Proteomic investigations into hypertension: what's new and how might it affect clinical practice?

Introduction: Hypertension is a multifactorial disease that has, thus far, proven to be a difficult target for pharmacological intervention. The application of proteomic strategies may help to identify new biomarkers for the early diagnosis and prompt treatment of hypertension, in order to control blood pressure and prevent organ damage. Areas covered: Advances in proteomics have led to the discovery of new biomarkers to help track the pathophysiological processes implicated in hypertension. These findings not only help to better understand the nature of the disease, but will also contribute to the clinical needs for a timely diagnosis and more precise treatment. In this review, we provide an overview of new biomarkers identified in hypertension through the application of proteomic techniques, and we also discuss the difficulties and challenges in identifying biomarkers in this clinical setting. We performed a literature search in PubMed with the key words 'hypertension' and 'proteomics', and focused specifically on the most recent literature on the utility of proteomics in hypertension research. Expert opinion: There have been several promising biomarkers of hypertension identified by proteomics, but too few have been introduced to the clinic. Thus, further investigations in larger cohorts are necessary to test the feasibility of this strategy for patients. Also, this emerging field would profit from more collaboration between clinicians and researchers.

Echocardiography can predict the development of severe mitral regurgitation after percutaneous mitral valvuloplasty by the Inoue technique

Severe mitral regurgitation (MR) following mitral balloon valvuloplasty is a major complication of this procedure. We recently described a new echocardiographic score that can predict the development of severe MR following mitral valvuloplasty with the double balloon technique. The present study was designed to test the usefulness of this score for predicting severe MR in patients undergoing the procedure using the Inoue balloon technique. From 117 consecutive patients who underwent mitral valvuloplasty using the Inoue technique, 14 (11.9%) developed severe MR after the procedure. A good quality echocardiogram before mitral valvuloplasty was available in 11 patients. These 11 patients were matched by age, sex, mitral valve area, and degree of MR before valvuloplasty with 69 randomly selected patients who did not develop severe MR after Inoue valvuloplasty. The total MR-echocardiographic (MR-echo) score was significantly greater in the severe MR group (10.5 +/- 1.4 vs 8.2 +/- 1.1; p <0.001). In addition, the component grades for the anterior leaflet (2.9 +/- 0.5 vs 2.2 +/- 0.4; p <0.001), posterior leaflet (2.6 +/- 0.7 vs 1.9 +/- 0.8), commissures (2.4 +/- 0.8 vs 2.0 +/- 0.5; p <0.05) and subvalvular apparatus (2.6 +/- 0.5 vs 1.9 +/- 0.4; p <0.001) were also higher in the MR group. Using a total score of > or = 10 as a cut-off point for predicting severe MR with the Inoue technique, a sensitivity of 82%, specificity of 91%, accuracy of 90%, and negative predictive value of 97% were obtained. Stepwise logistic regression analysis identified the MR-echo score as the only independent predictor for developing severe MR with the Inoue technique (p <0.0001). Thus, the MR-echo score can also predict the development of severe MR following mitral balloon valvuloplasty using the Inoue technique.

Two-dimensional echocardiographic assessment of the progression of aortic root size in 127 patients with chronic aortic regurgitation: role of the supraaortic ridge and relation to the progression of the lesion

