Methods Of Myocardial Preservation Research Articles

Myocardial preservation methods in isolated minimal invasive mitral valve surgery: Society of Thoracic Surgeons (STS) database outcomes.

Minimal invasive mitral valve surgery (MIMVS) has become a commonly used approach for mitral valve surgery. Several techniques of myocardial preservation were described in patients undergoing MIMVS. We aim to evaluate preservation technique and short term outcomes. A retrospective analysis of patients who underwent isolated MIMVS and were included in the Society of Thoracic Surgeons (STS) database. The final cohort included 4976 patients. Mean age was 63.1 years (SD, 12.5) and 42.6% were females. Antegrade delivery method (71.3% of the patients) was the most common, follow by antergrade/retrograde (19.9%). Blood, crystalloid solution, and combination of blood-crystalloid were used in 62.4%, 13.2%, and 13.7%, respectively. In multivariate analysis, cardioplegia technique was associated with mortality (P = .011), pleural effusion (P = .045), and length of ICU stay (P < .001). Antegrade-crystalloid (OR, 3.37; 95%CI, 1.70-6.68) and antegrade/retrograde-blood/crystalloid (OR, 3.28; 95%CI, 1.15-9.38) were associated with increased risk for mortality compared with antegrade-blood cardioplegia. Data on postoperative ejection fraction (EF), CPK-MB, and Troponin was available only in 30%, 9%, and 5% of the patients, respectively, and were not included in the analysis. Ante-grade-blood was the most common preservation technique in MIMVS. Ante-grade-crystalloid and ante-grade/retrograde-blood/crystalloid are associated with increased risk for mortality. The results suggest that using crystalloid solutions for cardioplegia should be carefully considered. The STS database as a source for MIMVS outcome analysis is lacking, both in detailed specification of different surgical technique aspects, and in actual data collection of already existing categories.

Adenosine injection prior to cardioplegia enhances preservation of senescent hearts in rat heterotopic heart transplantation

Advanced donor age is one of the risk factors for graft failure and is the leading cause of early death after heart transplantation. Better myocardial preservation methods should reduce graft failure. The purpose of this study was to determine if adenosine, which is known to enhance cardioplegic protection, enhances myocardial preservation during heart transplantation using older donors. We used a rat heterotopic heart transplantation model with Lewis rats that were at least 60 weeks old as donors. We injected saline (control) or adenosine (0.1 or 0.2 mg/kg) before cardioplegia, perfused with cold Celsior and stored the hearts in Celsior for 6 h at 4°C. The grafts were transplanted into syngenic, 12-16-week old recipients, and blood and tissue were collected 3 h after reperfusion. Bolus injection of adenosine led to faster mechanical arrest after perfusion with Celsior and faster reanimation after reperfusion compared with controls. Adenosine treatment significantly reduced myocardial injury, as indicated by serum troponin I and creatine phosphokinase levels. The mRNAs for inflammatory cytokines were markedly increased in the control grafts, but were less upregulated in the grafts treated with adenosine. The grafts treated with adenosine also exhibited less mitochondrial damage, fewer infiltrating cells and a higher adenosine triphosphate content. Adenosine injection prior to perfusion of cardioplegia significantly reduced cold ischaemia/reperfusion injury in cardiac grafts from older donors and improved the stores of cellular energy after reperfusion. This procurement protocol may be clinically feasible and should be considered in the clinical setting, particularly for older donors.

Associated factors with survivals in patients undergoing orthotopic heart transplant using retrograde blood microcardioplegia

Several techniques and cardioplegic solutions have been used for heart preservation during transplant procedures. Unfortunately, there is a lack of ideal method for myocardial preservation in the clinical practice. The use of retrograde cardioplegia provides continuous infusion of cardioplegic solution during the graft implantation. This strategy may provide better initial recovery of the graft. The objective of this study is to describe the experience of a single center where all patients received the same solution for organ preservation and were subjected to continuous retrograde blood microcardioplegia during implantation of the graft and to evaluate factors associated to early and late mortality with this technique.This is a retrospective, observational and descriptive study of a single center.During the study period were performed 35 heart transplants. Fifteen (42.9%) patients were in cardiogenic shock. The probability of survival was 74.8±7.8%, 60.4±11.3% and 15.1±13.4% at 1 year, 5 years and 10 years of follow-up, respectively. The median survival time was 96.6 months.The use of myocardial protection with retrograde cardioplegic solution may reduce the risks associated morbidity due to cold ischemia time during the heart transplant, and we suggest that this benefit may be even greater in cases of cold ischemia time longer ensuring protection to the myocardium.

