Biomedical subjects

G W He

Publications and source records attributed to G W He.

At least 73 records · Page 4Linked to original sources

PubMed1995

Overview of the nature of vasoconstriction in arterial grafts for coronary operations.

Many vasoconstrictors (spasmogens) may cause arterial graft spasm; however, there is lack of an overview of the nature of vasoconstriction in grafts. This study was designed to investigate the response of three major arterial grafts currently used for coronary artery bypass grafting to various vasoconstrictor substances. Segments of three arterial grafts (gastroepiploic [GEA], n = 28; internal mammary [IMA], n = 213; inferior epigastric [IEA], n = 24) taken from patients undergoing coronary artery bypass grafting were studied in organ baths under a physiologic pressure. Cumulative concentration-contraction curves were established for the following vasoconstrictor substances: endothelin-1, U46619, prostaglandin F2 alpha, norepinephrine, methoxamine, phenylephrine, 5-hydroxytryptamine, and potassium chloride (K+). In IMA, the highest contraction force was induced by U46619 (5.69 +/- 0.48 g), endothelin-1 (4.43 +/- 0.4 g), PGF2 alpha (6.29 +/- 1.42 g), and K+ (4.58 +/- 0.5 g). Internal mammary artery is highly sensitive to endothelin-1 (EC50, -8.13 +/- 0.08 log M) and U46619 (EC50, -8.21 +/- 0.21 log M) (lower than any other vasoconstrictors, p < 0.001). Next sensitive vasoconstrictors were PGF2 alpha and norepinephrine. 5-Hydroxytryptamine induced significantly higher contraction force in the IMA without endothelium (2.8 +/- 0.64 g versus 1.4 +/- 0.23 g, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1995

Up to thirty-year survival after aortic valve replacement in the small aortic root.

Aortic valve replacement (AVR) in the small aortic root has been reported to be associated with obstruction of left ventricular output. This study was designed to investigate the determinants of long-term survival after the implantation of small size prostheses. From September 1961 to December 1993, 2,977 patients underwent isolated aortic valve replacement at our institution. Of these patients, 447 who were older than 18 years received small size (21 mm or less) prostheses. Long-term survival was investigated in the 404 patients who survived operation (more than 30 days) with 92% follow-up completeness (mean +/- deviation 7.1 +/- 6.4; maximum, 31 years). The age was younger than 50 years in 62 patients, 50 to 59 years in 60, 60 to 69 years in 99, 70 to 79 years in 138, and 80 to 94 years in 45; 67% were men. Thirty patients (7%) had previous AVR. Prosthesis usage included early Starr-Edwards models in 130 (32%), current Starr-Edwards (model 1260 since 1969) in 50 (12%), Carpentier-Edwards (porcine) in 113 (28%), and other prostheses in 111 patients (27%). One hundred sixteen patients (26%) had concomitant coronary artery bypass grafting (CABG). Eleven variables (age divided as above, sex, preoperative functional class, body surface area [BSA], small BSA [less than 1.6, 1.7, 1.8, or 1.9 m2], period of operation, previous AVR, type of prosthesis, size of prosthesis, concomitant CABG, and re-replacement) were investigated with regard to the long-term survival by the Kaplan-Meier method, and age, concomitant CABG, and type of prosthesis were significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1995

Determinants of operative mortality in reoperative coronary artery bypass grafting.

