- Email: [email protected]
Double-loop sternal wiring technique
320
CORRESPONDENCE
3. Zamvar V, Lawson RAM. Technique for finding the left anterior descending coronary artery [letter]. Ann Thorac Surg 1995;60:1457-8.
Reply To the Editor: We congratulate Dr Fisk on the impressive figures he has quoted in his letter, and we entirely agree with his viewpoint. Faced with the prospect of an LAD that is not easily found, some surgeons will blindly dissect in the region of the proximal LAD in the hope of finding it. Bleeding from the small transverse veins may be troublesome, and luck often plays a role in the LAD being found. Doctor Oz's technique is basically the use of the same approach, but in a more controlled manner, and so perhaps the incidence of right ventricular perforation is substantially decreased. The technique of using the diagonal branch for retrograde probing has been used by us on a few occasions, but sometimes this cannot be used when the diagonal artery (which is big enough to accommodate the probe) is given otI from the LAD proximal to the diseased portion of the LAD. We have not yet had to use the retrograde probing technique for the circumflex artery. We agree with Dr Oz's remark about the intramuscular LAD being always to the right of the great cardiac vein, although on a few occasions we have found the LAD to the left of the great cardiac vein.
Vipin Zamvar, FRCS IL A~ M. Lawson, FRCS Wythenshawe Hospital Southmoor Rd, Wythenshawe Manchester M23 9LT England
Ann Thorac Surg 1996;62:317-24
around this axis. The arm in the axis usually breaks or weakens at the fastening site by excess torsion. Inspection might be more helpful than a subjective tightness feel to prevent this problem. Between December 1994 and December 1995 we used this technique in 44 coronary artery bypass grafting procedures (left internal mammary artery was used in 43 of them) and 7 valvular procedures, a total of 51 open heart procedures, in patients suspected to be at risk for sternal complications. We did not use this technique in a randomized fashion that would allow us to make comparison with other techniques. The hospital records were investigated retrospectively. The mean age (-+ standard error) was 58.3 + 1.39 years (range, 29 to 72 years), and 39 (76.5%) of them were male. Even though most of them were obese or elderly patients, 3 had extended intubation (more than 48 hours), 2 had superficial wound infection, and I had hemiplegia; but we did not observe any sternal dehiscence or instability even in fractured and osteoporotic sternums on physical examination. There was no wire snapping or sternal gap in the chest roentgenograms either at discharge or 2 months postoperatively. By double-looping the wires, one can achieve an easy and firm approximation of the sternal edges with half the traction force by doubling the pulling length, just like the principle used in a set of pulleys. The possibility of wire snapping is reduced to half by doubling the carrying forces. The double bundle of steel wire exerts half the cutting pressure over the sternum because the thickness of the cutting surface is doubled. It is possible to combine this technique with other reinforcement methods [3]. Another practical advantage of the technique is, if a thread breaks while twisting, you do not need to reopen the sternum; you simply take back one of the loops to extend the wire to reattach the arms. In conclusion, the double-loop sternal wiring technique is
D o u b l e - L o o p Sternal W i r i n g T e c h n i q u e
To the Editor: We read the ingenious technique of Roux and colleagues [1] with great interest. The quality of osteosynthesis affects the consolidation of sternotomy, but one can achieve a good osteosynthesis without assistance, effort, or even a specially designed device, with the usual steel threads and a double-loop wiring technique. Two important causes of sternal dehiscence, sternal tearing or wire snapping, especially in elderly or obese patients, also could be minimized with this uncomplicated and effective method. Usually we place two steel threads above the manibrium by simple and four below by a double-loop wiring technique (Fig 1). The technique resembles the closure of median sternotomy with transsternal figure-of-8 wires [2], but in this technique we use the same intercostal space when doubling the loop. It therefore is possible to place more threads with an easier method. Placing the wires intercostally below the manubrium improves the resistance against the tearing forces over the sternum. Intercostal wiring also maintains good matching of the sternotomy edges, and the wires slide more easily while approximating. After pulling the wires and turning the arms around each other two or three times, we twist them firmly with a needle-holder until appropriate tension is achieved. While the wires are twisted, the crossing arms should embrace each other spirally. At a certain point, if one continues twisting excessively, one of the wire arms turns as the axis and the other begins to coil © 1996 by The Society of Thoracic Surgeons Published by Elsevier Science Inc
Fig 1. Appfication of double-loop wiring technique: the two cranially placed wires on the manubrium are placed with standard technique. 0003-4975196l$15.00
Ann Thorac Surg 1996;62:317-24
CORRESPONDENCE
effective, simple, and reproducible to achieve good osteosynthesis and minimize sternal dehiscence and instability.
