Familial clustering of muscular and cardiac involvement in myotonic dystrophy type 1.

Myotonic dystrophy type 1 (DM1) is associated with both skeletal and cardiac muscle involvement. The aim of the present study was to determine whether familial clustering is observed in the severity of muscle involvement in DM1. We evaluated 51 sibling groups constituting 112 patients with genetically-verified DM1. The siblings were similar to each other in age, cytosine-thymine-guanine (CTG) repeat length, age at disease onset, muscular impairment rating score, and electrocardiographic markers of cardiac conduction disease. After adjusting for the similarities between siblings in age and CTG repeat length, the siblings remained similar to each other in measures of both skeletal and cardiac muscle involvement. These results suggest that factors other than CTG repeat length play a role in the severity and progression of the degenerative skeletal and cardiac muscle disease in DM1.

Prevalence of structural cardiac abnormalities in patients with myotonic dystrophy type I.

BACKGROUND: Myotonic dystrophy type 1 (DM1) is a neurological disorder with known cardiac involvement, including conduction disturbances, arrhythmias, and ventricular dysfunction. We studied which clinical and electrocardiographic features are associated with structural cardiac abnormalities. METHODS: History, physical examination, electrocardiography, and genetic testing were performed on 382 patients with DM1, and cardiac imaging was performed on 100 of these patients. RESULTS: Clinical congestive heart failure was found in 7 of the 382 patients (1.8%). Structural cardiac abnormalities determined with cardiac imaging included left ventricular hypertrophy (19.8%), left ventricular dilatation (18.6%), left ventricular systolic dysfunction (14.0%), mitral valve prolapse (13.7%), regional wall motion abnormality (11.2%), and left atrial dilatation (6.3%). Left ventricular systolic dysfunction was associated with increasing age (relative risk [RR], 1.9 per decade; 95% CI, 1.1-3.2; P =.02), cytosine-thymine-guanine (CTG) repeat length (RR, 2.8 per 500 repeats; 95% CI, 1.3-6.3; P =.01), P-R >200 ms (RR, 14.7; 95% CI, 3.0-73.1; P =.001), and QRS >120 ms (RR, 5.7; 95% CI, 1.5-21.8; P =.01). P-R >200 ms was predictive of regional wall motion abnormalities. QRS >120 ms correlated with regional wall motion abnormalities and left atrial dilatation. CONCLUSIONS: Several clinical and electrocardiographic findings in patients with DM1 are significantly associated with structural heart abnormalities. These results suggest an underlying genetic and pathophysiologic correlate that may lead to cardiac disease in these patients.

Heart rate variability declines with increasing age and CTG repeat length in patients with myotonic dystrophy type 1.

BACKGROUND: Cardiac myopathy manifesting as arrhythmias is common in the neurological disease, myotonic dystrophy type 1 (DM1). The purpose of the present study was to evaluate heart rate variability (HRV) in patients with DM1. METHODS: In a multicenter study, history, ECG, and genetic testing were performed in DM1 patients. RESULTS: In 289 patients in whom the diagnosis of DM1 was confirmed by a prolonged cytosine-thymine-guanine (CTG) repeat length the most common ambulatory ECG abnormality was frequent ventricular ectopy (16.3%). The 24-hour time domain parameters of SDNN (SD of the NN interval) and SDANN (SD of the mean NN, 5-minute interval) declined as age and CTG repeat length increased (SDNN: -8.5 ms per decade, 95% confidence intervals [CI]-12.9, -4.2, -8.7 ms per 500 CTG repeats, CI -15.7, -1.8, r=0.24, P<0.001; SDANN: -8.1 ms per decade, CI -12.4, -3.8, -8.8 ms per 500 CTG repeats, CI -15.7, -1.9, r=0.23, P<0.001). Short-term frequency domain parameters declined with age only (total power: -658 ms2 per decade, CI: -984, -331, r=0.23, P<0.001; low frequency (LF) power -287 ms2 per decade, CI: -397, -178, r=0.30, P<0.001; high frequency (HF) power: -267 ms2 per decade, CI: -386, -144, r=0.25, P<0.001). The LF/HF ratio increased as the patient aged (0.5 per decade, CI: 0.1, 0.9, r=0.13, P=0.03). CONCLUSIONS: In DM1 patients a decline in HRV is observed as the patient ages and CTG repeat length increases.

