Effect of venting on myocardial protection by hypothermic cardioplegic arrest

Myocardial rewarming between cardioplegic (CP) infusions is in part attributable to blood circulating through the heart from collateral channels. This experiment was performed to determine if the type of left ventricular (LV) venting affects myocardial temperature (temp) or alters myocardial protection. Twelve dogs underwent cardiopulmonary bypass (CPB) at 37 degrees C and were subjected to 100 min of cardioplegic arrest by intermittent coronary infusion of 300 ml 0-4 degrees C CP solution. Arterial, central venous, left atrial, and LV pressures; cardiac output; systemic, septal (S), right ventricular (RV), and LV temp; myocardial ATP and glycogen were measured; LV pressure/volume curves and LV dp/dt were calculated. Group A (6 dogs) had an LV vent during CPB, and Group B (6 dogs) had the aorta vented via the CP line. CP infusion lowered LV temp to 8 degrees C in Group A vs 13 degrees C in Group B (P less than 0.000002); S temp was lowered to 7 degrees C in Group A vs 11 C in Group B (P less than 0.00007); and RV temp was lowered to 16 degrees C in Groups A and B. Ten minutes after CP, LV and S temp increased to 20-21 degrees C in Groups A and B, and RV temp to 24-25 degrees C in Groups A and B. Twenty minutes after CP all temperatures were the same. Hemodynamics and myocardial metabolic studies were similar in the two groups. CONCLUSIONS: Hearts vented via the LV cooled to a lower temperature vs those vented via the aorta. Venting did not affect myocardial rewarming, myocardial metabolites, or ventricular function.     

Efficacy of crystalloid cardioplegic solutions in patients undergoing myocardial revascularization. Effect of infusion route and regional wall motion on preservation of adenine nucleotide stores

The effect of varying the mode of cardioplegic delivery and the presence of regional wall motion abnormalities on myocardial protection by crystalloid cardioplegic solutions was assessed in 68 patients undergoing coronary artery bypass grafting. Serial transmural biopsy specimens from the left ventricular apex were assayed for adenosine triphosphate. All patients had more than 75% stenosis of the left anterior descending coronary artery. They were prospectively randomized into Groups I and II to receive (I) all cardioplegic solution infused via the aortic root or (II) reinfusions of cardioplegic solution given both centrally and through the completed distal left anterior descending anastomosis. Patients were also stratified as to the presence of normal (N) or impaired (Ab) apicoanterior regional wall motion. Inadequate delivery of cardioplegia during ischemia in Group I was manifested by a 41% (p less than 0.01) depletion of adenosine triphosphate stores in abnormally contracting myocardium distal to the left anterior descending stenosis that was not repleted after restoration of coronary flow and a 27% (p less than 0.05) decline in ATP stores during reperfusion in myocardium with normal preoperative wall motion. In contrast, nucleotide stores were preserved at preischemic levels throughout ischemia and reperfusion in Group II regardless of preoperative wall motion. Preservation of ATP did not correlate with duration of ischemia, highest recorded septal temperature, or volume of cardioplegic solution infused. Two patients in each group had a new perioperative infarction. However, 38% of patients in Group IAb required transient inotropic support versus 5% in Group IIAb (p less than 0.05). These data emphasize that reinfusion of cardioplegic solutions distal to coronary obstructions is mandatory for optimal myocardial protection during coronary revascularization.     

Chronic Hypoxemia Depresses Global Ventricular Function and Predisposes to the Depletion of High-Energy Phosphates during Cardioplegic Arrest: Implications for Surgical Repair of Cyanotic Congenital Heart Defects

