapies. Recent studies have demonstrated the increasing utility of cardiac magnetic resonance in the management of this disease. With the increasing utilization of genetics, cardiac magnetic resonance is likely to play an even more important role in discerning the subtle morphologic differences seen in such patients with similar genotypic profiles.

Hypertrophic cardiomyopathy family with double-heterozygous mutations; does disease severity suggest doubleheterozygosity?

Background. With the improvement in genetic testing over time, double-heterozygous mutations are more often found by coincidence in families with hypertrophic cardiomyopathy (HCM). Double heterozygosity can be a cause of the wellknown clinical diversity within HCM families.Methods and results. We describe a family in which members carry either a single mutation or are double heterozygous for mutations in myosin heavy chain gene (MYH7) and cysteine and glycine-rich protein 3 (CSRP3). The described family emphasises the idea of a more severe clinical phenotype with double-heterozygous mutations. It also highlights the importance of cardiological screening where NT-proBNP may serve as an added diagnostic tool.Conclusion. With a more severe inexplicable phenotype of HCM within a family, one should consider the possibility of double-heterozygous mutations. This implies that in such families, even when one disease-causing mutation is found, all the family members still have an implication for cardiological screening parallel to extended genetic screening. (Neth Heart J 2009;17:458-63.).

Hypertrophic cardiomyopathy: preclinical and early phenotype

Hypertrophic cardiomyopathy (HCM) is caused by dominant mutations in sarcomere genes. Although the diagnosis of HCM is traditionally based on identifying unexplained left ventricular hypertrophy (LVH) by cardiac imaging, LVH is not an invariable feature of disease. The expression of LVH is highly age-dependent, and LV wall thickness is typically normal during childhood. Overt cardiac hypertrophy often does not develop until adolescence or later. With genetic testing, family members who have inherited a pathogenic sarcomere mutation (G+) can be identified prior to a clinical diagnosis (LVH-). This allows characterization of a new and important subset, denoted preclinical HCM (G+/LVH-). Although there are no distinguishing morphologic features of early disease, there is evidence of myocardial dysfunction prior to the development of LVH. Otherwise healthy sarcomere mutation carriers frequently have subtle impairment of diastolic function, detectable by tissue Doppler interrogation. These findings can assist in differentiating such at-risk family members from those who did not inherit the mutation, despite the presence of normal LV wall thickness. In contrast, systolic function appears relatively preserved in preclinical HCM but impaired in overt disease, suggesting that both the sarcomere mutation and the characteristic changes in myocardial architecture (LVH, fibrosis, and disarray) are required to perturb force generation. Better characterization of preclinical HCM will identify the initial manifestations of sarcomere mutations, characterize intermediate disease phenotypes, and foster efforts to develop novel therapeutic strategies based on genetic identification of at-risk individuals and early initiation of therapy to prevent disease progression when treatment may be most effective.

Identifying the etiology: a systematic approach using delayed-enhancement cardiovascular magnetic resonance

In patients who have heart failure, treatment and survival are directly related to the cause. Clinically, as a practical first step, patients are classified as having either ischemic or non-ischemic cardiomyopathy, a delineation usually based on the presence or absence of epicardial coronary artery disease. However, this approach does not account for patients with non-ischemic cardiomyopathy who also have coronary artery disease, which may be either incidental or partly contributing to myocardial dysfunction (mixed cardiomyopathy). By allowing direct assessment of the myocardium, delayed-enhancement cardiovascular magnetic resonance (DE-CMR) may aid in addressing these conundrums. This article explores the use of DE-CMR in identifying ischemic and non-ischemic myopathic processes and details a systematic approach to determine the cause of cardiomyopathy.

Extent of late gadolinium enhancement in cardiovascular magnetic resonance and its relation with left ventricular diastolic function in patients with hypertrophic cardiomyopathy

BACKGROUND

The aim of this study was to determine whether the extent of late gadolinium enhancement (LGE) is associated with left ventricular (LV) function in patients with hypertrophic cardiomyopathy (HCM).

