A novel MHC class II epitope expressed in thymic medulla but not cortex

The repertoire of receptors expressed by peripheral T cells is the result of two selective events that occur during intrathymic development. Positive selection expands cells able to recognize foreign peptides presented by self MHC molecules, and negative selection eliminates cells reactive to self MHC molecules and associated self peptides. Chimaera studies suggest that, at least in the case of T cells recognizing MHC class II, interaction with thymic cortical epithelial cells is responsible for the former, whereas thymic medullary cells, of bone marrow origin, mediate the latter. This view of thymic development is supported by recent morphometric analyses, showing that autoreactive cells are found in thymic cortex but not medulla. Although numerous studies have shown that MHC class II molecules are expressed in both sites, none provides any explanation for the differential selection of T cells that is observed. Here, we describe a novel MHC class II epitope which is found on cells in thymic medulla but not cortex. The antibody to this epitope reacts with about 10% of class II molecules on B cells and may be recognizing a self peptide-MHC complex. These results provide the first evidence for differential expression of class II epitopes in different tissues and are compatible with the hypothesis that different ligands, rather than different affinity thresholds for the same ligand, are involved in positive and negative selection of the T-cell repertoire.

Isotype switching by a microinjected mu immunoglobulin heavy chain gene in transgenic mice

Immunization of transgenic mice carrying an immunoglobulin mu heavy chain resulted in a response dominated by expression of the transgene variable region. Unexpectedly, in a large proportion of the antibody produced by immunized mice, the transgene variable region was associated with IgG rather than IgM. This demonstrates that the transgene can undergo an isotype switch. Four transgenic founder lines all exhibited transgene isotype switching despite the likelihood of random chromosomal integration of the transgene. In addition one of the lines was analyzed by breeding studies and the transgene was found to be genetically unlinked to the immunoglobulin heavy chain (Igh) locus. These results indicate that a precise chromosomal location is not required for isotype switching and suggest the possibility that the isotype switching process can occur interchromosomally.

Cross-linking and conformational change in T-cell receptors: role in activation and in repertoire selection

TCRs undergo a series of interactions with ligands during development. We have characterized the interaction of a TCR with its ligand and the attendant co-receptor and co-ligand structures. This characterization has led to the model in which the TCR not only binds to class II MHC, but also binds to CD4 co-receptors and co-ligands such as Mls. We have shown that both cross-linking and conformational change in the TCR are required for optimal T-cell activation. Finally, we have used the observation that a particular self-peptide found abundantly associated with class II MHC in the periphery is essentially lacking from thymic cortical epithelium to argue that positive selection for self-MHC recognition may occur by a novel process in the thymic cortex. A TCR recognizing class II MHC with low affinity could either be multiply cross-linked in the absence of conformational change, which here would be driven by a unique peptide, or could be conformationally changed without cross-linking due to the rarity of the individual high-affinity peptide on thymic cortical epithelial cells. Either proposal leads to a partial signal one delivered via the TCR, which we refer to as signal one-half. This signal one-half would induce the cell to repress its other co-receptor molecule and to undergo maturation events such as up-regulation in TCR expression. Such cells are then rigorously screened for activating interactions with autologous structures, such as Mls. The threshold for clonal deletion is set very low to avoid autoreactivity. By this combination of signaling events, a mature TCR repertoire is generated that has the functional characteristics observed in immune systems.

Anti-idiotypic humoral and cellular responses to antibody to hepatitis B surface antigen in hepatitis B viral infections

