Intraoperative blood-flow responses in coronary artery bypass grafts.

Intraoperative graft flow responses in 15 patients who underwent coronary artery bypass grafting (CABG) were studied systematically. The mean blood flow for 13 left anterior descending (LAD) coronary artery grafts was 64 +/- 20 ml/min and for 12 right coronary artery (RCA) grafts was 53 +/- 13 ml/min. Of these, systolic flow was dominant in one LAD and three RCA grafts, suggesting the perfusion of the right ventricle or the noncontractile left ventricle segment, or both. Five LAD and two RCA grafts had a negligible reactive hyperemic response, and the underlying cause for this can be futher examined by observing their phasic flow patterns. Temporary occlusion of the coronary artery proximal to the site of anastomosis produced increased flow in 8 grafts, indicating the presence of competitive flow; decreased flow was observed in 15 grafts, indicating the presence of proximal retrograde flow which may play a role in the proximal occlusion of the bypassed artery later. Thus intraoperative flow studies supplement the preoperative angiographic findings in elucidating the pathophysiology involved and are useful in evaluating CABG operations.     

Coronary artery bypass surgery for chronic total occlusion of the left main coronary artery by means of intermittent antegrade cold blood cardioplegia

From January, 1984 to May, 1990 eleven patients (men 9, women 2) underwent coronary artery bypass surgery for chronic total occlusion of the left main coronary artery by means of intermittent antegrade cold blood cardioplegia. The ages ranged from 33 to 74 (mean 56) years. The causes of the total occlusion of the left main coronary artery were atherosclerosis in 10 patients and aortitis syndrome in one. Four patients had history of a previous myocardial infarction. Preoperative selective coronary arteriography revealed well developed collateral vessels from the RCA to the LCA in all patients. One to five coronary arteries were bypassed. Myocardial protection was obtained in the usual fashion: antegrade intermittent cold blood cardioplegia with topical cardiac cooling. All patients were successfully weaned off from cardiopulmonary bypass without the need of IABP assist. No patient developed perioperative myocardial infarction. All grafts were patent postoperatively. Treadmill testing was negative in all patients. We believe that coronary artery bypass surgery for chronic total occlusion of the left main coronary artery can be performed safely with intermittent antegrade cold blood cardioplegia.     

Surgical revascularization of acute evolving myocardial infarction without blood cardioplegia fails to restore postischemic function in the involved segment

This study determines the additional protection provided by multidose hypothermic potassium blood cardioplegia over cardiopulmonary bypass alone following one hour of coronary occlusion. In 19 anesthetized dogs having an open-chest procedure, the left anterior descending coronary artery (LAD) was occluded for one hour, and this resulted in loss of active shortening in the affected zone (sonomicrometry). Cardiopulmonary bypass was established, and the dogs were divided into two groups based on the mode of reperfusion. In 10 dogs, hearts were arrested for one hour with amino acid-enhanced multi-dose blood cardioplegia; the ligatures were removed prior to the second infusion. In the 9 remaining dogs, the ligatures were removed and reperfusion was initiated with unmodified blood on total vented bypass. Both groups were reperfused for one additional hour. Postischemic levels of adenosine triphosphate (ATP) were comparable in the blood cardioplegia and bypass groups, and subendocardial levels averaged 42.8% and 45.8% of controls, respectively. Levels of creatine phosphate returned to control values. Subendocardial water content was significantly less in the blood cardioplegia hearts than the bypass hearts (79.4 +/- 0.5% vs. 81.5 +/- 0.5%; p less than .05); subendocardial water content in the blood cardioplegia group was not different from controls (78.6 +/- 0.1%). Blood cardioplegia restored significantly more fractional shortening than total vented bypass alone (39.3 +/- 9.8% vs. 6.3 +/- 9.1% of control), despite similarities in postischemic levels of ATP. We conclude that blood cardioplegia allows better myocardial salvage in the setting of evolving infarction. Therefore, attention must be directed to both the conditions (bypass, delivery pressure) and composition (cardioplegia) of reperfusion.     