Although aortic root dilation has etiologic and prognostic significance in patients with chronic aortic regurgitation (AR), no information is available regarding changes over time in aortic root size in patients with the entire spectrum of AR severity or how such changes relate to progression of the AR or to left ventricular (LV) overload. To analyze this, a total of 127 patients with chronic AR who had more than 6 months of follow-up by two-dimensional and Doppler echocardiography were included in the study (69 men and 58 women; mean age 59.3 +/- 21.2 years [range 14 to 94 years]; 67 cases of mild, 45 moderate, 15 severe, and 21 bicuspid aortic valve disease). The aortic anulus, sinuses of Valsalva, supraaortic ridge, and ascending aorta were measured in the parasternal long-axis view, LV volumes were calculated (biplane Simpson's approach), and the severity of AR was quantified based on proximal jet size and graded according to an algorithm that takes into account major color Doppler criteria. At entry to the study, significant differences between patients with mild, moderate, and severe AR were noted only in supraaortic ridge size (1.46 +/- 0.29 cm/m2 vs 1.63 +/- 0.33 cm/m2 [p < 0.006]; vs 1.67 +/- 0.43 cm/m2 [p < 0.03]). A significant increase in aortic root size at all levels was observed during the follow-up period in all three groups of severity of AR. The rate of change of the supraaortic ridge, the upper support structure of the anulus and cusps, was faster in patients with more severe degrees of AR (p = 0.013); this was not the case at the other aortic levels. No differences were observed in aortic root size or rate of progression between patients with bicuspid or tricuspid aortic valves. Patients were considered "progressive" if they lay on the steepest positive segment of the curve representing the rank order in the rate of aortic root progression. Compared with "nonprogressive" patients, patients who were progressive in supraaortic ridge size (rate >0.12 cm/yr; n = 23) had a faster rate of progression in the degree of regurgitation as assessed by the regurgitant jet area/LV outflow tract area ratio measured in the parasternal short-axis view (0.48 +/- 0.45 vs 0.24 +/- 0.5/yr; p < 0.03) and a foster rate of progression of LV end-diastolic volume (30 +/- 22.8 vs 14.4 +/- 15.6 ml/yr; p < 0.0002) and LV mass (70.8 +/- 74.4 vs 16.8 +/- 19.2 gm/yr; p < 0.0004). In conclusion, there is progressive dilation of the aortic root at all levels, even in patients with mild AR. More rapid progression in aortic root size is associated with more rapid progression of the underlying aortic insufficiency, as well as more rapid increases in LV volume and mass.

Doppler echocardiographic assessment of progression of aortic regurgitation

The rate of progression of the degree of chronic aortic regurgitation (AR) is unknown. Furthermore, although left ventricular (LV) dilation has been studied in patients with severe AR, its rate and determining factors, and specifically, its relation to the degree of regurgitation remain to be established and have not previously been studied for mild and moderate AR. The purpose of this study was to explore the progression of chronic AR by 2-dimensional and Doppler echocardiography, and the relation of LV dilation to the fundamental regurgitant lesion and its progression in patients with a full spectrum of initial AR severity. We studied 127 patients with AR by 2-dimensional and Doppler echocardiography (69 men; 59 +/- 21 years; 67 with mild, 45 with moderate, 15 with severe AR). AR increased in 38 patients (30%) (25% of mild, 44% of moderate, and 50% of moderate to severe lesions; p <0.006). The ratio of proximal AR jet height to LV outflow tract height also increased (30.3 +/- 17.5% vs 35.2 +/- 19.7%; p <0.0001). Initial LV volumes and mass were larger in patients with more severe AR and increased significantly during follow-up (138 +/- 53 to 164 +/- 70 ml; 59 +/- 32 to 71.7 +/- 42 ml; 203 +/- 89 to 241 +/- 114 g; p <0.0001). LV volumes and mass increased faster in patients with more severe AR, and in those in whom the degree of AR progressed more rapidly. Finally, patients with bicuspid aortic valve (n = 21) had a higher prevalence of severe AR than patients with tricuspid aortic valves (52% vs 4%; p <0.001). In conclusion, AR is a progressive disease not only in patients with severe AR but also in those with mild and moderate regurgitation. Patients with more severe AR have larger left ventricles that also dilate more rapidly.

Doppler echocardiographic assessment of long-term progression of mitral stenosis in 103 patients: valve area and right heart disease

OBJECTIVES

The purpose of this study was to determine, in a large referral population, the rate of echocardiographic change in mitral valve area (MVA) without interim intervention, to determine which factors influence progression of narrowing and to examine associated changes in the right side of the heart.

BACKGROUND

Little information is currently available on the echocardiographic progression of mitral stenosis, particularly on progressive changes in the right side of the heart and the ability of a previously proposed algorithm to predict progression.

METHODS

We studied 103 patients (mean age 61 years; 74% female) with serial two-dimensional and Doppler echocardiography. The average interval between entry and most recent follow-up study was 3.3 +/- 2 years (range 1 to 11).

RESULTS

During the follow-up period, MVA decreased at a mean rate of 0.09 cm2/year. In 28 patients there was no decrease, in 40 there was only relatively little change (< 0.1 cm2/year) and in 35 the rate of progression of mitral valve narrowing was more rapid (> or = 0.1 cm2/year). The rate of progression was significantly greater among patients with a larger initial MVA and milder mitral stenosis (0.12 vs. 0.06 vs. 0.03 cm2/year for mild, moderate and severe stenosis, p < 0.01). Although the rate of mitral valve narrowing was a weak function of initial MVA and echocardiographic score by multivariate analysis, no set of individual values or cutoff points of these variables or pressure gradients could predict this rate in individual patients. There was a significant increase in right ventricular diastolic area (17 to 18.7 cm2) and tricuspid regurgitation grade (2 + to 3 +; p < 0.0001 between entry and follow-up studies). Progression in right heart disease occurred even in patients with minimal or no change in MVA. Patients with associated aortic regurgitation had a higher rate of decrease in MVA than did those with trace or no aortic regurgitation (0.19 vs. 0.086 cm2/year, p < 0.05).