Persistence of impaired ventricular function after repair of cyanotic congenital heart defects may be due to previous exposure to chronic hypoxemia or to perioperative ischemic injury. Clarification of this phenomenon was sought in a canine model of cyanotic cardiovascular disease (Group I), in which the left atrium was anastomosed proximal to the banded pulmonary artery. Animals that had pulmonary artery banding alone (Group II) or no prior surgical intervention (Group III) served as controls. All Group I animals became cyanotic during the study period (arterial oxygen tension, 38 ± 4 mm Hg; hematocrit, 55 ± 5%). Radionuclide-determined ejection fractions performed three months after operation showed significant depression of global biventricular function by 16 to 29% (p < 0.05) compared with groups II and III. On cardiopulmonary bypass, all hearts were subjected to 4°C potassium cardioplegic arrest and reperfusion with serial assays for myocardial adenosine triphosphate (ATP) and creatine phosphate (CP) levels. The ATP and CP stores in each ventricle were similar at all sampling intervals, and preischemic levels were comparable in cyanotic and control groups. However, ATP levels were significantly depressed 37 to 43% from preischemic levels (p < 0.02) after arrest and reperfusion in cyanotic dogs, but they were preserved in Groups II and III. During ischemia, CP stores were depleted to 27% of preischemic values in Group I but only to 46 to 63% of preischemic levels in the control groups (p < 0.05). These data indicate that chronic hypoxemia impairs global ventricular function and predisposes to the accelerated depletion of high-energy phosphates during cardioplegic arrest. The formulation of new intracoronary perfusates for the cyanotic myocardium seems warranted.     

Identification and control of noncoronary collateral blood flow

To identify the source of noncoronary collateral myocardial blood flow and to establish methods to control it during induced ischemia, 29 dogs were placed on cardiopulmonary bypass. The right and left ventricles were vented, vent flows were measured volumetrically, and intracavitary left ventricular (LV) pressures were monitored. After induction of ischemia by aortic cross-clamping and infusion of cardioplegic solution, six different microspheres 7 to 10 microns in diameter were injected into the aorta at six different times to measure myocardial blood flow during the following interventions:vent drainage of the right or left ventricle or both, proximal ligation of both coronary arteries, severance of the proximal pulmonary artery or the ascending aorta or both, and ligation of the bronchial arteries. Without effective LV venting, LV intracavitary pressure rose to 7.0 +/- 0.1 mm Hg (mean +/- standard error of the mean) and myocardial blood flow in the anterior left ventricle was 2.3 +/- 1.3 ml/100 gm/min. When the LV vent was opened, vent flow was 35.9 +/- 3.5 ml/min and myocardial blood flow fell to 0.3 +/- 0.2 ml/100 gm/min. Right ventricular (RV) vent flow was absent except when the LV vent was occluded, and this RV vent flow was abolished by ligating the coronary arteries. With bronchial artery ligation, LV vent flow ceased and myocardial blood flow was virtually absent. These studies demonstrate that myocardial blood flow does occur during induced ischemia, but that the source of this blood flow is primarily through systemic-pulmonary channels. True noncoronary collateral myocardial blood flow was virtually nonexistent.     

Preservation of myocardial high-energy phosphates with vagal stimulation and hypothermic cardioplegia

We examined three methods of inducing hypothermic cardioplegic arrest and related each to preservation of high-energy phosphates. Levels of adenosine triphosphate (ATP) and creatine phosphate (CP) in baseline rat hearts were compared with levels found after vagal stimulation combined with cardioplegia containing 15 mEq of potassium chloride (KCl) per liter, cardioplegia with 15 mEq of KCl per liter alone, and cardioplegia with 30 mEq of KCl per liter alone. Vagal stimulation produced complete electromechanical arrest in a shorter time than either 15 or 30 mEq of KCl alone (p less than 0.001 for both cardioplegic solutions compared with vagal stimulation), with fewer ventricular beats after ischemia than cardioplegic solution containing 15 or 30 mEq of KCl (p less than 0.001 and less than 0.01, respectively). Levels of ATP and CP, although less than baseline levels (p less than 0.01 and less than 0.001, respectively), were greater with vagal stimulation than with either 15 or 30 mEq of KCl (p less than 0.001 and less than 0.05, respectively, for ATP and p less than 0.001 for both CP levels). Furthermore, when all groups were combined, ATP and CP levels were found to correlate negatively with arrest time (r = -0.851 and -0.788, respectively; both r values significant at p less than 0.01) and with the number of ventricular beats after ischemia (r = -0.927 and -0.851, respectively; both r values significant at p less than 0.01). We conclude that electromechanical work quantified as time to arrest after aortic cross-clamping and as number of ventricular beats after ischemia correlates negatively with ATP and CP levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