Melih Erdinc, MD Ahmet Ocal, MD Husnu Sezer, MD Ahmet Kuzgun, MD Cuneyt Ozturk, MD
References 1. Roux D, Fournial G, Glock Y, Rottin N. New technique for sternal osteosynthesis. Ann Thorac Surg 1995;60:1132. 2. Goodman G, Palatianos GM, Bolooki H. Technique of closure of median sternotomy with trans-sternal figure-of-eight wires. J Cardiovasc Surg 1986;27:512-3. 3. Robicsek F, Daugherty HK, Cook JW. The prevention and treatment of sternal seperation following open heart surgery. J Thorac Cardiovasc Surg 1977;73:267-8.
Systolic
Average T r a n s m u r a l To the Editor:
We read with great interest the article by Chen and associates [1] that described a technique of measuring transmural myocardial pressure using a fluid-filled balloon. However, we have great reservations in accepting their claim that a significant reduction in systolic average transmural myocardial pressure occurred due to the essential flaw in using untransformed fast muscle in their experiments. Despite a wealth of ongoing experimental data collected from both human and animal models since the debut of dynamic cardiomyoplasty, its mechanism(s) of action still remains far from clear [2, 3]. In this respect, the evidence presented so far on the hemodynamic effects of this procedure has been conflicting [4]. This has led various groups to propose different theories of mechanisms to account for the discrepancy between the subjective improvement in functional status and quality of life and the lack of consistent demonstrable hemodynamic benefit. Systolic "squeeze" assist, passive girdling effect, reversal of chronic chamber remodeling, and a reduction in systolic and diastolic wall stress were among such proposed mechanisms. Chen and associates demonstrated a significant reduction in systolic average transmural myocardial pressure using a fluidfilled balloon in an acute goat model of dynamic cardiomyoplasty. Techniques designed to measure intramuscular pressure in contracting muscle posed great practical challenges. Measurement of pressure within a fluid-filled balloon interposed between the myocardium and the latissimus dorsi flap eliminated this problem while permitting the direct calculation of transmural myocardial pressure. However, interpretation of their results is severely hampered by the use of untransformed latissimus dorsi muscle in a normal heart. It is a well-known fact that during fiber-type transformation, muscle loses not only its mass and power but also the speed of contraction [5]. A reduction in systolic transmural myocardial pressure and wall stress cannot be maintained if the contraction of the transformed muscle wrap is slower than that of the myocardium. This differs from the phenomenon of reduction in diastolic wall stress, which depends on an artificial ventricular hypertrophy created by the presence of the muscle wrap regardless of its contractile properties. We strongly believe therefore that the use of untransformed muscle in the setting of dynamic cardiomyoplasty © 1996 by The Society of Thoracic Surgeons Published by Elsevier Science Inc
research is unhelpful or even misleading. In particular, there is no place for the incorporation of untransformed muscle in an experimental design after a decade of clinical cardiomyoplasty employing only trained muscle. Further progress toward the understanding of its mechanism(s) of action can only be achieved with research that employs transformed latissimus dorsi muscle.
