Reduced Incidence of Intraoperative Myocardial Infarction During Coronary Bypass Surgery With Use of Intracoronary Shunt Technique ANDREW J. FRANZONE, MD EUGENE WALLSH, MD SIMON H. STERTZER, MD, FACC NICHOLAS P. DePASQUALE, MD, FACC MICHAEL S. BRUNO, MD
New York, New York
Intraoperative myocardial Infarction is a recognized complication of aortocoronary bypass surgery. One major cause of such Infarction m a y be interruption of coronary blood flow, particularly In patients with poor coronary collateral circulation. In 30 patients use of an intracoronary shunt made It possible to limit the period of coronary occlusion during graft construction to a few minutes. Use of this shunt was associated with a reduced Incidence of Intraoperative myocardial infarction (as judged b y the appearance of new Q waves) when these patients were compared with 50 patients operated on without this procedure (6 of 50 [12 percent] versus 0 of 30). The Incidence of postoperative persistent S-T segment elevation was reduced from 21 of 50 (42 percent) to 5 of 30 (17 percent). Except for use of the shunt, the surgical technique was identical in the two groups of patients.
Intraoperative myocardial infarction is a recognized complication o f aortocoronary saphenous vein bypass surgery. In addition to having l a t e effects on left ventricular performance, it contributes to i m m e d i a t e postoperative problems including arrhythmias, congestive heart failure and renal failure. Its mechanism is unknown but is not necessarily r e l a t e d to occlusion of the saphenous vein graft. 1 On the other hand, i n t e r r u p t i o n of coronary blood flow during construction of the graft p r o b a b l y c o n stitutes a major cause of intraoperative myocardial infarction. T o minimize such interruption, we used an intracoronary shunt t o maintain blood flow during construction of the bypass graft. This r e p o r t describes t h e shunt technique and compares the incidence of p o s t o p erative new Q waves in patients undergoing bypass surgery with a n d without use of the shunt. Material and Methods
From The Departmentsof Medicine and Surgery, Lenox Hill Hospital, New York, New York. Manuscript receivedApril 23, 1976; revisedmanuscript received November 16, 1976, accepted December 14, 1976. Address for reprints: Nicholas P. DePasquale, MD, LenoxHill Hospital, 100 East 77th Street, New York, New York 10021.
Patients: The shunt technique to be described was used in 30 consecutive patients undergoing aortocoronary saphenous vein bypass surgery. During t h e operation the standard limb leads were monitored and an epicardial electrocardiogram was recorded by means of a unipolar electrode sutured to the epicardial fat of the territory of the vessel to be grafted. A 12 lead electrocardiogram was recorded before operation and daily thereafter. The electrocardiograms were studied for the appearance of new Q waves and persistent S-T segment elevation. When both new Q waves and persistent S-T elevation were observed in the same patient the finding was categorized as a new Q wave. Persistent S-T elevation was defined as elevation equal to or greater than 1.5 mm in the standard limb leads or the precordial leads recorded to the left of the transition zone, or both, that persisted for at least 48 h o u r s postoperatively. The incidence of new Q waves and S-T elevation was compared with that in a series of 50 patients who underwent coronary bypass before introduction of the shunt technique. Except for the 'intracoronary shunt, t h e surgical technique was identical in both groups of patients. Shunt procedure: Surgery was performed using intermittent partial n o r mothermic cardiopulmonary bypass flow at a rate of 500 to 1,500 ml/min. Bypass flow was adjusted on the basis of a continuous display of left atrial pressure. A t
June 1977 The American Journal of CARDIOLOGY Volume39
1017
CORONARY BYPASS SURGERY WITH INTRACORONARY SHUNT TECHNIQUE~FRANZONE ET AL.
mold for suturing the saphenous vein graft to the coronary artery. The shunt was removed without clamping the artery immediately before tying the last few sutures between the artery and the graft. Results
Postoperative electrocardiographic
FIGURE 1. A series of Silastic shunts about 2 cm in length and of various calibers are prepared before surgery. A fine suture is tied around the shunt for ease of manipulation. Black bar indicates 2.0 cm.
