Early systolic closure of the aortic valve in patients with hypertrophic subaortic stenosis and discrete subaortic stenosis. Correlation with preoperative and postoperative hemodynamics

Patterns of motion of the aortic valve were analyzed with echocardiography in 9 patients with discrete subaortic stenosis and 31 patients with idiopathic hypertrophic subaortic stenosis, 22 with and 9 without a resting intraventricular pressure gradient. The intention was to determine whether the early systolic closure of the aortic valve was a sensitive indicator of a resting pressure gradient across the left ventricular outflow tract. All 9 patients with discrete subaortic stenosis and the 22 patients with idiopathic hypertrophic subaortic stenosis with a resting pressure gradient showed early systolic closure of the aortic valve; however, the 9 patients without a resting gradient had normal motion of the aortic valve. Measured values for O-ESC (the interval from the opening point of the aortic valve to the point of early systolic closure of the aortic valve) in 9 patients with discrete subaortic stenosis and in 22 with idiopathic hypertrophic subaortic stenosis averaged 0.05 ± 0.01 (standard deviation) second and 0.14 ± 0.04 second for each group, respectively (P < 0.01). Twelve patients with idiopathic hypertrophic subaortic stenosis underwent operation to alleviate left ventricular outflow tract obstruction. In eight of these patients the resting pressure gradient was completely abolished and early systolic closure of the aortic valve was no longer present. The results indicate that in idiopathic hypertrophic subaortic stenosis, early systolic closure of the aortic valve is recorded only when there is a significant intraventricular pressure gradient at rest. The time of occurrence of early systolic closure differentiated patients with discrete subaortic stenosis from those with idiopathic hypertrophic subaortic stenosis in all observations.     

Echocardiographic assessment of left ventricular outflow tract in d-transposition of the great arteries

The left ventricular outflow tract in 38 patients (aged 0.3 to 13 years) with complete d-transposition of the great arteries, 31 with intraatrial (Mustard) repair, was quantitated with echocardiography, and the findings were correlated with hemodynamic and angiographic data. The left ventricular outflow tract (LVO) was measured on the echocardiogram as an anteroposterior dimension between the closure point on the mitral valve below the pulmonary arterial root (PA) and the left endocardial surface of the interventricular septum. This measurement was expressed as an LVO/PA ratio and on the basis of these measurements three groups were recognized.Group I consisted of 14 patients who had an unobstructed left ventricular outflow tract and no significant pressure differences between the pulmonary artery and left ventricle. In Group II, the 16 patients had evidence of dynamic obstruction and mild to moderate pressure differences between the pulmonary artery and left ventricle, characterized in the echocardiogram by LVO/PA ratios comparable with those of Group I, but with an abnormally prominent early posterior systolic septal bulge in the left ventricular outflow tract, abnormal systolic anterior motion of the mitral valve and coarse fluttering of the pulmonary valve. In Group III the eight patients had anatomically fixed stenosis of the left ventricular outflow tract and severe left ventricular outflow pressure gradients characterized in the echocardiogram by a reduced LVO/PA ratio and fine vibrations of the pulmonary valve. Angiographically discrete or long segmental narrowing of the left ventricular outflow tract correlated well with the echocardiographic data. Echocardiographic measurements of left ventricular posterior wall thickness also correlated well with the severity of left ventricular outflow stenosis in these three groups. The echocardiogram provides clinically useful quantitative and qualitative analysis of the left ventricular outflow tract in patients with complete transposition of the great arteries.     

Masked subaortic stenosis in ostium primum atrial septal defect: Recognition and treatment

Five patients with ostium primum atrial septal defect (ASD) and a cleft mitral valve had no hemodynamic evidence of left ventricular (LV) outflow tract obstruction on preoperative cardiac catheterization. After surgical closure of the ASD and repair of the mitral cleft, all 5 patients manifested subaortic stenosis with pressure gradients ranging from 10 to 120 mm Hg. Postoperative LV angiograms revealed systolic narrowing of the outflow tract, and the same outflow tract dynamics were recognized on reviewing the preoperative angiograms and echocardiograms. Persistence or exaggeration of the characteristic diastolic “goose-neck” deformity during LV systole in atrioventricular canal defects is diagnostic of a potential or actual subaortic obstruction. This diagnostic sign is also readily recognizable by 2-dimensional echocardiography, and when present, the surgeon should be alerted to explore the LV outflow tract because the outflow tract anatomy is not readily apparent at operation aimed solely at closing the ASD and repairing the cleft mitral valve.     

