Assessment of mitral annular dynamics during diastole by Doppler tissue imaging: comparison with mitral Doppler inflow in subjects without heart disease and in patients with left ventricular hypertrophy

The purpose of this study was to determine the normal pattern and magnitude of mitral annular velocities in diastole by Doppler tissue imaging (DTI) and to assess whether this is altered in patients with left ventricular hypertrophy. Mitral annulus velocities were measured by DTI. Peak and time-velocity integral were measured from the DTI tracings and the timing of the velocities in relation to electrocardiogram. DTI was compared with M-mode echo of the annulus and mitral inflow Doppler velocities. Integrated annular velocities by DTI correlated with the annular displacement. Early diastolic velocities decreased with age and in patients with left ventricular hypertrophy. In the hypertrophy group, early diastolic velocities were significantly lower than normal even after correcting for age. Patients with left ventricular hypertrophy also showed a delay in peak early diastolic mitral annular velocity (5.5 +/- 21 msec after the E wave). In conclusion, mitral annular velocity in diastole is readily recorded by DTI. The magnitude and the pattern of these velocities are significantly altered by age and by left ventricular hypertrophy. This method provides a new insight into diastolic filling events and may prove useful in detecting abnormal diastolic function.

Plasma volume and its regulatory factors in congestive heart failure after implantation of long-term left ventricular assist devices

BACKGROUND

Congestive heart failure is associated with blood volume expansion caused by stimulation of the renin-aldosterone system and arginine vasopressin. The use of left ventricular assist devices as bridges to heart transplantation has improved the survival of patients during this critical period. In studying heart failure physiology on support devices, we hypothesized that improvement of cardiac function by a left ventricular assist device is associated with normalization of volume load secondary to normalization of its regulatory substances.

METHODS AND RESULTS

We studied 15 patients (13 men, 2 women: age 51 +/- 8 years) with end-stage heart failure who were cardiac transplant candidates eligible for HeartMate implantation. We measured plasma volume and plasma levels of atrial natriuretic peptide, aldosterone, renin, and arginine vasopressin sequentially before HeartMate implantation (baseline), after HeartMate implantation (weeks 4 and 8), and after transplantation. Baseline plasma volume was 123 +/- 20% of normal; it was 122 +/- 22% at week 4 and decreased to 115 +/- 14% at week 8. Atrial natriuretic peptide was 359 +/- 380 pg/mL at baseline, 245 +/- 175 pg/mL at week 4, and 151 +/- 66 pg/mL at week 8. Plasma aldosterone fell from 68 +/- 59 ng/dL at baseline to 17 +/- 16 ng/dL at week 4 (P < .05 versus baseline) and was 32 +/- 50 ng/dL at week 8. Plasma renin activity decreased from 80 +/- 88 ng/dL at baseline to 11 +/- 12 ng/dL at week 4 and was 16 +/- 38 ng/dL at week 8 (both P < .05 versus baseline). Arginine vasopressin fell from 5.0 +/- 4.8 fmol/mL at baseline to 1.1 +/- 0.7 fmol/mL at week 4 and 1.2+/-0.8 fmol/mL at week 8 (both P < .05 versus baseline).

CONCLUSIONS

The reduction of plasma renin activity, plasma aldosterone, and arginine vasopressin occurred earlier than the reduction of plasma volume and atrial natriuretic peptide after HeartMate implantation, possibly because of decreased pulmonary congestion and improved renal perfusion. The reduction of atrial natriuretic peptide cannot be responsible for the lack of adequate decrease of plasma volume; its reduction can be taken as a marker of improved cardiac pump function and decreased atrial stretch.

