Changes in left ventricular mass and function after aortic valve replacement: a comparison between stentless and stented bioprosthetic valves

Regression of cardiac hypertrophy in health and disease: mechanisms and therapeutic potential

Left ventricular hypertrophy is a leading risk factor for cardiovascular morbidity and mortality. Although reverse ventricular remodelling was long thought to be irreversible, evidence from the past three decades indicates that this process is possible with many existing heart disease therapies. The regression of pathological hypertrophy is associated with improved cardiac function, quality of life and long-term health outcomes. However, less than 50% of patients respond favourably to most therapies, and the reversibility of remodelling is influenced by many factors, including age, sex, BMI and disease aetiology. Cardiac hypertrophy also occurs in physiological settings, including pregnancy and exercise, although in these cases, hypertrophy is associated with normal or improved ventricular function and is completely reversible postpartum or with cessation of training. Studies over the past decade have identified the molecular features of hypertrophy regression in health and disease settings, which include modulation of protein synthesis, microRNAs, metabolism and protein degradation pathways. In this Review, we summarize the evidence for hypertrophy regression in patients with current first-line pharmacological and surgical interventions. We further discuss the molecular features of reverse remodelling identified in cell and animal models, highlighting remaining knowledge gaps and the essential questions for future investigation towards the goal of designing specific therapies to promote regression of pathological hypertrophy.

Predictors and Changes in Cardiac Hemodynamics and Geometry With Transcatheter Aortic Valve Implantation

The introduction of transcatheter aortic valve implantation (TAVI) has revolutionized the treatment of patients with severe aortic stenosis (AS). However, despite the great clinical success of TAVI, less is known about the cardiac hemodynamics and structural changes to post-TAVI. We analyzed patients with AS who had a transthoracic echocardiography at most 6 months before index TAVI and follow-up transthoracic echocardiography 9 to 18 months later, performed at Duke University Medical Center from 2012 to 2014. A total of 152 TAVI patients with a median age of 81 years (median interquartile range 74 to 86) were included. TAVI resulted in the reduction of left ventricle (LV) mass index (g/m²), median (interquartile range) 130 (115 to 157) pre versus 106 (85 to 135) post, p <0.001; LV end-diastolic volume (ml) 127 (105 to 143) pre versus 120 (100 to 143) post, p = 0.013; and LV end-systolic volume (ml) 55 (38 to 77) pre versus 45 (40 to 65) post, p = 0.027. TAVI also significantly improved LV global longitudinal strain (%) -14.4 (-11.3, -15.5) pre versus -14.8 (-12.2, -16.6) post (p <0.001, respectively). Post-TAVI LV mass regression was predicted by baseline LV mass and LV global longitudinal strain whereas post-TAVI LV ejection fraction was predicted by baseline LV ejection fraction, LV mass, and post-TAVI paravalvular leak. In conclusion, TAVI results in significant cardiac hemodynamic, geometrical, and functional changes at approximately 1-year postprocedure for patients with AS. Better baseline myocardial structure and function leads to more reverse remodeling.

Early regression of severe left ventricular hypertrophy after transcatheter aortic valve replacement is associated with decreased hospitalizations

OBJECTIVES

This study sought to examine the relationship between left ventricular mass (LVM) regression and clinical outcomes after transcatheter aortic valve replacement (TAVR).

BACKGROUND

LVM regression after valve replacement for aortic stenosis is assumed to be a favorable effect of LV unloading, but its relationship to improved clinical outcomes is unclear.

METHODS

Of 2,115 patients with symptomatic aortic stenosis at high surgical risk receiving TAVR in the PARTNER (Placement of Aortic Transcatheter Valves) randomized trial or continued access registry, 690 had both severe LV hypertrophy (left ventricular mass index [LVMi] ≥ 149 g/m(2) men, ≥ 122 g/m(2) women) at baseline and an LVMi measurement at 30-day post-TAVR follow-up. Clinical outcomes were compared for patients with greater than versus lesser than median percentage change in LVMi between baseline and 30 days using Cox proportional hazard models to evaluate event rates from 30 to 365 days.