Double outlet right ventricle {S,D,L} with subaortic ventricular septal defect and pulmonary stenosis: Report of six cases

The clinical, hemodynamic, angiocardiographic and pathologic findings are presented in an infrequent but surgically correctable type of double outlet right ventricle. This study is based on six cases, one with autopsy confirmation. In all, the viscera and atria were in situs solitus (S). A ventricular d-loop was present (D). There was l-malposition of the great arteries, the aorta being to the left of, and anterior to, the pulmonary artery (L). Hence, this anomaly may conveniently be represented as double outlet right ventricle {S,D,L}. The ventricular septal defect was subaortic because the aorta was anterior and leftward, adjacent to the ventricular septum. A bilateral conus was present beneath both the aortic and pulmonary valves, preventing any semilunar-atrioventricular fibrous continuity. The subpulmonary conus was poorly expanded, resulting in pulmonary infundibular and valvular (annular) stenosis.The clinical features were those of cyanosis, clubbing and accentuation of the second heart sound in the pulmonary area (related to aortic valve closure). There was a systolic ejection murmur along the upper left sternal border, related to pulmonary outflow tract stenosis. Selective right and left ventricular angiocardiography was diagnostic.Relatively early surgical correction is suggested to minimize the progression of pulmonary infundibular stenosis and to avoid acquired atresia. In this malformation, pulmonary outflow tract reconstruction is more difficult than in tetralogy of Fallot because of the rather posterior location of the pulmonary outflow tract, and because the right coronary artery crosses the stenotic pulmonary outflow tract in front of the pulmonary valve.     

Pre- and postoperative echocardiographic features of discrete subaortic stenosis.

In two patients with discrete membranous subaortic stenosis, partial early systolic closure of the aortic valve was noted on the preoperative record. Postoperatively, this abnormality was found to be less pronounced. Narrowing of the left ventricular outflow tract was seen in the preoperative tracing in each patient. Echocardiograms taken after resection of the subaortic membrane showed widening of the left ventricular outflow tract as compared with the preoperative tracing. Thus, echocardiography may be of value in distinguishing between discrete subaortic stenosis and other forms of left ventricular outflow tract obstruction.     

Discrete subvalvular aortic stenosis in childhood: Study of 51 patients

Fifty-one children with discrete subvalvular aortic stenosis were studied between 1951 and 1974. The three anatomic types of obstruction found were the thin membranous type (43 cases), the fibromuscular collar type (5 cases) and the tunnel type (3 cases). The obstruction was usually severe, and the median left ventricular to aortic systolic pressure gradient was 90 mm Hg. Progressive obstruction with an increasing gradient was documented in 10 patients by serial cardiac catheterizations. Significant associated cardiac defects, present in 57 percent of patients, often masked the typical clinical and cardiac catheterization features of subaortic stenosis. The stenosis was often not discovered until after surgery for the associated defect.Forty patients underwent surgical resection of the discrete subaortic obstruction. After surgery significant left ventricular to aortic pressure gradients can be found at postoperative cardiac catheterization. These gradients may reflect inadequate resection of the more complex discrete obstructions or represent proliferation and regrowth of the previously resected subvalvular fibrous tissue. The criteria for operability of discrete subaortic stenosis should be the angiographic demonstration of a discrete subvalvular diaphragm and the presence of a resting left ventricular to aortic systolic pressure gradient of 40 mm Hg or more.     

