A semiautomated objective technique for applying the proximal isovelocity surface area method to quantitate mitral regurgitation: Clinical studies with the digital flow map

BACKGROUND

Clinical application of the color Doppler proximal isovelocity surface area (PISA) method to quantify mitral regurgitation (MR) has been limited by the often inaccurate assumption that isovelocity surfaces are hemispheric. This study applied an objective method for selecting the region where the hemispheric geometry holds best on the basis of mathematic analysis of results at different distances from the orifice. We aimed to demonstrate this approach can be applied accurately in the clinical setting and can be semiautomated to promote routine use by extracting velocities from the digital Doppler output and then performing all the calculations automatically.

METHODS

In 75 patients with isolated MR, centerline velocities (V(r)) at each distance (r) from the orifice in the proximal flow field were extracted digitally. The automated analysis calculated peak MR flow rates as 2pir(2)V(r) and plotted these against their respective velocities. The optimal value for peak flow rate was obtained mathematically at the site where the slope of this curve was minimal (least inaccuracy). This value was combined with continuous wave Doppler data to provide regurgitant stroke volume (RSV) and orifice area (ROA), which were compared with quantitative Doppler in 75 patients and angiography in 42.

RESULTS

RSV and ROA by this optimized, semiautomated PISA method correlated and agreed well with values from quantitative Doppler (y = 0.9x + 1.9, r = 0.90, standard error of the estimate [SEE] = 8.1 mL, mean difference = -0.7 +/- 8.5 mL for RSV; y = 0.9x + 0.02, r = 0.90, SEE = 0.048 cm(2), mean difference = -0.005 +/- 0.1 cm(2) for ROA) and correlated well with angiography (rho = 0.90 for both RSV and ROA).

CONCLUSIONS

This objective PISA method for quantifying MR is accurate in the clinical setting and has been semiautomated by use of analysis of digital velocity data to provide a rapid and practical technique suitable to facilitate more extensive application in routine practice.

Tetrahydrobiopterin enhances apoptotic PC12 cell death following withdrawal of trophic support

(6R)-Tetrahydro-l-biopterin (BH(4)) is the rate-limiting cofactor in the production of catecholamine and indoleamine neurotransmitters and is also essential for the synthesis of nitric oxide by nitric-oxide synthase. We have previously reported that BH(4) administration induces PC12 cell proliferation and that nerve growth factor- or epidermal growth factor-induced PC12 cell proliferation requires the elevation of intracellular BH(4) levels. We show here that BH(4) accelerates apoptosis in undifferentiated PC12 cells deprived of serum and in differentiated neuron-like PC12 cells after nerve growth factor withdrawal. Increased production of catecholamines or nitric oxide cannot account for the enhancement of apoptosis by BH(4). Furthermore, increased calcium influx by exogenous BH(4) administration is not involved in the BH(4) proapoptotic effect. Our data also argue against the possibility that increased oxidative stress, due to BH(4) autoxidation, is responsible for the observed BH(4) effects. Instead, they are consistent with the hypothesis that BH(4) induces apoptosis by increasing cell cycle progression. Elevation of intracellular BH(4) during serum withdrawal increased c-Myc (and especially Myc S) expression earlier than serum withdrawal alone. Furthermore, N-acetylcysteine and the cyclin-dependent kinase inhibitor olomoucine ameliorated the BH(4) proapoptotic effect. These data suggest that BH(4) affects c-Myc expression and cell cycle-dependent events, possibly accounting for its effects on promoting cell cycle progression or apoptosis.

Objective detection and localization of multiple sclerosis lesions on magnetic resonance brainstem images: validation with auditory evoked potentials

To develop an objective method for detecting multiple sclerosis (MS) brainstem lesions, magnetic resonance (MR) images (multiple planar, spin-echo, acquired in three planes of section) of sixteen MS patients and fourteen normal subjects were analyzed with an algorithm that detected regions with a relatively increased intensity on both a spin-echo image and a T2 image. To be considered a lesion, such regions had to overlap in at least two orthogonal planes. Using a digitized atlas of the human brainstem, the lesion locations were mapped with respect to the brainstem anatomy. This method was evaluated by comparing the location of MS lesions with the brainstem auditory evoked potentials obtained from these subjects. Brainstem lesions were detected in five MS patients; four had lesions impinging upon the auditory system and one did not. All four had abnormal evoked potentials. The fourteen normal subjects, the one MS patient with brainstem lesions outside the auditory pathway, and the eleven other MS patients with no brainstem lesions all had normal evoked potentials. The requirement that lesions be detected in at least two planes of section greatly improved the specificity of the algorithm. The consistency between the MR and brainstem auditory evoked potentials results supports the validity of this imaging analysis algorithm for objectively localizing brainstem lesions.

Mechanism of ischemic mitral regurgitation with segmental left ventricular dysfunction: three-dimensional echocardiographic studies in models of acute and chronic progressive regurgitation

OBJECTIVES

This study aimed to separate proposed mechanisms for segmental ischemic mitral regurgitation (MR), including left ventricular (LV) dysfunction versus geometric distortion by LV dilation, using models of acute and chronic segmental ischemic LV dysfunction evaluated by three-dimensional (3D) echocardiography.