Augustine Tang, FRCSEd Timothy L. Hooper, MD
Baglan cad Orgen apt 18/3 16090 Cekirge, Bursa, Turkey
T e c h n i q u e for M e a s u r i n g a R e d u c t i o n in Pressure
321
Department of Cardiothoracic Surgery Regional Cardiothoracic Unit Wythenshawe Hospital Southmoor Rd Manchester M23 9LT United Kingdom
References 1. Chen FY, Aklog SML, deGuzman BJ, et al. New technique measures decreased transmural myocardial pressure in cardiomyoplasty. Ann Thorac Surg 1995;60:1678-82. 2. Kass DA, Baughman MD, Pak PH, et al. Reverse remodeling from cardiomyoplasty in human heart failure; external constraint versus active assist. Circulation 1995;91:2314-8. 3. Bellotti G, Moraes A, Bocchi E, et al. Late effects of cardiomyoplasty on left ventricular mechanics and diastolic filling. Circulation 1993;88(part 2):304-8. 4. El Oakley RM, Jarvis J. Cardiomyoplasty; a critical review of experimental and clinical results. Circulation 1994;90:2085-90. 5. Jarvis J. Power production and working capacity of rabbit tibialis anterior muscles after chronic electrical stimulation at 10 Hz. J Physiol 1993;470:157-69.
Reply To the Editor: We appreciate the comments of Drs Tang and Hooper and thank them. In summary, they question the interpretation of our results because untransformed latissimus dorsi muscle (LD) was applied to normal myocardium in an acute goat model of cardiomyoplasty. They believe strongly that the use of untransformed muscle in dynamic cardiomyoplasty (DCM) research is misleading and should not be used. We address their concerns. We are unclear regarding the statement that "a reduction in systolic transmural myocardial pressure and wall stress cannot be maintained if the contraction of the transformed muscle wrap is slower than that of the myocardium." If Tang and Hooper mean "contraction" to be velocity of shortening when the heart is wrapped with LD, we disagree. The velocity of LD shortening is always slower than that of the myocardium when the net systolic transmural myocardial pressure is reduced. In such a situation, the muscle wrap is intimately applied to the epicardium, and the rate of volume change inside the wrap is equivalent to the rate of volume change inside the heart. Assuming both the wrap and the myocardium to be spherical for simplicity, we may apply the formula for volume of a sphere: 4
v = ~rr 3
(1)
where V = volume of the sphere and r = radius of the sphere. The circumference of the sphere is given by C = 27rr
(2)
where C = the circumference. Substituting (2) into (1) and differentiating with respect to time yields the rate of change of 0003-4975/96/$15.00
CORRESPONDENCE
3. Zamvar V, Lawson RAM. Technique for finding the left anterior descending coronary artery [letter]. Ann Thorac Surg 1995;60:1457-8.
Reply To the Editor: We congratulate Dr Fisk on the impressive figures he has quoted in his letter, and we entirely agree with his viewpoint. Faced with the prospect of an LAD that is not easily found, some surgeons will blindly dissect in the region of the proximal LAD in the hope of finding it. Bleeding from the small transverse veins may be troublesome, and luck often plays a role in the LAD being found. Doctor Oz's technique is basically the use of the same approach, but in a more controlled manner, and so perhaps the incidence of right ventricular perforation is substantially decreased. The technique of using the diagonal branch for retrograde probing has been used by us on a few occasions, but sometimes this cannot be used when the diagonal artery (which is big enough to accommodate the probe) is given otI from the LAD proximal to the diseased portion of the LAD. We have not yet had to use the retrograde probing technique for the circumflex artery. We agree with Dr Oz's remark about the intramuscular LAD being always to the right of the great cardiac vein, although on a few occasions we have found the LAD to the left of the great cardiac vein.
