Aortic valve replacement in predominant aortic stenosis: What is an appropriate size valve?

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1 IJTCVS Joshi et al 141 Aortic valve replacement in predominant aortic stenosis: What is an appropriate size valve? Kishore Joshi, M.Ch., Sachin Talwar, M.Ch., Devagourou Velayoudham, M.Ch., Arkalgud Sampath Kumar, M.Ch. Cardiothoracic Centre, All India Institute of Medical Sciences, New Delhi, India Abstract Objective: This is a retrospective analysis of 94 patients who underwent aortic valve replacement for predominant aortic stenosis between January 1998 and December Patients and Methods: Age ranged from 16 to 70 years (mean 43.2±13.2 years). 73 were male (77.7%). Etiology was rheumatic in 71 (75.5%) and degenerative in 23 (24.5%) patients. On transthoracic echocardiography, the diameter of the aortic annulus ranged from 19 mm to 36mm (mean 28.5±3.0 mm) and the peak systolic gradients ranged from 54 mm to 174 mm of Hg (mean of 109.8±28.8 mmhg). Aortic regurgitation was absent or mild in 76 patients (80.8%) and moderate in rest. A mechanical valve was implanted in 66 patients (70.2%) and a tissue valve in 28 patients (29.8%). Valves of size 23 mm or more were implanted in 75 patients (80%). A valve of 25 mm or larger was implanted in 55 patients (54.3%). Results: There were no early deaths. Two patients required permanent pacemaker implantation for complete heart block in the immediate postoperative period. Prosthetic valve thrombosis in one patient was relieved by thrombolysis. Anticoagulant related hemorrhage was seen in two patients. One patient underwent homograft aortic valve replacement for prosthetic valve endocarditis nine months after surgery. Conclusion: Isolated aortic valve replacement in patients with predominant aortic stenosis can be performed safely by implanting an adequately large sized prosthesis, without root enlargement in a large majority of patients. (Ind J Thorac Cardiovasc Surg, 2007; 23: ) Key words: Aortic valve replacement, Aortic stenosis, Mechanical valves Introduction Surgeons consider small valves in aortic stenosis (AS) 1-6. Others use root enlargement techniques to implant adequately large sized valves There are few reports of large (27 mm-29 mm) valves implanted in aortic stenosis 2-4,11. Small aortic valve prosthesis (19-23mm) have been shown to produce significant gradients across the valves at rest and during exercise and may lead to prosthesis patient mismatch 19. Larger prosthesis are associated with a better prognosis than replacement with small prosthetic valves The size of the prosthesis should match as Address for correspondence: Dr. A. Sampath Kumar Department of Cardiothoracic and Vascular Surgery All India Institute of Medical Sciences New Delhi , India Telefax: asampath_kumar@hotmail.com IJTCVS /12 Received - 04/02/07; Review Completed - 16/02/07; Accepted - 04/05/07. closely as possible the native valve area for best hemodynamic performance and prognosis 9,23,24. Size of prosthesis implanted has been shown to be a surgeonrelated variable 24 and large sized prosthesis have been placed in the aortic position 11,25. In this study we evaluated if an adequately large size prosthesis could be implanted in the aortic position in patients with predominant aortic stenosis. Patients and Methods During the period from January 1998 to December 2004, 678 patients underwent aortic valve replacement (AVR) for all indications including double valve replacement (DVR), aortic homograft implantation and Ross procedure at Cardiothoracic Centre, All India Institute of Medical Sciences, New Delhi. Of these, 102 patients with predominant AS underwent AVR. Eight of these underwent AVR using aortic homograft or the pulmonary autograft and were excluded from the study. Data on demographic and clinical profile, diameter of the native aortic annulus, degree of associated aortic