The Effect of Acute Coronary Artery Occlusion during Cardioplegic Arrest and Reperfusion on Myocardial Preservation

A study was undertaken to evaluate the effect of acute occlusion of a coronary artery during cardioplegic arrest on myocardial preservation and to elucidate the influence of reestablishment of flow versus continued occlusion during the phase of myocardial reperfusion. Coronary occlusion was simulated, and myocardial viability was determined by measuring tissue levels of adenosine triphosphate (ATP) and creatine phosphate (CP) in biopsies of the posterior left ventricular wall. Eighteen pigs were divided into three equal groups consisting of animals with (1) patent right coronary arteries during arrest and reperfusion, (2) occluded right coronary arteries during arrest and patent during reperfusion, and (3) occluded right coronary arteries during arrest and reperfusion.The results of ATP and CP measurements showed that while poorer protection was afforded during two-hour arrest when the coronary artery was occluded, the risk of damage was much greater during reperfusion. Failure to restore adequate blood flow by retention of occlusion caused a concurrent decrease in ATP and CP levels below prescribed limits of myocardial tolerance. When occlusion occurs in the clinical setting, impeding cardioplegia and reperfusion, the importance of revascularization is emphasized.     

Electrophysiological evaluation of retrograde cardioplegia--experimental study of efficacy for the right ventricle

Recently, coronary artery bypass grafting operations for patients with total proximal multi-vessel coronary obstructions are increased. In these cases, antegrade cardioplegia through the aortic root has been applied as usual. But it seems to be difficult to deliver cardioplegic solution to myocardium uniformly beyond coronary stenosis. Retrograde coronary sinus cardioplegia in the presence of proximal coronary artery obstruction could maintain improved cardioplegic delivery and satisfactory myocardial protection. Because of the limitation of antegrade cardioplegia, retrograde cardioplegic technique has, once again, been cited as a reasonable alternative to antegrade cardioplegia. But on the other hand, retrograde cardioplegia includes the potential for relatively inadequate preservation of right ventricle based on the venous drainage communication to the coronary sinus. The object of the present work is mainly to evaluate the efficacy of retrograde coronary sinus cardioplegic technique for right ventricle by electrophysiological method. Thirty-six adult mongrel dogs divided three groups. Sixteen animals (Group I) received GIK cardioplegia through the coronary sinus, thirteen animals (Group II) received GIK added diltiazem cardioplegia through the same way, and seven animals (Group III) received GIK cardioplegia through aortic root. No large temperature gradients of myocardium between right and left ventricle in each group and also temperature gradients of right ventricle between three groups have been observed. The time duration from starting of injection of cardioplegia to disappear the electrical activity in right and left ventricle were 11.4 +/- 8.2, 3.4 +/- 1.2 minutes in group I, 2.9 +/- 1.5, 2.2 +/- 1.4 minutes in group II, and 0.9 +/- 0.4, 0.9 +/- 0.2 minutes in group III. The time duration from starting of injection of cardioplegia to reappear the electrical activity in right and left ventricle were 6.4 +/- 8.7, 13.4 +/- 7.9 minutes in group I, 20.0 +/- 3.5, 21.3 +/- 1.6 minutes in group II and 18.0 +/- 5.5, 18.7 +/- 4.5 minutes in group III. Unipolar peak-to-peak amplitude (UPPA) analysis reveals the condition of myocardial preservation during ischemic arrest and we compared preischemic UPPA with post-ischemic UPPA. In group I, UPPA declined of 44.1 +/- 29.3% in right ventricle and 72.7 +/- 27.6% in left ventricle, in group II, 78.7 +/- 28.7%, 81.9 +/- 23.6%, in group III, 71.4 +/- 18.7%, 76.7 +/- 9.89%. Analysis of ultrastructural changes in the myocardium are shown that injury was most manifest in the right ventricle of group I, but in group II, ultrastructure of right ventricle maintained nearly normal condition.(ABSTRACT TRUNCATED AT 400 WORDS)     

Retrograde coronary sinus perfusion prevents infarct extension during intraoperative global ischemic arrest

