tricuspid valve is bicuspid

2
References 1. Parrino PE, Kron IL, Ross SD, et al. Spinal cord protection during aortic cross-clamping using retrograde venous perfu- sion. Ann Thorac Surg 1999;67:1589–95. 2. Martinez-Arizala A, Rigamonti DD, Long JB, Kraimer JM, Holaday JW. Effects of NMDA receptor antagonists following spinal ischemia in the rabbit. Exp Neurol 1990;108:232– 40. 3. Heron A, Lekieffre D, Le Peillet E, et al. Effects of an A1 adenosine receptor agonist on the neurochemical, behavioral and histological consequences of ischemia. Brain Res 1994; 641:217–24. 4. Goda H, Ooboshi H, Nakane H, Ibayashi S, Sadoshima S, Fujishima M. Modulation of ischemia-evoked release of exci- tatory and inhibitory amino acids by adenosine A1 receptor agonist. Eur J Pharmacol 1998;357:149–55. 5. Rokkas CK, Cronin CS, Nitta T, et al. Profound systemic hypothermia inhibits the release of neurotransmitter amino acids in spinal cord ischemia. J Thorac Cardiovasc Surg 1995; 110:27–35. Comparison Between Stentless Xenografts and Homografts To the Editor: We found interest in the article by Gross and associates com- paring the Prima stentless xenograft (Baxter Health Care Cor- poration, Edwards CVS Division, Irvine CA) to homografts [1]. They found a higher mean resting gradient in the Prima valves (13 vs 6 mm Hg). The authors attribute this finding to stiffer cusps due to glutaraldehyde preservation, rigidity of the Dacron sewing ring, and inward folding of the Dacron cuff beneath the coronary ostia. We wish to suggest another mechanism, the preservation of the noncoronary sinus. In common practice, the noncoronary sinus is preserved during implantation of valves such as the Prima, which are supplied as a full root, scalloping only the left and right sinuses. In contrast, when homografts are implanted using freehand technique, all three sinuses are scalloped. As- suming this difference in insertion technique was applied in Gross’s group (a point that was not clear in their description of the surgical technique), the nonresected prosthetic aortic wall may explain the higher gradients in the xenografts due to the added bulk in the aortic root. We compared hemodynamics at rest and during exercise of the Toronto Stentless Porcine Valve (TSPV; St Jude Medical, Minneapolis MN) and normal native aortic valves, and found a mean gradient of only 6 mm Hg across the Toronto valves. This resting mean gradient did not increase at exercise [2]. Others [3] have found lower mean gradients across the Toronto valve, irrespective of valve size. Like the Prima, the TSPV is a porcine valve, glutaraldehyde preserved, and reinforced with Dacron. Unlike the Prima, the TSPV is fully scalloped. This design difference may explain the difference in gradients. Another question that is yet unanswered is whether preser- vation of the noncoronary sinus causes uneven distribution of forces on the valve, possibly compromising durability. Finally, the advantage of stentless valves must be realized in improved patient survival. It seems obvious that lower gradients are better, but where is the cutoff? David and associates have shown in a retrospective study that stentless xenografts afford better survival than stented bioprostheses, probably due to better preservation of the left ventricle [4]. Whether this is dependant on gradient, or at what gradient this advantage is lost, is still unclear. Although it is still early to tell, stentless xenografts may indeed be a favorable substitute for homografts. Shuli Silberman, MD Nadiv Shapira, MD Dani Bitran, MD Department of Cardiothoracic Surgery Shaare Zedek Medical Center PO Box 3235 91031 Jerusalem, Israel e-mail: cts.szmc.org.il. References 1. Gross C, Harringer W, Beran H, et al. Aortic valve replace- ment: is the stentless xenograft an alternative to the ho- mograft? Midterm results. Ann Thorac Surg 1999;68:919–24. 2. Silberman S, Shaheen J, Fink D, et al. Comparison of exercise hemodynamics among nonstented aortic bioprostheses, me- chanical valves, and normal native aortic valves. J Card Surg 1998;13:412– 6. 3. Del Rizzo DF, Goldman BS, Christakis GT, David TE. Hemo- dynamic benefits of the Toronto Stentless Valve. J Thorac Cardiovasc Surg 1996;112:1431– 46. 4. David TE, Puschmann R, Ivanov J, et al. Aortic valve replace- ment with stentless and stented porcine valves: a case match study. J Thorac Cardiovasc Surg 1998;116:236 – 41. Tricuspid Valve Is Bicuspid To the Editor: We thank Drs Anderson and Wilcox [1] for their kind reference to our publication relating to the anatomy of the so-called tricuspid valve [2]. Perhaps there is a misunderstanding, possi- bly relating to the use of the word “mural.” A clarification is necessary though belated. Classically, the venous atrioventricular valve, christened by Era- sistratos as the tricuspid valve, is considered to have septal, anterior or anterosuperior, and posterior or inferior leaflets. The latter leaflet has also been referred to as the mural leaflet [3]. However, the term mural implies that the anterior leaflet is not mural. Hence, the label “inferior” or “posterior” is more appropriate. Based on a study of 100 human autopsy hearts, we pointed out that the veil of leaflet tissue of the valve hanging down from a D-shaped annulus consists of straight (septal) and curved (non- septal or mural) components. We introduced the use of commis- sural lines to separate these components. These are imaginary shortest perpendiculars, from the free edge to the annulus, on either side of the septal leaflet, which is always unscalloped. The curved component consists of the classical anterior and posterior leaflets. But commonly, the free edge of the curved leaflet component dips into the leaflet substance, creating up to six scallops in this curved segment, inclusive of the anterior and posterior leaflets. Therefore, a conflict arises in naming these scallops. To avoid this conflict, we suggested that the entire curved segment of the veil of leaflet tissue, suspended from the annulus related to the nonseptal, mural wall of the right ventri- cle, inclusive of the anterior and posterior leaflets, be named as mural leaflet. Thus, the tricuspid valve resembles the mitral valve, with a straight (septal) and a curved (mural) leaflet. The curved mural leaflet of the mitral valve may also have up to six scallops [4]. Comparative anatomy of the atrioventricular valves reveals that they evolve with straight and curved components [5, 6]. Viewing the “tricuspid valve” as “bicuspid” helps in bicus- pidization (separation of the straight and curved leaflets) for 1989 Ann Thorac Surg CORRESPONDENCE 2000;69:1983–96 © 2000 by The Society of Thoracic Surgeons 0003-4975/00/$20.00 Published by Elsevier Science Inc

