Regression of left ventricular dilatation and hypertrophy after aortic valve replacement

Myocardial reverse remodeling after pressure unloading is associated with maintained cardiac mechanoenergetics in a rat model of left ventricular hypertrophy

Pressure unloading represents the only effective therapy in increased afterload-induced left ventricular hypertrophy (LVH) as it leads to myocardial reverse remodeling (reduction of increased left ventricular mass, attenuated myocardial fibrosis) and preserved cardiac function. However, the effect of myocardial reverse remodeling on cardiac mechanoenergetics has not been elucidated. Therefore, we aimed to provide a detailed hemodynamic characterization in a rat model of LVH undergoing pressure unloading. Pressure overload was induced in Sprague-Dawley rats by abdominal aortic banding for 6 (AB 6th wk) or 12 wk (AB 12th wk). Sham-operated animals served as controls. Aortic debanding procedure was performed after the 6th experimental week (debanded 12th wk) to investigate the regression of LVH. Pressure unloading resulted in significant reduction of LVH (heart weight-to-tibial length ratio: 0.38 ± 0.01 vs. 0.58 ± 0.02 g/mm, cardiomyocyte diameter: 18.3 ± 0.1 vs. 24.1 ± 0.8 μm debanded 12th wk vs. AB 12th wk, P < 0.05), attenuated the extracellular matrix remodeling (Masson's score: 1.37 ± 0.13 vs. 1.73 ± 0.10, debanded 12th wk vs. AB 12th wk, P < 0.05), provided protection against the diastolic dysfunction, and reversed the maladaptive contractility augmentation (slope of end-systolic pressure-volume relationship: 1.39 ± 0.24 vs. 2.04 ± 0.09 mmHg/μl, P < 0.05 debanded 12th wk vs. AB 6th wk, P < 0.05). In addition, myocardial reverse remodeling was also associated with preserved ventriculoarterial coupling and increased mechanical efficiency (50.6 ± 2.8 vs. 38.9 ± 2.5%, debanded 12th wk vs. AB 12th wk, P < 0.05), indicating a complete functional and mechanoenergetic recovery. According to our best knowledge, this is the first study demonstrating that the regression of LVH is accompanied by maintained cardiac mechanoenergetics.

Regression of cardiac hypertrophy by granulocyte colony-stimulating factor-stimulated interleukin-1β synthesis

AIMS

Aortic stenosis causes cardiac hypertrophy and fibrosis, which often persists despite pressure unloading after aortic valve replacement. The persistence of myocardial fibrosis in particular leads to impaired cardiac function and increased mortality. We investigated whether granulocyte colony-stimulating factor (G-CSF) beneficially influences cardiac remodelling after pressure unloading.

METHODS AND RESULTS

Left ventricular hypertrophy was induced by transverse aortic constriction in C57bl6 mice followed by debanding after 8 weeks. This model closely mimics aortic stenosis and subsequent aortic valve replacement. After debanding, mice were treated with either G-CSF or saline injection. Granulocyte colony-stimulating factor treatment significantly improved systolic (ejection fraction 70.48 ± 1.17 vs. 58.41 ± 1.56%, P < 0.001) and diastolic (E/E' 26.0 ± 1.0 vs. 32.6 ± 0.8, P < 0.05) function. Furthermore, cardiac fibrosis was significantly reduced in G-CSF-treated mice (collagen-I area fraction 7.96 ± 0.47 vs. 11.64 ± 1.22%, P < 0.05; collagen-III area fraction 10.73 ± 0.99 vs. 18.46 ± 0.71%, P < 0.001). Direct effects of G-CSF on cardiac fibroblasts or a relevant transdifferentiation of mobilized bone marrow cells could be excluded. However, a considerable infiltration of neutrophils was observed in G-CSF-treated mice. This sterile inflammation was accompanied by a selective release of interleukin-1 β (IL-1β) in the absence of other proinflammatory cytokines. In vitro experiments confirmed an increased expression of IL-1β in neutrophils after G-CSF treatment. Interleukin-1β directly induced the expression of the gelatinases matrix metalloproteinase-2 (MMP-2) and MMP-9 in cardiac fibroblasts thereby providing the regression of cardiac fibrosis.

CONCLUSION

Granulocyte colony-stimulating factor treatment improves the cardiac function and leads to the regression of myocardial fibrosis after pressure unloading. These findings reveal a previously unknown mechanism of fibrosis regression. Granulocyte colony-stimulating factor might be a potential pharmacological treatment approach for patients suffering from congestive heart failure after aortic valve replacement, although further basic research and clinical trials are required in order to prove beneficial effects of G-CSF in the human organism.