Hemodynamics in endomyocardial fibrosis

Nine patients with endomyocardial fibrosis have been studied. The clinical diagnosis was confirmed by right ventricular angiography in all of them. They were submitted to right and left ventricular catheterization and had the cardiac pressures, the pulmonary arteriolar resistance, and the cardiac index measured. The ratio between the end-diastolic and systolic ventricular pressures has been taken as an index of the degree of impairment to ventricular filling, and, based on this, patients were classified into two groups: I, predominant or isolated right ventricular disease (seven patients); and II, predominant left ventricular disease (two patients).Group I patients were characterized by a right ventricular $\text{D}{}_2\text{S}$ ratio above 60 per cent, severe tricuspid regurgitation, a diastolic pulmonary artery pressure slightly lower than the right ventricular plateau and end-diastolic pressures, and a reversal of the gradient between the left ventricular end-diastolic pressure and the right atrial mean pressure; these two latter findings strongly suggesting a diastolic blood flow between the right atrium and the left ventricle.The two patients in Group II did not show evidences suggestive of tricuspid regurgitation or of an early opening of the pulmonic valve. Even presenting high values for the left ventricular $\text{D}{}_2\text{S}$ ratio, the pulmonary arteriolar resistance was normal in one patient and mildly elevated in the other patient.     

The association of fixed and dynamic left ventricular outflow obstruction.

Twelve patients were investigated echocardiographically and angiographically and were shown to have severe fixed obstruction to the left ventricular outflow tract. Eight had valvular stenosis, and four had discrete subvalvular membranes. Two of the patients had additional dynamic obstruction of the left ventricular outflow tract. This was recognized preoperatively by echocardiography because of abnormal systolic motion of the mitral leaflet. At the time of definitive surgery for relief of the fixed obstruction, the additional dynamic obstruction was identified and treated, since persistent residual obstruction may lead to death in the immediate postoperative period or to long-term symptoms. The dynamic left ventricular outflow obstruction is probably a result of the hypertrophy produced by the fixed obstruction.     

Transoesophageal echocardiographic assessment of fixed subaortic obstruction in children.

OBJECTIVE--To evaluate the clinical usefulness of transoesophageal echocardiography in the assessment of children with fixed left ventricular outflow tract stenosis. PATIENTS AND METHODS--Eight consecutive children, aged over 5 years, with fixed subaortic stenosis and one child with fixed subpulmonary left ventricular outflow tract stenosis were prospectively assessed by precordial and transoesophageal echocardiography. RESULTS--Transoesophageal images of the left ventricular outflow tract were much clearer than precordial images in all patients except one with a prosthetic mitral valve. Improved visualisation provided further information on the nature of the lesion (additional chordal attachment of the mitral valve in one, accessory atrioventricular valve tissue with aneurysm formation in one), on the extent of the lesion (circumferential in three), and on the very close relation of a ridge to the aortic valve leaflets in one. Transoesophageal Doppler did not provide any additional information on aortic regurgitation and was unreliable for gradient estimation across the left ventricular outflow tract. CONCLUSIONS--Transoesophageal imaging provides an excellent means of visualising lesions in the left ventricular outflow tract and can be useful in a few children and adolescents in whom precordial echocardiography does not provide adequate information. The technique can also be used intraoperatively to define the full extent of the obstructive lesion and to assess residual lesions after surgery.     

Fixed subaortic stenosis: anatomical spectrum and nature of progression.

Retrospective echocardiographic review identified 58 consecutive infants and children with fixed subaortic stenosis. Mean (SD) age at diagnosis was 4.8 (3.6) years (range two days to 14.7 years), and diagnosis occurred in infancy in eight. Associated cardiac abnormalities were present in 41 (71%) whereas fixed subaortic stenosis was an isolated lesion in 17 (29%). Four types of fixed subaortic stenosis were identified: short segment (47 (81%)), long segment (7 (12%)), posterior displacement of the infundibular septum with additional discrete narrowing of the left ventricular outflow tract (3 (5%)), and redundant tissue arising from the membranous septum (1 (2%)). Echocardiographic studies had been performed before the diagnosis of fixed subaortic stenosis in nine patients, all with associated abnormalities. These were performed in infancy in each and showed a "normal" left ventricular outflow tract in six and posterior deviation of the infundibular septum in three. In 16 patients serial echocardiographic studies had been performed after the diagnosis of fixed subaortic stenosis but before surgery of the left ventricular outflow tract. Rapid evolution of short segment to long segment narrowing was seen in one patient, and tethering of the aortic valve or mitral valve developed in a further four patients. Aortic valve or mitral valve involvement was not seen before the age of three years but was common thereafter (10/40 patients, 25%). Fixed subaortic stenosis may be an "acquired" lesion with the potential for changes in form as well as progression in severity of left ventricular outflow tract obstruction.     

