Cardiac function and myocardial performance of 24-hour-preserved asphyxiated canine hearts.

A method of 24-hour storage of asphyxiated canine hearts for orthotopic cardiac transplantation was studied to expand the geographical size of the donor pool. Left ventricular function of asphyxiated hearts preserved for 24 hours (group 1, n = 8) was compared with that of hearts donated on-site (group 2, n = 5). Group 1 donors were pretreated with verapamil hydrochloride, propranolol hydrochloride, and prostacyclin. The donor hearts were perfused with warm blood cardioplegia in situ after 10 minutes of asphyxiation and then perfused with cold crystalloid cardioplegia for 2 hours. The hearts were excised and stored in ice-cold University of Wisconsin solution for 22 hours. At orthotopic transplantation, coronary perfusion with warm blood cardioplegia was performed before the graft aorta was unclamped. Conventional cardiac variables (eg, cardiac output and maximum rate of rise of left ventricular pressure), myocardial performance, and diastolic compliance of grafted hearts were assessed 1 hour after weaning from bypass. All recipients in both groups were easily weaned from cardiopulmonary bypass without inotropic agents, and there were no significant differences in cardiac variables between the two groups. These results strongly suggest that cadaver hearts can be preserved for 24 hours with satisfactory cardiac function.     

Successful transplantation after long-term preservation of dog hearts.

Nucleoside transport inhibition is a new approach to long-term preservation of donor hearts. To evaluate its effectiveness, the following were tested: 1) the effect of nucleoside transport inhibition on high-energy phosphate content after cardioplegic arrest and during long-term cold storage (group I: cardioplegia, control ]n = 18]; group II: cardioplegia plus nucleoside transport inhibitor [n = 18]); 2) the effect of nucleoside transport inhibition on high-energy phosphates and hemodynamic recovery in a modified blood-perfused Langendorff system (group III: 24-h cold storage followed by reperfusion [n = 6]; group IV: addition of nucleoside transport inhibition to cardioplegia but not during reperfusion [n = 6]; group V: addition of nucleoside transport inhibition during reperfusion [n = 6]; group VI: addition of nucleoside transport inhibition to cardioplegia and during reperfusion [n = 6]); and 3) the effect of nucleoside transport inhibition added to cardioplegia and during reperfusion on high-energy phosphate content and outcome after heart transplantation (group VII: no nucleoside transport inhibitor in cardioplegia and during reperfusion [n = 8]; group VIII: addition of nucleoside transport inhibition to cardioplegia and during reperfusion [n = 8]). The following results were obtained: 1) addition of nucleoside transport inhibition prevented high-energy phosphate depletion during cold storage: after 24 h, adenosine triphosphate content in group I was 9.4 +/- 3.1 mumol/g versus 17.7 +/- 3.6 mumol/g dry weight in group II (P less than 0.05); 2) addition of nucleoside transport inhibition to cardioplegia and during reperfusion resulted in greater high-energy phosphate content (adenosine triphosphate in group III was 7.9 +/- 3.5 mumol/g vs. 17.8 +/- 2.8 mumol/g in group VI [P less than 0.05]) and improved hemodynamics upon reperfusion (hearts in group III did not recover, maximum isometric left ventricular pressure development was 1,635 +/- 577 mmHg/sec in group IV, 1,915 +/- 423 mmHg/sec in group V, and 2,437 +/- 201 mmHg/sec in group VI [P less than 0.05, group VI vs. groups IV and V]); and 3) hearts treated with nucleoside transport inhibition in cardioplegia and during reperfusion (group VIII) could be transplanted successfully in contrast to group VII hearts. These data indicate that nucleoside transport inhibition in dogs is highly effective in long-term preservation of donor hearts.     