BACKGROUND

Dysfunction and dilation-both mechanisms with practical therapeutic implications-are difficult to separate in patients.

METHODS

In seven dogs with acute left circumflex (LCX) coronary ligation, LV expansion was initially restricted and then permitted to occur. In seven sheep with LCX branch ligation, LV expansion was also initially limited but became prominent with remodeling over eight weeks. Three-dimensional echo reconstruction quantified mitral apparatus geometry and MR volume.

RESULTS

In the acute model, despite LV dysfunction with ejection fraction = 23 +/- 8%, MR was initially trace with limited LV dilation, but it became moderate with subsequent prominent dilation. In the chronic model, MR was also initially trace, but it became moderate over eight weeks as the LV dilated and changed shape. In both models, the only independent predictor of MR volume was increased tethering distance from the papillary muscles (PMs) to the anterior annulus, especially medial and posterior shift of the ischemic medial PM, measured by 3D reconstruction (r2 = 0.75 and 0.86, respectively). Mitral regurgitation volume did not correlate with LV ejection fraction or dP/dt.

CONCLUSIONS

Segmental ischemic LV contractile dysfunction without dilation, even in the PM territory, fails to produce important MR. The development of MR relates strongly to changes in the 3D geometry of the mitral apparatus, with implications for approaches to restore a more favorable configuration.

Harvested porcine mitral xenograft fixation: impact on fluid dynamic performance

BACKGROUND AND AIM OF THE STUDY

Recent developments suggest that stentless bioprosthetic mitral valve heterografts should be considered in order to optimize valve hydrodynamics. The fixation process alters the mechanical properties of tissue. This study investigates the changes in mitral valve morphology and hemodynamic performance following fixation.

METHODS

Porcine mitral valves were excised and attached to a physiological annular ring. Mitral valve function was studied in vitro with a rigid transparent left heart model, allowing transverse and sagittal views. Initial experiments were performed with fresh valves under physiological conditions. Three different papillary muscle positions were used, and each was recorded. After glutaraldehyde fixation, genipin fixation, and cryopreservation, the valves were re-studied while maintaining cardiac output. Performance characteristics before and after fixation were obtained from hydrodynamic pressure and flow data, high-speed video camera, digital video, Doppler ultrasound, and three-dimensional papillary muscle force measurements. Morphology changes were detected by detailed anatomic measurements of the valves before and after fixation.

RESULTS

Valve length was reduced by 18.5% after fixation with genipin (p <0.001), but not with glutaraldehyde. Cryopreserved valves showed no statistically significant changes in morphology or hydrodynamic performance after preservation. The forward flow opening area was reduced by 12.2% (p <0.001) after glutaraldehyde fixation, and by 32.3% (p = 0.004) after genipin fixation. Thus, maximal forward flow velocity was increased by 33.3% (p = 0.008) after glutaraldehyde fixation and by 52.8% (p = 0.001) after genipin fixation. The flow acceleration was consistent with a funnel shape of the fixed valves causing important flow contraction beyond the orifice (vena contracta). The papillary muscle force increased with apically posterior papillary muscle displacement by 20.4% (p = 0.001) and 101.5% (p <0.001) after glutaraldehyde and genipin fixation, respectively, and total regurgitant volume was increased by 91.6% (p <0.001) and 117.3% (p <0.001), respectively. The work required by the heart simulator to maintain a constant cardiac output at constant vascular resistance increased by 24.2% (p = 0.003) and 34.2% (p = 0.004) after glutaraldehyde and genipin fixation, respectively.

CONCLUSION

The present study shows that chemical fixation of porcine mitral valves adversely affects the hemodynamics of the valves, increasing overall workload. The effects were more severe after fixation with genipin than with glutaraldehyde. This suggests the need to explore other fixation agents to optimize valvular cardiac function. Cryopreservation had no detrimental effects on valvular hemodynamic performance.

Atrioventricular nodal versus atrioventricular supraventricular reentrant tachycardias: characterization by an integrated Doppler electrophysiological hemodynamic study

During reentrant supraventricular tachycardias involving the atrioventricular node (AVN-SVT) or an AV bypass tract (AV-SVT), atrial pressure increases. While in AVN-SVT this increase relates to atrial contraction during ventricular systole, the mechanism remains unclear in AV-SVT. This study sought to clarify this mechanism. During 11 AVN-SVTs and 9 AV-SVTs, anterograde flow through the AV valves and retrograde flow in the pulmonary and hepatic veins were studied by pulsed-wave (PW) Doppler measuring the time interval between the ECG-R wave and (1) the end of venous retrograde flows, and (2) the beginning of valvular anterograde flows. The positive or negative difference between these two time intervals guided recognizing the atrial contraction against open or closed AV valves. Intracavitary pressures and cardiac index were also measured. During AVN-SVTs, venous retrograde flows always ended before the anterograde valvular flows, indicating atrial contraction against closed AV valves. During AV-SVTs, pulmonary retrograde flow ended before the beginning of mitral anterograde flow in five cases, began before but ended during the anterograde flow in three cases, and overlapped to the anterograde flow in one case. A corresponding behavior was observed at the right side of the heart. In both SVTs, atrial pressures increased and end-diastolic ventricular pressure and cardiac index decreased similarly. During AVN-SVT, the atrial contraction always occurs against closed AV valves, and during AV-SVT it generally occurs against totally or partially closed AV valves, explaining similar atrial pressure and cardiac index changes in both SVTs.