In order to investigate regulatory significance of humoral and cellular responses to the idiotypic (Id) determinants on the antibody to hepatitis B surface antigen (anti-HBs), they were studied in acute hepatitis B and in chronic HBV infection. The results were compared with humoral and cellular responses of the same patients to hepatitis B surface antigen (HBsAg). In acute hepatitis B, the responses to HBsAg, were delayed until 3-4 weeks after the onset of clinical symptoms. However, the leucocyte migration inhibition (LMI) and the lymphocyte transformation (LTT) responses to affinity purified anti-HBs were found to be evolved very early in the course of acute hepatitis B, though anti-Id antibodies were absent. The majority of chronic HBV carriers showed a poor humoral and cellular response to HBsAg. Ten out of 38 chronic carriers showed anti-Id antibodies which recognized a major cross-reactive idiotype (CRI) on the anti-HBs molecule. Twenty-five out of 38 chronic carriers also showed LMI response to the Id determinants on the anti-HBs. LMI response induced by anti-HBs could be blocked by a specific Balb/c anti-Id antibody which also recognized the CRI. Thus, in both acute and chronic HBV infections, the anti-Id humoral and cellular responses correlated with poor humoral and cellular responses to HBsAg, indicating regulatory significance.

Characterization of regional left ventricular contraction by curvature difference analysis

A method which characterizes the contraction of the left ventricle (LV) by changes in the LV endocardial contour curvatures is presented. A normalized curvature difference function (NCDF) is defined by the difference between the (normalized) curvature functions of end diastolic (ED) and end systolic (ES) contours. Unlike wall-motion based procedures, NCDF is independent of any reference system and of the method used for ED-ES shape alignment. Normal and pathological diagnosis criteria were first established based on right anterior oblique (RAO) projection ventriculograms of a study group which included 58 normal and 28 abnormal patients. Patients with an infarcted myocardial region differed from the characteristic NCDF pattern of normals and exhibited regionally defined irregularities. The diagnosis criteria were then applied to a total of 159 patients in two groups in two independent laboratories. One group (in Israel) included 49 cases (20 normals, 29 abnormals); the second (in France) included 108 cases (48 normals, 60 abnormals). These two groups yielded similar sensitivity (97% and 97%) and specificity (90% and 100%) in detection of abnormality of the ventricle. When tested against other quantitative wall motion techniques, the NCDF shwos a regional sensitivity of 95%, indicating that curvature difference analysis is a potential tool for the automatic and objective diagnosis of regional LV function abnormalities.

IgG subclass composition of antibodies to HBsAg in circulating immune complexes from patients with hepatitis B virus infections

The IgG subclass of antibody associated with hepatitis B surface antigen (HBsAg) in circulating immune complexes (CIC) from patients with either acute or chronic hepatitis B virus (HBV) infections was measured using an isotype and antigen-specific ELISA. All patients were HBsAg positive but were negative for free anti-HBs antibody. The subclass of antibody associated with HBsAg in CIC in both groups was predominantly IgG1 and IgG4. This is in contrast to free anti-HBs in convalescent sera from patients recovering from HBV infection, which are highly restricted to IgG1 and IgG3. The finding of high levels of IgG4 antibodies in CIC suggest that CIC containing this subclass may be cleared less efficiently than CIC containing antibodies of other subclasses. Formation of these CIC may be an important factor in the progression of infection to chronicity and may also be involved in the antigen-specific immunosuppression seen in early acute and chronic HBV infections.

Functional affinity of IgM rheumatoid factor in patients with rheumatoid arthritis and other autoimmune diseases

The functional affinity of IgM rheumatoid factors (RF) was measured in 31 patients with rheumatoid arthritis (RA), 24 with systemic lupus erythematosus (SLE), 13 with Sjögren's syndrome (SS), and in 13 seropositive healthy individuals. The functional affinity of IgM RF from patients with RA was significantly lower than in the other clinical groups studied. In addition, there was a significant inverse correlation between functional affinity and titre of IgM RF in all the groups. These results suggest that the usual mechanisms of affinity based selective pressure (somatic diversification and antigen selection) may operate differently for autoantibodies to serum antigens such as IgG.

An inhibition enzyme immunoassay for estimating relative antibody affinity and affinity heterogeneity

A method to measure the relative affinity of antibodies using an inhibition enzyme immunoassay is described. It is validated using monoclonal antibodies of defined affinity characteristics and by comparison with conventional methods of affinity measurement. The method allows measurement of the relative affinity of low levels of antibody, and the calculation of an empirical estimate of the heterogeneity of affinity in antibody populations.