Invited Commentary

Algarni and colleagues [1Algarni K.D. Maganti M. Yau T.M. Predictors of low cardiac output syndrome after isolated coronary artery bypass surgery: trends over 20 years.Ann Thorac Surg. 2011; 92: 1678-1685Abstract Full Text Full Text PDF PubMed Scopus (92) Google Scholar] present a 20-year analysis of a large cohort of patients undergoing coronary artery bypass grafting, in which they document a decrease in the prevalence of low cardiac output syndrome, improved in-hospital mortality, and a reduction in major postoperative complications over this 20-year span. Two unexpected findings in the current era were an increase in mortality among patients suffering low cardiac output syndrome and an increase in the likelihood of low cardiac output syndrome among patients with an ejection fraction less than 20%. A major conclusion of this analysis suggests caution in the evaluation of suitability for coronary bypass surgery among patients with a low ejection fraction and emphasizes the persistent imperfections of current methods of myocardial preservation. Is the reader to conclude that surgeons and physicians are experiencing degradation in their punctilious management of low cardiac output or preservation of the myocardium in patients with low ejection fraction in the current era? Although possible, it seems highly unlikely. A more plausible explanation acknowledges the inimical effect of accepting “sicker” patients for surgery with depressed ejection fraction in the current era, and that other variables describing the severity of advanced heart failure are not identified in this multivariable analysis. It is well known, for example, that ejection fraction is a poor discriminator of overall cardiac reserves. The same likely applies to the increased mortality among patients who develop low cardiac output syndrome, in that other unidentified patient-specific risk factors likely account for the increased mortality in the current era. All this speaks to the challenges of multivariate analyses that examine “era effects” and the inferences based on such analyses. Patients that are actually sicker in the current era may evade the detection of higher risk related to the panoply of additional comorbidities and other subtleties of the risk profile that are not always elucidated by variables entered into a statistical model. This conundrum confounds performance reports in many areas of cardiothoracic surgery when recent outcomes appear worse compared with the more distant past. This missive is not intended to deprecate the value of such research, but rather to underscore the challenge for the outcomes for researchers who strive to identify variables that connote true risk when depicting severity of illness and risk of mortality for individual patients undergoing increasingly complex cardiac operations. Predictors of Low Cardiac Output Syndrome After Isolated Coronary Artery Bypass Surgery: Trends Over 20 YearsThe Annals of Thoracic SurgeryVol. 92Issue 5PreviewPostoperative low cardiac output syndrome (LCOS) is associated with high morbidity and mortality after coronary artery bypass grafting (CABG). We sought to examine trends in predictors of LCOS after isolated CABG. Full-Text PDF

The Southern Thoracic Surgical Association 50th anniversary celebration: the impact of STSA pediatric cardiothoracic surgery manuscripts on surgical practice

Background Members of the Southern Thoracic Surgical Association (STSA) have presented important pediatric cardiothoracic surgery papers at the annual meetings over the last 50 years. In order to determine the influence of these presentations on the practice of surgery, a review was undertaken. Early papers were characterized by emerging advances in open-heart surgery, anatomic congenital heart studies, and electrophysiologic discoveries that extended life with pacemakers. Later years were characterized by innovative myocardial preservation methods, improved cardiopulmonary bypass techniques, expanded homograft availability, emphasis on accurate repairs, intraoperative transesophageal echocardiography, and cardiopulmonary transplantation. Methods All but one of the scientific programs of the annual meetings (that of 1964) were located. The programs were reviewed and 180 presentations were identified on topics in congenital heart disease, pediatric thoracic disease, and pediatric thoracic wall abnormalities. Of those 180 oral presentations, 155 manuscripts (86%) were eventually published or in press and available for critical review and analysis. Manuscripts were grouped by diagnosis or therapeutic intervention. We determined a “cumulative citation frequency” (CCF), which measures the number of times an article is cited in the bibliography of related papers in the universe of participating journals. The selected manuscripts were compared with the historic landmark contributions and the existing trends at the time, and the number of articles both by individual authors and from institutions were tallied. Results Grouping by authors and institutions showed that 100 of 155 pediatric cardiothoracic manuscripts (65%) originated from 13 institutions. The CCF for the 20 leading articles ranged from 26 to 93. Conclusions This historical STSA 50-year record of pediatric cardiothoracic advances was accomplished in a milieu of collegial respect and camaraderie. Our annual meetings over the years have provided a venue for thoracic surgeons to share their ideas, innovations, and scientific inquiry. These contributions have significantly affected the practice of pediatric cardiothoracic surgery. The STSA has worked for 50 years and we trust that it will work for another 50 years and beyond.

