Medium-term determinants of left ventricular mass index after stentless aortic valve replacement

Challenges and opportunities in improving left ventricular remodelling and clinical outcome following surgical and trans-catheter aortic valve replacement

Over the last half century, surgical aortic valve replacement (SAVR) has evolved to offer a durable and efficient valve haemodynamically, with low procedural complications that allows favourable remodelling of left ventricular (LV) structure and function. The latter has become more challenging among elderly patients, particularly following trans-catheter aortic valve implantation (TAVI). Precise understanding of myocardial adaptation to pressure and volume overloading and its responses to valve surgery requires comprehensive assessments from aortic valve energy loss, valvular-vascular impedance to myocardial activation, force-velocity relationship, and myocardial strain. LV hypertrophy and myocardial fibrosis remains as the structural and morphological focus in this endeavour. Early intervention in asymptomatic aortic stenosis or regurgitation along with individualised management of hypertension and atrial fibrillation is likely to improve patient outcome. Physiological pacing via the His-Purkinje system for conduction abnormalities, further reduction in para-valvular aortic regurgitation along with therapy of angiotensin receptor blockade will improve patient outcome by facilitating hypertrophy regression, LV coordinate contraction, and global vascular function. TAVI leaflet thromboses require anticoagulation while impaired access to coronary ostia risks future TAVI-in-TAVI or coronary interventions. Until comparable long-term durability and the resolution of TAVI related complications become available, SAVR remains the first choice for lower risk younger patients.

Stentless aortic valve replacement: current status and future trends

Stentless aortic xenografts were introduced into clinical practice as aortic valve substitutes over a decade ago. Stentless prosthetic valves were expected to provide enhanced durability and more physiologic hemodynamic behavior when compared with stented bioprostheses. Whilst the former expectation has not been fulfilled, partly due to concomitantly improved durability of second-generation stented bioprostheses, the latter has consistently been satisfied in early and late clinical observation. Evidence is accumulating suggesting improved long-term survival due to more timely and thorough regression of ventricular hypertrophy. In addition, stentless xenografts have shown extreme versatility when adopted in a variety of complex clinical conditions associated with aortic valve disease, including small aortic anulus, ascending aortic aneurysm, endocarditis and left ventricular dysfunction. Future research in the form of prospective, multicenter, randomized trials must address the issues of very long-term durability and survival, while simplification in valve design is required to promote wider use of stentless valves.

Atrail Fibrillation after Carfiac Surgery: Benign or Deserving of Prophylaxis

New onset atrial fibrillation (AF) is the commonest complication after cardiac surgery affecting around 30% of coronary artery bypass graft (CABG) patients, up to 50% of valve surgery patients and as many as 60% of those undergoing combined valve and CABG operations. After cardiac transplantation where the native pulmonary veins are electrically separated from the donor heart atria the incidence is only 11%.

Effect of the increase in valve area after aortic valve replacement with a 19-mm aortic valve prosthesis on left ventricular mass regression in patients with pure aortic stenosis

OBJECTIVES

Although patients with aortic stenosis, who receive 19-mm valves, are at high risk for prosthesis-patient mismatch, most of them show a significant left ventricular mass (LVM) regression postoperatively. The aim of this study was to identify factors predicting postoperative relative LVM regression in this subgroup of patients.

METHODS

A population of 44 patients operated on for pure aortic stenosis and receiving a 19-mm valve was studied by echocardiography at 1.4 +/- 0.5 years postoperatively.

RESULTS

The mean relative LVM regression was -19.3 +/- 18.9%, the mean gradient drop was -31.6 +/- 13.3 mmHg, and the mean Delta increase in aortic area index (postoperative aortic area index minus preoperative aortic area index) was 0.30 +/- 0.14 cm/m. Thirty-two patients had an indexed effective orifice area of less than 0.8 cm/m. At multivariate analysis (r = 0.63; r = 40%; P < 0.0001) preoperative LVM (P = 0.006), hypertension (P = 0.018) and Delta aortic area index (P = 0.049) were independent predictors of relative LVM regression.

CONCLUSIONS

Our study shows that, at least 1 year postoperatively, in patients receiving a 19-mm valve, LVM regression is influenced by several parameters, in particular preoperative LVM, hypertension and the magnitude of the increase in aortic area.