Value of proximal regurgitant jet size in tricuspid regurgitation

Recent studies have shown good agreement between proximal regurgitant jet size obtained with transthoracic color flow mapping and regurgitant fraction in patients with mitral regurgitation. To evaluate this in patients with tricuspid regurgitation, we analyzed 40 patients in sinus rhythm, 16 with free jets and 24 with impinging jets, comparing proximal jet size (millimeters) with parameters derived from the Doppler two-dimensional echocardiographic method (regurgitant fraction) and the flow-convergence method (peak flow rate, effective regurgitant orifice area, and momentum). Good agreement was noted between peak flow rate (r = 0.80, p < 0.001), momentum (r = 0.80, p < 0.001), and effective regurgitant orifice area (r = 0.78, p < 0.001), with proximal jet size measured in the apical four-chamber view in patients with free jets. The average of jet proximal size in three planes also had good correlation with peak flow rate (r = 0.75, p < 0.001), regurgitant fraction, momentum, and effective regurgitant orifice area (r = 0.74, p < 0.001). In patients with impinging jets, agreement was fair between effective regurgitant orifice (r = 0.65, p < 0.001), peak flow rate (0.65, p < 0.001), and momentum (r = 0.62, p < 0.001) with mean jet proximal size. Jet proximal size obtained with transthoracic color flow mapping is a good semiquantitative tool for measuring tricuspid regurgitation in free jets that correlates well with established measures of the severity and with new parameters available from analysis of the proximal acceleration field. In patients with eccentrically directed wall jets, the correlation weakens but still appears clinically significant.

Trisomy 3 in marginal zone B-cell lymphoma: a study based on cytogenetic analysis and fluorescence in situ hybridization

Trisomy 3 represents the most frequent and consistent chromosomal abnormality characterizing the recently defined entity marginal zone B-cell lymphoma (MZBCL). By cytogenetic analysis and/or fluorescence in situ hybridization (FISH) on interphase nuclei we found in increased copy number of chromosome 3 in 22/36 (61%) successfully analysed cases, including 8/12 cases with extranodal MZBCL, 8/13 cases with nodal MZBCL, and 6/11 patients with splenic MZBCL. Sensitivity of interphase cytogenetics was somewhat higher than that of conventional cytogenetic investigation. Structural chromosomal changes involving at least one chromosome 3 were seen in 11/20 cases with an increased copy number of chromosome 3: +de(3)(p13) was demonstrated in three cases, and was the sole chromosomal abnormality in one of them; +i(3)(q10) was seen in two other patients; and rearrangements involving various breakpoints on the long arm of chromosome 3 were found in the remaining cases. FISH on metaphase spreads confirmed these structural abnormalities and additionally showed two unexpected translocations involving chromosome 3. We conclude that: (1) trisomy 3 occurs in a high proportion of extranodal, nodal and splenic MZBCL; (2) FISH on interphase nuclei is an additional and sensitive tool in detecting an increased copy number of chromosome 3 in MZBCL; (3) additional structural abnormalities involving the long arm of chromosome 3 are frequent but non-recurrent and are perhaps secondary changes; and (4) abnormalities such as +del(3)(pl3) and +i(3)(q10) suggest that genes located on the long arm of chromosome 3 are of particular importance in the pathogenesis of MZBCL.

Signals mediating stimulation of cardiomyocyte glucose transport by the alpha-adrenergic agonist phenylephrine

Phenylephrine, a potent stimulator of cardiomyocyte glucose transport (GT), caused a rapid rise in cytosolic Ca2+ by 30%. Agents inducing a similar Ca2+ response did not stimulate (angiotension II, vasopressin) or inhibited GT by 20% (elevated extracellular Ca2+). Stimulation of GT by phorbol myristate acetate was additive to both phases of phenylephrine's effect (4 min, 60 min). Phenylephrine had no influence on the adenosine 3', 5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) levels. Agents raising cAMP (isoproterenol) or cGMP (e.g., nitroprusside) did not stimulate GT. Wortmannin (inhibitor of 1-phosphatidylinositol 3-kinase) suppressed the action of insulin on GT but not that of phenylephrine. In contrast, the Na+/H+ exchange inhibitor amiloride (which blocks phenylephrine-induced cytosolic alkalinization or even lowers cellular pH) depressed the effect of phenylephrine by 50%, whereas insulin-stimulated GT was little affected. However, raising extracellular pH up to 8.4 failed to increase GT. Lowering pH to 6.8 decreased phenylephrine's effect by 40% whereas insulin-dependent GT was not significantly altered. Clorgyline, tranylcypromine (monoamine oxidase inhibitors), and added catalase suppressed the slow phase of phenylephrine's action, whereas amiloride also affected the fast phase. We conclude that 1) stimulation of cardiomyocyte GT by phenylephrine does not involve cAMP, cGMP, or 1-phosphatidylinositol 3-kinase; 2) protein kinase C activation cannot explain the full extent of stimulation; 3) Ca2+ release or cytosolic alkalinization may be required but is not sufficient to trigger phenylephrine's action, and 4) the slow phase of stimulation is mediated by the monoamine oxidase-dependent degradation of phenylephrine and by the resulting H2O2 formation.

