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.     

Importance of topical hypothermia during heterogeneous distribution of cardioplegic solution

Recent studies have suggested that topical hypothermia may be unnecessary during coronary bypass operations because of possible pulmonary complications resulting from phrenic nerve damage. This study was undertaken to determine whether topical hypothermia is necessary for optimal myocardial protection when distribution of the cardioplegic solution is heterogeneous because of coronary occlusions. Twenty pigs were subjected to 120 minutes of ischemic arrest with multidose potassium crystalloid cardioplegia (4 degrees C). During arrest, the mid-left anterior descending coronary artery was occluded with a snare that was released on reperfusion. Ten of these pigs received topical hypothermia and 10 others served as controls. Hearts protected with topical hypothermia had lower temperatures in the left anterior descending (7.0 degrees +/- 0.7 degree C versus 18.5 degrees +/- 0.5 degree C; p less than 0.05) and circumflex regions (8.9 degrees +/- 0.5 degree C versus 15.5 degrees +/- 0.5 degree C; p less than 0.05). The pH values were higher in hearts protected with topical hypothermia in both the left anterior descending (7.36 +/- 0.09 versus 6.73 degrees +/- 0.07; p less than 0.05) and circumflex regions (7.40 +/- 0.07 versus 7.05 +/- 0.07; p less than 0.05). Topical hypothermia also resulted in better preservation of postischemic stroke work index (0.64 +/- 0.06 versus 0.40 +/- 0.08 gm-m/kg; p less than 0.05) and wall motion scores (1.0 +/- 0.3 hypothermia versus 1.8 +/- 0.4 no hypothermia; p less than 0.05). We conclude that topical hypothermia affords maximal myocardial protection when coronary occlusions are present and should be used during all coronary operations.     

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)     

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)     

Studies of retrograde cardioplegia. I. Capillary blood flow distribution to myocardium supplied by open and occluded arteries

This study defines the nutritive (i.e., capillary) distribution of blood cardioplegic solutions delivered via retrograde and antegrade techniques to muscle supplied by open and occluded coronary arteries where myocardial segments are in jeopardy of inadequate cardioplegic protection. Open-chest anesthetized dogs were studied by mixing radioactive microspheres (15 +/- 5 microns) with a blood cardioplegic solution and administering cardioplegia either into the coronary sinus or into the proximal aorta with the left anterior descending coronary artery open or occluded (30% +/- 2% area at risk). Nutritive flow (i.e., percentage of delivered 15 microns microspheres trapped in myocardial capillaries) during retrograde infusions averaged 65% versus 87% with antegrade cardioplegia (p less than 0.05). Retrograde and antegrade cardioplegic nutritive flow to all left ventricular regions was comparable with the left anterior descending coronary artery open (65 versus 82 ml/100 gm/min, p greater than 0.05), and both methods provided preferential hyperperfusion of subendocardial muscle (endocardial/epicardial ratios 1.6 and 1.5, respectively). Nutritive flow to muscle supplied by the occluded left anterior descending coronary artery was preserved better by retrograde than antegrade cardioplegia (35 versus 5 ml/100 gm/min, p less than 0.05). Preferential subendocardial hyperperfusion was maintained during retrograde cardioplegia (52 ml/100 gm/min, endocardial/epicardial ratio 1.6), but flow was redistributed away from subendocardial muscle with antegrade cardioplegia (less than 2 ml/100 gm/min, endocardial/epicardial, 0.29, p less than 0.05). Left ventricular flow was reduced markedly during retrograde infusion with the left anterior descending coronary artery open or occluded (23 and 12 ml/100 gm/min), but septal cooling was superior to antegrade cardioplegia (15 degrees +/- 1 degree C versus 20% +/- 3%, p less than 0.05) despite near-normal antegrade septal flow (the left anterior descending coronary artery was ligated beyond the first septal branch). Right ventricular nutritive flow was only 7 ml/100 gm/min during retrograde coronary sinus perfusion and was maintained normally with antegrade cardioplegia.(ABSTRACT TRUNCATED AT 400 WORDS)     

Improved distribution of antegrade cardioplegic solution with simultaneous coronary sinus occlusion following acute coronary artery occlusion.