2 142 Joshi et al IJTCVS Valve size in AVR 2007; 23: regurgitation, the severity of AS by transthoracic echocardiography (TTE) and valve morphology as assessed intraoperatively, was obtained. The size and type of valve used for AVR was also noted. Postoperative complications and follow up were also obtained. AVR with a mechanical valve was performed using the SJM aortic valve prosthesis (St. Jude Medical Inc., St. Paul, MN, USA Model No. AJ-501, AHPJ-505). Tissue valve used was the Carpentier Edwards perimount bovine pericardial bioprosthesis (Edwards Lifesciences Corporation, Irvine, CA, USA. Model No. 2900). Age of the patients ranged from 16 to 70 years (mean 43.2±13.2 years); 73 were male (77.7%). The weight of the patients was between 34 and 104 kg (mean 58.8±10.2 kg). Etiology was rheumatic in 71 patients (75.5%) and degenerative in 23 patients (24.5%) (Table 1). The native aortic valve was tricuspid in 71 patients Table 1. Demographic and clinical profile of patients undergoing aortic valve replacement for aortic stenosis Variable N Age (years) Range Mean 42.6±13.2 Male/Female 73/21 (77.7/22.3) Weight (kg) Range Mean 58.8±10.2 BSA (m 2 ) Range Mean 1.5±0.2 Etiology Rheumatic 71 (75.5) Nonrheumatic 23 (24.5) (75.5%) and bicuspid in the remaining. On transthoracic echocardiography, the diameter of the aortic annulus ranged from 19 mm to 36 mm (mean 28.5±3.0 mm) and peak systolic gradients ranged from 54 mmhg to 174 mmhg (mean 109.8±28.8 mmhg). Aortic regurgitation was absent or mild in 76 patients (80.8%) and moderate in 18 patients (19.2%). Surgical Technique After establishing cardiopulmonary bypass and aortic cross clamping, an oblique aortotomy was made. The incision was made 1 cm above the right coronary ostium and extended to the right into the non coronary sinus 5 mm above the aortic annulus. Direct ostial cardioplegia was delivered. The heart was cooled by topical ice slush. Commisural stay sutures were placed for traction, by which the valve annulus was pulled up for exposure. The valve leaflets were excised and all adherent calcium was debrided. Fibrous thickening over the endocardium in the left ventricular outflow tract and over the anterior mitral leaflet was also peeled. The prosthesis was seated using simple interrupted 2-0 braided polyester sutures. Aortic root enlargement was not performed in any patient. The prostheses were always implanted in an intra-annular position. Supra-annular implantation was not performed. Statistical Analysis Statistical analysis was performed using the statistical software SPSS for Windows Release , standard version (SPSS Inc, Chicago, IL, USA). Continuous variables are reported as mean ± standard deviation and median. Descriptive statistics were calculated for continuous and categorical variables. Reporting of valve related events is in accordance with the guidelines published earlier 15. Results Valves of size 19 mm to 29 mm were used for AVR (Table 2). Among the various sizes of aortic valve prostheses, the 23mm, 25mm and 27mm size valves were the most commonly used for AVR. The 23 mm valve was used in 24 patients (25.5%), 25mm valve in 27 patients (28.7%) and the 27 mm valve was implanted in 20 patients (21.3%). Seventy five patients (79.8%) received a prosthesis of 23 mm or larger in size. Fifty five patients (54.3%) received a prosthesis >25 mm while 39 patients (45.7%) received a prosthesis <25 mm in size. The valve size related to the body surface area is listed in Table 3. There was no co-relation between these indicating that valves of large sizes could also be implanted in small patients. Table 2. Distribution of various sizes of aortic valve prostheses Aortic valve Mechanical Bioprosthesis n size (mm) (3.2) (17.0) (25.5) (28.7) (21.3) (4.3) Total (100.0) <21 mm valves: 20.2% >23 mm valves: 79.8% >25 mm valves: 54.3%

3 IJTCVS Joshi et al 143 Table 3. Sizes of Aortic Valve prosthesis according to body surface area Valve Size (mm) Body Surface area (m 2 ) S.No. No. < > Total Associated Procedures Six patients underwent mitral valve repair in addition to AVR. The mitral valve was moderate to severely stenosed in these patients. Two patients also had a left atrial thrombus which was removed. The left atrial appendage was ligated in all of these six patients. Mortality All patients survived the operation. There were no early or late deaths. Follow up Of the 94 patients who underwent prosthetic valve replacement, 91 patients were followed up for a period of 2 months to 84 months (mean 31.7±22.4 months, median 26.5 months, 96.8% follow up). Three patients were lost to follow up. The total follow up was patient-years. The patients were followed at one month, 3 months, 6 months and then at yearly intervals with prothrombin time, international normalized ratio (INR), cinefluoroscopy (for mechanical valves) and echocardiography. Paravalvular leak There was no incidence of paravalvular leak either in the immediate postoperative period or in the follow up period. Valve Dysfunction No patient suffered structural deterioration of the valve prosthesis during the period of follow up. However prosthetic valve thrombosis occurred in one patient (0.4 events/100 patient-years). This was relieved by thrombolysis using streptokinase. Anticoagulant related hemorrhage Anticoagulant related hemorrhage was seen in 2 patients (0.8 events/100 patient-years). This was minor in both patients and did not require hospitalization. Both patients were managed conservatively. Prosthetic valve endocarditis There was one patient (0.4 events/100 patient-years) who underwent homograft aortic valve replacement for prosthetic valve endocarditis 9 months after AVR. His postoperative recovery was uneventful. Complete heart block Two patients developed complete heart block requiring permanent pacemaker implantation in the immediate postoperative period. Among these, complete heart block was noted intraoperatively in one patient and he underwent permanent pacemaker implantation on the fourth postoperative day. Another patient developed complete heart block on the 5 th postoperative day and she underwent permanent pacemaker implantation on the 21 st postoperative day. Discussion Insertion of a large prosthesis is essential during AVR because native valves have larger orifice areas 23. Though implantation of small prosthesis may result in significant symptomatic relief, this may produce patient-prosthesis mismatch with resultant transvalvuar gradients at rest which are increased during exercise 19. Large size valves have favourable hemodynamics and low gradients with resultant good exercise performance 24. Valve size is therefore a significant determinant of postoperative exercise capacity 16. Large majority of patients with AS have a small aortic root and receive small sized aortic prosthetic valves 1-6. Others utilize root enlargement procedures to enable implantation of larger valves The size of prosthesis implanted and reported earlier by various groups is summarized in Table 4. It is apparent that 46% of the valves implanted were 21 mm or less in size and only 22.3% were 25 mm or more in size. Kratz and colleagues in a review of 254 patients undergoing isolated AVR reported that small valves (<21mm) were implanted in 115 patients (45.3%) and large valves ( 23 mm) in 139 patients (54.7%) 5. Sawant and co-workers reported that 270 patients (46%) out of