Impact of concomitant aortic regurgitation on long-term outcome after surgical aortic valve replacement in patients with severe aortic stenosis

Background

Prognostic value of concomitant aprtic regurgitation (AR) in patients operated for severe aortic stenosis (AS) is not clarified. The aim of this study was to prospectively examine the impact of presence and severity of concomitant AR in patients operated for severe AS on long-term functional capacity, left ventricular (LV) function and mortality.

Methods

Study group consisted of 110 consecutive patients operated due to severe AS. The patients were divided into AS group (56 patients with AS without AR or with mild AR) and AS+AR group (54 patients with AS and moderate, severe or very severe AR). Follow-up included clinical examination, six minutes walk test (6MWT) and echocardiography 12 and 104 months after AVR.

Results

Patients in AS group had lower LV volume indices throughout the study than patients in AS+AR group. Patients in AS group did not have postoperative decrease in LV volume indices, whereas patients in AS+AR group experienced decrease in LV volume indices at 12 and 104 months. Unlike LV volume indices, LV mass index was significantly lower in both groups after 12 and 104 months as compared to preoperative values. Mean LVEF remained unchanged in both groups throughout the study. NYHA class was improved in both groups at 12 months, but at 104 months remained improved only in patients with AS. On the other hand, distance covered during 6MWT was longer at 104 months as compared to 12 months only in AS+AR group (p = 0,013), but patients in AS group walked longer at 12 months than patients in AS+AR group (p = 0,002). There were 30 deaths during study period, of which 13 (10 due to cardiovascular causes) in AS group and 17 (12 due to cardiovascular causes) in AS+AR group. Kaplan-Meier analysis showed that the survival probability was similar between the groups. Multivariate analysis identified diabetes mellitus (beta 1.78, p = 0.038) and LVEF < 45% (beta 1.92, p = 0.049) as the only independent predictor of long-term mortality.

Conclusion

Our data indicate that the preoperative presence and severity of concomitant AR has no influence on long-term postoperative outcome, LV function and functional capacity in patients undergoing AVR for severe AS.

Effect of aortic valve surgery on left ventricular diastole assessed by echocardiography and neuroendocrine response: percutaneous versus surgical approach

OBJECTIVES

Aortic valve implantation through peripheral vascular access is an option for high-risk patients with severe aortic valve stenosis. The authors aimed to compare the acute effect of endovascular and surgical aortic valve procedures on left ventricular diastolic function.

DESIGN

A case-matched, nonrandomized study.

SETTING

A university hospital.

PARTICIPANTS

Patients with aortic stenosis.

INTERVENTIONS

B-natriuretic peptide was measured in 30 patients with a logistic EuroSCORE > or =20% undergoing endovascular aortic valve implantation. Patients were case matched (age, mitral flow propagation velocity, mitral annulus early diastolic velocity, and B-natriuretic peptide measurement) with 30 control patients undergoing surgical aortic valve replacement through sternotomy. Left ventricular diastole was evaluated initially and after valve procedures with echocardiography by mitral flow propagation velocity and mitral annulus early diastolic velocity.

MEASUREMENTS AND MAIN RESULTS

B-natriuretic peptide was similar preoperatively in the 2 groups (346 [188-438] v 367 [211-458] pg/mL) and higher (p = 0.006) in the surgical group postoperatively (389.5 [237-479] v 710.5 [389-822] pg/mL), with a postprocedural statistically significant increase only in the surgical group. Diastolic function was similar in the 2 groups preoperatively, improved postoperatively in the endovascular group, and worsened in the surgical group.

CONCLUSIONS

B-natriuretic peptide increased after surgical but not after endovascular aortic valve replacement. Furthermore, endovascular aortic valve implantation acutely improved left ventricular diastolic function as documented by increases in mitral flow propagation velocity and mitral annulus early diastolic velocity.

