atrial-natriuretic-factor and Muscular-Dystrophy--Duchenne

Heart failure (HF) is a fatal complication in many muscular dystrophy cases and has become the most common cause of death in Duchenne muscular dystrophy (DMD) since 2001. HF deaths in DMD occur in young patients and increase, along with respiratory failure, in older patients. Managing HF, therefore, is the most important component of DMD treatment. Management of HF is necessary in DMD patients of all ages because myocardial damage progresses regardless of age and disability. Electrocardiography, echocardiography, myocardial single-photon emission computed tomography (SPECT), and natriuretic peptides are used for the diagnosis of myocardial damage and chronic HF. Tissue Doppler echocardiography is in particularly useful for early detection of minute myocardial damage and dysfunction in DMD. The first-line drugs for chronic HF are angiotensin-converting enzyme inhibitors, and the prognosis of DMD patients has been improved using these drugs and beta-blockers. Diuretics are added in the presence of pulmonary congestion. Digoxin is most effective at a blood level of 0.5-0.8 ng/mL because of its pharmacokinetics in DMD. Surgical treatment may be necessary in cases of intractable HF. Cardiac resynchronization therapy (biventricular pacing), a treatment with an artificial pacemaker, is indicated for cases that meet specific criteria, including HF with ventricular dyssynchrony. Applications of partial left ventriculectomy (Batista procedure) and left ventricular assist devices in muscular dystrophy are likely in the near future.

Topics: Adrenergic beta-Antagonists; Angiotensin-Converting Enzyme Inhibitors; Atrial Natriuretic Factor; Biomarkers; Cardiac Resynchronization Therapy; Cardiomyopathies; Chronic Disease; Diagnostic Imaging; Heart Failure; Humans; Muscular Dystrophy, Duchenne; Natriuretic Peptide, Brain

Dystrophinopathies are due to mutations in the dystrophin gene on chromosome Xp21.1 and comprise the allelic entities Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD) and X-linked dilative cardiomyopathy (XLDCM). In all three entities, the heart is affected to various degrees, depending on the stage of the disease and the type of the mutation (cardiac involvement, CI). The pathoanatomic evidence of CI in dystrophinopathies is the replacement of myocardium by connective tissue or fat. In DMD/BMD, the left ventricular posterobasal and lateral walls are most extensively affected, sparing the right ventricle and the atrium. Degree and dynamics of CI vary among the three entities. In DMD/BMD, CI usually remains subclinical in the early stages of the disease. Typical initial manifestations of CI in DMD/BMD are sinus tachycardia, tall R1 in V1, prominent Q in I, aVL, V6 or in II, III, and aVF, increased QT dispersion and possibly autonomic dysfunction. Initially, echocardiography is normal or shows regional wall motion abnormalities in areas of fibrosis. With spreading of fibrosis, left ventricular dysfunction and ventricular arrhythmias additionally occur. In the final stages of the disease, systolic function may lead to heart failure and sudden death. Subclinical or clinical CI is present in about 90% of the DMD/BMD patients but is the cause of death in only 20% of the DMD and 50% of the BMD patients. XLDCM is a rapidly progressive, almost exclusively myocardial disorder, starting in teenage males as heart failure due to dilative cardiomyopathy (CMP), leading to death from intractable heart failure within 1-2 years after diagnosis. Therapy of arrhythmias and CMP in all three disorders follows the established cardiological recommendations. Due to its protective effect, ACE inhibitors are recommended already at the early stages of the disease. Beta-blockers may be an additional option if indicated.

Topics: Atrial Natriuretic Factor; Cardiomyopathy, Dilated; Diagnostic Imaging; Electrocardiography; Heart Conduction System; Heart Diseases; Humans; Muscular Dystrophies; Muscular Dystrophy, Duchenne; Myocardium; Natriuretic Peptide, Brain; Signal Processing, Computer-Assisted

Duchenne muscular dystrophy (DMD) is caused by absence of the integral structural protein, dystrophin, which renders muscle fibres susceptible to injury and degeneration. This ultimately results in cardiorespiratory dysfunction, which is the predominant cause of death in DMD patients, and highlights the importance of therapeutic targeting of the cardiorespiratory system. While there is some evidence to suggest that restoring dystrophin in the diaphragm improves both respiratory and cardiac function, the role of the diaphragm is not well understood. Here using exon skipping oligonucleotides we predominantly restored dystrophin in the diaphragm and assessed cardiac function by MRI. This approach reduced diaphragmatic pathophysiology and markedly improved diaphragm function but did not improve cardiac function or pathophysiology, with or without exercise. Interestingly, exercise resulted in a reduction of dystrophin protein and exon skipping in the diaphragm. This suggests that treatment regimens may require modification in more active patients. In conclusion, whilst the diaphragm is an important respiratory muscle, it is likely that dystrophin needs to be restored in other tissues, including multiple accessory respiratory muscles, and of course the heart itself for appropriate therapeutic outcomes. This supports the requirement of a body-wide therapy to treat DMD.