Transmitral Doppler: a new transthoracic contrast method for patent foramen ovale detection and quantification

OBJECTIVES

This study compared a new transthoracic echocardiographic (TTE) method for detection of right to left bubble passage, transmitral Doppler (TMD), against two-dimensional (2D) TTE contrast study and the gold standard, of transesophageal echocardiography (TEE), and assessed its utility in quantitative assessment of patent foramen ovales (PFO).

BACKGROUND

Current TTE methods are relatively insensitive in PFO detection and do not allow quantitative assessment of right to left shunt.

METHODS

In 44 patients (59 years, range 34 to 76 years) saline contrast and color Doppler studies were performed in three conditions--TTE TMD, TTE 2D and TEE. Bubble transit on the TMD was measured semiquantitatively by a visual bubble score and objectively by integrating the acoustic power within the mitral velocity envelope.

RESULTS

By TEE it was determined that 17 patients (39%) had PFOs; 16 had right to left contrast passage, and only 1 had left to right flow by color Doppler. Against TEE contrast study, the sensitivity of TMD and 2D contrast studies were 100% and 75%, respectively, with specificity of 96% and 100%. Greater than 10 bubbles on a single beat of the resting contrast TMD identified patients with a maximum resting TEE PFO opening diameter >2 mm with 78% sensitivity and 100% specificity. There was a strong correlation (r2 = 0.72, p<0.01) between the TMD acoustic power and PFO opening diameter.

CONCLUSIONS

Transmitral Doppler is a sensitive and specific method for TTE PFO detection that allows quantification of right to left bubble passage and may obviate the need for TEE in many patients after stroke.

Quantitation of ventricular size and function: principles and accuracy of transthoracic rotational scanning

Two-dimensional echocardiography is a readily applicable method for the quantification of ventricular volumes. However, it is limited by assumptions regarding ventricular shape. Three-dimensional echocardiography has emerged as a more accurate and reproducible approach to ventricular volume and functional assessment compared with two-dimensional echocardiography. We review the principles of transthoracic rotational scanning and its clinical application for quantitative assessment of ventricular volume and function.

Transesophageal echocardiographic description of the mechanisms of aortic regurgitation in acute type A aortic dissection: implications for aortic valve repair

OBJECTIVES

The purpose of this study was to use transesophageal echocardiography (TEE) to define the mechanisms of aortic regurgitation (AR) in acute type A aortic dissection so as to assist the surgeon in identifying patients with mechanisms of AR suitable for valve preservation.

BACKGROUND

Significant AR frequently complicates acute type A aortic dissection necessitating either aortic valve repair or replacement at the time of aortic surgery. Although direct surgical inspection can identify intrinsically normal leaflets suitable for repair, it is preferable for the surgeon to correlate aortic valve function with the anatomy prior to thoracotomy.

METHODS

We studied 50 consecutive patients with acute type A aortic dissection in whom preoperative TEE findings were considered by the surgeons in planning aortic valve surgery. Six patients did not undergo surgery (noncandidacy or refusal) and one patient had had a prior aortic valve replacement and therefore was excluded from the analysis.

RESULTS

Twenty-seven patients had no or minimal AR and 22 had moderate or severe AR. In all, there were 16 with intrinsically normal leaflets who had AR due to one or more correctable aortic valve lesion: incomplete leaflet closure due to leaflet tethering in a dilated aortic root in 7; leaflet prolapse due to disrupted leaflet attachments in 8; and dissection flap prolapse through the aortic valve orifice in 5. Of these 16 patients, 15 had successful aortic valve repair whereas just 1 underwent aortic valve replacement after a complicated intraoperative course (unrelated to the aortic valve). Nine patients underwent aortic valve replacement for nonrepairable abnormalities, including Marfan's syndrome in four, bicuspid aortic valve in four, and aortitis in one. In patients undergoing aortic valve repair, follow-up transthoracic echocardiography at a median of three months revealed no or minimal residual AR, and clinical follow-up at a median of 23 months showed that none required aortic valve replacement.

CONCLUSIONS

When significant AR complicates acute type A aortic dissection, TEE can define the severity and mechanisms of AR and can assist the surgeon in identifying patients in whom valve repair is likely to be successful.