Impact of Left Ventricular Loading Conditions on Myocardial Deformation Parameters: Analysis of Early and Late Changes of Myocardial Deformation Parameters after Aortic Valve Replacement

Myocardial deformation imaging is used to assess regional left ventricular (LV) function. We sought to define the impact of changes in LV loading conditions on myocardial deformation parameters. Aortic valve replacement in patients with different aortic valve pathologies was used as a model to assess the impact of preload and afterload changes. In 53 patients scheduled for aortic valve replacement serial echocardiographic studies were performed preoperatively and postoperatively (within 7 days and at 6 months). Parasternal short-axis views were acquired. Using novel computer software radial and circumferential strain and strain rate were determined as parameters of myocardial deformation for each segment of the LV and were subsequently averaged. Immediately postoperatively there was a relative increase of radial strain by 4.5 +/- 1.8% after valve replacement for aortic stenosis (AS) (P < .001), a relative decrease of 9.4 +/- 7.7% after valve replacement for aortic regurgitation (aortic insufficiency [AI]) (P < .001), and unchanged radial strain after valve replacement for AS and aortic regurgitation. During the subsequent 6 months of follow-up, there was additional relative increase of radial strain by 5.2 +/- 3.1% in the AS group (P < .001), by 12.0 +/- 13.7% in the AI group (P < .01), and by 5.6 +/- 3.4% in the AS and AI group (P < .001). Similar changes were observed for the other strain and strain rate parameters. In conclusion, myocardial deformation parameters change significantly immediately after aortic valve replacement for AS or AI indicating a dependency of determined myocardial deformation parameters on LV preload and afterload.

Aortic Valve Replacement for Aortic Insufficiency: Valve Type as a Determinant of Systolic Strain Recovery

BACKGROUND AND AIM

Left ventricular (LV) 3D systolic strain decreases in absolute value postoperatively and does not recover in patients who undergo aortic valve replacement (AVR) for chronic aortic insufficiency (AI). We investigated whether choice of valve prosthesis (mechanical [St. Jude], bioprosthetic [bovine pericardial], Ross procedure) had a significant impact on strain recovery in this surgical population.

METHODS

MRI with tissue-tagging was performed on 14 patients with chronic AI both before and 28 +/- 13 months after AVR. Average values of LV systolic strain and end-systolic stress (ESS) were computed from MRI data for the LV. Three types of prosthetic valve were examined (Ross procedure n = 4, bovine pericardial n = 5, and St. Jude n = 5).

RESULTS

Overall, systolic strain, ESS, LV volumes, ejection fraction, and LV mass all changed significantly following AVR. Comparisons between individual valve types revealed no differences in any of these measurements. Patients who received a mechanical valve had a greater decrease in the absolute value of systolic strain following surgery compared to patients from the nonmechanical group (Ross procedure and bioprosthetic valve). Comparisons between the Ross group and the prosthetic group (St. Jude and bioprosthetic) produced no significant differences in strain, ESS, LV volume, and mass.

CONCLUSIONS

These early results suggest that valve prosthetic type may be a factor in efforts to improve strain recovery after AVR for AI, although further investigation is warranted. MRI with tissue-tagging may be a useful tool for comparing the impact of prosthetic valve choice on incompletely recovered systolic strain following AVR for chronic AI.

[Outcome and prognosis of surgical treatment in patients with severe aortic stenosis with respect to the duration and severity of associated aortic regurgitation]

INTRODUCTION

It is not clear whether associated aortic regurgitation (AR) should be regarded as a risk factor in patients undergoing surgery for severe aortic stenosis (AS). Some authors have suggested that morbidity and mortality are increased in these patients as compared to patients operated for pure AS, whereas others have found no difference of the outcome and prognosis between these groups.

OBJECTIVE

This study made an attempt to compare the outcome and prognosis following the surgical intervention in patients with severe AS and associated AR and those operated for pure AS, as well as to determine predictive value of clinical, functional and echocardiographic data for the outcome of surgery.

METHODS

Study population consisted of 122 consecutive patients operated at Dedinje Cardiovascular Institute during 1999 due to severe AS, defined as mean gradient over aortic valve >30 mmHg. The patients were divided into AS group (63 patients with AS without AR or with mild AR) and AS+AR group (59 patients with AS and moderate, severe or very severe AR). The patients were subjected to control clinical, functional and echocardiographic examinations 12 and 18 months following the surgery.

RESULTS AND DISCUSSION

Preoperatively, the patients in AS group were older and had coronary artery disease more frequently, whereas patients in AS+AR group had higher left ventricular volumes and mass. Preoperative NYHA class, ejection fraction, mean gradient over aortic valve, type and size of the implanted mechanical prosthesis, and the incidence of associated coronary artery bypass surgery were similar between the groups. Similarly, the operative mortality was similar in AS and AS+AR groups (1.6% vs 8.5%, respectively, p=0.11). Twelve months postoperatively, there were no difference of average NYHA class and NYHA class III/IV between the groups. The patients in AS+AR group were unable to walk >300 meters on 6 minute walk test more frequently than those in AS group (64% vs. 36%, respectively; p=0.043). Eighteen months postoperatively, NYHA class III/IV was found more frequently in AS+AR than in AS group (26% vs. 8%, respectively; p=0.0343). In patients with associated AR, there was no difference of NYHA class with respect to the severity of AR (p=0.815). Multivariate analysis found the association of more than mild AR as an independent predictor of poor functional capacity, irrespective of its severity.