Previously suggested risk factors for operative mortality in reoperative coronary artery bypass grafting are contradictory. Therefore, we analyzed our data of 622 patients who underwent reoperative bypass grafting from January 1986 through June 1993. Among these patients, 258 had saphenous vein grafts alone and 364 had internal mammary artery grafting, including unilateral (342 patients) and bilateral (22 patients) mammary artery grafting with or without additional saphenous vein grafting. Overall operative mortality was 11.4% for reoperation compared with only 3.6% for primary bypass grafting during the same time frame. To determine risk factors for mortality and the influence of internal mammary artery grafting on the outcome, we analyzed 82 variables (31 preoperative, 17 intraoperative, and 34 postoperative) by univariate analysis. Significant variables or the variables having a trend (p < 0.2) to be associated with the mortality were included in stepwise multiple logistic regression analyses. Two regression analyses were separately performed. Regression 1 only included preoperative and intraoperative variables whereas regression 2 included postoperative variables as well. The logistic regressions demonstrate that preoperative variables (low ejection fraction [p = 0.0002], old age [p = 0.003], female gender [p = 0.011], and history of arrhythmia [p = 0.023]), intraoperative variables (emergency operation [p = 0.0001] and long perfusion time [p = 0.0001]), and postoperative variables (complications) are independently associated with higher mortality. Unlike previously described results, aortic crossclamp time, route of cardioplegia, use of internal mammary artery, number of grafts, and year of operation are not associated with operative mortality. The identification of these risk factors may have important implications in further improvement of the results of reoperative coronary artery bypass grafting.

Cause of Death↗

PubMed1995

Comparison among arterial grafts and coronary artery. An attempt at functional classification.

Various arterial conduits have been used for coronary artery bypass grafting. However, arterial grafts are not uniform either in anatomy or in function. Some conduits are more spastic than others and there may be possible differences in long-term patency rates. The diverse biologic characteristics promote a necessity of classification of arterial grafts, which may facilitate the understanding of surgeons of biologic characteristics of various arterial grafts and provide a scientific basis for searching for new grafts. Another important issue is the comparison of reactivity between arterial grafts and coronary arteries. In this study, we aim to compare the pharmacologic reactivity among the human arteries (grafts and coronary arteries) and to classify arterial grafts. Segments of three arterial grafts (gastroepiploic, internal mammary, and inferior epigastric) taken from patients undergoing coronary artery bypass grafting and coronary arteries taken from explanted hearts were studied in organ baths for the contraction to four vasoconstrictors (endothelin-1, thromboxane A2 mimetic U46619, full adrenoceptor agonist norepinephrine, and depolarizing agent potassium) under physiologic pressure. The diameter of the four arteries at a pressure of 100 mm Hg was similar (p > 0.05). However, the gastroepiploic artery contracted to higher forces (9.41 +/- 2.0 gm for endothelin, 11.79 +/- 1.85 gm for U46619, 13.54 +/- 2.7 gm for norepinephrine, and 11.11 +/- 1.97 gm for potassium) than did the coronary artery and internal mammary artery (p < 0.05) for all the tested vasoconstrictors and higher than the inferior epigastric artery for potassium and norepinephrine (p < 0.05). There was no significant difference among the other three arteries (internal mammary artery, inferior epigastric artery, and coronary artery) regarding the maximal contraction force to any vasoconstrictor. No difference was detected in regard to the sensitivity (effective concentration causing 50% of the maximal response) to the vasoconstrictors among the four arteries. This study reveals that among the arterial grafts and the coronary artery, the gastroepiploic artery has the highest contractility to various vasoconstrictors. On the basis of our findings and physiologic and embryologic knowledge we propose a classification for arterial grafts: type I (somatic arteries), type II (splanchnic arteries), and type III (limb arteries). Types II and III are prone to spasm because of higher contractility whereas type I arteries are usually less spastic. This classification may have important clinical implications for the understanding of arterial graft spasm or patency and may be useful in the search for new grafts.

Arteries↗

PubMed1995

Functional comparison between the human inferior epigastric artery and internal mammary artery. Similarities and differences.

