Cardiomyopathy in myotonic dystrophy

Article written and reviewed by Dr Luca Moretti

Myotonic dystrophy is an autosomal dominant multisystem disease in which the heart may become diseased relatively independently of muscle weakness. The most characteristic finding is not a single ventricular morphology but a variable combination of conduction-system disease, atrial arrhythmias, ventricular tachyarrhythmias and myocardial dysfunction. A person who can walk and has no palpitations may already have clinically relevant infra-Hisian delay. The silent cardiac phenotype makes scheduled surveillance essential and not dependent on symptoms.

The two molecular forms, DM1 and DM2, share a mechanism of RNA toxicity but are not interchangeable. DM1, traditionally called Steinert disease, spans congenital disease to late paucisymptomatic disease and accounts for most available cardiology data. DM2 generally begins in adulthood with proximal weakness, pain and myotonia, has on average less frequent cardiac involvement, but can still cause block, atrial fibrillation, ventricular arrhythmias and cardiomyopathy. The DM1-DM2 distinction guides counseling and prognosis without justifying neglect of the heart in the second form.

Modern management links the neurologist, cardiologist, electrophysiologist, pulmonologist, anesthesiologist and geneticist. The goal is not only to prevent complete atrioventricular block, because sudden deaths have also been observed after pacing and may result from ventricular tachycardia, electromechanical dissociation, embolism or respiratory failure. Every decision must therefore integrate conduction, myocardial substrate, rhythm, ventilation and functional trajectory. A multidimensional assessment is more reliable than an isolated threshold.

Expansion genetics and RNA toxicity

DM1 is caused by an expansion of CTG triplets in the 3' untranslated region of DMPK on chromosome 19. Normal alleles are stable, whereas intermediate alleles may expand during transmission and pathogenic alleles contain at least approximately fifty repeats, with large differences among tissues. Diagnostic techniques must detect very large expansions and mosaicism, which is why normal exon sequencing does not exclude the disease. The DMPK expansion test requires dedicated methods and interpretation according to laboratory standards.

The repeat length measured in blood correlates only approximately with age at onset and severity. The expansion is somatically unstable, may increase over time and differs among leukocytes, muscle and heart; age, allele structure and sequence interruptions also modify expression. It is therefore scientifically incorrect to convert a CTG number into an individual prediction of pacemaker implantation or sudden death. Somatic mosaicism limits simple correlations between blood genotype and cardiac risk.

DM1 shows anticipation, meaning a tendency toward earlier onset and greater severity in successive generations because of intergenerational expansion. Maternal transmission of highly expanded alleles is particularly associated with congenital disease, characterized by neonatal hypotonia, respiratory failure and later multisystem disease; this does not mean that fathers cannot transmit DM1. An apparently negative family history may reflect a late-onset or unrecognized parent or mosaicism. Anticipation in DM1 should be explained without presenting it as an invariable destiny.

DM2 results from a large CCTG expansion in intron 1 of CNBP, formerly called ZNF9, on chromosome 3. This lesion also requires a specific assay and may be technically difficult because of its size and heterogeneity. The relationship between repeat number and severity is even less useful than in DM1, clinical anticipation is not predictable, and a recurrent congenital form is not the typical phenotype, although exceptions have been described. Molecular diagnosis of DM2 should not be based on the absence of obvious myotonia or cataract.

In both forms, injury does not primarily result from loss of the encoded protein but from a toxic RNA gain of function. Expanded CUG transcripts in DM1 and CCUG transcripts in DM2 form nuclear foci, sequester Muscleblind proteins, especially MBNL1 and MBNL2, and alter regulation of CELF1 and numerous splicing programs. Adult tissues thereby re-express inappropriate fetal isoforms. RNA spliceopathy provides a unifying mechanism for muscular, cardiac, endocrine and neurologic manifestations.

In the heart, aberrant splicing of SCN5A is particularly relevant, altering the Nav1.5 sodium channel and contributing to slowed conduction and arrhythmic vulnerability. Other transcripts involve the contractile apparatus, intracellular calcium, junctions and metabolism, while fibrosis and fatty replacement amplify the electrical defect. The MBNL model does not encompass all biology because gene expression, RAN translation and modifiers may also contribute. An acquired splicing channelopathy therefore overlaps with a progressive structural cardiomyopathy.

