Multidose blood versus crystalloid cardioplegia

Comparison of Bretschneider HTK cardioplegia solution and blood cardioplegia in terms of postoperative results in patients who underwent isolated supracoronary ascending aortic replacement

INTRODUCTION

Cardiac arrest with cardioplegia is the most common and reliable method of myocardial protection in cardiac surgery, but there is no definite consensus on the use of different types of cardioplegia. Two of the commonly used types of cardioplegia are Bretschneider histidine-tryptophan-ketoglutarate solution (Custodiol) and conventional blood cardioplegia. In this study, Custodiol solution and conventional blood cardioplegia used in patients with type A aortic dissection who underwent supracoronary ascending aortic replacement were aimed to be compared in terms of postoperative results.

METHODS

70 patients with type A aortic dissection who underwent supracoronary ascending aortic replacement in our clinic between January 2011 - October 2020 were included. Patients were divided into two groups, blood cardioplegia group (n = 48) and Custodiol group (n = 22) and they were compared regarding preoperative, perioperative and postoperative variables.

RESULTS

There was no significant difference between cardiopulmonary bypass time and cross-clamp time (p = 0.17 and p = 0.16, respectively). Mechanical ventilator weaning time, intensive care unit stay and hospital stay were shorter in Custodiol group (p = 0.04,p = 0.03 and p = 0.05, respectively). While inotropic support need was higher in the blood cardioplegia group (p = 0.001), there was no significant difference in terms of mortality, arrhythmia, neurological complications and renal complications.

CONCLUSIONS

Our results show that Custodiol cardioplegia solution may be superior to blood cardioplegia in reducing mechanical ventilation weaning period, intensive care and hospital stay, and reducing the use of inotropic agents in patients with type A aortic dissection undergoing supracoronary ascending aorta replacement.

Comparison Between Blood and Crystalloid Cardioplegia in Patients with Left Ventricular Dysfunction Undergoing Coronary Surgery

This study was done to compare the protective effect of blood and crystalloid cardioplegia in patients with left ventricular dysfunction undergoing coronary artery bypass grafting (CABG). Sixty consecutive patients with left ventricular ejection fraction < 35 % scheduled for CABG with the use of cardiopulmonary bypass without additional procedures were randomly divided into two groups. In the first group we used cold blood cardioplegia, in the second group cold crystalloid cardioplegia, both delivered only ortogradly. We measured hemodynamic data in early hours after operation, enzyme release and we collected other clinical data which could be influenced by perioperative myocardial protection. There was no death in either group. We also didn’t find any significant difference in incidence of perioperative myocardial infarction, arrhytmias and use of intraaortic balloon pumping between both groups. In an early hours after operation in the group with blood cardioplegia we found significantly better hemodynamic data (LVSWI, RVSWI) and significantly lower enzyme release. We conclude, that cold blood cardioplegia shows superior perioperative myocardial protection resulting in earlier restoration of myocardial function. This difference could be important in patients with high degree of left ventricular dysfunction.

Clinical Results of Different Myocardial Protection Techniques in Aortic Stenosis

Background

Hypertrophied myocardium is especially vulnerable to ischemic injury. This study aimed to compare the early and late clinical outcomes of three different methods of myocardial protection in patients with aortic stenosis.

Methods

This retrospective study included 225 consecutive patients (mean age, 65±10 years; 123 males) with severe aortic stenosis who underwent aortic valve replacement. Patients were excluded if they had coronary artery disease, an ejection fraction <50%, more than mild aortic regurgitation, or endocarditis. The patients were divided into three groups: group A, which was treated with antegrade and retrograde cold blood cardioplegia; group B, which was treated with antegrade crystalloid cardioplegia using histidine-tryptophan-ketoglutarate (HTK) solution; and group C, treated with retrograde cold blood cardioplegia.