operation all hearts were nonfibrillating and normothermic. The aortocoronary saphenous vein graft was constructed using a standard interrupted suture technique as previously described. 2 After exploration of the heart and confirmation of the angiographic findings, a site suitable for arteriotomy was selected. One of a series of previously prepared soft Silastic ® shunts of various calibers was selected for use according to the approximate inner diameter of the artery (Fig. 1). A fine suture placed around the shunt provided for ease of manipulation during insertion of the shunt and construction of the graft. The length of the shunt was determined by the size of the proposed arter]ommy. The shunt was tailored so that it was ot"sufficient length to extend both proximally and distally about 1 cm into the coronary artery. Immediately after arteriotomy, the shunt was introduced first proximally and then distally into the coronary artery. The suture around the shunt was centered in the arteriotomy. It was usually possible to install the shunt and reestablish coronary blood flow within 2 minutes of arteriotomy. A properly sized shunt provided excellent hemostasis. Traction on the tie around the shunt provided immobilization and exposure of the arterial wall for suturing. The shunt also served as a
SHUNT OPEN I~ ~l,'lllIHIfl.~ .
.
.
.
.
.
.
Characteristic sequential changes in the epicardial electrocardiogram during construction of a bypass graft to the left anterior descending coronary artery are shown in Figure 2. Before incision of the artery, the S-T segment was isoelectric (Fig. 2A). After incision of the artery and before the intracoronary shunt was inserted the S-T segment became elevated (Fig. 2B). Installation of the shunt with restoration of coronary blood flow was associated with an almost immediate return of the S-T segment to isoelectric level (Fig. 2C). After the shunt was inserted, S-T segment shifts could be reproduced by closing and opening the shunt with a clamp (Fig. 2D to 2F). Figure 3 shows the effect of closing the shunt on the epicardial electrocardiogram of a patient with three vessel coronary artery disease and a poor collateral circulation estimated angiographically. Clamp closure of the shunt was associated with progressive S-T segment elevation until the tracing
SHUNT OPEN
I1~~l~.t~ltltlllilili:j ~iliillllllllffltillllll~li~i!fllltll
SHUNT CLOSED ; 10sec ~ .
abnorm a l i t i e s : Six of 50 consecutive p a t i e n t s (12 p e r c e n t ) who u n d e r w e n t a o r t o c o r o n a r y s a p h e n o u s v e i n b y p a s s before use of the i n t r a c o r o n a r y s h u n t h a d electrocardiographic evidence of i n t r a o p e r a t i v e m y o c a r d i a l infarction manifested by the appearance of persistent new Q waves and 21 (42 percent) had persistent S - T segment elevation in postoperative electrocardiograms. None of the 30 consecutive patients undergoing c o r o n a r y bypass with the intracoronary s h u n t m a n i f e s t e d a n e w Q wave and only five (17 percent) h a d p e r s i s t e n t S - T s e g m e n t elevation. E p i c a r d i a l e l e c t r o c a r d i o g r a m : T h i s l e a d always displayed significant S - T ' s e g m e n t elevation a f t e r t h e a r t e r i o t o m y a n d before insertion of ~he i n t r a c o r o n a r y shunt. R e v e r s a l of the S - T elevation o c c u r r e d within seconds a f t e r insertion of the i n t r a c o r o n a r y s h u n t a n d restoration of coronary blood flow. C o r r e s p o n d i n g S - T elevation was not observed in t h e s t a n d a r d l i m b leads.
.
.
.
.
.
.
.
.
.
.
.
.
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.
.
.
.
.
.
.
.
.
.
• 3q-I~I-1 20S* c
..........
:-
" SHUNT CLOSED
i,i~hl ]~l/~[d, li" IL~,
SHUNT OPEN
I,t'l, t I I J-I.l I 1 I ] 1 lJl,,lt I.I I_111 I l l I I;1_
/~ i?:i~iii:ii'; i~:,:i~111:ii i: i~i, i)i;;~ii;~ii,::iii~ii~iii)?ii~2iiiiiii~i':ii]iiii,il,]iiiiil
FIGURE 2. Ep[cardial electrogram in a representative case. A, before incision of the left anterior descending coronary artery. The S-T segment is isoelectric. B, clamping and incision of the left anterior descending artery is associated with S-T segment elevation. C, after Insertion of the shunt, the S-T segment again becomes isoelectric D, the shunt has been inserted in the left anterior descending coronary artery and the S-T segment is isoelectric In the epicardlal electrocardiogram recorded from the territory of the artery. E, closure of the shunt with a clamp for several seconds Is associated with S-T elevation. F, release of the clamp results in almost immediate return of the S-T segment to the baseline. The simultaneously recorded standard limb leads failed to display S-T segment shift during any of these procedures
1018
June 1977
The American Journal of CARDIOLOGY
Volume 39
CORONARY BYPASS SURGERY WITH INTRACORONARY SHUNT TECHNIQUE~FRANZONE ET AL
achieved the appearance of a monophasic action potential. Release of the clamp was associated with junctional S-T depression and a marked increase in T wave amplitude compared with the control wave, thus suggesting residual suben~ docardial injury.