The relationship of myocardial stroke work to coronary flow velocity immediately after aortic valve replacement

BACKGROUND: The interrelations between myocardial stroke work and coronary flow velocity have not been fully defined during aortic valve replacement or with different cardioplegias. METHODS: Twenty-six patients (15 men age 63+/-13 years) who had elective isolated aortic valve replacement were studied by transesophageal Doppler echocardiography with simultaneous high fidelity left ventricular pressure. Fifteen patients received cold blood cardioplegia and 11 had warm blood cardioplegia. Myocardial stroke work and flow velocities in proximal left anterior descending coronary artery were quantified simultaneously before cardiopulmonary bypass and at 1, 6, 12, and 20 hours afterwards. RESULTS: Myocardial stroke work decreased postoperatively in both groups (160+/-19 versus 228+/-19 mJ/cm3 per minute, with cold blood cardioplegia; 135+/-22 versus 227+/-22 mJ/cm3 per minute with warm blood cardioplegia; both p<0.001 versus time, but p>0.05 versus cardioplegia, by two-way analysis of variance). Left anterior descending artery flow velocity-time integral per minute increased significantly in both groups (26.1+/-2.1 versus 15.0+/-2.1 m/min with cold blood cardioplegia; 32.8+/-2.5 versus 14.4+/-2.5 m/min with warm blood cardioplegia; both p<0.001 versus time, but p>0.05 versus cardioplegia). Thus, at 1 hour postoperatively the mJ x cm(-3) x m(-1) x min ratio of myocardial stroke work to left anterior descending artery flow velocity-time integral decreased significantly in both groups (4.3+/-1.6 versus 16.3+/-1.7 mJ x cm(-3) x m(-1) x min with warm blood cardioplegia, and 7.4+/-1.4 versus 17.9+/-1.4 J x cm(-3) x m(-1) x min with cold blood cardioplegia; both p<0.001 versus time). Warm blood cardioplegia was also associated with a lower mean ratio perioperatively than that with cold blood cardioplegia (7.8+/-0.9 versus 10.9+/-0.7 mJ x cm(-3) x m(-1) x min, p = 0.014). CONCLUSIONS: Coronary hyperemia occurs for at least 20 hours postoperatively when myocardial stoke work has decreased. The ratio of myocardial stroke work to coronary flow velocity appears to be more sensitive than either alone in differentiating the effect of warm versus cold blood cardioplegia.     

Effect of sialyl Lewis(x) oligosaccharide on myocardial and cerebral injury in the pig

BACKGROUND: Although administration of the sialyl Lewis(x) oligosaccharide may reduce myocardial injury after ischemia-reperfusion, its effect on coronary and cerebral microvascular regulation and its clinical application during cardiac operation have not been examined. METHODS: Pigs were placed on normothermic cardiopulmonary bypass after 30 minutes of left anterior descending coronary artery occlusion. The hearts were then arrested with cold high potassium cardioplegia. After 1 hour the cross-clamp was removed and the pigs were weaned from cardiopulmonary bypass and perfused for an additional 1 hour. CY-1503 (a sodium salt of the sialyl Lewis(x) oligosaccharide, n = 6) was administered before reperfusion. Six other pigs received saline vehicle. Endothelium-dependent relaxation of precontracted coronary and brain arterioles (70 to 180 microm) to adenosine 5'-diphosphate and endothelium-independent relaxation to sodium nitroprusside were studied in vitro with videomicroscopy. Control values were obtained from uninstrumented pigs. Myeloperoxidase activity in the myocardium and brain was measured to quantify neutrophil infiltration. Cardiac function and perfusion were assessed by left ventricular systolic pressure, maximum rate of increase of left ventricular pressure, left anterior descending coronary artery blood flow and percent segmental shortening, and cerebral vascular resistance, internal carotid artery blood flow, and the constitutively expressed and inducible isoform of nitric oxide synthase mRNA were measured. RESULTS: The impaired myocardial contractile function after ischemia and cardioplegia was not improved by administration of CY-1503. The reduced endothelium-dependent relaxation responses of coronary and brain arterioles during ischemia followed by cardioplegia and cardiopulmonary bypass were improved with CY-1503, but the altered pattern of organ perfusion was not improved. Myeloperoxidase activity was increased in the heart after ischemia-cardioplegia and in the brain after cardiopulmonary bypass. CY-1503 reduced myeloperoxidase activity in both the myocardium and in the brain. Expressions of myocardial inducible isoform or constitutively expressed nitric oxide synthase were not altered in the heart. CONCLUSIONS: Although the sialyl Lewis(x) oligosaccharide does reduce neutrophil infiltration and endothelial injury in the coronary and cerebral microcirculation after cardiopulmonary bypass, it does not have significant beneficial acute effects on organ perfusion or function in the myocardium or brain.     

