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Ann Thorac Surg 2002;73:1830-1836
© 2002 The Society of Thoracic Surgeons

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Original article: cardiovascular

Preliminary experience with the St. Jude Medical Regent mechanical heart valve in the aortic position: early in vivo hemodynamic results

^a Department of Cardiovascular Sciences, General Hospital "S. Maria Della Misericordia," Udine, Italy

Accepted for publication December 10, 2001.

* Address reprint requests to Dr Gelsomino, U. O. Cardiotoracica, Azienda Ospedaliera S. Maria Della Misericordia, Piazzale S. Maria Della Misericordia 11, 33100 Udine, Italy
e-mail: sandrogelsomino{at}virgilio.it

	Abstract

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
Background. The St. Jude Medical Regent is a new generation mechanical aortic valve.

Methods. Between March 2000 and July 2001, this valve was implanted in the aortic position in 40 patients (21 men; mean age 59.1 ± 9.0 years). Preoperatively, 24 patients (60%) were in New York Heart Association functional class III or IV. Eighteen patients (45%) underwent associated procedures. Mean valve size was 21.4 ± 2.4 mm. The mean duration of follow-up was 8.5 ± 4.5 months (range, 1 to 16 months).

Results. There were no operative deaths. Early complications included one reoperation for bleeding and one transient low output syndrome. Valve replacement was followed by a significant reduction in mean and peak transaortic gradients over time (p < 0.001) and analysis of variance failed to demonstrate statistical differences between valve size over time (p = not significant). A significant reduction in left ventricular hypertrophy occurred over time (p = 0.01) in all valve sizes (p = not significant between groups): baseline left ventricular mass index was 194 g/cm²; it reduced by 22 g/cm² (p = 0.006) at discharge. Left ventricular mass index decreased from 172 ± 55 g/cm² to 156 ± 44 g/cm² (p = 0.03) from discharge to 2 months. Further reductions were not significant. Relative wall thickness decreased from 0.57 ± 0.13 preoperatively to 0.42 ± 0.06 at discharge (p = 0.001), and again at 2 months (-0.2; p = not significant), and at 1 year (-0.02; p = not significant).

Conclusions. The early experience with the St. Jude Medical Regent valve has been satisfactory.

	Introduction

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
A continuing effort to improve the hemodynamic performance of mechanical heart valves has been made since Charles Hufnagel, in 1951, first implanted a ball valve placed into the descending thoracic aorta for treatment of aortic insufficiency [1]. At present several mechanical heart valves are available and all of them are considered to offer good hemodynamics and theoretically unlimited durability; nevertheless, they still do not meet all the criteria of an optimal substitute [2, 3], thus the search for an ideal mechanical heart valve continues [4].

The standard St. Jude Medical (SJM) disk valve (St. Jude Medical, Minneapolis, MN) was introduced for clinical use in 1977 [5] and, in the past 20 years, it has been one of the most widely used mechanical heart valves. The SJM Regent valve is a new generation mechanical aortic valve; it represents a design evolution of the SJM Hemodynamic Plus Series (SJM HP) with an increased orifice lumen area obtained by modifying the outside geometry of the orifice housing [6, 7].

This clinical study is a preliminary report of early in vivo hemodynamic performance of the SJM Regent mechanical heart prosthesis implanted in the aortic position.

	Material and methods

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
Patients
This analysis deals with the first 40 patients undergoing aortic valve replacement (AVR) with a SJM Regent mechanical valve in our institution between March 2000 (first implantation, March 3, 2000) and July 2001. Details are given in Table 1.

Follow-up information was obtained from outpatient clinic appointments; mean follow-up time was 8.5 ± 4.5 months (range, 1 to 16 months). Thirty-eight (95%), 29 (72.5%), and 9 (22.5%) patients reached 2-month, 6-month, and 1-year marks, respectively. No patient was lost at follow-up, which was 100% complete.

All data were collected following the Society of Thoracic Surgeons/American Association for Thoracic Surgery/European Association of Cardio-Thoracic Surgeons guidelines for reporting mortality and morbidity after aortic valvular procedures [8].