CONTROL iiiii~;iiiii~iii[i:: iii~iiiiiiiiiiiiiiiiiiiiiiiiiii~/~L,H~ • [ll;llrIT1fllllliTDllliU'JT1]/llJltq']]ULlD'nlllLl~11~urlmrdllf't~ I..'%1~.'.::1~':1:, 1
LAD I N C I S E D li::.l:-J. L ii!~':l:iI!:i,l"l~lr~lrl I,i I'J I,1 I~,l:l.:d I. B IIA I A~II~::IIAI ,l[~l|,h IL~:ili~ IE/~,:lP,l.il/~l llP,l.ll/~l
Discussion
Various types of catheter stents or graduated probes have been used during aortocoronary bypass surgery to simplify small vessel anastomoses, assure accuracy of suture placement and facilitate identification of nonstenotic vessel lumens. 3-'~ However, these stents or probes do not provide for maintenance of coronary blood flow during construction of the bypass graft. Effect on i n t r a o p e r a t i v e m y o c a r d i a l infarction: The electrocardiographic incidence of intraoperative myocardial infarction in eight reported series involving 863 patients was 18 percent, x,6-~2Using a combination of cardiac enzymatic and scintigraphic methods, Coleman et al. ~3 found a 16 percent incidence rate of intraoperative myocardial infarction. Before the intracoronary shunt was introduced at our institution, intraoperative myocardial infarction occurred in 12 percent of 50 consecutive patients undergoing aortocoronary bypass. By contrast, none of 30 consecutive patients undergoing aortocoronary bypass after introduction of the shunt had electrocardiographic evidence of intraoperative myocardial infarction. Although it was originally planned to use the intracoronary shunt on a random basis, the consistency of S-T segment elevation in the epicardial electrocardiogram and its immediate reversal when the shunt was opened made it difficult to justify surgery without use of the shunt. Therefore, the 30 consecutive patients operated on with use of the shunt were compared with the previous 50 patients operated on without use of the shunt. Because the two groups of patients were comparable with respect to surgical technique and severity of coronary artery disease, it is reasonable to attribute the absence Of electrocardiographic evidence of intraoperative myocardial infarction in the former group to maintenance of coronary blood flow during graft construction. Persistent S-T segment elevation was found in 42 percent of patients before and in 17 percent of patients after use of the shunt. Postoperative S-T elevation is usually attributed to pericarditis. However, the significant reduction in the incidence of postoperative S-T elevation suggests that such elevation may occasionally be due to myocardial injury. Role of h y p o t h e r m i a : Aortocoronary bypass in our series of patients was performed in the normothermic beating heart. In may be argued that maintenance of coronary blood flow during graft construction is unnecessary in the hypothermic heart. That hypothermia does no~ completely protect the myocardium is indicated by the fact that most of the studies documenting a high incidence rate of intraoperative myocardial infarction originated from centers in which aortocoronary bypass was performed in the hypothermic heart. It has been shown experimentally that reperfusion after a period of coronary occlusion may be associated with an
S H U N T IN PLACE
,~.1
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FIGURE 3. Eplcardiaf electrocardiogram in a patient with three vessel disease and poor collateral vessels. A, a functioning shunt is in place in the left anterior descending coronary artery (LAD) and the epicardial electrogram registered from the territory of the artery displays an isoelectric S-T segment. B, clamping of the shunt is associated with progressive S-T elevation. C, release of the clamp is associated with return of the S-T segment to the baseline, but the T waves are now tall and peaked compared with the cohtrol waves.