Results

Group A contained 70 patients (31.1%), group B contained 74 patients (32.9%), and group C contained 81 patients (36%). The three groups showed significant differences with regard to the proportion of patients with a New York Heart Association functional classification ≥III (p=0.035), N-terminal pro-brain natriuretic peptide levels (p=0.042), ejection fraction (p=0.035), left ventricular dimensions (p<0.001), left ventricular mass index (p<0.001), and right ventricular systolic pressure (p<0.001). Differences in cardiopulmonary bypass time (p=0.532) and aortic cross-clamp time (p=0.48) among the three groups were not statistically significant. During postoperative recovery, no significant differences were found regarding the use of inotropes (p=0.328), mechanical support (n=0), arrhythmias (atrial fibrillation, p=0.347; non-sustained ventricular tachycardia, p=0.1), and ventilator support time (p=0.162). No operative mortality occurred. Similarly, no significant differences were found in long-term outcomes.

Conclusion

Although the three groups showed some significant differences with regard to patient characteristics, both antegrade crystalloid cardioplegia with HTK solution and retrograde cold blood cardioplegia led to early and late clinical results similar to those achieved with combined antegrade and retrograde cold blood cardioplegia.

Cold blood cardioplegia reduces the increase in cardiac enzyme levels compared with cold crystalloid cardioplegia in patients undergoing aortic valve replacement for isolated aortic stenosis

OBJECTIVES

Cardiac arrest during cardiac surgery is most commonly induced by cold blood or cold crystalloid cardioplegia. The results from clinical studies are divergent regarding which of the 2 solutions provides better myocardial protection. This might be explained by several factors. Both heterogeneity in disease for the included patients and the fact that most studies are retrospective in design and that patients with coronary artery disease with different degrees of myocardial ischemia are included might explain these findings. To circumvent these potentially confounding factors, we included in a prospective randomized study only patients undergoing aortic valve replacement for aortic stenosis without other significant cardiac disease. Patients were randomized to antegrade cold crystalloid or cold blood cardioplegia.

METHODS

Eighty patients with aortic stenosis undergoing aortic valve replacement without significant coronary artery stenosis or other significant concomitant heart valve disease were included in the study. They were randomized to either antegrade cold blood or cold crystalloid cardioplegic solution delivered through the coronary ostia every 20 minutes throughout the period of aortic crossclamping. Maximum postoperative creatine kinase isoenzyme MB and troponin-T levels, well-established markers of myocardial damage, were compared between the 2 groups.

RESULTS

Both maximum postoperative creatine kinase isoenzyme MB and troponin-T levels were significantly higher by approximately 100% in the cohort of patients receiving crystalloid compared with blood cardioplegia. Only in the group of patients receiving cold crystalloid cardioplegia was there a positive correlation between cardiac enzyme levels and crossclamp time.

CONCLUSION

Antegrade cold blood cardioplegia provides better myocardial protection than cold crystalloid cardioplegia in patients undergoing aortic valve replacement.

Successful surgical correction of supravalvular pulmonary stenosis under beating heart using a cardiopulmonary bypass system in a dog

A male Pomeranian dog aged 1 year and 8 months was presented for evaluation of severe systolic ejection, cardiac murmur and syncope on excitation. Supravalvular pulmonary stenosis was diagnosed. An echocardiogram showed a supravalvular membranous stricture and a severely increased pulmonary arterial velocity in the stricture (6.49 m/s, pressure gradient of 169 mmHg). The supravalvular stricture was surgically removed by pulmonary arteriotomy with the heart beating using a cardiopulmonary bypass system. The postoperative pulmonary arterial velocity at the narrow area decreased to 3.80 m/s, and the pressure gradient decreased to 57.7 mmHg. Six months after the operation, there were no signs of restenosis, and the dog was in good condition without syncope. Surgical correction of pulmonary stenosis with the heart beating using a cardiopulmonary bypass system is useful because of the improvement it brings in safety and reliability.

Cardioplegia and myocardial ischemia during cardiopulmonary bypass

Presently myocardial protection can be obtained in three main ways: 1) energy conservation through chemical induction of rapid and complete diastolic arrest, 2) slowing of the metabolic rate and degradative process through the use of hypothermia, and 3) prevention or reversal of unfavourable ischemic-induced changes with various protective agents. These methods of myocardial protection and their effectiveness, the calcium metabolism during myocardial ischemia, and the effects of calcium channel blockers are briefly reviewed and discussed. It is stressed that myocardial protection during ischemic arrest is a complex entity, and that new modes of myocardial protection are needed in the future.

