Cardiovascular Research in Friedreich Ataxia: Unmet Needs and Opportunities

Friedreich Ataxia (FRDA) is an autosomal recessive disease in which a mitochondrial protein, frataxin, is severely decreased in its expression. In addition to progressive ataxia, patients with FRDA often develop a cardiomyopathy that can be hypertrophic. This cardiomyopathy is unlike the sarcomeric hypertrophic cardiomyopathies in that the hypertrophy is associated with massive mitochondrial proliferation within the cardiomyocyte rather than contractile protein overexpression. This is associated with atrial arrhythmias, apoptosis, and fibrosis over time, and patients often develop heart failure leading to premature death. The differences between this mitochondrial cardiomyopathy and the more common contractile protein hypertrophic cardiomyopathies can be a source of misunderstanding in the management of these patients. Although imaging studies have revealed much about the structure and function of the heart in this disease, we still lack an understanding of many important clinical and fundamental molecular events that determine outcome of the heart in FRDA. This review will describe the current basic and clinical understanding of the FRDA heart, and most importantly, identify major gaps in our knowledge that represent new directions and opportunities for research.

Increased prevalence of left ventricular diastolic dysfunction in adults with repaired coarctation of aorta

Background

Left ventricular (LV) pressure overload and coronary artery disease are common in patients with coarctation of aorta (COA), and they are risk factors for LV diastolic dysfunction. Patients with COA may have aortic vasculopathy that can result in LV pressure overload even in the absence of hemodynamically significant COA. We therefore hypothesized that patients with mild COA (without hemodynamically significant COA) will have more LV diastolic dysfunction compared to controls.

Methods

Adult patients with mild COA (Doppler peak velocity < 2.5 m/s) were matched 1:1 to patients without structural heart disease using propensity score method based on age, sex, body mass index, hypertension and blood pressure. The objective was to compare LV diastolic dysfunction (defined as E/e′ > 2 standard deviations above age-specific normative values) between adults with repaired COA and controls.

Results

Of 204 COA and 204 control patients (age 35 ± 12 years), patients with COA had higher septal and lateral E/e′ ratio (12 ± 4 vs 9 ± 4, p = 0.009) and (10 ± 3 vs 7 ± 3, p < 0.001), respectively. Compared to controls, the prevalence of LV diastolic dysfunction was higher in patients with COA for every age group: <40 years (63% vs 13%, p < 0.001); 41–60 years (87% vs 33%, p < 0.001); age > 60 years (82% vs 56%, p = 0.076). Left ventricular mass index (LVMI) was the strongest determinant of E/e′ (β = 2.71 per 10 g/m², standard error = 1.25, p < 0.001).

Conclusion

LV diastolic dysfunction was common in patients with COA, and the association with LVMI suggests that patients with COA may have ongoing LV pressure overload in the absence of hemodynamically significant re-coarctation.

Association of Cardiac Structure and Function With Neurocognition in Hispanics/Latinos: The Echocardiographic Study of Latinos

Objective

To study the associations of comprehensive measures of cardiac structure and function with multidimensional neurocognitive measures.

Patients and Methods

The Echocardiographic Study of Latinos is a population-based cohort of Hispanic/Latino adults older than 45 years enrolled from October 1, 2011, through June 30, 2014. Neurocognitive measures included Word Fluency (WF), Brief-Spanish English Verbal Learning Test (B-SEVLT), and Digit Symbol Substitution Test. The B-SEVLT included B-SEVLT-recall and B-SEVLT-sum. Echocardiographic measures included cardiac structure, systolic and diastolic function, and myocardial strain. Multivariable regression models were fit using survey statistics and sampling probabilities.

Results

A total of 1794 participants (mean age, 56±0.5 years; 56% women) were included in the analysis. In the adjusted model, higher left ventricular mass index was associated with lower B-SEVLT-sum and Digit Symbol Substitution Test scores. Left ventricular systolic dysfunction was associated with lower WF scores. Abnormal left ventricular geometry was associated with lower B-SEVLT-sum scores. Higher relative wall thickness was associated with B-SEVLT-recall and B-SEVLT-sum scores. Mitral annular relaxation velocities were associated with lower B-SEVLT-recall, B-SEVLT-sum, and WF scores. Higher mitral inflow to annular early diastolic velocity ratio was associated with lower B-SEVLT-recall and B-SEVLT-sum scores. Diastolic dysfunction was associated with lower B-SEVLT-sum scores. Finally, lower global longitudinal strain was associated with lower WF scores.