Transoesophageal echocardiographic assessment of fixed subaortic obstruction in children.

OBJECTIVE--To evaluate the clinical usefulness of transoesophageal echocardiography in the assessment of children with fixed left ventricular outflow tract stenosis. PATIENTS AND METHODS--Eight consecutive children, aged over 5 years, with fixed subaortic stenosis and one child with fixed subpulmonary left ventricular outflow tract stenosis were prospectively assessed by precordial and transoesophageal echocardiography. RESULTS--Transoesophageal images of the left ventricular outflow tract were much clearer than precordial images in all patients except one with a prosthetic mitral valve. Improved visualisation provided further information on the nature of the lesion (additional chordal attachment of the mitral valve in one, accessory atrioventricular valve tissue with aneurysm formation in one), on the extent of the lesion (circumferential in three), and on the very close relation of a ridge to the aortic valve leaflets in one. Transoesophageal Doppler did not provide any additional information on aortic regurgitation and was unreliable for gradient estimation across the left ventricular outflow tract. CONCLUSIONS--Transoesophageal imaging provides an excellent means of visualising lesions in the left ventricular outflow tract and can be useful in a few children and adolescents in whom precordial echocardiography does not provide adequate information. The technique can also be used intraoperatively to define the full extent of the obstructive lesion and to assess residual lesions after surgery.     

Rest and exercise hemodynamics in children before and after aortic valvotomy

The rest and exercise hemodynamics in children with congenital valvar aortic stenosis were studied before and after aortic valvotomy. Eighteen patients were studied at rest; ten of the 18 patients were also studied during supine leg exercise using a bicycle ergometer.Aortic valvotomy resulted in a significant reduction in the mean left ventricular-aortic pressure gradient and in peak left ventricular systolic pressure with an increase in aortic valve area in most patients. There was an associated increase in the subendocardial blood flow assessed indirectly by the $\text{DPTI ×}\text{O}{}_2{}^{\mathrm{c}}\text{SPTI}$ ratio. There was a minor increase in the degree of aortic insufficiency in most patients.Although, in general, there was significant hemodynamic improvement, three of the 18 patients still had significant residual stenosis after surgery and another four patients had a major increase in aortic insufficiency. The three patients with residual obstruction and one of the four patients with moderate to severe aortic insufficiency still had a $\text{DPTI ×}\text{O}{}_2{}^{\mathrm{c}}\text{SPTI}$ ratio of less than 10, suggesting possible residual subendocardial ischemia. Also, the increased left ventricular end-diastolic pressures (LVEDP) present in nearly 50% of the patients before surgery did not change significantly after surgery. Three patients showed an actual increase in LVEDP after surgery.Before surgery, the left ventricular systolic pressure and mean gradient increased on exercise, but this increase was proportionately less than the increase in cardiac output, so that calculated aortic valve area increased on exercise. The $\text{DPTI ×}\text{O}{}_2{}^{\mathrm{c}}\text{SPTI}$ ratio decreased significantly on exercise, suggesting an increase in myocardial ischemia. Successful surgery resulted in a reduction in left ventricular systolic pressure and mean left ventricular-aortic gradient on exercise, and in improvement in the subendocardial blood flow as assessed by the $\text{DPTI ×}\text{O}{}_2{}^{\mathrm{c}}\text{SPTI}$ ratio.In general, children with severe aortic stenosis have relatively normal cardiac function on exercise. Some children did show a reduction of stroke index on exercise in spite of rising LVEDP. However, stroke work index increased in all of our children. Adult studies have shown many patients with decrease in stroke work index relative to LVEDP on exercise.The results of pre- and postoperative rest and exercise hemodynamics may be useful in evaluating results of surgery; the postoperative hemodynamic evaluation including the use of $\text{DPTI ×}\text{O}{}_2{}^{\mathrm{c}}\text{SPTI}$ ratio provides additional useful information which can be used in making decisions concerning exercise activity after surgery.     