CONCLUSIONS

The rate of mitral valve narrowing in individual patients is variable and cannot be predicted by initial MVA, mitral valve score or transmitral gradient, alone or in combination. Right heart disease can progress independent of mitral valve narrowing.

Quantitative assessment of stenotic aortic valve area by using intracardiac echocardiography: in vitro validation and initial in vivo illustration

Quantitative assessment of aortic stenosis (AS) is subject to the limitations of all current noninvasive and invasive methods. The ability to obtain a direct measure of aortic valve area with high resolution by intracardiac echocardiography (ICE) could be of great benefit to catheterized patients. To provide a fixed AS area as an ideal standard for comparison, we performed ICE in 12 sheep hearts with experimentally created AS and five human AS hearts from autopsies. ICE catheters were passed retrograde across the aortic valve, and the minimal orifice area on pullback was planimetered and compared with calibrated video imaging. The entire orifice circumference could be successfully recorded in 16 (94%) hearts. Orifice area from ICE correlated well with actual values (r=0.98; standard error of the estimate [SEE] = 0.06 cm2). To illustrate the applicability in vivo, two canine models and 10 patients with AS were studied. The limiting orifice could be imaged in both animals and in 8 of 10 patients, in whom values agreed well with invasive data (r= 0.95; SEE = 0.04 cm2). ICE can therefore accurately measure AS orifice area in vitro; it can be applied in vivo as well. These validation studies laid the foundation for subsequent clinical studies and applications.

Echocardiography can predict which patients will develop severe mitral regurgitation after percutaneous mitral valvulotomy

OBJECTIVES

Using two-dimensional echocardiography, we sought to identify features that are associated with severe mitral regurgitation after percutaneous mitral valvulotomy and combine them into a predictive score.

BACKGROUND

Severe mitral regurgitation after percutaneous mitral valvulotomy is a major complication carrying an adverse prognosis that, to date, has not been predictable in advance.

METHODS

In a consecutive series of 566 patients who underwent percutaneous mitral valvulotomy, 37 (6.5%) developed severe mitral regurgitation (assessed by angiography) after the procedure, 31 of whom had an echocardiogram available before percutaneous mitral valvulotomy. These 31 patients were matched by age, gender, mitral valve area and degree of mitral regurgitation before valvulotomy with 31 randomly selected patients who did not develop severe mitral regurgitation after percutaneous mitral valvulotomy. An echocardiographic score was developed on the basis of the pathologic studies of valves of patients who developed severe regurgitation after percutaneous mitral valvulotomy (leaflet rupture of relatively thin portions of nonhomogeneously thickened leaflets in the presence of commissural and subvalvular calcification) and evaluated uneven distribution of thickness in the anterior and posterior mitral leaflets, degree of commissural disease and subvalvular disease involvement, with each component graded from 0 to 4 (total, 0 to 16). Intraobserver and interobserver variability for score assessment were 6% and 7%, respectively.

RESULTS

The total mitral regurgitation echocardiographic score was significantly greater in the severe mitral regurgitation group (11.7 +/- 1.9 [mean +/- SD] vs. 8.0 +/- 1.2, p < 0.001). In addition, the component grades for the anterior leaflet (3.2 +/- 0.7 vs. 2.3 +/- 0.6, p < 0.001), commissures (2.6 +/- 0.7 vs. 1.6 +/- 0.6, p < 0.001) and subvalvular apparatus (3.2 +/- 0.6 vs. 2.3 +/- 0.7, p < 0.001) were also higher in the mitral regurgitation group. With a total score > or = 10 as a cutoff point for predicting severe mitral regurgitation after percutaneous mitral valvulotomy, a sensitivity of 90 +/- 5% and a specificity of 97 +/- 3% were obtained. Stepwise logistic regression analysis identified the mitral regurgitation echocardiographic score as the only independent predictor for developing severe mitral regurgitation after percutaneous mitral valvulotomy (p < 0.0001).