DM1 and DM2 phenotypes across the lifespan

Congenital and childhood DM1 requires a cardiology pathway from pediatric age, even when the initial priorities are ventilation, nutrition and development. Classic disease includes myotonia, distal weakness, characteristic facies, cataracts, endocrine disorders, sleepiness and respiratory impairment; cardiac disease may precede or follow these signs. Mild forms with cataract and modest myotonia are not cardiologically benign. Cardiac-neuromuscular discordance prevents electrical risk from being inferred from strength alone.

DM2 often begins with pain, stiffness and proximal or axial weakness, whereas clinical myotonia may be modest and recognition delayed. Longitudinal series indicate a lower average frequency of conduction abnormalities and muscle injury than in DM1, but the difference is quantitative rather than absolute. Ventricular dysfunction, fibrosis on magnetic resonance, advanced blocks and sudden death are documented. Cardiac risk in DM2 justifies a similar baseline protocol, subsequently adapted to phenotype.

Cardiac penetrance increases with age and disease duration, with prevalence rising when Holter monitoring and imaging are added to ECG alone. A recent cohort of genetically confirmed DM1 showed an increase in overall involvement from 42 to 66 percent after median follow-up exceeding ten years, while only a minority reported cardiac symptoms. These figures depend on definitions and selection and are not universal percentages. Time-dependent progression makes it inappropriate to end follow-up after a normal assessment.

Diabetes, dyslipidemia, obesity, sedentary behavior, obstructive sleep apnea and respiratory disease may add an acquired burden to the genetic substrate. Blood pressure may be low because of dysautonomia or reduced muscle mass, but hypertension and coronary disease are not excluded. Chest pain, troponin elevation or new dysfunction therefore require an ordinary differential diagnosis including ischemia, myocarditis, embolism and toxicity. A nonexclusive diagnosis prevents every event from being automatically attributed to the dystrophy.

Electrical and myocardial substrate

Histopathology describes interstitial fibrosis, cardiomyocyte degeneration, fatty infiltration and involvement of the sinoatrial node, atrioventricular node, His bundle and bundle branches. Irregular distribution explains why conduction can deteriorate without a severe reduction in ejection fraction. Endomyocardial biopsy is not required for routine diagnosis and may miss focal lesions. His-Purkinje system injury is the principal target of electrical surveillance.

Disease may slow conduction at multiple levels, producing sinus bradycardia, atrioventricular block, hemiblock, bundle branch block and diffuse QRS widening. Evolution is not perfectly linear: a stable ECG does not guarantee that paroxysmal block will not occur, and a long PR interval alone does not localize the delay. Invasive measurement of the His-ventricular interval better separates the infra-Hisian component. Multilevel conduction disease requires PR, QRS and HV to be interpreted as complementary information.

Atrial myocardium is vulnerable to dilation, fibrosis and heterogeneous conduction, conditions that promote flutter, atrial tachycardia and atrial fibrillation. These arrhythmias may be silent because of limited physical activity or present as worsening fatigue, reduced ventilatory capacity and heart failure. An apparently controlled ventricular rate may reflect concomitant nodal disease. Atrial myopathy is therefore both an electrical complication and an indicator of progression.

In the ventricle, fibrosis and slowed conduction favor reentry, including bundle branch reentrant tachycardia in patients with diffusely diseased His-Purkinje systems. Ventricular ectopy and nonsustained ventricular tachycardia may precede sustained events, but their significance depends on burden, function and context. Sudden death may also result from block, ventricular fibrillation or nonarrhythmic causes. The mixed arrhythmic substrate explains why a pacemaker does not provide complete protection.

Clinical surveillance, ECG and monitoring

Initial assessment documents syncope, presyncope, palpitations, dyspnea, chest pain, edema, family history of sudden death and drugs that slow conduction or prolong QT. Symptoms should be sought with concrete examples because sleepiness, apathy, motor limitation and reduced perception of exertion decrease their reliability. An unexplained fall may represent syncope and functional decline may conceal fibrillation. A disability-adapted history reduces underestimation of events.

A 12-lead ECG is recommended at diagnosis and then at least annually according to the main cardiology consensus documents. Rhythm, rate, PR, QRS duration and axis, fascicular or bundle branch blocks, Q waves, repolarization and corrected QT should be archived and compared with previous tracings rather than relying only on the automated report. Rate of change may matter as much as the threshold reached. The longitudinal ECG record turns isolated measurements into a conduction trajectory.