Myocardial viability twenty-four hours after orthotopic heart transplantation from non-heart-beating donors

OBJECTIVES: Using a new preservation strategy, we investigated the performance of hearts from non-heart-beating donors during an observation period of 24 hours after orthotopic heart transplantation in a pig model. METHODS: In the control group (n = 6) beating donor hearts were harvested with Bretschneider's HTK solution and transplanted orthotopically without reperfusion modifications. In the non-heart-beating donor group (n = 6) hearts were perfused with leukocyte-depleted blood cardioplegia after 30 minutes of normothermic ischemia. Blood cardioplegia was supplemented with a sodium-hydrogen exchange inhibitor and adenosine. After transplantation, a second controlled reperfusion with blood cardioplegia was performed. RESULTS: Preload recruitable stroke work of the left ventricle 24 hours after transplantation in the control versus non-heart-beating donor group was 108% +/- 24% versus 103% +/- 18% of baseline values. Myocardial blood flow of the left and right ventricle was increased to 146% +/- 32% and 176% +/- 51% in the control group versus 176% +/- 29% and 194% +/- 27% in the non-heart-beating donor group. Myocardial oxygen consumption was 11.2 +/- 2.1 versus 12.8 +/- 2.2 mL/100 g per minute at baseline and 11.6 +/- 2.6 versus 13.2 +/- 3.1 mL/100 g per minute after 24 hours (not significant). Histologic examination with Luxol fast blue staining revealed that 2.6% +/- 4.8% of myocytes in the control group versus 1.8% +/- 1.9% in the non-heart-beating donor group were damaged irreversibly. CONCLUSIONS: Recovery of donor hearts from non-heart-beating donors is comparable with recovery of organs harvested from heart-beating donors if the above-mentioned preservation technique is used. These results could encourage the use of marginal donor hearts and help to expand the limited donor pool.     

Evaluation of myocardial preservation using 31P NMR

The purpose of this study was (1) to monitor myocardial high-energy phosphate content and recovery of left ventricular (LV) contractile function following normothermic graded cardiac ischemia and single-dose hypothermic potassium cardioplegia, and (2) to assess the temporal limits of LV functional recovery during single-dose cardioplegia maintained at 17 degrees C. Rabbit hearts (30) were perfused, equipped with an LV balloon, paced at 240 beats/min, and placed in a nuclear magnetic resonance (NMR) magnet. Hearts underwent either graded, global normothermic ischemia or potassium cardioplegia arrest maintained at 17 degrees C for 1 hr. Myocardial high-energy phosphate level, LV contractility, and temperature were monitored continuously. Phosphocreatine (PCr) fell to 10 +/- 2, 2 +/- 1, and 0% of control and ATP to 70 +/- 3, 19 +/- 7, and 0% of control at 10, 40, and 60 min of 37 degrees C ischemia. After 1 hr of reperfusion, regression analysis of final developed pressure (DP) on end ischemic ATP (EIATP) content revealed: DP = 1.02 EIATP + 18 (r = 0.95). Following single-dose cardioplegia, maintained at 17 degrees C, PCr fell to 16 +/- 3% of control at 60 min while ATP fell only to 92 +/- 5% control. With reperfusion, recovery of DP was 100%. It was concluded that (1) PCr serves as an energy buffer for ATP, (2) EIATP predicts recovery of LV function, (3) single-dose cardioplegia maintained at 17 degrees C provides complete myocardial preservation for up to 60 min.     

Prolonged preservation of cadaver heart with Belzer UW solution: 24-hour storage system for asphyxiated canine hearts

The efficacy of Belzer UW solution was compared to Collins' solution in the preservation of asphyxiated cadaver hearts in a canine model. Donor hearts were stored for 24 h: 2 h of in situ hypothermic (15 degrees C) coronary perfusion plus 22 h of simple immersion in ice-cold solution. Verapamil, propranolol and prostacyclin were used for myocytoprotection in both groups. After orthotopic transplantation, all animals were weaned off bypass without inotropic support. After 1 h, however, the cardiac output was significantly higher in the Belzer UW solution group (128 +/- 28 vs. 67 +/- 13 ml/kg/min, p less than 0.01).     