METHODS AND RESULTS

Forty-seven patients with HCM (35 males, mean age 53+/-14, 14 with LV outflow tract obstruction) underwent cardiovascular magnetic resonance imaging and comprehensive echocardiographic examination. The extent of LGE was expressed as LGE volume and LGE percentage of LV volume. LGE was present in 40 (85.1%) of 47 patients. The mean LGE volume was 36.5+/-36 cm3, and the mean percentage of LV volume was 16.4+/-17%. Following adjustment for age, mitral regurgitation and LV mass index, LGE volume and percentage positively correlated with the left atrial volume index (r=0.388, p=0.009 and r=0.425, p=0.004, respectively). However, there was no significant association of functional class, ejection fraction, mitral flow, or annular velocities with the extent of LGE.

CONCLUSIONS

In HCM patients, the extent of LGE positively correlated with the left atrial volume index, a surrogate marker of chronic diastolic burden. These findings suggest that myocardial scarring may be a pathologic substrate for chronic diastolic dysfunction in patients with HCM.

Noninvasive detection of fibrosis applying contrast-enhanced cardiac magnetic resonance in different forms of left ventricular hypertrophy relation to remodeling

OBJECTIVES

We aimed to evaluate the incidence and patterns of late gadolinium enhancement (LGE) in different forms of left ventricular hypertrophy (LVH) and to determine their relation to severity of left ventricular (LV) remodeling.

BACKGROUND

Left ventricular hypertrophy is an independent predictor of cardiac mortality. The relationship between LVH and myocardial fibrosis as defined by LGE cardiovascular magnetic resonance (CMR) is not well understood.

METHODS

A total of 440 patients with aortic stenosis (AS), arterial hypertension (AH), or hypertrophic cardiomyopathy (HCM) fulfilling echo criteria of LVH underwent CMR with assessment of LV size, weight, function, and LGE. Patients with increased left ventricular mass index (LVMI) resulting in global LVH in CMR were included in the study.

RESULTS

Criteria were fulfilled by 83 patients (56 men, age 57 +/- 14 years; AS, n = 21; AH, n = 26; HCM, n = 36). Late gadolinium enhancement was present in all forms of LVH (AS: 62%, AH: 50%; HCM: 72%, p = NS) and was correlated with LVMI (r = 0.237, p = 0.045). There was no significant relationship between morphological obstruction and LGE. The AS subjects with LGE showed higher LV end-diastolic volumes than those without (1.0 +/- 0.2 ml/cm vs. 0.8 +/- 0.2 ml/cm, p < 0.015). Typical patterns of LGE were observed in HCM but not in AS and AH.

CONCLUSIONS

Fibrosis as detected by CMR is a frequent feature of LVH, regardless of its cause, and depends on the severity of LV remodeling. As LGE emerges as a useful tool for risk stratification also in nonischemic heart diseases, our findings have the potential to individualize treatment strategies.

Cardiac magnetic resonance for risk stratification: the sudden death risk portrayed

Risk stratification of patients with structural heart disease remains problematic. While patients with low ejection fractions have been shown to be at significant risk for sudden cardiac death, a risk that can be decreased by ICD implantation, the sensitivity and specificity of ejection fraction for predicting sudden death are sub-optimal. Contrast enhanced magnetic resonance imaging (CMRI) has been shown to carefully delineate the extent and morphology of myocardial scar. Recent studies have suggested that the extent of myocardial scar and potentially its heterogeneity can help risk stratify patient with coronary artery disease. Ongoing clinical studies will help determine the utility of incorporating CMRI into a risk prediction algorithm.

Delayed enhancement cardiac magnetic resonance imaging reveals typical patterns of myocardial injury in patients with various forms of non-ischemic heart disease

BACKGROUND

Late gadolinium-hyperenhancement (LHE) on cardiac magnetic resonance imaging (CMR) has been linked to cardiovascular risk in ischemic and non-ischemic heart disease. We aimed to systematically categorize LHE-patterns in a variety of non-ischemic heart diseases (NIHD) and to explore their relationship with left ventricular (LV) function.

METHODS

In a retrospective database search, 156 patients with NIHD who exhibited LHE on CMR were identified. All images were re-analyzed stepwise. LHE was correlated to LV functional parameters. Cardiac magnetic resonance (CMR) was conducted on 1.5 T scanners.