The investigational review board approved the study protocol and written informed consent was obtained from all patients before enrollment.

Echocardiography
All patients were monitored with serial echocardiograms; the first study was performed preoperatively, subsequent controls were at 2 months, 6 months, and 1 year, respectively. All examinations were performed by the same technician (Maria Luisa Monti) with a consensus of a cardiologist (G. Morocutti). Images were stored on tape for late off-line analysis.

Echocardiograms were recorded by Hewlett Packard Sonos 5500 ultrasound system with a 2.5 MHz transducer (Hewlett Packard, Andover, MA). M-mode, two-dimensional, continuous pulsed-wave, and color Doppler were carried out and standard views were used.

The presence of aortic regurgitation was quantified using color flow Doppler [9]; ratios of either percent diameter or percent area of the jet to that of the left ventricular outflow tract (LVOT) in the long- or short-axis views were calculated. The regurgitant orifice was measured at its origin, just below the aortic valve [10]. Aortic regurgitation was defined as trivial (grade I), mild (grade II), moderate (grade III), or severe (grade IV) if the ratio of the jet diameter-to-LVOT diameter in the long-axis view was less than 24%, 24% to less than 45%, 45% to less than 65%, or 65% and more, respectively. Similarly, aortic regurgitation was defined as trivial, mild, moderate, or severe if the ratio of the jet area-to-LVOT area in the short-axis view was less than 4%, 4% to less than 25%, 25% to less than 60%, or 60% and more, respectively.

In most of the patients, data are comparable and, in cases of mismatch, a global evaluation of other factors (continuous Doppler pattern, reverse diastolic flow in the thoracic aorta) helped us to give a reliable evaluation of regurgitation [11].

Measurements of end-systolic diameter (ESD), end-diastolic diameter (EDD), posterior wall thickness (WT), and septum thickness (ST) were first made according to the recommendation of the American Society of Echocardiography using a leading edge-to-leading edge convention [12]. Relative wall thickness was obtained as . Left ventricular mass (LVM) was calculated using measurements made according the Penn convention [13]. Fractional shortening (FS) was obtained as follows: . Left ventricular hypertrophy was defined as left ventricular mass index (LVMI) more than 131 g/m² for men and 100 g/m² for women [14]. Peak and mean velocities (in centimeters per square meter) and velocity time integral (in centimeters) were recorded across the aortic valve with continuous wave Doppler and outflow tract velocities were recorded with pulsed Doppler. All Doppler measurements were averaged from 3 to 10 cardiac cycles in sinus rhythm and in atrial fibrillation, respectively. Mean and peak pressure gradients were calculated from the Bernoulli equation modified with correction for LVOT [15].

Effective orifice area (EOA) was calculated using the continuity equation [16]: , where CSA_LVOT (in square centimeters) is the cross-sectional area of the LVOT obtained using two-dimensional measurements of the LVOT diameter, TVI_LVOT (in centimeters) is the velocity time integral of LVOT, and TVI_AO (in centimeters) is the velocity time integral in the aortic jet.

The EOA and LVM were indexed by patient’s body surface area and expressed as EOAI and LVMI. This index was used to detect patient-prosthesis mismatch; according to Pibarot and coworkers [17] an EOAI 0.85 cm²/m² was considered evidence of patient-prosthesis mismatch.

Left ventricular ejection fraction was calculated by using the apical four-chamber view and the application of the modified Simpson rule method [18].

The study valve
The SJM Regent mechanical prosthesis is a rotatable bileaflet valve with leaflets and orifice all fabricated from pyrolitic carbon [6]. It basically retains the features of the SJM HP valve, with the blood-contacting components having the same design and the same pivot mechanism as those of the standard and HP valves [7].

In contrast with HP prosthesis sewing cuff-retaining rims have been modified to allow a more complete suprannular implantation, thus achieving a larger lumen area. The outer profile results changed, compared to standard SJM valves, but the original structural valve integrity is preserved [6].