Determination of the functional affinity of IgG1 and IgG4 antibodies to tetanus toxoid by isotype-specific solid-phase assays

Two solid-phase assays have been used to measure the affinity of IgG1 and IgG4 antibodies to tetanus toxoid (TT) in whole sera. In the first assay, low affinity antibodies were selectively inhibited from binding to solid-phase antigen by a mild chaotropic agent and in the second assay, high affinity antibodies were preferentially inhibited from binding by low concentrations of free antigen. Results from both assays suggest that IgG4 antibodies to TT are of lower functional affinity than IgG1 antibodies and that, in addition, IgG4 responses to TT display a more restricted affinity heterogeneity.

Hemodynamic effects of oral isosorbide-5-mononitrate and dinitrate in ischemic heart failure

Isosorbide-5-mononitrate (ISMN), the main metabolite of isosorbide dinitrate (ISDN) was recently introduced in clinical use. The hemodynamic effects of oral ISMN and ISDN, administered in equal doses, were studied in a randomized, crossover fashion in 20 patients with pump failure of ischemic etiology. Baseline hemodynamic criteria for admission into the study were: pulmonary capillary wedge pressure (PCW) of at least 20 mmHg and systolic arterial pressure (AP) above 90 mmHg. Hemodynamic parameters were serially measured and systemic vascular resistance was calculated up to 6 h postadministration of either ISMN or ISDN single dose (40 mg). Maximal effects obtained were statistically significantly different from baseline. While ISMN and ISDN appeared to be equipotent in reducing the filling pressure, with a maximum effect reached in 60-120 min, the mononitrate maintained its effects for a longer period.

Virological markers and antibody responses in fulminant viral hepatitis

Clinical profiles, serological markers, and antibody responses to antigens of hepatitis B virus (HBV) were studied in patients with fulminant viral hepatitis. Whereas hepatitis A and B were found to be uncommon causes (6.9% and 12.2%, respectively), non-A, non-B (NANB) hepatitis was found to be the most common cause of fulminant hepatitis (80.9%). As against this, the incidence of hepatitis B and NANB hepatitis was very similar in nonfulminant acute viral hepatitis in adults (41.2% and 51.9%, respectively). Pregnancy with labour was an important precipitating factor for development of fulminant hepatitis of the NANB type only; 32% of fulminant NANB hepatitis patients were pregnant women and 22.6% had a history of labour preceding hepatic coma. Only 0.8% of nonfulminant NANB hepatitis cases were pregnant women. Another major precipitating factor for the development of the fulminant form of NANB hepatitis was concomitant chronic HBV carrier state. A total of 38.6% of fulminant NANB hepatitis patients were HBV carriers, whereas only 19.2% of nonfulminant acute NANB hepatitis cases were HBV carriers. Sera of 32 chronic HBV carriers with fulminant NANB hepatitis and 10 cases of fulminant hepatitis B were tested for delta antibody, and all were nonreactive. The antibody responses of the fulminant hepatitis B patients to the antigens of HBV were found to be greater compared to those of patients with nonfulminant acute hepatitis B. Antibody responses of chronic HBV carriers with fulminant NANB hepatitis to antigens of HBV were found to be depressed in comparison with those of chronic asymptomatic carriers.

Mechanisms of liver cell damage in acute hepatitis B

Markers of hepatitis B viral infection and the evolution of immune response to these were compared with serum alanine aminotransferase (ALT) levels in adult male and non-pregnant and pregnant female patients with acute hepatitis B from the time of onset of disease to the seventh week. In the adult male and non-pregnant female patients, the peak ALT levels of about 360 IU/litre, seen at the time of onset, gradually declined during the course of the disease. Significantly, even in the seventh week, the median ALT level was abnormal (80 IU/litre). In contrast, the disease was mild in pregnant patients and the ALT levels declined rapidly, returning to normal by the third week. Markers associated with HBV replication, i.e., serum HBV-DNA and HBeAg, declined early in the course of the disease in both groups. The anti-HBc-IgM and anti-HBe responses were well evolved early in the course of the disease in both groups. HBsAg was present in the serum in large amounts (1-1.5 X 10(4) AU/100 microliter) early in the course of the disease and remained so up to the seventh week. Even the pregnant patients who had recovered clinically by the fourth week continued to have HBsAg in their sera in large amounts in spite of normal ALT levels. LMI and LTT responses to HBsAg, which were practically absent in the first week, gradually increased to a peak during the fourth week and remained elevated up to the seventh week in adult male and non-pregnant female patients. In contrast, LMI response to HBsAg was absent in pregnant patients with acute hepatitis B even up to the fourth week Thus, continued liver cell necrosis after the fourth week, as indicated by raised ALT levels, may be associated with T cell responses to HBsAg.

