Quantitative three-dimensional myocardial perfusion cardiovascular magnetic resonance with accurate two-dimensional arterial input function assessment.

BACKGROUND: Quantification of myocardial perfusion from first-pass cardiovascular magnetic resonance (CMR) images at high contrast agent (CA) dose requires separate acquisition of blood pool and myocardial tissue enhancement. In this study, a dual-sequence approach interleaving 2D imaging of the arterial input function with high-resolution 3D imaging for myocardial perfusion assessment is presented and validated for low and high CA dose. METHODS: A dual-sequence approach interleaving 2D imaging of the aortic root and 3D imaging of the whole left ventricle using highly accelerated k-t PCA was implemented. Rest perfusion imaging was performed in ten healthy volunteers after administration of a Gadolinium-based CA at low (0.025 mmol/kg b.w.) and high dose (0.1 mmol/kg b.w.). Arterial input functions extracted from the 2D and 3D images were analysed for both doses. Myocardial contrast-to-noise ratios (CNR) were compared across volunteers and doses. Variations of myocardial perfusion estimates between volunteers and across myocardial territories were studied. RESULTS: High CA dose imaging resulted in strong non-linearity of the arterial input function in the 3D images at peak CA concentration, which was avoided when the input function was derived from the 2D images. Myocardial CNR was significantly increased at high dose compared to low dose, with a 2.6-fold mean CNR gain. Most robust myocardial blood flow estimation was achieved using the arterial input function extracted from the 2D image at high CA dose. In this case, myocardial blood flow estimates varied by 24% between volunteers and by 20% between myocardial territories when analysed on a per-volunteer basis. CONCLUSION: Interleaving 2D imaging for arterial input function assessment enables robust quantitative 3D myocardial perfusion imaging at high CA dose.

Patients with Fabry disease after enzyme replacement therapy dose reduction versus treatment switch.

Because of the shortage of agalsidase-beta in 2009, many patients with Fabry disease were treated with lower doses or were switched to agalsidase-alfa. This observational study assessed end-organ damage and clinical symptoms during dose reduction or switch to agalsidase-alfa. A total of 105 adult patients with Fabry disease who had received agalsidase-beta (1.0 mg/kg body weight) for ≥1 year were nonrandomly assigned to continue this treatment regimen (regular-dose group, n=38), receive a reduced dose of 0.3-0.5 mg/kg (dose-reduction group, n=29), or switch to 0.2 mg/kg agalsidase-alfa (switch group) and were followed prospectively for 1 year. We assessed clinical events (death, myocardial infarction, severe arrhythmia, stroke, progression to ESRD); changes in cardiac, renal, and neurologic function; and Fabry-related symptoms (neuropathic pain, hypohidrosis, diarrhea, and disease severity scores). Organ function and Fabry-related symptoms remained stable in the regular-dose group. In contrast, estimated GFR decreased by about 3 ml/min per 1.73 m(2) (P=0.01) in the dose-reduction group, and the median albumin-to-creatinine ratio increased from 114 (0-606) mg/g to 216 (0-2062) mg/g (P=0.03) in the switch group. Furthermore, mean Mainz Severity Score Index scores and frequencies of pain attacks, chronic pain, gastrointestinal pain, and diarrhea increased significantly in the dose-reduction and switch groups. In conclusion, patients receiving regular agalsidase-beta dose had a stable disease course, but dose reduction led to worsening of renal function and symptoms. Switching to agalsidase-alfa is safe, but microalbuminuria may progress and Fabry-related symptoms may deteriorate.

Potential role of vitamin D deficiency on Fabry cardiomyopathy.

