J Thorac Cardiovasc Surg 2003;126:2109-2110
© 2003 The American Association for Thoracic Surgery
Apical versus basal partial ventriculectomy
P. P. Lunkenheimera,
R. H. Andersonb
a Klinik und Poliklinik für Thorax-, Herz- und Gefäßchirurgie, University Münster, Münster, Germany
b Cardiac Unit, Institute of Child Health, University College, London, United Kingdom
To the Editor:
With regard to the recent study of Koyama and colleagues published in the Journal of Thoracic and Cardiovascular Surgery,1 your readers should be aware that the authors have done no more than confirm the previous observations of Savage and colleagues,2 namely, that reducing volume by constricting or resecting the apical half of the ventricular cone has no significant effect on ventricular pump function. Their findings also confirm extensive clinical studies3-6 showing that reduction of the radius of the ventricle in its upper two thirds improves pump function, provided that the ventricle had been markedly dilated prior to such an intervention. Thus, simply by using a figure-of-eight symmetrical technique of resection, Konertz and colleagues5 have achieved results that surpass the current success of cardiac transplantation.
Your readers should also note that the technique used by the Japanese group to induce cardiac failure1 produced minimal alterations in left ventricular function. Thus, having reduced the radius of the left ventricle, the diameter in their experimental study was smaller than under control conditions. As is well established, however, any persistent therapeutic effect of reducing ventricular radius in the clinical situation is dependent in the degree of preexisting ventricular dilation.3-6
Furthermore, due to the beta-blockade used as part of the experimental setup, the ensuing bradycardia will have prevented their hearts from compensating adequately for the confined stroke volume, as would have occurred under physiological conditions simply due to an increase in heart rate. It is irrelevant, therefore, to measure cardiac output under these experimental conditions. At all events, stroke volume increased by one quarter when the radius was reduced along the basal two thirds of the heart.
There are then several other problems with the description and interpretation of the Japanese group1 that need to be drawn to the attention of your readers. It is incorrect to state that Batista advocated the apical region of the left ventricle as a primary area for resection. His primary intention was simply to reduce the radius of the dilated left ventricle. Furthermore, contrary to the conclusion drawn by the authors,1 the experimental results show clearly that plication of the apical segment produces no positive therapeutic effect. Nor, contrary to the assertions made by Torrent-Guasp and his colleagues,7,8 does such plication have any major detrimental impact on global ventricular pump function. When considering the differences observed in left ventricular function after apical or subbasal reduction of radius in this study, we need to remember that it is the extensive circular muscular layer enclosing the upper two thirds of the left ventricular cone that is largely responsible for left ventricular ejection. By reducing its radius, working conditions for the left ventricle are improved, thus ameliorating its pump function. This positive effect, however, is mitigated by plication of the interpapillary segment as performed by the Japanese investigators, as this procedure plicates also the marginal arteries. As has been shown,9 the resulting ischemic damage extends well beyond the plicated segment. Indeed, such collateral damage may well have been more significant in those hearts that were plicated up to the base in the Japanese study as compared with those plicated only along the apical half. The positive effect of reducing left ventricular radius probably would have been more pronounced had a less traumatic technique been used with the aim of preserving the marginal arteries.
In summary, therefore, the authors have done no more than confirm that resection or constriction at the apex has a strictly cosmetic effect on ejection fraction and a negligible effect on global left ventricular function. There is no need to invoke any pivotal impact of the spiraling muscles presumed to be involved in ventricular filling so as to explain the lack of therapeutic benefit. Indeed, the authors have provided no evidence of a major impairment of the dynamics of the ventricular filling apart from a moderate increase in the filling pressure of the left ventricle and a decrease by one tenth in stroke volume. In our opinion, this latter finding is more likely due to the overcorrection of the volume of the ventricle by reducing its long axis. They should remember that clinical results have now provided ample evidence that when the left ventricle is dilated, resection of any part of its walls, including the septum, is tolerated without impairing left ventricular function.3-6 Indeed, a marked improvement in left ventricular function is achieved whenever the radius of the upper two thirds of the left ventricle is significantly reduced. The conclusions drawn by the authors, namely, that surgical intervention on the left ventricular apex is markedly detrimental, are not, in our opinion, supported by their experimental evidence.
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References
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- Koyama T, Nishimura K, Soga Y, Unimonh O, Ueyama K, Komeda M. Importance of preserving the apex and plication of the base in left ventricular volume reduction surgery. J Thoracic Cardiovasc Surg. 2003;125:669–677[Abstract/Free Full Text]
- Savage EB, Downing SW, Ratcliffe MB, et al. Repair of left ventricular aneurysm. Changes in ventricular mechanics, hemodynamics, and oxygen consumption. J Thorac Cardiovasc Surg. 1992;104:752–762[Abstract]
- Batista RJV, Santos JLV, Takeshita N, et al. Partial left ventriculectomy to improve left ventricular function in end-stage heart disease. J Card Surg. 1996;11:96–97[Medline]
- Dowling RD, Koenig SC, Ewert DL, Laureano MA, Gray LA. Acute cardiovascular changes of partial left ventriculectomy without mitral valve repair. Ann Thorac Surg. 1999;67:1470–1472[Abstract/Free Full Text]
- Konertz W, Khoynezhad A, Sidiropoulos A, Borak V, Baumann G. Early and intermediate results of left ventricular reduction. Eur J Cardiothorac Surg. 1999;15(Suppl 1):S26–30 discussion. S39–43[Medline]
- Suma Hthe RESTORE GROUP. Left ventriculoplasty for nonischemic dilated cardiomyopathy. Semin Thorac Cardiovasc Surg. 2001;13:514–521[Medline]
- Torrent-Guasp F, Ballester M, Buckberg GD, et al. Spatial orientation of the ventricular muscle band: physiologic contribution and surgical implication. J Thorac Cardiovasc Surg 2001;122:389–2.
- Buckberg GD, Clemente C, Cox JL, et al. The structure and function of the helical heart and its buttress wrapping. Concepts of dynamic function from the normal macroscopic helical structure. Semin Thorac Cardiovasc Surg. 2001;13:342–357[Medline]
- Lunkenheimer PP, Redmann K, Cryer CW, et al. Late ventricular structure following partial left ventriculectomy: a case report. Ann Thorac Surg. 2000;69:1257–1259[Abstract/Free Full Text]
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References