Surgical data and technique
Operative data are given in Table 2. There were no emergency cases. Eighteen patients (45%) underwent associated procedures. Those undergoing concomitant coronary artery bypass grafting had an average of 1.7 ± 0.2 grafts and 55.5% (5 of 9 patients) had a bypass with the left internal mammary artery. The host annulus was intraoperatively measured with a Hegar probe; mean annulus size was 20.4 ± 2.1 and mean patient annulus index, obtained by dividing the intraoperative annulus diameter by the patient’s body surface area was 11.9 ± 1.1 mm; mean valve size implanted was 21.4 ± 2.4 mm (p = not significant [ns]).

Operations were performed using cardiopulmonary bypass with moderate hypothermia and cold crystalloid cardioplegic cardiac arrest. The valve was implanted with a pledgeted interrupted 2-0 Ethibond suture (Ethicon Inc, Somerville, NJ) in a suprannular position. A noneverted suture was preferred to an everting suture, which, in our opinion, may reduce the performance of a hemodynamic favorable prosthesis. The operation was completed as usual.

From the first postoperative day, all patients started a regimen of lifelong treatment with warfarin sodium (Coumadin, DuPont Pharmaceuticals, Wilmington, DE). The target international normalized ratio was 2.0 to 3.0.

Statistical analysis
Data analysis was performed using the SPSS for Windows, release 8.0 (SPSS, Inc, Chicago, IL) statistical package. Continuous data were presented as mean ± standard deviation; discrete variables were given as percentages. Regression analysis was performed to study relations between variables. A repeated measure one-way and two-way analysis of variance were used to test the significance of changes in the data at various points of the study and over time by categories (ie, valve size, gender); the Sheffé posthoc test was used for multiple comparisons. Two-way analysis of variance was performed to assess changes in echocardiographic measures by valve size over time. Mann-Whitney U, Kruskall-Wallis, and Kendall’s nonparametric tests were used, where appropriate. In all cases a p value less than 0.05 was considered significant.

	Results

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Clinical data
There were no early (30-day) deaths. One patient experienced transient low output syndrome, which resolved with adequate pharmacologic support and 1 patient suffered from postoperative bleeding requiring reexploration.

A 72-year-old man undergoing urgent redo-AVR for mechanical prosthesis failure and compromised left ventricular function (left ventricular ejection fraction, 30%) died from low cardiac output syndrome 2 months after operation. At postmortem examination no technical or valve failure were demonstrated, and the death was not valve related. Short-term clinical follow-up was marked by a complete absence of endocarditis, anticoagulant-related hemorrhage, valve thrombosis, reoperations, and prosthetic failure. There was one episode of transient ischemic attack occurring 3 months after operation in a 75-year-old human with additional carotid artery disease. At the latest control mean New York Heart Association functional class was 1.5 ± 0.2 (p < 0.001 versus preoperatively).

In particular, at the 2-month visit 92.1% of patients were in New York Heart Association class II and I. At 6-month and 1-year controls, 96.5% and 100% of patients were in New York Heart Association functional class I or II, respectively.

Echocardiographic/hemodynamic assessments
Hemodynamic data are shown in Table 3. Peak transprosthetic systolic gradients reduced significantly over time (p < 0.001). At discharge it showed a decrement of 47.6 mm Hg from preoperative values (p < 0.001); it decreased again at subsequent controls but without statistical significance.

View larger version (65K): [in this window] [in a new window]   Fig 1. Mean transprosthetic gradients (mm Hg) by valve size at various time points of the study.

View larger version (24K): [in this window] [in a new window]   Fig 2. Effective orifice area index (cm2/m2) stratified by valve size. Two-way analysis of variance (ANOVA) failed to show statistical significance in increment of effective orifice area index over time by valve size.