Contraction-independent effects of catecholamines on glucose transport in isolated rat cardiomyocytes

The effects of catecholamines on glucose transport were studied in noncontracting isolated rat cardiomyocytes. alpha-Adrenergic treatment (phenylephrine, or norepinephrine + propranolol) led to an approximately fourfold stimulation of glucose transport in basal cells (no insulin). The effect of phenylephrine was suppressed by the alpha 2-antagonist yohimbine or the beta-antagonist propranolol. The beta-adrenergic agonist isoproterenol partially counteracted the action of phenylephrine (but not that of insulin). Phenylephrine increased glucose transport in two phases with apparent half times of 3.2 and 13.0 min, respectively. Correspondingly, different EC50 values were found after 10 and 45 min on phenylephrine addition (5.0 +/- 1.9 vs. 31.6 +/- 9.6 microM, respectively). Maximal stimulation by phenylephrine was at least partially additive to that of insulin and of other stimulators of glucose transport (e.g., H2O2, vanadate, lithium). Phenylephrine significantly increased the level of cell surface glucose carriers GLUT-1 (1.54-fold) and GLUT-4 (1.78-fold), as assessed by using the specific photolabel 2-N-[4-(1-azi-2,2,2-trifluoroethyl)benzoyl]- 1,3-bis(D-mannos-4-yloxy)propyl-2-amine. In conclusion, catecholamines stimulate cardiomyocyte glucose transport through alpha 1-adrenergic receptors independently or downstream of a contraction-evoked stimulus. This effect is at least partially explained by a recruitment of glucose transporters to the cell surface. The mechanism(s) and/or signals involved differ from those triggered by insulin and insulinomimetic agents.

Left ventricular echocardiographic and histologic changes: impact of chronic unloading by an implantable ventricular assist device

OBJECTIVES

We studied the effects of chronic left ventricular unloading by a ventricular assist device and assessed left ventricular morphologic and histologic changes.

BACKGROUND

The implantable left ventricular assist device has been effective as a "bridge" to cardiac transplantation. Although there are reports documenting its circulatory support, little is known about the effects of chronic left ventricular unloading on the heart itself.

METHODS

We performed intraoperative transesophageal echocardiography at the insertion and explanation of a HeartMate left ventricular assist device in 19 patients with end-stage heart failure. They were supported by the assist device for 3 to 153 days (mean [+/-SD] 68 +/- 33). Measurements were taken retrospectively to obtain left atrial and ventricular diameters and interventricular septal and posterior wall thicknesses. Histologic examinations were made from the left ventricular myocardial specimens of 15 patients at the times of insertion and explanation for heart transplantation. Insertion and explanation specimens were compared qualitatively (0 to 3 scale) for wavy fibers, contraction band necrosis and fibrosis, with quantitative measurement of minimal myocyte diameter across the nucleus.

RESULTS

Left atrial and left ventricular diastolic and systolic diameters decreased immediately after insertion of the left ventricular assist device (from 46 to 35, 63 to 41 and 59 to 36 mm, respectively, all p < 0.001). Left ventricular wall thickness increased from 10 to 14 mm (p < 0.001) for the interventricular septum and from 10 to 13 mm for the posterior wall (p<0.001). No echocardiographic measurements showed significant subsequent changes at the chronic stage. Myocardial histologic findings demonstrated a reduction in myocyte damage (from 1.9 to 0.5, p<0.001, for wavy fiber and from 1.3 to 0.2, p<0.01, for contraction band necrosis) and an increase in fibrosis (from 1.3 to 1.9, p<0.05), but without significant change in myocyte diameter (from 15.6 to 16.8 micrometer, p=0.065).

