Diastolic function of the left ventricle in children with secondary cardiomyopathy

The structure of cardiac pathology has undergone significant changes in the last decades of the last century. In Ukraine there is a persistent tendency to increase the cardiovascular morbidity of non-rheumatic nature, including secondary cardiomyopathies (CMS). Their prevalence increased from 15.6% in 1994 to 27.79% in 2004.

According to the recommendations of the WHO working group, the International Society and the Federation of Cardiology (1995), cardiomyopathies are myocardial diseases associated with a violation of its functions. Over the past 15 years, a lot of research has been done to clarify the ways of development of myocardial dysfunction and lesions, new methods of research have been introduced. All this formed the conditions for revising the classification of cardiomyopathy. Thus, in 2004, Italian scientists expressed the opinion that the term "cardiac dysfunction" should cover not only a decrease in the contractility of the myocardium and a violation of the diastolic function, but also a violation of the rhythm and the conductive system, a condition of increased arrhythmogenicity. In 2006, the American Heart Association proposed treating cardiomyopathy as a "heterogeneous group of myocardial diseases that are associated with mechanical and / or electrical dysfunction, usually manifested by inadequate hypertrophy or dilated cardiac densities and arise from various factors, mainly genetic ones. Cardiomyopathy can be limited to heart damage or be part of a generalized systemic disorder that leads to the progression of heart failure or cardiovascular death. "

One of the main manifestations of secondary cardiomyopathies are disturbances of repolarization processes on the ECG. The opinions on their interpretation in the literature are ambiguous and contradictory. For example, until recently, it was believed that the syndrome of early ventricular repolarization (CVR) is a variant of the norm. However, in the opinion of many authors, the SDF can be a marker of pathological conditions occurring in the myocardium.

Stable disorders of rhythm and conduction in patients with cardiac pathology in the presence of CRF occur 2-4 times more often and may be accompanied by paroxysms of supraventricular tachycardia. In electrophysiological research, paroxysmal supraventricular rhythm disturbances are induced in 37.9% of practically healthy individuals with CRF.

Even in the experimental works of E. Son-nenblick, E. Braunwald, F. 3. Meerson, the joint contribution of systolic and diastolic dysfunctions to the development of heart failure was proved, but the prevailing role of systolic dysfunction in the development of heart failure was subsequently revised. It is known that a decrease in contractility and a small fraction of left ventricular ejection (LV) do not always determine the degree of decompensation, tolerance to physical exertion and prognosis in patients with cardiovascular pathology.

It has now been proven that diastolic dysfunction of the myocardium usually precedes a decrease in pumping function of the LV and can lead to the appearance of signs and symptoms of chronic heart failure in adults with cardiac pathology.

Given that a number of cardiovascular diseases begins in childhood, the study of diastolic myocardial function in children with the most common pathology - secondary cardiomyopathy - is an important task. At the same time in the scientific literature there are only single publications that characterize the relaxation properties of the myocardium in children with secondary cardiomyopathy.

The aim of our study was to improve the early diagnosis of complications of secondary cardiomyopathy in children based on the definition of diastolic LV dysfunction.

To evaluate the functional state of the cardiovascular system in patients with secondary cardiomyopathy, 65 children (46 boys and 19 girls, mean age 14.9 ± 0.3 years) were examined. The most common secondary cardiomyopathies were detected against a background of autonomic dysfunction in 44.62 ± 6.2% of children, endocrine pathology in 26.15 ± 5.5%, chronic kidney diseases of the 1st degree in 18.46 ± 4.9 % of children. One of the criteria for inclusion in the examination group was disturbances of repolarization of the ventricular myocardium on the ECG.

In the 1st group (40 children, 22 boys and 18 girls, mean age 14.8 ± 0.4 years) included children with nonspecific disturbances of repolarization processes (NDP) on the ECG as a decrease in amplitude and inversion of the T wave, depression and ascending ST segment relative to the isoline by 2 mm or more, prolongation of the QT interval by 0.05 s or more, respectively, the heart rate. The 2nd group (25 children, 24 boys and 1 girl, mean age 15.1 + 0.4 years) consisted of patients with the EWG on the ECG.

Among the children of the 1st group, CPD was most often recorded against the background of autonomic dysfunction (45.0 ± 8.0%) and metabolic shifts (35.0 ± 7.6%), in particular against the background of type 1 diabetes mellitus (15.0 ± 5.7%). Among the patients of the 2nd group, children with manifestations of autonomic dysfunction (44.0 +10.1%) prevailed, in 20.0 ± 8.2% of the examined SSRI was registered against the background of undifferentiated connective tissue dysplasia and chronic kidney disease of the 1st degree.