increase rather than a decrease in myocardial damage.Z4,15 Although the period of occlusion in experimental models is generally longer than that associated with coronary bypass surgery, it is possible that intraoperative myocardial damage is in some instances caused by alterations in the microvasculature during the period of occlusion. Epicardial versus limb lead electrocardiogram: The epicardial electrocardiogram always displayed S-T segment elevation during the brief period in which coronary blood flow was interrupted before installation of the shunt although corresponding S-T elevation was not evident in the simultaneously recorded standard limb leads. This discrepancy may have occurred because the chest was open and injury potentials were n o t propagated to the body surface. But it is more likely t h a t $-T elevation was the result of local injury potentials from a small area of myocardium corresponding to t h e territory of the grafted artery. This might explain why intraoperative myocardial infarction appears to be a more benign process than is the usual acute myocardial infarction. The absence of S-T segment alterations in the standard limb Ieads similar to those observed in the epicardial electrocardiogram suggests that the standard limb leads are inadequate for cardiac monitoring during aortocoronary bypass surgery. Implications: All patients undergoing aortocoronary bypass with use of the intracoronary shunt had relief o f angina pectoris. This finding suggests that in this series of patients relief of angina was due to improvement in coronary blood flow rather than to infarction of ischemie myocardium. As the technique of aortocoronary bypass surgery improves it is to be expected that the incidence of intraoperative myocardial infarction will decrease. T h e intracoronary shunt technique deserves further s t u d y to determine whether or not it will contribute to a reduction in the incidence of intraoperative myocardial infarction when other approaches to bypass surgery, particularly hypothermia, are utilized.
June 1977
The American Journal of CARDIOLOGY
Volume 39
1019
CoRONARY BYPASS SURGERY WITH INTRACORONARY SHUNT TECHNIQUE--FRANZONE ET AL.
References
1. Brewer DL, Bilbro RH, Barlel AG: Myocardial infarction as a complication of coronary bypass surgery. Circulation 47:58-64, 1973 2. Wallah E, Welnsteln G, Franzone AJ, et al: The use of distal right coronary artery endarterectomy and saphenous coronary bypass to decrease total grafts and extend operability In patients with coronary artery disease, in, Coronary Artery Medicine and Surgery. Concepts and Controversy(Norman JC, ed). EnglewoodCliffs, New Jersey, Appleton-Century-Crofts, 1975, p 590 3. Parsonnet B, Gilbert L, Glelchlnsky h Graduated probes for coronary bypass surgery. J Thorac Cardlovasc Surg 68:424-427, 1974 4. Grow JB, erantlgan CO: Use of a Fogarty biliary catheter to create a bloodless field for saphenousvein-coronary artery anastomosis. J Thorac Cardiovasc Surg 69:105-106, 1975 5. Ludlngton LG, Kafrounl G, Peterson MH, et ah Technique for using soft, flexible catheter stents in aortocoronary vein bypass operations. Ann Thorac Surg 21:328-332, 1976 6. Sheldon W, Favaloro R, Sones F, et al: Reconstructive coronary artery surgery: venous autograft technic. JAMA 213:78-82, 1970 7. Huitgen H, Mlyagawa M, Buck W, et al: Ischemic myocardial Injury during coronary artery surgery. Am Heart J 82:624-631, 1971 8. Dawson JT, Hall RJ, Garcla E, et ah Myocardial infarction after
1020
June 1977
The American Journal of CARDIOLOGY
9. 10. 11. 12. 13. 14. 15.
Volume 39
coronary artery bypass (CAB) surgery (abstr). Circulation 46:Suppl 11:11-144, 1972 Williams D, Iben A, Hurley E, et al: Myocardial infarction during coronary artery bypass surgery (abstr). Am J Cardlol 31:164, 1973 Kansal S, Roltman D, Sheffield T, et el: Acute myocardial Injury following aortocoronary bypass surgery (abstr). Am J Cardlol 31:140, 1973 Esplnoza J, Llpskl J, Lltwak R, et al: New Q waves after coronary artery bypass surgery for angina i~ectorls. Am J Cardiol 33: 221-224, 1974 Rose MR, Glassman E, Isom OW, el ah Electrocardiographic and serum enzyme changes of myocardial Infarction after coronary artery bypass surgery. Am J Cardlol 33:215-220, 1974 Coleman RE, Klein MS, Roberts R, el ah Enzymatic and sclntigraphic detection of myocardial infarction after cardiac surgery (abstr). Circulation 52:Supp111:11-171, 1975 Maroko PR, Glnks WR, Bloor CM, et ah Coronary artery reperfusion. 1. Early effects on local myocardial necrosis. J CIIn Invest 51:2717-2723, 1972 Bresnahan GF, Roberts R, Shell WE, et al: Deleterious effects due to hemorrhage after myocardial reperfusion. Am J Cardiol 33: 82-86, 1974
New York, New York
Intraoperative myocardial Infarction is a recognized complication of aortocoronary bypass surgery. One major cause of such Infarction m a y be interruption of coronary blood flow, particularly In patients with poor coronary collateral circulation. In 30 patients use of an intracoronary shunt made It possible to limit the period of coronary occlusion during graft construction to a few minutes. Use of this shunt was associated with a reduced Incidence of Intraoperative myocardial infarction (as judged b y the appearance of new Q waves) when these patients were compared with 50 patients operated on without this procedure (6 of 50 [12 percent] versus 0 of 30). The Incidence of postoperative persistent S-T segment elevation was reduced from 21 of 50 (42 percent) to 5 of 30 (17 percent). Except for use of the shunt, the surgical technique was identical in the two groups of patients.