RESULTS

Typically, LHE spared the subendocardium. Consistent LHE-patterns were observed in myocarditis, hypertrophic and dilated cardiomyopathy and systemic vasculitis. No conclusive LHE-patterns were observed in patients with aortic stenosis, arterial hypertension, lupus erythematosus, sarcoidosis, ventricular arrhythmia and in a mixed subgroup of rare NIHDs. There was no significant relationship between LHE and ejection fraction. There was no correlation between enddiastolic volume and LHE in either myocarditis (P = 0.13) or dilated cardiomyopathy (P = 0.62). LHE was unrelated to LV-mass in aortic stenosis (P = 0.13) and hypertrophic cardiomyopathy (P = 0.38).

CONCLUSIONS

Distinct LHE patterns exist in various NIHDs and their visualization may ultimately aid diagnosis. Unlike in ischemic heart disease, the structure-function relationship does not appear to be strong.

Advances in clinical applications of cardiovascular magnetic resonance imaging

Cardiovascular magnetic resonance (CMR) is an evolving technology with growing indications within the clinical cardiology setting. This review article summarises the current clinical applications of CMR. The focus is on the use of CMR in the diagnosis of coronary artery disease with summaries of validation literature in CMR viability, myocardial perfusion, and dobutamine CMR. Practical uses of CMR in non-coronary diseases are also discussed.

Assessment of late gadolinium enhancement in nonischemic cardiomyopathy: comparison of a fast Phase-Sensitive Inversion Recovery Sequence (PSIR) and a conventional segmented 2D gradient echo recall (GRE) sequence--preliminary findings

BACKGROUND

Reliable detection of myocardial scarring in nonischemic cardiomyopathy is time-consuming using techniques that require determination of optimal inversion time. Therefore we evaluated an inversion-time-insensitive approach using a fast phase-sensitive inversion recovery (PSIR) sequence to detect and quantify late gadolinium enhancement (LGE).

PATIENTS AND METHODS

Twenty patients (mean age 40 years, 9 females) with nonischemic cardiomyopathy and evidence of LGE were evaluated. After administration of 0.2 mmol/kg gadolinium diethylene triamine pentaacetic acid, a segmented 2D inversion recovery turbo fast low-angle shot gradient echo recall (GRE) sequence [echo time (TE) 4.3 milliseconds, repetition time (TR) 750 milliseconds, alpha 30 degrees , voxel size 1.7 x 1.3 x 8-10 mm] was obtained and served as the standard of reference. Second, a fast multislice single-shot 2D PSIR sequence (TE 1.1 millisecond, TR 700 milliseconds, alpha 40 degrees , voxel size 2.5 x 1.7 x 8-10 mm) was acquired in the same slice positions. The PSIR(IR) images were used to analyze LGE. Altogether 53 short-axis slices with LGE were evaluated. Contrast-to-noise ratio and area of LGE were calculated and compared by 2 experienced readers. Image quality and confidence level for identification of LGE were rated on 5-point scales. Interobserver variability was evaluated in 10 patients.

RESULTS

All images were interpretable. Imaging time was reduced from 385 +/- 127 seconds to 20 +/- 3 seconds (P < 0.001). Contrast-to-noise ratio was 8.29 for PSIRmag and 12.07 for the conventional GRE images (P < 0.001). The mean area of LGE was 1.01 +/- 0.62 cm(2) for the GRE sequence and 1.10 +/- 0.62 cm(2) for PSIR(IR) (P = NS). The general linear model showed no interaction between the results and no significant difference of the mean (r = 0.09, mean difference 0.09 cm(2)). The overall interobserver variability of PSIR(IR) and GRE was excellent, with Pearson's correlation coefficients of r = 0.96 for PSIR(IR) and r = 0.98 for GRE. PSIR(IR) and conventional GRE were comparable in terms of image quality and confidence level (image quality: 1.6 +/- 0.67 vs. 1.5 +/- 0.93, P = NS; confidence level: 1.4 +/- 0.84 vs. 1.3 +/- 0.5; P = NS).

CONCLUSIONS

Fast PSIR sequences enable accurate detection and quantification of LGE in nonischemic cardiomyopathies. The examination time can be significantly shortened using the single-shot approach of the PSIR technique.