Canine heart-lung transplantation after 24-hour hypothermic preservation

We compared the efficacy of Belzer UW solution (UWS) with modified Collins solution (MCS) in a 24 h canine heterotopic heart-lung transplantation model. Nine pairs of mongrel dogs were divided into 2 groups: MCS group (n = 5) and UWS group (n = 4). The donor heart was arrested with cardioplegia. The heart and lung were flushed with MCS or UWS, excised en bloc and immersed in 4 degrees C MCS or UWS for 24 h. Graft function was adequate in 1 of 5 grafts in the MCS group and in all 4 grafts in the UWS group (P less than 0.05). In the UWS group, the prepreservation and posttransplantation cardiac output was 71.2 +/- 21.6 and 96.4 +/- 44.4 ml/min per kg, the PaO2 was 80.8 +/- 12.9 and 74.1 +/- 2.7 mmHg, and the PaCO2 was 25.6 +/- 5.5 and 35.9 +/- 13.3 mmHg, respectively. No difference was significant. In the UWS group, the pulmonary vascular resistance increased significantly to 13.8 +/- 3.7 from 8.8 +/- 5.2 Wood units (P less than 0.05). Post-transplantation myocardial water content in the UWS group (78.6 +/- 2.0) was less than in the MCS group (81.1 +/- 1.4, P less than 0.05). The wet/dry ratio of the lung increased significantly to 8.3 +/- 1.6 from 4.4 +/- 0.6 in the UWS group (P less than 0.01) and to 10.3 +/- 0.8 from 4.1 +/- 0.1 in the MCS group (P less than 0.01), but was less in the UWS group (P less than 0.05). These results suggest that UWS is more effective than MCS in 24 h heart-lung preservation, but does not prevent pulmonary oedema adequately.     

Intermittent warm blood cardioplegia —An experimental study—

The influence of intermittent warm blood cardioplegia (WBCP) on myocardial function and metabolism was studied. Fourty-two adult mongrel dogs were used. The isolated heart of one dog was perfused by the cross circulation method with another support dog. The dogs then were divided into three groups. In group I (n=6), the empty beating heart was perfused with warm blood (WB) kept at 36°C for 100 minutes. In group II (n = 7), the arrested heart was perfused with continuous WBCP using modified Fremes solution for 100 minutes. In group III (n=8), the arrested heart was perfused with WBCP for 10 minutes following a 15-minute non-perfusion period. This perfusion method was repeated four times. The E max, LV developed pressure, ± LV dp/dt and LVEDP were all measured to evaluated the myocardial function. In addition, the coronary venous blood pH, myocardial oxygen consumption, myocardial lactate extraction, coronary blood flow, myocardial high energy phosphate content and myocardial water content were also studied in order to elucidate the myocardial metabolism. Regarding the myocardial function, no significant difference was observed between the three groups. The results of chemical studies on the myocardial metabolism were as follows: (1) the coronary venous blood pH in group III decreased at the end of the no perfusion period of WBCP. But it thereafter gradually returned to the normal physiological range; (2) the myocardial oxygen consumption in group III increased just after each interruption, but then gradually decreased toward following intermittent WBCP; (3) the myocardial lactate extraction decreased at the end of the non-perfusion period. However, it gradually returned to the control value by the end of each period of WBCP perfusion; (4) after 60 minutes of reperfusion, the coronary venous blood pH, myocardial oxygen consumption and myocardial lactate extraction showed no significant differences between the groups; (5) the coronary blood flow in group III increased significantly after 1 minute of reperfusion; (6) the ATP value in group III decreased significantly after 60 minutes of reperfusion. The ADP and AMP values demonstrated no significant difference between the groups during the same period; and (7) no significant difference was seen in the myocardial water content between the groups after 60 minutes of reperfusion. It is thus concluded that 10 minutes of intermittent WBCP followed by a 15-minute interruption appeared to have no deleterious effect on the myocardial funciton and metabolism.     

Improved neonatal heart preservation with an intracellular cardioplegia and storage solution

The optimal conditions for preservation of the neonatal heart for transplantation remain uncertain. An isolated, working neonatal piglet heart model was used to compare a standard extracellular-like cardioplegic solution followed by storage at 4 degrees C in normal saline for 12 hr (n = 8) to cardioplegia and storage at 4 degrees C for 24 hr in an intracellular-like solution (n = 7). Seven of eight hearts in the 12-hr Extracellular Group failed to regain function, with a maximum stroke work index (SWI), developed at a left ventricular end-diastolic pressure (LVEDP) of 9 mm Hg of 0.91 +/- 0.30 x 10(3) erg/g (mean +/- standard error of the mean), 7.1% of nonpreserved control hearts. In contrast, all hearts arrested and stored for 24 hr in the intracellular solution regained function with a maximum SWI, again at a LVEDP of 9 mm Hg of 9.51 +/- 1.98 X 10(3) erg/g, 73.7% of control (P less than 0.05). Ultrastructural changes seen by electron microscopy paralleled the functional results. We conclude that an intracellular arrest and storage solution may be superior to conventional solutions for extended preservation of the neonatal heart.     