Cold potassium cardioplegia versus topical hypothermia and intermittent aortic occlusion for myocardial protection during coronary artery surgery: a randomized clinical study

The effect of two different myocardial preservation techniques on perioperative myocardial necrosis during coronary artery bypass surgery was assessed by serial myocardial creatine kinase determinations in 100 consecutive patients operated on by the same surgeon. Topical hypothermia with cold potassium cardioplegia was used randomly in 50 patients (group 1), and topical hypothermia with local interruption of the coronary circulation was used in the other 50 patients (group 2). Myocardial creatine kinase was measured by column chromatography every 6 hours for 36 hours after surgery. There was no significant difference between the two groups in terms of age, sex, functional class, extent of coronary artery disease, number of bypassed arteries, ejection fraction, or cardiopulmonary bypass time. Myocardial creatine kinase release (mean +/- standard error of the mean) was 193 +/- 33 IU/L X hours in group 1 patients operated on with cardioplegia and 210 +/- 31 IU/L X hours in group 2 patients operated on with topical hypothermia (p greater than 0.5). Myocardial creatine kinase peaks were 9.2 +/- 1.9 IU/L and 10.0 +/- 1.6 IU/L, respectively (p greater than 0.5). Perioperative myocardial infarction, as defined by serum enzyme activity and electrocardiographic criteria, occurred in 4 patients in group 1 and 3 patients in group 2. Thus, the addition of cardioplegia to topical hypothermia, although perhaps offering technical advantages, does not appear to improve myocardial protection over topical hypothermia with local interruption of the coronary circulation during coronary artery bypass surgery.     

Effects of phenylephrine on transmural distribution of myocardial blood flow in regions supplied by normal and collateral arteries during cardiopulmonary bypass.

Cardiopulmonary bypass is frequently accompanied by decreased peripheral vascular resistance with resultant hypotension that is unresponsive to increased flow rates. Alpha adrenergic agonists are routinely used to increase peripheral vascular resistance and augment blood pressure. In this study, the effects of the alpha adrenergic stimulant phenylephrine on blood flow distribution during cardiopulmonary bypass in myocardium supplied by normal and collateral arteries were studied in eight mongrel dogs. Microsphere determinations of blood flow were made following augmentation of perfusion pressure with phenylephrine and were compared with intraoperative normotensive and hypotensive control levels. With systemic flow rates held constant, phenylephrine was infused in doses adequate to raise perfusion pressure to normotensive levels following hypotension. In the normal region (NR), blood flow was returned to normotensive control levels with flow favoring the subendocardium. In the region supplied by collateral vessels (CR), however, phenylephrine infusion failed to return flow to the normotensive control level in the subendocardial layer, and the flow imbalance present during hypotension was not corrected. An analogue model of the calculable resistances in the CR is presented, which indicates that phenylephrine increased resistance in the collateral vessels. Associated with this inflow restriction is decreased resistance or vasodilatation of the intramyocardial vessels supplied by collateral coronary arteries.     

