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Left ventricular remodeling, mechanics, and tissue characterization in congenital aortic stenosis
Giuseppe Pacileo1, Paolo Calabrò, Giuseppe Limongelli
1Pediatric Cardiology Division, 2 Degrees University, Monaldi Hospital. gpacile@tin.it
Insights
Children with moderate congenital aortic stenosis show increased myocardial collagen despite normal left ventricular (LV) function. LV remodeling is abnormal in only a quarter of patients, with no severe hypertrophy observed.
Area of Science:
- Pediatric Cardiology
- Cardiovascular Research
- Biomedical Engineering
Background:
- Congenital aortic stenosis (AS) imposes pressure overload on the left ventricle (LV).
- The myocardial response to pressure overload is known to be age-dependent.
- Understanding LV remodeling in pediatric AS is crucial for managing cardiovascular health.
Purpose of the Study:
- To investigate left ventricular (LV) remodeling, mechanics, and tissue characteristics in children with moderate congenital aortic stenosis.
- To assess age-dependent myocardial responses in pediatric cardiovascular disease.
- To characterize myocardial fibrosis and contractility in pediatric AS.
Main Methods:
- Echocardiography Doppler was used to study 22 children with moderate AS and 30 controls.
- LV geometry was assessed using sex- and age-specific cut-offs for LV mass/height(2.7) and relative wall thickness.
- Load-independent myocardial contractility and LV diastolic function were evaluated.
- Ultrasonic tissue characterization assessed intramural contractile function and myocardial collagen content via integrated backscatter.
Main Results:
- 81.8% of patients had normal endocardial contractility; all had normal midwall contractility.
- No significant differences in LV diastolic function (mitral flow indexes) were found between groups.
- 72.7% of patients exhibited normal LV geometry; 13.6% showed concentric remodeling, and 13.6% concentric hypertrophy, with no severe hypertrophy.
- Myocardial collagen content, measured by averaged myocardial integrated backscatter, was significantly higher in AS patients compared to controls.
Conclusions:
- Children with moderate congenital aortic stenosis have increased myocardial collagen despite normal LV contractility and diastolic function.
- LV remodeling is abnormal in approximately 25% of these pediatric patients, with no severe hypertrophy.
- The long-term implications of myocardial fibrosis in pediatric AS require further investigation.
Background:
As the response of the myocardium to pressure overload is age-dependent, this study was designed to examine left ventricular (LV) remodeling, mechanics, and tissue characterization in children with moderate congenital aortic stenosis.
Methods:
We studied by echocardiography Doppler 22 patients (mean age 12.4 +/- 5.6 years) with peak and mean transvalvular gradient of 63 +/- 6 and 32 +/- 4 mm Hg, respectively. In addition, 30 age- and body surface area-matched participants with structurally normal hearts were used as a control group. Sex- and age-specific cut-off levels for LV mass/height(2.7) and relative wall thickness were defined to assess LV geometry. As a load-independent index of myocardial contractility, the relation between the rate-corrected velocity of circumferential fiber shortening both at endocardium and midwall, and meridional end-systolic stress was assessed. In addition, LV diastolic function was also evaluated by the mitral flow indexes. Finally, ultrasonic tissue characterization of the LV myocardium was performed by calculating the magnitude of cyclic variation, which reflects the intramural contractile function, and the averaged myocardial intensity of integrated backscatter, which is directly related to the myocardium collagen content.
Results:
The endocardial velocity of circumferential fiber shortening endocardium and meridional end-systolic stress relationship was within the normal range (mean +/- 2SD) in 18 of 22 patients (81.8%), and midwall velocity of circumferential fiber shortening at endocardium and meridional end-systolic stress was normal in all 22 patients. No mitral flow index of LV diastolic function was significantly different between aortic stenosis group and normal participants. In our study population, 16 of 22 patients (72.7%) showed normal LV geometry, 3 (13.6%) had a pattern of concentric remodeling, and 3 (13.6%) concentric hypertrophy. LV hypertrophy was not marked (left ventricular mass index [LVMI] < 51 g/m(2.7)) in any patient. Finally, compared with control participants our study population showed, both at interventricular septum and posterior wall, comparable values of cyclic variation integrated backscatter, but significantly higher values of averaged myocardial integrated backscatter intensity (P <.01).
Conclusions:
In children with moderate congenital aortic stenosis, the total amount of myocardial collagen was increased despite normal LV myocardial contractility and diastolic function. Furthermore, LV remodeling was abnormal in only about a quarter of our patients and none had more than mild hypertrophy. Although the majority of these patients do not have markers now recognized to predict higher risk of cardiovascular events, the long-term significance of myocardial fibrosis and its response to treatment remain to be investigated.