Patients with Fabry disease frequently develop left ventricular (LV) hypertrophy and renal fibrosis. Due to heat intolerance and an inability to sweat, patients tend to avoid exposure to sunlight. We hypothesized that subsequent vitamin D deficiency may contribute to Fabry cardiomyopathy. This study investigated the vitamin D status and its association with LV mass and adverse clinical symptoms in patients with Fabry disease. 25-hydroxyvitamin D (25[OH]D) was measured in 111 patients who were genetically proven to have Fabry disease. LV mass and cardiomyopathy were assessed by magnetic resonance imaging and echocardiography. In cross-sectional analyses, associations with adverse clinical outcomes were determined by linear and binary logistic regression analyses, respectively, and were adjusted for age, sex, BMI and season. Patients had a mean age of 40 ± 13 years (42% males), and a mean 25(OH)D of 23.5 ± 11.4 ng/ml. Those with overt vitamin D deficiency (25[OH]D ≤ 15 ng/ml) had an adjusted six fold higher risk of cardiomyopathy, compared to those with sufficient 25(OH)D levels >30 ng/ml (p = 0.04). The mean LV mass was distinctively different with 170 ± 75 g in deficient, 154 ± 60 g in moderately deficient and 128 ± 58 g in vitamin D sufficient patients (p = 0.01). With increasing severity of vitamin D deficiency, the median levels of proteinuria increased, as well as the prevalences of depression, edema, cornea verticillata and the need for medical pain therapy. In conclusion, vitamin D deficiency was strongly associated with cardiomyopathy and adverse clinical symptoms in patients with Fabry disease. Whether vitamin D supplementation improves complications of Fabry disease, requires a randomized controlled trial.

Two-dimensional speckle tracking as a non-invasive tool for identification of myocardial fibrosis in Fabry disease.

AIMS: This cross-sectional study aimed to analyse myocardial deformation in patients with Fabry disease (FD) in order to evaluate speckle tracking as a method for non-invasive determination of myocardial fibrosis. Myocardial fibrosis is common in Fabry cardiomyopathy and is associated with disease progression and severe prognosis. METHODS AND RESULTS: In 101 consecutive Fabry patients (39.8 ± 12.9 years; 42 males), the quantitative measurement of myocardial fibrosis with magnetic resonance imaging was compared with regional myocardial deformation assessed by speckle-tracking imaging. Patients were analysed in relation to per cent of late-enhancement (LE)-positive areas of left-ventricular (LV) mass. Fifty-two patients (51%) displayed LE with a mean volume of 1.2 ± 1.8% of total LV mass. Predominantly basal lateral and posterior segments were affected. Patients with LE had lower global systolic longitudinal strain than those without (LE -14.8 ± 3.5% and -18.9 ± 2.1%, respectively; P < 0.001). Loss of global deformation, quantified by speckle tracking, was predominantly caused by basal posterior (P = 0.049) and lateral (P = 0.005) segments and global systolic strain correlated with the amount of LE (r = 0.543; P < 0.001). Patients with severe LE (>2%, n = 22) showed the lowest deformation values (-5.9 ± 8.4%) in basal postero-lateral segments when compared with those with mild (<2%; n = 30, -7.1 ± 7.5%) or no LE (n = 49, -16.3 ± 3.3%). These changes were accompanied by thinning of the posterior wall and a decrease in diastolic function, whereas ejection fraction and LV end-diastolic diameter were not different. Receiver operating characteristic analysis revealed that the systolic strain of basal postero-lateral segments was the most powerful predictor to distinguish between patients with and without LE (sensitivity = 90%; specificity = 97%, area under the curve = 0.913; P < 0.001). CONCLUSIONS: Late enhancement is associated with lower longitudinal strain in the fibrotic wall segments. Speckle tracking can be used as a tool for the indirect evaluation of LE in FD.

Cardiomyopathy of Friedreich ataxia.

