Heart Transplantation Ameliorates Ambulation Capacity in Patients With Muscular Dystrophy - An Analysis of 9 Cases

Is Cardiac Transplantation Still a Contraindication in Patients with Muscular Dystrophy-Related End-Stage Dilated Cardiomyopathy? A Systematic Review

Inherited muscular diseases (MDs) are genetic degenerative disorders typically caused by mutations in a single gene that affect striated muscle and result in progressive weakness and wasting in affected individuals. Cardiac muscle can also be involved with some variability that depends on the genetic basis of the MD (Muscular Dystrophy) phenotype. Heart involvement can manifest with two main clinical pictures: left ventricular systolic dysfunction with evolution towards dilated cardiomyopathy and refractory heart failure, or the presence of conduction system defects and serious life-threatening ventricular arrhythmias. The two pictures can coexist. In these cases, heart transplantation (HTx) is considered the most appropriate option in patients who are not responders to the optimized standard therapeutic protocols. However, cardiac transplant is still considered a relative contraindication in patients with inherited muscle disorders and end-stage cardiomyopathies. High operative risk related to muscle impairment and potential graft involvement secondary to the underlying myopathy have been the two main reasons implicated in the generalized reluctance to consider cardiac transplant as a viable option. We report an overview of cardiac involvement in MDs and its possible association with the underlying molecular defect, as well as a systematic review of HTx outcomes in patients with MD-related end-stage dilated cardiomyopathy, published so far in the literature.

Ivabradine ameliorates cardiomyopathy progression in a Duchenne muscular dystrophy model rat

Duchenne muscular dystrophy (DMD) is an X-linked recessive myopathy caused by dystrophin mutations. Inevitable progressive cardiomyopathy is a current leading cause of premature death although respiratory management has improved the prognosis of patients with DMD. Recent evidence shows that reducing the heart rate is expected as one of the promising strategies for heart failure treatment, but administering a sufficient dose of β-blocker for patients with DMD with tachycardia is difficult because of their low blood pressure (BP). Thus, this study aimed to clarify the role of ivabradine, which suppresses cardiac sinus node pacemakers without decreasing BP, in ameliorating cardiomyopathy progression in a rat model with DMD. A trans-oral single ivabradine administration demonstrated a declined dose-dependent heart rate without any significant BP reduction. Trans-gastric repeated administrations of 5 mg/kg of ivabradine twice a day for 3 months showed ameliorated cardiomyopathy in DMD rats based on echocardiography and histopathological observations (left ventricular dysfunction, right ventricular dysfunction, and myocardial fibrosis) as compared with vehicle administration.Our finding indicates that ivabradine is expected as another treatment choice for patients with DMD having tachycardia.

Efficacy and Tolerability of Ivabradine for Cardiomyopathy in Patients with Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is an intractable X-linked myopathy caused by dystrophin gene mutations. Patients with DMD suffer from progressive muscle weakness, inevitable cardiomyopathy, increased heart rate (HR), and decreased blood pressure (BP). The aim of this study was to clarify the efficacy and tolerability of ivabradine treatment for DMD cardiomyopathy.A retrospective analysis was performed in 11 patients with DMD, who received ivabradine treatment for more than 1 year. Clinical results were analyzed before (baseline), 6 months after, and 12 months after the ivabradine administration.The initial ivabradine dose was 2.0 ± 1.2 mg/day and the final dose was 5.6 ± 4.0 mg/day. The baseline BP was 95/64 mmHg. A non-significant BP decrease to 90/57 mmHg was observed at 1 month but it recovered to 97/62 mmHg at 12 months after ivabradine administration. The baseline HR was 93 ± 6 bpm and it decreased to 74 ± 12 bpm at 6 months (P = 0.011), and to 77 ± 10 bpm at 12 months (P = 0.008). A linear correlation (y = 2.2x + 5.1) was also observed between the ivabradine dose (x mg/day) and HR decrease (y bpm). The baseline LVEF was 38 ± 12% and it significantly increased to 42 ± 9% at 6 months (P = 0.011) and to 41 ± 11% at 12 months (P = 0.038). Only 1 patient with the lowest BMI of 11.0 kg/m2 and BP of 79/58 mmHg discontinued ivabradine treatment at 6 months, while 1-year administration was well-tolerated in the other 10 patients.Ivabradine decreased HR and increased LVEF without lowering BP, suggesting it can be a treatment option for DMD cardiomyopathy.

