A prosthesis–patient mismatch (PPM) is present when the prosthetic valve is too small in relation to the patient’s body size. The purpose of the present study was to investigate the frequency of PPM after the implantation of the Medtronic CoreValve System, and its relation to the clinical outcome. The indexed effective orifice area (EOA) was measured in 74 patients with symptomatic severe aortic stenosis, who had undergone successful transcatheter aortic valve implantation with the Medtronic CoreValve System, at baseline and discharge. PPM was defined as severe (indexed EOA <0.65 cm 2 /m 2 ) or moderate (indexed EOA 0.65 to 0.85 cm 2 /m 2 ). The indexed EOA increased from 0.35 ± 0.13 to 0.97 ± 0.34 cm 2 /m 2 after transcatheter aortic valve implantation (p <0.001) and was accompanied by significant clinical improvement. Severe and moderate PPMs were found in 16% and 23% of patients, respectively. Patients with severe PPM were more symptomatic and had a smaller indexed EOA at baseline than those with moderate or no PPM (0.28 ± 0.09 vs 0.36 ± 0.12 cm 2 /m 2 , p <0.05). Functional status and mortality at 30 days and 6 months was not significantly different between the patients with severe PPM and those with moderate or no PPM. In conclusion, the indexed EOA increased significantly after transcatheter aortic valve implantation. Severe PPM was observed in 16% of the patients and was not associated with the clinical outcome.
Prosthesis–patient mismatch (PPM) is present when the prosthetic valve is too small in relation to the patient’s body size. PPM is associated with a greater than expected transprosthetic gradient and increased left ventricular afterload, which, in turn, can adversely affect the immediate and long-term clinical outcome. PPM is considered severe when the indexed effective orifice area (EOA) is <0.65 cm 2 /m 2 and moderate when the indexed EOA is 0.65 to 0.85 cm 2 /m 2 . After surgical aortic valve replacement, PPM has been reported to range from 20% to 70% and to be severe in 2% to 28% of patients. Notwithstanding the conflicting reports of the effect of PPM on outcome, the general concept has been that PPM should be avoided by the careful selection of the prosthesis type and size and possibly by the use of additional surgical techniques, such as aortic root enlargement, to accommodate a larger prosthesis. Recently, in a study investigating the incidence and predictors of PPM after Medtronic CoreValve System (Medtronic, Minneapolis, Minnesota) implantation in 50 patients, Jilaihawi et al reported that severe PPM was present at discharge in 2% of patients. In a series of 50 patients who had received the Edwards SAPIEN bioprosthetic valve (Edwards Lifesiences, Irvine, California), Clavel et al reported that severe PPM was present in 11% of patients at discharge. The effect of PPM after transcatheter aortic valve implantation (TAVI) on the clinical outcome is unknown. We investigated the frequency of PPM after the implantation of the Medtronic CoreValve System and its relation to 30-day and 6-month mortality and functional status.
Methods
The study population included a series of 74 of 96 consecutive patients with symptomatic severe aortic stenosis who had undergone successful TAVI with the Medtronic CoreValve System and were discharged alive and in whom the image quality of transthoracic echocardiography allowed accurate measurements of the EOA at baseline and discharge. The inclusion and exclusion criteria for Medtronic CoreValve implantation have been previously described in detail. In brief, the patients were eligible for TAVI in the case of severe valvular aortic stenosis (EOA <1 cm 2 or <0.6 cm 2 /m 2 ) and considered at high or prohibitive operative risk.
The Medtronic CoreValve System consists of a trileaflet porcine pericardial tissue valve, mounted in a self-expanding nitinol frame. The selection of the size of the prosthesis was determined by the assessment of the aortic annulus using transthoracic echocardiography and/or multislice computed tomography before the procedure. With increasing operator experience, the latter technique became the single most important method for selecting the valve size.
