Rigorous patient-prosthesis matching of Perimount Magna aortic bioprosthesis

Abstract

Background

Severe patient-prosthesis mismatch, defined as effective orifice area index ≤0.65 cm² m⁻², has demonstrated poor long-term survival after aortic valve replacement. Reported rates of severe mismatch involving the Perimount Magna aortic bioprosthesis range from 4% to 20% in patients with a small annulus.

Methods

Between June 2008 and August 2011, 251 patients (mean age 70.5 ± 10.2 years; mean body surface area 1.55 ± 0.19 m²) underwent aortic valve replacement with a Perimount Magna bioprosthesis, with or without concomitant procedures. We performed our procedure with rigorous patient-prosthesis matching to implant a valve appropriately sized to each patient, and carried out annular enlargement when a 19-mm valve did not fit. The bioprosthetic performance was evaluated by transthoracic echocardiography predischarge and at 1 and 2 years after surgery.

Results

Overall hospital mortality was 1.6%. Only 5 (2.0%) patients required annular enlargement. The mean follow-up period was 19.1 ± 10.7 months with a 98.4% completion rate. Predischarge data showed a mean effective orifice area index of 1.21 ± 0.20 cm² m⁻². Moderate mismatch, defined as effective orifice area index ≤0.85 cm² m⁻², developed in 4 (1.6%) patients. None developed severe mismatch. Data at 1 and 2 years showed only two cases of moderate mismatch; neither was severe.

Conclusions

Rigorous patient-prosthesis matching maximized the performance of the Perimount Magna, and no severe mismatch resulted in this Japanese population of aortic valve replacement patients.

Keywords

Aortic valve stenosis bioprosthesis echocardiography heart valve prosthesis implantation mortality treatment outcome

Introduction

In many studies, severe patient-prosthesis mismatch (PPM) has demonstrated poor long-term survival after aortic valve replacement in a variety of patient groups.^1–3 The Carpentier-Edwards Perimount Magna (CEPM) aortic bioprosthesis (Edwards Lifesciences, Irvine, CA, USA) was introduced in 2002 as a modification of the Carpentier-Edwards Perimount standard (CEPS). The CEPM has an improved cuff design that allows implantation into a smaller aortic annulus. Dalmau and colleagues⁴ reported lower mean and peak pressure gradients (PG), larger effective orifice areas (EOA), and lower rates of PPM with CEPM compared to CEPS. However, the reported rate of severe PPM using CEPM still ranged from 4% to 20% in patients with small annular diameters.^5–8 To maximize CEPM performance and reduce the incidence of severe PPM, we performed aortic valve replacement surgery under rigorous patient-prosthesis matching with 3 policies. First, we chose a CEPM size based on careful measurement of annular size with a CEPM sizer. We consider the bioprosthesis size to be a size smaller than the sizer that passes through the annulus into the left ventricle, and always try to implant the exact size of bioprosthesis based on a sizer that precisely fits the annulus and does not enter the left ventricle. Complete annular decalcification is mandatory to perform this procedure. Second, we carry out annular enlargement when a 19-mm valve does not fit or when the EOA index (EOAI) is less than 0.85 cm² m⁻², based on the EOA data provided by Dalmau and colleagues,⁴ but we did not have any such cases in this series. Third, we use a simple interrupted suturing technique instead of pledgeted everting or non-everting mattress sutures because the former has recently been reported to improve the performance of CEPM.⁸ In addition, intraoperative transesophageal echocardiography (TEE) is used to measure the annulus. During TEE image acquisition, every effort is made to ensure that the largest annulus diameter is obtained. The objective of this study was to analyze the impact of our aortic valve replacement procedure, with rigorous patient-prosthesis matching, on the hemodynamic performance of the CEPM in the Japanese population.