Auditory dysfunction in stroke

The auditory and vestibular systems share the same end organ and cranial nerve, yet vestibular signs and symptoms are common with stroke, whereas hearing disturbances are much less frequent. Several reasons would appear to account for this striking dissimilarity. One is that the auditory pathway is less ubiquitous than the vestibular pathways. The likelihood that a stroke involves the auditory pathway is, therefore, less on this basis alone. A second difference, to our knowledge not previously reported, is that the auditory pathway is often spared by the most common strokes. This is because major parts of the auditory pathway, such as the cochlear nucleus, inferior colliculus and medial geniculate body, have multiple sources of blood supply. A third well-recognized factor is the redundancy of the central auditory system and its strong bilateral representation above the level of the cochlear nuclei. Consequently, rostral to the cochlear nuclei gross deficits in hearing, such as those measured by standard pure-tone audiometry and speech discrimination, only occur if lesions are bilateral. Furthermore, widespread bilateral lesions of the auditory system typically render the patient unable to respond or are incompatible with life. In contrast, language disorders are more frequent because language is usually unilaterally represented in the cortex. Certainly, cerebral stroke often includes the auditory system, resulting in various types of auditory disorders, but most hemispherical lesions produce subtle hearing dysfunctions that can only be detected with sophisticated psychoacoustic and electrophysiological testing. The purpose of this review is to provide an overview of the auditory system and its blood supply and to review how auditory processing can be affected by stroke. Psychoacoustic and electrophysiological test procedures for identifying lesions in the central auditory system are described. The literature of hearing disorders due to stroke is reviewed and illustrative cases are presented.

The power-velocity integral at the vena contracta: A new method for direct quantification of regurgitant volume flow

BACKGROUND

Noninvasive quantification of regurgitation is limited because Doppler measures velocity, not flow. Because backscattered Doppler power is proportional to sonified blood volume, power times velocity should be proportional to flow rate. Early studies, however, suggested that this held only for laminar flow, not for regurgitant jets, in which turbulence and fluid entrainment augment scatter. We therefore hypothesized that this Doppler power principle can be applied at the proximal vena contracta, where flow is laminar before entrainment, so that the power-times-velocity integral should vary linearly with flow rate and its time integral with stroke volume (SV).

METHODS AND RESULTS

This was tested in vitro with steady and pulsatile flow through 0.07- to 0.8-cm(2) orifices and in 36 hemodynamic stages in vivo, replacing the left atrium with a rigid chamber and column for direct visual recording of mitral regurgitant SV (MRSV). In 12 patients, MRSV was compared with MRI mitral inflow minus aortic outflow and in 11 patients with 3D echo left ventricular ejection volume-Doppler aortic forward SV. Vena contracta power in the narrow high-velocity spectrum from a broad measuring beam was calibrated against that from a narrow reference beam of known area. Calculated and actual flow rates and SV correlated well in vitro (r=0.99, 0.99; error=-1.6+/-2.5 mL/s, -2. 4+/-2.9 mL), in vivo (MRSV: r=0.98, error=0.04+/-0.87 mL), and in patients (MRSV: r=0.98, error=-2.8+/-4.5 mL).

CONCLUSIONS

The power-velocity integral at the vena contracta provides an accurate direct measurement of regurgitant flow, overcoming the limitations of existing Doppler techniques.

Truncated dipeptidyl peptidase IV is a potent anti-adhesion and anti-metastasis peptide for rat breast cancer cells

A novel adhesion receptor/ligand pair was shown recently to mediate lung vascular arrest and metastasis of rat breast cancer cells. The interacting adhesion molecules are endothelial dipeptidyl peptidase IV (DPP IV) and tumor cell surface-associated, polymeric fibronectin (FN). A truncated DPP IV (DPP IV(31-767): amino acids 31-767) in which the FN-binding site is preserved is shown here to mask the breast cancer cell surface-associated FN complexes, causing a dose-dependent inhibition of adhesion to endothelial DPP IV and impeding lung colony formation by approximately 80%. Since surface accumulation of FN is chiefly occurring during dissemination in the blood and since many cancer cell types have surface receptors by which they may initiate FN accumulation on their surfaces, the present anti-metastatic treatment modality may extend its efficacy farther than appreciated by this study.

Geometric distribution of chordae tendineae: an important anatomic feature in mitral valve function

BACKGROUND AND AIM OF THE STUDY

This study examined the geometric distribution of chordae tendineae and their importance in compensating for papillary muscle (PM) displacement.

METHODS

Anatomic, chordal mechanics and hemodynamic measurements were performed with porcine mitral valves. For hemodynamic measurements, physiological pulsatile flow conditions were maintained, and PM positions varied. Leaflet coaptation was documented by 2-D echocardiography, and regurgitation measured directly.

RESULTS

Anatomic measurements showed the sum of marginal leaflet and marginal chordal lengths to exceed basal chordal length (1.8+/-0.4 versus 2.8+/-0.7 cm for anterior leaflets; 1.6+/-0.3 versus 2.5+/-0.6 cm for posterior leaflets). Triangular structures existed between basal chordae and marginal chordae with the marginal leaflet as the third side. Basal chordae resisted apical PM displacement in static experiments, while marginal chordae governed leaflet closure in hemodynamic experiments. Under pulsatile flow conditions, apical PM displacement decreased leaflet coaptation length and increased regurgitation (9.4+/-2.1 versus 4.0+/-1.6 ml). When marginal chordae were fused to the basal chordae, eliminating the role of the marginal chordae, severe regurgitation resulted (28.5+/-5.0 ml with apical PM displacement).

