Early Left Ventricular Structural Myocardial Alterations and Their Relationship with Functional and Electrical Properties of the Heart in Myotonic Dystrophy Type 1

Cardiac magnetic resonance findings and prognosis in type 1 myotonic dystrophy

BACKGROUND

Cardiac involvement is a major determinant of prognosis in type 1 myotonic dystrophy (DM1), but limited information is available about myocardial remodeling and tissue changes. The aim of the study was to investigate cardiac magnetic resonance (CMR) findings and their prognostic significance in DM1.

METHODS

We retrospectively identified all DM1 patients referred from a neurology unit to our CMR laboratory from 2009 to 2020.

RESULTS

Thirty-four patients were included (aged 45 ± 12, 62% male individuals) and compared with 68 age-matched and gender-matched healthy volunteers (43 male individuals, age 48 ± 15 years). At CMR, biventricular and biatrial volumes were significantly smaller (all P < 0.05), as was left ventricular mass (P < 0.001); left ventricular ejection fraction (LVEF) and right ventricular ejection fraction (RVEF) were significantly lower (all P < 0.01). Five (15%) patients had a LVEF less than 50% and four (12%) a RVEF less than 50%. Nine patients (26%) showed mid-wall late gadolinium enhancement (LGE; 5 ± 2% of LVM), and 14 (41%) fatty infiltration. Native T1 in the interventricular septum (1041 ± 53 ms) was higher than for healthy controls (1017 ± 28 ms) and approached the upper reference limit (1089 ms); the extracellular volume was slightly increased (33 ± 2%, reference <30%). Over 3.7 years (2.0-5.0), 6 (18%) patients died of extracardiac causes, 5 (15%) underwent device implantation; 5 of 21 (24%) developed repetitive ventricular ectopic beats (VEBs) on Holter monitoring. LGE mass was associated with the occurrence of repetitive VEBs (P = 0.002). Lower LV stroke volume (P = 0.017), lower RVEF (P = 0.016), a higher LVMi/LVEDVI ratio (P = 0.016), fatty infiltration (P = 0.04), and LGE extent (P < 0.001) were associated with death.

CONCLUSION

DM1 patients display structural and functional cardiac abnormalities, with variable degrees of cardiac muscle hypotrophy, fibrosis, and fatty infiltration. Such changes, as evaluated by CMR, seem to be associated with the development of ventricular arrhythmias and a worse outcome.

Echocardiographic Features of Cardiac Involvement in Myotonic Dystrophy 1: Prevalence and Prognostic Value

Myotonic dystrophy type 1 (DM1) is the most common muscular dystrophy in adults. Cardiac involvement is reported in 80% of cases and includes conduction disturbances, arrhythmias, subclinical diastolic and systolic dysfunction in the early stage of the disease; in contrast, severe ventricular systolic dysfunction occurs in the late stage of the disease. Echocardiography is recommended at the time of diagnosis with periodic revaluation in DM1 patients, regardless of the presence or absence of symptoms. Data regarding the echocardiographic findings in DM1 patients are few and conflicting. This narrative review aimed to describe the echocardiographic features of DM1 patients and their prognostic role as predictors of cardiac arrhythmias and sudden death.

Trajectory of left ventricular ejection fraction in response to therapies in patients with muscular dystrophy

BACKGROUND

Patients with muscular dystrophy (MD) are at elevated risk of serious cardiac complications and clinical assessment is limited due to inherent physical limitations. We assessed the utility of left ventricular ejection fraction (LVEF) derived from transthoracic echocardiogram (TTE) as a prognostic marker for major adverse cardiac events (MACE) in a mixed adult MD cohort.

METHODS

One hundred and sixty-five MD patients (median age: 36 (interquartile range [IQR]: 23.0-49.0) years; 65 [39.4%] females) were enrolled in our prospective cohort study. Diagnoses included dystrophinopathies (n = 42), limb-girdle MD (n = 31), type 1 myotonic dystrophy (n = 71), and facioscapulohumeral MD (n = 21). Left ventricular ejection fraction, ventricular dimensions at end-diastole and end-systole, and serial measures (n = 124; follow-up period: 2.19 [IQR: 1.05-3.32] years) stratified patients for MACE risk.