Patients and methods

Between June 2008 and August 2011, 251 patients (mean age 70.5 ± 10.2 years, range 23–88 years; mean body surface area 1.55 ± 0.19 cm² m⁻²) underwent aortic valve replacement using the CEPM prosthesis at our hospital. We decided the size of the bioprosthesis to implant based on rigorous measurements obtained with sizers provided by the manufacturer. After complete annular decalcification, we determined which sizer precisely fitted the annulus and did not enter the left ventricle. Intraoperative TEE assisted our measurement, and a simple interrupted suturing technique was used to implant the bioprosthesis. We performed annular enlargement when a 19-mm valve did not fit. Eleven (4%) patients had undergone previous cardiac surgery. Patient demographics and indications for aortic valve replacement are summarized in Table 1. Intraoperative TEE was performed by an experienced echocardiographer to measure the aortic annulus. A Philips iE33 system (Philips, Andover, MA, USA) was used with a TEE (X7-2t) transducer that allowed 2-dimensional TEE images. An image plane between 120° and 150° was used to image the annulus in the midesophageal position. During 2-dimensional TEE image acquisition, every effort was made to ensure that the largest annulus diameter was obtained using zoom mode. All measurements of the annulus were taken during systole and recorded as an average from 3 beats. The annulus was recorded as the inner edge-to-inner edge distance measured from the junction of the aortic right coronary cusps with the septal endocardium to the junction of the noncoronary cusps with the mitral valve posteriorly. Annular calcification was included.^9,10

Table 1.

Characteristics of 251 patients undergoing aortic valve replacement.

Variable	No. of patients
Male/female	135/116
Age (years)	70.5 ± 10.2
Height (cm)	156.6 ± 9.4
Weight (kg)	56.7 ± 11.2
Body surface area (m²)	1.55 ± 0.19
Hypertension	186
Diabetes mellitus	48
Hyperlipidemia	89
Hemodialysis	32
Cerebral infarction	26
Chronic obstructive pulmonary disease	10
History of congestive heart failure	61
Emergency	4
Reoperation	11
Infective endocarditis (active/healed)	5/2
NYHA class
Class I	33
Class II	178
Class III	31
Class IV	9
Indication for surgery
Aortic stenosis	114
Aortic regurgitation	73
Aortic stenosis and regurgitation	60
Infective endocarditis*	3

Without aortic stenosis or regurgitation. NYHA: New York Heart Association.

TTE was performed predischarge and at one and two years after surgery. The modified Bernoulli equation was used to calculate the maximum and mean PG across the valve. We calculated the EOA according to the continuity equation: EOA (cm²) = (LVOT diameter × 0.5)²× π × (VTI_LVOT/VTI_valve), where LVOT and VTI are the left ventricular outflow tract and velocity time integral, respectively.⁹ The EOAI was calculated by dividing the EOA by the body surface area. The left ventricular mass (LVM) was measured preoperatively and one year after surgery by TTE and calculated as: LVM = 0.8 × (1.04 × [(LVIDd + PWTd + SWTd)³− (LVIDs)³]) + 0.6 g, where the LVIDd and LVIDs are the diastolic and systolic left ventricular internal diameters, respectively, and PWTd and SWTd are the diastolic posterior and septal wall thicknesses, respectively.¹¹ The LVM index (LVMI) was calculated by dividing the LVM by the body surface area. Based on the definition by Blais and colleagues,¹² we defined PPM as severe or moderate when the prosthetic aortic valve EOAI was ≤0.65 cm² m⁻² or >0.65 and ≤0.85 cm² m⁻², respectively. The mean follow-up period was 19.1 ± 10.7 months (range 0.4–42.2 months), and the follow-up completion rate was 98.4%.

Continuous variables are expressed as mean ± standard deviation and categorical variables as frequencies (%). The t test for continuous variables was used to assess patients’ preoperative and operative data, and the chi-square or Fisher’s exact tests was used to assess categorical variables. Pearson’s correlation test was used to analyze the relationship between the annulus size measured by TEE and the implanted bioprosthesis size. The SPSS program (Dr. SPSS II; SPSS Inc., Chicago, IL, USA) was used to analyze all data. A p value <0.05 was considered to indicate statistical significance.