Transthoracic echocardiography was performed at baseline and before discharge using a Philips iE33 or a Sonos 7500 system (Philips, Best, The Netherlands). Complete echocardiographic studies were performed in a standard fashion and analyzed by an experienced echocardiographer. During the studies, patients had a normal at rest heart rate (60 to 90 beats/min) and blood pressure within normal limits. The left ventricular (LV) ejection fraction was calculated using the Teichholz method. Low-gradient aortic stenosis was defined by a mean transaortic gradient of <40 mm Hg and a LV ejection fraction of <35%. The EOA was estimated using the continuity equation approach (EOA = LV outflow tract [LVOT] area × velocity time integral LVOT /velocity time integral valve ). According to the published guidelines, the LVOT area was measured just underneath the prosthesis, assuming a circular geometry. In addition, the pulse wave Doppler sample volume was located in the LVOT, adjacent to the in-flow segment of the prosthesis but not inside it, avoiding the region of subvalvular acceleration. The indexed EOA was calculated by dividing the EOA by the patient’s body surface area. The PPM was defined as follows: no PPM if the indexed EOA was >0.85 cm 2 /m 2 , moderate PPM if the indexed EOA was 0.65 to 0.85 cm 2 /m 2 , and severe PPM when the indexed EOA was <0.65 cm 2 /m 2 .
For the purposes of the present study, functional status (New York Heart Association) and mortality data were collected at baseline and 30 days and 6 months and were complete for all patients. Early and short-term mortality was defined by all-cause mortality at 30 days and 6 months after TAVI, respectively (for patients who were discharged alive).
Continuous variables are presented as the mean ± SD. The mean values of the continuous variables were compared using the t test. Categorical variables are presented as frequencies and percentages and were compared using the chi-square test or Fisher’s exact test. The significance of the differences among the 3 groups (severe PPM, moderate PPM, no PPM) was tested using 1-way analysis of variance, followed by the Bonferroni method for post hoc comparisons of the mean values. Univariate analysis was performed to delineate the differences between the patients with severe PPM and those without or with moderate PPM. Statistical significance was assumed at p <0.05. All statistical analyses were performed using the Statistical Package for Social Sciences, version 15.0, software (SPSS, Chicago, Illinois).
Results
The baseline characteristics are summarized in Table 1 . The study population consisted of 74 elderly patients with significant co-morbidities. Of the 96 patients who had undergone successful TAVI with the Medtronic CoreValve System during the study period, 22 were excluded from the analysis but had baseline characteristics similar to those of the study population. The reasons for exclusion were procedural death (3 patients), in-hospital death (6 patients), and suboptimal image quality on transthoracic echocardiography (13 patients). None of the deaths was related to the prosthesis. For patients discharged alive, the median length of stay was 10 days (interquartile range 7 to 18 days).
| Variable | Study Population (n = 74) | Excluded Patients (n = 22) | p Value |
|---|---|---|---|
| Age (years) | 81 ± 7 | 82 ± 4 | 0.51 |
| Men | 35 (47%) | 8 (36%) | 0.37 |
| Weight (kg) | 71 ± 12 | 74 ± 15 | 0.30 |
| Height (cm) | 166 ± 8 | 167 ± 9 | 0.91 |
| Body mass index (kg/m 2 ) | 26 ± 4 | 27 ± 4 | 0.36 |
| Body surface area (m 2 ) | 1.81 ± 0.18 | 1.85 ± 0.23 | 0.37 |
| Antecedents | |||
| Cerebrovascular events | 18 (24%) | 5 (23%) | 1.00 |
| Acute myocardial infarction | 15 (20%) | 6 (27%) | 0.56 |
| Percutaneous coronary intervention | 18 (24%) | 3 (14%) | 0.39 |
| Coronary artery bypass | 21 (28%) | 6 (27%) | 0.91 |
| Co-morbidities | |||
| Chronic obstructive pulmonary disease | 22 (30%) | 2 (9%) | 0.06 |
| Chronic renal disease | 11 (15%) | 4 (18%) | 0.74 |
| Peripheral vascular disease | 4 (5%) | 1 (5%) | 1.00 |
| Atrial fibrillation | 17 (23%) | 9 (41%) | 0.10 |
| Diabetes mellitus | 12 (16%) | 6 (27%) | 0.35 |
| New York Heart Association class | |||
| I–II | 15 (20%) | 2 (9%) | 0.34 |
| III–IV | 59 (80%) | 20 (91%) | |
| Logistic EuroSCORE | 15 ± 8 | 19 ± 10 | 0.08 |
| Medtronic CoreValve sizes available (mm) | |||
| 26 | 20 (27%) | 4 (18%) | 0.52 |
| 26 or 29 | 54 (73%) | 18 (82%) |
Of the 74 patients, 59 (80%) had New York Heart Association class III to IV at baseline. Twenty patients (27%) were treated during a period when only the 26-mm inflow Medtronic CoreValve System was available. TAVI was associated with a significant improvement in EOA (from 0.62 ± 0.20 to 1.74 ± 0.59 cm 2 , p <0.001), indexed EOA (from 0.35 ± 0.13 to 0.97 ± 0.34 cm 2 /m 2 , p <0.001), and mean transaortic gradient (from 47 ± 16 to 9 ± 5 mm Hg, p <0.001). Moreover, TAVI was accompanied by significant clinical improvement. The percentage of patients with New York Heart Association class I to II increased from 20% at baseline to 66% at discharge. Severe and moderate PPM, however, was identified in 16% and 23% of patients, respectively ( Table 2 ).