Friedreich's ataxia is a rare hereditary, predominantly neurologically defined multisystem disorder of mitochondrial function. Although the gene defect has been identified, the precise pathophysiology of the deficient mitochondrial protein, frataxin, is unknown. Besides the characteristic features of spinocerebellar ataxia the heart may also be affected, and patients may experience a hypertrophic cardiomyopathy eventually progressing toward heart failure and death. So far, research focused on the neurological aspects and little attention has been paid to better characterize and understand the cardiac involvement in Friedreich's ataxia. For that, a better understanding of longitudinal progression, cardiac complications and long-term cardiac outcome is warranted. In addition, the clinician should be familiar with the therapeutic option in Friedreich cardiomyopathy. This review discusses important clinical and diagnostic features of the cardiomyopathy in Friedreich's ataxia and potential therapeutic developments.

The Fabry cardiomyopathy: models for the cardiologist.

Fabry disease is an X-linked lysosomal storage disorder caused by α-galactosidase A deficiency. Intracellular accumulation of globotriaosylceramide starts in utero and progressively develops in various tissues and organs. Cardiac involvement is frequent, and its presentation as concentric nonobstructive left ventricular hypertrophy serves as a model for other hypertrophic cardiomyopathies. This review describes the Fabry cardiomyopathy, its treatment, and multidisciplinary patient care models. These models will help clinicians in diagnosing, assessing, and treating patients with Fabry disease. As the models can be extrapolated to other diseases, they might contribute to more optimal clinical management of patients with other cardiac disorders.

Analysis of left ventricular mass in untreated men and in men treated with agalsidase-ß: data from the Fabry Registry.

PURPOSE: The aim of this study was to evaluate the progression of left ventricular hypertrophy in untreated men with Fabry disease and to assess the effects of agalsidase-ß (recombinant human α-galactosidase A) on left ventricular hypertrophy. METHODS: Longitudinal Fabry Registry data were analyzed from 115 men treated with agalsidase-ß (1 mg/kg/2 weeks) and 48 untreated men. Measurements included baseline left-ventricular mass and at least one additional left-ventricular mass assessment over ≥ 2 years. Patients were grouped into quartiles, based on left-ventricular mass slopes. Multivariate logistic regression analyses identified factors associated with left ventricular hypertrophy progression. RESULTS: For men in whom treatment was initiated at the age of 18 to <30 years, mean left ventricular mass slope was -3.6 g/year (n = 31) compared with +9.5 g/year in untreated men of that age (n = 15) (P < 0.0001). Untreated men had a 3.4-fold higher risk of having faster increases in left-ventricular mass compared with treated men (odds ratio: 3.43; 95% confidence interval: 1.05-11.22; P = 0.0415). A baseline age of ≥ 40 years was also associated with left--ventricular hypertrophy progression (odds ratio: 5.03; 95% confidence interval: 1.03-24.49; P = 0.0457) compared with men younger than 30 years. CONCLUSION: Agalsidase-ß treatment for ≥2 years may improve or stabilize left-ventricular mass in men with Fabry disease. Further investigations may determine whether early intervention and stabilization of LVM are correlated with clinical outcomes.

Fluctuations of 1/f noise and the low-frequency cutoff paradox.

Recent experiments on blinking quantum dots, weak turbulence in liquid crystals, and nanoelectrodes reveal the fundamental connection between 1/f noise and power law intermittency. The nonstationarity of the process implies that the power spectrum is random--a manifestation of weak ergodicity breaking. Here, we obtain the universal distribution of the power spectrum, which can be used to identify intermittency as the source of the noise. We solve in this case an outstanding paradox on the nonintegrability of 1/f noise and the violation of Parseval's theorem. We explain why there is no physical low-frequency cutoff and therefore why it cannot be found in experiments.

Cross-sectional baseline analysis of electrocardiography in a large cohort of patients with untreated Fabry disease.