Non-depolarizing cardioplegia activates Ca2+-ATPase in sarcoplasmic reticulum after reperfusion.

Depolarizing cardioplegia is the most common method for myocardial preservation in cardiac operations. However, depolarizing cardioplegia causes depolarization of the membrane potential by extracellular hyperkalemia, resulting in depletion of energy stores and calcium overload. This study examined the hypothesis that non-depolarizing cardioplegia would provide superior protection compared with depolarizing cardioplegia. In an isolated rat heart Langendorff model, hearts were perfused for 10 min with St. Thomas' Hospital cardioplegic solution (Group I: n=20), St. Thomas' Hospital cardioplegic solution+Lidocaine 1 mM (Group II: n=20) or non-depolarizing cardioplegia (Group III: n=20). The hearts then were subjected to 60 min of normothermic global ischemia, after which they were perfused with Krebs-Henseleit buffer at 37 degrees C for 30 min. The percent recovery of functional data, myocardial cyclic AMP contents, and myocardial cyclic GMP contents were recorded at each time point (base, after the administration of cardioplegia, after global ischemia, and after 30 min of reperfusion). Ca(2+)-ATPase in sarcoplasmic reticulum was measured at pre-ischemia and 30 min of reperfusion. The percent recovery of developed pressure and +/-dp/dt were significantly higher in Group III than in other groups. Myocardial cyclic AMP and GMP contents were elevated after reperfusion in all groups. However, in Group III, myocardial cyclic AMP contents after 30 min of reperfusion were significantly higher than in other groups (Group III: 14.7+/-1.6 vs. Group I: 8.7+/-1.0, Group II: 8.3+/-0.2 pmol/mg dry weight, P=0.05) but not cGMP. The sarcoplasmic reticulum Ca(2+)-ATPase activities at 30 min of reperfusion significantly increased in Group III compared with Groups II and I (Group III: 70.3+/-3.6 vs. Group I: 46.8+/-3.4, Group II: 53.9+/-6.1 micromol Pi/mg per h, P=0.025 and P=0.030). Non-depolarizing cardioplegia induced the activity of Ca(2+)-ATPase in sarcoplasmic reticulum after reperfusion. The activity would be increased by the cyclic AMP pathway. These findings suggested that non-depolarizing cardioplegia prevented calcium overload after reperfusion, especially decreased cytosolic calcium during the diastolic phase.

Insulin cardioplegia for elective coronary bypass surgery

Background: Improved methods of myocardial preservation are required to reduce the morbidity and mortality of coronary bypass surgery for high-risk subgroups. Metabolic stimulation with insulin, glucose solutions, or both has been proposed as a method to preserve the ischemic myocardium. We performed a prospective, double-blind, randomized trial to evaluate the effects of insulin and glucose as cardioplegic additives when used as part of a tepid continuous blood cardioplegic strategy. Methods: We randomized 56 male patients undergoing elective isolated coronary bypass surgery to 1 of 4 cardioplegic groups containing either 42 or 84 mmol/L glucose with or without 10 IU/L of insulin. Perioperative assessments of myocardial metabolism and left ventricular function were performed. Results: Insulin-enhanced cardioplegia was associated with beneficial effects on both myocardial metabolic and functional recovery after cardioplegic arrest. Insulin’s effect was independent of the ambient glucose concentration. Conclusions: Cardioplegic formulations containing a 42 mmol/L concentration of glucose and a 10 IU/L concentration of insulin provide significant benefit to patients undergoing isolated coronary bypass surgery. The clinical effect of these formulations will need to be assessed in high-risk subgroups of patients, such as those with unstable angina, recent myocardial infarction, or poor left ventricular function. (J Thorac Cardiovasc Surg 2000;119:1176-84)

Mechanical support of the pediatric cardiac patient.