RESULTS

Compared with patients with lesser regression, patients with greater LVMi regression had a similar rate of all-cause mortality (14.1% vs. 14.3%, p = 0.99), but a lower rate of rehospitalization (9.5% vs. 18.5%, hazard ratio [HR]: 0.50, 95% confidence interval [CI]: 0.32 to 0.78; p = 0.002) and a lower rate of rehospitalization specifically for heart failure (7.3% vs. 13.6%, p = 0.01). The association with a lower rate of rehospitalization was consistent across subgroups and remained significant after multivariable adjustment (HR: 0.53, 95% CI: 0.34 to 0.84; p = 0.007). Patients with greater LVMi regression had lower B-type natriuretic peptide (p = 0.002) and a trend toward better quality of life (p = 0.06) at 1-year follow-up than did those with lesser regression.

CONCLUSIONS

In high-risk patients with severe aortic stenosis and severe LV hypertrophy undergoing TAVR, those with greater early LVM regression had one-half the rate of rehospitalization over the subsequent year compared to those with lesser regression.

Parathyroid hormone is associated with the LV mass after aortic valve replacement

AIMS

LV hypertrophy (LVH) is frequent after aortic valve replacement (AVR) and is often associated with comorbidities, including hypertension, obesity, renal failure and prosthesis-patient mismatch (PPM). However, whether other biological mechanism(s) may participate to LVH after AVR is still unknown. Parathyroid hormone (PTH) may play a role in LVH. However, it is presently unknown whether PTH is associated with LVH in patients that have undergone an AVR.

METHODS

In this cross-sectional study, 195 patients have been investigated at a mean of 8 ± 3.5 years following AVR. LV function and mass were evaluated by Doppler echocardiography. The plasma levels of PTH, 25-hydroxyvitamin D (25-OHD), calcium and phosphate were measured.

RESULTS

There were 102 (52%) patients with LVH after AVR. In univariate analyses, PTH blood level was associated with LV mass (LVMi) and LVH. After adjustment for other risk factors, elevated PTH remained associated with LVMi (p=0.003) and LVH (p=0.02). In turn, the blood levels of 25-OHD and the renal function (GFR) were independently and inversely related to the blood level of PTH.

CONCLUSIONS

After AVR, the level of PTH is independently associated with LVH. In turn, the level of PTH is related with the renal function and the level of 25-OHD.

Acquired aortic stenosis

Aortic stenosis is the most commonly encountered valvular disease in the elderly, with approximately 2-3% of individuals over 65 years of age afflicted. The most common cause of acquired aortic stenosis is calcific degeneration, characterized by a slowly progressive, asymptomatic period which can last decades. Once symptomatic, the clinical manifestation of aortic stenosis is from functional obstruction of left ventricular outflow and the additional hemodynamic effects on the left ventricle and vasculature. With advances in echocardiography, individuals with aortic stenosis are increasingly diagnosed in the asymptomatic latent period. However, echocardiographic measures alone cannot identify clinically significant outflow obstruction as there is considerable overlap in hemodynamic severity between symptomatic and asymptomatic individuals. Current clinical guidelines predicate the timing of surgical valve replacement on the presence or absence of symptoms. Management for symptomatic, significant stenosis is surgical valve replacement as there are no current medical therapies reliably proven to decrease aortic stenosis severity or improve long-term outcomes. However, recent retrospective studies have demonstrated an association between atherosclerotic disease risk factors, such as hyperlipidemia and aortic stenosis. Given these findings, there are now advocates for prospective primary prevention trials for aortic stenosis in patients with mild or moderate valvular disease. The following paper will discuss etiology, diagnostic evaluation and therapeutic options of acquired aortic stenosis. This review will discuss etiology, diagnostic evaluation, and therapeutic options of acquired aortic stenosis.