Controlled reperfusion following regional ischemia

The ability to reverse acute coronary occlusion with fibrinolytic agents and percutaneous transluminal angioplasty has increased interest in the revascularization of ischemic myocardium. This study defines changes in global ventricular function, mass, and compliance during acute coronary occlusion and following reperfusion with blood in the beating and arrested heart. In 17 dogs on cardiopulmonary bypass, the proximal left anterior descending coronary artery was occluded for 45 minutes. In 12 dogs, flow was reestablished by releasing the coronary snare in the beating heart. In the other 5 dogs, the snare was released during a continuous 10-minute infusion of blood potassium cardioplegia in the arrested heart. Coronary occlusion resulted in significant decreases in stroke work index and left ventricular (LV) mass, but compliance was unchanged. Reperfusion in the beating heart increased LV mass compared with the values measured before ischemia (104 +/- 5 versus 95 +/- 5 gm; p less than 0.05) and decreased LV compliance (39 +/- 4 versus 53 +/- 4 ml at LV end-diastolic pressure of 8 mm Hg; p less than 0.05). In contrast, with blood cardioplegia-based reperfusion in the arrested heart, LV mass and LV compliance remained unchanged from control values. We conclude that revascularization of acutely ischemic myocardium in the beating heart further impairs LV function by increasing LV mass and decreasing compliance. This damage can be avoided by reperfusion with blood cardioplegia in the arrested heart.     

Efficacy of coronary sinus cardioplegia in patients with complete coronary artery occlusions

Myocardial areas distal to complete coronary artery occlusions are poorly protected by antegrade cardioplegia. We assessed the effects of coronary sinus cardioplegia in 30 patients undergoing bypass operations and at high risk of cardioplegic maldistribution because of the following anatomical patterns of coronary artery disease: critical (greater than or equal to 50%) stenosis of the left main trunk with total occlusion of the right coronary artery (16 patients) or critical (greater than or equal to 70%) stenosis of the right coronary artery with total occlusion of the left anterior descending (11 patients) or circumflex artery (3 patients). After induction of arrest through the aorta, coronary sinus cardioplegia was given intermittently during the cross-clamp period at a flow rate of 100 mL/min. Intraoperatively, occluded arteries were consistently found to be filled with the retrogradely infused solution. One patient died early postoperatively of low cardiac output and a second patient died later during his hospital stay, presumably of an arrhythmia. At autopsy, none of them had pathological evidence of inadequate myocardial protection. One patient sustained a myocardial infarction and 3 others required inotropes for more than 24 hours postoperatively. Postoperative values for right and left stroke volume indices were not significantly different from prebypass levels. Overall, these results are consistent with the occurrence of limited intraoperative ischemic damage and, by inference, suggest the efficacy of the coronary sinus route in preserving myocardial areas supplied by completely occluded coronary arteries and, hence, in jeopardy of inadequate cardioplegia delivery.     

Effects of diltiazem cardioplegia on global function, segmental contractility, and the area of necrosis after acute coronary artery occlusion and surgical reperfusion

We investigated the effects of diltiazem cardioplegia on myocardial function and infarct size in the region of the left anterior descending artery after acute occlusion and reperfusion during cardiopulmonary bypass. Sheep (30 kg) were subjected to 1 hour of regional myocardial ischemia by occlusion of the left anterior descending artery and assigned to a control (n = 8) or experimental group (n = 5). Control animals were placed on cardiopulmonary bypass and the heart arrested with potassium cardioplegia. The left anterior descending artery was released and two additional doses of 100 ml of cardioplegic solution were infused during the total cross-clamp time of 30 minutes. The animals were then weaned from bypass after 1 hour and beating, working reperfusion maintained for an additional 4 hours. The experimental group followed the same protocol except that the cardioplegic solution contained diltiazem (1.4 mg/L). Segmental myocardial function was determined by pairs of ultrasonic crystals in the area at risk, control segment, and minor axis. Global contractility was determined from maximum derivative of left ventricular pressure and cardiac output. The area at risk was determined by injecting monastral blue dye into the left atrium with the left anterior descending artery briefly reoccluded, and the area of necrosis was determined by measuring with a planimeter non-triphenyltetrazolium chloride stained areas in the sectioned left ventricle. After 5 hours of reperfusion, not only did the diltiazem group demonstrate better global contractility as defined by the derivative of left ventricular pressure (1853 +/- 292 versus 979 +/- 191, p = 0.05) but, in addition, the systolic shortening in the ischemic area improved significantly when compared with the control group (9.4 +/- 4 versus 2.13 +/- 0.77, p = 0.05). The group receiving diltiazem cardioplegia had an area of necrosis to area at risk ratio of 31.4% +/- 3%, which was significantly better than this ratio in the control group of 60.75% +/- 7% (p = 0.01). Diltiazem cardioplegia results in improved global and segmental contractility and limits the infarct size after occlusion of the left anterior descending artery and surgical reperfusion.     