Leucocyte-depleted cardioplegia does not reduce reperfusion injury in hypothermic coronary artery bypass surgery

This study investigated the effects of leucocyte-depleted cardioplegia on postreperfusion oxidative stress and myocardial injury in elective hypothermic coronary artery bypass surgery. Forty patients were randomized to receive either cardioplegia with leucocytes depleted by an in-line Pall BC1B filter, or blood cardioplegia without leucocyte depletion. Transmyocardial oxidative stress was assessed by oxidized glutathione measurements in samples taken simultaneously from the coronary sinus and aortic root, and myocardial injury by postoperative CKMB and troponin-T measurements. The BC1B filters reduced numbers of cardioplegia leucocytes by a mean of 90.7%. Both patient groups demonstrated significant increases (p < 0.001) in transcardiac oxidized glutathione gradients after crossclamp release. No significant differences were found between the groups for postreperfusion oxidized glutathione gradients, postoperative levels of CKMB or troponin-T, or in the frequency of perioperative and postoperative complications. These results suggest that leucocyte-depleted cardioplegia does not significantly improve myocardial protection in patients undergoing elective coronary artery bypass surgery.

A clinical comparative study between crystalloid and blood-based St Thomas' hospital cardioplegic solution

OBJECTIVE

Myocardial protection with blood cardioplegia during cardiac surgery is increasingly preferred, but few studies have compared the protective effects of crystalloid cardioplegia to the same solution with blood as the only variable. This clinical study compared the protective effects of crystalloid or blood-based St. Thomas' Hospital cardioplegic solution No. 1.

METHODS

Fifty higher risk patients undergoing elective coronary artery bypass surgery, with an ejection fraction less than 40%, were randomly allocated to receive cold (4 degrees C) intermittent crystalloid St. Thomas' No. 1 cardioplegia (n = 25), or a similar blood-based solution (n = 25) with a haematocrit of 10-12%. We determined (1) peri-operative and post-operative arrhythmias, (2) left and right ventricular function (24 h) using the thermodilution technique, (3) left ventricular high-energy phosphate content sampled before ischaemia, the end of ischaemia and the end of bypass.

RESULTS

Pre-operative haemodynamic data, aortic cross-clamp and bypass times were similar in both groups of patients; there was no mortality. At the end of ischaemia there were no differences in ATP content between groups but creatine phosphate was maintained at a significantly (P < 0.007) higher level in the blood-based St. Thomas' cardioplegia group than the crystalloid St. Thomas' cardioplegia group (20+/-2 (SE) vs. 13+/-1 micromol/g dry wt, respectively). Return to spontaneous sinus rhythm was significantly (P = 0.002) increased in the blood-based St. Thomas' cardioplegia group (96%) compared to the crystalloid St. Thomas' cardioplegia group (60%). Early post-operative ventricular dysfunction occurred in both groups, but normal LV function (stroke work index) recovered significantly (P = 0.043) more rapidly (by 2 h) in the blood-based St. Thomas' cardioplegia group of patients.

CONCLUSIONS

In a higher risk (EF < 40%) group of patients undergoing elective cardiac surgery, addition of blood to an established crystalloid cardioplegic solution significantly enhanced myocardial protection by reducing arrhythmias, improving rate of recovery of function and maintaining myocardial high-energy phosphate content during ischaemia.

The adenosine-triphosphate-sensitive potassium-channel opener pinacidil is effective in blood cardioplegia

BACKGROUND

This study was designed to evaluate the adenosine-triphosphate-sensitive potassium channel opener pinacidil as a blood cardioplegic agent.

METHODS

Using a blood-perfused, parabiotic, Langendorff rabbit model, hearts underwent 30 minutes of normothermic ischemia protected with blood cardioplegia (St. Thomas' solution [n = 8] or Krebs-Henseleit solution with pinacidil [50 micromol/L, n = 81) and 30 minutes of reperfusion. Percent recovery of developed pressure, mechanical arrest, electrical arrest, reperfusion ventricular fibrillation, percent tissue water, and myocardial oxygen consumption were compared.