RESULTS

Cardiomyopathy was diagnosed in 60 (36.4%) patients of the broader cohort (median LVEF: 45.0 [IQR: 35.0-50.0] %). Ninety-eight MACE occurred over the 7-year study period. At baseline, patients with a LVEF < 55.0% had a high risk of MACE (adjusted odds ratio: 8.30; 95% confidence interval [CI]: 3.18-21.7), concordant with the analysis of LV dimensions. Forty-one percent of these patients showed an improvement in LVEF with the optimization of medical and device therapies. Relative to patients with preserved LVEF, patients with reduced LVEF were at an elevated risk of MACE (adjusted hazard ratio [aHR]: 7.21; 95% CI: 1.99-26.1), and improved LVEF resulted in comparable outcomes (aHR: 1.84; 95% CI: .49-6.91) associated with optimization of medical and device therapies. Reduction in QRS duration by CRT therapy was associated with an improvement in LVEF (average improvement: 12.8 [± 2.30] %; p = .04).

CONCLUSIONS

Reduction in LVEF indicates an increased risk of cardiovascular events in patients with MD. Baseline and serial LVEF obtained by TTE can prognosticate patients for MACE and guide clinical management.

Cardiac Pathology in Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM1), the most common muscular dystrophy affecting adults and children, is a multi-systemic disorder affecting skeletal, cardiac, and smooth muscles as well as neurologic, endocrine and other systems. This review is on the cardiac pathology associated with DM1. The heart is one of the primary organs affected in DM1. Cardiac conduction defects are seen in up to 75% of adult DM1 cases and sudden death due to cardiac arrhythmias is one of the most common causes of death in DM1. Unfortunately, the pathogenesis of cardiac manifestations in DM1 is ill defined. In this review, we provide an overview of the history of cardiac studies in DM1, clinical manifestations, and pathology of the heart in DM1. This is followed by a discussion of emerging data about the utility of cardiac magnetic resonance imaging (CMR) as a biomarker for cardiac disease in DM1, and ends with a discussion on models of cardiac RNA toxicity in DM1 and recent clinical guidelines for cardiologic management of individuals with DM1.

Outcome measures frequently used to assess muscle strength in patients with myotonic dystrophy type 1: a systematic review

Measurement of muscle strength is fundamental for the management of patients with myotonic dystrophy type 1 (DM1). Nevertheless, guidance on this topic is somewhat limited due to heterogeneous outcome measures used. This systematic literature review aimed to summarize the most frequent outcome measures to assess muscle strength in patients with DM1. We searched on Pubmed, Web of Science and Embase databases. Observational studies using measures of muscle strength assessment in adult patients with DM1 were included. From a total of 80 included studies, 24 measured cardiac, 45 skeletal and 23 respiratory muscle strength. The most common method and outcome measures used to assess cardiac muscle strength were echocardiography and ejection fraction, for skeletal muscle strength were quantitative muscle test, manual muscle test and maximum isometric torque and medical research council and for respiratory muscle strength were manometry and maximal inspiratory and expiratory pressure. We successfully gathered the more consensual methods and measures to evaluate muscle strength in future clinical studies, particularly to test muscle strength response to treatments in patients with DM1. Future consensus on a set of measures to evaluate muscle strength (core outcome set), is important for these patients.

Association between fragmented QRS complexes and left-ventricular dysfunction in anabolic androgenic steroid users

Background: Anabolic androgen steroid (AS) use has adverse effects on left ventricular functions, such as fibrosis development. Fragmented QRS is an important marker of myocardial fibrosis, while speckle-tracking echocardiographyis a method used to show subclinical left ventricle dysfunction. In this study, we examined the the ability of fQRS + to detect left ventricle fibrosis by speckle tracking echocardiography (STE) in AS users.Methods: The study included a total of 181 healthy athletes. Athletes were divided into two groups as AS users (n = 89) and non-AS users (n = 92). Then, athletes using AS were divided into two groups as fQRS+ (n = 52) and fQRS- (n = 37). In both groups, the arithmetic mean of three images was used to obtain the left ventricle global longitudinal strain (LV-GLS). The E/SRe ratio was also calculated and analysed.Results: There were significant differences between the AS users and non-AS users in terms of, E/SRe (55.7 ± 17.9 vs 50.3 ± 14.8; p = 0.015), LV-GLS (23.1 ± 1.9 vs 24.0 ± 1.7; p = 0.001), and fQRS (18.5% vs 6%; p = 0.005). When subgroup analysis was performed, both LV-GLS and E/SRivr were found to be poor in the fQRS + group. When multiple linear regression analysis was performed, we determined fQRS as an independent predictor for LV-GLS and E/SRivr ratio.Conclusion: In conclusion, our study demonstrated that fQRS is a parameter that can beused to determine left ventricle subclinical systolic and diastolic dysfunction in AS users. It can be used for cessation of drug use, especially in long-term use.