Intraoperative assessement of coronary flow and coronary vascular resistance during coronary bypass surgery

The measurement of coronary graft flow rates is a well-established method of assessing graft function intraoperatively. In order further to understand the dynamics of graft function, the resistance to the flow was considered a desirable measurement intraoperatively. The coronary vascular resistance (CVR) was estimated by applying the Poiseuille-Hagen equation. The CVR was estimated at zero cardiac work (during cardioplegic arrest) using fixed perfusion flow rates and estimating the pressures produced. After going off cardiopulmonary bypass (CPB), the bypass graft flow (F) was estimated by a standard ultrasound Doppler technique. The perfusion pressure over the perfused coronary graft was then determined and the CVR in the working heart ascertained. The CVR was studied in 178 vein grafts in 59 patients undergoing coronary bypass surgery. The mean CVR in the cardioplegic heart (c-CVR) varied from 0.81 to 2.3 mmHg/ml/min for various coronary artery diameters and was significantly higher in small diameter arteries compared with larger arteries (p < 0.0002). Consequently significant high flows were found in the large vessels compared with the smaller ones (p < 0.0001). The mean c-CVR during cardioplegia of 1.57 +/- 0.06 increased significantly to 1.75 +/- 0.07 mmHg/ml/min after the procedure (p-CVR) and was attributed to the dynamic resistance of the working heart. The post-CPB graft flow was significantly and negatively correlated to the c-CVR of the arrested heart. The measurement of coronary vascular resistance reveals coronary beds at potential high risk for inadequate perfusion. Such areas are usually fed by small vessels with low flows. The working heart, in turn, increases the coronary resistance following cardioplegia during the surgical procedure.     

Continuous versus intermittent cardioplegia in the presence of a coronary occlusion

Coronary artery occlusions can alter the distribution of cardioplegia and result in ischemic damage. This study was undertaken to determine whether continuous antegrade cardioplegia delivery would result in colder temperatures and provide better washout of acid metabolites than is possible with intermittent antegrade cardioplegia when coronary occlusions are present. Twenty pigs were placed on cardiopulmonary bypass and underwent 2 hours of ischemic arrest with occlusion of the middle left anterior descending coronary artery followed by 1 hour of reperfusion without occlusion of that artery. Ten pigs received intermittent (every 20 minutes) antegrade potassium crystalloid cardioplegia (4 degrees C), and 10 others had the same solution given continuously (30 mL/min). Cardioplegia distribution was assessed by continuous monitoring of myocardial pH (Khuri pH probe) and temperature in the region beyond the occlusion of the left anterior descending coronary artery. Both cardioplegic techniques resulted in tissue acidosis (continuous group, 6.69 +/- 0.08, versus intermittent group, 6.73 +/- 0.07; not significant). Average temperature in the left anterior descending coronary artery during arrest was also similar in both groups (continuous group, 18.3 degrees +/- 0.5 degrees C, versus intermittent group, 18.2 degrees +/- 0.5 degrees C). Because of these metabolic changes, both cardioplegic techniques resulted in abnormal wall motion in the anteroseptal region using two-dimensional echocardiography, but the scores were not significantly different (continuous group, 1.5 +/- 0.3, versus intermittent group, 1.6 +/- 0.4; 4 = normal to 0 = dyskinesia).(ABSTRACT TRUNCATED AT 250 WORDS)     

Surgery for chronic total occlusion of the left main coronary artery--myocardial preservation