CONCLUSION

Based on triangular structures involving the basal and marginal chordae, a compensatory mechanism was described which explains how the severity of mitral regurgitation can vary following PM displacement. Basal chordae provide a constant connection between the annulus and papillary muscles, while marginal chordae maintain marginal leaflet flexibility, governing proper valve closure. This study relates chordal distribution to normal valve function, and provides a better understanding of breakdown in valve function under pathophysiological conditions.

Design of a new surgical approach for ventricular remodeling to relieve ischemic mitral regurgitation: insights from 3-dimensional echocardiography

BACKGROUND

Mechanistic insights from 3D echocardiography (echo) can guide therapy. In particular, ischemic mitral regurgitation (MR) is difficult to repair, often persisting despite annular reduction. We hypothesized that (1) in a chronic infarct model of progressive MR, regurgitation parallels 3D changes in the geometry of mitral leaflet attachments, causing increased leaflet tethering and restricting closure; therefore, (2) MR can be reduced by restoring tethering geometry toward normal, using a new ventricular remodeling approach based on 3D echo findings.

METHODS AND RESULTS

We studied 10 sheep by 3D echo just after circumflex marginal ligation and 8 weeks later. MR, at first absent, became moderate as the left ventricle (LV) dilated and the papillary muscles shifted posteriorly and mediolaterally, increasing the leaflet tethering distance from papillary muscle tips to the anterior mitral annulus (P<0.0001). To counteract these shifts, the LV was remodeled by plication of the infarct region to reduce myocardial bulging, without muscle excision or cardiopulmonary bypass. Immediately and up to 2 months after plication, MR was reduced to trace-to-mild as tethering distance was decreased (P<0.0001). LV ejection fraction, global LV end-systolic volume, and mitral annular area were relatively unchanged. By multiple regression, the only independent predictor of MR was tethering distance (r(2)=0.81).

CONCLUSIONS

Ischemic MR in this model relates strongly to changes in 3D mitral leaflet attachment geometry. These insights from quantitative 3D echo allowed us to design an effective LV remodeling approach to reduce MR by relieving tethering.

Myocardial perfusion and wall motion in infarction border zone: assessment by myocardial contrast echocardiography

Several mechanisms have been proposed to explain the decreased wall motion (WM) at the borders of myocardial infarction (MI). We used myocardial contrast echocardiography (MCE) to investigate the relation of perfusion to WM in infarcted border zones (BZs) 6 weeks after MI in 5 sheep. After quantifying the extent of WM abnormality and the perfusion defect, normal (NL), infarcted, and BZs were defined. Peak intensity after contrast was measured in acoustic units (AU). Radiolabeled microspheres were injected to measure regional blood flow. The heart was stained with 2,3, 5-triphenyltetrazolium chloride (TTC). The perfusion defect on MCE was 33% +/- 7% of the total myocardial area and correlated well with TTC (r = 0.92, P <.03). The BZ was 8% +/- 5% of the total myocardial area. Peak intensity after contrast was decreased in MI compared with BZ and NL (MI: 2.5 +/- 1.9 AU, BZ: 8.0 +/- 3.8 AU, P <.005; NL: 10.2 +/- 6.9 AU, P <.02) and comparable in NL and BZ. The blood flow measured by microspheres was not different in NL and BZ but was decreased in MI (NL: 1.6 mL/g/min, BZ: 1.5 +/- 0.5 mL/g/min, MI: 0.7 +/- 0.5 mL/g/min; P <.0001). In this model of chronic ovine MI, the BZ was small and its perfusion was preserved. These findings support the hypothesis that tethering of normal myocardial segments explains the abnormal wall motion noted at the borders of MI.

Sound lateralization and interaural discrimination. Effects of brainstem infarcts and multiple sclerosis lesions

Subjects with brainstem lesions due to either an infarct or multiple sclerosis (MS) underwent two types of binaural testing (lateralization testing and interaural discrimination) for three types of sounds (clicks and high and low frequency narrow-band noise) with two kinds of interaural differences (level and time). Two major types of abnormalities were revealed in the lateralization performances: perception of all stimuli, regardless of interaural differences (time and/or level) in the center of the head (center-oriented), or lateralization of all stimuli to one side or the other of the head (side-oriented). Similar patterns of abnormal lateralization (center-oriented and side-oriented) occurred for MS and stroke patients. A subject's pattern of abnormal lateralization testing was the same regardless of the type of stimulus or type of interaural disparity. Lateralization testing was a more sensitive test than interaural discrimination testing for both types of subjects. Magnetic resonance image (MRI) scanning in three orthogonal planes of the brainstem was used to detect lesions. A semi-automated algorithm superimposed the auditory pathway onto each MRI section. Whenever a lesion overlapped the auditory pathway, some binaural performance was abnormal and vice versa. Given a lateralization test abnormality, whether the pattern was center-oriented or side-oriented was mainly determined by lesion site. Center-oriented performance was principally associated with caudal pontine lesions and side-oriented performance with lesions rostral to the superior olivary complex. For lesions restricted to the lateral lemniscus and/or inferior colliculus, whether unilateral or bilateral, just noticeable differences (JNDs) were nearly always abnormal, but for caudal pontine lesions JNDs could be normal or abnormal. MS subjects were more sensitive to interaural time delays than interaural level differences particularly for caudal pontine lesions, while stroke patients showed no differential sensitivity to the two kinds of interaural differences. These results suggest that neural processing of binaural stimuli is multilevel and begins with independent interaural time and level analyzers in the caudal pons.