Ambulatory monitoring identifies pauses, intermittent blocks, atrial fibrillation, flutter, ectopy and ventricular tachycardias missed by ECG. A recent 24-hour Holter study detected many new findings even in patients with a normal ECG, supporting broader periodic use; older series had judged systematic yield to be low. Duration and frequency should therefore reflect age, baseline abnormalities, symptoms and therapeutic consequences. Risk-proportionate monitoring may range from 24 hours to multiday patches.

An implantable loop recorder is reasonable when syncope or palpitations are rare, when conduction is abnormal but the HV interval does not reach the pacing threshold, or when documenting an arrhythmia would change the choice among observation, pacemaker and ICD. It does not replace a therapeutic device in someone who already has a pacing indication and should not delay treatment of advanced block. Remote transmission requires explicit clinical responsibility. A selective loop recorder is a diagnostic tool, not a guarantee of capturing the first lethal event.

Echocardiography or CMR is performed at baseline and, if normal, repeated every one to five years according to age and risk, more often with an abnormal ECG, arrhythmias or symptoms. Assessment includes biventricular function, atrial volumes, valves, pulmonary pressure and strain when reproducible. Biomarkers such as BNP or troponin may clarify a clinical change but do not replace rhythm assessment and imaging. Multimodal surveillance prevents preserved ejection fraction from concealing electrical progression.

Infra-Hisian conduction and electrophysiologic study

Prolonged PR and wide QRS are simple markers of conduction disease but do not directly measure an individual's risk of block. PR at least 240 milliseconds or QRS at least 120 milliseconds has identified higher-risk groups and appears in device recommendations. A DM1 registry analysis published in 2025 showed that HV at least 70 milliseconds discriminated major bradyarrhythmic events better than ECG criteria alone; an exploratory threshold of 65 increased sensitivity at the cost of many false positives and did not replace the guideline threshold. Electrocardiographic cutoffs select further investigation without replacing it.

Electrophysiologic study records atrial, nodal and His-Purkinje conduction and measures the HV interval. HV at least 70 milliseconds indicates significant infra-Hisian disease and is associated with progression to advanced block; European guidelines consider pacing even in an asymptomatic patient in this situation. Measurement may vary with drugs, heart rate and technique and must be interpreted in context. A pathologic HV interval has a primarily bradyarrhythmic role and does not predict all ventricular tachyarrhythmias.

ESC pacing guidelines indicate implantation with second- or third-degree atrioventricular block and with HV at least 70 milliseconds regardless of symptoms; they also allow pacing to be considered when PR at least 240 and QRS at least 120 milliseconds coexist. The 2022 HRS consensus uses broader wording: pacing is reasonable with PR at least 240 or native QRS at least 120 milliseconds and when HV is at least 70 milliseconds. Classes and levels of evidence reflect observational data rather than large randomized trials. Isolated first-degree block does not automatically equal a pacemaker in every patient. The pacing decision combines thresholds, progression, age, syncope and access to follow-up.

A strategy of electrophysiologic study and prophylactic pacing in DM1 patients with conduction abnormalities was associated with better survival than noninvasive surveillance in a large registry, but the analysis was observational and subject to confounding. The finding supports the clinical usefulness of HV without demonstrating that every patient should undergo invasive testing. EPS is particularly useful when the result concretely changes device choice. Nonrandomized evidence requires shared and transparent decision-making.

Programmed ventricular stimulation seeks tachyarrhythmic vulnerability, which differs from HV measurement. In the prospective ACADEMY-1 study, inducibility had limited value in separating those who would experience arrhythmic events and should not be the sole criterion for choosing an ICD rather than a pacemaker. By contrast, documented spontaneous ventricular tachycardia has direct clinical significance. The distinction between HV and inducibility prevents attributing two nonequivalent prognostic capabilities to a single EPS.

Arrhythmias and risk of sudden death

Atrial fibrillation and flutter are more frequent and occur earlier than in the general population. A systematic review estimated mean atrial fibrillation prevalence near eleven percent in DM1, but the figure varies with age, monitoring duration and device presence. Recognition matters because the arrhythmia predicts conduction events, may worsen function and introduces embolic risk. Subclinical atrial fibrillation is often discovered by Holter monitoring or device memory.