CONCLUSIONS

Left ventricular unloading with the implantable assist device induces an immediate increase in wall thickness, consistent with the reduction in chamber size, thereby decreasing wall stress. Chronic unloading allows myocardial healing and fibrosis without evidence for ongoing myocyte damage or atrophy. Left ventricular assist device insertion may have a role in "resting" the ventricle for selected patients with heart failure.

Dynamic magnetic resonance imaging assessment of the effect of ventricular wall curvature on regional function in hypertrophic cardiomyopathy

We hypothesized that contraction within the ventricular septum in hypertrophic cardiomyopathy (HC) may be related to its abnormal morphology because ventricular wall stress is related to wall curvature by the Laplace equation. To test this, we studied 17 HC patients with various septal morphologies using dynamic magnetic resonance imaging techniques. Short- and long-axis curvatures of the basal septal and basal lateral walls were determined on cine images as the reciprocal of the radius of the arc best fit to the endocardial contour, which was negative if the wall was convex to the cavity of the left ventricle. Endocardial and epicardial intramyocardial circumferential shortening (% circumferential shortening) was measured in the septal and lateral walls on basal short-axis myocardial tagging images. Septal walls were flatter in the short-axis plane and more convex toward the left ventricular cavity in the long-axis plane than lateral walls, as indicated by smaller short- and long-axis curvatures. Septal percent circumferential shortening was significantly lower than the lateral percent circumferential shortening, suggesting reduced septal contraction. Endocardial and epicardial percent circumferential shortening showed significant positive correlations with wall curvatures. Multiple stepwise linear regression analysis revealed that both short- and long-axis curvatures significantly contributed to percent circumferential shortening (r=0.87 for endocardial and r=0.70 for epicardial, both p<0.0001). In conclusion, wall curvature is related to wall function in HC; the more convex toward the left ventricular cavity the wall is, the less it contracts. Reduced contraction of the septum in HC may be partly due to its abnormal curvature.

Magnetization transfer in magnetic resonance imaging

Two populations of hydrogen protons exist in magnetic resonance imaging: free protons and bound protons. Bound protons do not contribute to normal MR signal because they resonate somewhat off the center frequency of water. A special pulse sequence called magnetization transfer contrast (MTC) was developed to compensate for this off-resonance limitation. A saturation transfer of bound protons occurs during MTC, enabling a transfer of energy to the free proton pool and thereby contributing to the overall MR signal. This article describes MTC, reviews its applications and explains how it improves lesion conspicuity, small vessel detail and background suppression.

Pressure-relieving supports in an ICU

Intensive care wards have a high incidence of pressure sores. This trial, in an eight-bed unit, aimed to compare the cost-effectiveness of constant-low-pressure and alternating-pressure support systems for preventing pressure sores. Patients without sores with a Norton risk score of < 13 were allocated to either alternating- or constant-low-pressure supports according to their hospital number. The cheapest supports were used initially, and changed for more sophisticated types if the patient's pressure areas deteriorated. None of the 23 patients using low-cost alternating-pressure supports developed open sores and only one had to be transferred to a more sophisticated mattress because of persistent erythema. Eleven out of 20 patients on constant-low-pressure mattresses or overlays developed either persistent erythema (three) or sores (eight). Ten were transferred to more expensive support systems. The mean cost of supports per patient in the alternating-pressure group was 44.50 pounds and in the constant-low-pressure group 86.20 pounds.

