EDITORIAL

Percutaneous Valve Implantation: Milestone or Millstone?

Roxane McKay*, M.D., F.R.C.S., F.R.C.S.C., FACC Department of Cardiology and Cardiovascular Surgery, Hamad Medical Corporation Doha, Qatar

IValvar lesions remain a challenging niche in the management of congenitally malformed hearts. In addition to prosthetic characteristics, issues of somatic growth, life-style preferences, long-term ventricular function, and multiple reoperations may impact upon both the timing and outcome of any intervention. Moreover, in contrast to acquired pathology on the left side of the heart, the indications for and benefits of pulmonary valve replacement have been less clearly defined and more difficult to balance against small but definite risks of resternotomy and cardiopulmonary bypass.
In this issue of Heart Views, Boudjemline and Bonhoeffer summarize their experience with percutaneous implantation of a gluteraldehyde preserved bovine venous valve into the right ventricular outflow tract of nine patients. By any standard, this is a remarkable technical achievement. Implantation was performed successfully and without significant complications in all nine cases where it was attempted, and, at a mean follow-up of eleven months, all valves were either completely competent or had trivial leakage on color Doppler echocardiography. Not only was improved right ventricular function achieved through reduction of the regurgitant volume overload, but also the early effects of valve implantation were isolated from those of surgical trauma and cardiopulmonary bypass, thus possibly demonstrating that a competent valve may be of potentially more benefit than previously recognized.
0 Although presently applicable to only a small subset of patients, if, as the authors propose, it shows long-term durability and can be adapted to other types pathology, this procedure could have considerable impact upon surgical management of the right ventricular outflow in a number of congenital heart malformations. For example, percutaneous valve implantation might be planned routinely to subsequently compensate transannular outflow patching in repair of Fallots tetralogy, which is frequently necessary1 and presently perceived to be a disadvantage of operation in early infancy. Or, the surgeon might endeavor to use a larger, valved extracardiac conduit in the correction of pulmonary atresia or truncus arteriosus, with the knowledge that a second valve could later be implanted within the graft. Given that pulmonary regurgitation rarely if ever requires emergency correction, another possibility could be the incorporation of tissue engineering, such that a "scaffold" was placed percutaneously into the right ventricular outflow tract, and the patients own cells then grew into it over a period of time to form a viable, competent valve.
The authors also describe their experimental work in preparation for aortic valve replacement and suggest that valves might be inserted into the atrioventricular positions or the Fontan circulation using percutaneous techniques as well. While these feats may well become possible in patients during the next few years, (and the authors enthusiasm for application of their technology is understandable), one wonders if this should not, perhaps, be tempered by the known results of similar procedures which have been done surgically for many years. In the higher-pressure systemic circulation, durability of the prosthesis assumes increasing importance.
While improvements have been made in the preparation of gluteraldehyde-preserved tissues2, evidence that this will significantly prolong their longevity in young patients is still awaited. And, as the authors themselves note, such limitations are shared equally by surgical and percutaneous approaches. In the case of Fontan pathways, neither homograft valves nor the native pulmonary valve have been demonstrated to function effectively long-term.3 Not withstanding occasional reports of improvement in protein-losing enteropathy after valve implantation, 4 current trends are to minimize rather than incorporate so-called "energy sinks" in this particular circulation.5 Indiscriminate insertion of valve tissue merely
because it can be done percutaneously could potentially become the reinvention of a wheel that has already turned rather poorly. Finally, one cannot help but note that a new word – "valvulation"- has been invented to describe this procedure! In the future, will we need to qualify whether the patient has undergone open, surgical "valvulation" or percutaneous, interventional "valvulation"? Or should we not, without recourse to Greek and Latin justification, just continue to use the accurately descriptive terms of "valve implantation?" Boudjemline, Bonhoeffer, and their colleagues6 are certainly to be congratulated for an important addition to the armaments of interventional cardiology. As the frontiers of this subspeciality approach those of cardiac surgery, however, it becomes increasingly important that patients benefit from the history, traditions, and innovations of both.

 References
 QUOTES

References

1. Walsh EP, Rockenmacher S, Keane JF, Hougen TJ, Locke JE, Castaneda AR. 
    Late results in patients with tetralogy of Fallot repaired during infancy.
    Circulation 1988;77:1062-7.

2. Mayne AS, Christie GW, Smaill BH, Hunter PJ, Barratt- Boyes BG. 
    An assessment of the mechanical properties of leaflets from four second-generation 
     porcine bioprostheses with biaxial testing techniques. 
    J Thorac Cardiovasc Surg 1989;98:170-80.

3. Ishikawa T, Neutze JM, Brandt PW, Barratt-Boyes BG. 
    Hemodynamics following the Kreutzer procedure for tricuspid atresia in 
    patients under two years of age. J Thorac Cardiovasc Surg 1984;88:373-9.

4. Crupi G, Locatelli G, Tiraboschi R. Villani M, De Tommasi M, Parenzan L.
    Protein-losing enteropathy after Fontan operation for tricuspid atresia
    (imperforate tricuspid valve). Thorac Cardiovasc Surg 1980;28:359-63.

5. Mighavacca F, de Leval MR, Dubini G, Pietrabissa R, Fumero R. 
    Computational fluid dynamic simulations of cavopulmonary connections with 
    an extracardiac lateral conduit. Med Eng Phys 1999;21:187-93.

6. Bonhoeffer P, Boudjemline Y, Qureshi SA, Le Bidois J, Iserin L, Acar P,
    Merckx J, Kachaner J, Sidi D. 
    Percutaneous insertion of the pulmonary valve. J Am Coll Cardiol 2002;39:1664-9.

QUOTES

Once a sage was asked why scholars always flock to the doors of the rich, whilst the rich are not inclined to call at the doors of scholars. “The scholars,” he answered, “are well aware of the use of money, but the rich are ignorant of the nobility of science.”                                               Al-Biruni, 973-1048 Science is the meeting place of two kinds of poetry: the poetry of thought and the poetry of action.                                             George Agostinho da Silva, 1906-1994 The reasonable man adapts himself to the world: the unreasonable persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.                                             George Bernard Shaw, 1856 – 1950, Irish playwright Everywhere the old order changes and happy they who can change with it.                                               William Osler, Principles and Practice of Medicine (1895) There is a great difference between knowing and understanding: you can know a lot about something and not really understand it.                                             Charles Kettering (1876 - 1958) Those that know, do. Those that understand, teach.                                                Aristotle It is the mark of an educated mind to be able to entertain a thought without accepting it.                                               Aristotle It takes the whole of life to learn how to live, and — what will perhaps amaze you more — it takes the whole of life to learn how to die.                                               Lucius Seneca (4 BC-65AD)