Ann Thorac Surg 2000;69:625-628
© 2000 The Society of Thoracic Surgeons
Case Reports
Injection of vasodilators into arterial grafts through cardiac catheter to relieve spasm
Guo-Wei He, MD, PhDa,
Katherine Yue-Yan Fan, MRCPa,
Shui-Wah Chiu, FRCSa,
Wing-Hing Chow, FRCPa
a Division of Cardiothoracic Surgery, Department of Surgery and Cardiac Medical Unit, University of Hong Kong, Grantham Hospital, Hong Kong, China
Address reprint requests to Dr He, Division of Cardiothoracic Surgery, University of Hong Kong, Grantham Hospital, 125 Wong Chuk Hang Rd, Aberdeen, Hong Kong, China
e-mail: gwhe{at}hkucc.hku.hk
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Abstract
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Both native coronary artery and coronary bypass grafts may develop vasospasm after coronary artery bypass grafting. We recommend that whenever there is a high suspicion of vasospasm in arterial grafts and the native coronary artery unresponsive to or not suitable for usual vasodilator therapy, prompt selective graft arteriogram should be performed. Intraluminal injection of vasodilators such as calcium antagonists in combination with nitroglycerin may provide an effective antispastic therapy and this procedure could be lifesaving as demonstrated in the present report.
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Introduction
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Arterial grafts have been increasingly used for coronary artery bypass grafting. Recently at the University of Hong Kong, Grantham Hospital, the radial artery (RA) has become the preferred arterial graft, next to the internal thoracic artery (ITA).
According to our functional classification [1], the RA belongs to the type III arterial graft—a type of graft that is more spastic than type I arteries (somatic arteries, such as ITA and inferior epigastric artery [IEA]). Recently we have developed an antispastic protocol (University of Hong Kong protocol) for using the RA as an arterial graft [2, 3] and have performed more than 100 RA graftings and the incidence of occlusion and spasm is low (data to be reported). However, in abnormal situations such as when a large dose of inotropic agents is required, the arterial grafts and the native coronary artery may be in life-threatening spasm despite the intravenous infusion of nitroglycerin (NTG), as seen in the present report. We used intraluminal verapamil plus NTG injection through cardiac catheterization and successfully reversed the severe vasospasm. The patient’s life was saved.
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Case reports
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Patient 1
A 59-year-old man with a 10-year history of hypertension and insulin-independent diabetes mellitus presented with increasing exertional angina for 6 months. Coronary angiogram showed triple-vessel disease including diffusely diseased left anterior descending artery, right coronary artery, posterior descending artery, and left circumflex artery. Surgical revascularization was performed with left internal thoracic artery grafted to left anterior descending artery, RA to the intermediate artery, and saphenous vein graft to the posterior descending artery. His diabetes was not well controlled at admission. Insulin had to be given to treat the hyperglycemia at the second day after the admission. During the operation, a few doses of insulin were given intravenously to control his blood glucose level. Immediately after closure of sternotomy wound in the operating room, there were incessant repeated episodes of ventricular fibrillation requiring immediate resuscitation. This was later found to be due to hypokalemia (serum potassium, 2.6 mmol/L) that was obviously worsened by insulin infusion despite intravenous infusion of potassium. Intravenous injection followed by infusion of inotropic agents including dopamine, dobutamine, and adrenaline was necessary to support the hemodynamics. The patient was transferred to the Cardiac Catheterization Laboratory with repeated ventricular fibrillation during the transportation that was electrically defibrillated. Urgent angiogram was then performed to assess the patency of the grafts. There was severe vasospasm of the two arterial grafts and their respective anastomosed native coronary arteries (Fig 1). However, all anastomotic sites appeared patent. Intraluminal injection of verapamil and NTG into both ITA and RA was performed. After relief of the spasm (Fig 1B), an intraaortic balloon pump was inserted to support the hemodynamics.
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Fig 1. Selective graft (left internal thoracic artery graft anastomosed to the left anterior descending artery) angiography of patient 1. There was prominent spasm of the entire length of the graft and the native coronary artery (left anterior descending artery) (A). After injection of verapamil and nitroglycerin into the left internal thoracic artery graft, the flow in both graft and native coronary arteries is significantly improved (B).
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Patient 2
A 67-year-old man with 6 months’ history of exertional angina and coronary angiogram showed triple-vessel disease with left main stem disease as well. Coronary artery bypass grafting was performed with RA graft to the first obtuse marginal branch, left ITA to left anterior descending artery, and saphenous vein graft to right coronary artery and second obtuse marginal branch. Intravenous infusion of verapamil was incidentally omitted in this patient, although it is part of our routine protocol in management for RA grafting (University of Hong Kong protocol) [2]. However, the patient was on the usual low dose of NTG infusion. Twenty-four hours after the patient returned to the cardiac intensive care unit, he developed hypotension and raised pulmonary wedge pressure with a clinical picture compatible with cardiogenic shock, requiring positive inotropic agents and intraaortic balloon pump for circulatory support. He was transferred to the Cardiac Catheterization Laboratory. Coronary angiogram was performed, which showed diffuse arterial spasm of the left internal thoracic artery and RA (Fig 2A) grafts as well as the native coronary arteries. Intraluminal injection of verapamil and NTG was performed and the vasospasm in both arterial grafts and native coronary arteries was relieved (Fig 2B).
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Fig 2. Selective graft (radial artery graft anastomosed to first obtuse marginal branch) angiography of patient 2. There was vasospasm in both radial artery graft and native coronary arteries (A) and significantly improved flow after intraluminal injection of verapamil and nitroglycerin (B).