Although the inferior epigastric artery has been used as an alternative arterial graft for coronary artery bypass grafting, little is known about the contractile and relaxation characteristics of this artery. This study was designed to compare the pharmacologic reactivity of the two arterial conduits--the inferior epigastric artery and the internal mammary artery. Forty-one inferior epigastric artery ring segments from eight patients undergoing coronary grafting and 62 internal mammary artery ring segments were set up in organ baths under physiologic pressure. The contractility was determined from the contraction induced by the depolarizing agent potassium and receptor-mediated vasoconstrictor agents, norepinephrine, U46619, and endothelin-1. Endothelium-dependent relaxation was induced by the calcium ionophore A23187, a non-receptor agonist for endothelium-derived relaxing factor, and acetylcholine, a receptor agonist for endothelium-derived relaxing factor. Glyceryl trinitrate was used to study endothelium-independent relaxation. The maximal response (either contraction or relaxation) and the effective concentration causing 50% of the maximal response for these two arteries were compared. There was no difference (p > 0.05) either in the maximal contraction force (5.30 +/- 0.87 versus 4.76 +/- 0.89 gm for potassium, 5.13 +/- 0.67 versus 4.47 +/- 1.15 gm for norepinephrine, 8.04 +/- 1.23 versus 6.23 +/- 0.99 gm for U46619, and 4.88 +/- 0.69 versus 5.57 +/- 0.93 for endothelin-1 (n = 6 to 10 for each vasoconstrictor) or in the maximal relaxation induced by glyceryl trinitrate (86.46% versus 92.98%, n = 6) or by acetylcholine (20.72% versus 45.51%, n = 5) between the inferior epigastric artery and internal mammary artery. The effective concentration causing half maximal response to all vasoconstrictors and vasodilators was similar between the two arteries (p > 0.05). However, A23187 induced significantly less relaxation in the inferior epigastric artery (38.42 +/- 15.49%, n = 6) than in the internal mammary artery (71.89 +/- 7.17%, n = 9, p < 0.05). We conclude that contractility, endothelium-independent relaxation, and receptor-mediated endothelium-dependent relaxation are similar in the inferior epigastric artery and the internal mammary artery. However, the endothelium of this arterial graft has less ability to respond to the non-receptor-mediated endothelium-derived relaxing factor stimulant. The influence of this difference on the prevalence of atherosclerosis and long-term patency rate in the inferior epigastric artery remains to be studied.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1995

Effect of thromboxane A2 antagonist GR32191B on prostanoid and nonprostanoid receptors in the human internal mammary artery.

Arterial grafts have been demonstrated to be very effective for coronary artery bypass surgery. Thromboxane A2 (TXA2) is a potent vasoconstrictor for arterial grafts. To determine whether the specific TXA2 (TP) receptor antagonist GR32191B is effective in inhibition of prostanoid or nonprostanoid receptors, we studied the effect of GR32191B in human internal mammary artery (IMA) segments, taken from coronary bypass patients, in organ chambers. In IMA precontracted with U46619 (10 nM, n = 7), prostaglandin F2 alpha (PGF2 alpha 1 microM, n = 7), or potassium chloride (K+ 25 microM, n = 6). GR32191B induced 100.0 +/- 0, 97.86 +/- 2.14, or 45.87 +/- 7.63% relaxation. In other experiments, one IMA ring taken from each patient was used as a control and others from the same patient were allocated to other groups treated with different concentrations of GR32191B [3-300 nM for U46619, 30 nM-3 microM for PGF2 alpha, 300 nM-100 microM for K+, 3 microM norepinephrine (NE), and 3 microM for 5-hydroxytryptamine (5-HT)] for 1 h before concentration-contraction curves to these vasoconstrictors (expressed as percentage of K(+)-induced contraction force) were established. Treatment with GR32191B (300 nM) significantly decreased the contraction induced by U46619 (from 306.4 +/- 22.1 to 61.9 +/- 24.9%, p < 0.01) and that induced by PGF2 alpha (from 208.2 +/- 13.5 to 1.4 +/- 1.4%, p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1994

Risk factors for operative mortality in elderly patients undergoing internal mammary artery grafting.