Acute and long-term effects of thrombolysis after anterior wall acute myocardial infarction with serial assessment of infarct expansion and late ventricular remodeling

This study investigates the impact of thrombolysis on infarct expansion and subsequent left ventricular (LV) remodeling in patients with anterior wall acute myocardial infarction (AMI). We evaluated 51 consecutive patients (24 treated with thrombolysis) with anterior wall AMI by 2-dimensional echocardiography in the following sequence: days 1, 2, 3, and 7, after 3 and 6 weeks, and after 3, 6, and 12 months. LV end-diastolic and end-systolic volume indexes were determined from apical 2- and 4-chamber views using Simpson's biplane formula. Infarct and total LV perimeters were determined in the same views and their ratio expressed as infarct percentage. Infarct expansion was defined as: (1) an increase in infarct percentage and total perimeter >5% on days 2 to 3 in either of the views, or (2) initial infarct percentage >50% with an increase in total perimeter >5% on days 2 to 3. Coronary angiography was performed in 43 patients before discharge, and patency of the infarct-related artery was assessed using Thrombolysis in Myocardial Infarction trial criteria. Infarct expansion was detected in 23 patients. Infarct perimeter steadily decreased in patients with versus without thrombolysis and in patients with patent versus occluded infarct-related arteries. Furthermore, by logistic regression, thrombolysis (p = 0.007) and potency of the infarct-related artery (p = 0.02) were strong negative predictors of expansion, whereas initial infarct perimeter (p = 0.009) was directly associated with subsequent expansion. End-systolic volume index was higher in patients with expansion from day 1 (p = 0.003) through the end of the study (p = 0.021), and end-diastolic volume index was higher in these patients from day 2 (p = 0.012) through 12 months (p = 0.015). Thus thrombolysis, initial infarct size, and infarct-related artery patency are major predictors of infarct expansion after anterior wall AMI.

Impact of wall constraint on velocity distribution in proximal flow convergence zone. Implications for color Doppler quantification of mitral regurgitation

OBJECTIVES

This study sought to elevate the effect of proximal flow constraint induced by the left ventricular wall on the accuracy of calculated flow rates and to assess a possible correction factor to adjust the proximal convergence angle. We further defined under which hydrodynamic and geometric conditions it is necessary to apply the corrected convergence angle.

BACKGROUND

The proximal flow convergence method has been proposed as a new approach to quantify valvular regurgitation. However, significant overestimation of the calculated regurgitant flow rate has been reported, particularly in patients with mitral valve prolapse and severe mitral regurgitation.

METHODS

We used an in vitro flow model and induced various degrees of proximal flow constraint. The accuracy of the proposed convergence angle formula, alpha = tau + 2 tan-1 d/r (d = wall distance; r = isovelocity radius) was tested in vitro and in a three-dimensional numerical simulation.

RESULTS

With a constraining wall near the orifice, overstimulation of regurgitant flow rates was noted and was most significant with the constraining wall positioned closest to the orifice (calculated flow rate [Qc]/true flow rate [Qo] = 1.85 +/- 0.55 [mean +/- SD]). These findings were similar to the results of the numerical simulation. Applying the correction factor nearly completely eliminated the overestimation of the calculated flow rates (cQc), with cQc/Qo = 1.13 +/- 0.25.

CONCLUSIONS

In the presence of a constraining wall, significant overestimation of calculated flow rates is observed when hemispheric symmetry of the flow field is assumed. In this situation, it is necessary to apply the corrected convergence angle formula to improve the accuracy of the proximal flow convergence method.

Serial assessment of left ventricular chamber stiffness after acute myocardial infarction

Left ventricular (LV) systolic function after acute myocardial infarction (AMI) has been the subject of detailed studies during the last decade, but diastolic phenomena during and after AMI are less well understood. Recently, it has been shown that early filling deceleration time accurately predicted LV chamber stiffness in an experimental model. To assess changes of LV stiffness after AMI, we studied 116 consecutive patients with 2-dimensional and Doppler echocardiographic examinations 1, 2, 3, 7, 21, and 42 days after AMI. Coronary angiography was performed in 101 patients. For the entire study group, deceleration time decreased nonsignificantly on day 2 and subsequently increased on days 3 (p = 0.001) and 7 (p = 0.036), returning toward initial values afterward. Deceleration time was shorter in large (peak creatine kinase level >1,000 U/L) versus small infarcts (p = 0.0008) and in patients with anterior versus inferior AMI (p = 0.02); there was no difference between patients with good and poor (< or = 45%) ejection fraction. These data indicate that increased LV stiffness can be detected 24 to 48 hours after AMI, but returns to normal within several days. Chamber stiffness is higher in large and anterior infarcts, but appears to be independent of LV systolic function.