Intraoperative myocardial infarction is a recognized complication o f aortocoronary saphenous vein bypass surgery. In addition to having l a t e effects on left ventricular performance, it contributes to i m m e d i a t e postoperative problems including arrhythmias, congestive heart failure and renal failure. Its mechanism is unknown but is not necessarily r e l a t e d to occlusion of the saphenous vein graft. 1 On the other hand, i n t e r r u p t i o n of coronary blood flow during construction of the graft p r o b a b l y c o n stitutes a major cause of intraoperative myocardial infarction. T o minimize such interruption, we used an intracoronary shunt t o maintain blood flow during construction of the bypass graft. This r e p o r t describes t h e shunt technique and compares the incidence of p o s t o p erative new Q waves in patients undergoing bypass surgery with a n d without use of the shunt. Material and Methods
From The Departmentsof Medicine and Surgery, Lenox Hill Hospital, New York, New York. Manuscript receivedApril 23, 1976; revisedmanuscript received November 16, 1976, accepted December 14, 1976. Address for reprints: Nicholas P. DePasquale, MD, LenoxHill Hospital, 100 East 77th Street, New York, New York 10021.
Patients: The shunt technique to be described was used in 30 consecutive patients undergoing aortocoronary saphenous vein bypass surgery. During t h e operation the standard limb leads were monitored and an epicardial electrocardiogram was recorded by means of a unipolar electrode sutured to the epicardial fat of the territory of the vessel to be grafted. A 12 lead electrocardiogram was recorded before operation and daily thereafter. The electrocardiograms were studied for the appearance of new Q waves and persistent S-T segment elevation. When both new Q waves and persistent S-T elevation were observed in the same patient the finding was categorized as a new Q wave. Persistent S-T elevation was defined as elevation equal to or greater than 1.5 mm in the standard limb leads or the precordial leads recorded to the left of the transition zone, or both, that persisted for at least 48 h o u r s postoperatively. The incidence of new Q waves and S-T elevation was compared with that in a series of 50 patients who underwent coronary bypass before introduction of the shunt technique. Except for the 'intracoronary shunt, t h e surgical technique was identical in both groups of patients. Shunt procedure: Surgery was performed using intermittent partial n o r mothermic cardiopulmonary bypass flow at a rate of 500 to 1,500 ml/min. Bypass flow was adjusted on the basis of a continuous display of left atrial pressure. A t
June 1977 The American Journal of CARDIOLOGY Volume39
1017
CORONARY BYPASS SURGERY WITH INTRACORONARY SHUNT TECHNIQUE~FRANZONE ET AL.
mold for suturing the saphenous vein graft to the coronary artery. The shunt was removed without clamping the artery immediately before tying the last few sutures between the artery and the graft. Results
Postoperative electrocardiographic
FIGURE 1. A series of Silastic shunts about 2 cm in length and of various calibers are prepared before surgery. A fine suture is tied around the shunt for ease of manipulation. Black bar indicates 2.0 cm.
operation all hearts were nonfibrillating and normothermic. The aortocoronary saphenous vein graft was constructed using a standard interrupted suture technique as previously described. 2 After exploration of the heart and confirmation of the angiographic findings, a site suitable for arteriotomy was selected. One of a series of previously prepared soft Silastic ® shunts of various calibers was selected for use according to the approximate inner diameter of the artery (Fig. 1). A fine suture placed around the shunt provided for ease of manipulation during insertion of the shunt and construction of the graft. The length of the shunt was determined by the size of the proposed arter]ommy. The shunt was tailored so that it was ot"sufficient length to extend both proximally and distally about 1 cm into the coronary artery. Immediately after arteriotomy, the shunt was introduced first proximally and then distally into the coronary artery. The suture around the shunt was centered in the arteriotomy. It was usually possible to install the shunt and reestablish coronary blood flow within 2 minutes of arteriotomy. A properly sized shunt provided excellent hemostasis. Traction on the tie around the shunt provided immobilization and exposure of the arterial wall for suturing. The shunt also served as a
SHUNT OPEN I~ ~l,'lllIHIfl.~ .