From January 1986 through June 1992, 512 elderly patients (70 years and older) underwent internal mammary artery grafting (IMAG). The operative mortality in these patients was 7.62% (39 of 512), which was significantly higher than that (1.97% [60 of 3,047]; p < 0.0001) in younger patients (under 70 years old). To investigate the risk factors in the elderly, the data from the 512 patients were evaluated by univariate analysis and multiple logistic regression. Of 53 variables analyzed, nine preoperative variables (age, smoking history, congestive heart failure, myocardial infarction, New York Heart Association functional class, ejection fraction, left main artery disease, stenosis of the left anterior descending artery, and reoperation), three intraoperative variables (emergency operation, bilateral IMAG, and right IMAG), and nine postoperative variables were significantly associated with the higher mortality (p < 0.05). In particular, the operative mortality was significantly higher in the patients undergoing right IMAG (21.62% [8 of 37]) than that in patients only undergoing left IMAG (6.53% [31 of 475]; p < 0.004). The significant preoperative and intraoperative variables and the variables that have a tendency for correlation (p < 0.2) to mortality were included in a stepwise multiple logistic regression. The regression analysis demonstrated that right IMAG, reoperation, history of myocardial infarction, age, left main artery disease, history of smoking, and postoperative complications are the risk factors for the elderly undergoing IMAG. Therefore, particular care should be taken in those patients scheduled to undergo IMAG. The role of right IMAG in the elderly should be further clarified before universal acceptance of the technique in these patients.

Age Factors↗

PubMed1994

Tolerance of epicardial coronary endothelium and smooth muscle to hyperkalemia.

Results of previous studies have suggested that high K+ concentrations in cardioplegic solutions may be detrimental to coronary endothelium in perfused hearts, as determined from changes in the coronary flow rate, but the direct functional changes in endothelium secondary to hyperkalemia have not been fully studied. To determine the effect of the K+ concentration in a physiologic solution (Krebs') and in St. Thomas' cardioplegic solution, and the effect of exposure time on endothelium and smooth muscle, porcine coronary artery rings were set up in organ baths under a physiologic pressure. The effect of exposure to Krebs' solution containing 5.9 or 50 mmol/L K+ or to St. Thomas' solution containing 16 or 50 mmol/L K+, for either 2 hours (group I) or 4 hours (group II), was examined. The solutions were continuously aerated with 95% oxygen and 5% carbon dioxide to exclude the effects of ischemia and hypoxia. The rings were then washed and contracted with K+ (25 mmol/L). The ability to release endothelium-derived relaxing factor (EDRF) in response to an EDRF stimulus (substance P) was used as an index of endothelial function. Smooth muscle function was evaluated in terms of the K(+)-induced contraction force and the relaxation induced with glyceryl trinitrate, in addition to the maximal substance P-induced relaxation. The maximal relaxation induced by substance P did not decrease by incubation with 50 mmol/L K+ in any group (p > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Aortic valve replacement: determinants of operative mortality.

Contradictory results have been reported regarding risk factors for aortic valve replacement (AVR). This study was designed to investigate determinants of operative mortality for AVR with emphasis on concomitant coronary artery bypass grafting (CABG) and old age. Between January 1986 and June 1992, 371 patients with a mean age of 61.99 +/- 0.76 years underwent AVR. There were 256 men (69.0%) and 115 women (31.0%). Twenty-six patients (7.0%) were 80 years old or older, and 97 (26.1%) were between 70 and 80 years old. Of these patients, 210 (56.6%) had isolated AVR, 142 (38.3%) had concomitant CABG, and 31 (8.4%) had concomitant mitral valve operations. Twenty patients (5.4%) underwent emergency operation. There were 33 operative deaths (8.9%). Univariate analysis and stepwise multiple logistic regression analysis were used to determine the risk factors for operative mortality. In the univariate analysis, 13 preoperative variables (sex, age, history of congestive heart failure, myocardial infarction, arrhythmia, functional class, class I/II versus III/IV, four variables related to aortic valve pathology, ejection fraction, left ventricular function) and 20 perioperative variables (emergency operation, individual surgeon, myocardial protection by type and route of cardioplegia, type of prosthesis, size of prosthesis, mean size by survival, small versus large size, concomitant procedure, concomitant CABG (versus others or AVR alone), concomitant mitral valve operation (versus others or AVR alone), concomitant CABG and MV operation, aortic cross-clamp time, cardiopulmonary bypass time, use and time of insertion of intraaortic balloon pump, low cardiac output, postoperative complications) were examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed1994

Greater contractility of internal mammary artery bifurcation: possible cause of low patency rates.