Regulation of cell-mediated immunity in mice immunised with Salmonella enteritidis

The effects of diverse factors, such as route of immunisation, composition of immunogen and administration of interferon inducer, on the expression of cell-mediated immune responses against Salmonella enteritidis were investigated in BALB/c and Swiss white mice. Immunisation with live cells of S. enteritidis by the intraperitoneal route (ip) generated both delayed type hypersensitivity (DTH) and protective cell-mediated immunity (CMI). However, the two responses showed diametrically opposite time kinetics. The decline and disappearance by 9 weeks after ip immunisation of DTH and the rise of protective immunity in the same period suggested the possibility that the two responses were mediated by different subsets of T cells. Immunisation by the intradermal (id) route with a sonicate of S. enteritidis generated only DTH; id immunisation also suppressed the development of the protective response following ip immunisation with live S. enteritidis. Both responses were not seen when T cells were eliminated with anti-T cell serum. Oral immunisation with live cells of S. enteritidis induced excellent CMI expressing both DTH and protective responses. On the other hand, oral immunisation with the sonicate of S. enteritidis not only did not induce CMI, but also prevented the development of the DTH and protective response to ip immunisation with live S. enteritidis. Induction of interferon by the administration of poly I: poly C for four consecutive days after id immunisation with killed S. enteritidis suppressed the generation of DTH.

Review of echocardiographically diagnosed right heart entrapment of pulmonary emboli-in-transit with emphasis on management

2DE permits detection of thromboemboli transiently entrapped in the right heart chambers while en route to the pulmonary arteries. Review of the 49 cases recorded to date reveals that the supple elongated clot produces a 2DE picture--a mass of changing configuration and striking mobility--that is highly characteristic. Since emboli that become entrapped are large, when managed by medical measures alone they have an attendant mortality rate of 50%, usually soon after 2DE diagnosis, upon completion of pulmonary embolization. Death occurred in 8 of 16 patients treated with anticoagulants, thrombolytic agents, or antiaggregants and in 6 of 13 who received supportive measures only. Of 20 patients referred for surgery (cardiotomy and, in 17, pulmonary embolectomy), only three died, two of them failures of preceding anticoagulant treatment. These data indicate that thromboemboli entrapped in the right heart chambers are best handled as a surgical emergency.

Two-dimensional echocardiographic analysis of proximal left main coronary artery in humans

The left main coronary artery (LMCA) was evaluated in 100 consecutive patients (88 men and 12 women; mean age 63 years) with anginal syndrome, all in New York Heart Association classes II and III. Each patient underwent two-dimensional echocardiography (2DE) from the parasternal short-axis and apical four-chamber views. Coronary angiography was subsequently performed within 24 hours. The LMCA was directly measured by 2DE and coronary angiography at its widest point. Each echocardiogram was blindly evaluated for LMCA aneurysm or obstruction. Eight patients (8%) were excluded because of inadequate visualization of the LMCA. The mean 2DE measurement was 4.4 +/- 0.9 mm vs 4.2 +/- 0.8 mm on coronary angiography (r = 0.86). Atherosclerotic aneurysms of the LMCA were correctly diagnosed in two patients by 2DE. LMCA stenosis (greater than 50%) was found in 11 patients on coronary angiography; three of them had ostial or proximal lesions, three had middle lesions, and five had distal lesions. 2DE correctly diagnosed all three ostial lesions, two of three middle lesions, but only two of five distal lesions. In four patients, dense echoes in the LMCA caused a false positive diagnosis. It was concluded that: the LMCA can be visualized and correctly measured by 2DE; atherosclerotic aneurysms can be detected; and 2DE is yet unable to screen patients for LMCA lesions; however, 2DE is a promising method for evaluating proximal and especially ostial LMCA stenosis.