.
.
.
.
.
.
Characteristic sequential changes in the epicardial electrocardiogram during construction of a bypass graft to the left anterior descending coronary artery are shown in Figure 2. Before incision of the artery, the S-T segment was isoelectric (Fig. 2A). After incision of the artery and before the intracoronary shunt was inserted the S-T segment became elevated (Fig. 2B). Installation of the shunt with restoration of coronary blood flow was associated with an almost immediate return of the S-T segment to isoelectric level (Fig. 2C). After the shunt was inserted, S-T segment shifts could be reproduced by closing and opening the shunt with a clamp (Fig. 2D to 2F). Figure 3 shows the effect of closing the shunt on the epicardial electrocardiogram of a patient with three vessel coronary artery disease and a poor collateral circulation estimated angiographically. Clamp closure of the shunt was associated with progressive S-T segment elevation until the tracing
SHUNT OPEN
I1~~l~.t~ltltlllilili:j ~iliillllllllffltillllll~li~i!fllltll
SHUNT CLOSED ; 10sec ~ .
abnorm a l i t i e s : Six of 50 consecutive p a t i e n t s (12 p e r c e n t ) who u n d e r w e n t a o r t o c o r o n a r y s a p h e n o u s v e i n b y p a s s before use of the i n t r a c o r o n a r y s h u n t h a d electrocardiographic evidence of i n t r a o p e r a t i v e m y o c a r d i a l infarction manifested by the appearance of persistent new Q waves and 21 (42 percent) had persistent S - T segment elevation in postoperative electrocardiograms. None of the 30 consecutive patients undergoing c o r o n a r y bypass with the intracoronary s h u n t m a n i f e s t e d a n e w Q wave and only five (17 percent) h a d p e r s i s t e n t S - T s e g m e n t elevation. E p i c a r d i a l e l e c t r o c a r d i o g r a m : T h i s l e a d always displayed significant S - T ' s e g m e n t elevation a f t e r t h e a r t e r i o t o m y a n d before insertion of ~he i n t r a c o r o n a r y shunt. R e v e r s a l of the S - T elevation o c c u r r e d within seconds a f t e r insertion of the i n t r a c o r o n a r y s h u n t a n d restoration of coronary blood flow. C o r r e s p o n d i n g S - T elevation was not observed in t h e s t a n d a r d l i m b leads.
.
.
.
.
.
.
.
.
.
.
.
.
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.
.
.
.
.
.
.
.
.
.
• 3q-I~I-1 20S* c
..........
:-
" SHUNT CLOSED
i,i~hl ]~l/~[d, li" IL~,
SHUNT OPEN
I,t'l, t I I J-I.l I 1 I ] 1 lJl,,lt I.I I_111 I l l I I;1_
/~ i?:i~iii:ii'; i~:,:i~111:ii i: i~i, i)i;;~ii;~ii,::iii~ii~iii)?ii~2iiiiiii~i':ii]iiii,il,]iiiiil
FIGURE 2. Ep[cardial electrogram in a representative case. A, before incision of the left anterior descending coronary artery. The S-T segment is isoelectric. B, clamping and incision of the left anterior descending artery is associated with S-T segment elevation. C, after Insertion of the shunt, the S-T segment again becomes isoelectric D, the shunt has been inserted in the left anterior descending coronary artery and the S-T segment is isoelectric In the epicardlal electrocardiogram recorded from the territory of the artery. E, closure of the shunt with a clamp for several seconds Is associated with S-T elevation. F, release of the clamp results in almost immediate return of the S-T segment to the baseline. The simultaneously recorded standard limb leads failed to display S-T segment shift during any of these procedures
1018
June 1977
The American Journal of CARDIOLOGY
Volume 39
CORONARY BYPASS SURGERY WITH INTRACORONARY SHUNT TECHNIQUE~FRANZONE ET AL
achieved the appearance of a monophasic action potential. Release of the clamp was associated with junctional S-T depression and a marked increase in T wave amplitude compared with the control wave, thus suggesting residual suben~ docardial injury.