This study was designed to evaluate the distribution of cardioplegic solution infused antegradely with simultaneous coronary sinus occlusion. After 1 hr LAD occlusion, sheep were placed on cardiopulmonary bypass. Hearts were arrested with 300 ml of cold cardioplegia and replenished with two additional doses. In group I (n = 10), antegrade cardioplegia (ACP) was given alone; in group II (n = 9), ACP was given in combination with simultaneous coronary sinus occlusion. Microspheres were infused into the cardioplegic line to determine the antegrade distribution of the solution, while a different microsphere was injected into the anterior interventricular vein to detect the venous backflow of the solution. The data showed that myocardium distal to LAD occlusion in group II received more antegrade (0.17 +/- 0.02 versus 0.06 +/- 0.02 ml/g/min, P less than 0.01, in subendocardium; and 0.15 +/- 0.03 versus 0.09 +/- 0.02 ml/g/min, P = NS, in subepicardium) and retrograde (2181 +/- 455 versus 0 counts/g/min, P less than 0.01, in subendocardium; and 2,146 +/- 527 versus 0 counts/g/min, P less than 0.01, in subepicardium) distribution of cardioplegic solution in comparison to group I. We therefore conclude that simultaneous coronary sinus occlusion significantly improves the distribution of antegrade cardioplegic solution to the regionally occluded myocardium by increasing collateral flow as well as venous backflow.     

A new technique for delivering antegrade/retrograde blood cardioplegia without right heart isolation

We report our updated experience with combined antegrade/retrograde cardioplegia using a self-inflating/deflating balloon cannula that allows rapid transatrial retrograde coronary sinus cannulation (10-15 s) without right heart isolation. This permits routine single venous cannulation and optimizes myocardial protection when combined with antegrade cardioplegia. Two hundred fifty-five consecutive patients underwent antegrade/retrograde cardioplegia. Initial antegrade blood cardioplegia caused immediate arrest (less than 1 min), and the cardioplegic dose was divided equally between antegrade and retrograde delivery. Included are 173 isolated CABG patients (39 with either extending infarction, cardiogenic shock, or ejection fraction less than 20%), and 37 coronary reoperations, 67 with aortic and/or mitral valve procedures, 3 with arrhythmia surgery, and 7 children (VSD, Rastelli, Konno, etc). Septal temperature in patients with LAD occlusion fell to 11.6 degrees C +/- 0.5 after retrograde vs only 16.1 degrees C +/- 3 after antegrade cardioplegia (p less than 0.05). Overall hospital mortality was 2.8% and no complications followed transatrial retrograde coronary sinus cannulation. Antegrade/retrograde cardioplegia allowed retrograde flushing of debris in redo coronary operations, produced immediate arrest with low cardioplegic volumes, improved cardioplegic distribution during IMA grafting, allowed aortic and mitral valve procedures to proceed uninterrupted, and ensured distribution in unforeseen aortic insufficiency. Antegrade/retrograde cardioplegia is now used routinely in all adult and in many pediatric operations because of its speed, safety, and simplicity.     

Reversal of reperfusion injury after ischemic arrest with pressure-controlled intermittent coronary sinus occlusion

Recent experimental studies have shown that pressure-controlled intermittent coronary sinus occlusion effectively reduces both infarct size and myocardium at risk after coronary artery occlusion. This study was undertaken to determine whether this modality was equally effective in altering reperfusion damage after a period of ischemic arrest. Fourteen pigs were placed on cardiopulmonary bypass and subjected to 2 hours of ischemic arrest with multidose potassium crystalloid cardioplegia supplemented with topical and systemic hypothermia (28 degrees C). During arrest, the mid-left anterior descending artery was occluded with a snare, which was released immediately after aortic unclamping. In seven pigs, a 7F balloon-tipped catheter was positioned in the coronary sinus and pressure-controlled intermittent coronary sinus occlusion was performed for 60 minutes after aortic unclamping. Seven other pigs served as controls. Parameters measured included stroke work index, ejection fraction, and myocardial pH in the distribution of the distal left anterior descending artery. Pigs treated with pressure-controlled intermittent coronary sinus occlusion had a significantly higher myocardial pH (6.99 +/- 0.06 versus 6.67 +/- 0.05, p less than 0.01), ejection fraction (50% +/- 2% versus 33% +/- 6%, p less than 0.01), and stroke work index (0.87 +/- 0.07 versus 0.61 +/- 0.05 gm-m/kg, p less than 0.01) after 60 minutes of reperfusion compared with those of the group not treated in this way. We conclude that pressure-controlled intermittent coronary sinus occlusion effectively reverses reperfusion damage after periods of ischemic arrest.     