CONCLUSIONS

This new mitral regurgitation echocardiographic score can predict the development of severe mitral regurgitation after percutaneous mitral valvulotomy and can be useful in the selection of patients for this technique.

Intracardiac echocardiography: in vitro and in vivo validation for right ventricular volume and function

To determine the feasibility and accuracy of intracardiac ultrasonography (ICUS) for the measurement of right ventricular (RV) volumes and function, a 10 MHz ICUS catheter was used in an in vitro and in vivo model. In the in vitro study, 16 sheep hearts were imaged. Sequential cross-sectional images from RV apex to base were recorded during a calibrated pullback. Volumes were calculated by applying Simpson's algorithm. ICUS-obtained volumes correlated well with actual volumes (standard error of estimate [SEE] = 2.3 ml, r = 0.98). For the in vivo study, a beating-heart canine model was used (31 hemodynamic stages in six dogs). Actual volumes were measured by an intracavitary balloon connected to an external column. Sequential cross-sectional images were recorded during the ICUS catheter pullback from apex to base of the RV, and volumes calculated by Simpson's algorithm. Good correlations were observed between ICUS and actual values for diastolic (SEE = 4.1 ml, r = 0.97), systolic (SEE = 3.4 ml, r = 0.96), and ejection fraction (SEE = 3.1%, r = 0.87) values. This new technique can accurately quantitate RV volumes, can function both in vitro and in vivo, and has the potential for increasing applications to questions of clinical and research interest.

Intracardiac ultrasonographic assessment of atrial septal defect area: in vitro validation and technical considerations

Assessment of atrial septal defect (ASD) size and shape is important for planning and guiding its transcatheter occlusion and can potentially be achieved by intracardiac ultrasonography (ICUS). ICUS accuracy, however, must first be established against stable standards and technical imaging requirements defined. We therefore used 10, 20, and 30 MHz ICUS catheters to examine 17 ASDs that were 0.16 to 6.7 cm2 in area and were surgically created in excised ovine hearts with 10, 20, and 30 MHz ICUS catheters. ASD shape and area by ICUS were compared with direct video images of the actual ASD. In all instances minimal area by ICUS pullback agreed well with actual values (y = 1.04x + 0.2, SEE = 0.23 cm2, r = 0.99) and corresponded well with defect shapes. The maximum angle between ultrasonography beam and septal plane allowing for complete ASD visualization was 20 degrees. The angle depended on transducer frequency and septal thickness. This new technique has potential value for the accurate assessment of ASD shape and size and may be especially useful in the setting of transcatheter occlusion.

Pulsatile pressure affects the disappearance of echocardiographic contrast agents

The purpose of this study was to determine in an in vitro model the effect of pulsatile pressure on the decay of echocardiographic contrast agents. Use of contrast agents for quantitative assessment of perfusion requires understanding of the factors controlling their rates of disappearance. Prior studies have shown that constant pressure affects the rate of disappearance of these agents. It is not known whether pulsatile pressure influences the rate of decay of contrast agents. In an in vitro chamber, three contrast agents (Albunex, hand-agitated saline solution, and hand-agitated Angiovist) were exposed to pulses of pressure at three rates (30, 60, and 120 pulsations/min), keeping pressure characteristics (peak, nadir, and mean) within a narrow range. Five injections were performed for each agent at each rate. Two-dimensional echocardiographic images of the effects of contrast material were recorded from injection until total disappearance. Videointensity was measured and time-intensity curves were generated. These curves of intensity decay were fitted to an exponential decay function (I = Ae-lambda t) and the velocity of decay (lambda) was used for comparisons. For all agents, intensity of contrast decreased over time. Saline solution and Angiovist, but not Albunex, showed pulsatile decreases in intensity of contrast with each peak pressure and partial recovery of contrast intensity with each nadir pressure. (ABSTRACT TRUNCATED AT 250 WORDS)

Intracardiac ultrasound measurement of volumes and ejection fraction in normal, infarcted, and aneurysmal left ventricles using a 10-MHz ultrasound catheter

BACKGROUND

Our objective was to examine the accuracy of intracardiac ultrasound (ICUS) measurement of left ventricular (LV) volumes and ejection fraction (EF) using a 10-MHz ultrasound catheter. ICUS can image the LV in cross sections at all levels along the long axis with a transducer mounted on the tip of a catheter. Sequential serial LV cross-sectional images can be obtained during cardiac catheterization and used to calculate LV volumes by Simpson's rule. This technique may be an alternative to contrast LV angiography.