BACKGROUND: Morphology and function of Fabry cardiomyopathy has been previously studied by echocardiography and cardiac magnetic resonance (CMR). However, the value of electrocardiography (ECG) in relation to these two techniques remains largely unknown. METHODS: One hundred fifty genetically confirmed Fabry patients were investigated using a comprehensive clinical workup comprising 12-lead ECG, echocardiography, and CMR. RESULTS: ECG parameters at rest [PR, P wave, QT, QTc, QT dispersion and time interval from the peak to the end of the T wave (Tpeak to Tend)] were normal in the entire cohort and did not distinguish between males and females or stages of cardiomyopathy. A significant positive correlation was found between left ventricular (LV) mass on CMR and both the QRS duration and the LV Sokolow index, with the highest values in male patients with an advanced cardiomyopathy stage. No prediction of late enhancement on CMR (a sign for replacement fibrosis) was possible by a single ECG parameter. However, the absence of ST or T alterations (in 37 of 38 patients) specifically excluded late enhancement on CMR. CONCLUSION: Our data in a large cohort of Fabry patients, including all cardiomyopathy stages, show, in contrast to former assumptions, that ECG parameters are not suitable to stage Fabry cardiomoypathy. Most ECG parameters were normal in the complete cohort. However, the absence of ST or T alterations seems to almost exclude late enhancement on CMR in these patients.

Interdisciplinary approach towards female patients with Fabry disease.

BACKGROUND: Fabry disease (FD) is a rare X-linked lysosomal storage disorder leading to an accumulation of globotriaosylceramides in the lysosomes of various organs. DESIGN: Being X-chromosomal-linked, most studies in the past have focused on involvement in male patients. However, it has been elucidated recently that female patients can present typical organ involvement and thus need to be treated, respectively. CONCLUSIONS: This review wants to give a systematical overview of the typical organ involvement in female patients with FD. Moreover, therapy recommendations especially for female patients are discussed.

Right ventricular involvement in left ventricular non-compaction cardiomyopathy.

BACKGROUND: Left ventricular non-compaction cardiomyopathy (LVNC) features extensive trabeculations. Involvement of the right ventricle (RV) has been reported; however, distinction from normal RV trabeculation is difficult. This study aimed at assessing RV morphology and function in LVNC by cardiac magnetic resonance (CMR) and transthoracic echocardiography (TTE). METHODS: Dimensional and functional parameters were assessed according to guidelines. Novel CMR parameters were RV end-diastolic (ED) trabeculated area, RV ED trabeculated volume, and RV ED non-compacted to compacted (NC/N) ratio in short axis (SAX) as well as in four-chamber view (4CH). RESULTS: Twenty patients with LVNC and 20 controls were included. RV size and function were comparable in LVNC and controls and exhibited a good correlation between TTE and CMR. Although RV trabeculated area, RV trabeculated volume, and RV ED NC/C ratio in SAX as well as in 4CH were larger in LVNC, there was a major overlap with values in controls. RV ED NC/C ratio in SAX correlated with LV ED NC/C ratio (not in 4CH). Quantitative assessment of RV non-compaction was not feasible in TTE. CONCLUSIONS: Right ventricle size and function in LVNC can be measured by CMR and TTE, while RV trabeculation can only be quantified by CMR. RV myocardium displays more trabeculations in LVNC; however, overlap with normal individuals is extensive, not allowing separation of patients with LVNC from controls.

Long-term effects of enzyme replacement therapy on fabry cardiomyopathy: evidence for a better outcome with early treatment.

