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Division of Cardiovascular Surgery, Toronto General Hospital, 200 Elizabeth St, Toronto, ON M5G 2C4 Canada
(Email: vidyadhar.lad{at}uhn.on.ca).
I read with great interest the article by Yoshikawa and colleagues' [1] report of observations suggesting that a small St. Jude Medical (SJM) valve (St. Jude Medical Inc, St. Paul, MN) can be advantageously used in most Japanese patients because their body size is generally smaller than that of Western patients. The authors have reported actuarial survival at 10 years as 90.9% ± 8.7%, which drops to 25.2% ±21.0% at 20 years in patients undergoing aortic valve replacement (AVR) using a 19-mm prosthesis. Although the authors emphasize that the deaths are not valve related, philosophically the patients are most concerned with not why they die, but the fact that they do die. Most published studies including this one [1] emphasize that patient–prosthesis mismatch (PPM) has no effect on survival after AVR, yet the majority of longest reported survival is 10 years [2, 3], which is reasonably good, but it certainly drops significantly as it extends beyond this time period [4, 5]. In addition, in these studies [1–5], the majority of the patients were elderly; they seem to be more tolerant to small aortic prostheses owing to less physical activity than younger patients.
With this background information, I wish to add a comment applicable to the practice of many cardiovascular surgeons in Asia. Juvenile rheumatic aortic stenosis (age 
30 years) necessitating valve replacement is well known in the Indian subcontinent [6]. The patient population here is also typically small in size, with small aortic roots. In these individuals, with a longer life expectancy, I believe one can not be satisfied with a 25% survival at 20 years. In an earlier study, Pai and colleagues [7] showed that young rheumatics (mean age, 36 years; body surface area, 1.53 m2) with aortic stenosis, who were undergoing AVR using an SJM valve, mild PPM and moderate PPM in those receiving a 19-mm valve was poorly tolerated, even though the drop in trans-prosthetic gradient (TPG) and left ventricular mass index (LVMI) were maximum. At 6-month follow-up, the mean TPG was 48 mm Hg and the mean LVMI was 159 g/m2. Although it can be argued that if these patients been followed-up longer, then a decreasing trend could have been seen; it does not seem to happen. Sharma and colleagues [8] have shown that the drop in TPG and regression in LVMI reaches a stable value by 6 months after surgery. Persistently elevated left ventricular mass in these patients, as a result of a small prosthesis with obstructive gradients, may increase the risk of sudden death. Data from hypertension literature supports the concept of lowering the risk of sudden cardiac death by facilitating the regression of left ventricular hypertrophy [9].
Based on the available literature, it is difficult to establish the influence of small valves on the postoperative clinical outcome, yet it is clearly conceivable that a 19-mm valve that would be appropriate in an old patient should be avoided in young active patients in whom 20 to 30-year survival is a reasonable target. Add the growth of pannus to this on these small valves, further reducing the effective valve orifice area with years to follow. In these patients, surgical strategies should be considered to avoid PPM, such as aortic annular patch enlargement or homograft or autograft insertion. Of these, aortic annular patch enlargement may be the safest and most reproducible one, and allows insertion of a prosthetic valve one to two sizes larger, rather than with AVR alone [10].
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  S. Fukunaga and K. Yoshikawa Reply Ann. Thorac. Surg., January 1, 2009; 87(1): 354 - 355. [Full Text] [PDF]
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