To determine whether continuous infusion of cardioplegia retrograde through the coronary sinus could improve the salvage of infarcting myocardium, 54 pigs were utilized in a region at risk model. All hearts underwent 30 minutes of reversible coronary artery occlusion, and were divided into six groups. Group 1 served as controls and underwent two hours of coronary reflow without global ischemic arrest. The remaining five groups were subjected to 45 minutes of cardioplegia-induced hypothermic arrest followed by two hours of normothermic reflow. Group 2 had a single infusion of crystalloid cardioplegia, and Group 3 received an oxygenated perfluorocarbon cardioplegic solution initially and again after 20 minutes of ischemia. After initial cardiac arrest with crystalloid cardioplegia, all hearts in Groups 4, 5, and 6 underwent a continuous infusion of a cardioplegic solution retrograde through the coronary sinus. Group 4 received a nonoxygenated crystalloid cardioplegic solution, Group 5 received an oxygenated crystalloid cardioplegic solution, and Group 6 received an oxygenated perfluorocarbon cardioplegic solution. With results expressed as the percent of infarcted myocardium within the region at risk, Group 2 hearts, which received only antegrade cardioplegia, had a mean infarct size of 44.8 +/- 6.3%, a 2.2-fold increase over controls (p less than 0.05). While antegrade delivery of oxygenated perfluorocarbon cardioplegia (Group 3) and coronary sinus perfusion with nonoxygenated crystalloid cardioplegia (Group 4) limited infarct size to 33.6 +/- 4.7% and 35.3 +/- 5.4%, respectively, only oxygenated cardioplegia delivered retrograde through the coronary sinus (Groups 5 and 6) completely prevented infarct extension during global ischemic arrest.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of varied cardioplegic perfusion pressure on myocardial preservation with critical coronary stenosis

Inadequate delivery of cardioplegic solution distal to coronary artery stenosis may result in increased injury during ischemic arrest. This study was performed to determine the effects of cardioplegic perfusion pressure on cardioplegia delivery and myocardial preservation in hearts with critical coronary artery stenosis. Twenty dogs underwent 90 minutes of cold potassium cardioplegic arrest with partial occlusion of the circumflex coronary artery. Group 1 received cardioplegia at 50 mm Hg pressure, Group 2 at 90 mm Hg pressure, and Group 3 at 130 mm Hg pressure. It was found that cooling rates were 5.4 degrees, 9.1 degrees, and 18.2 degrees C per minute in the nonischemic area (p = 0.004) and 2.0 degrees, 4.5 degrees, and 7.9 degrees C in the ischemic area (p = 0.008) in Groups 1, 2, and 3, respectively. Total of cardioplegic solution flows were 86, 188, and 262 ml per minute per 100 gm in Groups 1, 2, and 3, respectively (p = 0.001). However, flow did not differ significantly between groups in the ischemic area. Rate of rise of left ventricular (LV) pressure decreased significantly in Groups 1 and 2 but not in Group 3 (p = 0.002). Other measured variables did not differ significantly between groups, although LV function curves showed less deterioration in the high-pressure groups. It is concluded that higher cardioplegic perfusion pressure resulted in more rapid cooling in normal and ischemic areas and slightly better preservation of ventricular function as measured by some indexes. However, preservation was generally good for each of the pressures for up to 90 minutes of ischemia when the septum was consistently cooled to 10 degrees C.     

Improved myocardial preservation during global ischemia by continuous retrograde coronary sinus perfusion

