The number of patients undergoing reoperation for valvular heart disease is increasing and will continue to increase as the general population ages.1 These reoperations most commonly involve structural deterioration of a bioprosthesis or progression of native-valve disease after nonvalve cardiac surgery. Structural failure of a biologic valve should be considered a part of the natural evolution of tissue valves and should be fully appreciated by both the surgeon and the patient prior to implantation.2 Reoperations are technically more difficult than primary operations because of adhesions around the heart with an associated risk of reentry, the presence of more advanced cardiac pathology, and the existence of more frequent comorbidities such as pulmonary hypertension. Perhaps most importantly, reoperative valve replacement operations often are performed in functionally compromised patients who tolerate complications poorly or who have little reserve.3 As a consequence of these and other factors, reoperative valve surgery historically has been associated with a considerably higher operative mortality than primary valve surgery, particularly in patients who have had multiple prior replacements.4 In the modern era, however, with the use of alternative surgical approaches and advanced perioperative care, there has been significant improvement in outcomes.5-9
Reductions in operative risk and postoperative morbidity after reoperative valve surgery have been made in the past few years through advances in myocardial protection, as well as alternative perfusion strategies such as the proper use of deep hypothermic cardiac arrest.10 In addition, use of peripheral cannulation techniques to institute cardiopulmonary bypass (CPB) has become a relatively standard practice in reoperative cases.11-13 Early institution of CPB prior to reentry prevents injury to the right ventricle (RV) or patent coronary artery bypass grafts during reoperative sternotomy.
Successful replacement of degenerated cardiac valves usually results in symptomatic and hemodynamic improvement. In this regard, improvements in valve design have mitigated but not eliminated primary bioprosthetic failure.14-16 As such, the risk of re-replacement for bioprosthetic failure remains a significant factor to be considered in the selection of valve type for implantation.17
MECHANICAL VERSUS BIOLOGIC VALVES
The most appropriate valve substitute for an individual patient remains a source of much controversy. This choice should be adapted to each individual patient depending on age, life expectancy, life style, valve size, and cardiac as well as noncardiac comorbidities.18 Some studies comparing the long-term outcomes between biologic and mechanical aortic valve prostheses have yielded similar results with regard to overall valve-related complications.19-22 However, most recent large studies have documented that anticoagulant-related bleeding with mechanical valves must be balanced against life expectancy and the risk of biologic valve re-replacement.23-25 Bioprosthetic valves are known to undergo a time-dependent process of structural deterioration that results in freedom of reoperation of 80% at 15 years.20 Consequently, structural degeneration of a bioprosthesis is the most frequent indication for reoperation in patients with tissue valves.19,26