Congenital heart malformations associated with disproportionate ventricular septal thickening

Asymmetric septal hypertrophy, or ASH, is a genetically determined myocardial disorder that is transmitted as an autosomal dominant trait. ASH is characterized by a disproportionately thickened ventricular septum that contains numerous hypertrophied, bizarrely-shaped and disorganized cardiac muscle cells. Disproportionate hypertrophy of the ventricular septum has also been observed in association with certain congenital cardiac malformations. To determine whether such congenital cardiac malformations are part of the disease spectrum of genetically determined ASH, cardiac pathologic observations were made in eight patients with disproportionate septal thickening (ventricular septal to posterobasal left ventricular free wall thickness ratios of 1.5 to 2.5) and the following three categories of associated lesions: 1) parachute deformity of the mitral valve (occurring either as an isolated lesion or with ventricular septal defect, coarctation of the aorta, supravalvular ring of the left atrium, or double outlet right ventricle); 2) complete interruption of the aortic arch; and 3) ventricular septal defect. The arrangement of cardiac muscle cells in the disproportionately thickened ventricular septum was normal in six of the eight patients; in the other two patients (one with parachute deformity of the mitral valve and one with ventricular septal defect) numerous bundles of hypertrophied cardiac muscle cells were interlaced in a disorganized fashion among more normally arranged bundles of cells. First degree relatives of six of the eight patients were studied by echocardiography and found to have normal ventricular wall thicknesses and septal-free wall ratios. It is concluded that disproportionate ventricular septal thickening may occur in patients with a variety of congenital heart malformations, but that such a finding is not necessarily a manifestation of the disease spectrum of genetically determined ASH.

Identification of congenital malformations of the great arteries in infants by real-time two-dimensional echocardiography

Real-time, two dimensional echocardiography was used to identify great artery relations in 23 infants and small children, including 16 patients with angiography documented transposition of the great arteries, tetralogy of Fallot, or pulmonary aresia. Using this technique, the heart was scanned perpendicular to its long axis at the origin of the great arteries. Great arteries cross-sectioned perpendicular to their long axes appear as circles; when sectioned longitudinally these arteries appeared as elongated sausage-shaped structures. I- patients with normally related great arteries, a curcular structure (aorta) always was positioned posterior to an elongated, sausage-shaped structure (distal right ventricular outflow tract and proximal main pulmonary artery). In transposition of the great arteries, two adjacent circular structures were observed; the anterior circle (aorta) was located to the right, left or directly anterior to the posterior circle (pulmonary artery). In pulmonary atresia or hypoplasis, a large posterior circle (aorta) was associated with an anteriorly positioned structure that was either short and small (atretic right ventricular outflow tract) or elongated with an area of severe narrowing (hypoplastic right ventricular outflow tract). Thus, real-time two-dimensional echocardiography provides a rapid, noninvasive means of accurately identifying congenital malformations of the great arteries in infants and small children and may be a useful adjunct to cardiac catheterization in the diagnosis of cyanotic congenital heart disease.

Prognostic implications of left ventricular function in endomyocardial disease in infants and children

Hemodynamic factors measured at cardiac catheterization in 40 infants and children with chronic endomyocardial disease were analyzed in regard to subsequent clinical condition. The patients were followed for periods ranging from 2 months to 11 years (average 4.3 years) after initial cardiac catheterization. There were no statistically significant differences in left ventricular end-diastolic volume among survivors with no symptoms, survivors with persistent congestive heart failure, and nonsurvivors. Ejection fractions were depressed in about four fifths of patients with chronic endomyocardial disease and were significantly lower in the group of patients who died subsequently. LVEDP in patients who did not survive was significantly higher than in asymptomatic survivors, but there was too much overlapping of individual values to be of prognostic value. Left ventricular pressure-volume loops appeared to offer an improved, although more tedious, method of assessing LV function. In addition to offering information on LVEDV, LVEDP, and EjF, LV stroke work may easily be estimated from pressure-volume loops. There was generally good correlation between hemodynamic status assessed from pressure-volume loops and subsequent clinical outcome.

