Left ventricular assist device as bridge to liver transplantation in a patient with propionic acidemia and cardiogenic shock

Cardiac Involvement in Classical Organic Acidurias: Clinical Profile and Outcome in a Pediatric Cohort

BACKGROUND

Cardiac involvement is reported in a significant proportion of patients with classical organic acidurias (OAs), contributing to disability and premature death. Different cardiac phenotypes have been described, among which dilated cardiomyopathy (DCM) is predominant. Despite recent progress in diagnosis and treatment, the natural history of patients with OAs remains unresolved, specifically with regard to the impact of cardiac complications. We therefore performed a retrospective study to address this issue at our Referral Center for Pediatric Inherited Errors of Metabolism.

METHODS

Sixty patients with OAs (propionic (PA), methylmalonic (MMA) and isovaleric acidemias and maple syrup urine disease) diagnosed from 2000 to 2022 were systematically assessed at baseline and at follow-up.

RESULTS

Cardiac anomalies were found in 23/60 OA patients, all with PA or MMA, represented by DCM (17/23 patients) and/or acquired long QT syndrome (3/23 patients). The presence of DCM was associated with the worst prognosis. The rate of occurrence of major adverse cardiac events (MACEs) at 5 years was 55% in PA with cardiomyopathy; 35% in MMA with cardiomyopathy; and 23% in MMA without cardiomyopathy. Liver transplantation was performed in seven patients (12%), all with PA or MMA, due to worsening cardiac impairment, and led to the stabilization of metabolic status and cardiac function.

CONCLUSIONS

Cardiac involvement was documented in about one third of children diagnosed with classical OAs, confined to PA and MMA, and was often associated with poor outcome in over 50%. Etiological diagnosis of OAs is essential in guiding management and risk stratification.

Evaluation of Right Ventricular Function in Patients with Propionic Acidemia-A Cross-Sectional Study

(1) Background: In propionic acidemia (PA), myocardial involvement often leads to progressive cardiac dysfunction of the left ventricle (LV). Cardiomyopathy (CM) is an important contributor to mortality. Although known to be of prognostic value in CM, there are no published data on right ventricular (RV) function in PA patients. (2) Methods: In this cross-sectional single-center study, systolic and diastolic RV function of PA patients was assessed by echocardiography, including frequency, onset, and combinations of echocardiographic parameters, as well as correlations to LV size and function. (3) Results: N = 18 patients were enrolled. Tricuspid annulus S' was abnormal in 16.7%, RV-longitudinal strain in 11.1%, tricuspid annular plane systolic excursion (TAPSE) in 11.1%, Tricuspid valve (TV) E/e' in 33.3%, and TV E/A in 16.7%. The most prevalent combinations of pathological parameters were TV E/A + TV E/e' and TAPSE + TV S'. With age, the probability of developing abnormal RV function increases according to age-dependent normative data. There is a significant correlation between TAPSE and mitral annular plane systolic excursion (MAPSE), and RV/LV-longitudinal strain (p ≤ 0.05). N = 5 individuals died 1.94 years (mean) after cardiac evaluation for this study, and all had abnormal RV functional parameters. (4) Conclusions: Signs of diastolic RV dysfunction can be found in up to one third of individuals, and systolic RV dysfunction in 16.7% of individuals in our cohort. RV function is impaired in PA patients with a poor outcome. RV functional parameters should be used to complement clinical and left ventricular echocardiographic findings.

Detection of early cardiac disease manifestation in propionic acidemia - Results of a monocentric cross-sectional study

BACKGROUND

In propionic acidemia (PA) myocardial involvement is common and includes development of cardiomyopathy, life-threatening acute heart failure, and acquired long-QT syndrome. We sought to investigate which echocardiographic parameters of left ventricular systolic and diastolic function indicate early cardiac disease manifestation in PA.