Prevalence of Left Ventricular Systolic Dysfunction in Myotonic Dystrophy Type 1: A Systematic Review

Cardiac involvement is recorded in about 80% of patients affected by myotonic dystrophy type 1 (DM1). The prevalence of cardiac conduction abnormalities and arrhythmias has been well described. Data regarding the prevalence of left ventricle systolic dysfunction (LVSD) and heart failure (HF) are still conflicting. The primary objective of this review was to assess the prevalence of LVSD and HF in DM1. The secondary aim was to examine the association of clinical features with LVSD and to detect predisposing and influencing prognosis factors. A systematic search was developed in MEDLINE, EMBASE, Cochrane Register of Controlled Trials, and Web of Science databases to identify original reports between January 1, 2009, and September 30, 2017, assessing the prevalence of LVSD and HF in populations with DM1. Retrospective and prospective cohort studies and case series describing the prevalence of LVSD, as evaluated by echocardiography, and HF in patients with DM1 were included. Case reports, simple reviews, commentaries and editorials were excluded. Seven studies were identified as eligible, of which 1 was a retrospective population-based cohort study, and 6 were retrospective single-center-based cohort studies. Echocardiographic data concerning LV function were available for 647 of the 876 patients with DM1 who were included in the analysis. The prevalence of LVSD in patients with DM1, defined as LVEF < 55%, was 13.8%, 4.5-fold higher than in general population. Patients with DM1 and LVSD were older, were more likely to be male, had longer baseline atrioventricular and intraventricular conduction-time durations, had higher incidences of atrial arrhythmias, and were more likely to have undergone device implantation. Also, symptomatic HF is more prevalent in patients with DM1 despite their limited levels of physical activity. Further studies are needed to evaluate the prevalence of LVSD and HF in patients with DM1 and to investigate electrocardiographic abnormalities and other clinical features associated with this condition.

Left ventricular longitudinal strain impairment predicts cardiovascular events in asymptomatic type 1 myotonic dystrophy

BACKGROUND

Type 1 myotonic dystrophy (DM1) patients' prognosis is very poor. Up until now, only a few prognostic factors for cardiovascular events have been identified, and they are predictive of end-stage disease. The aim was to assess the prognostic value of global longitudinal strain (GLS) for cardiovascular events in asymptomatic DM1 patients.

METHODS

DM1 patients were included between 2011 and 2015 and followed up until January 2016. Patients underwent a transthoracic echocardiography at inclusion. The primary endpoint was a composite of all-cause mortality, type 2 Mobitz 2 and type 3 atrioventricular block, symptomatic sino-atrial block, HV interval≥70ms at invasive electrophysiology exploration, left ventricular ejection fraction (LVEF) ≤45% and newly developed atrial fibrillation.

RESULTS

Forty-six patients (25 males, mean age 40years old) were included. The primary outcome was reached in 14 patients with a mean follow-up of 38months. GLS of patients who reached the primary endpoint was significantly impaired as compared to those who did not (-15.1 [-16.7; -12.7] vs. -18.2 [-19.2; -16.7] respectively; P=0.001). According to ROC curve analysis, probability of primary outcome occurrence was significantly greater in patients with GLS values≥-17.2% (P=0.001). On multivariate analysis, PR electrocardiogram interval and GLS remained significantly and independently associated with the primary endpoint [hazard ratio (HR) 1.03, 95% confidence interval (CI) 1.01-1.04, P=0.006 for PR interval; HR 1.4, 95% CI 1.1-1.7, P=0.002 for GLS] while LVEF alone was not.

CONCLUSION

Left ventricular GLS is a powerful marker to predict cardiovascular events in asymptomatic DM1 patients, independently of LVEF.

Myotonic dystrophy and the heart: A systematic review of evaluation and management

Myotonic dystrophy (MD) is a multisystem, autosomal dominant disorder best known for its skeletal muscle manifestations. Cardiac manifestations arise as a result of myocardial fatty infiltration, degeneration and fibrosis and present most commonly as arrhythmias or conduction disturbances. Guidelines regarding the optimal cardiac management of patients with MD are lacking. The present article provides a summary of the pathophysiology of cardiac problems in patients with MD and provides a practical approach to contemporary cardiac monitoring and management of these patients with a focus on the prevention of complications related to conduction disturbances and arrhythmias.