A new simplified method of optimizing cardioplegic delivery without right heart isolation. Antegrade/retrograde blood cardioplegia

We report our initial experience with antegrade/retrograde cardioplegia using a self-inflating/deflating balloon cannula that allows rapid transatrial retrograde cannulation of the coronary sinus (10 to 15 seconds) without right heart isolation and permits routine single venous cannulation. We subjected 141 consecutive adult patients and nine children to antegrade/retrograde cardioplegia using rapid transatrial insertion of the Retroplegia cannula (Research Medical, Inc., Salt Lake City, Utah). Single venous cannulation was used in 116 patients having coronary artery bypass grafting or aortic valve replacement, or both. Initial antegrade blood cardioplegia caused immediate arrest (less than 1 minute) and the cardioplegic dose was divided equally between antegrade and retrograde delivery. Included are 95 patients having isolated bypass grafting (34 with extending infarction, cardiogenic shock, or ejection fraction less than 20%); 19 having coronary reoperations, 42 with aortic or mitral valve procedures, or both; and nine children having repair of congenital defects (e.g., repair of ventricular septal defect, Rastelli operation, Konno operation). Septal temperature in patients with occlusion of the left anterior descending coronary artery fell to 11.5 degrees +/- 0.5 degrees C after retrograde cardioplegia versus only 16 degrees +/- 3 degrees C after antegrade cardioplegia (p less than 0.05). The overall hospital mortality rate was 2% and no complications followed transatrial retrograde cannulation of the coronary sinus.     

Does warm antegrade intermittent blood cardioplegia really protect the heart during coronary surgery?

OBJECTIVE: Intermittent antegrade blood cardioplegia (IABC) has been standardized as a routine technique for myocardial protection in coronary surgery. However, if the myocardium is known to tolerate short periods of ischemia during hypothermic arrest, it may be less tolerant of warm ischemia, so the optimal cardioplegic temperature of intermittent antegrade blood cardioplegia is still controversial. The aim of this study was to compare the effects of warm intermittent antegrade blood cardioplegia and cold intermittent antegrade blood cardioplegia on myocardial pH and different parameters of the myocardial metabolism. METHODS: Thirty patients undergoing first-time isolated coronary surgery were randomly allocated into two groups: group 1 (15 patients) received warm (37 degrees C) intermittent antegrade blood cardioplegia and group 2 (15 patients) received cold (4 degrees C) intermittent antegrade blood cardioplegia. The two randomization groups had similar demographic and angiographic characteristics. Total duration of cardiopulmonary bypass (108+/-17 and 98+/-21 min) and of aortic cross-clamping (70+/-13 and 65+/-15 min) were similar. The cardioplegic solutions were prepared by mixing blood with potassium and infused at a flow rate of 250 ml/min for a concentration of 20 mEq/l during 2 min after each anastomosis or after 15 min of ischemia. Intramyocardial pH was continuously measured during cardioplegic arrest by a miniature glass electrode and values were corrected by temperature. Myocardial metabolism was assessed before aortic clamping (pre-XCL), 1 min after removal of the clamp (XCL off) and 15 min after reperfusion (Rep) by collecting coronary sinus blood samples. All samples were analyzed for lactate, creatine kinase (MB fraction), myoglobin and troponin I. Creatine kinase and troponin I were also daily evaluated in peripheral blood during 6 days post-operatively. RESULTs: The clinical outcomes and the haemodynamic parameters between the two groups were identical. In group 1, XCL off and Rep were associated with higher coronary sinus release of lactate (5.5 +/- 1.8 and 2.2 +/- 0.5 mmol/l) than in group 2 (2.0 +/- 0.7 and 1.6 +/- 0.3 mmol/l, P < 0.05). Mean intramyocardial pH was lower in group 1 (7.23 +/- 0.08) than in group 2 (7.65 +/- 0.30, P < 0.05). There were no significant differences between the two groups with respect of creatine kinase (MB fraction) either after Rep or during the post-operative period. Lower coronary sinus release of myoglobin was detected at Rep in group 1 (170 +/- 53 microg/l) than in group 2 (240 +/- 95 microg/l, P < 0.05). At day 1, a lower release of troponin I was found in group 1 (0.11 +/- 0.07 g/ml) compared to group 2 (0.17 +/- 0.07 ng/ml, P < 0.05). CONCLUSION: With regards to similar clinical and haemodynamic results, myocardial protection induced by warm IAEX is associated with more acidic conditions (intramyocardial pH and lactate release) and less myocardial injury (myoglobin and troponin I release) than cold intermittent antegrade blood cardioplegia during coronary surgery.     

