Relation of systemic sympathetic nervous system activation to echocardiographic left ventricular size and performance and its implications in patients with mitral regurgitation

Gene expression and ultra-structural evidence for metabolic derangement in the primary mitral regurgitation heart

Aims

Chronic neurohormonal activation and haemodynamic load cause derangement in the utilization of the myocardial substrate. In this study, we test the hypothesis that the primary mitral regurgitation (PMR) heart shows an altered metabolic gene profile and cardiac ultra-structure consistent with decreased fatty acid and glucose metabolism despite a left ventricular ejection fraction (LVEF) > 60%.

Methods and results

Metabolic gene expression in right atrial (RA), left atrial (LA), and left ventricular (LV) biopsies from donor hearts (n = 10) and from patients with moderate-to-severe PMR (n = 11) at surgery showed decreased mRNA glucose transporter type 4 (GLUT4), GLUT1, and insulin receptor substrate 2 and increased mRNA hexokinase 2, O-linked N-acetylglucosamine transferase, and O-linked N-acetylglucosaminyl transferase, rate-limiting steps in the hexosamine biosynthetic pathway. Pericardial fluid levels of neuropeptide Y were four-fold higher than simultaneous plasma, indicative of increased sympathetic drive. Quantitative transmission electron microscopy showed glycogen accumulation, glycophagy, increased lipid droplets (LDs), and mitochondrial cristae lysis. These findings are associated with increased mRNA for glycogen synthase kinase 3β, decreased carnitine palmitoyl transferase 2, and fatty acid synthase in PMR vs. normals. Cardiac magnetic resonance and positron emission tomography for 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) uptake showed decreased LV [18F]FDG uptake and increased plasma haemoglobin A1C, free fatty acids, and mitochondrial damage-associated molecular patterns in a separate cohort of patients with stable moderate PMR with an LVEF > 60% (n = 8) vs. normal controls (n = 8).

Conclusion

The PMR heart has a global ultra-structural and metabolic gene expression pattern of decreased glucose uptake along with increased glycogen and LDs. Further studies must determine whether this presentation is an adaptation or maladaptation in the PMR heart in the clinical evaluation of PMR.

Differential Expression of the Angiotensin-(1-12)/Chymase Axis in Human Atrial Tissue

BACKGROUND

Heart chymase rather than angiotensin (Ang)-converting enzyme has higher specificity for Ang I conversion into Ang II in humans. A new pathway for direct cardiac Ang II generation has been revealed through the demonstration that Ang-(1-12) is cleaved by chymase to generate Ang II directly. Herein, we address whether Ang-(1-12), chymase messenger RNA (mRNA), and activity levels can be differentiated in human atrial tissue from normal and diseased hearts and if these measures associate with various pathologic heart conditions.

MATERIALS AND METHODS

Atrial appendages were collected from 11 nonfailing donor hearts and 111 patients undergoing heart surgery for the correction of valvular heart disease, resistant atrial fibrillation, or ischemic heart disease. Chymase mRNA was analyzed by real-time polymerase chain reaction and enzymatic activity by high-performance liquid chromatography using Ang-(1-12) as the substrate. Ang-(1-12) levels were determined by immunohistochemical staining.

RESULTS

Chymase gene transcripts, chymase activity, and immunoreactive Ang-(1-12) expression levels were higher in left atrial tissue compared with right atrial tissue, irrespective of cardiac disease. In addition, left atrial chymase mRNA expression was significantly higher in stroke versus nonstroke patients and in cardiac surgery patients who had a history of postoperative atrial fibrillation versus nonatrial fibrillation. Correlation analysis showed that left atrial chymase mRNA was positively related to left atrial enlargement, as determined by echocardiography.

CONCLUSIONS

As Ang-(1-12) expression and chymase gene transcripts and enzymatic activity levels were positively linked to left atrial size in patients with left ventricular heart disease, an important alternate Ang II forming pathway, via Ang-(1-12) and chymase, in maladaptive atrial and ventricular remodeling in humans is uncovered.

Three-dimensional echocardiographic comparison of left ventricular geometry and systolic function between dilated cardiomyopathy and mitral regurgitation with similar left ventricular dilation

PURPOSE

This study aimed to analyze left ventricular (LV) remodeling in patients with LV dilation using three-dimensional (3D) echocardiography, and to compare geometry and systolic function between patients with dilated cardiomyopathy (DCM) and with mitral regurgitation (MR) but similar LV dimension.