Determination of the diastolic function of the heart was performed on the basis of the parameters of the transmittal flow in a pulse-wave doppler echocardiographic study using an ultrasound device "AU3Partner" from the firm "Esaote Biomedica" (Italy). The criteria for inclusion in the study were the absence of mitral regurgitation in children, stenosis of the mitral valve (as factors that alter the diastolic function of the LV), or tachycardia more than 110-120 beats / min.

To assess diastolic LV function, the following parameters were measured: the maximum flow rate in the phase of early diastolic filling of the LV (E, m / s), the flow rate into the phase of late diastolic filling of the LV in atrial systolic (A, m / s), the acceleration time of the flow velocity in the phase of early diastolic filling of the left ventricle (ATE, c), the time of slowing the flow rate into the phase of early diastolic filling (DTe, c), the time of isovolytic LV relaxation (IVRT, c). Based on the obtained values of the velocity and time parameters of the transmitral flow, the ratio of the rates in the phase of early and late diastolic filling of the LV (E / A), the index of myocardial compliance (IPM) was calculated. IPM is the ratio of the time to reach the maximum flow rate and the half-time reduction in the flow rate to the phase of early diastolic filling (ATe / DTe / 2). According to M. Johnson, IPM allows to assess the diastolic stiffness of the myocardium irrespective of the heart rate.

For the normative indices of the diastolic function of the heart, the data obtained in examining the control group of 20 practically healthy children, who did not have cardiac complaints, organic heart diseases, and the systolic function indices did not differ from normative ones, were accepted.

When analyzing the transmittal flow parameters, diastolic LV dysfunction was recorded in 78.1 ± 7.2% of the examined children of the 1st group with nonspecific CPD. Among the children of the 2nd group with SDHD diastolic LV dysfunction was recorded in 65.0 + 11.6% of patients. A high incidence of diastolic dysfunction in those examined may be due to metabolic disorders in the myocardium in children with type 1 diabetes mellitus or manifestations of hypersympathicotonia in patients with autonomic dysfunction.

We have identified restrictive and pseudonormal types of LV diastolic dysfunction (figure). There were no significant differences in the type of diastolic LV disturbances in the children of the 1st and 2nd groups. However, it should be noted that the most unfavorable restrictive type of diastolic LV dysfunction was more often detected among the children of the 1st group and was accompanied by a decrease in the contractile function of the heart (50.0% of the examined, p <0.05); mild hypertrophy of the LV wall (75.0% of the examined, p <0.05), which could indicate the duration or strength of the pathological process.

A pseudo normal type of diastolic LV dysfunction was more often observed in children with chronic somatic pathology (type 1 diabetes, hypothalamic pubertal syndrome, dysmetabolic nephropathy). Diastolic LV dysfunction in the stage of pseudonormalization of the transmittal spectrum is manifested due to the increasing rigidity of LV myocardium and disturbances of its relaxation, which is confirmed by the reliability of differences between the integral indices of the diastolic function.

A high percentage of LV diastolic dysfunction (65.0 + 11.6%) among children of the 2nd group with manifestations of CRH on the ECG does not allow considering it, as was previously thought, a variant of the norm.

In both groups of the examined children, a significant decrease in the rate of early and late filling of the LV is revealed in comparison with similar parameters in the children of the control group (p <0.05 and p <0.01, respectively). There is also a significant increase in the time of acceleration of the diastolic flow of early filling among the children of the 2nd group (0.107 ± 0.005 s, p <0.05), as compared to that of the children of the 1st group and the control group.

In the analysis of IPM, its significant decrease was revealed (IPM = 0.935 ± 0.097, at a rate of 1.24 ± 0.14, /> <0.05) in 14.3% of patients in Group 1 and 8.7% in patients 2 group, which indicates a violation of the elastic properties of the myocardium. Reduction of this indicator was mainly found in children who professionally engage in sports sections and receive prolonged physical activity.

Thus, violations of the repolarization processes, both nonspecific and CPRH, can not be considered an inoffensive ECG phenomenon. Diastolic LV dysfunction is manifested in 75,0 ± 6,06% of the examined children, in particular, in 78,1 ± 7,2% of the children of the 1st group and in 65,0 ± 11,6% of the children of the 2-nd group. Registration of pseudonormal and restrictive spectra of the transmitral LV flow indicates marked disturbances in the diastolic properties of the myocardium with the possible formation of heart failure in patients with secondary cardiomyopathies.

IA Sanin. Diastolic function of the left ventricle in children with secondary cardiomyopathies // International Medical Journal №4 2012

[1], [2], [3], [4], [5], [6], [7], [8],