CONCLUSION

Patients with severe AS and associated AR have poorer postoperative functional capacity as compared to patients operated for pure AS.

Systematic review of the outcome of aortic valve replacement in patients with aortic stenosis

BACKGROUND

After the establishment of aortic valve replacement procedure for aortic stenosis, there are heterogeneous studies and varying reports on outcome. An analysis that compares individual studies to summarize the overall effect is still lacking. This study systematically analyzes the change in left ventricular (LV) mass index and ejection fraction after aortic valve replacement in adult patients.

METHODS

We performed MEDLINE and bibliographic searches and included 27 articles published between 1980 and 2003 about the outcome of valve replacement in 1546 aortic stenosis patients. To allow comparisons, we stratified the patients into early (0-6 months), intermediate (7-24 months), and late (25-120 months) follow-up groups for the analysis of both LV mass regression and ejection fraction. We separately analyzed five articles that reported groups of patients with low preoperative ejection fraction.

RESULTS

Increase in ejection fraction after surgery is more pronounced in the patients that have low preoperative ejection fraction (28% +/- 4.3%(preop) vs 40% +/- 9.4%(6-41 months) follow-up). Patients with normal or high preoperative ejection fraction have variable outcomes. However, regression of LV mass is uniformly achieved regardless of age, sex, time of operation, or types of valve substitute. Furthermore, LV mass regresses predominantly within the first 6 months after surgery (g/m2, 181 +/- 25.8(preop) vs 124 +/- 27(6 months), 117 +/- 15(24 months), and 113 +/- 14(120 months) follow-up).

CONCLUSIONS

This systematic review supports the concept that aortic stenosis patients with LV dysfunction show a clear functional improvement after aortic valve replacement. Ventricles regress rapidly and reach their approximate final size within the first 6 months of surgery.

Left ventricular remodeling early after aortic valve replacement: differential effects on diastolic function in aortic valve stenosis and aortic regurgitation

OBJECTIVES

The aim of this study was to evaluate the effect of aortic valve replacement (AVR) on left ventricular (LV) function and LV remodeling, comparing patients with aortic valve stenosis to patients with aortic regurgitation.

BACKGROUND

Aortic valve disease is associated with eccentric or concentric LV hypertrophy and changes in LV function. The relationship between LV geometry and LV function and the effect of LV remodeling after AVR on diastolic filling, in patients with aortic valve stenosis compared with aortic regurgitation, are largely unknown.Nineteen patients with aortic valve disease (12 aortic valve stenosis, 7 aortic regurgitation) were studied using magnetic resonance imaging to assess LV geometry and LV function before and 9 +/- 3 months after AVR. Ten age-matched healthy males served as control subjects.

RESULTS

Before AVR, the ratio between left ventricular mass index (LVMI) and left ventricular end-diastolic volume index (LVEDVI) was only increased in patients with aortic valve stenosis (1.37 +/- 0.16 g/ml) compared with control subjects (0.93 +/- 0.08 g/ml, p < 0.05). After AVR, LVMI/LVEDVI decreased significantly in aortic valve stenosis (to 1.15 +/- 0.14 g/ml, p < 0.0001), but increased significantly in aortic regurgitation (1.02 +/- 0.20 g/ml to 1.44 +/- 0.27 g/ml, p < 0.0001). Before AVR, diastolic filling was impaired in both aortic valve stenosis and aortic regurgitation. Early after AVR, diastolic filling improved in patients with aortic valve stenosis, whereas patients with aortic regurgitation showed a deterioration in diastolic filling.

CONCLUSIONS

Early after AVR, patients with aortic valve stenosis show a decrease in both LVMI and LVMI/LVEDVI and an improvement in diastolic filling, whereas in patients with aortic regurgitation, LVMI decreases less rapidly than LVEDVI, causing concentric remodeling of the LV, most likely explaining the observed deterioration of diastolic filling in these patients.