METHODS

Cross-sectional study of 60 DCM and 60 MR patients with LV end diastolic diameter (LVEDD) > 35 mm/m² , and of 60 healthy control volunteers.

RESULTS

Despite a similar LVEDD, DCM patients showed a significantly higher 3D sphericity index (3D-SI) than MR patients, whereas 3D ejection fraction (3D-EF) was significantly lower (P < .01). There was a linear relationship between 3D-EF and 3D-SI in both DCM and MR patients (r = -0. 745 and r = -0. 642, respectively; both P < .001). Receiver operating characteristic (ROC) curves showed that 3D-SI had could better discriminate between DCM and MR (sensitivity 90%; specificity 73%; AUC 0.852, P < .01) than other variables. The area under the ROC curve of 3D-SI was significantly larger than that of 3D-EF for detecting heart failure in both patients with DCM and MR.

CONCLUSIONS

LV geometry appears to be more spherical and associated with worse systolic function in DCM than in MR patients, in spite of similar LV dimensions. Systolic function correlated significantly with 3D-SI, which provided a better description of LV remodeling and could be a stronger indicator of heart failure in patients with LV dilation.

Levosimendan in patients with reduced left ventricular function undergoing isolated coronary or valve surgery

OBJECTIVE

In the Levosimendan in Patients with Left Ventricular Systolic Dysfunction Undergoing Cardiac Surgery Requiring Cardiopulmonary Bypass (LEVO-CTS) trial, no differences in clinical outcomes were observed between levosimendan and placebo in a broad population of patients undergoing cardiac surgery. In previous studies, the benefits of levosimendan were most clearly evident in patients undergoing isolated coronary artery bypass grafting (CABG) surgery. In a prespecified analysis of LEVO-CTS, we compared treatment-related outcomes and costs across types of cardiac surgical procedures.

METHODS

Overall, 563 (66.4%) patients underwent isolated CABG, 97 (11.4%) isolated valve, and 188 (22.2%) combined CABG/valve surgery. Outcomes included the co-primary 4-component composite (30-day mortality, 30-day renal replacement, 5-day myocardial infarction, or 5-day mechanical circulatory support), the 2-component composite (30-day mortality or 5-day mechanical circulatory support), 90-day mortality, low cardiac output syndrome (LCOS), and 30-day medical costs.

RESULTS

The 4- and 2-component outcomes were not significantly different with levosimendan and placebo in patients undergoing CABG (15.2% vs 19.3% and 7.8% vs 10.4%), valve (49.0% vs 33.3% and 22.4% vs 2.1%), or combined procedures (39.6% vs 35.9% and 24.0% vs 19.6%). Ninety-day mortality was lower with levosimendan in isolated CABG (2.1% vs 7.9%; hazard ratio [HR], 0.26; 95% confidence interval [CI], 0.11-0.64), but not significantly different in valve (8.3% vs 2.0%; HR, 4.10; 95% CI, 0.46-36.72) or combined procedures (10.4% vs 7.6%; HR, 1.39; 95% CI, 0.53-3.64; interaction P = .011). LCOS (12.0% vs 22.1%; odds ratio, 0.48; 95% CI, 0.30-0.76; interaction P = .118) was significantly lower in levosimendan-treated patients undergoing isolated CABG. Excluding study drug costs, median and mean 30-day costs were $53,707 and $65,852 for levosimendan and $54,636 and $67,122 for placebo, with a 30-day mean difference (levosimendan - placebo) of -$1270 (bootstrap 95% CI, -$8722 to $6165).

CONCLUSIONS

Levosimendan was associated with lower 90-day mortality and LCOS in patients undergoing isolated CABG, but not in those undergoing isolated valve or combined CABG/valve procedures.

Targeting the sympatho-adrenergic link in chronic rheumatic mitral regurgitation: assessing the role of oral beta-blockers

INTRODUCTION

Chronic mitral regurgitation (MR) is characterized by adverse ventricular remodeling and progressive LV dysfunction leading to heart failure (HF). Beta-blockers (BB) improve LV remodeling and prognosis in patients with HF. As chronic severe MR results in neuroendocrine activation similar to HF, it is likely that BB may also exert favorable effects in these patients. No study has assessed the role of oral BB therapy in chronic rheumatic MR.