Effects of left ventricular venting and distention during heterogenous distribution of cardioplegic solution

The effects of left ventricular venting and distention on myocardial protection during heterogenous distribution of cardioplegic solution remain undefined. This study was undertaken to determine if left ventricular venting enhances and distention impairs myocardial cooling and recovery of global and regional left ventricular function. Twenty-one pigs were placed on cardiopulmonary bypass and subjected to 80 minutes of ischemic arrest with the mid-left anterior descending artery occluded. Hearts were protected with multidose potassium (25 mEq/L) crystalloid cardioplegic solution supplemented with topical (4 degrees C) and systemic (28 degrees C) hypothermia. During arrest, the left ventricle was vented in seven pigs, seven pigs were not vented, and seven others had systemic pump blood infused into the left ventricle to maintain an end-diastolic pressure of 15 mm Hg. Parameters measured included left ventricular temperature, stroke work index, compliance (end-diastolic pressure-end-diastolic volume curves) and wall motion scores (two-dimensional echocardiography). Distended hearts had the lowest mean left ventricular temperature beyond the left anterior descending arterial occlusion (10.1 degrees +/- 1.8 degrees C distended [p less than 0.025 from vented and nonvented groups] versus 14.2 degrees +/- 0.7 degrees C vented versus 15.5 degrees +/- 1.2 degrees C nonvented), the highest postischemic stroke work index (0.78 +/- 0.09 gm-m/kg distended versus 0.62 +/- 0.07 gm-m/kg vented versus 0.66 +/- 0.07 gm-m/kg nonvented at end-diastolic pressure = 10 mm Hg), and the best wall motion scores (0.7 +/- 0.04 distended [p less than 0.025 from vented and nonvented groups] versus 5.5 +/- 1.80 vented versus 4.8 +/- 1.20 nonvented). Postischemic end-diastolic pressure-end-diastolic volume curves were unchanged from preischemic values in each group. We conclude that during heterogenous cardioplegic arrest, left ventricular venting offers no additional myocardial protection and may negate the beneficial effects of moderate (end-diastolic pressure = 15 mm Hg) left ventricular distention.     

Clinical evaluation of pressure-controlled intermittent coronary sinus occlusion: randomized trial during coronary artery surgery

Pressure-controlled intermittent coronary sinus occlusion (PICSO) was evaluated in a randomized trial in 30 patients undergoing bypass surgery. PICSO was applied for one hour during early reperfusion. Myocardial function was determined from short-axis cross-sectional views of intraoperative two-dimensional echocardiography. Changes of sectional and segmental wall motion during extracorporeal circulation were analyzed. Although sectional wall motion did not change significantly, hypokinetic segments were preserved better in PICSO-treated patients than in controls (-1.3 +/- 2.4 versus -9.1 +/- 2.6 delta% fractional area change; p less than 0.04). Although not significant, the same trend was found for normal and severely hypokinetic segments. Cumulative enzyme release was related to coronary sinus occluded pressure (r = 0.94; p less than 0.006), indicating washout of metabolites during PICSO. Three months after operation, functional classification was similarly favorable in both groups. Long-term effects of PICSO cannot be predicted because PICSO was applied only during early reperfusion. We conclude that PICSO is a safe procedure and that its short-term beneficial effects on myocardial function suggest a preservation of myocardial viability.     