Magnetic resonance imaging versus echocardiography to ascertain the regression of left ventricular hypertrophy after bioprosthetic aortic valve replacement: results of the REST study

OBJECTIVES

To compare the decrease in left ventricular mass index (LVMI) by magnetic resonance imaging (MRI) versus transthoracic echocardiography (TTE) after aortic valve replacement (AVR) for severe aortic stenosis with Epic and Epic Supra stented porcine bioprostheses (St Jude Medical, Inc, St Paul, Minn).

METHODS

This prospective multicenter study enrolled 149 patients who underwent AVR between January 2006 and February 2008. TTE and cardiac MRI measurements of LVMI were made at baseline and at 6 months of follow-up and were compared. Changes in mean pressure gradients were examined using TTE.

RESULTS

TTE measurements of LVMI were 48% to 63% higher than the MRI measurements. A decrease in LVMI from 137 ± 32 to 95 ± 16 g/m(2) with the Epic and from 139 ± 29 to 104 ± 28 g/m(2) with the Epic Supra valves (P < .0001 for both comparisons) was measured by TTE. Cardiac MRI revealed decreases in LVMI from 84 ± 20 to 64 ± 12 g/m(2) and from 86 ± 27 to 64 ± 17 g/m(2) with the Epic and Epic Supra valves, respectively (P < .0001 for both comparisons). TTE revealed a significant regression of mean pressure gradients from 51.6 ± 15.3 to 15.5 ± 5.2 mm Hg with the Epic and from 46.7 ± 19.4 to 17.9 ± 12.8 mm Hg with the Epic supra (P < .0001 for both comparisons).

CONCLUSIONS

A significant decrease in LVMI was measured after AVR with all sizes of both bioprosthetic models. Because of the overestimation of the decrease in LVMI by the Devereux formula, as well as the higher accuracy and reproducibility of cardiac MRI measurements, the latter should be preferred to TTE. An ultimate validation of this thesis could only be done comparing each of these modalities with pathologic examination.

Stentless valves for aortic valve replacement: where do we stand?

PURPOSE OF REVIEW

Following more than a decade's experience with stentless valves and the development of better profiled stented valves, the article discusses the advantages of stentless valves regarding hemodynamic performance, left ventricular mass regression, durability and survival.

RECENT FINDINGS

Recent studies show that stentless valves remain hemodynamically superior compared with modern porcine stented valves. This superiority is, however, rarely reported in comparison with modern pericardial stented valves. In general, patient-prosthesis mismatch is less frequent in stentless vs. stented valves. Recent randomized trials comparing stentless valves and modern stented valves show equivalent left ventricular mass regression at 1 year. At 10 years, stentless valve durability is excellent and comparable with that of stented valves. Recent comparative studies do not confirm the previously reported midterm survival advantages of stentless valves.

SUMMARY

Improvement of stented valves has significantly reduced the hemodynamic differences between them and their stentless counterpart. Patients with small aortic annulus, however, should benefit from a stentless valve due to the better expected gradients and lower risk of patient-prosthesis mismatch. Midterm results suggest equivalent durability and survival for both prosthesis types but additional and longer-term trials are necessary to confirm these results.

The Stentless Freestyle Bioprosthesis: Impact of Age Over 80 Years on Quality of Life, Perioperative, and Mid-Term Outcome

BACKGROUND

The steadily increasing life expectancy of the population in the Western World, together with the progress in noninvasive diagnostic methods and operating techniques lead to an increase in aortic valve surgery in elderly people.

AIM OF THE STUDY

Is there an increased risk of adverse perioperative and mid-term outcome for octogenarians and do they benefit from aortic valve replacement (AVR) with stentless bioprostheses?

METHODS

Between 1996 and 2002, 503 patients older than 60 years underwent AVR with a stentless Freestyle bioprosthesis. Seventy-six of them were older than 80 years. The risk of operative mortality, perioperative complications, valve-related morbidity for octogenarians was determined by multivariate logistic regression.