AIMS

A total of 100 patients of chronic rheumatic MR (mean age 30±13.48 years, NYHA 2.2±0.5) were randomized to BB (Metoprolol, 37±13.5 mg, n=48) vs no BB (n=52) in addition to standard therapy.

RESULTS

Baseline BNP and echocardiographic parameters were comparable in the two groups. At 3 months, BB therapy resulted in significantly lower NYHA class (1.97 vs 2.35), BNP (141 vs 207 pg/mL), LV end-systolic (35.89 vs 51.30) and LV end-diastolic volumes (101 vs 128 mL/m(2) ), LV end-systolic stress (81.1 vs 93.3 dyn/cm(2) ), LV mass (122 vs 154 gm/m(2) ), and LV work (737.02 vs 952.82 mm Hg L/min, all P significant). Therapy with BB resulted in a -15.6%, -10.4%,-12.1%, and -7.3% reduction in LV end-systolic and end-diastolic dimensions and LVESVi and LVEDVi, respectively. Following BB therapy, BNP levels, end-systolic stress, indexed LV mass, and LV work also reduced significantly by 27.3%, 15.6%, 8.7%, and 28%, respectively. The control group had no significant change. The MR grade reduced from severe to moderate in 11% of those on BB (controls: no change). At 6 months, the BB group had further improvement in all echocardiographic parameters ranging from +9.1 to -18.2%.

CONCLUSION

In this first study of BB in rheumatic MR, targeting the sympatho-adrenergic axis exerted favorable effects on NYHA class, LV volumes, LV end-systolic stress, and LV work. Further studies are required to elucidate the role of BB in rheumatic MR.

Differential expression of the angiotensin-(1-12)/chymase axis in human atrial tissue

OBJECTIVE

Heart chymase rather than angiotensin converting enzyme has higher specificity for angiotensin (Ang) I conversion into Ang II in humans. A new pathway for direct cardiac Ang II generation has been revealed through the demonstration that Ang-(1-12) is cleaved by chymase to generate Ang II directly. We address here whether Ang-(1-12) and chymase gene expression and activity are detected in the atrial appendages of 44 patients (10 females) undergoing heart surgery for the correction of valvular heart disease, resistant atrial fibrillation or ischemic heart disease.

METHODS AND RESULTS

Immunoreactive Ang-(1-12) expression was 54% higher in left atrial compared with right atrial appendages. This was associated with higher abundance of left atrial appendage chymase gene transcripts and chymase activity, but no differences in angiotensinogen mRNA. Atrial chymase enzymatic activity was highly correlated with left atrial but not right atrial enlargement as determined by echocardiography, while both tyrosine hydroxylase and neuropeptide Y atrial appendage mRNAs correlated with atrial angiotensinogen mRNAs.

CONCLUSIONS

Higher Ang-(1-12) expression and upregulation of chymase gene transcripts and enzymatic activity from the atrial appendages connected to the enlarged left versus right atrial chambers of subjects with left heart disease defines a role of this alternate Ang II forming pathway in the processes accompanying adverse atrial and ventricular remodeling.

Cardiac mechanics are impaired during fatiguing exercise and cold pressor test in healthy older adults

We sought to determine how the aging left ventricle (LV) responds to sympathetic nervous system (SNS) activation. Three separate echocardiographic experiments were conducted in 11 healthy young (26 ± 1 yr) and 11 healthy older (64 ± 1 yr) adults. Tissue Doppler imaging was used to measure systolic myocardial velocity (S(m)), early diastolic myocardial velocity (E(m)), and late diastolic myocardial velocity (A(m)) during isometric fatiguing handgrip (IFHG), a 2-min cold pressor test (CPT), and 5 min of normobaric hypoxia. Heart rate (HR) and mean arterial pressure (MAP) were also monitored on a beat-by-beat basis; rate pressure product (RPP) was used as an index of myocardial oxygen demand. At peak IFHG, the groups had similar increases in RPP, but the ΔS(m) was significantly greater (i.e., larger impairment) in the older subjects (-0.82 ± 0.13 cm/s) compared with the young subjects (0.37 ± 0.30 cm/s). At peak IFHG, the ΔE(m) was similar between older (-1.59 ± 0.68 cm/s) and young subjects (-1.06 ± 0.76 cm/s). In response to the CPT, both S(m) and E(m) were reduced in the older adults but did not change relative to baseline in the young subjects. Normobaric hypoxia elevated HR and RPP in both groups but did not alter Tissue Doppler parameters. These data indicate that S(m) and E(m) are reduced in healthy older adults during IFHG and CPT. We speculate that suboptimal LV adaptations to SNS stress may partly explain why acute heavy exertion can trigger myocardial ischemia.