RESULTS

The percent recovery of developed pressure was not different between the groups (52.3 +/- 5.9 and 52.8 +/- 6.9 for hyperkalemic and pinacidil cardioplegia, respectively). Pinacidil cardioplegia was associated with prolonged electrical and mechanical activity (14.4 +/- 8.7 and 6.1 +/- 3.9 minutes), compared with hyperkalemic cardioplegia (1.1 +/- 0.6 and 1.1 +/- 0.6 minutes, respectively; p < 0.05). Pinacidil cardioplegia was associated with a higher reperfusion myocardial oxygen consumption (0.6 +/- 0.1 versus 0.2 +/- 0.0 mL/100 g myocardium/beat; p < 0.05) and a higher percent of tissue water (79.6% +/- 0.7% versus 78.6% +/- 1.2%; p < 0.05).

CONCLUSIONS

Systolic recovery was not different between groups, demonstrating comparable effectiveness of pinacidil and hyperkalemic warm blood cardioplegia.

Clinical evaluation of a leucocyte-depleting blood cardioplegia filter (BC1B) for elective open-heart surgery

Activation of leucocytes during extracorporeal circulation has attracted attention in recent years as a cause of reperfusion injury in open-heart surgery patients. In the present study, 40 adult patients undergoing elective open-heart surgery were randomized into two groups: 20 using the Pall BC1B leucocyte-depleting filter for blood cardioplegia (group 1) and the other 20 without the filter (group 2). In order to determine if the filter was effective in protecting the myocardium, CPK-MB and troponin-T (TnT) were measured. In addition, efforts were also made to determine appropriate sites at which the BC1B blood cardioplegia filter should be positioned. There were no significant differences between the two groups in terms of conditions of perfusion. No adverse effects were seen in either group. The total leucocyte reduction rate through the filter was 98.1% with the passage of 2 liters of blood through the filter. A pressure drop of 4.4 +/- 3.2 mmHg was observed through the filter during use. Statistically significant differences were noted between the two groups in CPK-MB (p = 0.031) and TnT (p = 0.004). Findings obtained in previous studies demonstrate that the various advantages of leucocyte reduction, shown in experimental studies, can be translated into clinical advantages. In conclusion, based on the results in this clinical study showing significant difference in CPK-MB and TnT which are known effective indicators for myocardial injury, between leucoreduced and non-leucoreduced group, the Pall BC1B leucocyte-depleting filter for blood cardioplegia has been shown to be effective in alleviating reperfusion injury in open-heart surgery patients.

Effect of pressure on myocardial function after 6-hour preservation with blood cardioplegia

BACKGROUND

This study examined the return of cardiac function in pig hearts after 6 hours' preservation by continuous perfusion with blood cardioplegia at two perfusion pressures compared with preservation with crystalloid solutions.

METHODS

Isolated pig hearts were randomly divided into five groups (n = 8 per group) according to the following treatments: group 1 = fresh hearts (control); group 2 = hearts arrested with Queen's cocktail cardioplegia and then immersion in 0 degrees C saline solution (QS group); group 3 = hearts arrested with (5 degrees C) and simple immersion in 0 degrees C University of Wisconsin solution (UW group); and groups 4 and 5 = hearts arrested with blood cardioplegia at 10 degrees C and then continuously perfused at a pressure of 80 cm H2O or 40 cm H2O, respectively (groups BC80 and BC40). After preservation for 6 hours, donor hearts were reperfused by a cross-circulation support pig. Thereafter, cardiac function and metabolism were examined every half hour for 2 hours. A three-way mixed general linear model was used to analyze data with repeated measures. Bonferroni test was used to determine differences (p < or = 0.05) between groups.

RESULTS

Only 4 hearts recovered electric activity in the BC80 group (p < or = 0.05 versus other groups). There was poor recovery of left ventricular work in the BC80 group compared with the other groups (p < 0.001). Left ventricular work in the QS and UW groups was also lower than in the control and BC40 groups. Left ventricular work in the BC40 group fully recovered. Maximum elastance did not differ between groups. Compliance was reduced in the QS, BC80, and BC40 groups versus controls after preservation (p < 0.006). Coronary flow decreased and coronary vascular resistance increased in the BC80 group versus the other groups (p < or = 0.001). Coronary flow in the QS, UW, and BC40 groups was lower than in the control group (p < 0.001). The magnitude of lactate release was much higher in the BC80 group than in the other groups (p < or = 0.001).