Fixed subaortic stenosis: anatomical spectrum and nature of progression

Retrospective echocardiographic review identified 58 consecutive infants and children with fixed subaortic stenosis. Mean (SD) age at diagnosis was 4.8 (3.6) years (range two days to 14.7 years), and diagnosis occurred in infancy in eight. Associated cardiac abnormalities were present in 41 (71%) whereas fixed subaortic stenosis was an isolated lesion in 17 (29%). Four types of fixed subaortic stenosis were identified: short segment (47 (81%)), long segment (7 (12%)), posterior displacement of the infundibular septum with additional discrete narrowing of the left ventricular outflow tract (3 (5%)), and redundant tissue arising from the membranous septum (1 (2%)). Echocardiographic studies had been performed before the diagnosis of fixed subaortic stenosis in nine patients, all with associated abnormalities. These were performed in infancy in each and showed a "normal" left ventricular outflow tract in six and posterior deviation of the infundibular septum in three. In 16 patients serial echocardiographic studies had been performed after the diagnosis of fixed subaortic stenosis but before surgery of the left ventricular outflow tract. Rapid evolution of short segment to long segment narrowing was seen in one patient, and tethering of the aortic valve or mitral valve developed in a further four patients. Aortic valve or mitral valve involvement was not seen before the age of three years but was common thereafter (10/40 patients, 25%). Fixed subaortic stenosis may be an "acquired" lesion with the potential for changes in form as well as progression in severity of left ventricular outflow tract obstruction.     

Detection of mild aortic regurgitation by range-gated pulsed doppler echocardiography

In order to assess the sensitivity and specificity of the range-gated pulsed Doppler echocardiogram for the detection of aortic regurgitation, a study with use of this technique was carried out in 46 patients. They were classified into 3 groups: Group I was composed of 19 patients with a variety of heart diseases but with a competent aortic valve. Cardiac catheterization revealed no aortic regurgitation in any of the 19 patients, and the Doppler echocardiogram detected no turbulent diastolic flow in the left ventricular outflow tract. Group II was composed of 17 patients who clinically and by auscultation had aortic regurgitation, which was confirmed by cardiac catheterization in 6. In all 17 patients the Doppler echocardiogram detected several grades of turbulent diastolic flow compatible with aortic regurgitation in the left ventricular outflow tract. Group III was composed of 10 patients with aortic regurgitation but without the expected clinical or auscultatory evidence. The echocardiogram detected mitral valve flutter in only 1 patient. Cardiac catheterization revealed aortic regurgitation graded $\text{1}\text{4}$ and $\text{2}\text{4}$ in 9 patients, and the patient who did not undergo catheterization had a murmur of aortic insufficiency 6 months later. In all 10 patients the Doppler echocardiogram detected a regurgitating turbulent flow compatible with aortic regurgitation in the left ventricular outflow tract.It is concluded that the Doppler echocardiogram was more useful than auscultation and echocardiography for the detection of mild aortic regurgitation. In this study the range-gated pulsed Doppler echocardiogram proved 100% sensitive and specific. However, it will be necessary to study larger groups in order to assess its utility in more complicated conditions (obesity, emphysema, and heart failure) and the differential diagnosis with other diastolic murmurs.     