Volume overload

Structural cardiac volume overload comprises a group of heterogeneous diseases, each creating a nearly unique set of loading conditions on the left ventricle and/or right ventricle. In turn, the heart responds to each with unique patterns of remodeling, leading to both adaptive and maladaptive consequences. An understanding of these different patterns of hypertrophy and/or remodeling should be useful in developing strategies for the timing and correction of cardiac volume overload.

Left ventricular remodeling early after correction of mitral regurgitation: maintenance of stroke volume with decreased systolic indexes

OBJECTIVE

Mitral valve repair for mitral regurgitation is followed by left ventricle adjustment to new preload and afterload. We evaluated left ventricular geometry and function immediately after mitral valve repair for degenerative prolapse.

METHODS

We prospectively studied 25 patients undergoing mitral valve repair; 15 patients undergoing a coronary artery bypass graft served as controls to determine the impact of cardiopulmonary bypass and cardioplegic arrest on left ventricular function. Intraoperative transesophageal echocardiography was conducted after sternotomy before initiation of cardiopulmonary bypass and after termination of cardiopulmonary bypass and protamine infusion. Simultaneous pulmonary catheter data ensured that the images were obtained under similar hemodynamic conditions.

RESULTS

Immediately after mitral valve repair, left ventricular fractional area change decreased significantly from 65% ± 7% to 52% ± 8% (P < .001). Left ventricular end-diastolic area decreased minimally (21.3 ± 5.3 cm(2) vs 19.4 ± 4.5 cm(2); P = .005), whereas left ventricular end-systolic area increased significantly (7.5 ± 2.3 cm(2) vs 9.3 ± 2.5 cm(2); P < .001). Notably, forward stroke volume (thermodilution) remained similar (63 ± 24 mL vs 66 ± 19 mL; P = .5). No significant difference was found in controls between pre- cardiopulmonary bypass and post-cardiopulmonary bypass fractional area change (54% ± 12% vs 57% ± 10%; P = .19), left ventricular end-diastolic area (16.6 ± 6.2 cm(2) vs 15.7 ± 5.0 cm(2); P = .32), and stroke volume (72 ± 29 mL vs 65 ± 19 mL; P = .15); they had a slight decrease in left ventricular end-systolic area (7.9 ± 4.4 cm(2) vs 6.9 ± 3.2 cm(2); P = .03).

CONCLUSIONS

Early after correction of mitral regurgitation, left ventricular fractional area change decreases significantly, primarily as the result of a larger end-systolic dimension. This may be a compensatory mechanism to prevent augmentation of forward stroke volume after mitral valve repair.

Mitral regurgitation

Mitral regurgitation affects more than 2 million people in the USA. The main causes are classified as degenerative (with valve prolapse) and ischaemic (ie, due to consequences of coronary disease) in developed countries, or rheumatic (in developing countries). This disorder generally progresses insidiously, because the heart compensates for increasing regurgitant volume by left-atrial enlargement, causes left-ventricular overload and dysfunction, and yields poor outcome when it becomes severe. Doppler-echocardiographic methods can be used to quantify the severity of mitral regurgitation. Yearly mortality rates with medical treatment in patients aged 50 years or older are about 3% for moderate organic regurgitation and about 6% for severe organic regurgitation. Surgery is the only treatment proven to improve symptoms and prevent heart failure. Valve repair improves outcome compared with valve replacement and reduces mortality of patient with severe organic mitral regurgitation by about 70%. The best short-term and long-term results are obtained in asymptomatic patients operated on in advanced repair centres with low operative mortality (<1%) and high repair rates (>/=80-90%). These results emphasise the importance of early detection and assessment of mitral regurgitation.