Coronary artery bypass grafting using bifurcation of the internal mammary artery (IMA) has been reported to have a poor patency rate. To test the hypothesis that the contractility (tendency for spasm) is greater at the bifurcation than at the main IMA, segments of the bifurcation and the distal section of IMA taken from patients with coronary artery bypass grafts were studied in organ baths. The IMA rings were set up at a physiologic pressure. Concentration-response curves were established for norepinephrine, endothelin-1, U46619, potassium, and glyceryl trinitrate (precontracted with 10 nmol/L U46619). Contraction forces were standardized (gram per mm circumference) at a pressure of 100 mm Hg. The diameter was 1.50 +/- 0.08 mm (n = 38) for the bifurcation and 2.03 +/- 0.07 (n = 42) for the main IMA (p < 0.0001). The standardized contraction force was greater in the bifurcation than in the main IMA for norepinephrine (0.82 +/- 0.06 versus 0.54 +/- 0.1; p = 0.02) and endothelin-1 (1.07 +/- 0.11 versus 0.69 +/- 0.07; p = 0.02). No differences were seen for potassium, U46619, or glyceryl trinitrate, whereas the effective concentration that induced 50% of maximal effect for U46619 was 6.17-fold lower in the bifurcation than in the main IMA (9.14 +/- 0.28 versus 8.35 +/- 0.09 -log M; p = 0.003), indicating higher sensitivity in the bifurcation.(ABSTRACT TRUNCATED AT 250 WORDS)

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1994

Inhibitory effects of calcium antagonists on alpha-adrenoceptor-mediated contraction in the human internal mammary artery.

1. The internal mammary artery has become a preferred coronary bypass graft. Sympathomimetic amines are spasmogens for vasospasm and calcium antagonists are frequently administered drugs perioperatively. The effect of calcium antagonists on alpha-adrenoceptor-mediated contraction depends on the subtype of alpha-adrenoceptor and the type of origin of vascular smooth muscle. This study was designed to investigate the effect of calcium antagonists on alpha-adrenoceptor-mediated contraction in the IMA. 2. Human IMA segments taken from 22 patients undergoing IMA--coronary artery bypass grafting were mounted in an organ bath under the physiological pressure determined from their own length-tension curves. 3. Three ring segments were allocated into three groups. One served as a control and the others were treated with clinically related concentrations of nifedipine (20 or 200 nM) for 25 min before concentration-contraction curves to alpha 1-adrenoceptor agonist methoxamine (MO) or full alpha-adrenoceptor agonist noradrenaline (NA) were established. 4. In separate experiments, the concentration-relaxation curves to nifedipine were established in the IMA rings precontracted with MO (30 microM) or NA (10 microM). Glyceryl trinitrate (GTN, 3 microM) was added to further relax the vessels. 5. Pretreatment with nifedipine (200 nM) only slightly inhibited the MO- (1.74 +/- 0.32 vs 2.88 +/- 0.56 g) or NA- (2.43 +/- 0.66 vs 3.60 +/- 0.82 g) induced contraction without statistical significance (P > 0.05). 6. On the other hand, nifedipine only caused 34.49% relaxation in the MO-precontracted and 24.39% relaxation in the NA-precontracted IMAs. In contrast, GTN caused 76.16% (against MO, P < 0.05) or 92.22% (against NA, P < 0.0001) relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Agonists↗

PubMed1994

Interaction between endothelin and vasodilators in the human internal mammary artery.