Vipin Zamvar, FRCS IL A~ M. Lawson, FRCS Wythenshawe Hospital Southmoor Rd, Wythenshawe Manchester M23 9LT England
Ann Thorac Surg 1996;62:317-24
around this axis. The arm in the axis usually breaks or weakens at the fastening site by excess torsion. Inspection might be more helpful than a subjective tightness feel to prevent this problem. Between December 1994 and December 1995 we used this technique in 44 coronary artery bypass grafting procedures (left internal mammary artery was used in 43 of them) and 7 valvular procedures, a total of 51 open heart procedures, in patients suspected to be at risk for sternal complications. We did not use this technique in a randomized fashion that would allow us to make comparison with other techniques. The hospital records were investigated retrospectively. The mean age (-+ standard error) was 58.3 + 1.39 years (range, 29 to 72 years), and 39 (76.5%) of them were male. Even though most of them were obese or elderly patients, 3 had extended intubation (more than 48 hours), 2 had superficial wound infection, and I had hemiplegia; but we did not observe any sternal dehiscence or instability even in fractured and osteoporotic sternums on physical examination. There was no wire snapping or sternal gap in the chest roentgenograms either at discharge or 2 months postoperatively. By double-looping the wires, one can achieve an easy and firm approximation of the sternal edges with half the traction force by doubling the pulling length, just like the principle used in a set of pulleys. The possibility of wire snapping is reduced to half by doubling the carrying forces. The double bundle of steel wire exerts half the cutting pressure over the sternum because the thickness of the cutting surface is doubled. It is possible to combine this technique with other reinforcement methods [3]. Another practical advantage of the technique is, if a thread breaks while twisting, you do not need to reopen the sternum; you simply take back one of the loops to extend the wire to reattach the arms. In conclusion, the double-loop sternal wiring technique is
D o u b l e - L o o p Sternal W i r i n g T e c h n i q u e
To the Editor: We read the ingenious technique of Roux and colleagues [1] with great interest. The quality of osteosynthesis affects the consolidation of sternotomy, but one can achieve a good osteosynthesis without assistance, effort, or even a specially designed device, with the usual steel threads and a double-loop wiring technique. Two important causes of sternal dehiscence, sternal tearing or wire snapping, especially in elderly or obese patients, also could be minimized with this uncomplicated and effective method. Usually we place two steel threads above the manibrium by simple and four below by a double-loop wiring technique (Fig 1). The technique resembles the closure of median sternotomy with transsternal figure-of-8 wires [2], but in this technique we use the same intercostal space when doubling the loop. It therefore is possible to place more threads with an easier method. Placing the wires intercostally below the manubrium improves the resistance against the tearing forces over the sternum. Intercostal wiring also maintains good matching of the sternotomy edges, and the wires slide more easily while approximating. After pulling the wires and turning the arms around each other two or three times, we twist them firmly with a needle-holder until appropriate tension is achieved. While the wires are twisted, the crossing arms should embrace each other spirally. At a certain point, if one continues twisting excessively, one of the wire arms turns as the axis and the other begins to coil © 1996 by The Society of Thoracic Surgeons Published by Elsevier Science Inc
Fig 1. Appfication of double-loop wiring technique: the two cranially placed wires on the manubrium are placed with standard technique. 0003-4975196l$15.00
Ann Thorac Surg 1996;62:317-24
CORRESPONDENCE
effective, simple, and reproducible to achieve good osteosynthesis and minimize sternal dehiscence and instability.
Melih Erdinc, MD Ahmet Ocal, MD Husnu Sezer, MD Ahmet Kuzgun, MD Cuneyt Ozturk, MD
References 1. Roux D, Fournial G, Glock Y, Rottin N. New technique for sternal osteosynthesis. Ann Thorac Surg 1995;60:1132. 2. Goodman G, Palatianos GM, Bolooki H. Technique of closure of median sternotomy with trans-sternal figure-of-eight wires. J Cardiovasc Surg 1986;27:512-3. 3. Robicsek F, Daugherty HK, Cook JW. The prevention and treatment of sternal seperation following open heart surgery. J Thorac Cardiovasc Surg 1977;73:267-8.