We report seven patients with chronic total occlusion of the left main coronary artery that were operated in our institution and discuss the myocardial preservation options in these patients. In addition to total occlusion of the left main coronary artery, three patients also had severe lesions of right coronary artery. Prior myocardial infarction history and significantly depressed left ventricle functions were detected in all three patients with right coronary artery lesions. Five patients were operated on cardiopulmonary bypass while two patients were operated off pump. All patients received alternating antegrade/retrograde cardioplegia for myocardial preservation. In patients with simultaneous right coronary artery disease we first established the origin of the collaterals to the left coronary system. For patients with collaterals arising from the right coronary artery segment distal to the right coronary artery lesion, the antegrade component was administered through the saphenous vein graft bypassed to a distal part of right coronary artery segment. Thus we have achieved a more effective distribution of the antegrade cardioplegia. In off-pump-operated patients the left coronary system was revascularized before the right coronary system. Postoperative low cardiac output syndrome occurred in only one patient who was operated off pump. There was no operative and early mortality. Mean follow-up was 32 +/- 21.42 (range, 4 to 60) months. Alternating antegrade/retrograde cardioplegia was used with acceptable results in patients with total occlusion of the left main coronary artery. In patients with simultaneous RCA lesion we recommend regulation of the antegrade component based on the origin of collaterals that supplies the left coronary system. In off-pump-operated patients we suggest avoiding of clamping of right coronary artery at the beginning of the operation while it still supplies all the coronary circulation.     

Superiority of retrograde cardioplegia after acute coronary occlusion

Because antegrade cardioplegia may limit the distribution of cardioplegia beyond a coronary occlusion, this study was undertaken to determine whether retrograde coronary sinus cardioplegia provides superior myocardial protection during revascularization of an acute coronary occlusion. In 20 adult pigs, the second and third diagonal branches were occluded with a snare for 1 1/2 hours. Animals were then placed on cardiopulmonary bypass and underwent 30 minutes of ischemic arrest with multidose, potassium, crystalloid cardioplegia. In 10 animals, the cardioplegia was given antegrade through the aortic root, whereas in 10 others, it was given retrograde through the coronary sinus. After the arrest period, the coronary snares were released and all hearts were reperfused for 3 hours. Postischemic damage in the myocardium beyond the occlusions was assessed by wall motion scores using two-dimensional echocardiography (4 = normal to -1 = dyskinesia), the change in myocardial pH from preischemia, and the area of necrosis/area of risk (histochemical staining). Hearts protected with retrograde coronary sinus cardioplegia had less tissue acidosis (change in pH = 0.08 +/- 0.03 versus 0.41 +/- 0.13; p less than 0.05), higher wall motion scores (2.0 +/- 0.6 versus 1.3 +/- 0.3; not significant), and less myocardial necrosis (43.4% +/- 3.6% versus 73.3% +/- 3.5%; p less than 0.0001). We conclude that retrograde coronary sinus cardioplegia provides more optimal myocardial protection than is possible with antegrade cardioplegia after revascularization of an acute coronary occlusion.     

Electroplegia: an alternative to blood cardioplegia for arresting the heart during conventional (on-pump) cardiac operation

BACKGROUND: Aortic cross-clamping is contraindicated in patients with severe atherosclerosis of the ascending aorta, and administration of chemical cardioplegia may be cumbersome in these patients. In this study, we demonstrate an alternative method of achieving cardioplegia by electrical stimulation of the vagus nerve. METHODS: In anesthetized canines, the left anterior descending coronary artery was reversibly ligated for 90 minutes, followed by cardiopulmonary bypass (CPB) and randomization to three groups (n = 8 each): (1) BCP group: 1 hour of intermittent hypothermic (4 degrees C) blood cardioplegia infusion; (2) CPB group: 1 hour of CPB alone; (3) EP group (group receiving electroplegia): 1 hour of intermittent vagal stimulation (total of 60 20-second electrical stimuli at 40 Hz, 6 to 10 V) with adjunctive pyridostigmine (0.5 mg/kg), verapamil (50 microg/kg), and propranolol (80 microg/kg) to potentiate hyperpolarization and suppress ectopic escape beats. RESULTS: The EP group achieved consistent intervals of arrest with 3.8 +/- 1.2 escape beats per 20-second stimulation period. After 2 hours of reperfusion off CPB, the left anterior descending coronary artery segmental shortening was reduced from baseline in all groups, but the segmental shortening recovered to a greater extent in the EP group than in either the CPB or BCP group (2.4% +/- 1.4% versus -1.3% +/- 1.3% versus -4.0% +/- 0.8%, p < 0.05). Infarct size (TTC stain, percentage of area at risk) was comparable among groups (EP: 20.9% +/- 4.7%; CPB: 29.6% +/- 3.2%; BCP: 25.1% +/- 5.7%). Postischemic left anterior descending coronary artery endothelial function (percent maximum relaxation to acetylcholine) was depressed in the EP group (68.6% +/- 7.6% versus 102.3% +/- 6.4%, p < 0.05), but was comparable versus nonischemic circumflex function in the BCP group (77.1% +/- 11.9% versus 100.4% +/- 10.0%, p = 0.15) and the CPB group (93.8% +/- 6.6% versus 93.3% +/- 6.6%). CONCLUSIONS: Electroplegia achieves elective intermittent cardiac arrest, avoids hypothermia, chemical cardioplegia, and aortic cross-clamping, with physiological outcomes comparable to blood cardioplegia.     