Ultrastructural features of degenerated cardiac muscle cells in patients with cardiac hypertrophy

Degenerated cardiac muscle cells were present in hypertrophied ventricular muscle obtained at operation from 12 (38%) of 32 patients with asymmetric septal hypertrophy (hypertrophic cardiomyopathy) or aortic valvular disease. Degenerated cells demonstrated a wide variety of ultrastructural alterations. Mildly altered cells were normal-sized or hypertrophied and showed focal changes, including preferential loss of thick (myosin) filaments, streaming and clumping of Z band material, and proliferation of the tubules of sarcoplasmic reticulum. Moderately and severely degenerated cells were normal-sized or atrophic and showed additional changes, including extensive myofibrillar lysis and loss of T tubules. The appearance of the most severely degenerated cells usually reflected the cytoplasmic organelle (sarcoplasmic reticulum, glycogen, or mitochondria) which underwent proliferation and filled the myofibril-free areas of these cells. Moderately and severely degenerated cells were present in areas of fibrosis, had thickened basement membranes, and had lost their intercellular connections. These observations suggest that degenerated cardiac muscle cells have poor contractile function and may be responsible for impaired cardiac performance in some patients with chronic ventricular hypertrophy.

Myocardial ultrastructure in patients with chronic aortic valve disease

Light and electron microscopic observations were made on left ventricular myocardium removed at operation from 16 patients with chronic aortic valve disease. In all 16 patients most cardiac muscle cells were hypertrophid, and surrounded by small amounts of fibrous tissue. In two of the six patients with pure aortic regurgitation and in four of the five patients with combined aortic stenosis and regurgitation, cardiac muscle cells with evidence of degeneration were present in addition to hypertrophied, nondegenerated cells. Degenerated cardiac muscle cells were not observed in the six patients with predominant aortic stenosis. Cardiac muscle cells with mild degeneration showed focal myofibrillar lysis, with preferential loss of thick myofilaments, and focal proliferation of tubules of sarcoplasmic reticulum. More severely degenerated muscle cells showed a marked decrease in the numbers of myofibrils and T tubules and proliferation of sarcoplasmic reticulum or mitochondria, or both. Severly degenerated cells usually were present in areas of marked fibrosis, often were atrophic, had thickened basement membranes and had lost their intercellular connections. These findings suggest that degenerated cardiac muscle cells have poor contractile function and may be responsible for impaired cardiac performance in some patients with chronic aortic valve disease.

Comparative left ventricular dimensions in trained athletes

Little is known about the structure of athletes' hearts of anatomic variations associated with training. Echocardiograms of 56 active athletes were obtained. Mean left ventricular end-diastolic volume and mass were increased in athletes involved in isotonic exercise, such as swimming (181 ml, 308 g) and running (160 ml, 302 g), compared with controls (101 ml, 211 g); wall thickness was normal (less than or equal to 12 mm). Athletes involved in isometric exercise, such as werstling and shot putting, had normal mean left ventricular end-diastolic volumes (110 ml, 122 ml), but increased wall thickness (13 to 14 mm) and mass (330 g, 348 g). Thus, athletes participating in isotonic exercise had increased left ventricular mass with cardiac changes similar to those in chronic volume overloads. Athletes participating in isometric exercise had increased left ventricular mass with cardiac changes similar to those in chronic pressure loads, recognizing greater left ventricular mass and volume in well-trained athletes aids in interpreting values deviating from "normal" limits.

The nuclear membranes in hypertrophied human cardiac muscle cells

Nuclear membranes of cardiac muscle cells were studied in 134 patients with cardiac hypertrophy of various causes. Abnormalities observed consisted of: a) increased foldings and convolutions; b) nuclear pseudoinclusions formed by cytoplasmic organelles protruding into saccular invaginations of the nuclear membranes, and c) intranuclear tubules. The increased foldings and convolutions of the nuclear membranes and the nuclear pseudoinclusions appear to result from synthesis of nuclear membranes in excess of that needed to accommodate the increase in nuclear volume which occurs in hypertrophy. Intranuclear tubules were found in 6 patients and consisted of tubular invaginations, 400 to 650 A in diameter, of the inner nuclear membranes into the nucleoplasm. Some of these tubules were straight and cylindrical, and were associated with a peripheral layer of marginated chromatin; others were not associated with chromatin, appeared coiled and followed irregular courses. Intranuclear tubules in cardiac muscle cells probably represent an extreme cellular response to the stimulus of hypertrophy.