Ventricular arrhythmias include nonsustained tachycardia, monomorphic tachycardia, bundle branch reentry and ventricular fibrillation. In a French cohort of 1,388 adults followed for about ten years, sustained ventricular tachyarrhythmia was less frequent than new major conduction defects, and nonsustained tachycardia was the main independent predictor of the sustained form. This does not make every short run an automatic ICD indication. The weight of NSVT depends on function, syncope, substrate and need for pacing.

In the same cohort, 3.6 percent died suddenly, with heterogeneous documented mechanisms: ventricular tachyarrhythmia, asystole, complete block, electromechanical dissociation and even noncardiac causes at autopsy. Age, family history of sudden death and left bundle branch block were independent predictors of sudden death, whereas atrial fibrillation, syncope and conduction abnormalities mainly predicted new major defects. Multimodal sudden death cannot be reduced to bradycardia alone.

The historical Groh study associated sudden death with a severely abnormal ECG, defined by nonsinus rhythm, markedly prolonged PR, wide QRS or advanced atrioventricular block, and with atrial tachyarrhythmia. These findings remain warning signs but derive from populations and practices predating remote surveillance and current therapies. Predictive value in an individual remains imperfect. Dynamic stratification requires reassessment after every change in rhythm, conduction or function.

There is no universally validated score that converts age, CTG, PR, QRS, LGE and arrhythmias into a reliable individual probability of sudden death in DM1 or DM2. An internally validated DM1 score for ten-year overall survival is available, but its endpoint includes all-cause mortality and does not justify pacemaker or ICD decisions. Calculators developed for hypertrophic cardiomyopathy, LMNA or sarcoidosis are not transferable, while ventricular inducibility and LGE burden have no validated DM-specific thresholds for defibrillation. Limitations of scores require expert multidisciplinary review and discussion of uncertainty.

Pacemaker, ICD, ablation and device follow-up

A pacemaker prevents syncope and death from bradycardia or block, but timing should preferably precede a major event. Second-degree block, third-degree block and HV at least 70 milliseconds are robust indications even without symptoms; markedly prolonged PR and QRS, rapid progression or syncope lower the threshold for a preventive strategy. In young people, decades of leads, revisions and venous access must be considered. Pacing design should anticipate disease evolution.

The choice between pacemaker and ICD does not depend on pacing need alone. Cardiac arrest from tachyarrhythmia and nonreversible sustained ventricular tachycardia indicate secondary prevention; for primary prevention, established cardiomyopathy indications are applied and ventricular dysfunction, NSVT, syncope, scar and family history are integrated. Registries have documented appropriate therapies and sudden deaths even in pacemaker recipients. A selective ICD provides tachyarrhythmic protection at the cost of shocks, infections and revisions.

An ejection fraction of 35 percent or less despite appropriate therapy supports ICD implantation according to general guidelines, but many deaths in myotonic dystrophy occur with higher function. In intermediate cases, HRS consensus allows an ICD to be considered, especially when a device is already needed and arrhythmic markers are present, without providing a deterministic algorithm. Respiratory capacity, overall prognosis and patient goals matter as much as electrical findings. Defibrillator proportionality avoids both undertreatment and disproportionate procedures.

A high proportion of right ventricular pacing may cause dyssynchrony and worsen already vulnerable function. CRT is used when usual criteria for dysfunction, QRS and pacing burden are met; conduction-system pacing is promising but specific data in myotonic dystrophy remain limited. The decision should consider venous anatomy, life expectancy and upgrade feasibility. Physiologic ventricular pacing should not be presented as treatment of the spliceopathy.

Device follow-up includes thresholds, impedances, battery, pacing percentages, atrial and ventricular arrhythmias and evolution of intrinsic conduction. Remote monitoring reduces time to recognition of fibrillation and tachycardia but does not replace visits and imaging. Overly sensitive programming may classify noise or myopotentials as arrhythmia, while inappropriate detection zones may miss relatively slow tachycardias. Interpreted telemetry requires review of electrograms rather than automatic counters alone.

Flutter and supraventricular tachycardias can be ablated according to anatomy and symptoms; bundle branch reentry is a specific target when documented. Ablation does not remove atrial myopathy, progression of conduction disease or the risk of new arrhythmias, and may reveal a previously latent pacing need. Antiarrhythmic drugs are selected considering QRS, function and respiratory vulnerability. Circuit ablation treats one mechanism without curing systemic disease.