To investigate whether retrograde continuous low-pressure perfusion of the coronary sinus could deliver cardioplegic solutions with oxygen and substrate beyond stenoses and result in improved myocardial preservation, we subjected 41 canine hearts to 90 minutes of ischemia with an occlusion on the circumflex coronary artery. There were four groups: Group I, antegrade (aortic root) crystalloid cardioplegia every 30 minutes during ischemia; Group II, antegrade plus topical cooling; Group III, continuous retrograde perfusion; Group IV, same as Group III, with an oxygenated perfluorocarbon. All solutions had a PO2 of 400 to 500 mm Hg. Intramyocardial oxygen and carbon dioxide tensions (PO2 and PCO2) and mean myocardial temperatures were monitored during ischemia, and left ventricular (LV) function was assessed before ischemia and after reperfusion. After global ischemia, the circumflex occlusion was released and the hearts reperfused. Following 60 minutes of reperfusion, isovolumic developed pressure returned to 36% +/- 4% and 41% +/- 5% of preischemic levels, respectively, in Groups I and II. By contrast, Groups III and IV (retrograde perfusion) had a significantly greater percent of recovery (78% +/- 5% and 73% +/- 5%). Circumflex area intramyocardial PO2 fell 20 and 25 mm Hg below preischemic levels in Groups I and II during ischemia, whereas in Group III, intramyocardial PO2 in the circumflex region remained near preischemic levels, and in Group IV, it rose 19 mm Hg. Mean myocardial temperature during ischemia in the circumflex area was significantly higher in Group I than in Groups II, III, and IV. Peak intramyocardial PCO2 in the circumflex region was significantly less in the retrogradely perfused hearts. Retrograde coronary sinus perfusion resulted in significant improvement in recovery of LV function, uniform myocardial cooling, normal intramyocardial PO2, and less intramyocardial PCO2 accumulation, despite the presence of a total circumflex coronary artery occlusion.     

Right ventricular function: a comparison between blood and crystalloid cardioplegia

Blood cardioplegia resulted in better left ventricular (LV) function than crystalloid cardioplegia after elective coronary artery bypass operations. However, most methods of cardioplegic delivery may not adequately cool and protect the right ventricle, and right ventricular (RV) dysfunction may limit hemodynamic recovery. Therefore, RV and LV temperatures were measured intraoperatively and RV and LV function were evaluated postoperatively in 80 patients with double-vessel or triple-vessel coronary artery disease who were randomized to receive either blood cardioplegia or crystalloid cardioplegia. Myocardial performance, systolic function, and diastolic function were assessed with nuclear ventriculography by evaluating the response to volume loading. Preoperatively the groups were similar. Intraoperatively, blood cardioplegia resulted in significantly warmer LV and RV temperatures (left ventricle: 15.5 degrees +/- 0.2 degrees C with blood cardioplegia and 12.6 degrees +/- 0.3 degrees C with crystalloid cardioplegia [p less than .0001]; right ventricle: 18.3 degrees +/- 0.3 degrees C with blood cardioplegia and 15.1 degrees +/- 0.3 degrees C with crystalloid cardioplegia [p less than .0001]). Postoperatively, blood cardioplegia resulted in better LV performance (higher LV stroke work index at a similar LV end-diastolic volume index [EDVI]) (p = .01), better LV systolic function (similar systolic blood pressures at smaller LV end-systolic volume indexes [ESVI]), (p = .04), and improved LV diastolic function (lower left atrial pressures at similar LVEDVIs) (p = .03).(ABSTRACT TRUNCATED AT 250 WORDS)     

Myocardial protection by retrograde cardioplegia in arterial switch operation

Retrograde coronary sinus perfusion of cold cardioplegic solution was evaluated in infants undergoing an arterial switch operation for transposition of the great arteries. To assess myocardial injury during ischemia, hemodynamic measurements were conducted at weaning from cardiopulmonary bypass and a postoperative assay of creatine kinase isoenzyme MB was performed. In 22 infants with retrograde coronary sinus perfusion, the initial cardioplegic infusion was performed through the aortic root and additional infusion was repeated every 30 minutes by retrograde coronary sinus perfusion. The other 11 infants received additional solution by antegrade selective coronary artery perfusion. The aortic cross-clamp time in the retrograde coronary sinus perfusion group was significantly shorter than that in the antegrade selective coronary perfusion group (128 +/- 19 versus 143 +/- 21 minutes, p less than 0.05). There were no significant differences between the two groups in terms of postoperative hemodynamic variables and enzyme indexes. Eight neonates in the retrograde coronary sinus perfusion group also exhibited enzymatic and hemodynamic indexes similar to those of older infants. These results suggested that retroperfusion of cardioplegic solution was a safe and useful means of myocardial protection in infants and neonates because of the simplification of the operative procedure and the avoidance of traumatic injury to the coronary ostia.     

Myocardial perfusion during warm antegrade and retrograde cardioplegia: a contrast echo study.