Conclusion

Alterations in cardiac structure, systolic and diastolic function, and myocardial strain were associated with worse neurocognitive function. Further study is needed to determine the mechanisms (ie, impairment of cerebral flow and silent brain infarctions) mediating these heart-brain associations.

Long-term galsulfase enzyme replacement therapy in Taiwanese mucopolysaccharidosis VI patients: A case series

BACKGROUND

Information regarding the long-term outcome of enzyme replacement therapy (ERT) with recombinant human N-acetylgalactosamine 4-sulfatase (rhASB, galsulfase, Naglazyme®, BioMarin Pharmaceutical Inc.) for Taiwanese patients with mucopolysaccharidosis (MPS) VI is limited.

METHODS

Nine Taiwanese patients with MPS VI (4 males and 5 females; age range, 1.4 to 21.1 years) treated with weekly intravenous infusions of galsulfase (1.0 mg/kg) in 5 medical centers in Taiwan were reviewed. A set of biochemical and clinical assessments were evaluated annually.

RESULTS

After 6.2 to 11.2 years of galsulfase treatment, 6 patients experienced improvement over baseline in the 6-minute walk test by a mean of 150 m (59% change over time), and 3 patients also increased the 3-minute stair climb test by a mean of 60 steps (46%). In a manual dexterity test, 3 patients decreased the time required to pick up 10 coins and put the coins into a cup by 15 s (33%). Shoulder range of motion in all 9 patients improved, and Joint Pain and Stiffness Questionnaire scores improved by 0.42 points (21%). Four patients showed improved pulmonary function. Five patients had positive effects on cardiac-wall diameters. Four patients had improved cardiac diastolic function. Liver and spleen sizes as measured by abdominal ultrasonography remained the same or decreased in all 9 patients. However, the severity degree of valvular stenosis or regurgitation did not show improvement despite ERT. A mean overall 69% decrease in urinary glycosaminoglycan (GAG) excretion indicated a satisfactory biomarker response.

CONCLUSIONS

Long-term ERT was beneficial and safe for Taiwanese patients with MPS VI. This treatment reduced urinary GAG and had positive effects on a wide range of clinical functional assessments including endurance, mobility, joint function, pulmonary function, liver and spleen size, cardiac hypertrophy and diastolic dysfunction.

Effects of the combinations of amlodipine/valsartan versus losartan/hydrochlorothiazide on left ventricular hypertrophy as determined with magnetic resonance imaging in patients with hypertension

Background

Left ventricular hypertrophy (LVH), a marker of cardiac end-organ damage, is frequently found in patients with arterial hypertension and is associated with cardiovascular and cerebrovascular morbidity and mortality. Therefore, LVH regression is an important treatment goal. For amlodipine plus valsartan (A/V) no specific study on LVH has been reported to date.

Methods

Prospective, open-label, randomized parallel-group study. Patients with essential hypertension and LVH were randomized to 52-week treatment with A/V 10/160 mg (n = 43) or the active comparator losartan/HCT 100/25 mg (L/H, n = 47). Add-on medication was allowed in case of inadequate blood pressure control. LV parameters were measured by cardiovascular magnetic resonance imaging (MRI), and adjudicated in a blinded manner. Study identifiers were NCT00446563 and EudraCT 2006-001977-17.

Results

In addition to the study treatment, 35% of patients in the A/V group and 49% in the L/H group received additional antihypertensive medication. Compared to baseline, both treatments reduced measures of LVH significantly after 52 weeks (e.g. LV mass index in the A/V group from 64.7 g/m² by −3.5 g/m², in the L/H group from 69.1 g/m² by −4.4 g/m², p < 0.01 for both). LV ejection fraction and LV volumes were not significantly changed by any regimen. A/V and L/H treatments were well tolerated.

Conclusions

Both regimen were effective in reducing LV mass compared to baseline and were well tolerated.