Effects of heat stress on metabolism of high-energy phosphates. Comparison of normothermic and hypothermic ischemia.

BACKGROUND: Alterations in metabolic pathways may contribute to the cardioprotective effects of heat stress (HS). We investigated the effects of HS on ATP and phosphocreatine (PCr) levels in the ischemic rat myocardium, after both normothermic and hypothermic ischemia. METHODS: Two protocols were used: (1) normothermic ischemia (20 min at 37 degrees C) with no myocardial protection (n=6 HS; n=6 control); (2) hypothermic ischemia (4 hrs at 4 degrees C) after cardioplegic arrest (n=6 HS; n=6 control). ATP and PCr levels in the heart were measured using 31P nuclear magnetic resonance spectroscopy. RESULTS: At the end of normothermic ischemia, ATP levels were better maintained in HS hearts (C vs HS: 4.51+/-0.66 vs 7.81+/-1.06 micromol/g dry wt+/-SEM, p=0.04). A trend for higher ATP content in HS hearts was observed after 40 min of reperfusion (C vs HS: 11.7+/-1.5 vs 16.9+/-2.0 micromol/g dry wt+/-SEM, p=0.09). PCr content was also higher at the end of 40 minutes of reperfusion in HS hearts (C vs HS: 46.4+/-2.9 vs 56.9+/-3.0 micromol/g dry wt+/-SEM, p=0.03). After prolonged hypothermic ischemia under cardioplegic arrest, heat stress again led to better preservation of ATP levels at the end of ischemia (C vs HS: 5.71+/-0.88 vs 9.23+/-1.38 micromol/g dry wt+/-SEM, p=0.05) and after 40 minutes of reperfusion (C vs HS: 16.8+/-1.4 vs 24.6+/-2.8 micromol/g dry wt+/-SEM, p=0.03). PCr levels were also better maintained at the end of ischemia (C vs HS: 4.87+/-0.77 vs 12.4+/-3.0 micromol/g dry wt+/-SEM, p=0.03) and after 40 minutes of reperfusion in HS hearts (C vs HS: 55.1+/-7.0.vs 79.8+/-7.3 micromol/g dry wt+/-SEM, p=0.03). CONCLUSIONS: Heat stress induces changes in the energy profile of the heart which results in better preservation of ATP and phosphocreatine levels. These changes could be observed after brief normothermic ischemia and also after prolonged hypothermic ischemia under cardioplegic arrest, mimicking conditions of preservation for cardiac transplantation.     

Correlation between high adenosine triphosphate tissue concentration and good posttransplant outcome for the canine pancreas graft after preservation by the two-layer cold storage method.