METHODS

This is a prospective observational study (cross-sectional design) in a Tertiary Medical Care Center. Individuals with confirmed PA were enrolled and the following cardiac investigations were performed in all study individuals: echocardiographic measurements of systolic and diastolic left ventricular (LV) function (LV fractional shortening (LV-FS), LV ejection fraction by biplane modified Simpson's (LV-EF), mitral annular plane systolic excursion (MAPSE), LV global longitudinal strain (LV-GLS) by speckle tracking echocardiography (STE), pulsed Doppler analyses of mitral valve (MV) inflow velocities (MV E/A) and MV deceleration time (DT-E), tissue doppler imaging (TDI) of the mitral annulus (MV E/e'), and LV myocardial performance index (LV-MPI)). LV and left atrial (LA) diameters were assessed. 12‑lead electrocardiograms (ECG) were recorded and corrected QT intervals (QTc) calculated. Clinical phenotype and laboratory parameters at the time of cardiac investigation were assessed. Besides descriptive analyses we analyzed frequency, onset, and combinations of echocardiographic and ECG data as well as their correlations with clinical and biochemical findings. The effects of 'age at visit' and LV functional parameters on QTc were analyzed with multiple regression.

RESULTS

A total of 18 patients with confirmed PA were enrolled. Median age at PA onset was 6 days (range 1-357 days). Median age at visit for cardiac evaluation was 13.1 years (range 0.6-28.1 years). LV-GLS was abnormal in 72.2%, LV-EF in 61.1%, MAPSE in 50%, MV E/e' in 44.4%, LV-MPI in 33.3%, LV-FS in 33.3%, and MV E/A in 27.8%. In cases with normal or near normal LV-FS, LV-GLS was pathological in 5/10, LV-EF in 4/10, and MAPSE in 3/10. The probability of developing LV dysfunction - systolic and diastolic - increases with age. LV-MPI is a reliable parameter to indicate systolic LV-dysfunction in combination with a dilated LV, i. e. dilated cardiomyopathy (DCM) in PA. Multiple regression reveals a significant positive association between LV diameters and QTc. Abnormal LV-GLS significantly correlates with reduced muscle strength, muscle tone and/or abnormal gross motor function.

CONCLUSIONS

Our data suggests a high prevalence of cardiac disease manifestation in PA, considerably higher than in previous studies, where only LV-FS was used to assess LV function. Usage of advanced echocardiographic techniques, such as LV-GLS assessment, may allow for early detection of subtle LV dysfunction in PA, and may lead to timely cardiac treatment but also consideration of liver transplantation to prevent development of manifest cardiac complications.

Natural history of propionic acidemia in the Amish population

Propionic acidemia (PA) in the Amish is caused by a homozygous pathogenic variant (c.1606A>G; p.Asn536Asp) in the PCCB gene. Amish patients can have borderline or normal newborn screening (NBS) results and symptoms can present at any time from early childhood to mid-adulthood. Early diagnosis and initiation of treatment for PA in the non-Amish population improves patient outcomes. Here, we present data from a retrospective chart review of Amish patients diagnosed with PA from three different medical centers in order to document its natural history in the Amish and determine the influence of treatment on outcomes in this population. A total of 38 patients with average current age 19.9 years (range 4y-45y), 57.9% males, were enrolled in the study. Fourteen patients (36.8%) were diagnosed with a positive newborn screening (NBS) while 24 patients (63.2%) had negative or inconclusive NBS or had no record of NBS in their charts. These 24 patients were diagnosed by screening after a family member was diagnosed with PA (14; 58.3%), following a hospitalization for metabolic acidosis (5; 20.8%), hospitalization for seizures (3; 12.5%) or via cord blood (2; 8.3%). The majority of patients were prescribed a protein restricted diet (32; 84.2%), including metabolic formula (29; 76.3%). Most were treated with carnitine (35; 92.1%), biotin (2; 76.3%) and/or Coenzyme Q10 (16; 42.1%). However, treatment adherence varied widely among patients, with 7 (24.1%) of the patients prescribed metabolic formula reportedly nonadherent. Cardiomyopathy was the most prevalent finding (22; 63.2%), followed by developmental delay/intellectual disability (15; 39.5%), long QT (14; 36.8%), seizures (12; 31.6%), failure to thrive (4; 10.5%), and basal ganglia strokes (3; 7.9%). No difference in outcome was obvious for those diagnosed by NBS and treated early with dietary and supplement management, especially for cardiomyopathy. However, this is a limited retrospective observational study. A prospective study with strict documentation of treatment adherence and universal screening for cardiomyopathy and long QT should be conducted to better study the impact of early detection and treatment. Additional treatment options such as liver transplantation and future therapies such as mRNA or gene therapy should be explored in this population.