RESULTS

In general, risk-adjusted analyses did not reveal an increased risk of operative mortality (p = 0.4), postoperative atrial fibrillation (p = 0.2), prolonged ventilation (p = 0.5), prolonged stay in the intensive care unit (p = 0.3), or mid-term valve-related morbidity as prosthetic valve endocarditis (p = 0.2), reoperation (p = 0.4), bleeding events (p = 0.1), and stroke (p = 0.8) for octogenarians. Continuously increasing age was an independent risk factor for postoperative neurological complications (OR = 1.8 per 10 years, p = 0.04). Quality of life was equal to or better than the general population of the same age. Median survival time of octogenarians was 5.2 +/- 0.5 years.

CONCLUSIONS

Except for postoperative neurological complications, octogenarians receiving stentless bioprostheses had no increased risk of adverse perioperative and mid-term outcome in comparison to younger patients. As quality of life and life expectancy after AVR with stentless valves were equal to the general population, AVR with stentless bioprostheses should not be withheld from octogenarians.

Impact of Stentless Aortic Valves on Left Ventricular Function and Hypertrophy: Current Best Available Evidence

Past four decades have seen a gradual evolution in aortic valve replacement surgery. The ideal valve substitute should combine central flow, low transvalvular gradient, low thrombogenicity, durability, easy availability, resistance to infection, freedom from anticoagulation, and easy implantability. Although there are several types of valves available to replace the diseased aortic valve-autograft, allograft, xenograft, mechanical, and bioprosthetic valves-none is ideal. On one end of the spectrum is the pulmonary autograft, which comes closest to achieving these goals, but creates a double valve procedure for single valve disease, while on the other end are the mechanical valves and stented tissue valves, which allow easy "off the shelf" availability as well as easy implantability but are limited by the potential drawback of causing intrinsic obstruction to some extent because of the space occupied by the stent and sewing ring. Stentless xenograft aortic valves have been developed as a compromise between these ends of the valve spectrum. Stentless aortic valves have been reported to provide more physiologic hemodynamic behavior and cause more timely and thorough regression of ventricular hypertrophy. This review article attempts to evaluate current best available evidence from randomized controlled trials to assess the impact of stentless aortic valves on left ventricular function and hypertrophy.

Ross Procedure and Left Ventricular Mass Regression

Background— Return of left ventricular mass to normal is considered to be a favorable result of aortic valve replacement. The Ross procedure provides near normal hemodynamics and thus allows studies of left ventricular (LV) reverse remodeling. LV mass regression may be influenced by surgical technique (subcoronary [SC] versus root replacement [RR]).

Methods and Results— Data from the German Ross Registry were analyzed. A total of 646 patients (mean age: 43.6±12.7 years, range: 16 to 71 years; SC technique n=295, RR technique n=351) underwent a Ross procedure in 7 participating centers from 1990 to 2004. The patients underwent preoperative and postoperative echocardiographic evaluations. Mean follow-up time was 3.5±2.5 years (range 0.12 to 13.7 years). Follow-up completeness was 97%. The LV mass index (LVMI) decreased significantly during follow-up in both groups (SC: 209±53 preoperatively to 154±48 at 1-year follow-up, [ P <0.01 versus preoperative values] to 149±51g/m 2 at 2-year follow-up, [ P =NS 1-year versus 2-year follow-up] versus RR: from 195±56 preoperatively to 144±51 at 1-year follow-up [ P <0.01 versus preoperative values] to 140±49g/m 2 [ P =NS 1-year versus 2-year follow-up]). LVMI regression remained stagnant 1 year after the Ross procedure in most patients in both groups. On the basis of multivariate analysis, predictors for incomplete LVMI regression after the autograft procedure were high preoperative LVMI, smoking, and uncontrolled diastolic hypertension.

Conclusions— At mid-term echocardiographic follow-up, patients of both groups had favorable autograft hemodynamics. Risk factors for incomplete postoperative LVMI regression in our study were smoking and persistent diastolic hypertension. This emphasizes the importance of cessation of smoking and treatment of arterial hypertension, even in younger patients, after corrected aortic valve disease.