Analysis of shape and motion of the mitral annulus in subjects with and without cardiomyopathy by echocardiographic 3-dimensional reconstruction

The shape and dynamics of the mitral annulus of 10 patients without heart disease (controls), 3 patients with dilated cardiomyopathy, and 5 patients with hypertrophic obstructive cardiomyopathy and normal systolic function were analyzed by transesophageal echocardiography and 3-dimensional reconstruction. Mitral annular orifice area, apico-basal motion of the annulus, and nonplanarity were calculated over time. Annular area was largest in end diastole and smallest in end systole. Mean areas were 11.8 +/- 2.5 cm(2) (controls), 15.2 +/- 4.2 cm(2) (dilated cardiomyopathy), and 10.2 +/- 2.4 cm(2) (hypertrophic cardiomyopathy) (P = not significant). After correction for body surface, annuli from patients with normal left ventricular function were smaller than annuli from patients with dilated cardiomyopathy (5.9 +/- 1.2 cm(2)/m(2) vs 7.7 +/- 1.0 cm(2)/m(2); P <.02). The change in area during the cardiac cycle showed significant differences: 23.8% +/- 5.1% (controls), 13.2% +/- 2.3% (dilated cardiomyopathy), and 32.4% +/- 7.6% (hypertrophic cardiomyopathy) (P <.001). Apico-basal motion was highest in controls, followed by those with hypertrophic obstructive and dilated cardiomyopathy (1.0 +/- 0.3 cm, 0.8 +/- 0.2 cm, 0.3 +/- 0.2 cm, respectively; P <.01). Visual inspection and Fourier analysis showed a consistent pattern of anteroseptal and posterolateral elevations of the annulus toward the left atrium. In conclusion, although area changes and apico-basal motion of the mitral annulus strongly depend on left ventricular systolic function, nonplanarity is a structural feature preserved throughout the cardiac cycle in all three groups.

Evidence of deprenyl-insensitive apoptosis of nigral dopamine neurons during development

Apoptosis of dopamine neurons occurs naturally in the substantia nigra during development, culminating in approximately 30% loss of these cells during the perinatal period. Deprenyl, independent of its monoamine oxidase (MAO)-B inhibitory properties, can prevent dopamine neuronal apoptosis in models of neurodegeneration. Our current study demonstrate that apoptotic death of dopamine neurons during development is insensitive to daily treatment of pregnant mothers and then newborns with deprenyl (0.1, 1, or 10 mg/kg). This result is not due to poor crossing of the placental and blood-brain barriers, since deprenyl caused a dose-dependent inhibition of brain MAO-B activity in pups at birth. Determining the pathway(s) leading to deprenyl-insensitive apoptosis of nigral dopamine neurons in development may shed light on mechanisms underlying the premature death of dopamine neurons in neurodegenerative disorders.

C-Reactive protein predicts all-cause and cardiovascular mortality in hemodialysis patients

Hypoalbuminemia predicts death in dialysis patients. Although hypoalbuminemia has been attributed to malnutrition, evidence of inflammation (C-reactive protein [CRP] and cytokine levels) has recently been recognized to predict albumin concentration in dialysis patients. We measured CRP and albumin levels in October 1995 in 91 hemodialysis (HD) patients. During a 34-month follow-up period, we determined the incidence and cause of death. Patients were divided into four groups based on serum albumin levels (<3.5 [lowest quartile], 3.5 to 3.8, 3.9 to 4.0, and >4.0 g/dL [highest quartile]). Survival differed among the four groups (P = 0.0063). Patients with albumin levels greater than 4.0 g/dL had the greatest survival. Kaplan-Meier survival estimates of patients from varying CRP quartiles (<2.6, 2.6 to 5.2, 5.3 to 11.5, and >11.5 microg/mL) differed among the four groups (P < 0.0001). The group with the greatest CRP level (>11.5 microg/mL) had the lowest survival. Multivariate analysis using the Cox proportional hazards model showed that only CRP level (chi-square = 21.11; P < 0.0001) and age (chi-square = 5.44; P = 0.020) predicted death. Albumin level (chi-square = 0.16; P = 0.69) was not predictive. Only when CRP was excluded from the model did low serum albumin level (chi-square = 12. 04; P = 0.0004) predict death. CRP level (chi-square = 16.79; P < 0. 0001) and age (chi-square = 6.38; P = 0.012) also superceded albumin level (chi-square = 0.45; P = 0.51) in predicting cardiovascular mortality. Although values for blood urea nitrogen, creatinine, and normalized protein catabolic rate were significantly less among patients who died, these parameters, as well as cholesterol level and diabetes, were not important predictors of death in multivariate analysis. The acute-phase response or the cause of the acute-phase response is largely responsible for the effect of hypoalbuminemia on mortality in HD patients.