Therapeutic potential of living donor liver transplantation from heterozygous carrier donors in children with propionic acidemia

Background

Current world experience regarding living donor liver transplantation (LDLT) in the treatment of propionic acidemia (PA) is limited, especially in terms of using obligate heterozygous carriers as donors. This study aimed to evaluate the clinical outcomes of LDLT in children with PA.

Methods

From November 2017 to January 2020, 7 of the 192 children who underwent LDLT at our institution had been diagnosed with PA (median age, 2.1 years; range, 1.1–5.8 years). The primary indication for transplantation was frequent metabolic decompensations in 6 patients and preventative treatment in 1 patient. Of the seven parental living donors, six were genetically proven obligate heterozygous carriers.

Results

During a median follow-up of 23.9 months (range, 13.9–40.2 months), all patients were alive with 100% allograft survival, and no severe transplant-related complications occurred. In the case of liberalized protein intake, they did not suffer metabolic decompensation or disease-related complications and made progress in neurodevelopmental delay and body growth, as well as blood and urinary metabolite levels. In one patient with pre-existing mild dilated cardiomyopathy, her echocardiogram results completely normalized 13.8 months post-transplant. All living donors recovered well after surgery, with no metabolic decompensations or procedure-related complications. Western blotting revealed that the hepatic expressions of PCCA and PCCB in one of the heterozygous donors were comparable to those of the normal healthy control at the protein level.

Conclusions

LDLT using partial liver grafts from asymptomatic obligate heterozygous carrier donors is a viable therapeutic option for selected PA patients, with no negative impact on donors’ and recipients' clinical courses.

Guidelines for the diagnosis and management of methylmalonic acidaemia and propionic acidaemia: First revision

Isolated methylmalonic acidaemia (MMA) and propionic acidaemia (PA) are rare inherited metabolic diseases. Six years ago, a detailed evaluation of the available evidence on diagnosis and management of these disorders has been published for the first time. The article received considerable attention, illustrating the importance of an expert panel to evaluate and compile recommendations to guide rare disease patient care. Since that time, a growing body of evidence on transplant outcomes in MMA and PA patients and use of precursor free amino acid mixtures allows for updates of the guidelines. In this article, we aim to incorporate this newly published knowledge and provide a revised version of the guidelines. The analysis was performed by a panel of multidisciplinary health care experts, who followed an updated guideline development methodology (GRADE). Hence, the full body of evidence up until autumn 2019 was re-evaluated, analysed and graded. As a result, 21 updated recommendations were compiled in a more concise paper with a focus on the existing evidence to enable well-informed decisions in the context of MMA and PA patient care.

Liver Transplantation for Propionic Acidemia: Evidence from A Systematic Review and Meta-analysis

BACKGROUND

The worldwide experience of liver transplantation (LT) in the treatment of propionic acidemia (PA) remains limited and fragmented. This review aims to provide a comprehensive and quantitative understanding of post-transplant clinical outcomes in PA patients.

METHODS

MEDLINE, Embase and the Cochrane Library databases were searched for studies focusing on PA patients who underwent LT. The pooled estimate rates and 95% confidence intervals (CIs) were calculated using a random-effects model with Freeman-Tukey double arcsine transformation.