Modified stentless porcine valve enhances accelerated cuspal calcification in the juvenile sheep model

OBJECTIVE

Stent mounting of any bioprosthesis, induces a loss of mobility and reduces the effective valve orifice. By contrast, for stentless procedures, the higher surgical technicality remains a major obstacle for many surgeons. In an attempt to facilitate the insertion of the stentless porcine aortic valve (Toronto SPV), we tried to alter the design by lowering the invasive profile at the depth of the sinuses on both coronary sites. This could theoretically facilitate the implant of the modified stentless valve with an easygoing single layer suture at the challenging subcoronary level and make it more attractive for every surgeon.

METHODS

Modifications of the standard model were done by lowering the profile at the depth of the sinuses on both coronary sites, whether by plication or excision of the protruding porcine aortic wall at the nadir of each coronary sinus. Nine juvenile sheep underwent implantation of stentless porcine aortic valves in pulmonary position: 3 standard Toronto SPV, 3 plicated Toronto SPV and 3 excised Toronto SPV. In each series, valves were explanted after 3 months. Valves were analyzed.

RESULTS

The cusps of standard Toronto SPV were perfectly functioning and pliable, without visible calcification after three months. The calcium content of the cusps was less than those in the plicated and excised Toronto SPV (2.4 +/- 0.7 microg/mg versus 10.8 +/- 5.9 and 6.7 +/- 3.4 microg/mg). In the plicated and excised valves, calcification of the cusp was more pronounced in the commissural region (3.9 +/- 1.9, 29.0 +/- 16.7, 13.8 +/- 9.5 microg/mg in the standard, plicated and excised Toronto SPV, respectively). On the other hand, the aortic wall from the plicated Toronto SPV had more calcium than that from the other groups (53.6 +/- 6.3, 41.2 +/- 7.1, 45.2 +/- 7.4 microg/mg in the plicated, standard and excised Toronto SPV, respectively).

CONCLUSIONS

The modification of stentless porcine valve enhanced accelerated cuspal calcification in the commissural region. It accentuated that the correct implantation technique for stentless procedures is extremely important in order to prevent early degeneration.

Quantification of haemodynamic performance of stented and stentless aortic bioprostheses and potential influence on survival

BACKGROUND

The goal of aortic valve replacement is relief of symptoms, optimisation of haemodynamics, regression of left ventricular mass and advancement of survival. The objective of this review article is to provide the evidence-to-date on the clinical performance of stented and stentless heterograft bioprostheses with regard to haemodynamics, durability and survival.

METHODS

The haemodynamic advantage of aortic valve replacement prostheses is judged on ability to minimise postoperative gradients and to optimise the normalisation of left ventricular mass and function. The most frequent cause of high postoperative gradients occurs when the effective prosthetic valve area is less than that of the normal human valve. The effective orifice area index (EOAI) of >/= 0.85 cm(2)/m(2) is considered optimal to prevent patient-prosthesis mismatch (PPM) at rest and exercise.

RESULTS

The stented bioprostheses contribute to obstructive non-physiological flow patterns whereas stentless bioprostheses provide laminar non-obstructive flow. The stentless bioprostheses have been shown to have larger effective orifice areas and lower gradients. Mismatch is decreased with stentless bioprostheses especially when prosthesis size is </=21 mm. Left ventricular mass (LVM) postoperatively has been shown to relate to baseline LVM index (LVMI) and PPM. The EOAI >0.8 cm(2)/m(2) provides the best long-term regression of LVM. It has been identified that a tendency for PPM in sizes 21 and 23 mm stented bioprostheses did not prevent adequate achievement of appropriate LVMI. Survival at 5 years favoured stentless over stented bioprostheses for patients <70 years, but not in patients >/= _70 years of age. The durability comparison of the stentless bioprostheses must wait until 10-15 years experience is achieved. There is preliminary evidence that uneven shear stress on the leaflet of a regurgitant stentless bioprosthesis can accelerate leaflet tears at the level of the commissures. Dilation of the aortic root and, particularly, the sinotubular junction, can cause progressive stentless valve insufficiency.

CONCLUSIONS

The long-term performance advantages or disadvantages of stentless bioprostheses compared to stented bioprostheses will require at least another 5-7 years of cumulative stentless bioprostheses experience. Surgeons can use an algorithm intraoperatively to prevent patient-prosthesis mismatch while choosing the optimal prosthesis.