Early cardiac rehabilitation after heart transplantation in a patient with limb-girdle muscular dystrophy: A case report

RATIONALE

Cardiac rehabilitation (CR) after heart transplantation (HT) decreases the mortality rate and increases exercise capacity of patients. Dilated cardiomyopathy develops in most patients with muscular dystrophy (MD), leading to advanced heart failure, necessitating the use of left ventricular assist devices or HT. As the clinical outcomes of left ventricular assist devices and HT in patients with myopathy differ from those in patients without myopathy, CR adapted to patients with MD should be considered.

PATIENT CONCERNS

A 39-year-old man with limb-girdle muscular dystrophy developed dilated cardiomyopathy and underwent HT.

DIAGNOSIS

The patient was diagnosed as having limb-girdle muscular dystrophy in 1997.

INTERVENTION

Early CR was performed based on the patient's physical condition and ability.

OUTCOMES

With chest physiology, aerobic, and resistance exercises, the patient was able to walk using a walker 28 days after HT. This is important because his lower-extremity strength and walking ability were, to some extent, maintained after surgery.

LESSONS

Since an increasing number of patients with MD are undergoing HT, specific CR programs for these patients should be discussed.

A medium-chain triglyceride containing ketogenic diet exacerbates cardiomyopathy in a CRISPR/Cas9 gene-edited rat model with Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is an X-linked recessive myopathy caused by dystrophin mutations. Although respiratory management has improved the prognosis of patients with DMD, inevitable progressive cardiomyopathy is a current leading cause of premature death. Recently, we showed that a medium-chain triglyceride containing ketogenic diet (MCTKD) improves skeletal muscle function and pathology in a CRISPR/Cas9 gene-edited rat model with DMD. In this study, we sought to clarify whether MCTKD also improves the cardiomyopathy in these rats. DMD rats were fed either the MCTKD or normal diet (ND) from ages of 3 weeks to 9 months old. Compared with the ND-fed rats, MCTKD-fed rats showed significantly prolonged QRS duration, decreased left ventricular fractional shortening, an increased heart weight/body weight ratio, and progression of cardiac fibrosis. In contrast to our previous study which found that MCTKD improved skeletal myopathy, the current study showed unexpected exacerbation of the cardiomyopathy. Further studies are needed to explore the underlying mechanisms for these differences and to explore modified dietary options that improve skeletal and cardiac muscles simultaneously.

Age-Dependent Echocardiographic and Pathologic Findings in a Rat Model with Duchenne Muscular Dystrophy Generated by CRISPR/Cas9 Genome Editing

Duchenne muscular dystrophy (DMD) is X-linked recessive myopathy caused by mutations in the dystrophin gene. Although conventional treatments have improved their prognosis, inevitable progressive cardiomyopathy is still the leading cause of death in patients with DMD. To explore novel therapeutic options, a suitable animal model with heart involvement has been warranted.We have generated a rat model with an out-of-frame mutation in the dystrophin gene using CRISPR/Cas9 genome editing (DMD rats). The aim of this study was to evaluate their cardiac functions and pathologies to provide baseline data for future experiments developing treatment options for DMD.In comparison with age-matched wild rats, 6-month-old DMD rats showed no significant differences by echocardiographic evaluations. However, 10-month-old DMD rats showed significant deterioration in left ventricular (LV) fractional shortening (P = 0.024), and in tissue Doppler peak systolic velocity (Sa) at the LV lateral wall (P = 0.041) as well as at the right ventricular (RV) free-wall (P = 0.004). These functional findings were consistent with the fibrotic distributions by histological analysis.Although the cardiac phenotype was milder than anticipated, DMD rats showed similar distributions and progression of heart involvement to those of patients with DMD. This animal may be a useful model with which to develop effective drugs and to understand the underlying mechanisms of progressive heart failure in patients with DMD.