METHODS AND RESULTS

A beating-heart in vivo model was created to measure LV volume directly and continuously with an intracavity high-compliance latex balloon connected to a calibrated extracardiac reservoir in eight dogs in 35 experimental stages. A 10F ICUS catheter with a 10-MHz single-element transducer was introduced retrogradely via the aortic valve to the apex. Series of sequential LV cross-sectional images were recorded from the apex to the base during a calibrated pullback of the catheter. At each 5-mm interval, the LV cross section was traced at end diastole and end systole. LV volume was calculated by Simpson's rule by integrating all segmental areas multiplied by segmental height. The effect on accuracy of selecting 5-, 10-, or 15-mm heights or a single section at the midventricular level for measurement was assessed. The influence of distorted ventricular shape on the accuracy of ICUS measurements of LV volume was evaluated. This method was applied in 19 experimental stages in 10 intact dogs and pigs catheterized via the femoral artery. In the in vivo canine model, LV end-diastolic volume, end-systolic volume, and EF determined by ICUS using 5-, 10-, or 15-mm segments were not different from the actual measurements. But correlation and agreement between ICUS end-diastolic volume and direct measurements for 5- and 10-mm segments were significantly better than for 15-mm segments or a single section. Similar excellent correlations and agreement were observed for actual and ICUS-derived end-systolic volumes using 5-, 10-, or 15-mm segments. The ICUS-derived EF correlated very well with actual EF with a small measurement error of 3.91 +/- 2.59% for 5-mm or 4.13 +/- 2.79% for 10-mm segments but a significantly greater measurement error for 15-mm segments (5.35 +/- 3.76%) or single sections (14.8 +/- 12.2%). The presence of LV infarction or aneurysm did not significantly influence the accuracy of ICUS calculations for segmental heights < or = 10 mm. Application in intact animals demonstrated a good correlation between stroke volume measured by ICUS and by thermodilution or flowmeter. ICUS-derived LV volumes correlated well with biplane angiographic volumes, with a tendency toward underestimation. There was no significant difference between ICUS-determined LV EF and EF determined by angiography.

CONCLUSIONS

Intracardiac echocardiography accurately measures LV volumes and global systolic function in both regularly shaped and distorted left ventricles. This technique directly and continuously visualizes circumferential LV endocardium and wall thickness without contrast agents or geometric assumptions for calculation of LV volume. Thus, it should be particularly useful in patients at high risk for contrast-related complications or distorted LV shapes in which geometric assumptions may not be valid.

Determinants of functional tricuspid regurgitation in incomplete tricuspid valve closure: Doppler color flow study of 109 patients

OBJECTIVES

The aim of this study was to investigate the association between the pattern of incomplete tricuspid valve closure and the presence of tricuspid regurgitation and to identify factors that determine the severity of regurgitation associated with this pattern.

BACKGROUND

The incomplete tricuspid valve closure pattern (defined as apical displacement of the leaflets) has been described by two-dimensional echocardiography. However, whether this pattern is universally associated with tricuspid regurgitation and the determinants of severity of regurgitation in its presence have not been studied by Doppler color flow mapping.

METHODS

We identified 109 consecutive patients (mean age 62 +/- 17 years) with incomplete tricuspid valve closure who were studied by Doppler color flow mapping. We measured the linear apical displacement of the coaptation point from the tricuspid annulus and the area of displacement between the leaflets and annulus. Right atrial, ventricular and annular dimensions were measured and compared with those in a group of normal subjects.

RESULTS

Tricuspid regurgitation was present in all patients with the incomplete closure pattern; it was mild in 14%, moderate in 19% and severe in 67%. Apical displacement was significantly greater (p < 0.02) in those with severe regurgitation than in those with mild regurgitation or in normal subjects. Tricuspid annulus dilation was the only independent predictor of severity of regurgitation. The right ventricle was not significantly dilated in 32% of patients, and right ventricular systolic pressure was not correlated with the severity of regurgitation and was < 30 mm Hg in 11% of patients.

CONCLUSIONS

Tricuspid regurgitation was associated with incomplete tricuspid valve closure in all patients studied and was moderate to severe in 86%. Impaired coaptation is best reflected by the displacement area between the leaflets and the annulus. High pulmonary pressure and significant right ventricular dilation are not prerequisites for functional tricuspid regurgitation. Annular dilation is the most consistent and important determinant of this lesion.