Results

As shown in Table 2, 156 (62%) patients underwent concomitant procedures. Only 5 (2.0%) patients required annular enlargement to implant a 19-mm CEPM (mean body surface area 1.34 ± 0.13 cm² m⁻²). Hospital mortality was 1.6% (4/251 patients). Causes of death were multiple organ failure (n = 2), congestive heart failure (n = 1), and sepsis (n = 1). Twenty-five (10%) patients developed complications. Major complications included reexploration due to bleeding and/or tamponade (n = 5), cerebral infarction (n = 1), mediastinitis (n = 3), and respiratory failure requiring tracheostomy (n = 4). Intraoperative TEE was used to measure aortic annulus size in all cases except those with previous aortic valve replacement (n = 5). Among the 246 patients whose annulus was measured, 227 (92%) had a bioprosthesis ≤2 mm of the TEE measured value. Sixteen (6.5%) patients received a bioprosthesis >1 size smaller than the size measured by TEE. Reasons for under-sizing were diseased aorta (n = 6), bicuspid aortic valve with an inaccurate TEE measurement (n = 3), concomitant mitral procedure with rheumatic pathology (n = 2), and unknown (n = 4). Pearson’s coefficient for the correlation between the TEE size and actual implanted CEPM size was 0.80, which shows a strong positive relationship (p < 0.01). Fourteen (5.7%) patients died during the follow-up period. Causes of death were congestive heart failure (n = 1), sepsis (n = 1), myocardial infarction (n = 1), pneumonia (n = 1), thrombocytopenia (n = 1), cancer (n = 1), subarachnoid hemorrhage (n = 1), cerebral infarction (n = 1), respiratory failure (n = 1), acute renal failure (n = 1), and unknown (n = 3). Major complications included cerebral infarction (n = 2), wound dehiscence (n = 3), infective endocarditis (n = 2), and heart failure due to tricuspid regurgitation (n = 1). Predischarge TTE (Table 3) revealed that the mean and peak PG were 11.5 ± 4.4 and 22.1 ± 8.6 mm Hg, respectively. The mean EOA was 1.87 ± 0.33 cm², and the mean EOAI was 1.21 ± 0.20 cm² m⁻². None of the patients developed severe PPM, and moderate PPM occurred in 4 (1.6%): 19-mm valve in 3/44 (6.8%); 21-mm in 1/77 (1.3%). An EOAI of more than 0.85 cm² m⁻² was expected in these 4 patients preoperatively; however, the EOA remained lower than expected (1.31 ± 0.01 cm²), which caused moderate PPM. The mean EOAI was maintained >1.0 cm² m⁻² in all valve groups regardless of valve size (Table 3). At the one-year follow-up, the mean and peak PG values significantly decreased relative to the predischarge values. None of the patients developed severe PPM, but moderate PPM developed in 2/171 patients (1.2%): 1/32 (3.1%) with 19-mm valves and 1/48 (2.1%) with 21-mm valves. The mean EOAI at 1 year was maintained >1.0 cm² m⁻² in all valve groups regardless of size. These trends were still present at two years. None of the patients developed severe PPM, but moderate PPM developed in 2/94 (2.1%): 2/22 (9.1%) with 21-mm valves. The overall LVM and LVMI values at one year were significantly decreased relative to the preoperative values (Table 4). The LVM and LVMI values decreased with 27-mm valves, but the differences were not significant. All patients remained in New York Heart Association class I or II; 147 (89%) remained in class I.

Table 2.

Surgical details of 251 patients undergoing aortic valve replacement.

Variable	No. of patients
Surgical duration (min)	379 ± 106
Cardiopulmonary bypass time (min)	201 ± 65
Aortic crossclamp time (min)	159 ± 54
Valve size
19 mm	46
21 mm	79
23 mm	76
25 mm	33
27 mm	17
Cannulation site
Ascending aorta	209
Axillary artery	41
Femoral artery	1
Concomitant procedures	156
Aortic annular enlargement	5
Morrow	1
Coronary artery bypass grafting	73
No. of anastomosis	2.0 ± 1.3
Left main trunk plasty	1
Mitral valve plasty	55
Mitral valve replacement	4
Tricuspid annuloplasty	35
Maze procedure	39
Ascending aorta replacement	31
Total arch replacement	5
Atrial septal defect closure	6
Patent ductus arteriosus ligation	2

Table 3.

Follow-up transthoracic echocardiography data.