Cardiac imaging and heart-failure therapy

Left ventricular systolic dysfunction is less frequent than electrical disease but has strong prognostic value. A systematic review estimated mean prevalence of 13.8 percent in DM1, with higher values when strain or CMR was used and in older cohorts. Dilation, regional hypokinesia and right ventricular dysfunction may also occur without symptoms. Subclinical cardiomyopathy justifies serial imaging despite an apparently dominant ECG phenotype.

Echocardiography measures volumes, ejection fraction, diastolic function, atria, valves and pulmonary pressure. Longitudinal strain may identify early dysfunction but depends on image quality and has no DM-specific prognostic cutoff. A poor acoustic window or discordant result directs assessment to CMR. Reproducible quantification requires comparison in the same laboratory and attention to heart rate and pacing.

Magnetic resonance defines biventricular function and fibrous replacement using late gadolinium enhancement and mapping. LGE may be present with preserved ejection fraction and provides a plausible explanation for arrhythmias, but distribution and prevalence vary and no extent has been validated as an independent ICD threshold. Gadolinium requires renal assessment and some devices require dedicated protocols. Fibrosis on CMR adds context without producing an automatic verdict.

Heart failure with reduced ejection fraction is treated, when tolerated, with ARNI or an ACE inhibitor or ARB, beta-blocker, mineralocorticoid receptor antagonist and SGLT2 inhibitor according to general guidelines. There are no large trials dedicated to myotonic dystrophy, and hypotension, bradycardia, gastrointestinal disorders and low muscle mass may limit titration and interpretation of creatinine. Beta-blockade requires particular caution without protection against block. Transferred heart-failure therapy must be individualized and monitored.

Congestion and arrhythmia are treated without attributing all dyspnea to the heart because hypoventilation and respiratory weakness are often predominant. In advanced cases, CRT, mechanical support and transplantation are assessed considering respiratory function, swallowing, rehabilitation and ability to adhere to a complex pathway. The systemic genetic disease does not recur in the graft, but extracardiac manifestations persist. Advanced cardiac therapy requires early multidisciplinary selection rather than automatic exclusion.

Atrial fibrillation and anticoagulation

Management of atrial fibrillation includes rate or rhythm control, identification of reversible factors and stroke prevention. Drugs that slow nodal conduction may precipitate bradycardia in an already diseased system, while some antiarrhythmics widen the QRS or prolong QT. Cardioversion and ablation are possible, but recurrences reflect the underlying atrial myopathy. The rhythm strategy should be coordinated with any pacing indication.

Anticoagulation is not prescribed for genotype alone but according to thromboembolic risk validated by the adopted guideline, currently CHA2DS2-VA in Europe, and modifiable bleeding risk. Myotonic dystrophy introduces elements not perfectly captured by scores: falls, dysphagia, respiratory failure, low body weight, uncertain renal-function estimation and executive difficulties. These factors guide drug choice, dose and support but do not by themselves justify withholding indicated therapy. Personalized embolic prevention requires periodic reassessment of adherence and renal function.

DOACs are generally preferred to vitamin K antagonists in nonvalvular atrial fibrillation when there is no moderate or severe rheumatic mitral stenosis, mechanical valve or other contraindication. Very low creatinine due to reduced muscle mass may overestimate renal function; when dosing is uncertain, alternative estimates and clinical assessment are useful. Dysphagia and enteral feeding require checking administration requirements for the specific drug. The correct anticoagulant dose should not be empirically reduced because of fear of falls.

Device-detected atrial episodes require confirmation of the electrogram, duration and burden before being equated with clinical atrial fibrillation. The threshold for anticoagulating a short subclinical arrhythmia is not specifically defined for DM1 or DM2 and follows general evidence while considering individual risk. Embolic risk does not automatically disappear after ablation. A documented rhythm diagnosis prevents chronic therapy based on device false positives.

Respiration, sleep, anesthesia and drugs

Diaphragmatic weakness, reduced cough, obstructive or central apneas and impaired ventilatory control may cause nocturnal hypoxemia and hypercapnia. These conditions increase ectopy, hemodynamic stress and sleepiness and may mimic or worsen heart failure. Assessment includes sitting and supine vital capacity, respiratory pressures, peak cough flow and overnight study with CO2 when indicated. Integrated cardiorespiratory physiology is essential for interpreting dyspnea and prognosis.