BACKGROUND: We evaluated distribution of warm antegrade and retrograde cardioplegia in patients undergoing coronary artery bypass grafting (CABG). METHODS: Myocardial perfusion was evaluated pre- and post-CABG using transesophageal echocardiography with injection of sonicated albumin microbubbles (Albunex) during warm antegrade and retrograde cardioplegia. The left ventricle (LV) was evaluated in five segments and the right ventricle (RV) was evaluated in two segments. Segmental contrast enhancement was graded as absent (score = 0), suboptimal or weak (score = 1), optimal or excellent (score = 2), or excessive (score = 3). RESULTS: Pre-CABG cardioplegic perfusion correlated weakly with severity of coronary artery stenoses (r = -0.331 and 0.276 for antegrade and retrograde cardioplegia, respectively). Antegrade cardioplegia administration resulted in 98% and 96% perfusion to the left ventricle pre- and post-CABG, respectively. Retrograde cardioplegic administration resulted in reduced LV perfusion, with 86% (p = 0.032 from antegrade) and 59% (p<0.001 from antegrade) pre- and post-CABG, respectively. The average LV perfusion score (mean +/- SEM) was greater with antegrade than retrograde cardioplegia both pre-CABG (1.93+/-0.04 vs. 1.53+/-0.11, p<0.001) and post-CABG (1.63+/-0.07 vs. 1.19+/-0.13, p = 0.004). RV perfusion was poor with both techniques pre-CABG, but improved significantly with antegrade cardioplegia post-CABG. CONCLUSIONS: We conclude that warm antegrade cardioplegia results in better left ventricular perfusion than warm retrograde cardioplegia. Right ventricular cardioplegic perfusion was suboptimal, but the best delivery was achieved with antegrade cardioplegia after coronary bypass. We therefore recommend construction of the saphenous vein graft to the right coronary artery early in the operative procedure.     

Free radical scavengers improve functional recovery of stunned myocardium in a model of surgical coronary revascularization

This study examined whether treatment with the oxygen free radical scavengers, superoxide dismutase and catalase, could improve functional recovery in hearts subjected to regional ischemia and global cardioplegic arrest. Regional left ventricular (LV) function was assessed in open chest pigs with sonomicrometry and micromanometry to calculate an index of regional work from the LV pressure-segment length relationship. After measuring baseline preischemic function, the left anterior descending artery was occluded, creating a region-at-risk in 20% of the LV mass. Cardiopulmonary bypass was begun 15 minutes after initiation of regional ischemia and was followed immediately by cardioplegic arrest for 45 minutes, after which time the coronary artery occluder was removed to simulate coronary revascularization. Starting just before removal of the aortic cross-clamp and continuing for the first 30 minutes of reflow, animals received an aortic root infusion of either superoxide dismutase (3600 U/kg) and catalase (20,000 U/kg) or a control saline solution infusion. In each group, seven animals were successfully weaned from cardiopulmonary bypass without inotropic support. After 2 hour of reperfusion, the recovery of baseline function in the region-at-risk was 44% +/- 7% in the treated animals and 4% +/- 13% in the untreated animals (p less than 0.05). In this experimental model, oxygen free radical scavengers were effective in preserving functional recovery in regionally ischemic myocardium reperfused under conditions simulating surgical revascularization in the setting of acute myocardial ischemia.     

Influence of coronary anatomy and reimplantation on the long-term outcome of the arterial switch.