CONTROL iiiii~;iiiii~iii[i:: iii~iiiiiiiiiiiiiiiiiiiiiiiiiii~/~L,H~ • [ll;llrIT1fllllliTDllliU'JT1]/llJltq']]ULlD'nlllLl~11~urlmrdllf't~ I..'%1~.'.::1~':1:, 1
LAD I N C I S E D li::.l:-J. L ii!~':l:iI!:i,l"l~lr~lrl I,i I'J I,1 I~,l:l.:d I. B IIA I A~II~::IIAI ,l[~l|,h IL~:ili~ IE/~,:lP,l.il/~l llP,l.ll/~l
Discussion
Various types of catheter stents or graduated probes have been used during aortocoronary bypass surgery to simplify small vessel anastomoses, assure accuracy of suture placement and facilitate identification of nonstenotic vessel lumens. 3-'~ However, these stents or probes do not provide for maintenance of coronary blood flow during construction of the bypass graft. Effect on i n t r a o p e r a t i v e m y o c a r d i a l infarction: The electrocardiographic incidence of intraoperative myocardial infarction in eight reported series involving 863 patients was 18 percent, x,6-~2Using a combination of cardiac enzymatic and scintigraphic methods, Coleman et al. ~3 found a 16 percent incidence rate of intraoperative myocardial infarction. Before the intracoronary shunt was introduced at our institution, intraoperative myocardial infarction occurred in 12 percent of 50 consecutive patients undergoing aortocoronary bypass. By contrast, none of 30 consecutive patients undergoing aortocoronary bypass after introduction of the shunt had electrocardiographic evidence of intraoperative myocardial infarction. Although it was originally planned to use the intracoronary shunt on a random basis, the consistency of S-T segment elevation in the epicardial electrocardiogram and its immediate reversal when the shunt was opened made it difficult to justify surgery without use of the shunt. Therefore, the 30 consecutive patients operated on with use of the shunt were compared with the previous 50 patients operated on without use of the shunt. Because the two groups of patients were comparable with respect to surgical technique and severity of coronary artery disease, it is reasonable to attribute the absence Of electrocardiographic evidence of intraoperative myocardial infarction in the former group to maintenance of coronary blood flow during graft construction. Persistent S-T segment elevation was found in 42 percent of patients before and in 17 percent of patients after use of the shunt. Postoperative S-T elevation is usually attributed to pericarditis. However, the significant reduction in the incidence of postoperative S-T elevation suggests that such elevation may occasionally be due to myocardial injury. Role of h y p o t h e r m i a : Aortocoronary bypass in our series of patients was performed in the normothermic beating heart. In may be argued that maintenance of coronary blood flow during graft construction is unnecessary in the hypothermic heart. That hypothermia does no~ completely protect the myocardium is indicated by the fact that most of the studies documenting a high incidence rate of intraoperative myocardial infarction originated from centers in which aortocoronary bypass was performed in the hypothermic heart. It has been shown experimentally that reperfusion after a period of coronary occlusion may be associated with an
S H U N T IN PLACE
,~.1
.e
[II
L I I I J
I.I
' "
,111hl
I
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~-~ T
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T
FIGURE 3. Eplcardiaf electrocardiogram in a patient with three vessel disease and poor collateral vessels. A, a functioning shunt is in place in the left anterior descending coronary artery (LAD) and the epicardial electrogram registered from the territory of the artery displays an isoelectric S-T segment. B, clamping of the shunt is associated with progressive S-T elevation. C, release of the clamp is associated with return of the S-T segment to the baseline, but the T waves are now tall and peaked compared with the cohtrol waves.