1. The internal mammary artery (IMA) is the primary choice as an arterial graft for coronary artery bypass surgery. Endothelin (ET) has been recently measured with an increased release after cardiopulmonary bypass for coronary artery bypass grafting. Threshold concentrations of ET-1 have been found to amplify specifically contractions induced by noradrenaline and serotonin. This study was designed to investigate the effect of glyceryl trinitrate (GTN) and calcium antagonists on ET-1 contraction in the human IMA. 2. Human IMA segments taken from 21 patients undergoing IMA-coronary artery bypass grafting were mounted in an organ bath under the physiological pressure determined from their own length-tension curves. Four ring segments were allocated into four groups. One served as a control and the others were treated with GTN (10, 100 nM, or 30 microM) for 5 min or nifedipine (20 or 200 nM, or 30 microM) for 25 min before concentration-contraction curves to ET-1 were established. In separate experiments, the concentration-relaxation curves to GTN or nifedipine were established in the IMA rings precontracted with ET-1 (10 nM). 3. Pretreatment of IMA with GTN for 5 min did not alter the ET-1-induced contraction. Pretreatment with 20 or 200 nM of nifedipine slightly but not significantly, altered the maximum contraction induced by ET-1. Higher concentrations (30 microM) significantly reduced the maximum contraction force (P = 0.008). On the other hand, GTN caused 76.44 +/- 6.35% relaxation in ET-1-precontracted IMA. In contrast, the nifedipine-induced relaxation was difficult to establish due to unsustained contraction to ET-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Endothelins↗

PubMed1994

"Vasoactivators"--a new concept for naturally secreted vasoconstrictor substances.

Many vasoconstrictor substances have been demonstrated as being vasodilators through the mechanism of endothelium-derived relaxing factor (EDRF) release. The authors have hypothesized that all naturally secreted vasoconstrictor substances may potentially be vasodilators as well in order to maintain an adequate physiological vascular tone. To test this hypothesis, they studied the effect of thromboxane A2--a naturally secreted vasoconstrictor substance released from platelets, which has not been demonstrated as an EDRF stimulus, using its stable analog U46619 in the porcine coronary artery (CA). The results have shown that U46619 is a stimulus for EDRF biosynthesis/release. This effect may be blocked by the specific inhibitor of EDRF biosynthesis/release NG-nitro-L-arginine (L-NNA). Therefore, this study supports the aforementioned hypothesis. The authors suggest that naturally secreted vasoconstrictor substances may be more accurately termed "vasoactivator" substances. These vasoactivators, according to the balance between their constrictive or relaxing effects, may be classified as (1) Type I: vasoconstriction-predominant type such as acetylcholine (ACh), and U46619 in porcine which mainly cause contraction in endothelium-intact arteries; (2) Type II: balanced type such as norepinephrine (NE) and 5-hydroxytryptamine (5-HT) in porcine CA, which cause little contraction in endothelium-intact arteries but cause a great contraction when the endothelium is denuded. Usually, the receptor subtypes located in the endothelium and smooth muscle stimulated by any one of these vasoactivator substances are different. All these characteristics of vasoconstrictor substances may play an important role in maintaining an adequate vascular tone.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1994

Middle and proximal sections of the human internal mammary artery are not "passive conduits".

Recent studies have shown that blood flow through the internal mammary artery graft is inadequate for maximal exercise and that hypoperfusion may be worsened by high-dose vasopressor therapy that could further reduce arterial graft flow. Histologic studies have suggested that the human internal mammary artery is an elastic "passive conduit" along the majority of its length. However, although the pharmacologic reactivity at the distal section of the internal mammary artery has been extensively studied, this evaluation has never been done at the middle and proximal sections. It is extremely important to understand the contractility at the midsection of the internal mammary artery because, in a critical situation, any contraction may further reduce the internal mammary artery flow. The present study was designed to investigate the following: (1) Is it true that the pharmacologic reactivity of the human internal mammary artery is different among various sections? and (2) Is the human internal mammary artery a nonreactive "passive conduit" at its most important area used as the graft--the middle and the proximal sections? One hundred six human internal mammary artery ring segments taken from patients who underwent internal mammary artery grafting procedures (29 from the proximal, 38 from the middle, and 39 from the distal sections) were studied in the organ bath under a physiologic pressure. Concentration-response curves were established for norepinephrine, endothelin-1, U46619, potassium, and glyceryl trinitrate (precontracted with 10 nmol/L U46619). Contraction forces were standardized (in grams per millimeter circumference) at a pressure of 100 mm Hg. The contraction force was greater in the distal section than in other sections for norepinephrine (p = 0.002) and endothelin-1 (p = 0.04). No differences were seen for potassium, U46619, or glyceryl trinitrate, whereas the effective concentration inducing 50% of maximal response for U46619 was 100-fold lower in the distal than in the middle section (9.06 +/- 0.34 versus 7.06 +/- 0.48 -log M; p = 0.01) indicating higher sensitivity in the distal section. This study for the first time shows various reactivity along the full length of the human internal mammary artery and shows that the distal section is the most reactive part of the graft. However, although the middle and the proximal sections are less reactive to some vasoconstrictors (norepinephrine and endothelin-1), it is not a "passive conduit" and it contracts with all four vasoconstrictors tested.(ABSTRACT TRUNCATED AT 400 WORDS)