BACKGROUND: Abnormal coronary artery anatomy is reported to have a significant influence on the outcome of the arterial switch operation. This study examines the impact of coronary anatomy and the occurrence of late coronary obstruction on left ventricular (LV) function and long-term outcome. METHODS: Coronary artery anatomy, of 170 patients after arterial switch operation (1977-1999), was determined based on operative reports and pre-operative aortograms. Current status was evaluated using ECGs, echocardiograms, scintigraphy, and post-operative coronary angiograms. RESULTS: In 133/170 patients, coronary artery anatomy consisted of an anterior descending (LAD) and circumflex artery (Cx) from the left sinus and the right coronary artery (RCA) from the right or posterior sinus. The left coronary had an intramural initial course in two of these patients. Fifteen patients had the LAD from the left and Cx and RCA from the right sinus; eight had LAD and RCA from one sinus and Cx from the other; four had single ostium; and three had three separate ostia. Four patients had complex patterns and four patients had a supra commissural coronary. To date, follow-up angiography was performed in 59 patients. Surgical coronary sequellae were found in five patients. Two patients had an occluded left ostium. Initially, they were asymptomatic but showed polymorphic ventricular extrasystoles on ECG and moderate LV dysfunction with large irreversible perfusion defects on scintigraphy. Both patients developed ventricular fibrillation at the age of 14 years. One patient did not survive. The other patient required implantation of a defibrillator. One patient has an occluded RCA, one patient has stenosis of the right ostium and one patient has multiple tortuous collaterals without obstruction of a major branch. In the latter three patients, coronary sequellae were not suspected on ECG, echo, or scintigraphy and were only found on follow-up angiography. Retrograde collateral flow was noted in all three occluded coronaries. LV dysfunction, with normal coronaries, was noted in three patients. All, of these patients, had peri-operative ischaemia suggesting failure of myocardial protection. Two are now asymptomatic with mild LV dysfunction. One patient continues to have severe myocardial dysfunction and secondary aortic insufficiency. A Ross-like procedure was performed placing the original aortic valve in the neo-aortic root. Coronary artery anatomy did not influence early survival or late coronary sequellae. CONCLUSION: Abnormal coronary anatomy was not a determinant of outcome in our study. Surgical coronary obstruction is independent of original anatomy. It can be almost silent and is potentially fatal. Follow-up angiography must be considered in all patients after the arterial switch operation.     

Myocardial protection by retrograde cardioplegic perfusion in the presence of acute coronary artery obstruction. An experimental study.

To investigate retrograde delivery of cardioplegic solutions as a means of enhancing myocardial protection in the presence of coronary artery occlusion, a two-part experimental model was devised. In part 1 (in vitro) the possibility of retroperfusing the entire myocardium during acute occlusion of the left anterior descending artery (LAD) was assessed. In part 2 (in vivo) acute LAD occlusion was performed in dogs, and during 2 hours of aortic cross-clamping crystalline cardioplegic solution was infused at 20-minute intervals. In group I the infusion was antegrade, via the aortic root, and in group II it was retrograde, via the coronary sinus. Thereafter the LAD snare was released and the dogs were weaned from bypass. Delivery of cardioplegia through the aortic root was associated with depression of ventricular function, poor myocardial cooling and severe cellular damage. With the retrograde procedure there was significantly improved recovery of left ventricular function, uniform myocardial cooling and better preservation of cellular morphology.     

Oxygen utilization during isovolumic pressure-volume loading: effects of prolonged extracorporeal circulation and cardioplegic arrest

In canine hearts supported by cardiopulmonary bypass, isovolumic peak developed pressure (PDP, mm Hg) and myocardial oxygen consumption (MVO2, ml O2 X 10(-2)/beat/100 gm left ventricular [LV] weight) were determined at 5-ml increments of LV balloon inflation before and after either 2 hours of potassium cardioplegic arrest (ischemia, N = 7) or a comparable period of normothermic perfusion without ischemia (control, N = 6). The sensitivity of MVO2 as a marker of ischemic injury was compared with preservation of both adenosine triphosphate (ATP) stores and systolic pump function. Over a physiological range of end-diastolic volumes (5 to 35 ml) and end-diastolic pressures (0 to 18 mm Hg), the Frank-Starling curves were not depressed following both cardioplegic arrest and prolonged nonischemic perfusion. Although ATP stores decreased by 26% and 22% (ischemia and control groups, respectively; not significant), these levels did not distinguish the effects of cardioplegic arrest from prolonged perfusion. At the preinterventional measurement in both groups, PDP between 50 and 200 correlated with MVO2 from 3.0 to 10.0 (r = +0.84). Following cardioplegic arrest, postischemic MVO2 increased 137 +/- 6% when measured over the PDP range of 75 to 200 mm Hg (p less than 0.01). This change was not evident at a PDP of less than 75, in the empty beating heart, or in control hearts subjected to nonischemic extracorporeal perfusion. These data suggest that increased utilization of oxygen to develop physiological pressures may be a more sensitive indicator of ischemic injury than shifts in the pressure-volume relationship or depletion of adenine nucleotide stores.     