increase rather than a decrease in myocardial damage.Z4,15 Although the period of occlusion in experimental models is generally longer than that associated with coronary bypass surgery, it is possible that intraoperative myocardial damage is in some instances caused by alterations in the microvasculature during the period of occlusion. Epicardial versus limb lead electrocardiogram: The epicardial electrocardiogram always displayed S-T segment elevation during the brief period in which coronary blood flow was interrupted before installation of the shunt although corresponding S-T elevation was not evident in the simultaneously recorded standard limb leads. This discrepancy may have occurred because the chest was open and injury potentials were n o t propagated to the body surface. But it is more likely t h a t $-T elevation was the result of local injury potentials from a small area of myocardium corresponding to t h e territory of the grafted artery. This might explain why intraoperative myocardial infarction appears to be a more benign process than is the usual acute myocardial infarction. The absence of S-T segment alterations in the standard limb Ieads similar to those observed in the epicardial electrocardiogram suggests that the standard limb leads are inadequate for cardiac monitoring during aortocoronary bypass surgery. Implications: All patients undergoing aortocoronary bypass with use of the intracoronary shunt had relief o f angina pectoris. This finding suggests that in this series of patients relief of angina was due to improvement in coronary blood flow rather than to infarction of ischemie myocardium. As the technique of aortocoronary bypass surgery improves it is to be expected that the incidence of intraoperative myocardial infarction will decrease. T h e intracoronary shunt technique deserves further s t u d y to determine whether or not it will contribute to a reduction in the incidence of intraoperative myocardial infarction when other approaches to bypass surgery, particularly hypothermia, are utilized.
June 1977
The American Journal of CARDIOLOGY
Volume 39
1019
CoRONARY BYPASS SURGERY WITH INTRACORONARY SHUNT TECHNIQUE--FRANZONE ET AL.
References
1. Brewer DL, Bilbro RH, Barlel AG: Myocardial infarction as a complication of coronary bypass surgery. Circulation 47:58-64, 1973 2. Wallah E, Welnsteln G, Franzone AJ, et al: The use of distal right coronary artery endarterectomy and saphenous coronary bypass to decrease total grafts and extend operability In patients with coronary artery disease, in, Coronary Artery Medicine and Surgery. Concepts and Controversy(Norman JC, ed). EnglewoodCliffs, New Jersey, Appleton-Century-Crofts, 1975, p 590 3. Parsonnet B, Gilbert L, Glelchlnsky h Graduated probes for coronary bypass surgery. J Thorac Cardlovasc Surg 68:424-427, 1974 4. Grow JB, erantlgan CO: Use of a Fogarty biliary catheter to create a bloodless field for saphenousvein-coronary artery anastomosis. J Thorac Cardiovasc Surg 69:105-106, 1975 5. Ludlngton LG, Kafrounl G, Peterson MH, et ah Technique for using soft, flexible catheter stents in aortocoronary vein bypass operations. Ann Thorac Surg 21:328-332, 1976 6. Sheldon W, Favaloro R, Sones F, et al: Reconstructive coronary artery surgery: venous autograft technic. JAMA 213:78-82, 1970 7. Huitgen H, Mlyagawa M, Buck W, et al: Ischemic myocardial Injury during coronary artery surgery. Am Heart J 82:624-631, 1971 8. Dawson JT, Hall RJ, Garcla E, et ah Myocardial infarction after
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9. 10. 11. 12. 13. 14. 15.
Volume 39
coronary artery bypass (CAB) surgery (abstr). Circulation 46:Suppl 11:11-144, 1972 Williams D, Iben A, Hurley E, et al: Myocardial infarction during coronary artery bypass surgery (abstr). Am J Cardlol 31:164, 1973 Kansal S, Roltman D, Sheffield T, et el: Acute myocardial Injury following aortocoronary bypass surgery (abstr). Am J Cardlol 31:140, 1973 Esplnoza J, Llpskl J, Lltwak R, et al: New Q waves after coronary artery bypass surgery for angina i~ectorls. Am J Cardiol 33: 221-224, 1974 Rose MR, Glassman E, Isom OW, el ah Electrocardiographic and serum enzyme changes of myocardial Infarction after coronary artery bypass surgery. Am J Cardlol 33:215-220, 1974 Coleman RE, Klein MS, Roberts R, el ah Enzymatic and sclntigraphic detection of myocardial infarction after cardiac surgery (abstr). Circulation 52:Supp111:11-171, 1975 Maroko PR, Glnks WR, Bloor CM, et ah Coronary artery reperfusion. 1. Early effects on local myocardial necrosis. J CIIn Invest 51:2717-2723, 1972 Bresnahan GF, Roberts R, Shell WE, et al: Deleterious effects due to hemorrhage after myocardial reperfusion. Am J Cardiol 33: 82-86, 1974