Electrocardiographic evidence of left ventricular hypertrophy in otherwise normal children. Clarification by echocardiography

Eleven apparently normal children whose electrocardiograms demonstrated greatly increased precordial QRS voltages suggestive of left ventricular hypertrophy were studied by echocardiography to determine whether this finding represented an early manifestation of cardiac disease. Echocardiographic measurements of the thickness of the ventricular septum and of the left ventricular posterobasal wall were normal in all 11 subjects when compared with normal values for age. Also within normal limits were left ventricular, left atrial and aortic root internal diameters, left ventricular mass and the motion and structure of the anterior and posterior mitral valve leaflets. We conclude: (1) These children probably have normal hearts; (2) increased precordial QRS voltage in children and adolescents, in the absence of other abnormalities, is an unreliable indicator of left ventricular hypertrophy; and (3) echocardiography is a powerful diagnostic test in determining the significance of abnormal electrocardiograms suggestive of left venticular hypertrophy.

Asymmetric septal hypertrophy (ASH) in infancy

Clinical and pathologic observations were made in four infants who died with asymmetric septal hypertrophy in the first five months of life. One of these infants was stillborn and the other three were aged 1½ months, 4½ months, and 5 months at the time of their deaths. The three live-born infants demonstrated severe congestive heart failure and cardiac enlargement. The clinical features present in these three infants during life suggested a variety of other congenital cardiac malformations, including congenital mitral regurgitation, pulmonary stenosis, and endocardial fibroelastosis. In each of the four infants the ventricular septum was markedly hypertrophied and was thicker than the postero-basal left ventricular wall; septal to postero-basal free wall thickness ratios ranged from 1.8 to 2.6. Moreover, the septum of each infant contained a disordered arrangement of hypertrophied cardiac muscle cells. In three of the infants the myocardial cellular abnormalities were less marked in the left ventricular free walls than in the ventricular septum. In the fourth infant disorganized cardiac muscle cells were distributed widely in both the ventricular septum and left ventricular free wall; the clinical findings suggested the absence of left ventricular outflow obstruction in this infant. Asymmetric septal hypertrophy was documented in one first degree relative of each infant. It is concluded that asymmetric septal hypertrophy is a genetically transmitted disease that may present clinically in infancy and lead to infant death. Furthermore, the characteristic pathologic feature of asymmetric septal hypertrophy in adults, a disproportionately thickened ventricular septum containing numerous hypertrophied and disorganized cardiac muscle cells, can be present at birth.

Differences in distribution of myocardial abnormalities in patients with obstructive and nonobstructive asymmetric septal hypertrophy (ASH). Light and electron microscopic findings

Previous studies have shown that abnormal cellular morphology is present in the ventricular septum of patients with asymmetric septal hypertrophy (ASH). The present study was undertaken to determine whether these morphologic abnormalities are limited to the ventricular septum of patients with ASH or are more diffusely distributed throughout the heart, and whether different patterns of distribution of the cellular abnormalities exist in patients with and patients without left ventricular outflow obstruction. Myocardium was obtained at operation or necropsy from 22 patients, including 14 with obstructive and eight with non-obstructive ASH, and studied by both light and electron microscopy. Many hypertrophied, bizarrely shaped, and abnormally arranged cardiac muscle cells, presumably a morphologic manifestation of the genetically transmitted myocardial defect in ASH, were present in the ventricular septum of all patients. In patients with obstructive ASH, these abnormalities were either absent or rarely found in muscle from the left and right ventricular free walls. This observation suggests that functional limitation in these patients is due largely to left ventricular outflow obstruction. In contrast, numerous disorganized cells were extensively distributed in the left and right ventricular feee walls from seven of eight symptomatic patients with non-obstructive ASH, suggesting that these abnormalities probably contribute importantly to functional impairment in such patients.

Intracytoplasmic junctions in cardiac muscle cells

JUNCTIONAL STRUCTURES FORMED BY TWO PARTS OF THE PLASMA MEMBRANE OF THE SAME CARDIAC MUSCLE CELL WERE OBSERVED IN VENTRICULAR MYOCARDIUM OF: a) patients with neoplasms, aortic valvular disease or idiopathic hypertrophic subaortic stenosis and b) dogs subjected to prolonged normothermic anoxic cardiac arrest. Most of these structures had features of desmosomes; other, more complex structures had components with features of desmosomes, fasciae adherentes and nexuses, and, therefore, resembled intercalated discs. These intracytoplasmic junctions were localized to: a) the peripheral cytoplasm at the sides or ends of cells, b) narrow invaginations of plasma membranes, c) narrow zones of deep, broad plasmalemmal invaginations and d) narrow branches of T tubules. In patients with idiopathic hypertrophic subaortic stenosis or aortic valvular disease and in the dogs subjected to anoxic cardiac arrest, intracytoplasmic junctions were observed in hypertrophied or degenerated muscle cells which were located in areas of fibrosis and which showed loss of contact with adjacent cells. In patients with neoplasms, intracyto-plasmic junctions were found in degenerated cells which were located in areas of interstitial edema and which also showed loss of contact with adjacent cells. Our observations suggest that remodeling of cell surfaces following loss of intercellular contact is the most likely mechanism of formation of intracytoplasmic junctions.