Changes in systemic vascular resistance detected by the arterial resistometer: preliminary report of a new method tested during percutaneous transluminal coronary angioplasty

A recently developed apparatus provides on-line continuous monitoring of systemic vascular resistance (SVR) by means of simple computer analysis of the peripheral arterial waveform. The fundamental equation of this method is Ri = P'/(dP/dt), where dP/dt is the peak dP/dt of the peripheral arterial waveform, P' is the pressure at time of peak dP/dt, and Ri is a resistance index that bears a direct relation to SVR. Eleven patients undergoing percutaneous transluminal coronary angioplasty (PTCA) were studied to evaluate the changes in SVR associated with myocardial ischemia (angina detection). There were 49 balloon inflations, all of which were associated with an increase in Ri (from 38.4 +/- 12 to 81.2 +/- 36 X 10(-3) sec; p less than .01) and a decrease in dP/dt (from 2076 +/- 257 to 1327 +/- 326 mm Hg/sec; p less than .01). In 42 of the balloon inflations these changes were associated with electrocardiographic ST-T changes and in 23 it was also associated with anginal pain. When angina was present, a further increase in Ri (to 97.5 +/- 43 X 10(-3) sec; p less than .01) and a decrease in dP/dt (to 1218 +/- 338 mm Hg/sec; p less than .01) was observed. It was found that myocardial ischemia is associated with an increase in the resistance index and a decrease in dP/dt and can be detected by the resistometer.

Severe aortic regurgitation: a rare presentation of giant cell arteritis

A 53-year-old patient with no past history of rheumatic fever or lues presented with severe aortic regurgitation, underwent hemodynamic evaluation, and subsequently, an uneventful aortic valve replacement. The initial pathological interpretation was nonspecific aortitis. Six months following surgery arthralgia, muscular pain, difficulty in mastication, and fatigue occurred. There was no fever, however, sedimentation rate was 100/130. Cardiac examination was normal. Review of the pathological specimens revealed granulomatous arteritis with giant cells, typical of giant cell arteritis. Though the association of aortic regurgitation and giant cell arteritis is well recognized, only two such cases of severe aortic regurgitation requiring valve replacements have yet been described, of them, one probably had Takayasu's arteritis. An accurate diagnosis is of importance since steroid treatment is effective, and if introduced early, the inflammatory process may be arrested.

Improvement by oral metoprolol of exercise-induced ischemic dysfunction in patients with coronary heart disease

The effect of metoprolol on global left ventricular function during exercise was analyzed with nuclear ventriculography in 17 patients with ischemic heart disease. All had stable angina pectoris and ST-segment depression of more than 0.1 mV during treadmill exercise when not taking metoprolol. Each patient was stressed with supine bicycle exercise to the same load on a maintenance dose of metoprolol (100 mg X 2/day) and on a second occasion without the drug, the two being separated by 7 days. The mean heart rate and systolic blood pressure were significantly reduced both at rest and exercise with metoprolol. There was no significant difference of rest left ventricular ejection fraction with or without metoprolol. At exercise, however, every patient showed improvement of left ventricular function, the average left ventricular ejection fraction increasing by 14% (+/- 6) relative to the same exercise without metoprolol (p less than 0.001). We conclude that chronic metoprolol treatment in patients with ischemic heart disease can ameliorate left ventricular dysfunction induced by exercise and may thereby reduce myocardial ischemia.