CONCLUSIONS

Continuous perfusion with 10 degrees C blood cardioplegia at 40 cm H2O pressure for 6 hours provided adequate preservation of systolic function in this model. University of Wisconsin solution provided the best protection of diastolic function.

Effect of delay in retroperfusion therapy on infarct size reduction

Retroperfusion of arterial blood through the coronary sinus reduces infarct size if therapy starts immediately after coronary artery occlusion. To determine if a new system of non-electrocardiogram-synchronized retroperfusion is able to reduce infarct size after delays consistent with clinical use, anesthetized pigs were subjected to 4 hours of left anterior descending coronary artery occlusion followed by 1 hour of reperfusion. Retroperfusion of arterial blood commenced immediately after occlusion of the left anterior descending coronary artery in the no-delay group (n = 10) and after a 1-hour (n = 10) and a 2-hour (n = 8) delay in two other groups. In the control group (n = 10), no therapy was used. In all groups, retroperfusion of arterial blood was terminated after 4 hours of occlusion of the left anterior descending coronary artery. Infarct size, expressed as a percentage of the in vivo area at risk (+/- the standard deviation), was smaller in the no-delay group (44.1 +/- 12.9) and marginally smaller in the 1-hour delay group (71.0 +/- 9.8) compared with controls (86.3 +/- 7.5) (p < 0.05). Infarct size in the 2-hour delay group (75.0 +/- 10.7) was not significantly different from controls. Mean coronary sinus pressure (+/- the standard deviation) was 56 +/- 25 mm Hg, 39 +/- 9 mm Hg, and 47 +/- 9 mm Hg in the no-delay, 1-hour delay and 2-hour delay groups, respectively. Thus, this new retroperfusion system limits infarct size by 50% if it is started immediately after coronary occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Fluosol cardioplegia results in complete functional recovery: a comparison with blood cardioplegia

Blood cardioplegia is considered by many to be the preferred solution for myocardial protection. Proposed benefits include the ability to deliver oxygen and the ability to maintain metabolic substrate stores. However, the decreased capacity of blood to release oxygen at hypothermic conditions as well as the presence of deleterious leukocytes, platelets, and complement may limit complete functional recovery. Fluosol is an asanguineous solution with the ability to bind and release oxygen linearly at low temperatures. Neonatal piglet hearts (24 to 48 hours old) were excised and supported on an isolated, blood-perfused working heart model. After baseline stroke-work index was determined, hearts were arrested with either normocalcemic blood cardioplegia (group 1, n = 8) or normocalcemic Fluosol cardioplegia (group 2, n = 8). Cold cardioplegia was administered at 45 mm Hg every 20 minutes for 2 hours. Hearts were then reperfused with whole blood. Functional recovery, expressed as percent of control stroke-work index, was determined 60 minutes after reperfusion at left atrial pressures of 3, 6, 9, and 12 mm Hg. Functional recovery at 60 minutes was similar between group 1 (95%, 93%, 93%, 88%) and group 2 (100%, 94%, 94%, 95%) at left atrial pressures of 3, 6, 9, and 12 mm Hg, respectively. Mean lactate consumption 5 minutes after reperfusion was significantly greater (p = 0.0001) in group 1 (31.8 +/- 6.3 micrograms.min-1 x g-1) than in group 2 (-0.59 +/- 0.1 microgram.min-1 x g-1), indicating superior metabolic recovery in the blood cardioplegia hearts. Edema formation, as determined both by water content (group 1, 81.10%; group 2, 81.63%) and by electron microscopy, was not significantly different between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood cardioplegia: a review and comparison with crystalloid cardioplegia

The Oxford International Symposium on myocardial preservation provided an appropriate milestone and impetus to survey one aspect of operative myocardial preservation, namely blood cardioplegia, and to contrast it with the more popular crystalloid cardioplegia. This review is by no means complete or exhaustive but represents my best effort to summarize important information that has accumulated in the literature as blood cardioplegia, and our understanding of it, has evolved. It is appropriate to compare blood and crystalloid cardioplegia with respect to biochemical and physiological differences. Clinical comparison has been limited, for the most part, to randomized studies, and a number of differences and details of clinical management of the two techniques have been omitted, either because they seemed unimportant or there was no good information that would allow an objective comparison of their significance. Hopefully, the reader will recognize the intent to focus on meaningful differences and similarities between the two techniques and to present them fairly.