New insights into the reduction of mitral valve systolic anterior motion after ventricular septal myectomy in hypertrophic obstructive cardiomyopathy

To determine the mechanism of reduction of mitral valve systolic anterior motion by myectomy, we examined 33 patients with hypertrophic obstructive cardiomyopathy echocardiographically before and after myectomy. Measurements included outflow tract diameter, the direction of ejection streamline (the angle between the ejection flow and the mitral valve), midventricular fractional area change, and papillary muscle inward excursion in the short-axis image. After myectomy, the outflow tract was enlarged (from 1.2 +/- 0.3 cm to 2.1 +/- 0.4 cm; p < 0.001), and the ejection flow became more parallel to mitral leaflets (from 51 +/- 10 degrees to 28 +/- 8 degrees; p < 0.001), whereas hyperdynamic midventricular fractional area change was reduced (81% +/- 14% to 62% +/- 14%; p < 0.001), and papillary muscle excursion decreased (1.3 +/- 0.3 cm to 0.8 +/- 0.3 cm; p < 0.001). Outflow enlargement and reduced ventricular contraction would decrease the Venturi force. Change of ejection streamline and reduced contraction would decrease the drag force onto the mitral leaflets. Blunted papillary motion would increase the mitral leaflet tension and decrease the effect of drag force on both leaflets. Thus myectomy decreases Venturi and drag forces and appears to reduce systolic anterior motion of the mitral valve.

8-(N,N-diethylamino)octyl 3,4,5-trimethoxybenzoate (TMB-8) acts as a muscarinic receptor antagonist in the epithelial cell line HT29

8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8) is a widely used pharmacological tool to investigate the involvement of intracellular Ca2+ stores in cellular responses. In this study we investigate the effect of TMB-8 as a putative inhibitor of "Ca2+ signalling" in single fura-2 loaded HT29 colonic epithelial cells stimulated by ATP, carbachol (CCH) and neurotensin (NT). TMB-8 effectively inhibited the CCH-induced (100 mumol/l intracellular Ca2+ ([Ca2+]i) transient with an IC50 of 20 mumol/l. However, [Ca2+]i transients induced by other phospholipase C coupled agonists ATP (10 mumol/l, n = 4) and NT (10 nmol/l, n = 4) remained unaffected by TMB-8 (50 mumol/l). The agonist-induced [Ca2+]i transients remained equally unaffected by 100 mumol/l TMB-8 when the stimulatory concentration was reduced to 0.5 mumol/l for ATP (n = 4) or 1 nmol/l for NT (n = 4). The competitive nature of the TMB-8-induced inhibition of the CCH-induced [Ca2+]i transient was demonstrated by examining the agonist at various concentrations in absence and presence of the antagonist. High TMB-8 concentrations (100 mumol/l) alone induced a small [Ca2+]i increase (delta[Ca2+]i: 40 +/- 5 nmol/l, n = 7). We assume that this increase is a consequence of a TMB-8 induced intracellular alkalinization (delta pH: 0.1 +/- 0.02, n = 7) occurring simultaneously with the increase in [Ca2+]i. From these results we draw the following conclusions: (1) In sharp contrast to a large number of other studies, but in agreement with studies in other types of cells, these results substantially challenge the value of the "tool" TMB-8 as an "intracellular Ca2+ antagonist"; (2) TMB-8 acts a muscarinic receptor antagonist at the M3 receptor; (3) TMB-8 does not influence the release of Ca2+ from intracellular stores when IP3 signal transduction is activated by ATP or NT; (4) TMB-8 as a weak organic base alkalinizes the cytosol at high concentrations; and (5) TMB-8 induces small [Ca2+]i transients at higher concentrations.