Time course of left ventricular remodeling after stentless aortic valve replacement

BACKGROUND

Stentless aortic valves are associated with a significant decrease in left ventricular hypertrophy. This study examined the time course and factors affecting left ventricular mass regression (LVMR) after aortic valve replacement (AVR) with Cryolife O'Brien (CLOB) (Cryolife International, Atlanta, Ga) stentless valves.

METHODS

Between 1993 and 2000, 130 consecutive patients underwent AVR with CLOB. Mean age was 71.3 +/- 6.3 years. Sixty-four (49.2%) were male. Mean body surface area (BSA) was 1.7 +/- 0.2 m(2). Mean valve size implanted was 23.6 +/- 2.0 mm. All patients were monitored with serial echocardiograms; the first study was performed preoperatively, and subsequent controls were at 6 months, 1, 2, 3, 4, 5, 6, and 7 years, respectively. Left ventricular mass was calculated by the Devereux formula and indexed by BSA.

RESULTS

Analysis of variance showed a significant reduction in the left ventricular mass index (LVMI) over time (P < .001). Most LVMRs occurred within the first 6 months, and after 1 year LVMI had decreased by 37.5% with further, but not statistically significant, reductions at later examinations. We found that baseline BSA > 1.75 m(2), male sex, arterial blood pressure > or = 150 mm Hg, left ventricular ejection fraction < or = 35%, New York Heart Association functional class > or = III, non-sinus rhythm, and prevalent aortic incompetence to be factors influencing LVMR. LVMR was not related to postoperative effective orifice area < or = 0.85 cm/m(2) and prosthetic size.

CONCLUSIONS

AVR with a CLOB valve is followed by a significant LVMR that occurs soon after surgery. It is influenced by several patient-related factors: most of them can be predicted preoperatively.

Stentless bioprostheses in aortic root disease

INTRODUCTION

The availability of aortic homografts is steadily decreasing. In the meantime, stentless xenografts convey similar flow characteristics, and tissue preservation methods are improving durability. Initially, these valves were contraindicated in aortic roots with discrepancy between annulus and sinotubular junction or with extensive calcification or sepsis. With increasing experience stentless xenografts are now applied in a wide spectrum of aortic root disease.

METHODS

I reviewed our own experience with stentless aortic bioprosthesis for aortic valve replacement (AVR) and more taxing root problems. I used these valves in aortic aneurysm repair, acute Type A dissection, and for endocarditis with abcess formation. I studied valve hemodynamics, regression of left ventricular hypertrophy, and comparative survival with stented bioprostheses.

RESULTS

Stentless bioprostheses convey hemodynamic and possibly survival benefit through a low incidence of valve-related complications. They provide a useful alternative to aortic homografts in endocarditis, Type A dissection, and aortic aneurysm surgery.

CONCLUSIONS

Stentless bioprostheses are no longer confined to AVR alone. Experience supports the use of stentless bioprostheses where aortic homografts were previously applied. With availability in a wide range of sizes.

Standard 19mm St Jude aortic valves in patients with body surface less than 1.7m2

Although new models of bileaflet valves with improved orifice have been devised, aortic valve replacement with 19mm prostheses still raises concerns about long term effects of residual transprosthetic gradient.

We reviewed our experience with 19 mm standard model St Jude prostheses in 68 patients operated on between January 1983 and December 1995. Clinical late assessment was performed to evaluate the incidence of valve related complications. Postoperative echocardiography was performed to evaluate hemodynamic performance of the prostheses.

Mean body surface area was 1.66±0.14m2. Late postoperative peak gradient was 53.85±7.16 mmHg; mean gradient was 34.80±5.55 mm Hg; effective orifice area was 1.93±0.05 cm2. Thirteen-year actuarial survival has been 90.89 ± 0.6%; thirteen-year freedom from embolism 89.41 ± 0.7% and freedom from hemorrhage 98.25 ± 0.02%. No case of prosthetic endocarditis, thrombosis, or reoperation was observed during follow-up.

Standard versus hemodynamic plus 19-mm St Jude Medical aortic valves

OBJECTIVE

We reviewed our experience with aortic valve replacement using 19-mm St Jude Medical prostheses (St Jude Medical, Inc, St Paul, Minn) in 119 patients, among which 68 (group A) had a Standard model and 51 (group B) had a Hemodynamic Plus model.