Does complete revascularization by the conventional method truly provide the best possible results? Analysis of results and comparison with revascularization of infarct-prone segments (systematic segmental myocardial revascularization): the Sheba Study

Myocardial revascularization is usually considered "complete" if all stenosed major coronaries are bypassed. Attempts were made to compare the results of this method with an approach by which each of the following five left ventricular infarct-prone segments is revascularized if ischemic: anteroseptal, anterolateral, posterosuperior, posteroinferior, and diaphragmatic. Two subsets of patients were studied. A total of 366 patients (Group A) who underwent aortacoronary bypass operations from 1980 to 1982 were followed up for a mean of 16.3 (6 to 43) months and were retrospectively divided into two groups: Group A1 (120 patients) had incomplete segmental revascularization (mean of 3.4 grafts per patient) and Group A2 (246 patients) had complete segmental revascularization (4.0 grafts per patient) (p less than 0.0001). Groups A1 and A2 were identical in all clinical and angiographic parameters: unstable angina, 60%; previous myocardial infarction, 70%; left main stenosis, 10%; and ejection fraction less than 30%, 2%. Overall operative mortality was 2.3%. Results in Groups A1 and A2, respectively, were as follows: operative mortality, 5.8% versus 0.8% (p less than 0.005); perioperative myocardial infarction, 6.9% versus 0.8% (p less than 0.0005); 35 month survival rate, 93.3% versus 97.9% (p less than 0.02); total freedom from symptoms, 54.1% versus 68.3% (p less than 0.025). In addition, 151 patients operated on in 1984 (Group B) were studied prospectively with regard to operative mortality and perioperative myocardial infarction, and the results were identical to those in Group A. Compared to conventional complete revascularization, complete segmental revascularization provides better results.

The effects of varying lengths and powers of CO2 laser pulses transmitted through an optical fiber on atherosclerotic plaques

We have studied the changes induced in atherosclerotic arteries by a CO2 laser beam delivered through a silver halide optical fiber. We found that the crater depth and diameter correlate with the total energy delivered and with the mode of delivery. Short-duration high-power pulses caused shallower and narrower craters and less damage to the arterial wall compared to the same energy delivered as low-power pulses of long duration. Thus, high-power pulses for short periods may be an effective and safe procedure for evaporization of atherosclerotic plaques.

Hemodynamic effects of nifedipine in hypertension in the presence of elevated angiotensin-II and beta-adrenergic blockade

The hemodynamic effects of the slow release form of a calcium channel blocker, nifedipine retard, in essential hypertension patients after angiotensin II (AII) infusion were studied using nuclear ventriculography. Sublingual nifedipine lowered blood pressure that had been acutely raised by an infusion of AII to its baseline level. When used for 4 weeks, nifedipine retard maintained its blood-pressure-lowering effects without a change in heart rate, both when used alone and when used in addition to beta-adrenergic blockers. In the patients with untreated essential hypertension, nifedipine counteracted the lowering effect of AII on left ventricular ejection fraction (LVEF), which was 67.5 +/- 8.9% at recumbency, 61.2 +/- 6.6% (+/- SD) during AII infusion, and 72.1 +/- 7.5% 30 minutes after sublingual nifedipine. These acute effects seem to result from a marked reduction in total peripheral resistance (TPR) and are accompanied by a rise in cardiac index (CI). The TPR, in dynes/sec/cm-5, was 1376.9 +/- 275.8 at recumbency, 2000.7 +/- 358 during AII infusion, and 1228.6 +/- 289 30 minutes after sublingual nifedipine. The corresponding figures for CI in liters/M2 BSA, were 4.02 +/- 0.77, 3.03 +/- 0.64, and 4.32 +/- 0.79. In patients receiving beta-blocker therapy (propranolol or atenolol) with inadequate control of blood pressure, similar results were obtained in LVEF (69.7 +/- 8.87% at recumbency, 63.7 +/- 11.9% during AII infusion, and 72.2 +/- 6.05% 30 minutes after sublingual nifedipine). The initial TPR was much higher than that of untreated essential hypertensive patients. Nevertheless, the increase obtained during AII infusion was counteracted by sublingual nifedipine. CI was decreased by AII.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential regulation of effector responses of cell mediated immunity in experimental salmonellosis

Delayed type hypersensitivity (DTH) and protective cell mediated immunity showed different profiles with respect to time following intraperitoneal immunization with live Salmonella enteritidis. Whereas the DTH response decreased with time the Protection Index increased. The decline in DTH response was found to be associated with suppressor cells generated by intraperitoneal immunization and could be prevented by cyclophosphamide treatment prior to immunization. It was concluded that the two effector responses of cell mediated immunity were under differential regulation.