The LVMI reduced significantly over time (p = 0.01). It decreased by 22 ± 12 g/cm² at discharge (p = 0.006) and by 16 ± 9 g/cm² (p = 0.03) from discharge to 2 months. Further reductions were not significant; analysis of variance did not show significant differences in LVMI reduction between different valve sizes (p = ns). Again, valve size was not related to LVMI at regression analysis (R² = 0.014, p = ns). Figure 3 shows LVMI by gender: there was no difference in LVMI between male and female patients at discharge (175 ± 60.8 g/cm² versus 170 ± 50.9 g/cm², p = ns). However, a significant difference was observed in LVMI between men and women at 2 months (162 ± 48.1 g/cm² versus 146 ± 42.2 g/cm², respectively, p = 0.031) and 6 months (156 ± 51 g/cm² versus 140 ± 44 g/cm², respectively, p = 0.04), but it did not reach a statistical significance at the 1-year study (156 ± 46 g/cm² versus 144 ± 44 g/cm², p = ns).

View larger version (12K): [in this window] [in a new window]   Fig 3. Mean values ± standard error of left ventricular mass index (LVMI) according to sex. Two-way analysis of variance for repeated measurements showed no significant differences in left ventricular mass index over time between men and women (p = 0.327).

Left ventricular ejection fraction did not show any significant changes over time (p = ns) and 2.5% and 2.6% of patients were below the fifth percentile at discharge and 2 months, respectively. By the 6-month and 1-year interval no patient was below the fifth percentile.

A trivial or mild aortic incompetence was detected in 45% (18 of 40), 55.2% (21 of 38), 75.9% (22 of 29), and 66.7% (6 of 9) of patients at discharge, 2 months, 6 months and 1 year, respectively. At late study the regurgitation was central in 83.3% (5 of 6 patients) and perivalvular in 6.7% (1 of 6 patients).

One patient, who reached 2 months of follow-up, showed moderate aortic incompetence due to a perivalvular leak. Up to 2 months no patient had any moderate or severe aortic incompetence.

	Comment

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
The SJM heart valve was the first bileaflet mechanical prosthesis with leaflets and orifice housing all fabricated from pyrolitic carbon [6]. Nicoloff first introduced the standard SJM disk valve for clinical use on October 3, 1977 [19, 20] and it has been in use for 20 years [21–23]. The SJM HP [7] was introduced in 1993. With its suprannular cuff configuration, it achieved a larger effective orifice area when compared to the SJM standard valve. In 1995 a new valve was implanted, the SJM Masters Series, with a rotatable cuff configuration. The Regent is a new generation SJM heart valve that represents a further evolution of the SJM design. It is a bileaflet, rotatable prosthesis, manufactured from pyrolitic carbon, which retains the characteristics of previous SJM valves with the advantage of an enlarged geometric orifice area achieved by a modification of sewing cuff-retaining rims and obtained without compromising the original structural valve integrity. In an in vitro study, Walker and colleagues [6] compared all sizes of the SJM Regent and SJM HP valve. They made steady flow and pulse flow measurements, using a simulator of the left heart system. They found that, for the small-sized valves (17 to 21 mm), EOA increased by 21% to 22% and the gradients reduced by 21% to 22% when the SJM Regent was compared to the SJM HP valve. Furthermore, the energy loss results showed approximately a one-size increment improvement of the SJM Regent over the HP valve, thus a two-size increment improvement over the SJM standard valve.

More recently, Ellis and Yoganathan [7] compared the hinge flow dynamics of 17 mm SJM Regent and 17-mm SJM HP valves. They concluded, "... Flow dynamics of 17 mm Regent valve were at least equivalent to, and possibly superior, to those of the 17-mm HP."

To explore if this increased orifice area might translate into improved hemodynamics even in vivo, we studied early data, obtained at rest by serial echocardiograms from patients undergoing AVR with the SJM Regent mechanical valve.

Valve replacement was followed by a significant reduction in mean and peak transaortic gradients over time (p < 0.001) without statistical differences between valve size. Patients also showed statistically significant increases at discharge (p < 0.001) and from discharge to the 6-month control (p = 0.04) without further statistically significant changes at late intervals.

It is widely accepted that a discrepancy between the prosthesis effective orifice area and the patient’s body surface area, a condition termed prosthesis-patient mismatch [17], usually seen after AVR with small-sized valves, results in abnormally high residual gradients, worsening of the patient’s hemodynamic status [24] and impaired regression of left ventricular hypertrophy [25]. Thus, this condition might require a reoperation [26]. In our experience, AVR with the SJM Regent valve minimized the problem of patient-prosthesis mismatch and at the 1-year control all patients had an EOAI more than 0.85 cm²/m².