Relation of the echocardiographic estimate of left ventricular size to mortality in infants with severe left ventricular outflow obstruction

The relation of left ventricular size, as estimated with echocardiography, to mortality was evaluated in three groups of infants with severe left ventricular outflow obstruction. Group I consisted of 17 patients with combined aortic and mitral stenosis or atresia associated with definite hypoplasia of the left ventricle. Group II consisted of eight patients with the primary diagnosis of severe aortic stenosis. Group III consisted of 12 patients with severe coarctation of the aorta. The left ventricular enddiastolic dimension measured with M mode echocardiography and the cross-sectional area of the left ventricular cavity as seen in the parasternal long axis view of the two dimensional echocardiogram were used as indexes of left ventricular volume.All patients with symptomatic outflow obstruction and a left ventricular end-diastolic dimension of less than 13 mm died in infancy. However, five patients with a hypoplastic left ventricle proved at angiography or at autopsy, or both, were found to have a ventricular end-diastolic dimension of 13 mm or greater. Two dimensional echocardiography showed that the left ventricle in these patients was foreshortened and spherical in shape. The cross-sectional area of the left ventricle of each patient in group I was less than 1.6 cm². This was below the range of cross-sectional areas found in a group of normal infants (1.8 to 3.5 cm² ± 2 standard deviations about the mean). Three patients in groups II and III had a slightly reduced left ventricular area (1.7 cm²) and none of these patients survived infancy.Measurement of the cross-sectional area of the left ventricle is a useful method of determining left ventricular size in infants suspected of having the hypoplastic left ventricle syndrome. Patients who have reduced left ventricular volume as assessed by this technique are at very great risk even if surgical relief of the outflow obstruction is attempted.     

Coexisting right and left hypertrophic subvalvular stenosis and fixed left ventricular outflow obstruction due to aortic valve stenosis

A case of fixed left ventricular outflow tract obstruction due to aortic valve stenosis coexisting with right- and left-sided subvalvular hypertrophic stenosis is documented with hemodynamic data, angiograms, echocardiograms and findings at surgery. Histologic examination of the septal muscle with light and electron microscopy revealed hypertrophy of the muscle but none of the characteristics of idiopathic hypertrophic subaortic stenosis. Septal hypertrophy with subvalvular obstruction can occur secondary to left ventricular pressure overload due to fixed left ventricular outflow tract obstruction and is not always the chance occurrence of two separate diseases.     

Left ventricular outflow tract obstruction in atrioventricular septal defects: a pathologic and morphometric evaluation.

Subaortic stenosis has been described with increasing frequency as an ominous feature of atrioventricular septal defect (AVSD), especially following surgical correction of the anomaly in non-Down's syndrome patients. In order to study the surgical anatomy of the left ventricular outflow tract in this malformation, 48 hearts featuring AVSD were examined. Obstructive lesions were classified into unequivocal forms (class A, 13.5%) and potential ones (class B, 10.8%). In the remaining hearts (class C, 75.7%) no obstruction was noted. In class A, subaortic stenosis was due to exaggeration of the anticipated anomalous arrangement of atrioventricular valve tensor apparatus, to the persistence of a subaortic muscular infundibulum, and to a discrete fibrous diaphragm. A potential for subaortic stenosis is provided by the unwedged position of the aortic valve. The left ventricular outflow tract is transformed into a long, forward-displaced fibromuscular channel. Morphometric analysis showed in AVSD (with both common annulus and separate orifices) a significantly (p less than 0.01) lower inflow/outflow tract ratio, and a significantly (p less than 0.01) lower right ventricular/left ventricular outflow length ratio than normal hearts. These results suggest that AVSD is characterized not only, as commonly stated, by inflow tract shortening, but by outflow tract lengthening as well. On these anatomical grounds, nearly all cases of AVSD could harbor the potential for subaortic stenosis; however, this becomes a real hazard (class B) only when associated with forward displacement of the left anterior papillary muscle, or direct insertion on the ventricular septum of the anterior bridging leaflet, and it may be converted to an actual obstruction by the effects of surgery.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of ouabain and diphenylhydantoin on myocardial potassium balance in man