Left circumflex coronary aneurysm with separated left main trunk

We report a left circumflex coronary aneurysm associated with separated left main coronary trunks (LMT). A 66-year-old man was admitted to our hospital for further examination of dyspnea on effort. He has been performed maintenance hemodialysis since 1999 for chronic renal failure. Coronary angiography and multislice spiral computed tomography (CT) revealed an unusual coronary anatomic variance in which separate origins of the left anterior descending (LAD) and left circumflex (LCx) coronary arteries arose from the left coronary aortic sinus. Furthermore, these images of the LCx revealed an aneurysm 2 cm in diameter and 99% stenosis at the proximal of side of the aneurysm. Under cardioplegic arrest, the aneurysm was ligated and coronary artery bypass grafting (left thoracic artery to posterolateral branch) was performed. The patient was discharged at the 20th postoperative day without any complication.     

Warm retrograde cardioplegia. Protection of the right ventricle in mitral valve operations.

Hypothermia is believed to be the most important aspect of successful myocardial protection with retrograde coronary sinus cardioplegia. Because nutritive capillary flow to the right ventricle and septum is thought to be diminished with retrograde perfusion, these areas of the myocardium are considered at higher risk for intraoperative deterioration without the added protection of hypothermia. Recently we introduced warm aerobic arrest as an alternative to conventional methods of myocardial protection. We present our clinical results in 37 patients with mitral valve disease (+/- aortic valve, aortic root, or coronary artery disease) who underwent various cardiac procedures for which warm blood cardioplegic solution was delivered continuously via the coronary sinus after antegrade arrest. Thirty-five of the patients were in New York Heart Association class III or IV, and 19 patients had grade 3 or grade 4 left ventricular function. Sixteen patients had pulmonary hypertension, three with suprasystemic pressures, and marked right ventricular hypertrophy. Two patients had associated left ventricular hypertrophy. Nearly all patients returned to normal sinus rhythm shortly after removal of the aortic crossclamp, and they were easily discontinued from cardiopulmonary bypass even with crossclamp times of 3 hours. The 30-day hospital mortality rate was 2.7%. The perioperative myocardial infarction rate was 5.4%, and the prevalence of low-output syndrome was 10.8%. The results suggest that retrograde coronary sinus perfusion of blood cardioplegic solution at 37 degrees C is an effective method of myocardial protection even in patients with pulmonary hypertension at high risk for right ventricular failure. Its efficacy in this circumstance does not reside in its ability to deliver hypothermia.     

Cold blood as the vehicle for potassium cardioplegia

Cold blood with potassium, 34 mEq/L, was compared with cold blood and with a cardioplegic solution. Three groups of 6 dogs had 2 hours of aortic cross-clamp while on total bypass at 28 degrees C with the left ventricle vented. An initial 5-minute coronary perfusion was followed by 2 minutes of perfusion every 15 minutes for the cardioplegic solution (8 degrees C) and every 30 minutes for 3 minutes with cold blood or cold blood with potassium (8 degrees C). Hearts receiving cold blood or cold blood with potassium had topical cardiac hypothermia with crushed ice. Peak systolic pressure, rate of rise of left ventricular pressure, maximum velocity of the contractile element, pressure volume curves, coronary flow, coronary flow distribution, and myocardial uptake of oxygen, lactate, and pyruvate were measured prior to ischemia and 30 minutes after restoration of coronary flow. Myocardial creatine phosphate (CP), adenosine triphosphate (ATP), and adenosine diphosphate (ADP) were determined at the end of ischemia and after recovery. Changes in coronary flow, coronary flow distribution, and myocardial uptake of oxygen and pyruvate were not significant. Peak systolic pressure and lactate uptake declined significantly for hearts perfused with cold blood but not those with cold blood with potassium. ATP and ADP were lowest in hearts perfused with cardioplegic solution, and CP and ATP did not return to control in any group. Heart water increased with the use of cold blood and cardioplegic solution. Myocardial protection with cold blood with potassium and topical hypothermia has some advantages over cold blood and cardioplegic solution.