Beta1-adrenoceptor blockade mitigates excessive norepinephrine release into cardiac interstitium in mitral regurgitation in dog

Mitral regurgitation (MR) is associated with increased neuronal release of norepinephrine (NE) and epinephrine (EP) into myocardial interstitial fluid (ISF) that may be necessary in sustaining left ventricular (LV) function via activation of cardiomyocyte beta-adrenergic receptors (ARs). However, activation of neuronal beta-ARs on cardiac neurons may lead to further catecholamine release, with an attendant risk of functional deterioration. We hypothesize that a beneficial effect of beta-AR blockade may therefore mitigate excessive catecholamine release from cardiac adrenergic neurons in dogs with MR. We measured the effects of chronic beta-receptor blockade (beta-RB) on ISF NE and EP release using in vivo microdialysis in open-chest anesthetized dogs after 4 wk of MR with or without extended release of metoprolol succinate (100 mg/day) as well as in control dogs. Fractional shortening increased by 30% in both MR and MR + beta-RB dogs after 4 wk of MR. In MR + beta-RB dogs, stellate-stimulated heart rate change was attenuated compared with control and MR dogs, whereas peak change of LV pressure over time (+dP/dt) increased equally in all groups. Stellate-stimulated ISF NE increased fivefold over baseline in MR versus twofold in control dogs (< 0.05), but the NE release was significantly attenuated in MR + beta-RB dogs. In contrast, stellate-stimulated increases in ISF EP did not differ in control, MR, and MR + beta-RB dogs. This study demonstrates that beta-RB attenuates ISF NE release from cardiac neurons and that the LV functional response to MR is not dependent on an excess increase in ISF NE. Thus beta1-RB may exert a beneficial effect by attenuating untoward effects of excessive sympathetic efferent neural NE release while sustaining early LV functional adaptation to MR.

Controversies in ventricular remodelling

Ventricular remodelling describes structural changes in the left ventricle in response to chronic alterations in loading conditions, with three major patterns: concentric remodelling, when a pressure load leads to growth in cardiomyocyte thickness; eccentric hypertrophy, when a volume load produces myocyte lengthening; and myocardial infarction, an amalgam of patterns in which stretched and dilated infarcted tissue increases left-ventricular volume with a combined volume and pressure load on non-infarcted areas. Whether left-ventricular hypertrophy is adaptive or maladaptive is controversial, as suggested by patterns of signalling pathways, transgenic models, and clinical findings in aortic stenosis. The transition from apparently compensated hypertrophy to the failing heart indicates a changing balance between metalloproteinases and their inhibitors, effects of reactive oxygen species, and death-promoting and profibrotic neurohumoral responses. These processes are evasive therapeutic targets. Here, we discuss potential novel therapies for these disorders, including: sildenafil, an unexpected option for anti-transition therapy; surgery for increased sphericity caused by chronic volume overload of mitral regurgitation; an antifibrotic peptide to inhibit the fibrogenic effects of transforming growth factor beta; mechanical intervention in advanced heart failure; and stem-cell therapy.

Percutaneous mitral annular reduction provides continued benefit in an ovine model of dilated cardiomyopathy

BACKGROUND

Functional mitral valve regurgitation plays a key role in the symptomatic severity and progression of heart failure. In an ovine model of dilated cardiomyopathy, we examined the chronic functional consequences of mitral regurgitation reduction using a recently developed novel percutaneous mitral annular reduction (PMAR) device.

METHODS AND RESULTS

Fourteen adult sheep were paced right ventricularly at 180 to 190 bpm for 5 weeks, leading to the development of moderate mitral valve regurgitation. After echocardiographic, hemodynamic, and neurohormonal analysis, 9 animals underwent PMAR. All animals were subsequently paced for another 28 days, and a final echocardiographic and hemodynamic study was conducted. Animals that had undergone PMAR showed significantly increased negative and positive dP/dt, whereas pulmonary capillary wedge pressure and mitral valve regurgitation were significantly reduced compared with those at device implant despite continued pacing. In conjunction, significant improvements in plasma norepinephrine and brain natriuretic peptide were apparent.

CONCLUSIONS

The application of PMAR in animals with pacing-induced dilated cardiomyopathy and functional mitral valve regurgitation resulted in continued improvements in hemodynamic and neurohormonal parameters.