Assessment of viability of a pancreas graft during preservation is very important to avoid transplantation of a nonfunctioning allograft. In the present report the correlation between adenosine triphosphate tissue concentration at the end of cold preservation by the two-layer method and viability a of canine pancreas graft following transplantation was studied. After preservation by an original two-layer (Euro-Collins' solution/perfluorochemical) method (group 1) and a modified two-layer (University of Wisconsin solution/PFC) method (group 2) for 24, 48, 72, 96, and 120 hr (subgroups A, B, C, D, and E), the tissue concentration of ATP was determined using high-performance liquid chromatography, and the viability of the pancreas graft was tested in the canine model of segmental pancreas autotransplantation. Maintenance of normoglycemia for at least five days after transplantation was considered to indicate a viable pancreas graft. In group 1, functional success rates were A: 5/5, (100%), B: 4/4 (100%), C: 4/4, (100%), and D: 0/4 (0%), respectively. The ATP tissue concentrations were 7.47 +/- 0.47 (n = 5), 7.91 +/- 1.21 (n = 4), 8.29 +/- 0.21 (n = 4), and 4.94 +/- 1.11 (n = 4) mumol/g dry weight in groups 1A, 1B, 1C, and 1D, respectively. There was a statistically significant difference between viable groups (groups 1A, 1B, and 1C, 7.86 +/- 0.77 mumol/g dry weight [n = 13]) and the nonviable group (group D, 4.94 +/- 1.11 mumol/g dry weight (n = 4) (P less than 0.01). On the other hand, the functional success rates were 3/3 (100%), 3/3 (100%), 3/3 (100%), 5/7 (71%), and 0/3 (0%) in groups 2A, 2B, 2C, 2D, and 2E, respectively. Two of seven dogs died of causes related to the grafts (pancreatitis and thrombosis). The ATP tissue concentrations were 8.53 +/- 1.45 (n = 3), 9.64 +/- 1.77 (n = 3), 13.81 +/- 2.09 (n = 3), and 12.49 +/- 2.52 (n = 5) mumol/g dry weight in groups 2A, 2B, and 2C and in viable grafts in group 2D, respectively, but the ATP tissue concentration of nonviable grafts in group 2D and group E were 3.51 +/- 0.81 (n = 2) and 3.98 +/- 1.34 (n = 3) mumol/g dry weight, respectively. There was a statistically significant difference between viable groups (groups 2A, 2B, 2C and viable grafts in group 2D, 11.03 +/- 2.72 mumol/g dry weight [n = 14]) and nonviable groups (group E and nonviable grafts in group 2D, 3.79 +/- 1.06 mumol/g dry weight [n = 5]) (P less than 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)     

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.     

Enflurane enhances postischemic functional recovery in the isolated rat heart

Enflurane is a direct myocardial depressant and may act as a myocardial protective agent during ischemia. The authors studied the effects of enflurane on myocardial high-energy phosphates and tolerance to ischemia in the normothermic, isolated rat heart. After isolation and perfusion with Krebs-Henseleit buffer, the hearts were perfused with either buffer (control) or buffer gassed with 2% enflurane for 10 minutes. Thereafter, hearts were made globally ischemic and elapsed times to initiation of ischemic contracture (IC) were determined. ATP and creatine phosphate (CP) were measured at the conclusion of control and enflurane administration and at IC. Ten hearts per group were reperfused with buffer following IC for 20 min; peak pressure and ATP and CP were determined. Administration of 2% enflurane significantly decreased peak pressure by 20% but did not alter baseline high-energy phosphate levels nor did it prolong time to IC. However, enflurane-treated hearts exhibited significantly greater (P less than 0.01) recovery of function as defined by per cent return of peak pressure (67% +/- 3%) when compared with those hearts not treated with enflurane preischemically (44% +/- 5%). Also, enflurane-treated hearts had significantly higher (P less than 0.01) ATP levels at the conclusion of reperfusion than hearts not perfused with enflurane (12.2 +/- .8 mumol/g dry weight vs. 9.0 +/- 0.8 mumol/g dry weight). These findings suggest that enflurane administered prior to an ischemic interval enhances postischemic myocardial recovery.     

Effects of supplemental L-arginine during warm blood cardioplegia.

OBJECTIVES: Effects of supplemental L-arginine, nitric oxide precursor, during warm blood cardioplegia were assessed in the blood perfused isolated rat heart. METHODS: The isolated hearts were perfused with blood at 37 degrees C from a support rat. After 20 minutes of aerobic perfusion, the hearts were arrested for 60 minutes with warm blood cardioplegia given at 20-minute intervals. This was followed by 60 minutes of reperfusion. The hearts were divided into the following three groups according to the supplemental drugs added to the cardioplegic solution. The control group (n = 10) received standard warm blood cardioplegia. The L-ARG group (n = 10) received warm blood cardioplegia supplemented with L-arginine (3 mmol/l). The L-NAME group (n = 10) received warm blood cardioplegia supplemented with L-arginine (3 mmol/l) and L-nitro-arginine methyl ester, a competitive inhibitor of nitric oxide synthase (1 mmol/l). After 60 minutes of cardioplegic arrest, cardiac function, myocardial metabolism and myocardial release of circulating adhesion molecules were measured during reperfusion. RESULTS: Left ventricular end-diastolic pressure was significantly lower (p<0.05) in the L-ARG group than in the control group and the L-NAME group during reperfusion. Isovolumic left ventricular developed pressure, dp/dt and coronary blood flow were significantly greater (p< 0.05) in the L-ARG group during reperfusion. The L-ARG group resulted in early recovery of lactate metabolism during reperfusion. Myocardial release of circulating intercellular adhesion molecule-1 (ICAM-1) and E-selectin were significantly less (p<0.05) in the L-ARG group at 15 minutes of reperfusion. CONCLUSIONS: The results suggest that augmented nitric oxide by adding L-arginine to warm blood cardioplegia can preserve left ventricular function and ameliorate endothelial inflammation. The technique can be a novel cardioprotective strategy in patients undergoing cardiac surgery.     