4 144 Joshi et al IJTCVS Valve size in AVR 2007; 23: patients undergoing AVR in small aortic root, had a small aortic valve prosthesis implanted although they reported satisfactory short and long-term performance with these valves 6. In contrast, 80% of our patients receieved valves 23 mm or larger in size. Aortic valve dimension in the Indian population is similar to that in the West 23,24 Observations of aortic root dimensions in cadavers in India has shown that the mean aortic annulus diameter in adult Indian males aged years is 23.2±1.9 mm and in the adult Indian females aged years is 21.2±2.5 mm which corresponds to valve areas of 4.2 cm 2 (range cm 2 ) and 3.5 cm 2 (range cm 2 ) respectively 24. Therefore valve prosthesis of mm diameter are considered to match the native valves in terms of area 24. In our study we have implanted valves of 23 mm or more in size in 80% of the patients and valves of 25 mm or more in 55% of patients. Small sized aortic valve prosthesis (19 mm and 21 mm) were implanted in only 19 patients (20%). We have not implanted a 17 mm valve in any patient. In addition we have not performed root enlargement to implant large valves. Factors contributing to the size of prosthesis implanted Sizing of the Aortic annulus in aortic stenosis is critical for implantation of an adequate size valve. For this we rely on the diameter measured across the annulus at the point of attachment of the cusps (Fig. 1) on transesophageal echocardiography. For this the long axis view of the heart is ideal, with the transducer rotated to 120 degrees. Measurements made preoperatively by transthoracic echocardiography are operator dependent and vary widely. It is best for the surgeon to go with an open mind and measure the annulus again after excising the valve completely and removing all calcium and fibrous endocardial thickening. With the arrested flaccid heart it will be possible to fit in a larger valve than anticipated in the majority of patients, without need for annular enlargement. The surgeon has been shown to be an (a) (b) Fig. 1. (a) & (b) Measurement of aortic annulus diameter on transesophageal echocardiography Ao : Aorta, LV : Left Ventricle, RV : Right Ventricle important variable and implantation of large sized aortic valve prosthesis (>25mm) has been shown to be possible with a few technical modifications in the procedure 24. A low aortotomy gives excellent and unobstructed exposure of the aortic valve. Traction on the commissural stay sutures pulls up the aortic annulus to the level of the aortotomy permitting complete excision of the valve and removal of calcium from the annulus. During implantation of the valve through the aortotomy, the commissural stay sutures are removed and the valve is delivered into the left ventricle obliquely (mechanical valves) through the flattened aortic root, which assumes its maximum diameter. The valve is then pulled up and seated at the annulus and sutures tied. In our previous studies, we demonstrated that large sized aortic prosthesis can be implanted in patients with Aortic regurgitation in whom the root is dilated 24,25. Study limitations This study does not address the late functional results of AVR nor does it address regression of the ventricular mass correlated with prosthesis size. Estimating the effective orifice area of the valve and co-relating it with the body surface area of the patient is a better indicator of the haemodynamic performance of these valves than the manufacturer s size as it may be different for different brands. However, we have overcome this to Table 4. Sizes of aortic valve prosthesis implanted by different groups for aortic stenosis S. Valve Size No. Author No Gonzalez- Juanataley et al (23.1) 16 (30.8) 15 (28.9) 9 (17.3) Connoly et al (1.9) 3 (5.7) 8 (15.4) 30 (57.8) 6 (11.4) 3 (5.7) - 3. Medallion et al (20.6) 228 (28.2) 243 (30.0) 123 (15.2) 38 (4.7) 10 (1.2) 4. Teoh et al (18.4) 73 (22.7) 113 (35.2) 55 (17.1) 21 (6.5) - 5. Present study 94-3 (3.2) 16 (17.0) 24 (25.5) 27 (28.7) 20 (21.3) 4 (4.3)

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