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Page 1: Tricuspid valve is bicuspid

References

1. Parrino PE, Kron IL, Ross SD, et al. Spinal cord protectionduring aortic cross-clamping using retrograde venous perfu-sion. Ann Thorac Surg 1999;67:1589–95.

2. Martinez-Arizala A, Rigamonti DD, Long JB, Kraimer JM,Holaday JW. Effects of NMDA receptor antagonists followingspinal ischemia in the rabbit. Exp Neurol 1990;108:232–40.

3. Heron A, Lekieffre D, Le Peillet E, et al. Effects of an A1adenosine receptor agonist on the neurochemical, behavioraland histological consequences of ischemia. Brain Res 1994;641:217–24.

4. Goda H, Ooboshi H, Nakane H, Ibayashi S, Sadoshima S,Fujishima M. Modulation of ischemia-evoked release of exci-tatory and inhibitory amino acids by adenosine A1 receptoragonist. Eur J Pharmacol 1998;357:149–55.

5. Rokkas CK, Cronin CS, Nitta T, et al. Profound systemichypothermia inhibits the release of neurotransmitter aminoacids in spinal cord ischemia. J Thorac Cardiovasc Surg 1995;110:27–35.

Comparison Between Stentless Xenografts andHomograftsTo the Editor:

We found interest in the article by Gross and associates com-paring the Prima stentless xenograft (Baxter Health Care Cor-poration, Edwards CVS Division, Irvine CA) to homografts [1].They found a higher mean resting gradient in the Prima valves(13 vs 6 mm Hg). The authors attribute this finding to stiffercusps due to glutaraldehyde preservation, rigidity of the Dacronsewing ring, and inward folding of the Dacron cuff beneath thecoronary ostia.

We wish to suggest another mechanism, the preservation ofthe noncoronary sinus. In common practice, the noncoronarysinus is preserved during implantation of valves such as thePrima, which are supplied as a full root, scalloping only the leftand right sinuses. In contrast, when homografts are implantedusing freehand technique, all three sinuses are scalloped. As-suming this difference in insertion technique was applied inGross’s group (a point that was not clear in their description ofthe surgical technique), the nonresected prosthetic aortic wallmay explain the higher gradients in the xenografts due to theadded bulk in the aortic root. We compared hemodynamics atrest and during exercise of the Toronto Stentless Porcine Valve(TSPV; St Jude Medical, Minneapolis MN) and normal nativeaortic valves, and found a mean gradient of only 6 mm Hg acrossthe Toronto valves. This resting mean gradient did not increaseat exercise [2]. Others [3] have found lower mean gradientsacross the Toronto valve, irrespective of valve size. Like thePrima, the TSPV is a porcine valve, glutaraldehyde preserved,and reinforced with Dacron. Unlike the Prima, the TSPV is fullyscalloped. This design difference may explain the difference ingradients.

Another question that is yet unanswered is whether preser-vation of the noncoronary sinus causes uneven distribution offorces on the valve, possibly compromising durability.