Topics: Amino Acid Sequence; Animals; Atrial Natriuretic Factor; Blotting, Western; Diaphragm; Disease Models, Animal; Dystrophin; Gene Expression; Heart; Humans; Magnetic Resonance Imaging; Male; Mice, Inbred C57BL; Mice, Inbred mdx; Morpholinos; Muscle, Skeletal; Muscular Dystrophy, Duchenne; NADPH Oxidase 4; NADPH Oxidases; Natriuretic Peptide, C-Type; Peptides; Physical Conditioning, Animal; Protein Precursors; Radiography; Reverse Transcriptase Polymerase Chain Reaction

A boy with Duchenne muscular dystrophy was admitted to our hospital due to a transient loss of consciousness. Transthoracic echocardiography revealed left ventricular (LV) dilatation and diffuse hypokinesis of the LV wall. The LV wall was thin, and both non-compaction of the LV wall and marked thinning of the posterior LV wall resulting from a lesion were observed. The plasma B-type natriuretic peptide (BNP) level ultimately increased to 7,795 pg/mL, and the patient died of cardiac arrest following ventricular tachycardia. Severe heart failure, a critical condition, and thinning of the LV wall may have contributed to the markedly high plasma BNP level in this case.

Topics: Adolescent; Atrial Natriuretic Factor; Biomarkers; Diuretics; Fatal Outcome; Heart Failure; Humans; Male; Muscular Dystrophy, Duchenne; Natriuretic Peptide, Brain; Ultrasonography; Ventricular Dysfunction, Left

Initial signs of cardiac dysfunction caused by Duchenne muscular dystrophy are usually detected during adolescence. However, decreased physical activity can allow better tolerance of decreased cardiac function. Mild myocardial dysfunction secondary to ischemic or idiopathic cardiomyopathy is accompanied by elevation of plasma levels of norepinephrine and atrial natriuretic factor. This is considered an adaptation to maintain adequate perfusion. We evaluated neurohormone levels in 17 adolescents (median age 14 years) with Duchenne muscular dystrophy and different degrees of ventricular dysfunction determined by echocardiography. All patients were asymptomatic. Electrocardiographic abnormalities were present in 14 of 17 (82%). Shortening fraction was below normal in 9 of 17 (53%). Norepinephrine plasma levels were elevated in 3, and all had normal atrial natriuretic factor levels. There was no association between fractional shortening and norepinephrine plasma level (P = .66). The majority of younger adolescents with Duchenne muscular dystrophy and abnormal ventricular function do not show signs of inadequate perfusion, as evidenced by normal measurements of neurohormones.

Topics: Adolescent; Atrial Natriuretic Factor; Child; Echocardiography; Heart Rate; Humans; Male; Muscular Dystrophy, Duchenne; Norepinephrine; Systole; Ventricular Dysfunction

Dilated cardiomyopathy is a common complication of Duchenne and Becker muscular dystrophies, which are caused by mutations in the dystrophin gene. The mdx mouse is an animal model for Duchenne muscular dystrophy (DMD) and shows mildly dystrophic changes in the heart. By contrast, the utrophin-dystrophin knockout (dko) mouse shows severe dystrophic changes in cardiac muscle, that more closely resembles DMD cardiomyopathy than mdx mouse. However the pathogenesis of development has not been fully understood. Recently many reports have revealed that calcineurin and stress activated protein kinase (SAPK)/p38-mitogen activated protein kinase (MAPK) hypertrophic signalling pathways are associated with the development of some forms of hypertrophic and dilated cardiomyopathies. These signalling pathways may have some roles in the development of dystrophin-deficient cardiomyopathy. Here we report that calcineurin and SAPK/p38-MAPK signalling pathways were constantly activated in dko hearts, but the activation varied in mdx hearts. The pathogenesis of the development of dystrophin-deficient cardiomyopathy may be associated with the activation of these signalling pathways.

Topics: Age Factors; Animals; Atrial Natriuretic Factor; Calcineurin; Cardiomyopathy, Dilated; Cytoskeletal Proteins; Dystrophin; Glyceraldehyde-3-Phosphate Dehydrogenases; Membrane Proteins; Mice; Mice, Inbred C57BL; Mice, Knockout; Mitogen-Activated Protein Kinase 8; Mitogen-Activated Protein Kinases; Muscular Dystrophy, Duchenne; Myocardium; Natriuretic Peptide, Brain; p38 Mitogen-Activated Protein Kinases; Receptor, Angiotensin, Type 1; Receptor, Angiotensin, Type 2; Receptors, Angiotensin; RNA, Messenger; Signal Transduction; Utrophin