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In both cases, arterial access was achieved through right femoral artery. The left ITA and RA grafts were selected with 7F internal mammary catheter and 7F Judkins Right-4 catheter, respectively. Intraarterial bolus injections of 0.2 mg of verapamil and 0.2 mg of NTG, diluted in 2 mL of normal saline were alternatively and repeatedly administered in both patients. Subsequent repeated angiograms of the arterial grafts and native vessels revealed improved antegrade flow from arterial grafts into the native vessels and gradual resolution of arterial spasm. Intraaortic balloon pump was inserted through the left femoral artery in the patient (patient 1), whereas the second patient was already on circulatory support therapy. Neither patient suffered from ventricular arrhythmias or further cardiogenic shocks after injection of vasodilators. Both patients required only minimal amount of positive inotropic agents after the procedure and both were successfully weaned off the balloon pump within next 24 hours. Both patients recovered and were discharged from the hospital.
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Comment
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The 2 patients presented had severe vasospasm in arterial grafts as well as in native coronary arteries. In the first patient, the primary complication was ventricular arrhythmia that was due to hypokalemia. This was related to poorly controlled diabetes mellitus. The required insulin infusion induced intractable hypokalemia. Ventricular fibrillation developed and large dose of inotropic support was necessary after defibrillation to maintain cardiac output and this was the cause of the vasospasm. As recently demonstrated, both the ITA and RA are 
-adrenoceptor-predominant arteries with little ß-adrenoceptor function [4, 5] and therefore, the action of inotropic agents in the ITA and RA is mediated by -adrenoceptors that evoke a significant contraction rather than relaxation. Therefore, inotropic agents are potential spasmogens in arterial grafts. In patient 1, repeated direct intraluminal injection of vasodilators through the cardiac catheter immediately overcame the spasm. The arterial grafts and native coronary artery were visibly dilated. The condition of the patient was immediately improved. He then had an uneventful recovery on the cardiovascular system. The cause of vasospasm in arterial grafts in the second patient was less obvious. However, it was probably related to the omission of the use of calcium antagonists during the intraoperative period. We believe that systemic use of vasodilators (calcium antagonists) is an important procedure, although other investigators may no longer use it (C. Acar, personnel communication). The vasospasm in both ITA and RA in this patient was also immediately relieved by intraluminal injection of the two vasodilators.
The vasoreactivity is dose dependent. Usually, the plasma concentration of a vasodilator can only reach a moderately high level (free plasma concentrations of verapamil, nifedipine, and diltiazem have been measured at levels equivalent to -6.7, -7.7, and -7.2 log M [6]). The plasma concentration for NTG is -8.7 to 7.9 log M at an infusion rate of 37 to 175 µg/minute intravenously [7]. These concentrations are effective in vasorelaxation under usual situations [8]. However, vasospasm develops as an extremely strong contraction that causes zero flow. Under this situation, a very high dose of vasodilators is required for relief of the spasm. Such a high concentration is only reached by topical use of the drug. This can only be fulfilled in two conditions. First, during the harvesting of the graft, topical use of vasodilators such as verapamil + NTG (VG) solution may reach high concentration (-4.5 log M) as we prepared [2]. Second, intraluminal injection of the vasodilators in the arterial grafts as performed in the present report. As we reported, 0.2 mg of verapamil and 0.2 mg of NTG were repeatedly injected into the lumen of the RA and ITA, which immediately relieved the vasospasm in these two arterial grafts as well as the coronary artery spasm in both patients. Such high dose would never be achieved by the usual administration—the intravenous injection. In addition, the intraluminal injection with the mechanical force developed may add a dilating effect on the grafts and the coronary arteries.
We recommend that whenever there is a high suspicion of vasospasm in arterial grafts and the native coronary artery unresponsive to or not suitable for usual vasodilator therapy, prompt selective graft arteriogram should be performed. Intraluminal injection of vasodilators such as calcium antagonists in combination with NTG may provide an effective antispastic therapy and this procedure could be lifesaving as demonstrated in the present report.
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References
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He G.-W., Yang C.-Q. Comparison among arterial grafts and coronary artery. An attempt at functional classification. J Thorac Cardiovasc Surg 1995;109:707-715.[Abstract/Free Full Text]
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He G.-W. Verapamil plus nitroglycerin solution maximally preserves endothelial function of the radial artery. J Thorac Cardiovasc Surg 1998;115:1321-1327.[Abstract/Free Full Text]
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He G.-W., Yang C.-Q. Use of verapamil and nitroglycerin solution for preparation of radial artery for coronary bypass grafting. Ann Thorac Surg 1996;61:610-614.[Abstract/Free Full Text]
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He G.-W., Shaw J., Hughes C.F., et al. Predominant 1-adrenoceptor mediated contraction in the human internal mammary artery. J Cardiovasc Pharmacol 1993;21:256-263.[Medline]
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He G.-W., Yang C.-Q. Characteristics of adrenoceptors in the human radial artery. J Thorac Cardiovasc Surg 1998;115:1136-1141.[Abstract/Free Full Text]
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Henry P.D. Comparative pharmacology of calcium antagonists. Am J Cardiol 1980;46:1047-1058.[Medline]
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Wei J.Y., Reid P.R. Quantitative determination of trinitroglycerin in human plasma. Circulation 1979;59:588-592.[Abstract/Free Full Text]
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He G.-W., Yang C.-Q. Pharmacological studies and guidelines for the use of vasodilators for arterial grafts. In: He G.-W., ed. Arterial grafts for coronary artery bypass surgery. Singapore: Springer-Verlag, 1999:69-79.
Accepted for publication June 24, 1999.
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Abstract
Introduction