Finally, the advantage of stentless valves must be realized inimproved patient survival. It seems obvious that lower gradientsare better, but where is the cutoff? David and associates haveshown in a retrospective study that stentless xenografts affordbetter survival than stented bioprostheses, probably due tobetter preservation of the left ventricle [4]. Whether this isdependant on gradient, or at what gradient this advantage is

lost, is still unclear. Although it is still early to tell, stentlessxenografts may indeed be a favorable substitute for homografts.

Shuli Silberman, MDNadiv Shapira, MDDani Bitran, MD

Department of Cardiothoracic SurgeryShaare Zedek Medical CenterPO Box 323591031 Jerusalem, Israele-mail: cts.szmc.org.il.

References

1. Gross C, Harringer W, Beran H, et al. Aortic valve replace-ment: is the stentless xenograft an alternative to the ho-mograft? Midterm results. Ann Thorac Surg 1999;68:919–24.

2. Silberman S, Shaheen J, Fink D, et al. Comparison of exercisehemodynamics among nonstented aortic bioprostheses, me-chanical valves, and normal native aortic valves. J Card Surg1998;13:412–6.

3. Del Rizzo DF, Goldman BS, Christakis GT, David TE. Hemo-dynamic benefits of the Toronto Stentless Valve. J ThoracCardiovasc Surg 1996;112:1431–46.

4. David TE, Puschmann R, Ivanov J, et al. Aortic valve replace-ment with stentless and stented porcine valves: a case matchstudy. J Thorac Cardiovasc Surg 1998;116:236–41.

Tricuspid Valve Is BicuspidTo the Editor:

We thank Drs Anderson and Wilcox [1] for their kind referenceto our publication relating to the anatomy of the so-calledtricuspid valve [2]. Perhaps there is a misunderstanding, possi-bly relating to the use of the word “mural.” A clarification isnecessary though belated.

Classically, the venous atrioventricular valve, christened by Era-sistratos as the tricuspid valve, is considered to have septal,anterior or anterosuperior, and posterior or inferior leaflets. Thelatter leaflet has also been referred to as the mural leaflet [3].However, the term mural implies that the anterior leaflet is notmural. Hence, the label “inferior” or “posterior” is moreappropriate.

Based on a study of 100 human autopsy hearts, we pointed outthat the veil of leaflet tissue of the valve hanging down from aD-shaped annulus consists of straight (septal) and curved (non-septal or mural) components. We introduced the use of commis-sural lines to separate these components. These are imaginaryshortest perpendiculars, from the free edge to the annulus, oneither side of the septal leaflet, which is always unscalloped.

The curved component consists of the classical anterior andposterior leaflets. But commonly, the free edge of the curvedleaflet component dips into the leaflet substance, creating up tosix scallops in this curved segment, inclusive of the anterior andposterior leaflets. Therefore, a conflict arises in naming thesescallops. To avoid this conflict, we suggested that the entirecurved segment of the veil of leaflet tissue, suspended from theannulus related to the nonseptal, mural wall of the right ventri-cle, inclusive of the anterior and posterior leaflets, be named asmural leaflet. Thus, the tricuspid valve resembles the mitralvalve, with a straight (septal) and a curved (mural) leaflet. Thecurved mural leaflet of the mitral valve may also have up to sixscallops [4]. Comparative anatomy of the atrioventricular valvesreveals that they evolve with straight and curved components [5,6]. Viewing the “tricuspid valve” as “bicuspid” helps in bicus-pidization (separation of the straight and curved leaflets) for

1989Ann Thorac Surg CORRESPONDENCE2000;69:1983–96

© 2000 by The Society of Thoracic Surgeons 0003-4975/00/$20.00Published by Elsevier Science Inc

Page 2: Tricuspid valve is bicuspid

tricuspid stenosis [7] and shortening the annulus related to thecurved (mural) leaflet during tricuspid annuloplasty [8].

Solomon Victor, FRCPVijaya M. Nayak, MS

The Heart Institute15 East StKilpauk Garden ColonyMadras 600 010, Indiae-mail: [email protected].

References

1. Anderson RH, Wilcox BR. Understanding cardiac anatomy:the prerequisite for optimal cardiac surgery. Ann Thorac Surg1995;59:1306–15.

2. Victor S, Nayak VM. The tricuspid valve is bicuspid. J HeartValve Dis 1994;3:27–36.

3. Hurst JW, Anderson RH, Becker AE, Wilcox BR. Atlas of theHeart. New York: Gower Medical Publishing Book Co., 1988:1.7.

4. Victor S, Nayak VM. Definition and function of commissures,slits and scallops of the mitral valve: analysis in 100 hearts.Asia Pacific J Thorac Cardiovasc Surg 1994;3:10–6.