Continuous warm blood cardioplegia preserves cardiac autonomic function.

We studied in anesthetized dogs, the effects of cardiopulmonary bypass with normothermic whole blood, crossclamping of the aortic root, and continuous warm blood cardioplegia on the ability of the efferent sympathetic nervous system to augment the heart and that of the efferent parasympathetic nervous system to depress the heart. In control states, heart rate, atrial force of contraction, and right and left ventricular wall systolic pressures were augmented by stimulation of the intrathoracic efferent sympathetic nervous system and by administration of isoproterenol into the systemic circulation. After 1 hour of normothermic cardiopulmonary bypass that utilized aortic crossclamping and continuous perfusion of the coronary arteries with normothermic blood (20 mEq/L potassium), cardiac-augmenting effects induced by the efferent sympathetic nervous system and by isoproterenol were similar. Depressive responses elicited by the efferent parasympathetic nervous system were also unaffected by these procedures. Continuous warm blood cardioplegia does not result in impairment of the efferent sympathetic nervous system regulating the heart.     

Cardiac prostacyclin kinetics during cardiopulmonary bypass

We have investigated the response of systemic and myocardial prostacyclin metabolism to cardiopulmonary bypass and 30 minutes of hypothermic (22 degrees C), hyperkalemic (25 mEq K+) surgical cardioplegia. Thirteen adult mongrel dogs of either sex (range 21 to 36 kg) underwent sterile cardiopulmonary bypass without donor blood. Prostacyclin levels were obtained after cannulation, 20 minutes after onset of partial bypass, and 5 seconds after the onset of cardioplegia 1 (CP-1) and cardioplegia 2 (CP-2, 30 minutes later). Samples were drawn from the thoracic aorta, the aortic root below cross-clamping, and the coronary sinus. The stable metabolite of prostacyclin, 6-keto-PGF1 alpha was measured by double-antibody radioimmunoassay (pg/ml; values +/- standard error of the mean). We found that the onset of partial bypass is associated with significant increase in the systemic production of 6-keto-PGF1 alpha (122 +/- 33 versus 518 +/- 187; p less than 0.05), which persists throughout the experiment. A small but significant positive cardiac gradient of 6-keto-PGF1 alpha is found after cannulation (aortic root 122 +/- 33, coronary sinus 202 +/- 57, p less than 0.05). This gradient is more pronounced during partial bypass (aortic root 518 +/- 187, coronary sinus 686 +/- 186 p less than 0.05), when significant cardiac lactate extraction (p less than 0.005) is observed. After cross-clamping, a significantly increased gradient of 6-keto-PGF1 alpha is found during CP-1 (aortic root 74 +/- 10, coronary sinus 264 +/- 46, p less than 0.05 versus cannulation) in the presence of significant cardiac lactate production (p less than 0.005). A further significant increase in 6-keto-PGF1 alpha production is noted during the CP-2 infusion (aortic root 73 +/- 10, coronary sinus 483 +/- 83; p less than 0.01 versus CP-1), which is inversely related to cardiac oxygen uptake and endocardial/epicardial flow ratio. Our data demonstrate significant production of prostacyclin in the systemic and cardiac circulations during cardiopulmonary bypass and surgical cardioplegia. They further indicate that both ischemic and nonischemic stimuli regulate prostacyclin metabolism during cardiopulmonary bypass.     