RESULTS

Twenty-one studies involving 70 individuals were included. The pooled estimate rates were 0.95 (95% CI, 0.80-1.00) for patient survival and 0.91 (95% CI, 0.72-1.00) for allograft survival. The pooled estimate rates were 0.20 (95% CI, 0.05-0.39) for rejection, 0.08 (95% CI, 0.00-0.21) for hepatic artery thrombosis, 0.14 (95% CI, 0.00-0.37) for cytomegalovirus/Epstein-Barr virus infection and 0.03 (95% CI, 0.00-0.15) for biliary complications. The pooled estimate rates were 0.98 (95% CI, 0.88-1.00) for metabolic stability, 1.00 (95% CI, 0.79-1.00) for reversal of pre-existing cardiomyopathy and 0.97 (95% CI, 0.78-1.00) for improvement of neurodevelopmental delay. A large proportion of patients achieved liberalization of protein intake posttransplant [pooled estimate rate 0.66 (95% CI, 0.35-0.93)].

CONCLUSIONS

Despite the risk of transplant-related complications, LT is a viable therapeutic option in PA patients, with satisfactory survival rates and clinical outcomes. Given the diversity in neurological assessment methods and the inconsistency in achievement of dietary protein liberalization across different studies, consensus on neurological evaluation methods and post-transplant protein intake is necessary. Longer-term clinical outcomes of LT for PA warrants further investigation.

The re-occurrence of cardiomyopathy in propionic acidemia after liver transplantation

Cardiomyopathy is a frequent complication of propionic acidemia (PA). It is often fatal, and its occurrence is largely independent of classic metabolic treatment modalities. Liver transplantation (LT) is a treatment option for severe PA as the liver plays a vital role in metabolism of the precursors that accumulate in patients with PA. LT in PA is now considered to be a long-lasting and valid treatment to prevent cardiac disease. The subject of this report had severe cardiomyopathy that largely disappeared prior to undergoing a LT. Three years following the transplant, there was recurrence of cardiomyopathy following a surgery that was complicated with a postoperative aspiration pneumonia. On his last hospital admission, he was presented with pulmonary edema and heart failure. He continued with episodes of intractable hypotension, despite maximum inotropic and diuretic support. He died following redirection of care. We conclude that lethal cardiomyopathy may develop several years after successful LT in patients with PA.

Liver Transplantation in Children With Propionic Acidemia: Medium-Term Outcomes

Liver transplantation (LT) for patients with propionic acidemia (PA) is an emerging therapeutic option. We present a retrospective review of patients with PA who underwent LT at a tertiary liver center between 1995 and 2015. A total of 14 children were identified (8 males) with median age at initial presentation of 3 days (range, 0-77 days). Pretransplant median protein restriction was 1 g/kg/day (range, 0.63-1.75 g/kg/day), 71% required supportive feeding, and 86% had developmental delay. Frequent metabolic decompensations (MDs) were the main indication for LT with a median age at transplantation of 2.4 years (range, 0.8-7.1 years). Only 1 graft was from a living donor, and 13 were from deceased donors (4 auxiliary). The 2-year patient survival was 86%, and overall study and graft survival was 79% and 69%, respectively. Three patients died after LT: at 43 days (biliary peritonitis), 225 days (acute-on-chronic rejection with multiorgan failure), and 13.5 years (posttransplant lymphoproliferative disease). Plasma glycine and propionylcarnitine remained elevated but reduced after transplant. Of 11 survivors, 5 had at least 1 episode of acute cellular rejection, 2 sustained a metabolic stroke (with full recovery), and 3 developed mild cardiomyopathy after LT. All have liberalized protein intake, and 9 had no further MDs: median episodes before transplant, 4 (range, 1-30); and median episodes after transplant, 0 (range, 0-5). All survivors made some developmental progress after LT, and none worsened at a median follow-up of 5.8 years (range, 2-23 years). LT in PA significantly reduces the frequency of MDs, can liberalize protein intake and improve quality of life, and should continue to be considered in selected cases.