METHODS

A literature search was performed using PubMed and Medline. The keywords used in the search included "myotonic dystrophy", "cardiac manifestations", "heart", "arrhythmia", "pacemaker" and "defibrillator", all terms were used in combination. In addition, "myotonic dystrophy" was searched in conjunction with "electrophysiology", "electrocardiogram", "echocardiograph", "signal averaged electrocardiograph", "magnetic resonance imaging" and "exercise stress testing". The titles of all the articles revealed by the search were screened for relevance. The abstracts of relevant titles were read and those articles which concerned the cardiac manifestations of myotonic dystrophy or the investigation and management of cardiac manifestations underwent a full manuscript review.

Assessment of cardiac involvement in myotonic muscular dystrophy by T1 mapping on magnetic resonance imaging

BACKGROUND

Patients with myotonic muscular dystrophy (DM) are at risk for atrioventricular block and left ventricular (LV) dysfunction. Noninvasive detection of diffuse myocardial fibrosis may improve disease management in this population.

OBJECTIVE

To define functional and postcontrast myocardial T1 time cardiac magnetic resonance characteristics in patients with DM.

METHODS

Thirty-three patients with DM (24 with type 1 and 9 with type 2) and 13 healthy volunteers underwent cardiac magnetic resonance for the assessment of LV indices and the evaluation of diffuse myocardial fibrosis by T1 mapping. The association of myocardial T1 time with electrocardiogram abnormalities and LV indices was examined among patients with DM.

RESULTS

Patients with DM had lower end-diastolic volume index (68.9 mL/m(2) vs 60.3 mL/m(2); P = .045) and cardiac index (2.7 L/min/m(2) vs 2.33 L/min/m(2); P = .005) and shorter myocardial T1 time (394.5 ms vs 441.4 ms; P < .0001) than did control subjects. Among patients with DM, there was a positive association between higher T1 time and LV mass index (2.2 ms longer per g/m(2); P = .006), LV end-diastolic volume index (1.3 ms longer per mL/m(2); P = .026), filtered QRS duration (1.2 ms longer per unit; P = .005), and low-amplitude (<40 mcV) late-potential duration (0.9 ms longer per unit; P = .01). Using multivariate random effects regression, each 10-ms increase in myocardial T1 time of patients with type 1 DM was independently associated with 1.3-ms increase in longitudinal PR and QRS intervals during follow-up.

CONCLUSIONS

DM is associated with structural alterations on cardiac magnetic resonance. Postcontrast myocardial T1 time was shorter in patients with DM than in controls, likely reflecting the presence of diffuse myocardial fibrosis.

Increased myocardial fibrosis and left ventricular dysfunction in Cushing's syndrome

OBJECTIVE

Active Cushing's syndrome (CS) is associated with cardiomyopathy, characterized by myocardial structural, and ultrastructural abnormalities. The extent of myocardial fibrosis in patients with CS has not been previously evaluated. Therefore, the objective of this study was to assess myocardial fibrosis in CS patients, its relationship with left ventricular (LV) hypertrophy and function, and its reversibility after surgical treatment.

DESIGN AND METHODS

Fifteen consecutive CS patients (41±12 years) were studied together with 30 hypertensive (HT) patients (matched for LV hypertrophy) and 30 healthy subjects. Echocardiography was performed in all patients including i) LV systolic function assessment by conventional measures and by speckle tracking-derived global longitudinal strain, ii) LV diastolic function assessment using E/E', and iii) myocardial fibrosis assessment using calibrated integrated backscatter (IBS). Echocardiography was repeated after normalization of cortisol secretion (14±3 months).

RESULTS

CS patients showed the highest value of calibrated IBS (-15.1±2.5  dB) compared with HT patients (-20.0±2.6  dB, P<0.01) and controls (-23.8±2.4  dB, P<0.01), indicating increased myocardial fibrosis independent of LV hypertrophy. Moreover, calibrated IBS in CS patients was significantly related to both diastolic function (E/E', r=0.79, P<0.01) and systolic function (global longitudinal strain, r=0.60, P=0.02). After successful surgical treatment, calibrated IBS normalized (-21.0±3.8 vs -15.1±2.5  dB, P<0.01), suggestive of regression of myocardial fibrosis.

CONCLUSIONS

Patients with CS have increased myocardial fibrosis, which is related to LV systolic and diastolic dysfunction. Successful treatment of CS normalizes the extent of myocardial fibrosis. Therefore, myocardial fibrosis appears to be an important factor in the development and potential regression of CS cardiomyopathy.