Iron reduction before and during interferon therapy of chronic hepatitis C: results of a multicenter, randomized, controlled trial

Patients with chronic hepatitis C and low serum and hepatic iron stores may have an improved response to interferon (IFN). We tested whether iron reduction before and during IFN therapy would lead to an improved sustained biochemical and virological response compared with IFN alone. Eighty-two previously untreated patients with chronic hepatitis C were randomized to either: group A IFN-alpha2b 3 MU 3 times per week for 6 months, or group B iron reduction before and during IFN-alpha2b 3 MU 3 times per week for 6 months. Group B patients had lower mean serum alanine transaminase (ALT) levels than group A patients during treatment and follow-up. Group B patients had significantly lower mean hepatitis C virus (HCV)-RNA levels at treatment weeks 4 and 12 (P <.05). Serum HCV RNA was undetectable at the end of treatment in 15 group B patients compared with 7 group A patients (P =.03); 7 group B patients and 3 group A patients had persistently undetectable serum HCV RNA 24 weeks after the end of therapy (P =.20). Paired pre- and posttreatment liver biopsies in 18 group B patients demonstrated significant improvements in 2 of the 3 inflammation scores of the Knodell histological activity index (P <. 05). No changes occurred in the paired biopsies from 15 group A patients. We conclude that iron reduction via therapeutic phlebotomy improves the end-of-treatment virological and histological response to short-term IFN therapy. Additional studies are needed to determine if iron reduction in combination with higher doses or longer duration of IFN may be of benefit.

Retinoic acid-induced blr1 expression promotes ERK2 activation and cell differentiation in HL-60 cells

Retinoids are known to induce the differentiation and cell cycle arrest of human myeloid leukemia cells in vitro. Differential display was used to identify putative early regulatory genes that are differentially expressed in HL-60 human promyelocytic leukemia cells treated with retinoic acid. One of the cDNAs cloned encodes sequences identifying Burkitt's lymphoma receptor 1 (BLR1), a recently described chemokine receptor. Northern blot analysis demonstrates that blr1 mRNA expression increases within 9 h of retinoic acid treatment, well before functional differentiation or G(1)/G(0) growth arrest at 48 h or onset of morphological changes, suggesting a possible regulatory function. The expression of blr1 mRNA is transient, peaking at 72 h when cells are differentiated. blr1 mRNA also is induced by other differentiation-inducing agents, 1alpha,25-dihydroxyvitamin D(3) and DMSO. Induction of blr1 mRNA by retinoic acid is not blocked by the protein synthesis inhibitor cycloheximide. In HL-60 cells stably transfected with blr1 cDNA, ectopic expression of blr1 causes an increase in ERK2 MAPK activation and promotes retinoic acid-induced G(1)/G(0) growth arrest and cell differentiation. The early expression of blr1 mRNA during differentiation, its ability to increase ERK2 activation, and its enhancement of retinoic acid-induced differentiation suggest that blr1 expression may be involved in retinoic acid-induced HL-60 differentiation.

Lateralized tinnitus studied with functional magnetic resonance imaging: abnormal inferior colliculus activation

Tinnitus, the perception of sound in the absence of external stimuli, is a common and often disturbing symptom that is not understood physiologically. This paper presents an approach for using functional magnetic resonance imaging (fMRI) to investigate the physiology of tinnitus and demonstrates that the approach is effective in revealing tinnitus-related abnormalities in brain function. Our approach as applied here included 1) using a masking noise stimulus to change tinnitus loudness and examining the inferior colliculus (IC) for corresponding changes in activity, 2) separately considering subpopulations with particular tinnitus characteristics, in this case tinnitus lateralized to one ear, 3) controlling for intersubject differences in hearing loss by considering only subjects with normal or near-normal audiograms, and 4) tailoring the experimental design to the characteristics of the tinnitus subpopulation under study. For lateralized tinnitus subjects, we hypothesized that sound-evoked activation would be abnormally asymmetric because of the asymmetry of the tinnitus percept. This was tested using two reference groups for comparison: nontinnitus subjects and nonlateralized tinnitus subjects. Binaural noise produced abnormally asymmetric IC activation in every lateralized tinnitus subject (n = 4). In reference subjects (n = 9), activation (i.e., percent change in image signal) in the right versus left IC did not differ significantly. Compared with reference subjects, lateralized tinnitus subjects showed abnormally low percent signal change in the IC contralateral, but not ipsilateral, to the tinnitus percept. Consequently, activation asymmetry (i.e., the ratio of percent signal change in the IC ipsilateral versus contralateral to the tinnitus percept) was significantly greater in lateralized tinnitus subjects as compared with reference subjects. Monaural noise also produced abnormally asymmetric IC activation in lateralized tinnitus subjects. Two possible models are presented to explain why IC activation was abnormally low contralateral to the tinnitus percept in lateralized tinnitus subjects. Both assume that the percept is associated with abnormally high ("tinnitus-related") neural activity in the contralateral IC. Additionally, they assume that either 1) additional activity evoked by sound was limited by saturation or 2) sound stimulation reduced the level of tinnitus-related activity as it reduced the loudness of (i.e., masked) the tinnitus percept. In summary, this work demonstrates that fMRI can provide objective measures of lateralized tinnitus and tinnitus-related activation can be interpreted at a neural level.