Disturbance of bioenergetics and calcium homeostasis provoked by metabolites accumulating in propionic acidemia in heart mitochondria of developing rats

Propionic acidemia is caused by lack of propionyl-CoA carboxylase activity. It is biochemically characterized by accumulation of propionic (PA) and 3-hydroxypropionic (3OHPA) acids and clinically by severe encephalopathy and cardiomyopathy. High urinary excretion of maleic acid (MA) and 2-methylcitric acid (2MCA) is also found in the affected patients. Considering that the underlying mechanisms of cardiac disease in propionic acidemia are practically unknown, we investigated the effects of PA, 3OHPA, MA and 2MCA (0.05-5 mM) on important mitochondrial functions in isolated rat heart mitochondria, as well as in crude heart homogenates and cultured cardiomyocytes. MA markedly inhibited state 3 (ADP-stimulated), state 4 (non-phosphorylating) and uncoupled (CCCP-stimulated) respiration in mitochondria supported by pyruvate plus malate or α-ketoglutarate associated with reduced ATP production, whereas PA and 3OHPA provoked less intense inhibitory effects and 2MCA no alterations at all. MA-induced impaired respiration was attenuated by coenzyme A supplementation. In addition, MA significantly inhibited α-ketoglutarate dehydrogenase activity. Similar data were obtained in heart crude homogenates and permeabilized cardiomyocytes. MA, and PA to a lesser degree, also decreased mitochondrial membrane potential (ΔΨm), NAD(P)H content and Ca²⁺ retention capacity, and caused swelling in Ca²⁺-loaded mitochondria. Noteworthy, ΔΨm collapse and mitochondrial swelling were fully prevented or attenuated by cyclosporin A and ADP, indicating the involvement of mitochondrial permeability transition. It is therefore proposed that disturbance of mitochondrial energy and calcium homeostasis caused by MA, as well as by PA and 3OHPA to a lesser extent, may be involved in the cardiomyopathy commonly affecting propionic acidemic patients.

Intracellular calcium mishandling leads to cardiac dysfunction and ventricular arrhythmias in a mouse model of propionic acidemia

Propionic acidemia (PA) is a rare metabolic disease associated with mutations in genes encoding the α and β subunits of the enzyme propionyl-CoA carboxylase. The accumulation of toxic metabolites results in mitochondrial dysfunction, increased reactive oxygen species production and oxidative damage, which have been associated with the disease pathophysiology. Clinical symptoms are heterogeneous and include cardiac complications, mainly cardiac dysfunction and arrhythmias, which are recognized as one of the major life-threatening manifestations in patients. We aimed to investigate the molecular mechanisms underlying the cardiac phenotype using a hypomorphic mouse model (Pcca^-/-(A138T)) that recapitulates some biochemical and clinical characteristics of PA. We demonstrate that Pcca^-/-(A138T) mice present with depressed cardiac function along with impaired cell contractility when compared to the wild-type mice. Cardiac dysfunction in Pcca^-/-(A138T) mice was associated with lower systolic Ca²⁺ release ([Ca²⁺]_i transients), impairment in the sarcoplasmic reticulum (SR) Ca²⁺ load and decreased Ca²⁺ re-uptake by SR-Ca²⁺ ATPase (SERCA2a). These functional changes correlated well with the depressed activity of SERCA2a, the elevated ROS levels and SERCA2a oxidation rate in cardiomyocytes isolated from Pcca^-/-(A138T) mice. In addition, decreased SR-Ca²⁺ load in Pcca^-/-(A138T) cardiomyocytes was associated with increased diastolic Ca²⁺ release. The increase in Ca²⁺ sparks, Ca²⁺ waves and spontaneous [Ca²⁺]_i transients in Pcca^-/-(A138T) cardiomyocytes could be responsible for the induction of ventricular arrhythmias detected in these mice. Overall, our results uncover the role of impaired Ca²⁺ handling in arrhythmias and cardiac dysfunction in PA, and identify new targets for the development of therapeutic approaches for this devastating metabolic disease.