Humans↗

PubMed1994

Determinants of operative mortality in elderly patients undergoing coronary artery bypass grafting. Emphasis on the influence of internal mammary artery grafting on mortality and morbidity.

Coronary artery bypass grafting has been performed for elderly patients (> or = 70 years) with increasing frequency. From January 1986 through June 1993, 1399 elderly patients underwent isolated coronary bypass grafting. Of these patients, 823 had saphenous vein grafts alone and 576 had internal mammary artery grafting, including unilateral (n = 546) and bilateral (n = 28). Overall operative mortality was 8.86%. Operative mortality for unilateral internal mammary artery grafting (6.41%) was lower than for saphenous vein grafting only (9.96%, p = 0.021) and bilateral internal mammary artery grafting (21.43%, 6/28, p = 0.018). Fewer patients undergoing internal mammary artery grafting had postoperative complications (low cardiac output, intraaortic balloon pumping, and neurologic complications) than patients having saphenous vein grafting only. To determine risk factors for mortality and the influence of internal mammary artery grafting on the outcome, we analyzed 55 variables (27 preoperative, 15 intraoperative, and 13 postoperative) by univariate analysis. Significant variables (age, gender, height, weight, surface area, diabetes, obesity, body mass index, history of congestive heart failure, myocardial infarction, or arrhythmia, functional class, left ventricular ejection fraction, stenosis of the left anterior descending or right coronary artery, emergency operation, reoperation, number of grafts, perfusion time, and bilateral or right internal mammary artery grafting) were included in a stepwise multiple logistic regression analysis. The logistic regression demonstrates that those preoperative (history of congestive heart failure or myocardial infarction, low ejection fraction, female gender, and old age), intraoperative (long cardiopulmonary bypass time, emergency operation, reoperation, and use of right internal mammary artery grafting), and postoperative (postoperative complications) variables are independently associated with higher mortality. This study reveals the high-risk groups in elderly patients undergoing coronary bypass and suggests that a left internal mammary artery graft in combination with saphenous vein grafting may achieve a lower operative mortality and morbidity than other procedures in selected elderly patients undergoing coronary artery bypass grafting.

Age Factors↗

PubMed1994

Pharmacologic dilatation of the internal mammary artery during coronary bypass grafting.