BACKGROUND: Enzyme replacement therapy with recombinant alpha-galactosidase A reduces left ventricular hypertrophy and improves regional myocardial function in patients with Fabry disease during short-term treatment. Whether enzyme replacement therapy is effective in all stages of Fabry cardiomyopathy during long-term follow-up is unknown. METHODS AND RESULTS: We studied 32 Fabry patients over a period of 3 years regarding disease progression and clinical outcome under enzyme replacement therapy. Regional myocardial fibrosis was assessed by magnetic resonance imaging late-enhancement technique. Echocardiographic myocardial mass was calculated with the Devereux formula, and myocardial function was quantified by ultrasonic strain-rate imaging. In addition, exercise capacity was measured by bicycle stress test. All measurements were repeated at yearly intervals. At baseline, 9 patients demonstrated at least 2 fibrotic left ventricular segments (severe myocardial fibrosis), 11 had 1 left ventricular segment affected (mild fibrosis), and 12 were without fibrosis. In patients without fibrosis, enzyme replacement therapy resulted in a significant reduction in left ventricular mass (238+/-42 g at baseline, 202+/-46 g at 3 years; P for trend <0.001), an improvement in myocardial function (systolic radial strain rate, 2.3+/-0.4 and 2.9+/-0.6 seconds(-1), respectively; P for trend=0.045), and a higher exercise capacity obtained by bicycle stress exercise (106+/-14 and 122+/-26 W, respectively; P for trend=0.014). In contrast, patients with mild or severe fibrosis showed a minor reduction in left ventricular hypertrophy and no improvement in myocardial function or exercise capacity. CONCLUSIONS: These data suggest that treatment of Fabry cardiomyopathy with recombinant alpha-galactosidase A should best be started before myocardial fibrosis has developed to achieve long-term improvement in myocardial morphology and function and exercise capacity.

Impact of myocardial fibrosis in patients with symptomatic severe aortic stenosis.

BACKGROUND: In this prospective follow-up study, the effect of myocardial fibrosis on myocardial performance in symptomatic severe aortic stenosis was investigated, and the impact of fibrosis on clinical outcome after aortic valve replacement (AVR) was estimated. METHODS AND RESULTS: Fifty-eight consecutive patients with isolated symptomatic severe aortic stenosis underwent extensive baseline characterization before AVR. Standard and tissue Doppler echocardiography and cardiac magnetic resonance imaging (late-enhancement imaging for replacement fibrosis) were performed at baseline and 9 months after AVR. Endomyocardial biopsies were obtained intraoperatively to determine the degree of myocardial fibrosis. Patients were analyzed according to the severity of interstitial fibrosis in cardiac biopsies (severe, n=21; mild, n=15; none, n=22). The extent of histologically determined cardiac fibrosis at baseline correlated closely with New York Heart Association functional class and markers of longitudinal systolic function (all P<0.001) but not global ejection fraction or aortic valve area. Nine months after AVR, the degree of late enhancement remained unchanged, implying that AVR failed to reduce the degree of replacement fibrosis. Patients with no fibrosis experienced a marked improvement in New York Heart Association class from 2.8+/-0.4 to 1.4+/-0.5 (P<0.001). Only parameters of longitudinal systolic function predicted this functional improvement. Four patients with severe fibrosis died during follow-up, but no patient from the other groups died. CONCLUSIONS: Myocardial fibrosis is an important morphological substrate of postoperative clinical outcome in patients with severe aortic stenosis and was not reversible after AVR over the 9 months of follow-up examined in this study. Because markers of longitudinal systolic function appear to indicate sensitively both the severity of myocardial fibrosis and the clinical outcome, they may prove valuable for preoperative risk assessment in patients with aortic stenosis.

Diagnostic criteria for left ventricular non-compaction in cardiac computed tomography.