Reversal of cardiomyopathy in propionic acidemia after liver transplantation: a 10-year follow-up

Cardiomyopathy is a frequent complication in propionic acidemia. It is mostly rapidly fatal and independent of the metabolic control or medical intervention. Here, we present the reversal of a severe cardiomyopathy after liver transplantation in a patient with propionic acidemia and the long-term stability after ten years. Liver transplantation in patients with propionic acidemia may be considered a valid and long-lasting treatment when cardiomyopathy is progressive and unresponsive to medical therapy.

Proposed guidelines for the diagnosis and management of methylmalonic and propionic acidemia

Methylmalonic and propionic acidemia (MMA/PA) are inborn errors of metabolism characterized by accumulation of propionic acid and/or methylmalonic acid due to deficiency of methylmalonyl-CoA mutase (MUT) or propionyl-CoA carboxylase (PCC). MMA has an estimated incidence of ~ 1: 50,000 and PA of ~ 1:100’000 -150,000. Patients present either shortly after birth with acute deterioration, metabolic acidosis and hyperammonemia or later at any age with a more heterogeneous clinical picture, leading to early death or to severe neurological handicap in many survivors. Mental outcome tends to be worse in PA and late complications include chronic kidney disease almost exclusively in MMA and cardiomyopathy mainly in PA. Except for vitamin B₁₂ responsive forms of MMA the outcome remains poor despite the existence of apparently effective therapy with a low protein diet and carnitine. This may be related to under recognition and delayed diagnosis due to nonspecific clinical presentation and insufficient awareness of health care professionals because of disease rarity.

These guidelines aim to provide a trans-European consensus to guide practitioners, set standards of care and to help to raise awareness. To achieve these goals, the guidelines were developed using the SIGN methodology by having professionals on MMA/PA across twelve European countries and the U.S. gather all the existing evidence, score it according to the SIGN evidence level system and make a series of conclusive statements supported by an associated level of evidence. Although the degree of evidence rarely exceeds level C (evidence from non-analytical studies like case reports and series), the guideline should provide a firm and critical basis to guide practice on both acute and chronic presentations, and to address diagnosis, management, monitoring, outcomes, and psychosocial and ethical issues. Furthermore, these guidelines highlight gaps in knowledge that must be filled by future research. We consider that these guidelines will help to harmonize practice, set common standards and spread good practices, with a positive impact on the outcomes of MMA/PA patients.

Successful reversal of propionic acidaemia associated cardiomyopathy: evidence for low myocardial coenzyme Q10 status and secondary mitochondrial dysfunction as an underlying pathophysiological mechanism

Dilated cardiomyopathy is a rare complication in propionic acidaemia (PA). Underlying pathophysiological mechanisms are poorly understood. We present a child of Pakistani consanguineous parents, diagnosed with late-onset PA at 18months of age. He presented a mild phenotype, showed no severe further decompensations, normal growth and psychomotor development on a low protein diet and carnitine supplementation. At 15years, a mildly dilated left ventricle was noticed. At 17years he presented after a 2-3month history of lethargy and weight loss with severe decompensated dilated cardiomyopathy. He was stabilised on inotropic support and continuous haemofiltration; a Berlin Heart biventricular assist device was implanted. He received d,l-hydroxybutyrate 200mg/kg/day, riboflavin and thiamine 200mg/day each and coenzyme Q10 (CoQ10). Myocardial biopsy showed endocardial fibrosis, enlarged mitochondria, with atypical cristae and slightly low respiratory chain (RC) complex IV activity relative to citrate synthase (0.012, reference range 0.014-0.034). Myocardial CoQ10 was markedly decreased (224pmol/mg, reference range 942-2738), with a marginally decreased white blood cell level (34pmol/mg reference range 37-133). The dose of CoQ10 was increased from 1.5 to 25mg/kg/day. Cardiomyopathy slowly improved allowing removal of the external mechanical cardiac support after 67days. We demonstrate for the first time low myocardial CoQ10 in cardiomyopathy in PA, highlighting secondary mitochondrial impairment as a relevant causative mechanism. According to these findings, a high-dose CoQ10 supplementation could be a potential adjuvant therapeutic to be considered in PA-related cardiomyopathy.