Glutathione disulfide formation and lipid peroxidation during cardiac ischemia and reflow in the dog in vivo

The content of glutathione disulfide (GSSG) in tissue, coronary sinus blood plasma, and in cardiac lymph was measured in a well-characterized model of regional cardiac ischemia and reflow in dogs in vivo in order to assess the magnitude of the oxidant stress produced. No increase in GSSG content was observed during 60 min of occlusion of the circumflex or left anterior descending arteries, or during up to 70 min of reflow. The contents of 11-, 12-, and 15-hydroxyeicosatetraenoates (HETEs) in total lipids also were not increased following 60 min of regional ischemia and up to 60 min of reflow. In addition, global ischemia produced by aortic crossclamping and cardiopulmonary bypass did not increase HETE content. In contrast, infusion of tertiary butyl hydroperoxide (tBHP) into the left atrium produced readily measurable increases in GSSG content with or without prior induction of myocardial ischemia. Infusion of tBHP also increased tissue contents of the HETEs. These findings indicate that the canine myocardium subjected to ischemia-reflow conditions does not generate large amounts of reactive oxygen and does not form significant amounts lipid peroxidation products.

Upgrading acellular to sanguineous cardioplegic efficacy

To determine which biochemical entity of the red cell is responsible for preventing augmented postischemic myocardial oxygen consumption (MVO2), 28 canine hearts instrumented with ultrasonic dimension crystals underwent simultaneous determination of stroke work (SW) and MVO2 during incremental volume loading on right heart bypass before and 30 min after 2 hr of 10 degrees C cardioplegic arrest with unmodified oxygenated crystalloid cardioplegia (OC), OC with histidine of equal buffering capacity as 18% hematocrit blood (OC + H), or OC with 200 units/ml of superoxide dismutase and catalase (OC + SOD/C). In all groups, the slope of the linear SW vs end-diastolic volume relationship, Mw, and the slope of the linear SW vs MVO2 relationship, Me, were unchanged after cardioplegic arrest. The intercept of the SW vs MVO2 relationship, Eo, was augmented an average of 22.2% in the OC group, but both OC + H and OC + SOD/C prevented this subtle expression of ischemic injury. The characteristic of the red cell most likely responsible for the myoprotective efficacy of blood cardioplegia is buffering capacity; however, since the effects of tissue acidosis are partially mediated by free radicals, the use of free radical scavengers can also ameliorate ischemic damage incurred during cardioplegic arrest.

Quantitation of postischemic skeletal muscle necrosis: histochemical and radioisotope techniques

Skeletal muscle necrosis will result from prolonged periods of ischemia. The purpose of this study was to develop a method to estimate the extent of necrosis using nitroblue tetrazolium staining and technetium scanning. The bilateral canine gracilis muscle preparation with total vascular isolation was exposed to 4 hr of complete normothermic ischemia followed by reperfusion. After 45 hr of reperfusion 99mTc pyrophosphate (PYP) was injected and 3 hr later the muscles were harvested, cut into six slices, and stained with nitroblue tetrazolium. Biopsies were taken from tetrazolium-positive and -negative areas for electron microscopy to confirm the ability of the stain to distinguish viable from necrotic muscle. Computerized planimetry of the staining pattern was used to estimate the extent of necrosis as a percentage of the total muscle. Electron microscopy confirmed the validity of nitroblue tetrazolium to discriminate between viable and necrotic skeletal muscle in this experimental model. After 4 hr of ischemia the percentage necrosis was 30.2 +/- 6.1% (mean +/- SEM, n = 12), there was no difference in the extent of necrosis in left vs right paired muscles, using tetrazolium staining or technetium PYP uptake. There was a statistically significant correlation between the percentage necrosis and the density of 99mTc PYP uptake per muscle (r = 0.83, P less than 0.001) and per slice (r = 0.94, P less than 0.001). This study demonstrates the ability of tetrazolium staining to accurately differentiate between viable and necrotic skeletal muscle and provides a reproducible method for estimating the extent of necrosis in the gracilis muscle model.