A Comparison of Distribution Between Simultaneously or Sequentially Delivered Antegrade/Retrograde Blood Cardioplegia

A bstract Commercially available cardioplegia delivery systems now allow for antegrade (aortic root, coronary ostia, saphenous vein graft) perfusion to occur either sequentially or simultaneous with retrograde (coronary sinus) perfusion. This study was designed to compare the total flow and local distribution of sequential versus simultaneous antegrade/retrograde cardioplegia delivery. Methods : Explanted human hearts diagnosed with idiopathic cardiomyopathy underwent a cold cardioplegic arrest and bicaval cardiectomy. Thirty-seven degree centigrade blood cardioplegia containing colored microspheres was then delivered antegrade (red color) at a pressure of 80 mmHg or retrograde (blue color) at a pressure of 40 mmHg. In the sequential group (n = 6), cardioplegia was delivered antegrade and then retrograde for 2 minutes, respectively. For the simultaneous group (n = 6), cardioplegia was delivered both antegrade and retrograde for 2 minutes. The ventricular myocardium was then sampled at 12 representative sites to determine regional cardioplegic flow. Results : Mean total cardioplegia delivery/minute was 0.69 ± 0.62 mL/g per minute for sequential cardioplegia, and 0.46 ± 0.19 mL/g per minute for simultaneous cardioplegia (p > 0.05, NS). At the 12 ventricular sites sampled, mean regional cardioplegic flow (mL/g per min) was in general slightly greater for sequential delivery. However, this was not statistically significant (p > 0.05, NS). Conclusion : The data suggest that there may be a slight advantage in total cardioplegia delivery and regional cardioplegia delivery when using sequential rather than simultaneous cardioplegia delivery. However, this difference was not statistically significant and is likely not of clinical significance. Therefore, we would recommend using either sequential or simultaneous antegrade/retrograde cardioplegia based upon whichever technique facilitates the conduct of the individual operation.     

The effects of cardioplegic arrest on right atrial function

Atrial electrical and mechanical activity persists during cardioplegic arrest. It has been postulated that atrial ischemia may occur and cause deterioration in atrial function. This study was designed to assess the effect of cardioplegic arrest on right atrial function. Twenty-one pigs were placed on cardiopulmonary bypass (CPB), and the right atrium was isolated from the circulation by snaring both venae cavae and incising the coronary sinus. The tricuspid valve was closed through a small right ventriculotomy, and baseline atrial function was assessed using a compliant balloon in the atrium. Fourteen pigs underwent one hour of cardioplegic arrest (7 with cardioplegia alone [CCA group] and 7 with the addition of topical hypothermia [CCA + TH group]) followed by one hour of normothermic reperfusion. Seven other pigs were placed on CPB for the same period of time (CPB group). Atrial electrical and mechanical activity persisted at 45 beats per minute in the CCA group but was virtually abolished in the CCA + TH group. Cardioplegic arrest caused considerable deterioration in right atrial function (developed pressure, 18.9 +/- 0.8 [baseline] versus 14.1 +/- 0.7 mm Hg; p less than 0.05; first derivative of atrial pressure [dP/dt], 187 +/- 19 versus 134 +/- 25 mm Hg per second; p less than 0.05; 60 minutes of reperfusion and balloon volume of 20 ml). It was not affected by topical cooling. Right atrial developed pressure was maintained, but dP/dt was significantly reduced in the CPB group. This study suggests that cardioplegic arrest does not protect the atrium.     