Increased temporal dispersion of myocardial repolarization in myotonic dystrophy type 1: beyond the cardiac conduction system

BACKGROUND AND OBJECTIVES

The most frequently mechanism underlying sudden cardiac death in myotonic dystrophy type 1 (DM1) is bradyarrhythmias due to cardiac conduction abnormalities. However the risk of ventricular tachyarrhythmias remains a concern in clinical management as well as in its determinant. We therefore assessed autonomic nervous system activity aiming to disclose differences in the QT variability index (QTVI)-a marker of temporal myocardial repolarization lability-between DM1 patients and healthy controls. We also investigated the possible differences within DM1 patients by subdividing them according either to the presence of first degree atrioventricular block (1st AVB) or to the cytosine-thymine-guanine (CTG) repeat expansion size.

METHODS

Sixty-two DM1 patients and 20 healthy subjects underwent neurological and cardiological examinations, the latter including ECG, echocardiography and 24-hour Holter monitoring. All underwent a 5-minute ECG recording to assess heart rate variability power spectral components, and the QTVI values.

RESULTS

Power spectral data, namely total power, low frequency power and high frequency power, were lower, whereas QTVI values were higher in DM1 patients than in controls (p<.0001). Higher QTVI values were found in DM1 subgroups with 1st AVB (p=.009) and more than 500 CTG repeat (p=.014) with respect to DM1 patients without 1st AVB and CTG<500. Spectral data did not significantly differ. At multivariable analysis, QTVI and age were independently associated with PR interval and CTG repeat.

CONCLUSIONS

The increased values of QTVI argue in favour of an important heart involvement extending beyond the conduction system. Whether QTVI could be useful in predicting clinical course of DM1 clearly requires larger prospective studies.

Exercise-induced left ventricular systolic dysfunction in women heterozygous for dystrophinopathy

BACKGROUND

Mutations in the X-linked gene encoding dystrophin cause skeletal and cardiac muscle diseases in men. Female "carriers" also can develop overt disease. The purpose of this study was to ascertain the prevalence of cardiac contractile abnormalities in dystrophinopathy carriers.

METHODS

Twenty-four dystrophinopathy heterozygotes and 24 normal women each underwent standard exercise stress echocardiography.

RESULTS

Heterozygotes demonstrated mildly lower left ventricular ejection fractions (LVEFs) at rest compared with controls (0.56 + or - 0.10 vs 0.62 + or - 0.07, P = .02). After exercise, the mean LVEF fell to 0.53 + or - 0.14 in heterozygotes but rose to 0.73 + or - 0.07 in controls (P < .001). Twenty-one of 24 dystrophinopathy heterozygotes demonstrated > or = 1 of the following: abnormal resting LVEF, abnormal LVEF response to exercise, or exercise-induced wall motion abnormality.

CONCLUSIONS

Women heterozygous for dystrophinopathy demonstrate significant left ventricular systolic dysfunction, which is unmasked by exercise. This finding has mechanistic implications for both inherited and acquired cardiac disease states.

Early myocardial dysfunction after chronic use of anabolic androgenic steroids: combined pulsed-wave tissue Doppler imaging and ultrasonic integrated backscatter cyclic variations analysis

BACKGROUND

The chronic consumption of androgenic anabolic steroids (AAS) has shown to cause subclinical impairment of myocardial function. Pulsed-wave Doppler tissue imaging (PWDTI) detects early regional alterations of ventricular function, whereas integrated backscatter cyclic variations (IBScv) are tightly related to the contractile efficiency of the left ventricular wall. The aim of this study was to identify the effects of chronic AAS misuse on myocardial function using both PWDTI and IBScv.

METHODS

Twenty-eight male bodybuilders (11 AAS users, 17 AAS nonusers) and 20 healthy sedentary subjects (controls), matched according to age, were studied. To assess left ventricular function, each subject underwent standard Doppler echocardiography, PWDTI, and IBScv analyses.

RESULTS

Left ventricular mass was significantly higher in AAS users than in AAS nonusers and controls. Global systolic function (assessed by determining the ejection fraction) was similar in all subjects, but isovolumetric relaxation time was significantly higher in AAS users than in controls. On PWDTI analysis, AAS users showed regional systolic and diastolic dysfunction (evaluated by measuring s', e', and a') not detectable in the other two groups. IBScv identified regional systolic impairment only in AAS users at the level of the left ventricular inferior wall.

CONCLUSIONS

The present study confirms that in AAS users, PWDTI and IBScv are effective and reliable noninvasive diagnostic tools for detecting early abnormalities of the systolic and diastolic longitudinal myocardial function, probably related to an increase in myocardial collagen content, interpretable as a repair process against the direct cellular injury produced by AAS.