Increased understanding of the anatomical nuances of congenital heart defects, improved methods of myocardial preservation, and advances in surgical techniques have led to improved results and need for postoperative mechanical support in patients undergoing congenital heart surgery. However, there remains a small portion of patients with myocardial or pulmonary failure that can can be rescued by intelligent use of mechanical support. The most widely used form of mechanical support is extracorporeal membrane oxygenation (ECMO), which has been adapted for use in congenital heart patients as well as patients with respiratory failure. Recent reports have suggested that ventricular support devices may also be useful in this patient population. A promising new application of mechanical support is for rescue during cardiac arrest; surprisingly good results have been obtained in this obviously moribund group of patients. Future developments in mechanical support include more accurate identification of patients who will benefit from this therapy and technological advances that will provide greater biocompatibility and simplification of the support circuit. Copyright 2000 by W.B. Saunders Company

Aortic valve replacement after previous coronary artery bypass grafting

As the population ages, an increasing number of patients with previous coronary artery bypass grafting (CABG) will require subsequent aortic valve replacement (AVR). This study examined outcome of AVR after previous CABG and reviewed possible indications for valve replacement at the time of initial myocardial revascularization. Between March 1975 and December 1994, 145 patients had AVR after previous CABG. Sixty-three patients (43%) had their initial CABG elsewhere. Reoperation for AVR was the second cardiac procedure in 137 patients and the third in 8. Redo CABG with AVR was done in 66 (46%). There were 118 men and 27 women. The mean age at CABG was 64 +/- 7.9 years; for AVR this was 71 +/- 7.6 years. In 2 young patients accelerated calcific aortic stenosis occurred in the setting of renal failure. Significant aortic stenosis did not appear to be addressed at initial CABG in 3 patients. Transaortic valvular gradient, as measured by cardiac catheterization, increased by 10.4 +/- 7.0 mm Hg/y. Twenty-four patients (16.6%) died. The mortality for AVR alone or for AVR + redo-CABG was 15 of 125 patients (12%). For patients having more complicated procedures, the mortality was 9 of 20 (45%). Nine patients (6.2%) suffered a postoperative cerebrovascular accident. Low preoperative ejection fraction measured by echocardiography, sternal reentry problems, complexity of operation, and prolonged cross-clamp and bypass times were significant factors associated with mortality. Age at AVR, interval between operations, the extent of underlying native coronary artery disease, the state of the previously placed bypass conduits, and methods of myocardial preservation were not significant predictors of operative mortality. On multivariate analysis there was only one significant value: prolonged cross-clamp time. Aortic valve replacement after previous CABG is associated with a mortality that is higher than that seen after repeat CABG or repeat AVR. It seems prudent, therefore, to use liberal criteria for AVR in those patients who require coronary revascularization and who, at the same time, have mild or moderate aortic valve disease.

Prolonged neonatal myocardial preservation with a highly buffered low-calcium solution

Optimal methods of myocardial preservation remain controversial in the neonate. This study compared prolonged hypothermic storage of neonatal hearts with modified University of Wisconsin solution (group I) with a solution formulated to promote anaerobic glycolysis by providing proton buffering with histidine (100 mmol/L) and exogenous glucose and insulin (group II). Hearts from piglets aged 3 to 5 days were given a single dose of either solution ( n = 6 each), subjected to 20 hours of global ischemia at 4° C, and reperfused with an erythrocyte-enhanced perfusate in an isovolumic Langendorff preparation. After 1 hour of reperfusion, in comparison with hearts preserved with University of Wisconsin solution, those in group II demonstrated (mean ± standard error of the mean) greater left ventricular developed pressure (101 ± 7 versus 62 ± 9 mm Hg, p < 0.01) and the first derivative of left ventricular pressure (816 ± 23 versus 614 ± 69 mm Hg · sec -1, p < 0.05). Diastolic indices were reduced to a similar degree in the two groups. Myocardial oxygen consumption was significantly greater (38.8 ± 2.4 versus 11.8 ± 2.4 μl oxygen · min · g -1, p < 0.01) in group II hearts. Group I hearts vasoconstricted (6% increase in coronary vascular resistance) in response to an intracoronary infusion of acetylcholine (20 nmol·min -1); in contrast, acetylcholine produced coronary dilation in group II hearts (5% decrease in coronary resistance, p < 0.02) that was similar to that observed in nonischemic control hearts. These results demonstrate enhanced preservation of myocardial contractility, oxidative metabolism, and vascular function in neonatal hearts provided by a solution designed to buffer protons and promote anaerobic glycolysis during ischemia. (J THORAC CARDIOVASC SURG 1994;108:772-9)