Myocardial potassium balance and hemodynamics were studied in 19 patients. In 12 patients the effect of diphenylhydantoin administration was studied and in 7 the effect of pretreatment with diphenylhydantoin on the ionic and hemodynamic responses to ouabain was observed. Diphenylhydantoin caused no change in myocardial potassium balance, but a significant fall in left ventricular $\text{dP}\text{dt}$ and a brief increase in left ventricular end-diastolic pressure occurred. Heart rate, cardiac output, stroke work and brachial arterial pressure did not change. In patients pretreated with diphenylhydantoin, ouabain administration was followed by a significant loss of potassium from the myocardium. This was accompanied by a significant increase in left ventricular $\text{dP}\text{dt}$ and a decrease in left ventricular end-diastolic pressure. No change occurred in heart rate, cardiac output, stroke work or brachial arterial pressure. These ionic and hemodynamic responses to ouabain after pretreatment with diphenylhydantoin are similar in magnitude and timing to those observed when only ouabain is administered. These results in man are compatible with theories of digitalis action which associate inotropic effect with the inhibition of membrane sodium- and potassium-activated adenosine triphosphatase and indicate that diphenylhydantoin acts on the heart by some mechanism other than stimulation of this enzyme.     

Diagnosis of idiopathic hypertrophic subaortic stenosis by right ventricular septal biopsy

The clinical, hemodynamic and histologic features of six adult male patients with idiopathic hypertrophic subaortic stenosis are compared with those of three adult patients with aortic valve stenosis. All nine patients had a right ventricular septal biopsy, and the tissue so obtained was examined by light and electron microscopy. The characteristic disorganized architecture with random orientation of myoflbers seen by others in tissue removed from the left ventricular outflow tract was also observed in each specimen from patients with idiopathic hypertrophic subaortic stenosis but in none of those from patients with aortic stenosis. The changes were even more striking and bizarre when viewed under the electron microscope. Whorled collagen fibers in the tissue of three patients with Idiopathic hypertrophic subaortic stenosis resembled the whorled myofibers. Neither structural abnormality was seen in tissue obtained from patients with aortic stenosis. Thus, biopsy of the right ventricular septum can differentiate idiopathic hypertrophic subaortic stenosis from aortic stenosis, even when the specimens are examined by light microscopy alone.     

Early sequential changes in left ventricular dimensions and filling pressure in patients after myocardial infarction

Early consecutive changes in pulmonary arterial end-diastolic pressure (PAEDP) and echocardlographic left ventricular dimensions were measured in 14 patients within the first 8 days after acute myocardial infarction. Left ventricular volumes were estimated from echocardiographic left ventricular dimensions. Left ventricular compliance was assessed by three formulas, $\text{ΔV}\text{ΔP}$, ΔV/ESV/ΔP and $\text{LVID}{}_{\mathrm{d}}\text{PAEDP}$, where AV = echocardiographic stroke volume, ΔP = a derived left ventricular diastolic pressure change from the lowest level of early diastolic to the end-diastolic pressure, ESV = left ventricular end-systolic volume, and LVID_d = echocardiographic left ventricular end-diastolic dimension. To compare pressure, dimension and compliance values, linear relations were assumed between values for left ventricular end-diastolic volume, end-systolic volume, pulmonary arterial end-diastolic pressure and the day after infarction. The estimated third day values for the variables obtained from these linear relations were used so that each patient's values would contribute equal weight to the statistical analysis.The estimated third day compliance values from each formula correlated highly with one another (r = 0.69 ? 0.82). Neither $\text{ΔV}\text{ΔP}$ nor ΔV/ESV/ΔP had a significant correlation with LVID_d. Echocardiographic end-diastolic volume correlated with both end-systolic volume (r = 0.89) and echocardiographic stroke volume (r = 0.62) but not with pulmonary arterial end-diastolic pressure. When the first and last measurements for each patient are used, large changes in pulmonary arterial end-diastolic pressure associated with no or small alterations in echocardiographic left ventricular end-diastolic dimension in 12 patients imply acute changes in ventricular compliance. Sequential compliance values ($\text{ΔV}\text{ΔP}$) increased in seven survivors and decreased in one. $\text{ΔV}\text{ΔP}$ decreased in the five patients who died or had electrocardiographic evidence of extension of infarction. Early sequential changes in filling pressure, echocardiographic dimensions, and left ventricular compliance had a close correlation with the clinical course of the patients in our series and these data may assist in the management of patients with hemodynamic instability after acute myocardial infarction.