Comparison of DMD and BMD Groups
The DMD and BMD groups had a similar age at cardiomyopathy diagnosis (14.4±2.3 vs. 14.6±2.0 years) and rates of CHF at diagnosis (30% vs. 33%). ().
Demographics, Medical History and Clinical Characteristics at the Diagnosis of Cardiomyopathy by Etiologic Classification in 455 Patients with Dilated Cardiomyopathy.
At the time of cardiomyopathy diagnosis, the BMD group had larger LV end-diastolic and LV end-systolic dimension Z-scores than did the DMD group (), but similar LV fractional shortening (FS) and LV wall thickness. Although only qualitative echocardiographic data were available for 40 of the 143 children with DMD or BMD, the BMD group was more likely to have at least moderate mitral regurgitation (50% vs. 18% in DMD group, linear trend P=.05). Similarly, moderate tricuspid regurgitation was more common in the BMD group (17% vs. 0% in DMD group, linear trend P=.004). Forty-one BMD and DMD cases had follow-up echocardiograms. At 2 years following cardiomyopathy diagnosis, only LV end-diastolic dimension (EDD) reflected marked deterioration in the DMD+BMD group (mean±SD change in Z-score, 1.39±1.81, P=.003). All other change scores of the DMD+BMD group were in the direction of deterioration (), but did not achieve significance in this small sample.
Echocardiographic Characteristics at the Diagnosis of Cardiomyopathy by Etiologic Classification in 414 Patients with Dilated Cardiomyopathy and Echocardiographic Data.
Mean (±Standard Deviation) Change in Echocardiographic Characteristics from Diagnosis of Cardiomyopathy to 2 Years After Diagnosis
Time to Death or Transplant after Cardiomyopathy Diagnosis
Forty-seven cases with DMD and none with BMD died (median follow-up time of non-transplanted survivors, 3.3 years). In the DMD group, 25% and 50% died within 2.4 years and 5.5 years after cardiomyopathy was diagnosed, respectively (; log-rank P=.06). The striking difference in survival but lack of statistical significance was probably due to the shorter follow-up time of the BMD cases, many of whom underwent heart transplantation.
Survival from time of diagnosis of cardiomyopathy, by diagnosis (P=.06).
Six of the 15 BMD cases but none of the 128 in the DMD group underwent heart transplantation. In the BMD group, 25% underwent heart transplantation within 5 months after cardiomyopathy diagnosis (). Because the DMD and BMD groups experienced roughly the same proportion of events overall, there was no difference in the composite endpoint (death or transplant) between the two groups (; log-rank P=.25), but weighting earlier differences more heavily there was longer event-free survival in the DMD group (Gehan-Wilcoxon test, P=.03). The 5-year event-free rates were 55% (95% C.I. 28%–82%) and 57% (95% C. I. 46%–68%) for the children with DMD and BMD, respectively.
Freedom from transplantation following diagnosis of cardiomyopathy, by diagnosis (P<.001).
Freedom from death and transplantation following diagnosis of cardiomyopathy, by diagnosis (log-rank P=.25; and Gehan-Wilcoxon, P=.03).
Cause of Death
Sixty-four percent (30 of 47) of the deaths had a known cause. Three of the 30 deaths with a specified cause (10%) were due to ventricular arrhythmia, with one noted as sudden. Two of 30 were due to cardiogenic shock (7%). Five deaths (17%) were primarily respiratory in nature (two cardiopulmonary arrests secondary to airway obstruction, one pneumonitis, two respiratory failure). Twenty deaths were due to CHF, with respiratory failure noted as a secondary cause in all nine for whom respiratory failure was specifically queried. One of the 20 CHF deaths was also noted to be secondarily due to sepsis, one to liver stasis, and one to renal failure.
The use of digoxin and diuretics was similar for the DMD and BMD groups at cardiomyopathy diagnosis (68% vs. 60%, P=.57). The use of anti-arrhythmics, ACE inhibitors, and calcium channel blockers was less common (3%–38%) and similar in the two groups. No beta-blocker use was documented. Two years after cardiomyopathy diagnosis, 81% of DMD children and 57% of BMD children used digoxin and diuretics (P=.16 for DMD-BMD differences).
Comparison of DMD+BMD with ODCM Children & Adolescents
At presentation, the ODCM group was significantly more likely to have CHF (P<.001) and to receive anti-congestive therapy (P=.006) compared with the DMD+BMD group. The DMD+BMD group had a significantly higher familial incidence of genetic syndromes (defined to include muscular dystrophy) than did the ODCM group (41% vs. 3%, P<.001).
At cardiomyopathy diagnosis, the DMD+BMD group had less dilation than the ODCM group (LVEDD Z-scores, 1.41±1.92 vs. 3.37±2.29, P<.001), less impaired LVFS (median Z-scores −5.20 vs. −7.80, P<.001), and closer-to-normal mean LV mass Z-scores (−0.41 ±1.81 vs. 1.67±2.14, P<.001) (). Median LV posterior wall thickness to EDD ratio was nearly identical for the DMD+BMD and ODCM groups.
LV end-diastolic and systolic dimensions increased over two years in the DMD+BMD group but not in the ODCM group (mean EDD change score 1.39±1.81 vs. −0.22±1.70, P=.002). LVFS did not change in the DMD+BMD group, but improved in the ODCM group (mean Z-score change −0.53±2.79 vs. 1.64±3.76, P=.008).
Time to Death or Transplant after Cardiomyopathy Diagnosis
Survival after cardiomyopathy diagnosis did not differ significantly between the ODCM group and the DMD+BMD group (log-rank P=.08). The 5-year survival rate was 71% (95% C.I. 61%–80%) in the ODCM group () and was 59% in the DMD+BMD group (95% C.I. 49%–70%).
At the time of cardiomyopathy diagnosis, anti-congestive therapy use was significantly higher in the ODCM group than in the DMD+BMD group (80% vs. 67%, P=.006). However, two years after diagnosis, the rates were similar (73% vs. 79%, P=.77). The ODCM group received anti-arrhythmic and ACE inhibition therapy twice as often at the time of cardiomyopathy diagnosis (P=.045 and <.001 respectively) compared with the DMD+BMD group. Calcium channel blockers and beta-blockers were rarely used at the time of diagnosis of cardiomyopathy.