5. Victor S, Nayak VM, Raveen R, Gladstone M. Bicuspidevolution of arterial and venous atrioventricular valves.J Heart Valve Dis 1995;4:78–87.

6. Victor S, Nayak VM. Design of atrioventricular valves span-ning six hundred thousand millenniums. Abstract from theSeventh Annual Meeting of Asian Society for CardiovascularSurgery, Singapore, May 1999.

7. Victor S, Nayak VM. Bicuspidization for tricuspid stenosis.Ann Thorac Surg 1998;65:1468–70.

8. Victor S, Nayak VM. C-ring tricuspid annuloplasty andchordal replacement using everted autogenous saphenousvein. Abstract from the 14th Biennial Asian Congress onThoracic & Cardiovascular Surgery, Lahore, December 1999:360.

ReplyTo the Editor:

We thank Drs Victor and Nayak for their response, albeit muchdelayed, to our comments concerning the tricuspid valve. Thereis, however, no misunderstanding, at least, not on our part. Wehave debated this matter previously, and have published ourown analysis of the arrangement of the tricuspid valve [1]subsequent to their study [2]. Victor and Nayak steadfastlyrefuse to contemplate the alternative interpretation. As westressed in the review that they question [3], valves functionwhen their leaflets are closed. Valves with two leaflets then havea solitary zone of apposition, whereas those with three leafletsclose in trifoliate fashion. As we demonstrated in our ownanalysis [1], and as is well known to echocardiographers, thetricuspid valve indeed closes in trifoliate fashion, and thereforepossesses the three leaflets recognized by Erasistratos. We alsopointed out in our review [3] that the evidence from hearts withEbstein’s malformation militates against the concept advancedby Victor and Nayak. In fact, the mural leaflet is that which isderived initially by a process of undermining of the musculardiaphragmatic surface of the inlet of the right ventricle [4]. Theantero-superior leaflet, in contrast, has a markedly differentdevelopmental origin. Victor and Nayak are fond themselves ofciting evidence from development sources to support theiranatomic hypotheses. All this evidence, morphologic, functional,and developmental, supports the notion that the tricuspid valvehas three leaflets, providing that the valve is analyzed in its

closed position as well as viewed exclusively when open as inthe autopsied specimen.

Robert H. Anderson, MD

Cardiac UnitInstitute of Child HealthUniversity College London30 Guilford StLondon WC1N 1EH, England

Benson R. Wilcox, MD

Division of Cardiothoracic SurgeryUniversity of North Carolina at Chapel HillChapel Hill, NC 27599-7065e-mail: [email protected].

References

1. Sutton JP III, Ho SY, Vogel M, Anderson RH. Is the morpho-logically right atrioventricular valve tricuspid? J Heart ValveDis 1995;4:571–5.

2. Victor S, Nayak VM. The tricuspid valve is bicuspid. J HeartValve Dis 1994;3:27–36.

3. Anderson RH, Wilcox BR. Understanding cardiac anatomy:the prerequisite for optimal cardiac surgery. Ann Thorac Surg1995;59:1366–75.

4. Lamers WH, Viragh S, Wessels A, Moorman AFM, AndersonRH. Formation of the tricuspid valve in the human heart.Circulation 1995;91:111–21.

Thoracoscopic Surgery, Video-Thoracoscopic Surgery,or VATS: A Confusion in DefinitionTo the Editor:

In the last decennium the introduction of mini-invasive tech-niques in thoracic surgery had made it possible for differentsurgical groups from around the world to publish a largenumber of articles on the subject. It is interesting that even todaythe abbreviation and terminology used to indicate the rightmini-invasive approach are not used uniformly; in fact, someauthors use thoracoscopic surgery, others video-thoracoscopy,and others video-assisted thoracic surgery (VATS).

We believe that video-thoracoscopic surgery (VTS) shouldindicate the procedure that uses the standard thoracoscope. Thepossible operative maneuvers with this technique are very few,such as biopsy of pleura and pleurodesis with talc; in this casethe chest tube is not positioned under vision because it is

Table 1. Proposed Nomenclature With Abbreviation forMini-Invasive Techniques in Thoracic Surgery

AbbreviationInstrumentation and

No. of Trocars

TS 5 thoracoscopicsurgery

Standard thoracoscope

VTS 5 video-thoracoscopicsurgery

Standard thoracoscopeconnected to a camera andin turn to a video

VATS 5 video-assistedthoracic surgery

Single skin incision or singletrocar, the optic is separatedfrom the surgicalinstruments

2-3-4 trocarsMini-thoracotomy

1990 CORRESPONDENCE Ann Thorac Surg2000;69:1983–96

© 2000 by The Society of Thoracic Surgeons 0003-4975/00/$20.00Published by Elsevier Science Inc