The development of the semilunar valves in the human heart

The development of human semilunar valves was studied in a range of specimens including embryos before the appearance of cellular semilunar valves at stage 17 and hearts after the attainment of mature fibroelastic valvular structure, which occurs around the time of birth. The valves develop by modification of endocardial cushion material at the downstream end of the cardiac tube and appear to grow at the margins, probably by cellular proliferation into a stagnant zone caused by boundary layer separation of blood flow. The flat endothelium on the ventricular aspect and the cuboidal endothelium on the arterial aspect of the valves correlate, respectively, with expected high and low shear forces produced by surface blood flow. Development of an aorta and pulmonary trunk with tricuspid semilunar valves appears to be contingent on the appearance of separate entwined ventricular ejection streams. The later fibroelastic phases of semilunar valve development show progressive increase in elastic and collagenous fibers, at sites which appear to be subjected, respectively, to fluctuating and static tensions.

Unusual evolution of acquired infundibular stenosis in patients with ventricular septal defect. Clinical and morphologic observations

Hemodynamic and cardiac morphologic observations were made on two patients with ventricular septal defect who showed unusual evolution of obstruction to right ventricular outflow. Both patients developed progressive infundibular stenosis, one in the presence of a spontaneously closing ventricular septal defect and the other after operative closure of the defect. Light and electron microscopic examination of resected infundibular muscle revealed hypertrophy and abnormal shapes and arrangements of cardiac muscle cells. These abnormalities resembled those found in left ventricular outflow tract muscle of patients with idiopathic hypertrophic subaortic stenosis. It is suggested that the patterns of distribution and growth of these abnormal cells in the right ventricular outflow tract may lead to localized hypertrophy and to development of progressive infundibular obstruction in some patients with ventricular septal defect.

Postoperative assessment of patients with ventricular septal defect and pulmonary hypertension. Response to intense upright exercise

Circulatory function of patients with operatively closed ventricular septal defect and preoperative pulmonary arterial hypertension was evaluated in 11 asymptomatic subjects at rest and during intense treadmill exercise three to 15 years after operation. The pulmonary-to-systemic resistance ratio was normal or mildly to moderately elevated preoperatively. Postoperative mean pulmonary arterial pressure at the time of study was normal or mildly elevated at rest in 10 patients and moderately elevated in one (40 mm Hg). During intense upright exercise sufficient to lower pulmonary arterial oxygen saturation to 30%, cardiac output was below the normal range in five patients. Each of these patients had been operated upon after 10 years of age. The magnitude of the postoperative abnormality in cardiac output response to exercise was directly related to age at operation. Two of the five patients with impaired cardiac output response and two other patients manifested an abnormally elevated mean pulmonary arterial pressure during intense exercise. There was a positive correlation between pulmonary arterial pressure during intense exercise and age at operation. These results indicate that late postoperative cardiovascular function may be abnormal in patients with ventricular septal defect and preoperative pulmonary arterial hypertension, and that these abnormalities appear to be related to age at operation. Since all patients were asymptomatic, the long-term clinical significance of these hemodynamic abnormalities remains to be determined.

Significance of multiple intercalated discs in hypertrophied human myocardium

Multiple intercalated discs were frequently observed in muscle cells from patients with cardiac hypertrophy of various causes. Evidence is presented that these structures are the intercellular junctions of lateral processes of muscle cells. The sizes and shapes of these processes showed marked variations, depending in part on the plane of sectioning. It is postulated that lateral processes develop in certain cells which have side-to-side intercellular junctions with adjacent cells, and that localized mechanical tensions induce their growth. These tensions are due to shearing forces exerted at side-to-side junctions when contraction occurs at different rates or magnitudes in adjacent cells. These forces lead to asymmetric and complementary growth of sarcomeres along the two sides of the lateral junctions, to reorientation of these junctions and to the eventual formation of lateral processes.