Effects of blood and crystalloid cardioplegia on cardiac function at organ and cellular levels during hypothermic cardiac arrest

The present investigation was undertaken to compare the effects of cold crystalloid and blood cardioplegia on the functional recovery of the heart; on Ca++ binding and uptake, Ca++-ATPase of the sarcoplasmic reticulum (SR), and sarcolemmal (SL) ATPase; and on serum MB fraction of creatine kinase (MBCK) after one and half hours of reperfusion following one hour of ischemic cardiac arrest in dog. This study was made also to determine if the functional changes are related to the changes in biochemistry at the molecular level. The dogs were divided into three groups: sham bypass (SB), cold crystalloid cardioplegia (CC), and pump blood cardioplegia (PB). There was a decrease in the cardiac index (CI), left ventricular work index (LVWI), and mean aortic pressure (MAP) in all three groups. The index of myocardial contractility [dp/dt)/IIP) and CI were lower in the CC group as compared with the SB and PB groups. All the hemodynamic values for the PB group were similar to those of the SB group except total systemic vascular resistance (TSVR) and left ventricular end-diastolic pressure (LVEDP) which were lower in the PB group. The index of myocardial contractility and cardiac index appeared to be greater in the PB group than in the CC group. There was a decrease in the Ca++ uptake by SR from both the CC and PB groups. Ca++ binding and Ca++,-ATPase of SR from the PB group were depressed. The sarcolemmal ATPase was unaffected in both groups. The serum MBCK increased in both PB and CC groups, though the increase was smaller in the PB group. These results indicate that the functional recovery of the heart was slightly better with pump blood cardioplegia than with cold crystalloid cardioplegia. The depressed myocardial contractility and cardiac function in the CC group were associated with a decrease in the Ca++ uptake by SR. However, the decreases in the Ca++ binding, Ca++ uptake, and Ca++ ATPase by SR from the pump blood cardioplegic group were not accompanied by decreases in the cardiac contractility and cardiac function. Myocardial damage as assessed by serum MBCK was smaller in the PB group than in the CC group.

Anesthesia and cardiopulmonary bypass technique in calves and sheep

The number of research institutions using calves and sheep as models for open heart surgical procedures is increasing. The Artificial Heart Laboratory of the University of Utah has developed an effective protocol for thoracic procedures in these animals. Routine barbiturate induction and maintenance with fluothane and a pressure-regulated ventilator have minimized anesthetic problems. A membrane oxygenator with blood flows of 50 to 75 ml/kg body weight/min. seems to give adequate circulatory support during heart-lung bypass. Although animals implanted with total artificial hearts do not have problems with arrhythmias, changes in pulmonary function and peripheral vascular tone can alter their cardiac performance. The judicious use of ventilatory support and specific vasoactive drugs can significantly improve the animal's intraoperative blood pressure and postoperative arterial gases. A summary of the techniques and drugs which were used successfully in 187 of 189 animals during a 2 year period are presented.