Systolic
Average T r a n s m u r a l To the Editor:
We read with great interest the article by Chen and associates [1] that described a technique of measuring transmural myocardial pressure using a fluid-filled balloon. However, we have great reservations in accepting their claim that a significant reduction in systolic average transmural myocardial pressure occurred due to the essential flaw in using untransformed fast muscle in their experiments. Despite a wealth of ongoing experimental data collected from both human and animal models since the debut of dynamic cardiomyoplasty, its mechanism(s) of action still remains far from clear [2, 3]. In this respect, the evidence presented so far on the hemodynamic effects of this procedure has been conflicting [4]. This has led various groups to propose different theories of mechanisms to account for the discrepancy between the subjective improvement in functional status and quality of life and the lack of consistent demonstrable hemodynamic benefit. Systolic "squeeze" assist, passive girdling effect, reversal of chronic chamber remodeling, and a reduction in systolic and diastolic wall stress were among such proposed mechanisms. Chen and associates demonstrated a significant reduction in systolic average transmural myocardial pressure using a fluidfilled balloon in an acute goat model of dynamic cardiomyoplasty. Techniques designed to measure intramuscular pressure in contracting muscle posed great practical challenges. Measurement of pressure within a fluid-filled balloon interposed between the myocardium and the latissimus dorsi flap eliminated this problem while permitting the direct calculation of transmural myocardial pressure. However, interpretation of their results is severely hampered by the use of untransformed latissimus dorsi muscle in a normal heart. It is a well-known fact that during fiber-type transformation, muscle loses not only its mass and power but also the speed of contraction [5]. A reduction in systolic transmural myocardial pressure and wall stress cannot be maintained if the contraction of the transformed muscle wrap is slower than that of the myocardium. This differs from the phenomenon of reduction in diastolic wall stress, which depends on an artificial ventricular hypertrophy created by the presence of the muscle wrap regardless of its contractile properties. We strongly believe therefore that the use of untransformed muscle in the setting of dynamic cardiomyoplasty © 1996 by The Society of Thoracic Surgeons Published by Elsevier Science Inc
research is unhelpful or even misleading. In particular, there is no place for the incorporation of untransformed muscle in an experimental design after a decade of clinical cardiomyoplasty employing only trained muscle. Further progress toward the understanding of its mechanism(s) of action can only be achieved with research that employs transformed latissimus dorsi muscle.
Augustine Tang, FRCSEd Timothy L. Hooper, MD
Baglan cad Orgen apt 18/3 16090 Cekirge, Bursa, Turkey
T e c h n i q u e for M e a s u r i n g a R e d u c t i o n in Pressure
321
Department of Cardiothoracic Surgery Regional Cardiothoracic Unit Wythenshawe Hospital Southmoor Rd Manchester M23 9LT United Kingdom
References 1. Chen FY, Aklog SML, deGuzman BJ, et al. New technique measures decreased transmural myocardial pressure in cardiomyoplasty. Ann Thorac Surg 1995;60:1678-82. 2. Kass DA, Baughman MD, Pak PH, et al. Reverse remodeling from cardiomyoplasty in human heart failure; external constraint versus active assist. Circulation 1995;91:2314-8. 3. Bellotti G, Moraes A, Bocchi E, et al. Late effects of cardiomyoplasty on left ventricular mechanics and diastolic filling. Circulation 1993;88(part 2):304-8. 4. El Oakley RM, Jarvis J. Cardiomyoplasty; a critical review of experimental and clinical results. Circulation 1994;90:2085-90. 5. Jarvis J. Power production and working capacity of rabbit tibialis anterior muscles after chronic electrical stimulation at 10 Hz. J Physiol 1993;470:157-69.
Reply To the Editor: We appreciate the comments of Drs Tang and Hooper and thank them. In summary, they question the interpretation of our results because untransformed latissimus dorsi muscle (LD) was applied to normal myocardium in an acute goat model of cardiomyoplasty. They believe strongly that the use of untransformed muscle in dynamic cardiomyoplasty (DCM) research is misleading and should not be used. We address their concerns. We are unclear regarding the statement that "a reduction in systolic transmural myocardial pressure and wall stress cannot be maintained if the contraction of the transformed muscle wrap is slower than that of the myocardium." If Tang and Hooper mean "contraction" to be velocity of shortening when the heart is wrapped with LD, we disagree. The velocity of LD shortening is always slower than that of the myocardium when the net systolic transmural myocardial pressure is reduced. In such a situation, the muscle wrap is intimately applied to the epicardium, and the rate of volume change inside the wrap is equivalent to the rate of volume change inside the heart. Assuming both the wrap and the myocardium to be spherical for simplicity, we may apply the formula for volume of a sphere: 4
v = ~rr 3
(1)
where V = volume of the sphere and r = radius of the sphere. The circumference of the sphere is given by C = 27rr
(2)
where C = the circumference. Substituting (2) into (1) and differentiating with respect to time yields the rate of change of 0003-4975/96/$15.00