Effect of coronary artery bypass grafting on native coronary artery stenosis. Comparison of internal thoracic artery and saphenous vein grafts

BACKGROUND: The purpose of this study was to investigate the influence of coronary artery bypass grafting on the degree of stenosis of the native coronary artery. METHODS: Experimental design: retrospective data analysis. Setting: University hospital. Patients: consecutive patients undergoing coronary artery bypass grafting (n=52). Bypasses using internal thoracic artery grafts (n=26) and saphenous vein grafts (n=37) to incompletely occluded coronary arteries were studied. Interventions: coronary artery bypass grafting using internal thoracic artery or saphenous vein grafts. Measures: stenosis of the native coronary artery on angiography. RESULTS: Three recipient coronary arteries bypassed with internal thoracic artery grafts (12%) and 14 recipient coronary arteries bypassed with saphenous vein grafts (38%) showed progression of narrowing (p=0.024). Two recipient coronary arteries bypassed with internal thoracic artery grafts (8%) and 13 recipient coronary arteries bypassed with saphenous vein grafts (35%) showed total occlusion (p=0.016). Hypertension, hyperlipidemia, diabetes mellitus, and smoking history did not correlate with progression of stenosis of the native coronary arteries. Graft flow measured during surgery in the saphenous vein grafts was not significantly different between the group that exhibited progression of the native stenosis and the group that did not. CONCLUSIONS: Coronary artery bypass grafting with saphenous vein grafts may result in progression of stenosis of the recipient coronary artery. This is less likely after coronary artery bypass grafting with internal thoracic artery grafts. This difference may be due to the ability of the pedicled internal thoracic artery graft to regulate flow. Thus competitive flow in the native coronary artery is minimized. This has significant clinical implications.     

A randomized study of the systemic effects of warm heart surgery.

The technique of warm heart surgery is defined as continuous warm blood cardioplegia and normothermic cardiopulmonary bypass. Although the systemic effects of traditional myocardial protection are well known, the effects of warm heart surgery are not. In a prospective trial, 204 patients undergoing coronary artery bypass grafting were randomized to the warm heart surgery technique (normothermic group) or traditional intermittent cold blood cardioplegia and cardiopulmonary bypass (hypothermic group). The groups had similar heparin sodium requirement, activated clotting times, urine output, hematocrit, and blood product utilization. There were no differences in hemodynamics immediately after cardiopulmonary bypass. The normothermic patients had a higher incidence of spontaneous defibrillation at cross-clamp removal (84%) than the hypothermic patients (33%) (p less than 0.01). An increase in the flow rate of low K+ cardioplegia was necessary to eradicate electrical activity during aortic occlusion more often in the normothermic patients (20%) than in the hypothermic patients (3%) (p less than 0.01). When low K+ cardioplegia was ineffective, high K+ cardioplegia was necessary to eradicate electrical activity in 31% of the normothermic patients compared with 10% of the hypothermic patients (p less than 0.05). The total cardioplegia volume delivered to the normothermic group (4.7 +/- 1.9 L) was higher than that delivered to the hypothermic group (2.6 +/- 0.8 L) (p less than 0.01). Although urine output was similar in both groups, the serum K+ levels were higher in the normothermic group (5.7 +/- 0.8 mmol/L) than in the hypothermic group (5.3 +/- 0.8 mmol/L) (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Endarterectomy and surgical angioplasty without cardiopulmonary bypass

Surgical angioplasty for ostial stenosis of the major coronary arteries is a well-established treatment modality. Management of discrete stenoses of distal coronary arteries in the presence of mild proximal disease is a challenging task. Percutaneous intervention or grafting beyond the diseased segment may be limited by size of the target vessel, whereas endarterectomy followed by graft placement may result in graft occlusion due to competitive native flow. Patch angioplasty with or without endarterectomy is an effective option in this setting, which can be performed without cardiopulmonary bypass in the appropriate group of patients. A patient with triple vessel coronary artery disease and a discrete lesion in the posterior descending artery underwent off-pump endarterectomy with vein patch angioplasty in combination with bypass grafting to left anterior descending and obtuse marginal arteries. Operative technique and intraoperative strategies are discussed.