Erythrocyte-containing versus crystalloid cardioplegia in the rat: effects on myocardial capillaries

BACKGROUND: The purpose of this study was to investigate the effects of crystalloid and erythrocyte-containing cardioplegia on capillary morphology of the isolated erythrocyte-perfused rat heart. METHODS: Hearts from adult Sprague-Dawley rats were perfused throughout with resuspended sheep erythrocytes and subjected to the following protocols (n = 6, all groups): (1) 15 minutes nonworking and 30 minutes working heart mode (control; group 1); (2) as for group 1, with 30 minutes erythrocyte-containing (BL) or crystalloid (CR) cardioplegic arrest without reperfusion (groups 2BL and 2CR); (3) as for group 2, with 30 minutes nonworking reperfusion (groups 3BL and 3CR); and (4) as for group 3, with 30 minutes working heart mode (groups 4BL and 4CR). After each protocol troponin I from coronary effluent was measured. Corrosion casts were then made of the coronary microvasculature. Cast density was calculated as cast volume per left ventricular dry weight. Casts also underwent scanning electron microscopy. Analysis was by analysis of variance. Values are mean +/- standard deviation. RESULTS: Prearrest working heart coronary flow averaged 15.1 +/- 4.7 mL/min without any differences among groups. Coronary flow in group 4 working hearts was the same before and after either cardioplegia. Cardiac outputs were similarly consistent in all groups. Cast density in group 1 (control) was 9.60 +/- 1.17 x 10(-2) mm3/mg. It was unaltered by erythrocyte-containing cardioplegia, but after crystalloid cardioplegia (group 2CR), it was 6.52 +/- 0.93 x 10(-2) mm3/mg (p = 0.0001 versus group 1 and p = 0.0007 versus group 2BL). With 30 minutes of nonworking reperfusion (group 3CR, there was slight improvement in cast density at 7.60 +/- 0.90 x 10(-2) mm3/mg (p = 0.0072 versus group 1; p = 0.0242 versus group 3BL). No further improvement was seen in group 4CR. Electron micrographs showed circumferential angularities or narrowings in crystalloid-perfused, arrested hearts, consistent with ischemic damage. Troponin I rose significantly after reperfusion in all groups, but it was higher in crystalloid-perfused, arrested hearts: 0.054 +/- 0.013 microg/L versus 0.024 +/- 0.017 microg/L (p = 0.0273). CONCLUSIONS: Erythrocyte-containing cardioplegia maintained capillary density and morphology. Crystalloid cardioplegia produced capillary loss, visible abnormalities, and higher troponin I release. These hearts may be more vulnerable to myocardial damage during reperfusion than hearts perfused with erythrocyte-containing cardioplegic solution.     