Protection of the immature heart. Temperature-dependent beneficial or detrimental effects of multidose crystalloid cardioplegia in the neonatal rabbit heart

There are conflicting reports of the detrimental or beneficial effects of hypothermic cardioplegia in the immature heart. We therefore investigated the temperature-dependence of myocardial protection and the ability of single-dose and multidose infusions of cardioplegic solution to protect the immature heart during hypothermic ischemia. Isolated, working hearts (n = 6 per group) from neonatal rabbits (aged 7 to 10 days) were perfused aerobically (37.0 degrees C) for 20 minutes before infusion (2 minutes) with either perfusion fluid (noncardioplegia control) or St. Thomas' Hospital cardioplegic solution and ischemic arrest (for 4, 6, and 18 hours) at various temperatures between 10.0 degrees and 30.0 degrees C. Hearts arrested with cardioplegic solution received either one preischemic infusion only (single-dose cardioplegia) or repeated infusions at intervals of 60 or 180 minutes (multidose cardioplegia). Ischemic arrest with single-dose cardioplegia for 4 hours at 10.0 degrees, 20.0 degrees, 22.5 degrees, 25.0 degrees, 27.5 degrees, and 30.0 degrees C resulted in 96.0% +/- 4.3%, 96.6 +/- 2.5%, 87.0% +/- 3.8%, 71.8% +/- 10.0% (p less than 0.05 versus 10.0 degrees C group), 35.1% +/- 10.3% (p less than 0.01 versus 10.0 degrees C group), and 3.0% +/- 1.9% (p less than 0.04 versus 10.0 degrees C group) recovery of preischemic cardiac output, respectively. With 6 hours of ischemia at 20.0 degrees C, single-dose cardioplegia significantly (p less than 0.01) increased the recovery of cardiac output from 20.9% +/- 13.1% (control) to 76.4% +/- 4.4%, whereas multidose cardioplegia (infusion every 60 minutes) further increased recovery to 97.8% +/- 3.8% (p less than 0.01 versus control and single-dose cardioplegia). In contrast, after 6 hours of ischemia at 10.0 degrees C, cardiac output recovered to 93.4% +/- 1.2% (control) and 92.3% +/- 3.1% (single-dose cardioplegia), whereas multidose cardioplegia reduced recovery to 76.9% +/- 2.2% (p less than 0.01 versus both groups). This effect was confirmed after 18 hours of ischemia at 10.0 degrees C; single-dose cardioplegia significantly increased the recovery of cardiac output from 24.5% +/- 10.9% (control) to 62.9% +/- 13.3% (p less than 0.05), whereas multidose cardioplegia reduced recovery to 0.8% +/- 0.4% (p less than 0.01 versus single-dose cardioplegia) and elevated coronary vascular resistance from 8.90 +/- 0.56 mm Hg.min/ml (control) to 47.83 +/- 9.85 mm Hg.min/ml (p less than 0.01). This effect was not reduced by lowering the infusion frequency (from every 60 to every 180 minutes).(ABSTRACT TRUNCATED AT 400 WORDS)     

Improved myocardial recovery after cardioplegic arrest with an oxygenated crystalloid solution

Possible enhancement of myocardial protection by oxygenation of a crystalloid cardioplegic solution was evaluated in a three-part study. In Part I, canine hearts underwent ischemia followed by heterogeneous cardioplegic arrest for 45 to 60 minutes. Oxygenation led to improved recovery in the left anterior descending region (47% versus 86% recovery, p less than 0.05) (15 minutes of ischemia) and in the circumflex region (9.5% versus 52% recovery, p less than 0.05) (30 minutes of ischemia). Part II was a blind prospective randomized study in 12 patients. It examined creatine kinase, myoglobin, and lactate as well as coronary sinus flow, oxygen consumption, and cardiac work 1 hour after aortic cross-clamping during atrial and during ventricular pacing. No significant difference was demonstrable between control and oxygenated solutions. In Part III, 57 coronary bypass patients were protected with a nonoxygenated solution while 94 patients received an identical oxygenated solution. Twelve-hour creatine kinase levels were similar in the nonoxygenated (9.5 +/- 16 IU, +/- standard deviation) and oxygenated (11 +/- 22 IU) groups if the cross-clamp interval was 28 minutes or less. In patients subjected to longer than 28 minutes of arrest, the 12 hour creatine kinase MB levels were more than twice as high in the nonoxygenated group (26.5 +/- 26 IU) compared to the oxygenated group (9.9 +/- 14 IU, p less than 0.05). In this canine model of heterogeneous cardioplegia and in the routine conduct of coronary bypass operations, oxygenated crystalloid cardioplegia is superior to an identical nonoxygenated solution.     