METHODS

Comparison between the 2 models included analysis of early and late mortality and all valve-related complications. Postoperative echocardiography was performed to evaluate the hemodynamic performance of both prosthetic models. Laboratory tests were performed to evaluate the amount of red blood cell damage caused by the transprosthetic turbulent flow.

RESULTS

Average body surface area was 1.66 +/- 0.14 m(2) in group A and 1.65 +/- 0.16 m(2) in group B (P =.72). There was no statistically significant difference between the 2 groups in terms of preoperative variables (sex, cardiac rhythm, body surface area, preoperative gradients, and New York Heart Association class). Five-year follow-up was 100% complete. Although group A patients had significantly higher postoperative peak and mean gradients (P =.0001) and a lower effective orifice area (P =.0001), no statistical differences were found in terms of late (5-year) survival (P =.6) and postoperative complications (P =.09). Moreover, postoperative left ventricular mass was found to be similar in the 2 groups (P =.18). Hematologic evaluation did not show any significant difference between the 2 groups as to incidence of hemolysis.

CONCLUSIONS

Aortic valve replacement with 19-mm aortic prostheses in patients with a body surface area of less than 1.7 m(2) allows good results. Although Hemodynamic Plus models have better hemodynamic results, no significant difference was found in terms of clinical results and clinical hemolysis.

The CryoLife O'Brien stentless porcine aortic bioprosthesis: 5-year follow-up

BACKGROUND

Mortality, morbidity, complication rates, and echo hemodynamic results using the Cryolife O'Brien stentless aortic bioprosthesis over a 5-year period are reported.

METHODS

The stentless valve was implanted in 97 conscecutive patients, 54 male and 43 female, mean age 70.9 +/- 6.5 years. All patients underwent preoperative, discharge (early study), 6-month (intermediate study), and late (18.3 +/- 10.4 months) echocardiography.

RESULTS

The actuarial 5-year survival rate was 93.9% +/- 3%. Aortic regurgitation was absent in 95.5%, mild in 3.4%, and moderate in 1.1%. Peak and mean systolic gradients were significantly lower at discharge (p < 0.001) and at the 6-month follow-up (p < 0.001) but did not significantly fall further at the late study (p = NS). The effective orifice area index at discharge (p < 0.001) and at 6 months (p < 0.001) differed significantly from preoperative values, but variations at late study were not significant (p = NS). Left ventricular mass index decreased early postoperatively (p < 0.001) and at 6-month assessment (p < 0.001) with a further significant reduction at late echocardiography (p = 0.04).

CONCLUSIONS

The 5-year results of this stentless valve showed a low rate of valve-related complications with excellent hemodynamic performance in all valve sizes.

Survival advantage of stentless aortic bioprostheses

BACKGROUND

Bioprostheses (BPs) are used to avoid anticoagulation after aortic valve replacement (AVR) in patients over 65 years of age. Stentless BPs offer established hemodynamic benefits. We sought to determine whether these advantages translate into improved survival.

METHODS

Between 1993 and 1997, follow-up data (for Food and Drug Administration submission) were collected prospectively for 160 consecutive, unselected hospital survivors who received the Freestyle valve (FS). Equivalent data were collected for 247 Carpentier-Edwards (CE) porcine xenograft patients. Detailed comparative statistical analysis was used to compare events and survival between the groups. Follow-up was 100% complete for the FS (5.2 years maximum; mean 3.2+/-1.0 years) group and 98% (7.2 years maximum; mean 3.8+/-2.0 years) for CE.

RESULTS

The groups were well matched in age (FS, 73+/-6 years; CE, 74+/-6 years), gender (FS, 58% male; CE, 62% male), ventricular function, and number of patients requiring coronary grafts (FS, 41%; CE, 37%). Actuarial survival at 5 years was 84% for FS versus 69% for CE (p = 0.023 Kaplan Meier, p = 0.009 Cox). Annual mortality rates were 3.6% for FS versus 7.1% for CE (p = 0.001). Thromboembolic rate was 0.8% per year for FS and 2.4% for CE (p = 0.024) without a difference in cardiac rhythm. Incidence of nonstructural dysfunction (paravalvular leak) was 0.2% for FS versus 1.3% for CE (p = 0.020).

CONCLUSIONS

By 5 years, the stentless valve patients had improved survival and reduced adverse events. Though differences in durability are yet to be proved, our findings support the use of stentless bioprostheses in this age group.