Noninvasive ventilation, treatment of apneas and cough assistance are prescribed according to respiratory criteria and tolerance. Correcting hypoventilation may improve alertness and reserve but does not normalize the conduction system and does not replace a pacemaker or ICD. Oxygen alone may mask CO2 retention in someone who hypoventilates. Appropriate ventilatory support reduces a major determinant of mortality and perioperative risk.

Anesthesia and sedation expose patients to aspiration, prolonged hypoventilation, excessive response to sedatives and opioids, difficult extubation and arrhythmias. Before the procedure, ECG, function, device, vital capacity, cough and swallowing are reviewed, with proportionate monitoring and postoperative support planned. Significant cases are not appropriate for hurried discharge after sedation. Perioperative planning should begin before fasting and involve the neuromuscular center.

Succinylcholine, shivering, mechanical stimulation and hypothermia may provoke myotonic contractions and complicate ventilation or surgery. Myotonic dystrophy does not in itself equal proven susceptibility to malignant hyperthermia, but still requires a specific anesthetic technique and a prepared environment. The device is managed according to type, dependency, electrocautery and operative site. Perioperative myotonia is distinct from malignant hyperthermia and should not be confused with it.

Mexiletine may reduce myotonia but blocks the sodium channel and should be preceded by ECG and conduction assessment; a cardiologist is involved if abnormalities or symptoms are present. Flecainide, antidepressants, antipsychotics, macrolides and other drugs may also alter QRS, QT or rate. No static list can replace checking interactions and electrolytes. Cardiology medication review is required with every relevant new prescription.

Pregnancy, family, physical activity and prognosis

A woman with DM1 or DM2 is assessed before conception for conduction, rhythm, ventricular function, respiratory capacity and medications. Pregnancy increases volume and ventilatory demand and may unmask arrhythmias or failure; monitoring is intensified according to phenotype rather than an identical schedule for everyone. Delivery requires obstetric, cardiology, anesthetic and neonatal coordination. Neuromuscular cardio-obstetrics reduces the risk of isolated decisions during an emergency.

In DM1, reproductive counseling should explain autosomal dominant 50 percent transmission, expansion instability and the risk of congenital disease, particularly with maternal transmission of expanded alleles. Prenatal and preimplantation diagnosis are discussed according to preferences and regulations without directive pressure. DM2 shares the 50 percent Mendelian risk but not a reliable prediction of severity from expansion size. Informed reproductive choice distinguishes probability of inheriting the allele from clinical severity.

A confirmed familial expansion permits cascade testing, but in DM1 and DM2 the expansion is sought rather than an ordinary point variant on a panel. Relatives carrying the expansion enter cardiology surveillance even if asymptomatic; those who did not inherit the familial expansion do not need disease-specific genetic follow-up. In minors with DM1, testing may have medical utility because of pediatric manifestations, while timing and consent require genetics expertise. Targeted family screening identifies cardiac disease before block becomes symptomatic.

Gradually prescribed aerobic and strength activity may support functional capacity, metabolism and quality of life. Before intense exercise or competitive sport, syncope, ECG, monitoring, function, chronotropic response, respiration and devices are assessed; uncontrolled arrhythmias or unstable conduction require treatment and reassessment. Exercise testing may clarify capacity and rhythm but does not exclude nocturnal blocks. Individual exercise prescription replaces generalized prohibition and sedentary behavior.

Prognosis depends on age at onset, respiratory phenotype, swallowing, mobility, conduction, arrhythmias and myocardial function. In DM1, respiratory failure and cardiac causes are major determinants of mortality; in DM2, data are fewer and do not permit absolute reassurance. A pacemaker modifies bradyarrhythmic risk but not systemic natural history, while an ICD terminates some tachyarrhythmias without preventing embolism or respiratory failure. Component-based prognosis makes it possible to explain the benefits and limitations of each intervention.

Follow-up should assign clear responsibilities: who reviews the ECG, who checks device transmissions, who schedules imaging and who monitors ventilation. Apathy, cognitive difficulty and avoidance may reduce adherence and require reminders, consensual family involvement and pathways concentrated on the same day. Failure to attend a visit is a clinical signal, not simply disinterest. Adapted continuity of care is a concrete preventive measure.

Prospective registries, prolonged monitoring and natural-history studies are improving risk definition, while antisense therapies and other strategies against toxic RNA are under development. Until they demonstrate clinical cardiac benefit, they should not replace surveillance and phenotype treatment. The priority remains recognizing electrical and respiratory progression before an irreversible event. Contemporary care combines available prevention with rigorous access to research.