Spasm of the internal mammary artery during coronary bypass grafting is a widely recognized problem during and after mobilization of the IMA. On the basis of previous laboratory studies, we have developed a buffered vasodilator solution containing glyceryl trinitrate and verapamil (pH 7.4). When tested in human internal mammary artery segments in the organ bath, this solution caused full relaxation of the segments with a 1- to 2-minute onset and a duration of action of more than 2 hours. In 31 patients undergoing internal mammary artery grafting, flow through the internal mammary artery was measured immediately after mobilization and 20 minutes later. In 10 untreated patients, flow increased by 13% from 41.8 +/- 7.1 to 47.3 +/- 7.5 ml/min (p < 0.025). In 11 patients, intraluminal injection of glyceryl trinitrate-verapamil solution into the internal mammary artery on one side caused an increase in flow of 55 +/- 10 ml/min (95%), which was greater than that caused by Ringer's solution, 22 +/- 8 ml/min (53%), in the opposite internal mammary artery (p < 0.025). In another 10 patients intraluminal injection of glyceryl trinitrate-verapamil solution in one internal mammary artery caused an increase in flow of 57.9 +/- 8.7 ml/min (107%), which was similar to that caused by papaverine solution (pH 5.2) in the opposite internal mammary artery of 45.0 +/- 12.3 ml/min (80%). We conclude that intraluminal injection of vasodilator solution is effective in dilating the IMA graft and that because of its rapid onset, long action, and neutral pH, glyceryl trinitrate-verapamil solution may be preferable to papaverine.

Coronary Artery Bypass↗

PubMed1994

Risk factors for operative mortality and sternal wound infection in bilateral internal mammary artery grafting.

To investigate risk factors for operative mortality and sternal infection in patients undergoing bilateral internal mammary artery grafting, we analyzed the data of 199 patients who underwent this procedure from January 1986 through June 1992. These patients were also compared with those who underwent only saphenous vein grafting (1664 cases) and those who underwent unilateral internal mammary artery grafting (3359 cases) during the same time frame. The operative mortality was 3.52% (7/199) in the patients having bilateral internal mammary artery grafting, 2.71% (91/3359) in those having unilateral internal mammary artery grafting, and 8.53% (142/1664) in the patients having saphenous vein grafting (p < 0.0001). The occurrence rate of sternal infections was 2.45% (5/199) for bilateral internal mammary artery grafting, 1.32% (13/1664) for saphenous vein grafting, and 1.19% (20/3359) for unilateral internal mammary artery grafting (p = 0.27). The univariate analysis revealed that age, history of congestive heart failure, emergency operation, ejection fraction, and aortic crossclamp time were significantly correlated with operative mortality and that obesity was correlated with sternal wound infection. Stepwise multiple logistic regression identified that old age (> or = 70 years) (p < 0.0001), long perfusion time (p < 0.0001), and emergency operation (p = 0.0004) are risk factors for operative mortality and that obesity (p = 0.0009) is the only significant risk factor for sternal wound infection. We conclude that bilateral internal mammary artery grafting does not increase operative mortality in properly selected patients. However, this procedure should be carefully chosen in elderly (> or = 70 years) patients and for emergency operation. Obese patients have a high risk for sternal infection after bilateral internal mammary artery grafting.

Aged↗

PubMed1993

Pharmacological relaxation of the saphenous vein during harvesting for coronary artery bypass grafting.

Spasm of the saphenous vein frequently occurs during harvesting from the leg and high-pressure distension is required to restore an adequate diameter for grafting. Forceful distention has been shown to damage the intima and media and may predispose to subsequent occlusion of the vein graft. Various pharmacologic vasodilators are capable of relaxing veins; in this study, we carried out a systematic investigation to determine the appropriate agents and concentrations for use during vein graft operations. In organ baths, human saphenous vein segments were contracted with potassium or a thromboxane mimetic, and vasodilator agents were then applied. Glyceryl trinitrate, 7.2 micrograms/mL, or papaverine hydrochloride, 11.9 micrograms/mL, caused 80% to 100% relaxation of contraction induced by potassium or thromboxane. Verapamil, 15.5 micrograms/mL, relaxed the potassium contraction by 100% and the thromboxane contraction by 75%. Comparison of the time course of action showed that glyceryl trinitrate had a rapid onset and a short duration of maximal action, whereas verapamil (like papaverine) had delayed onset and a long duration. A mixture of glyceryl trinitrate and verapamil combined rapid onset with long duration of action. We now use a mixture of glyceryl trinitrate and verapamil (pH 7.4) topically and intraluminally during harvesting of the saphenous vein to provide a relaxed conduit for coronary artery bypass grafting.

Coronary Artery Bypass↗