European approach to cardiopulmonary bypass in neonates

The advent of cardiopulmonary bypass in 1953, and its subsequent continuous refinements, have securely established the specialty of cardiovascular surgery. In conjunction with the improved methods of myocardial preservation, this has allowed the safe repair of acquired and complex congenital cardiac defects. During the years, the many variables of the systems used for cardiopulmonary bypass have been altered to the point that most operations are now reproducible with, relatively, low morbidity and mortality. Although in its present form the system is quite reasonable for most routine surgery, it is far from perfect. There remains, therefore, a quest for alterations to improve the system as an ongoing process. Certain complications of open-heart surgery persist and many new and unique approaches to the concept of organ protection and the treatment of these complications must be developed and refined.

Exercise responses in ventricular septal defect

Most reports indicate that exercise testing in operated and unoperated VSD patients demonstrates subnormal levels of work performance, maximal heart rate response, and ventricular function. Usually, maximal oxygen consumption is normal but the ventilatory anaerobic threshold is decreased. It is important to consider, however, that many of these studies were performed during an era in which children with unoperated VSD were often physically restricted and surgical closure of the defect frequently was delayed until relatively late in childhood. Our studies of VSD patients are encouraging. These patients were operated on at such young ages that a mindset of chronic cardiovascular disability was not characteristic for the child or family. Moreover, the patients have been operated on with contemporary surgical techniques and more enlightened methods of myocardial preservation during cardiopulmonary bypass. Follow-up exercise testing of these patients over the next decades will be important to determine if abnormalities can be detected in adult patients, as the effects of atherosclerotic and hypertensive cardiovascular disease are introduced. With the current routine practice of surgical closure of significant VSDs in the first 2 years of life, it is possible that the cardiopulmonary abnormalities produced by myocardial dysfunction or progressive pulmonary vascular disease, so easily demonstrated by exercise testing, will be avoided or minimized.

Interstitial pH during myocardial preservation: Assessment of five methods of myocardial preservation

We investigated changes in myocardial pH during cardioplegic arrest with five methods of preservation at 15 ° ± 1 °C. Twenty-five dogs were subjected to cardiopulmonary bypass for 150 minutes. Group I (control) had hypothermia only. Group II received THAM-buffered blood cardioplegia, group III a bicarbonate-buffered blood cardioplegic solution, group IV infusions of hyperkalemic blood, and group V oxygenated St. Thomas 2 solution. After 120 minutes of ischemia, interstitial pH in group I was markedly depressed (6.4 ± 0.07; p < 0.01). The pH in groups II and IV was well maintained (7.23 ± 0.05 and 7.27 ± 0.07) and differed significantly ( p < 0.05) from that of the remaining groups. The pH in groups III and V was less well maintained (7.14 ± 0.02 and 7.01 ± 0.05), with no significant difference ( p > 0.05) between these two groups. Postreperfusion functional recovery after 45 minutes was 24% ± 6% in group I, 92% ± 3% in group II, 82% ± 5% in group III, 84% ± 4% in group IV, and 66% ± 6% in group V. Creatine kinase levels were significantly ( p < 0.01) increased and ultrastructural damage was more prominent in group I compared with the remaining groups. Myocardial water content significantly increased in all groups. We conclude that a strongly buffered blood-based cardioplegic solution is more effective in preventing interstitial acidosis during moderate hypothermia and that maintenance of an optimal tissue pH plays an important role in postischemic functional recovery.

Risk analysis of low cardiac output syndrome after valve replacement.