Attitudes of law enforcement officers regarding automated external defibrillators.

OBJECTIVE: To assess the knowledge and attitudes of law enforcement officers regarding treating out-of-hospital cardiac arrest (OHCA) and using automated external defibrillators (AEDs). METHODS: This was a survey conducted among officers serving Marion County, Indiana. RESULTS: Of 1,130 surveys distributed, 929 (82.2%) were returned. Among these officers, 603 (66.4%) were certified in cardiopulmonary resuscitation (CPR) and 103 (11.3%) had received AED training. Most officers had limited knowledge regarding OHCA. A 100-point knowledge score (mean +/- SD: 31.9 +/- 14.3) was higher in officers who had performed CPR while on duty [35.0, 95% confidence interval (95% CI) = 32.9 to 37.2, p = 0.005] and who were AED-trained (40.8, 95% CI = 38.0 to 43.6, p < 0.001). Of the respondents, 367 (40.1%) believed that AED usage by local law enforcement was needed, and 323 (35.6%) stated that they would feel comfortable using an AED if trained. A 100-point attitude score (mean +/- SD: 32.1 +/- 21.0) was higher in officers who had CPR certification (38.2, 95% CI = 35.6 to 40.8), who had performed CPR while on duty (40.6, 95% CI = 37.7 to 43.5), who were AED-trained (39.5, 95% CI = 35.6 to 43.4), and who had improved OHCA knowledge (+3.8 per 10 points knowledge score, 95% CI = 3.0 to 4.7), p < 0.001, all significant factors. CONCLUSIONS: Limited knowledge and negative attitudes of law enforcement officers regarding their involvement in treating OHCA and using AEDs are commonly present. These factors could result in barriers that negatively impact law enforcement AED programs.

Severity of cardiac conduction involvement and arrhythmias in myotonic dystrophy type 1 correlates with age and CTG repeat length.

INTRODUCTION: Cardiac myopathy manifesting with conduction disturbances and arrhythmias is common in the neurologic disease myotonic dystrophy. We studied whether the severity of cardiac involvement in myotonic dystrophy correlates with the severity of the genetic abnormality cytosine-thymine-guanine (CTG) repeat expansion. METHODS AND RESULTS: History, physical examination, ECG evaluation, and genetic testing were performed in patients with a clinical diagnosis of myotonic dystrophy. In 342 of 385 patients, the diagnosis was confirmed by CTG repeat expansion. In these patients, the muscular disability severity correlated with age and CTG repeat length (r = 0.44, P < 0.001). An arrhythmia diagnosis was present in 19 (5.6%) patients with a likelihood of diagnosis correlating with age (relative risk [RR] 2.2 per decade, 95% confidence intervals [CI] 1.4 to 3.4, P = 0.001) and CTG repeat length (RR 2.9 per 500 repeats, 95% CI 1.5 to 5.4, P = 0.001). ECGs were abnormal in 222 (64.9%) of the patients. Age, CTG repeat length, and male gender were factors found to correlate with ECG conduction abnormalities quantitated by the PR interval (r = 0.43, P < 0.001) and QRS duration (r = 0.32, P < 0.001). A 24-hour ambulatory ECG was abnormal in 95 (29.6%) of 321 recordings. The presence of an abnormality correlated with age (RR 1.5 per decade, 95% CI 1.2 to 1.9, P < 0.001) and CTG repeat length (RR 1.6 per 500 repeats, 95% confidence intervals 1.1 to 2.2, P = 0.01). CONCLUSION: The severity of skeletal and cardiac myopathy in myotonic dystrophy correlates with age and CTG repeat length, suggesting a similar mechanism causing a time-dependent degenerative process.

Use of an insertable loop recorder in a myotonic dystrophy patient.

The case of a 66-year-old woman with myotonic dystrophy is presented. This patient underwent implantation of an insertable loop recorder as a participant in a clinical trial. At 1-month follow-up, interrogation of the insertable loop recorder revealed multiple episodes of wide complex tachycardia. She underwent electrophysiologic study, which revealed moderate His-Purkinje disease, focal atrial tachycardia, monomorphic ventricular tachycardia, and ventricular fibrillation. Successful radiofrequency ablation of the focal atrial tachycardia and implantation of a dual-chamber implantable cardioverter defibrillator was performed.