Herpes simplex virus type 1-mediated up-regulation of IL-12 (p40) mRNA expression. Implications in immunopathogenesis and protection

In this report we investigated whether induction of IL-12 occurs in response to herpes simplex virus (HSV) infection of the mouse eye, which may serve to regulate the nature of the subsequent immune response. The data show early induction and continued maintenance of IL-12 (p40) mRNA in the cornea and draining lymph node upon ocular infection with HSV. Using a very sensitive radioimmunoassay technique, IL-12 (p40) protein also was detected in the cornea upon ocular HSV infection. Unfractionated splenocytes and enriched populations of dendritic cells, macrophages, and neutrophils all responded to HSV infection in vitro by up-regulating the expression of IL-12 (p40) mRNA. However, cultured corneal cells failed to generate IL-12 (p40) upon exposure to HSV. The data indicate that inflammatory cells that infiltrate the cornea in response to HSV-1 infection are the main source of IL-12 in the eye. Our results are consistent with the hypothesis that IL-12 induction in the eye acts as a triggering event that biases HSV-specific immunity to a type 1 T cell response, which, in the environment of the eye, culminates in an immunopathologic disease.

Mechanisms of hemolysis with mitral prosthetic regurgitation. Study using transesophageal echocardiography and fluid dynamic simulation

OBJECTIVES

The aims of this study were to define the hydrodynamic mechanisms involved in the occurrence of hemolysis in prosthetic mitral valve regurgitation and to reproduce them in a numeric simulation model in order to estimate peak shear stress.

BACKGROUND

Although in vitro studies have demonstrated that shear stresses > 3,000 dynes/cm2 are associated with significant erythrocyte destruction, it is not known whether these values can occur in vivo in conditions of abnormal prosthetic regurgitant flow.

METHODS

We studied 27 patients undergoing reoperation for significant mitral prosthetic regurgitation, 16 with and 11 without hemolysis. We classified the origin and geometry of the regurgitant jets by using transesophageal echocardiography. By using the physical and morphologic characteristics defined, several hydrodynamic patterns were simulated numerically to determine shear rates.

RESULTS

Eight (50%) of the 16 patients with hemolysis had paravalvular leaks and the other 8 had a jet with central origin, in contrast to 2 (18%) and 9 (82%), respectively, of the 11 patients without hemolysis (p = 0.12, power 0.38). Patients with hemolysis had patterns of flow fragmentation (n = 2), collision (n = 11) or rapid acceleration (n = 3), whereas those without hemolysis had either free jets (n = 7) or slow deceleration (n = 4) (p < 0.001, power 0.99). Numeric simulation demonstrated peak shear rates of 6,000, 4,500, 4,500, 925 and 950 dynes/cm2 in these five models, respectively.

CONCLUSIONS

The distinct patterns of regurgitant flow seen in these patients with mitral prosthetic hemolysis were associated with rapid acceleration and deceleration or high peak shear rates, or both. The nature of the flow disturbance produced by the prosthetic regurgitant lesion and the resultant increase in shear stress are more important than the site of origin of the flow disturbance in producing clinical hemolysis.

Herpes simplex virus type 1-mediated up-regulation of IL-12 (p40) mRNA expression. Implications in immunopathogenesis and protection

In this report we investigated whether induction of IL-12 occurs in response to herpes simplex virus (HSV) infection of the mouse eye, which may serve to regulate the nature of the subsequent immune response. The data show early induction and continued maintenance of IL-12 (p40) mRNA in the cornea and draining lymph node upon ocular infection with HSV. Using a very sensitive radioimmunoassay technique, IL-12 (p40) protein also was detected in the cornea upon ocular HSV infection. Unfractionated splenocytes and enriched populations of dendritic cells, macrophages, and neutrophils all responded to HSV infection in vitro by up-regulating the expression of IL-12 (p40) mRNA. However, cultured corneal cells failed to generate IL-12 (p40) upon exposure to HSV. The data indicate that inflammatory cells that infiltrate the cornea in response to HSV-1 infection are the main source of IL-12 in the eye. Our results are consistent with the hypothesis that IL-12 induction in the eye acts as a triggering event that biases HSV-specific immunity to a type 1 T cell response, which, in the environment of the eye, culminates in an immunopathologic disease.