PPAR-gamma agonist rosiglitazone ameliorates ventricular dysfunction in experimental chronic mitral regurgitation

Previously we reported that the beneficial effects of beta-adrenergic blockade in chronic mitral regurgitation (MR) were in part due to induction of bradycardia, which obviously affects myocardial energy requirements. From this observation we hypothesized that part of the pathophysiology of MR may involve faulty energy substrate utilization, which in turn might lead to potentially harmful lipid accumulation as observed in other models of heart failure. To explore this hypothesis, we measured triglyceride accumulation in the myocardia of dogs with chronic MR and then attempted to enhance myocardial metabolism by chronic administration of the peroxisome proliferator-activated receptor (PPAR)-gamma agonist rosiglitazone. Cardiac tissues were obtained from three groups of dogs that included control animals, dogs with MR for 3 mo without treatment, and dogs with MR for 6 mo that were treated with rosiglitazone (8 mg/day) for the last 3 mo of observation. Hemodynamics and contractile function (end-systolic stress-strain relationship, as measured by K index) were assessed at baseline, 3 mo of MR, and 6 mo of MR (3 mo of the treatment). Lipid accumulation in MR (as indicated by oil red O staining score and TLC analysis) was marked and showed an inverse correlation with the left ventricular (LV) contractility. LV contractility was significantly restored after PPAR therapy (K index: therapy, 3.01 +/- 0.11*; 3 mo MR, 2.12 +/- 0.34; baseline, 4.01 +/- 0.29; ANOVA, P = 0.038; *P < 0.05 vs. 3 mo of MR). At the same time, therapy resulted in a marked reduction of intramyocyte lipid. We conclude that 1) chronic MR leads to intramyocyte myocardial lipid accumulation and contractile dysfunction, and 2) administration of the PPAR-gamma agonist rosiglitazone ameliorates MR-induced LV dysfunction accompanied by a decline in lipid content.

Cardiac-specific norepinephrine mass transport and its relationship to left ventricular size and systolic performance

Objectives of this study were to develop a technique for quantifying cardiac-specific norepinephrine (NE) mass transport and determine whether cardiac NE kinetic modeling parameters were related to physiological variables of left ventricular (LV) size and systolic performance in nine patients with chronic mitral regurgitation. Biplane contrast cineventriculograms were used to determine LV size and ejection fraction (EF), micromanometer LV pressures and radionuclide LV volumes from a range of loading conditions to calculate LV end-systolic elastance, and [(3)H]NE infusions with LV and coronary sinus sampling for [(3)H]NE and endogenous NE during and after termination of infusions to model NE mass transport. Total NE release rate into cardiac interstitial fluid (M(IF)(R)) averaged 859 +/- 214 and NE released de novo into cardiac interstitial fluid (M(IF)(u,r,en)) averaged 546 +/- 174 pmol/min. Both M(IF)(R) and M(IF)(u,r,en)correlated directly with LV end-systolic volume (r = 0.84, P = 0.005; r = 0.86, P = 0.003); inversely with LV EFs (r = -0.75, P = 0.02; r = -0.81, P = 0.008); and inversely with LV end-systolic elastance values, optimally fit by a nonlinear function (r = 0.89, P = 0.04; r = 0.96, P = 0.01). We conclude that total and newly released NE into interstitial fluid of the heart, determined by regional mass transport kinetic model, are specific measures of regional cardiac-specific sympathetic nervous system activity and are strongly related to measures of LV size and systolic performance. These data support the concept that this new model of organ-specific NE kinetics has physiological relevance.

Is it ever too late to operate on the patient with valvular heart disease?

All valvular heart disease imparts a hemodynamic burden on the left and/or right ventricle. This burden can only be removed effectively by correcting the responsible valvular lesion. Although a percutaneous approach is usually used to correct mitral stenosis, other valve lesions require surgical intervention. Over the past 40 years there has been a persistent improvement in our understanding of the pathophysiology of valvular heart disease and in the surgical techniques for correcting it. These factors have acted in concert to alter our view of the proper timing and applicability of surgery. On one hand it is no longer necessary or even advisable to delay surgery until advanced symptoms are present, and thus surgery is timed earlier today than it was even a decade ago. On the other hand, many but not all patients with far advanced disease, once considered inoperable, are now often helped substantially by valve surgery. However, selection of which of these very ill patients will or will not benefit from valve surgery remains a challenge for all of us. It is this group of patients that is addressed in the review.