Valve size	n	Time	BSA (m²)	Ejection fraction	Mean PG (mm Hg)	Max PG (mm Hg)	EOA (cm²)	EOAI (cm² m⁻²)	EOAI ≤ 0.85 cm² m⁻²
19 mm	44	Discharge	1.39 ± 0.13	61.1% ± 9.7%	14.3 ± 5.8	26.9 ± 10.2	1.49 ± 0.16	1.09 ± 0.18	3
	32	1 year		65.2% ± 3.1%	13.3 ± 5.0	25.2 ± 9.6	1.46 ± 0.09	1.06 ± 0.11	1
	23	2 years		65.7% ± 4.1%	12.5 ± 3.6	23.7 ± 6.8	1.49 ± 0.11	1.07 ± 0.09	0
21 mm	77	Discharge	1.51 ± 0.17	58.5% ± 9.1%	12.3 ± 3.8	24.0 ± 8.9	1.76 ± 0.18	1.18 ± 0.17	1
	48	1 year		62.2% ± 7.5%	9.9 ± 3.2	19.1 ± 5.8	1.77 ± 0.22	1.17 ± 0.19	1
	22	2 years		64.1% ± 6.4%	10.4 ± 3.9	19.3 ± 7.4	1.75 ± 0.25	1.11 ± 0.16	2
23 mm	74	Discharge	1.59 ± 0.15	56.0% ± 11.2%	10.4 ± 3.7	19.9 ± 6.9	1.94 ± 0.19	1.23 ± 0.17	0
	55	1 year		62.3% ± 6.6%	9.2 ± 3.7	18.0 ± 7.0	1.94 ± 0.21	1.21 ± 0.14	0
	30	2 years		62.9% ± 7.7%	8.3 ± 2.4	16.3 ± 4.1	1.98 ± 0.20	1.25 ± 0.15	0
25 mm	33	Discharge	1.67 ± 0.16	51.8% ± 11.1%	9.5 ± 3.2	18.3 ± 5.7	2.20 ± 0.23	1.33 ± 0.21	0
	23	1 year		53.3% ± 11.3%	8.1 ± 2.4	15.4 ± 4.2	2.16 ± 0.19	1.33 ± 0.16	0
	11	2 years		53.5% ± 13.1%	6.5 ± 1.4	12.3 ± 2.5	2.15 ± 0.19	1.30 ± 0.13	0
27 mm	17	Discharge	1.77 ± 1.13	48.4% ± 14.5%	8.9 ± 3.0	17.6 ± 5.8	2.51 ± 0.32	1.41 ± 0.17	0
	13	1 year		57.0% ± 14.2%	6.9 ± 2.1	13.6 ± 3.9	2.47 ± 0.31	1.39 ± 0.17	0
	8	2 years		54.3% ± 15.2%	6.1 ± 1.9	11.8 ± 3.7	2.36 ± 0.33	1.35 ± 0.18	0
Total	245	Discharge	1.55 ± 0.19	56.6% ± 11.1%	11.5 ± 4.4	22.1 ± 8.6	1.87 ± 0.33	1.21 ± 0.20	4
	171	1 year		61.2% ± 8.7%	9.9 ± 4.0	19.0 ± 7.5	1.87 ± 0.33	1.20 ± 0.18	2
	94	2 years		62.0% ± 9.3%	9.4 ± 3.7	18.0 ± 6.9	1.86 ± 0.34	1.19 ± 0.17	2

BSA: body surface area; EOA: effective orifice area; EOAI: effective orifice area index; PG: pressure gradient.

Table 4.

Changes in left ventricular mass, left ventricular mass index, and New York Heart Association class.

Valve size	No. of patients	Time	LVM (g)	LVMI (g m⁻²)	NYHA class I	NYHA class II
19 mm	32	Preop	127 ± 37	92 ± 30
		1 year	97 ± 24*	71 ± 23*	28	4
21 mm	45	Preop	139 ± 40	94 ± 35
		1 year	105 ± 29*	70 ± 21*	37	8
23 mm	53	Preop	147 ± 44	93 ± 31
		1 year	107 ± 28*	67 ± 18*	49	4
25 mm	23	Preop	153 ± 42	94 ± 24
		1 year	107 ± 31*	67 ± 19*	22	1
27 mm	12	Preop	172 ± 42	97 ± 26
		1 year	110 ± 34^†	62 ± 18^†	11	1
Total	165	Preop	143 ± 42	94 ± 30
		1 year	105 ± 29*	68 ± 20*	147	18

p < 0.01. ^†p > 0.05. LVM: left ventricular mass; LVMI: left ventricular mass index; NYHA: New York Heart Association; Preop: preoperative.