A significant reduction in left ventricular hypertrophy occurred over time (p = 0.01) in all valve sizes (p = ns between groups): baseline LVMI was 194 g/cm²; it reduced by 22 g/cm² (p = 0.006) at discharge and by 16 g/cm² (p = 0.03) at 2 months. Further reductions were not significant. At 1 year LVMI was 151 ± 54 in the entire group, and 156 ± 46 g/cm² and 144 ± 44 g/cm² in men and women, respectively, remaining slightly above the normal range.

Although we gained superior hemodynamic results with stentless valves, in terms of effective orifice area, gradients [27] as well as regression of left ventricular hypertrophy [28], we believe that the results obtained with this new mechanical valve are satisfactory.

Although comparisons may not be appropriate because of differences in patient characteristics and study methods, our findings compare favorably with results reported by Bernal and coworkers [29] with the small-sized Carbomedics "Top Hat" valve (Sulzer Carbomedics Inc, Austin, TX), a new-generation suprannular mechanical prosthesis. In a period between 1 and 42 postoperative months, the 19-mm prostheses showed a mean gradient of 19.1 ± 4.4 mm Hg and an EOA of 1.0 ± 0.2 cm² in patients with a body surface area of 1.61 ± 0.16 m². In the present study patients receiving a 19-mm SJM Regent and with a similar body surface area (1.66 ± 0.09 m²) showed a lower mean gradient (17.8 ± 3.1) and larger EOA (2 ± 0.3 cm²).

In a prospectively randomized study, Autschbach and colleagues [30] compared three different mechanical valves: ATS (ATS Medical Inc, Minneapolis, MN) Carbomedics (CM, Sulzer Carbomedics Inc), and SJM HP. Transvalvular flow velocities at 1 year were 2.3 ± 0.4 m/s, 2.4 ± 0.04 m/s, and 2.3 ± 0.4 m/s for ATS, Carbomedics, and HP, respectively (p = ns) and LVMI were 166 ± 75 g/cm², 161 ± 54 g/cm², and 159 ± 59 g/cm² in the three groups, respectively (p = ns). Our results were very similar but our patients had a smaller patient annulus index (11.9 ± 1.1 versus 13.3 ± 1.5 [ATS], 13 ± 1.4 [Carbomedics], 12.7 ± 1.2 [SJM HP]) and received a smaller valve (21.4 ± 2.4 versus 24 ± 2 mm [ATS], 23.7 ± 1.6 [Carbomedics], 23.6 ± 1.9 [SJM HP]).

Finally, the incidence of aortic incompetence was low. At 6 months the insufficiency was absent in 7 patients (24.1%) and trivial or mild in 22 (75.9%); at 1 year 3 (33.3%) patients had no aortic insufficiency and in 6 (66.7%), it was trivial. None had an insufficiency graded mild, moderate, or severe at the late control.

The small number of patients strongly limits our report and the short follow-up fails to give definitive information about valve performance. Furthermore, we did not compare the SJM Regent with other mechanical prostheses. However, as far as we know, the present study represents the first clinical report regarding the SJM Regent and its only purpose was to explore short-term hemodynamic results of a new generation mechanical valve.

In conclusion, in our limited experience, the SJM Regent mechanical aortic valve has been associated with satisfactory early hemodynamic performance. Further investigation with a larger series of patients is necessary to confirm these features. Nevertheless, by our preliminary results SJM Regent seems to be a good choice for patients selected to receive a mechanical heart valve.

	Acknowledgments

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
We gratefully acknowledge the help of Dr Orlando Parise for statistical analysis. We thank Maria Luisa Monti and Lorenzo Del Mestre for collecting data and Viviana Giavedoni, Cristina Ceccotti, Dr Judith Wilson, and Laura Pilotto for their assistance in the manuscript preparation.

	References

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 

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