Sinus tachycardia is common in cases of Duchenne muscular dystrophy (DMD). The authors hypothesized that an elevated heart rate would herald cardiomyopathy onset. A retrospective case-control study was performed with 55 DMD boys and 150 age-matched control boys. The variables were age, heart rate, shortening fraction, and left ventricular end-diastolic dimension. Cardiomyopathy was defined as a shortening fraction less than 28%. The DMD boys had a higher initial heart rate with no baseline echocardiographic evidence of cardiomyopathy. The control subjects showed a statistically significant age-related decline in heart rate (p = 0.001) but not the DMD boys. Cardiomyopathy developed in 17 of the 55 DMD boys over a period of 4.6 ± 1.6 years. The DMD upper and lower heart rate groups were similar in age, follow-up time, and initial shortening fraction, yet cardiomyopathy developed in 14 (42%) of 33 upper quartile boys but only 3 (14%) of 22 lower quartile DMD boys (odds ratio, 6.5 (95% confidence interval, 1.15-18.92; p < 0.05). Compared with the control subjects, the DMD boys had a higher resting heart rate and a lack of age-related heart rate decline. The DMD boys in the upper heart rate quartile were more likely to progress to cardiomyopathy than those in the lower quartiles. This study establishes heart rate elevation as a statistically significant risk factor for cardiomyopathy. Further studies may define heart rate cutoffs for early pharmacologic intervention for incipient cardiomyopathy.

Cardiac manifestations of Duchenne muscular dystrophy (DMD) include progressive cardiac dysfunction and an elevated resting heart rate (HR). We hypothesized this elevated HR reflects autonomic dysfunction that can be identified by heart rate variability (HRV) analyses which will be associated with myocardial fibrosis by cardiac magnetic resonance imaging (cMR). DMD patients (N = 74) and controls (N = 17) had time and frequency domain HRV analyses calculated via Holter monitoring. Cardiac magnetic resonance imaging was performed on DMD cases only. χ (2) test, T test, ANOVA, and logistic regression were used to perform comparisons between groups. A p value of <0.05 was used for statistical significance. DMD cases had higher resting average HR than controls (99.4 ± 8.9, 85.4 + 6.2, p < 0.001). Among HRV variables, decreases were seen in the following: standard deviation of R to R intervals, the percent RR intervals differing by >50 ms from previous RR interval, the root-meansquare of successive differences of RR intervals, the standard deviation of the mean R to R segment (SDANN), low frequency, and high frequency domain, all p values 0.001. Maximum HR and SDANN most significantly associated with positive LGE on cMR (p = 0.008, p = 0.016). DMD cases on beta blocker had an average HR lower than those not on beta blocker (p = 0.009), but with no difference in HRV analysis. DMD patients have reduced HRV and therefore autonomic dysfunction prior to the onset of heart failure which is associated with myocardial fibrosis.

Patients supported with a VAD are at increased risk for sensitization. We aimed to determine risk factors for sensitization as well as the impact of sensitization on post-transplant outcomes. The UNOS database (January 2004-June 2014) was used to identify patients (≤18 yrs) supported with a durable VAD. Rates and degree of sensitization in the VAD cohort were calculated. Post-transplant survival was determined comparing outcomes of sensitized vs. non-sensitized patients. There were 3097 patients included in the study; 19% (n = 579) were bridged with a VAD. Of these, 41.8% were sensitized vs. 29.9% of the patients who were not bridged with a VAD (p < 0.001). VAD was an independent predictor of sensitization (OR 2.05 [1.63-2.57]; p < 0.001). There was no difference in sensitization based on device type (continuous vs. pulsatile flow, p = 0.990). Post-transplant survival rates between the sensitized and non-sensitized VAD patients were not different, including patients with a PRA >50% and VAD patients with a positive DSC (p = 0.280 and 0.160, respectively). In conclusion, pediatric VAD patients are more likely to be sensitized, but there was no difference in sensitization based on device type. In addition, sensitization does not appear to impact outcomes.

Acute myocardial infarction (AMI) is extremely rare in children, and unlike the adult disease, the etiology of the infarction is rarely due to atherosclerotic coronary disease. This unique reported case involved a 15-year-old boy with severe chest pain who presented with an ST-segment-elevation myocardial infarction secondary to in situ thrombus formation in the left anterior descending (LAD) coronary artery. The initial electrocardiogram (ECG) had a Q-wave pattern in V6 and ST depression in the inferior leads with ST-segment elevation in reciprocal leads. The cardiac enzymes and routine labs showed evidence of myocardial damage. The boy was urgently taken to the cardiac catheterization laboratory for percutaneous coronary intervention, where complete occlusion of the LAD was found and successfully stented. Eventually, a peripheral blood smear showed pancytopenia with 38 % hypergranular blast-like cells consistent with acute myeloid leukemia (AML), and chemotherapy with all-transretinoic acid was implemented. This first pediatric case report of an AML-associated AMI emphasizes the benefit resulting from expedient reperfusion of the ischemic myocardium by quick reestablishment of coronary perfusion. It also emphasizes the limitations of existing noninvasive technologies in detecting myocardial viability.