Retrograde versus antegrade cardioplegia: impact on right ventricular function.

Retrograde cardioplegia administered through the coronary sinus has several documented advantages over antegrade cardioplegia but has been thought to provide inadequate right ventricular myocardial protection. We prospectively compared the effects of retrograde and antegrade cardioplegia on right ventricular performance in patients undergoing myocardial revascularization. Two groups of similar age, extent of disease, and preoperative left ventricular ejection fraction received retrograde (n = 16) or antegrade (n = 14) crystalloid cardioplegia. A right ventricular rapid-response thermistor catheter, previously developed and validated in our institution, was used to measure right atrial pressure, pulmonary artery pressure, right ventricular ejection fraction, end-diastolic volume index, and stroke volume index before bypass (baseline) and at several intervals after bypass. There were no differences in cross-clamp time, heart rate, cardiac enzymes, inotrope requirements, or arrhythmias between the two groups. Right ventricular parameters were equivalent in both groups at all time intervals except 30 minutes after bypass, at which time right ventricular end-diastolic volume index was lower (80 +/- 6 versus 93 +/- 6 mL/m2; p less than 0.05) and right ventricular stroke volume index was higher (35 +/- 3 versus 29 +/- 2 mL/m2, p less than 0.05) in the retrograde group compared with the antegrade group, indicating better right ventricular function with retrograde cardioplegia early after bypass. In both groups, right ventricular end-diastolic volume index was higher than baseline (p less than 0.05) during the first 4 hours after bypass. No other important differences were found.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of retrograde cardioplegia technique on myocardial perfusion and energy metabolism: a magnetic resonance imaging and localized phosphorus 31 spectroscopy study in isolated pig hearts

OBJECTIVE: The present work was designed to study the myocardial perfusion and energy metabolism during retrograde cardioplegia performed with different methods, including deep coronary sinus cardioplegia, coronary sinus orifice cardioplegia, and right atrial cardioplegia. METHODS: Isolated pig hearts were subjected to antegrade cardioplegia, right atrial cardioplegia, deep coronary sinus cardioplegia, and coronary sinus orifice cardioplegia in a random order. Cardioplegic distribution was assessed by T1-weighted magnetic resonance imaging in 1 group of hearts (n = 8). The flow dynamics of cardioplegia were assessed by T2*-weighted imaging in a second group of hearts (n = 8). RESULTS: T1-weighted images revealed an apparent perfusion defect in the posterior wall of the left ventricle, the posterior portion of the interventricular septum, and the right ventricular free wall during deep coronary sinus cardioplegia. The perfusion defect observed in the first 2 regions with deep coronary sinus cardioplegia resolved with coronary sinus orifice cardioplegia. Right atrial cardioplegia provided the most homogeneous perfusion to all regions of the myocardium relative to the other 2 retrograde cardioplegia modalities. T2*-weighted images showed that the 3 retrograde cardioplegia modalities provided similar cardioplegic flow velocities. Localized phosphorus 31 spectroscopy showed that the levels of adenosine triphosphate and phosphocreatine were significantly lower in the posterior wall (adenosine triphosphate, 42.86% +/- 5.91% of its initial value; phosphocreatine, 11.43% +/- 11.3%) than the anterior wall (adenosine triphosphate, 89.19% +/- 8.83%; phosphocreatine, 59.54% +/- 12.58%) of the left ventricle during 70 minutes of normothermic deep coronary sinus cardioplegia. CONCLUSIONS: Deep coronary sinus cardioplegia results in myocardial ischemia in the posterior wall of the left ventricle and the posterior portion of the interventricular septum, as well as in the right ventricular free wall. Coronary sinus orifice cardioplegia improves cardioplegic distribution in these regions. Relative to deep coronary sinus cardioplegia and coronary sinus orifice cardioplegia, right atrial cardioplegia provides the most homogeneous perfusion.     