Inactivation of p53 and retinoblastoma family pathways in canine osteosarcoma cell lines

Canine osteosarcoma (OS) has been used as a model system for the study of cancer biology and treatment despite the lack of information regarding its pathogenesis. Expression of tumor suppressor genes known to participate in malignant transformation were studied in five different OS cell lines. Each of the cell lines exhibited properties of transformed cells, and those that were tested grew in soft agarose and formed osteoid-containing tumors when injected subcutaneously into nude mice. p53 function was determined to be defective in each cell line as indicated by the lack of induction of p53-responsive genes, p21 and mdm2, following treatment with 5-fluorouracil. p53 mRNA and protein levels were elevated in three cell lines and were extremely low in two cell lines. p53 protein overexpression correlated with the presence of mutations within the DNA binding domain. Four cell lines appeared to contain normal retinoblastoma (Rb) mRNA and Rb protein and no detectable p16 mRNA or protein. In contrast, the remaining cell line contained high levels of p16 mRNA and protein and significantly reduced levels of Rb, p107, and p130 proteins. These results underscore the importance of inactivating p53 and Rb family pathways in canine OS and suggest that unlike human OS, cells derived from canine OS contain mutations that simultaneously inactivate all three Rb family members.

Echocardiographic predictors of left ventricular outflow tract obstruction and systolic anterior motion of the mitral valve after mitral valve reconstruction for myxomatous valve disease

OBJECTIVE

To determine predictors of systolic anterior motion and left ventricular outflow tract obstruction (SAM/LVOTO) after mitral valve repair (MVRep) in patients with myxomatous mitral valve disease.

BACKGROUND

Mechanisms for the development of SAM/LVOTO after MVRep have been described; however, predictors of this complication have not been explored. We hypothesize that pre-MVRep transesophageal echocardiography (TEE) can predict postrepair SAM/ LVOTO.

METHODS

Using TEE, the lengths of the coapted anterior (AL) and posterior (PL) leaflets and the distance from the coaptation point to the septum (C-Sept) were measured before and after MVRep in 33 patients, including 11 who developed SAM/LVOTO (Group 1) and 22 who did not (Group 2).

RESULTS

Group 1 patients had smaller AL/PL ratios (0.99 vs. 1.95, p < 0.0001) and C-Sept distances (2.53 vs. 3.01 cm, p = 0.012) prior to MVRep than those in Group 2. Resolution of SAM/LVOTO was associated with increases in AL/PL ratio and C-Sept distance. This reflects a more anterior position of the coaptation point in those who developed SAM/ LVOTO.

CONCLUSIONS

These data suggest that TEE analysis of the mitral apparatus can identify patients likely to develop SAM/LVOTO after MVRep for myxomatous valve disease. The findings are consistent with the concept that SAM of mitral leaflets is due to anterior malposition of slack mitral leaflet portions into the LVOT. The position of the coaptation point of the mitral leaflets is dynamic and a potential target and end point for surgical designs to prevent SAM/LVOTO post MVRep.

Aortic regurgitant flow by color Doppler measurement of the local velocity 7 mm above the leak orifice--Part 2: Comparison with cardiac catheterization

AIMS

An in vitro study of the flow convergence region in aortic regurgitation has shown that regurgitant flow rate can be derived from the local velocity V(7 mm) at 7 mm distance above the leak orifice. This clinical study was performed to test this method in patients.

METHODS AND RESULTS

In 67 patients with aortic regurgitation, the flow convergence region was imaged by color Doppler. By analogy with the afore mentioned in vitro study, velocity profiles of the acceleration across the flow convergence region were read from the color maps. The profiles were fitted by using a multiplicative regression model. The V(7 mm) was read from the regression curve, and instantaneous regurgitant flow Q was derived from the V(7 mm) with the equation developed in vitro (Q = V(7 mm).cm2/0.28). Q showed a close association with the angiographic grade. Q-derived regurgitant stroke volume correlated significantly with invasive measurements by the angio-Fick method (r = 0.897, SEE = 19.9 ml, y = 0.88x + 5.9 ml).

CONCLUSIONS

Within the color Doppler flow convergence region of aortic regurgitation, the local velocity at 7 mm distance to the leak reflects regurgitant flow rate.