Fate of nonobstructive aneurysmatic coronary artery disease: angiographic and clinical follow-up report

The incidence of coronary aneurysmatic dilatation without coronary stenosis is rare, and the clinical course of such an entity is unknown. We present five adult patients, four men and one woman, with such an anatomic finding. The age range was 44 to 60 years. In four patients the aneurysmatic dilatations involved multiple coronary sites. The clinical course in all five patients was suggestive of coronary insufficiency. Despite no obstructive disease, two of the patients developed transient ischemic ECG changes accompanied by chest pain, and another two patients demonstrated ischemic exercise nuclear ventriculography response. In time, all five patients developed acute myocardial infarction and recatheterization revealed complete occlusion of a previously nonstenosed aneurysmatic vessel. More information is needed in order to guide therapy. However, prevention of thrombus formation and close follow-up is highly recommended.

Two-dimensional echocardiography in discrete subaortic stenosis

Thirty-seven patients with discrete subaortic stenosis (DSS) underwent 2-dimensional echocardiography (2-D echo) and cardiac catheterization. The peak systolic pressure gradients ranged from 0 to 150 mm Hg. Thirty-two patients had membranous DSS and 5 had fibromuscular DSS. Of 37 patients with DSS, 2-D echo diagnosed the presence and type in 35; in 2, a membrane was demonstrated by angiography. Of the 35 patients accurately diagnosed by 2-D echo, angiography corroborated the diagnosis in 33, but failed to show the membrane in 2. Subsequent cardiac surgery confirmed the accuracy of the echocardiographic diagnosis in these 2 patients. In all patients with membranous DSS, the anterior insertion of the membrane was demonstrated. In 9 of them the posterior insertion was demonstrated by tilt of the transducer but the anterior insertion disappeared. In 4 patients both insertions were demonstrated simultaneously and in 3 patients the membrane was demonstrated as a continuous line. In 4 of the 5 patients with fibromuscular DSS, both insertions of the lesion were demonstrated simultaneously. However, 2-D echo was unsuccessful in assessing the severity of obstruction. In only 1 patient did demonstration of the whole subaortic membrane as a continuous line below the aortic valve correlate with severe obstruction. Thus, the presence and type of DSS, but not the degree and severity, can be accurately and reliably diagnosed by means of 2-D echo.

Correlation between echocardiography and cardiac catheterization in assessing the severity of aortic stenosis

The severity of aortic stenosis was assessed by echocardiography in 81 consecutive adult patients, 40 of whom underwent cardiac catheterization. The patients' mean age was 54 +/- 16.4 years. A good correlation was found between the severity of aortic stenosis assessed by cross-sectional echocardiography and cardiac catheterization. Aortic valve separation of 7 mm or less occurred only in severe aortic stenosis whereas a separation of 12 mm ruled out any significant aortic stenosis. A separation of 8-11 mm constituted a 'grey' area between mild and severe aortic stenosis. Cross-sectional echocardiography provides a reliable method for crude evaluation of aortic stenosis.

Systolic closure of aortic valve in patients with prosthetic mitral valves

Systolic closure of the aortic valve was found in 10 of 36 patients who underwent mitral valve replacement. Eight patients had early systolic closure, and two had mid-systolic closure. The left ventricular outflow tract dimension on M-mode and two dimensional echocardiograms, left ventricular posterior wall and septal thickness, left ventricular dimensions in systole and diastole, aortic valve opening, and mitral to aortic valve distance were not significantly different between patients with and without systolic closure of the aortic valve. Two of the 10 patients with systolic aortic valve closure were catheterised and in neither was there a gradient between the left ventricle and the aorta. The two patients with mid-systolic closure, however, were the patients who had the narrowest left ventricular outflow tract which could cause significant distortion of blood flow. Systolic closure of the aortic valve in patients with mitral valve replacement is probably not caused by left ventricular outflow tract obstruction, though abnormalities in laminar flow from the left ventricular outflow tract may be involved.

Bilateral congenital coronary artery fistula

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