In order to obtain a better understanding of the pathogenesis of the postoperative low cardiac output syndrome (LOS), a multivariate regression analysis was performed, evaluating predictive risk factors quantitatively as a function of plural preoperative variables. A total of 145 cases including 76 MVR (MS 36 MR 40), 42 AVR and 27 DVR were analyzed in this study. Ten historical, 10 hemodynamic and 4 operative risk factors were collected to compose the data file with corresponding status of postoperative cardiac function which was classified as follows. Patients who were not associated with postoperative LOS (Score 1), associated with the LOS which required and responded to ordinal dosage of a catecholamine (Score 2) associated with the LOS which required and responded to maximal dosage of the catecholamine and/or mechanical circulatory support (Score 3), and died of LOS (Score 4). Variables with significant relationships to postoperative LOS, regression equation to LOS score and their multiple correlation coefficients (R) of each group were as follows. MVR group: technical trouble (TT), extracorporeal circulation time (ECCT), change of myocardial preservation methods, delta LVSWI/delta LVEDP, diseased duration, aortic cross clamping time, CTR, Y = -1.16 + 1.01 (TT) + 0.05(ECCT) + 0.16(delta LVSWI/delta LVEDP) + 0.02(CTR), R = 0.76. AVR group: LVMMI, ECCT, cardiac failure, NYHA, Y = -0.71 + 0.03(LVMMI) + 0.004 (ECCT) + 0.22(NYHA), R = 0.78. DVR group: delta LVWI/delta LVEDP, LVMMI, NYHA, LV diastolic eccentricity ratio, ECCT, Y = -0.50 + 0.60 (delta LVWI/delta LVEDP) + 0.003(LVMMI) + 1.18(NYHA) + 0.38(delta LVSWI/delta LVEDP) + 0.003(ECCT), R = 0.87. It was demonstrated that preoperative ergometer exercise study during cardiac catheterization was useful in prediction of postoperative outcomes, especially in the MVR (MS) group.

Successful long-term preservation of the neonatal heart with a modified intracellular solution

Current methods of myocardial preservation for transplantation are suboptimal. A newly developed intracellular cardioplegic and storage solution (modified University of Wisconsin solution, group 1) was compared in a randomized, blinded fashion with our present clinical protocol, Stanford cardioplegic solution and saline storage (group 2) in an isolated neonatal pig model. After arrest and storage for 12 hours at 4 degrees C, biopsy specimens were taken from six group 1 hearts and five group 2 hearts for examination under an electron microscope and assessment of high-energy phosphate levels and water content. The remainder (group 1, n = 7; group 2, n = 6) were reperfused with blood for 50 minutes, after which function curves were obtained at left ventricular end-diastolic pressures of 3 to 12 mm Hg and biopsy tissue was taken. Eight control hearts (group 3) were cannulated in situ and perfused on the circuit without arrest or intervening ischemia. Stroke and minute work index curves were approximately threefold and fivefold higher for group 1 (modified University of Wisconsin solution) than for group 2 (Stanford), respectively (p less than 0.01). The hearts preserved with University of Wisconsin solution did not differ in function from unpreserved control hearts (group 3). High-energy phosphate levels were better maintained in group 1 than group 2 (p less than 0.05), and water content was lower (p less than 0.01). Semiquantitative grading of electron micrographs paralleled the functional and biochemical results. Modified University of Wisconsin intracellular solution provides markedly better heart preservation than conventionally used cardioplegic and storage solutions.

Pre-Oxygenated Crystalloid Cardioplegia

Since 1982, oxygenated crystalloid cardioplegia solution has become a popular method of myocardial preservation during cardiac surgery. The preferred method of oxygenated cardioplegia delivery has been the use of a recirculating delivery circuit that bubbles or films oxygen into the solution. Our present method allows us to pre-oxygenate the cardioplegia solution bags up to two weeks before using the oxygenated solution. The pO2 remains between 650-850 mmHg, and the oxygen content remains at 3.0-4.0 vol. %. The oxygenated cardioplegia maintains its sterility for as long as two weeks. The cost of oxygenating the cardioplegia is less than $1 per bag. Our delivery circuit requires no recirculating pump or sophisticated circuitry.

Post-infarction ventricular septal defect: the importance of site of infarction and cardiogenic shock on outcome.

Sixty-eight patients operated upon for post-infarction VSD from 1980-1987 have been reviewed to identify incremental risk factors which influence survival. Univariate and multivariate analysis was performed on 19 parameters and showed the following in decreasing order of importance to be significantly associated with non-survival: (1) operation within 24 h of occurrence of the VSD; (2) inferior infarct preceding the VSD; (3) requirement for inotropic support preoperatively; (4) preoperative cardiogenic shock; (5) a lower mean pulmonary artery pressure; (6) a lower mean wedge pressure; (7) a lower mean systolic pressure. The presence of a graft to the right coronary artery was associated with a better prognosis. Age, sex, diastolic blood pressure, balloon pumping, mean plasma urea, right atrial pressure, extent of coronary disease, number of coronary grafts, grafts to the left coronary system and method of myocardial preservation had no influence on survival.