Atrial activity during cardioplegia and postoperative arrhythmias

Cardioplegia provides excellent protection for the left ventricle, but the right atrium may be poorly protected. Myocardial temperatures, right atrial electrical activity, and postoperative arrhythmias were assessed in 103 patients participating in two consecutive randomized trials comparing blood cardioplegia (n = 36), crystalloid cardioplegia (n = 38), and diltiazem crystalloid cardioplegia (n = 29). Both right atrial and right ventricular temperatures were significantly warmer (p less than 0.05) during delivery of the blood cardioplegic solution than during delivery of either the crystalloid or the diltiazem crystalloid cardioplegic solutions; the aortic root temperatures were 9 degrees +/- 2 degrees C with blood cardioplegia and 5 degrees + 1 degrees C with both crystalloid and diltiazem crystalloid cardioplegia. Atrial activity during cardioplegic arrest was greatest with blood cardioplegia (12 +/- 3 beats/min), lower with crystalloid cardioplegia (10 +/- 2 beats/min), and minimal with diltiazem crystalloid cardioplegia (5 +/- 1 beats/min, p less than 0.05). Perioperative ischemic injury (by creatine kinase MB isoenzyme analysis) was greatest with crystalloid cardioplegia (p less than 0.05). Postoperative supraventricular arrhythmias (both treated and untreated) were more frequent after crystalloid cardioplegia (crystalloid, 63%; blood, 40%; diltiazem, 47%; p less than 0.05). Patients in whom supraventricular arrhythmias developed had significantly more postoperative ischemic injury (by creatinine kinase MB isoenzyme analysis, p less than 0.05). Blood cardioplegia reduced supraventricular arrhythmias by reducing ischemic injury despite warmer intraoperative temperatures and more right atrial activity. Diltiazem crystalloid cardioplegia reduced postoperative arrhythmias by improving intraoperative myocardial protection and suppressing intraoperative and postoperative atrial activity. Crystalloid cardioplegia cooled but did not arrest the right atrium intraoperatively, resulted in the most perioperative ischemic injury, and yielded the highest incidence of postoperative supraventricular arrhythmias.     

Effects of antegrade cardioplegic infusion with simultaneously controlled coronary sinus occlusion on preservation of regionally ischemic myocardium after acute coronary artery occlusion and reperfusion

This study was conducted to assess the protective effects of antegrade infusion of cardioplegic solution with simultaneously controlled coronary sinus occlusion on regionally ischemic myocardium after acute coronary occlusion and reperfusion. Twelve sheep were subjected to 1 hour of occlusion of the distal left anterior descending coronary artery. Sheep in group I (n = 6) were subjected only to infusion of potassium crystalloid cardioplegic solution into the aortic root, whereas in group II (n = 6) a stitch was snared around the proximal coronary sinus for its subsequent occlusion during antegrade infusions of cardioplegic solution. All animals were placed on cardiopulmonary bypass. Five hundred milliliters of cardioplegic solution at 4 degrees to 8 degrees C was administered in three divided doses during the total cross-clamp period of 30 minutes. The occlusion of the left anterior descending artery was then released, and the animals were weaned from bypass and studied for an additional 4 hours. Coronary sinus pressure, myocardial temperature, regional function assessed by pairs of ultrasonic crystals, global function assessed by rate of rise of left ventricular pressure and cardiac output, and the area at risk and area of necrosis were determined. The heart was excised at the end of the experiment and stained. Animals treated by the technique of antegrade infusion combined with coronary sinus occlusion had more homogeneous myocardial cooling during cardioplegic infusions and better recovery of the first derivative of left ventricular pressure and regional segment shortening at 90 and 270 minutes of reperfusion than those treated with antegrade infusion alone (p less than 0.01 and p less than 0.05, respectively). The group treated by antegrade infusion of cardioplegic solution combined with coronary sinus occlusion had an area of necrosis/area at risk ratio of 40.5% +/- 1.2%; the antegrade infusion group, 58.3% +/- 4.1% (p less than 0.01). These data suggest that antegrade infusion combined with coronary sinus occlusion may be an improved method of global and regional myocardial protection in the presence of an occluded coronary artery.