Reduction in myocardial acidosis using blood cardioplegia

The composition of the ideal cardioplegic solution is controversial. Blood cardioplegia is an attractive alternative to standard crystalloid solutions, though its superiority in preserving myocardial metabolism has not been demonstrated. Using a new pH electrode system, this study contrasts the effects of blood and crystalloid solutions upon the generation of myocardial acidosis during global ischemia. Thirty-eight mongrel dogs underwent a 120-min period of aortic cross clamping using systemic hypothermia. To maintain myocardial temperature below 15 degrees C, 19 dogs received multiple doses of a bicarbonate containing crystalloid cardioplegic solution (Group I), while 19 dogs received multiple doses of blood cardioplegia (Group II). Myocardial pH and temperature were continuously monitored in the subendocardial region of the left ventricle. There was no difference in baseline pH between Group I (7.13 +/- 0.05) and Group II (7.17 +/- 0.05, P:NS). With systemic cooling and the initial bolus of cardioplegia, myocardial pH rose to 7.42 +/- 0.04 in Group I and 7.42 +/- 0.06 in Group II (P:NS). After 120 min of global ischemia, myocardial pH decreased to 6.61 +/- 0.05 in Group I and 7.07 +/- 0.05 in Group II (P less than 0.001). Blood cardioplegia was most effective during the first hour of aortic cross clamp when myocardial pH rose by 0.13 +/- 0.04 pH units. In contrast, myocardial pH in Group I during the first hour of global ischemia fell -0.35 +/- 0.08 pH units (P less than 0.001 compared to Group II). During the second hour of cross clamp, myocardial pH declined both in Group I (0.26 +/- 0.03 pH units) and in Group II (0.24 +/- 0.05 pH units, P:NS). However, the accumulation of hydrogen ion during the second hour was significantly greater in Group I (+128.0 +/- 21.4 nm/liter) than in Group II (+36.6 +/- 9.0 nm/liter, P less than 0.001). Thus, myocardial acidosis was reduced during the administration of blood cardioplegia when compared to a bicarbonate-buffered crystalloid solution. The salutary effects of blood cardioplegia on myocardial metabolism stem from blood's significant buffering capacity and its ability to deliver oxygen.

Surgical revascularization of acute (1 hour) coronary occlusion: blood versus crystalloid cardioplegia

This study compares blood versus crystalloid cardioplegia in restoring contractile function, and high-energy phosphate and tissue water content in a myocardial segment after 1 hour of coronary artery occlusion. Anesthetized dogs underwent instrumentation with the chest open to measure left ventricular and aortic pressures, and systolic shortening in the myocardium perfused by the left anterior descending coronary artery (LAD) was measured with ultrasonic crystals. In 21 dogs, the LAD was occluded for an hour, thereby replacing systolic shortening with passive lengthening averaging -28.7 +/- 6.2% of control shortening in both groups. The dogs were then placed on total bypass, and arrest was achieved with multidose crystalloid (N = 10) or blood cardioplegia (N = 11). The ligatures were released just prior to the second infusion of cardioplegic solution. Postischemic subendocardial levels of adenosine triphosphate were comparably depleted with crystalloid and blood cardioplegia (55.2% and 44.0%, respectively, of control). Subendocardial increases in water content were similar for crystalloid (3.62%) and blood (3.16%) cardioplegia. Recovery of segmental shortening was significantly greater with blood than crystalloid cardioplegia (31.5 +/- 8.2% versus 4.9 +/- 6.6% of control, respectively). We conclude that the composition and the delivery of blood cardioplegia used in this study restore greater postischemic function than crystalloid cardioplegia in acute evolving myocardial infarction.

Recent advances in cardiopulmonary bypass and the clinical application of myocardial protection

Basic scientific research has provided the impetus to develop cardioplegic solutions that offer excellent myocardial preservation. Future research will continue to develop methods for better delivery of cardioplegia to all myocardial regions. In addition, earlier detection of evolving ischemic damage during aortic cross-clamping might provide a basis for earlier intervention to reverse developing myocardial injury. At the present time, the cardiac surgeon has many cardioplegic solutions and delivery systems from which to choose. Only by understanding the principles involved in myocardial preservation will the surgeon be able to develop a system that will work best in his or her clinical practice.

Delayed left ventricular free wall rupture complicating coronary artery bypass surgery. A case report

Rupture of the left ventricular free wall is a not uncommon life-threatening complication of acute myocardial infarction and after prosthetic mitral valve replacement. To our knowledge, no case of left ventricular rupture after coronary artery bypass surgery has been reported. A case is now described in which coronary artery bypass grafting was complicated by delayed rupture, which was successfully repaired. Different etiologic factors are discussed, but the cause considered most likely was trauma from elevation of and traction on the heart in exposure of its posterior aspect.