| Variable | Total | PPM | |||
|---|---|---|---|---|---|
| Severe | Moderate | Absent | p Value | ||
| Patients | 74 (100%) | 12 (16%) | 17 (23%) | 45 (61%) | |
| Effective orifice area (cm 2 ) | 1.74 ± 0.59 | 1.02 ± 0.17 | 1.34 ± 0.14 | 2.08 ± 0.49 | <0.001 ⁎ |
| Effective orifice area indexed (cm 2 /m 2 ) | 0.97 ± 0.34 | 0.56 ± 0.08 | 0.74 ± 0.06 | 1.17 ± 0.04 | <0.001 ⁎ |
| Mean gradient (mm Hg) | 9 ± 5 | 14 ± 6 | 10 ± 4 | 8 ± 4 | <0.001 † |
⁎ Between group without PPM and groups with severe or moderate PPM.
Univariate analysis was performed to delineate the differences between patients with severe PPM and those without or with moderate PPM ( Tables 3 and 4 ). Patients with severe PPM had a greater prevalence of a history of myocardial infarction. All patients with severe PPM had New York Heart Association class III to IV at baseline. Furthermore, patients with severe PPM had a greater severity of aortic stenosis at baseline (indexed EOA 0.28 ± 0.09 vs 0.36 ± 0.12 cm 2 /m 2 , p <0.05). No difference was seen in LV function or aortic annulus size. Patients with severe PPM were more likely to have received a 26-mm inflow CoreValve (75% vs 25%, p = 0.06). Clinical improvement was found in most patients after TAVI that was maintained at 6 months. We found no difference in functional status or mortality between patients with severe PPM and those without or with moderate PPM ( Table 4 ). An inverse exponential relation was found between the indexed EOA and the mean transprosthetic gradient at discharge (r = 0.38; Figure 1 ).