Right and left ventricular metabolites

Current methods of cardioplegic delivery may delay the recovery of right ventricular metabolism and function. To evaluate right and left ventricular metabolism, we performed biopsies in 37 patients undergoing elective coronary bypass operation with aortic root blood cardioplegia. Right ventricular temperatures were warmer than left ventricular temperatures during cardioplegic arrest (right ventricle: 16.8 degrees +/- 3.8 degrees C, left ventricle: 14.3 degrees +/- 3.7 degrees C, p = 0.02). Adenosine triphosphate concentrations were lower in the right ventricle than in the left ventricle before cardioplegic arrest (right ventricle: 13.8 +/- 7.8 mmol/kg, left ventricle: 21.5 +/- 8.7 mmol/kg, p = 0.02). After reperfusion, right ventricular adenosine triphosphate concentrations fell to low levels (10 +/- 6 mmol/kg). Postoperative left and right ventricular high energy phosphate concentrations (the sum of adenosine triphosphate and creatine phosphate levels) correlated inversely with myocardial temperatures during cardioplegia (r = -0.29, p = 0.048). Aortic root cardioplegia did not cool the right ventricle as well as it did the left ventricle. The lower preoperative high energy phosphate concentrations may have increased the susceptibility of the right ventricle to ischemic injury. Alternative methods of myocardial preservation may improve right ventricular cooling and protection.

Protection of the Neonatal Heart Following Normothermic Ischemia: A Comparison of Oxygenated Saline and Oxygenated versus Nonoxygenated Cardioplegia

Optimal methods of myocardial preservation in the neonate remain unknown. Hypothermia and cardioplegia have been shown to protect neonatal hearts, but few studies have examined the effects of cardioplegia when administered at normothermia. Accordingly, the role of 37°C St. Thomas' cardioplegic solution in protecting the neonatal heart during 1 hour of ischemia in an isolated working rabbit heart model was examined. Both oxygenated and nonoxygenated cardioplegic solutions (CSs) were evaluated and compared with an oxygenated physiological saline solution (PSS). Following ischemia, control hearts were characterized by severely impaired left ventricular function, whereas all three treatment groups recovered well, indicating that the treatments provided substantial protection. Aortic flow recovered to 62, 63, and 57% of preischemic values for the oxygenated CS, nonoxygenated CS, and oxygenated PSS groups, respectively. Similarly, rate of change of pressure recovered to 76, 80, and 76% of preischemic values for oxygenated CS, nonoxygenated CS, and oxygenated PSS groups. All values were significantly greater than those for the control group. Recovery of developed pressure was significantly improved in all three groups. End-diastolic pressure rose markedly following ischemia in control hearts, was not increased after ischemia in hearts receiving oxygenated and nonoxygenated CS, but was increased in the oxygenated PSS group. These data indicate that crystalloid cardioplegia and oxygenated PSS provide substantial protection in neonatal rabbit hearts, even when delivered at 37°C. No additional benefit was seen when the cardioplegic solution was oxygenated. Therefore, either method of balancing the oxygen supply/demand ratio appears to be beneficial: supplying oxygen intermittently during ischemia (oxygenated PSS group) or decreasing oxygen demand during the ischemic period (cardioplegia groups).

Is High Potassium Solution Necessary for Reinfusions in “Multidose” Cold Cardioplegia? A Randomized Prospective Study Using Computerized Holter System

Multidose potassium cardioplegia is a common method of myocardial preservation. Although initial potassium arrest conserves high-energy phosphates, there is conflicting evidence that repeat high potassium boluses augment this protection. Fifty-six patients were prospectively randomized to receive multidose cold high potassium cardioplegia (27 mEq of KCl/L) both in the initial and subsequent infusions (Group 1) or an initial cold high potassium (27 mEq/L) cardioplegia followed by boluses of cold low potassium (7 mEq, of KCl/L) solution (Group 2). The two groups were compared in terms of postoperative myocardial electrical stability and hemodynamic performance. Electrocardiograms were recorded by continuous Holter monitor, and the data were analyzed by computer. The duration of aortic cross-clamping and cardiopulmonary bypass did not differ between groups. Group 1, who received more total KCl than Group 2 ( p < .005), experienced more high-grade ventricular ectopia during both reperfusion ( p < .001) and the immediate postoperative period ( p < .001), and required more lidocaine hydrochloride ( p < .001) for arrhythmias. There was no significant difference in hemodynamic performance between the two groups. This study fails to show an advantage to multidose “high potassium” cardioplegia and found a significant increase in ventricular ectopia associated with its use. We advocate using low potassium solutions after initial cold high potassium arrest.