Changes in systemic sympathetic nervous system activity after mitral valve surgery and their relationship to changes in left ventricular size and systolic performance in patients with mitral regurgitation

BACKGROUND

We have shown that the systemic sympathetic nervous system (SNS) is activated in patients with chronic mitral regurgitation (MR). However, the fate of systemic SNS activity after surgical correction of MR is currently unknown.

METHODS

We examined 14 patients with MR who had normal sinus rhythm with an investigational, preoperative cardiac catheterization, including arterial norepinephrine (NE) sampling and [(3)H]-NE infusions and arterial blood sampling to determine NE kinetic parameters using a 2-compartment modeling analysis. The arterial NE and NE kinetic parameters were determined in all patients after mitral valve surgery (MVS) at a mean of 12 months. A 2-dimensional echocardiographic examination was also performed before and after MVS.

RESULTS

The average extravascular NE release rates (NE(2)) before and after MVS were 1.89 +/- 0.66 and 2.26 +/- 0.82 microg/min/m(2) (P =.24), respectively. The average left ventricular (LV) end-diastolic dimension, fractional shortening, and ejection fraction decreased, whereas the mean LV end-systolic dimension did not change between the pre- and post-MVS echocardiographic studies. However, these group averages were comprised of patients with MR in whom the NE(2) and echocardiographic values both increased and decreased. This lack of homogeneity was a reflection of our new observation that the pre- to post-MVS changes in NE(2) were directly proportional to the changes in LV end-systolic dimension (r = 0.91, P <.001) and inversely related to the changes in LV fractional shortening (r = -0.82, P <.001) and ejection fraction (r = -0.78, P <.001).

CONCLUSIONS

The response in systemic SNS activity in patients with MR after MVS is not homogeneous, and these changes are concordant with the post-MVS changes in LV size and systolic performance. These data further support our earlier observations and extend them to suggest that systemic SNS activation in patients with chronic MR is related to LV remodeling and impaired systolic performance.

Feasibility and Short-Term Efficacy of Percutaneous Mitral Annular Reduction for the Therapy of Heart Failure-Induced Mitral Regurgitation

Background— Mitral regurgitation (MR) frequently accompanies congestive heart failure (CHF) and is associated with poorer prognosis and more significantly impaired symptomatic status. Although surgical mitral valve annuloplasty has the potential to offer benefit, concerns about the combined surgical risk and possible effects on ventricular performance have limited progress. We evaluated the feasibility and short-term efficacy of a novel device placed in the coronary sinus to reduce MR in the setting of CHF.

Methods and Results— CHF and MR were induced in 9 adult sheep by rapid ventricular pacing for 5 to 8 weeks. A mitral annular constraint device was implanted percutaneously through the right internal jugular vein in the coronary sinus and great cardiac vein to create a short-term stable reduction (24.9±2.5%) in the mitral annular septal-lateral dimension as assessed echocardiographically. Right and left heart pressures and cardiac output were determined before and 15 minutes after device implantation. MR extent was examined echocardiographically and expressed as a ratio of left atrial area (MR/LAA). After device placement, MR was substantially reduced from an MR/LAA of 42+6% to 4±3% ( P <0.01). In association, mean pulmonary wedge pressure was significantly reduced (26±3 to 18±3 mm Hg; P <0.01) and mean cardiac output significantly increased (3.4±0.3 to 4.3±0.4 L/min; P =0.01).

Conclusions— In this model of CHF, percutaneous placement of a mitral annular constraint device in the coronary sinus resulted in the short-term elimination or minimization of MR and was accompanied in the short term by favorable hemodynamic effects.

The renin-angiotensin system in mitral regurgitation: a typical example of tissue activation

Mitral regurgitation (MR) creates a unique hemodynamic stress by inducing a low pressure form of volume overload due to ejection into the left atrium, without the pressure component that accompanies aortic regurgitation. Chronic therapy with vasodilators has been shown to reduce left ventricular wall stress, and thereby delay or obviate the need for valve replacement in aortic regurgitation; however, no data are currently available in patients with chronic MR using standard vasodilators or agents that block renin-angiotensin system (RAS) components. Studies in a clinically relevant dog model of experimentally induced MR demonstrate upregulation of the cardiac RAS. However, RAS blockade fails to improve left ventricular remodeling and function, whereas beta-adrenergic blockade results in restoration of left ventricular chamber and myocyte function.