| Variable | Severe PPM | ||
|---|---|---|---|
| Yes (n = 12) | No (n = 62) | p Value | |
| Age (years) | 82 ± 6 | 81 ± 7 | 0.73 |
| Men | 7 (58%) | 28 (45%) | 0.40 |
| Weight (kg) | 72 ± 12 | 71 ± 12 | 0.69 |
| Height (cm) | 168 ± 6 | 166 ± 9 | 0.45 |
| Body mass index (kg/m 2 ) | 26 ± 4 | 26 ± 4 | 0.94 |
| Body surface area (m 2 ) | 1.83 ± 0.17 | 1.80 ± 0.18 | 0.59 |
| Antecedents | |||
| Cerebrovascular events | 3 (25%) | 15 (24%) | 0.60 |
| Acute myocardial infarction | 7 (58%) | 8 (13%) | <0.001 |
| Percutaneous coronary intervention | 4 (33%) | 14 (23%) | 0.32 |
| Coronary artery bypass | 3 (25%) | 18 (29%) | 0.54 |
| Co-morbidities | |||
| Chronic obstructive pulmonary disease | 4 (33%) | 18 (29%) | 0.51 |
| Chronic renal disease | 2 (18%) | 9 (15%) | 0.57 |
| Peripheral vascular disease | 0 (0%) | 4 (6%) | 0.48 |
| Atrial fibrillation | 2 (18%) | 15 (24%) | 0.44 |
| Diabetes mellitus | 2 (18%) | 10 (16%) | 0.62 |
| New York Heart Association class | |||
| I–II | 0 (0%) | 15 (24%) | 0.05 |
| III–IV | 12 (100%) | 47 (76%) | |
| Logistic EuroSCORE | 15 ± 7 | 15 ± 9 | 0.83 |
| Medtronic CoreValve sizes available (mm) | |||
| 26 | 5 (42%) | 15 (24%) | 0.18 |
| 26 or 29 | 7 (58%) | 47 (76%) | |
| Variable | Total (n = 74) | Severe PPM | ||
|---|---|---|---|---|
| Yes (n = 12) | No (n = 62) | p Value | ||
| Baseline | ||||
| Ejection fraction (%) | 52 ± 16 | 49 ± 18 | 53 ± 16 | 0.50 |
| Ejection fraction <35% | 9 (12%) | 3 (25%) | 6 (10%) | 0.16 |
| Low-gradient aortic stenosis ⁎ | 3 (4%) | 1 (8%) | 2 (3%) | 0.07 |
| Aortic annulus diameter (mm) | 22 ± 2 | 22 ± 2 | 23 ± 2 | 0.13 |
| Peak gradient (mm Hg) | 81 ± 26 | 92 ± 31 | 78 ± 25 | 0.10 |
| Mean gradient (mm Hg) | 47 ± 16 | 56 ± 17 | 46 ± 15 | 0.05 |
| Peak velocity (cm/s) | 438 ± 72 | 469 ± 844 | 433 ± 69 | 0.11 |
| Effective orifice area (cm 2 ) | 0.62 ± 0.20 | 0.52 ± 0.16 | 0.64 ± 0.20 | <0.05 |
| Effective orifice area indexed (cm 2 /m 2 ) | 0.35 ± 0.12 | 0.28 ± 0.09 | 0.36 ± 0.12 | <0.05 |
| Discharge | ||||
| Peak gradient (mm Hg) | 18 ± 9 | 26 ± 10 | 17 ± 8 | <0.001 |
| Mean gradient (mm Hg) | 9 ± 5 | 14 ± 6 | 8 ± 4 | <0.001 |
| Peak velocity (cm/s) | 206 ± 53 | 252 ± 52 | 197 ± 48 | <0.001 |
| Effective orifice area (cm 2 ) | 1.74 ± 0.59 | 1.02 ± 0.17 | 1.88 ± 0.54 | <0.001 |
| Effective orifice area indexed (cm 2 /m 2 ) | 0.97 ± 0.34 | 0.56 ± 0.08 | 1.05 ± 0.31 | <0.001 |
| Aortic regurgitation grade | 0.44 | |||
| None to mild | 57 (77%) | 10 (83%) | 47 (76%) | |
| Moderate to severe | 17 (23%) | 2 (17%) | 15 (24%) | |
| Medtronic CoreValve size (mm) | 0.06 | |||
| 26 | 37 (50%) | 9 (75%) | 28 (45%) | |
| 29 | 37 (50%) | 3 (25%) | 34 (55%) | |
| Outcome | ||||
| At 30 days | ||||
| New York Heart Association class | 1.00 | |||
| I–II | 49 (66%) | 8 (67%) | 41 (66%) | |
| III–IV | 24 (33%) | 4 (33%) | 20 (32%) | |
| Mortality † | 1 (1%) | 0 (0%) | 1 (2%) | 0.84 |
| At 6 months | ||||
| New York Heart Association status | 0.45 | |||
| I–II | 49 (66%) | 6 (50%) | 43 (69%) | |
| III–IV | 19 (26%) | 4 (33%) | 15 (24%) | |
| Mortality † | 6 (8%) | 2 (17%) | 4 (7%) | 0.25 |
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