Mid term outcome and quality of life after aortic valve replacement in elderly people: mechanical versus stentless biological valves

OBJECTIVE

To assess the benefit for patients older than 65 years of aortic valve replacement with stentless biological heart valves in comparison with mechanical valves.

DESIGN

Multiple regression analysis of a retrospective follow up study.

SETTING

Single cardiothoracic centre.

PATIENTS

Between 1996 and 2001, 392 patients with a mean age of 74 years underwent aortic valve replacement with stentless Freestyle bioprostheses or mechanical St Jude Medical prostheses.

MAIN OUTCOME MEASURE

Operative mortality and morbidity, postoperative morbid events, mid term survival, and New York Heart Association (NYHA) class improvement, and quality of life.

RESULTS

No significant differences were found between patients receiving stentless biological valves and patients receiving mechanical prostheses. However, analysis of subgroups showed that patients older than 75 years with mechanical valves had an increased risk of major bleeding events (p = 0.007). Patients requiring anticoagulation by means of coumarin had a twofold increased risk of an impaired emotional reaction (p = 0.052). However, for patients who received a mechanical valve for severe combined aortic valve disease a survival advantage (p = 0.045) and a decreased risk of prolonged ventilation (p = 0.001) was observed. On the other hand, patients receiving a stentless bioprosthesis had an increased risk of a prolonged stay in intensive care (p = 0.04) and stroke (p = 0.01) if they had severely reduced cardiac function (NYHA class IV).

CONCLUSIONS

Elderly people receiving stentless bioprostheses benefit emotionally because of the avoidance of coumarin. However, in patients with severe hypertrophied ventricles and extraordinary calcifications, stentless bioprostheses should be chosen with caution.

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.

Risk in elderly patients after stentless versus stented aortic valve surgery

Recent studies suggest that the hemodynamic advantage of stentless bioprostheses over the stented type improves long-term survival after aortic valve replacement, but the more complex and time-consuming implantation technique may increase the risks of operative death and postoperative complications. Between April 1996 and June 2001, 519 patients with a mean age of 76 +/- 5 years underwent aortic valve replacement using a stentless (Medtronic Freestyle, n = 277) or stented bioprosthesis (Medtronic Mosaic, n = 242). Multiple logistic regression analysis considering different patient populations revealed no increased risk of operative death, postoperative complications, or neurological impairment after implantation of a stentless bioprosthesis. Survival curves in respect of 367 patients who underwent aortic valve replacement up to September 2000 and were followed up for 3 years were not different (p = 0.98). As the patients were elderly, improved survival due to implantation of a stentless valve could not be demonstrated within this time span.

[Risk of perioperative mortality and complications following biological aortic valve replacement in elderly patients: stented vs unstented bioprotheses]

Recently published studies suggest that the hemodynamic advantage of stentless bioprostheses in comparison to stented bioprostheses positively influence the long-term survival after aortic valve replacement. However, the more complex and time consuming implantation technique may increase the risk of operative death. Between April 1996 and September 2000, 201 patients with the mean age of 75 ± 5 years underwent aortic valve replacement (AVR) with a stentless Medtronic Freestyle Bioprothesis (FP) and 166 patients with a mean age of 77 ± 5 years received a stented Medtronic Mosaic Biopros thesis (MP). Patients requiring concomitant procedures other than coronary artery bypass grafting (CABG) were excluded. The operative mortality was 3.5% after AVR with the FP and 6% after AVR with the MP. Multiple logistic regression analysis considering the different patient populations revealed no increased risk of operative death after AVR with FB (p = 0.46). Previously heart operations (p = 0.046) and emergency operation (p = 0.022) were risk factors for operative death after AVR with the biological bioprostheses. The risk for postoperatively neurological impairment (p = 0.15) and other complications (p = 0.46) was furthermore not increased after implantation of a Freestyle stentless valve. The risk of delayed mobilization (p < 0.001) was 2.4-fold increased for patients after AVR with the Freestyle valve. A positive influence on survival due to the implantation of a stentless Freestyle valve could not be shown within the observed period. However, in spite of the more complex and time-consuming operation technique, the risk of operative death and postoperative complications is not increased after aortic valve replacement with the stentless FB.