Discussion

Although it is still controversial, many reports have shown that the presence of severe PPM leads to significantly worse long-term survival in a variety of patient groups.^1–3 The EOAI at rest is ideally >0.85–0.90 cm² m⁻² to maintain optimal valve performance during exercise.¹³ Another study found that EOAI ≤0.80 cm² m⁻² increased the risk of heart failure after valve replacement by approximately 60%, but long-term survival was not significantly affected.¹⁴ These findings suggest that a larger EOAI is one of the most important factors affecting a patient’s prognosis after aortic valve replacement. On the basis of these findings, we performed aortic valve replacement with a focus on careful patient-prosthesis matching. Our standard practice is to carefully implant exact-size prostheses based on the measured annular size. In addition, intraoperative TEE helped our decision-making. We initially trained our echocardiographers to measure the exact annular size. After they had performed measurements for a month, the values very closely matched the actual annular size, as shown by the correlation coefficient of 0.8. We then strived to implant the exact size of CEPM using a simple interrupted suture technique.⁸ By combining these techniques, we achieved no severe PPM in our 251 patients.

The most striking feature of the CEPM valve is the narrow suture ring that maintains a large EOA. Dalmau and colleagues⁴ described significantly larger EOA with 19-, 21- and 23-mm CEPM valves than with CEPS valves. Botzenhardt and colleagues¹⁵ also reported that the CEPM valve resulted in a low mean PG and large EOA and EOAI compared to the CEPS valves with a 22–23-mm aortic annulus, whereas severe PPM was significantly less prevalent than that observed with CEPS valves with annulus diameters <22 mm. However, the reported rates of severe PPM using CEPM still range from 4% to 20% in patients with small annular diameters.^5–8 We have been performing aortic valve replacement surgery by adding aortic annular enlargement (Nicks procedure) when a 19-mm valve did not fit. Although we add annular enlargement when the EOAI is less than 0.85 cm² m⁻², we did not have such cases in this series. The use of the Nicks procedure decreased after the induction of CEPM, and only 5 (2.0%) patients required annular enlargement to implant a 19-mm CEPM among our 251 patients. Again, by applying a careful patient-prosthesis matching policy, we achieved no severe PPM. We observed a postoperative EOAI > 1.0 cm² m⁻² for all sizes. Moreover, EOAI values were higher than those obtained using CEPM as described in previous reports.^5–8

The LVMI as a measure of left ventricular hypertrophy has become a popular endpoint for assessing aortic valve replacement at follow-up.^16–18 Incomplete regression of left ventricular hypertrophy after aortic valve replacement has been associated with increased mortality rates.¹⁹ Fuster and colleagues²⁰ demonstrated that significantly higher hospital mortality in patients with high LVMI was promoted by coexisting PPM and a low left ventricular ejection fraction. The present study showed that our aortic valve replacement surgery produced a significant decrease in LVMI at the one-year follow-up, with New York Heart Association class improvement. Improved prognosis as well as quality of life is expected, and we continue to monitor our patients.

This study has several limitations. First, it is a retrospective short-term investigation with postoperative follow-up for only two years. Careful long-term follow-up is warranted. Second, we did not compare CEPM with other bioprostheses, and other valves should be used to further evaluate the careful patient-prosthesis matching. We concluded that a careful patient-prosthesis matching approach for aortic valve replacement surgery, using rigorous annular size measurement and a simple interrupted suturing technique to maximize the performance of CEPM, achieved no severe patient-prosthesis mismatch in 251 Japanese patients.

Footnotes

Acknowledgment

The authors would like to thank Enago () for the English language review.

Presented at the 20th Annual Meeting of The Asian Society for Cardiovascular and Thoracic Surgery, Bali, Indonesia, March 8–11, 2012.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Conflicts of interest statement

None declared.

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