PURPOSE: Left ventricular non-compaction (LVNC) is characterized by a 2-layered myocardium composed of a noncompacted (NC) and a compacted (C) layer. The echocardiographic NC:C ratio is difficult to assess in many patients. The aim of the study was to assess the value of cardiac computed tomography (CCT) for the diagnosis of LVNC. METHODS: In this prospective controlled study, segmental analysis of transthoracic echocardiography (TTE) and prospective ECG-triggered CCT was performed in 17 patients with LVNC and 19 healthy controls. In TTE maximal NC and C thickness was measured at enddiastole and endsystole in the segment with most prominent trabeculation in short axis views. In CCT, maximal segmental NC and C thickness was measured during diastole, and NC:C ratio was determined. Spearman's correlation coefficient and receiver operating characteristic curves were calculated. RESULTS: The median [IQR] radiation dose was 1.3[1.2-1.5]mSv. The CCT thickness of the C layer was significantly lower in patients with LVNC as compared to controls in the inferolateral, midventricular, lateral-, inferior-, and septal-apical segments. The CCT NC:C ratio differed significantly between LVNC and controls in the inferior-midventricular and all the apical segments. NC:C ratio correlated significantly between TTE and CCT at enddiastole (σ = 0.8) and endsystole (σ = 0.9). Using a CCT NC:C ratio ≥1.8, all LVNC patients could be identified. CONCLUSION: LVNC can be diagnosed with ECG-triggered low-dose CCT and discriminated from normal individuals using a NC:C ratio of ≥1.8 in diastole. There is a very good correlation of NC:C ratio in TTE and CCT.

Joint probability distributions and multipoint correlations of the continuous-time random walk.

We present an efficient method to determine the Fourier-Laplace transform of the joint n-point probability distribution of a continuous-time random walk for arbitrary finite n. Additionally, we devise a recursive procedure with which it is possible to calculate the Laplace transforms of the multipoint correlation functions without having to determine the joint probability distributions first. The methods are used on several examples with both independent and dependent distributions for the waiting time and the spatial step size.

Usage of the Mori-Zwanzig method in time series analysis.

The use of memory kernels stemming from a Mori-Zwanzig approach to time series analysis is discussed. We show that despite its success in determining properties from an analytical model, the kernel itself is not easily interpreted. We consider a recently introduced discretization of the kernel and show that its properties can be quite different from its continuous counterpart. We provide a rigorous analysis of the discrete case and show for several analytically calculated memory kernels of simple time series processes that their features are not readily detectable in the kernel. We show furthermore that practical relevant Mori-Zwanzig models with a finite kernel form a true subclass of the autoregressive moving average (ARMA) models. The fact that this approach already veils the properties of these simple time series gives rise to severe doubts about its applicability in more complex situations.

Right ventricular outflow tract dimensions in arrhythmogenic right ventricular cardiomyopathy/dysplasia-a multicentre study comparing echocardiography and cardiovascular magnetic resonance.

Aims: Right ventricular outflow tract (RVOT) dilation is one of the echocardiographic criteria in the 2010 revised Task Force Criteria (TFC) of arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D). However, studies comparing cardiac magnetic resonance (CMR) and transthoracic echocardiography (TTE) suggest a lower diagnostic accuracy of TTE due to its operator dependence and limited reproducibility. The goal of this study was to compare the 2010 TFC measures of RVOT dilation with three alternative measures for improving the echocardiographic assessment of RVOT in patients with ARVC/D. Methods and results: In this multicentre study, CMR and TTE were performed in 38 patients with a definite, borderline, or possible ARVC/D diagnosis and in 10 healthy controls. Besides the echocardiographic RVOT measurements listed by the 2010 TFC, we assessed three additional end-diastolic RVOT diameters. These included the RVOT diameter defined by the parasternal long axis M-mode of the aortic sinus portion (RVOT3), that defined by the parasternal long axis M-mode of the left ventricle (RVOT4), and that obtained by the parasternal short axis view of the distal RVOT proximal to the pulmonary valve (RVOT5). RVOT4 provided the best correlation between CMR and TTE (r = 0.92, [95% confidence interval (CI): 0.84-0.96; P < 0.0001]) and enhanced diagnostic accuracy for diagnosing ARVC/D (area under the curve 0.92 [95% CI, 0.78-0.98]). Conclusion: Among all RVOT diameters examined, that defined by the parasternal long axis M-mode of the left ventricle (RVOT4) provides the best agreement between CMR and TTE and exhibits the best diagnostic accuracy for ARVC/D. This novel RVOT4 measurement carries the potential for improving the echocardiographic diagnosis of ARVC/D.