Hemodynamic comparison of second- and third-generation stented bioprostheses in aortic valve replacement

BACKGROUND

The hemodynamic performance of aortic replacement prostheses is of extreme importance. There is renewed interest in hemodynamics because of the influence of prosthesis-patient mismatch on left ventricular mass regression and the potential influence on survival.

METHODS

The hemodynamic performance of the second-generation Carpentier-Edwards supraannular porcine and pericardial (Perimount) bioprostheses and the third-generation Medtronic Mosaic porcine bioprosthesis were compared for mean gradient and effective orifice area index. The effective orifice area index of at least 0.85 cm2/M2 was considered as lack of prosthesis-patient mismatch. The study group included included 53 patients with Carpentier-Edwards supraannular porcine, 48 with pericardial, and 98 with Medtronic Mosaic porcine bioprostheses.

RESULTS

The mean gradients were not different between the prostheses by prosthesis size. The Medtronic Mosaic was not provided in size 19. The mean gradients for the prostheses, except in the very large sizes, were all double-digit values. The effective orifice area index was not different between the prostheses but there was a trend toward prosthesis-patient mismatch in smaller size prostheses.

CONCLUSIONS

There was no apparent hemodynamic advantage between porcine and pericardial bioprostheses in the aortic position.

Hemodynamic performance during maximum exercise in adult patients with the ross operation and comparison with normal controls and patients with aortic bioprostheses

This study examines the resting and exercise hemodynamic performance of the pulmonary autografts in the aortic position as well as of the homografts used for right ventricular outflow reconstruction in patients undergoing the Ross operation. Previous studies have reported excellent resting hemodynamics in patients who underwent aortic valve replacement with a pulmonary autograft. However, there are very few studies of their hemodynamic performance during exercise. Twenty adult subjects who underwent the Ross operation and 12 normal control subjects were submitted to maximum romp bicycle exercise. The valve effective orifice areas and transvalvular gradients of both aortic (autograft) and pulmonary (homograft) valves were measured at rest and at peak of maximum exercise using Doppler echocardiography. Valve areas were indexed for body surface area. The hemodynamics of the aortic valve were very similar in Ross subjects and in control subjects at rest and during exercise. However, the indexed valve area of the pulmonary valve at rest was significantly (p < 0.001) lower in the Ross subjects (1.10 +/- 0.46 cm2/ m2) than in the control subjects (1.95 +/- 0.41 cm2/m2), resulting in higher (p = 0.004) mean gradients at rest (Ross: 9 +/- 7 mm Hg vs control: 2 +/- 1 mm Hg) and at peak exercise (Ross: 21 +/- 14 mm Hg vs control: 7 +/- 2 mm Hg). The pulmonary autograft provided excellent hemodynamics in the aortic position either at rest or during maximum exercise, whereas moderately high gradients were found during exercise across the homograft implanted in the pulmonary valve position. Future improvement of the Ross procedure should be oriented toward the search of new methods to prevent the deterioration of the homografts.

Hemodynamic and clinical impact of prosthesis-patient mismatch in the aortic valve position and its prevention

Prosthesis-patient mismatch is present when the effective orifice area of the inserted prosthetic valve is less than that of a normal human valve. This is a frequent problem in patients undergoing aortic valve replacement, and its main hemodynamic consequence is the generation of high transvalvular gradients through normally functioning prosthetic valves. The purposes of this report are to present an update on the concept of aortic prosthesis-patient mismatch and to review the present knowledge with regard to its impact on hemodynamic status, functional capacity, morbidity and mortality. Also, we propose a simple approach for the prevention and clinical management of this phenomenon because it can be largely avoided if certain simple factors are taken into consideration before the operation.