Four year follow up of aortic valve replacement for isolated aortic stenosis: a link between reduction in pressure overload, regression of left ventricular hypertrophy, and diastolic function

OBJECTIVE

To evaluate changes in left ventricular function and the impact of ventricular hypertrophy and pressure gradient early and late after aortic valve replacement in patients with isolated aortic stenosis.

DESIGN

41 patients with isolated aortic stenosis and normal systolic function underwent cross sectional and Doppler echocardiography two months before and two weeks and four years after aortic valve replacement.

RESULTS

Early after the operation, left ventricular mass index (mean (SD)) decreased from 187 (44) g/m(2) to 179 (46) g/m(2), because of a reduction in end diastolic diameter (p < 0.05). Aortic pressure gradients were reduced, as expected. Isovolumic relaxation time was reduced from 93 (20) ms to 78 (12) ms, and deceleration time from 241 (102) ms to 205 (77) ms (p < 0.05). At four years, left ventricular mass index was further reduced to 135 (30) g/m(2) (p < 0.01) as a result of wall thickness reduction in the interventricular septum (from 14 (1.6) mm to 12 (1.4) mm, p < 0.01) and the posterior wall (from 14 (1.6) mm to 12 (1.3) mm, p < 0.01). Diastolic function, expressed by a reduction in isovolumic relaxation time from 93 (20) ms to 81 (15) ms (p < 0.01) and deceleration time from 241 (102) ms to 226 (96) ms (p < 0.05), remained improved. Prolonged isovolumic relaxation time was associated with significant septal and posterior wall hypertrophy (wall thickness > 13 mm) (p < 0.05), whereas prolonged deceleration time was related to high residual gradient (peak gradient > 30 mm Hg ) (p < 0.01).

CONCLUSIONS

Left ventricular diastolic function improves early after surgery for aortic stenosis in parallel with the reduction in the aortic gradient. However, prolongation of Doppler indices of myocardial relaxation and ventricular filling is observed in patients with significant left ventricular hypertrophy and a residual pressure gradient early after surgery. At four years postoperatively, diastolic function remains improved.

Coronary flow reserve improves after aortic valve replacement for aortic stenosis: an adenosine transthoracic echocardiography study

OBJECTIVES

The goal of this study was to assess coronary flow reserve (CFR) before and after aortic valve replacement (AVR).

BACKGROUND

Coronary flow reserve is impaired under conditions of left ventricular (LV) hypertrophy. It is not known whether CFR improves with regression of LV hypertrophy in humans.

METHODS

We investigated 35 patients with pure aortic stenosis, LV hypertrophy and normal coronary arteriograms. Patients underwent adenosine transthoracic echocardiography on two occasions--immediately before AVR and six months postoperatively. Left ventricular mass, distal left anterior descending coronary artery (LAD) diameter, flow and CFR were assessed on each occasion.

RESULTS

Distal LAD diameter was successfully imaged in 30 patients (86%), and blood flow was successfully imaged in 27 (77%). Paired data were subsequently available in 24 patients, of whom 14 were men, mean age 68.1+/-12.5 years, body mass index 24.5+/-2.0 kg/m2, aortic valve gradient 93+/-32 mm Hg. Pre- to post-AVR a significant decrease was seen in LV mass (271+/-38 vs. 236+/-32g, p<0.01) and LV mass index (154+/-21 vs. 134+/-21 g/m2, p< 0.01). Distal LAD diameter fell from 2.27+/-0.37 to 2.23+/-0.35 mm, p = 0.08). Pre- to post-AVR there was no significant change in resting parameters of peak diastolic velocity (0.43+/-0.16 vs. 0.41+/-0.11 m/s), distal LAD flow 23.3+/-10.1 vs. 20.9+/-5.2 ml/min or distal LAD flow scaled for LV mass (8.7+/-3.8 vs. 9.0+/-2.5 ml/min/100 g LV mass), but there was significant increase in hyperemic peak diastolic velocity (0.71+/-0.26 vs. 1.08+/-0.24 m/s; p<0.01), distal LAD flow (37.8+/-11.3 vs. 53.5+/-16.1 ml/min; p<0.01) and distal LAD flow scaled for LV mass (14.3+/-5.0 vs. 23.3+/-8.5 ml/min/100 g LV mass; p<0.01). Coronary flow reserve, therefore, increased from 1.76+/-0.5 to 2.61+/-0.7.

CONCLUSIONS

Coronary flow reserve increases after AVR for aortic stenosis. This increase occurs in tandem with regression of LV hypertrophy.