Diagnosis of patent foramen ovale by contrast versus color Doppler by transesophageal echocardiography: relation to atrial size

To ascertain the factors related to the transesophageal echocardiographic diagnosis of patent foramen ovale, the primary echocardiographic data were reviewed from 74 patients with that diagnosis. Similar detection rates were observed with contrast echocardiography (82%) and color flow mapping (78%), but contrast was more sensitive in patients with normal-sized atria (94%) and isolated right atrial enlargement (100%) than in those with enlarged left atria, all but three of whom had biatrial enlargement (52%) (p < 0.001 by chi-square test). Doppler flow mapping was less sensitive for normal-sized atria (66%) than for isolated enlarged right atria (81%) and left (bi-) atrial enlargement (96%) (p = 0.024). Patent foramen ovale was directly visualized by two-dimensional echocardiography in 80%, with close agreement to the size of the color flow jet (r = 0.90, delta = 0.1 +/- 0.4 mm); foramen ovale size was related to right atrial area (r = 0.31, p = 0.015). Thus both saline contrast and color flow imaging are necessary to exclude the diagnosis of patent foramen ovale.

Macrozamia toxicosis in a dog

A case of Macrozamia riedlei seed poisoning is described in a young Dachshund. Vomiting and depression commenced within 6 h of ingestion; other signs that developed included severe hepatopathy, jaundice, abdominal pain that was unresponsive to analgesics, severe gastro-intestinal haemorrhage and thrombocytopenia as well as crystalluria and marrow dyserythropoiesis. The dog was euthanased 6 days after ingestion of the seeds.

Prognostic value of dobutamine echocardiography in patients with left ventricular dysfunction

OBJECTIVES

This study sought to establish the prognostic implications of ischemic and viable myocardium identified by dobutamine echocardiography in patients with left ventricular dysfunction.

BACKGROUND

Recent studies have suggested that in patients with viable myocardium identified by positron emission tomography, medical treatment is associated with recurrent cardiac events. Dobutamine echocardiography has been used to identify viable myocardium in patients with left ventricular dysfunction, but the prognostic significance of this test is undefined.

METHODS

One hundred thirty-six consecutive patients (mean [+/- SD] age 67 +/- 7.9 years; 104 men) with moderate or severe left ventricular dysfunction (left ventricular ejection fraction 30 +/- 5%) undergoing dobutamine echocardiography were included in the study. Dobutamine was administered using a standard incremental protocol (5 to 40 micrograms/kg body weight per min intravenously in 3-min stages) with additional atropine (1 mg intravenously) as required. Standard body weight echocardiographic views were digitized on-line and compared using a side-by-side display. Viable myocardium was identified by enhancement of regional function at low dose (< 10 micrograms); scar was diagnosed by akinesia at rest or dyskinesia without change and ischemia as new or worsening dysfunction. One hundred thirty patients (95%) were followed up for 16 +/- 8 months after the original study for major cardiac events (cardiac death, myocardial infarction or severe unstable angina requiring late myocardial revascularization).

RESULTS

No significant complications occurred during dobutamine echocardiography. Viable myocardium was detected in 26 patients (19%), ischemia in 23 (17%), both viability and ischemia in 13 (10%) and scar in 74 (54%). Of 108 patients treated medically, 46 had viable or ischemic myocardium, and 62 had scar only. There were no significant differences in age or other clinical characteristics, stress response, left ventricular dimensions and ejection fraction between the two groups. Cardiac events occurred in 26 medically treated patients (24%): 18 died of cardiac-related causes; 4 had a nonfatal myocardial infarction; and 4 had late revascularization because of unstable angina. The event rate was greater in patients with viable or ischemic myocardium than those with scar (43% vs. 8%, p = 0.01 by log-rank test). In a Cox regression model, the presence of viable or ischemic myocardium was found to predict subsequent events (relative risk 3.51, p = 0.02) independently of ejection fraction and age.

CONCLUSIONS

Viable or ischemic myocardium detected at dobutamine echocardiography in patients with left ventricular dysfunction is associated with an adverse prognosis, independent of age and ejection fraction.