The effects of cardioplegia washout on myocardial preservation

Preservation of the myocardium in vitro is more effective than preservation in vitro when preservation conditions are apparently the same. The washout of cardioplegia from the myocardium by noncoronary blood flow has been implicated as a probable cause of the poorer myocardial preservation seen in vivo. Isolated dog hearts were used to study the effects of cardioplegia washout by low flow perfusion (0.05 ml/min/g LV weight) during a 2-hr preservation period. Six experimental groups of five hearts each underwent 2 hr of myocardial preservation at temperatures of 20 degrees C (three groups) or 30 degrees C (three groups). The three groups for each temperature consisted of retrograde coronary sinus perfusion (to simulate cardioplegia washout by collateral flow) with blood cardioplegia (BC), normal blood (NB), or no perfusion at all (No CSP). The quality of preservation in each group was assessed by measuring recovery of left ventricular function, tissue water and electrolyte content, and myocardial high-energy phosphate and adenylate content prior to, during, and following preservation. In hearts maintained at 20 degrees C, cardioplegia washout did not significantly affect left ventricular function or myocardial levels of H2O, Na, K, ATP, or total adenylates. When myocardial temperature was allowed to increase to 30 degrees C, preservation was better with low flow perfusion during the preservation period. Hearts warmed to 30 degrees C with no cardioplegia washout experienced a 50% loss of tissue ATP levels and recovered less than 30% of normal left ventricular function during a 150-min reperfusion period. In contrast, hearts slowly perfused during the preservation period maintained nearly normal levels of ATP and returned to normal function by 150 min of reperfusion. Although myocardial warming by noncoronary perfusion has a detrimental effect on myocardial preservation, the slow washout of cardioplegia per se has no apparent detrimental effect on preservation.     

Prolonged preservation of the blood-perfused canine heart with glycolysis-promoting solution.

BACKGROUND: Prolonged ischemia and inadequate myocardial preservation remain significant perioperative risk factors in cardiac transplantation. Long-term preservation techniques that have been effective in small rodent hearts have not been as effective in larger animal models or in clinical studies. We developed a cardioplegia solution formulated to promote high-energy phosphate production from glycolysis and determined its efficacy in a blood perfused canine heart model subjected to 24 hours of ischemia. METHODS: Hearts harvested from adult dogs (n = 6 per group) were flushed with a histidine-buffered cardioplegia solution containing glucose or University of Wisconsin solution. The hearts were maintained at 4 degrees C for 24 hours then reperfused with autologous blood. After reperfusion, left ventricular pressures were measured with an intracavitary balloon at varying balloon volumes and compared with control nonischemic hearts. Predicted stroke volume and ejection fraction were calculated at an end-systolic pressure of 70 mm Hg and end-diastolic pressure of 15 mm Hg. RESULTS: Developed pressure was better preserved in the hearts that received histidine-buffered solution (93+/-9 versus 38+/-7 mm Hg, p<0.05), along with a higher end-diastolic volume at 15 mm Hg (31+/-3 versus 22+/-2 mL histidine-buffered versus University of Wisconsin solutions, respectively, p<0.05). Stroke volume and ejection fraction were also higher in the histidine group (17+/-2.5 versus 2.3+/-1.2 mL and 50%+/-3.5% versus 9% +/-4.5%, respectively) in the presence of dobutamine. CONCLUSIONS: The highly buffered glycolysis-promoting cardioplegia solution provided effective preservation of the blood perfused canine heart with superior recovery of pump performance after 24 hours of hypothermic ischemia compared with University of Wisconsin solution in this model.     

Insulin effects on pantothenic acid uptake in isolated perfused working hearts from diabetic rats

Pantothenic acid uptake was studied in isolated working hearts from spontaneously diabetic BB Wistar and streptozocin-induced diabetic (STZ-D) rats. If insulin treatment was stopped for a 24-h period from spontaneously diabetic rats, a significant decrease in the rate of pantothenic uptake was noted (from 147.3 +/- 5.0 to 110.8 +/- 10.6 nmol.g-1 dry wt.30 min-1). Pantothenic acid uptake rates were also reduced in 48-h STZ-D rats (118.0 +/- 6.1 nmol.g-1 dry wt.30 min-1, compared to 158.2 +/- 5.3 in control rats). The decrease in pantothenic acid uptake in all diabetic animals occurred whether hearts were perfused with 1.2 mM palmitate or 1.2 mM palmitate and 11 mM glucose. If insulin (500 microU/ml) was added to the perfusion medium of hearts from spontaneously diabetic rats perfused with palmitate and glucose, a significant increase in pantothenic acid uptake was noted (from 110.8 +/- 10.6 to 167.0 +/- 9.4 nmol.g-1 dry wt.30 min-1). Insulin had no significant effect on pantothenic acid uptake in hearts from spontaneously diabetic rats perfused with palmitate alone. In STZ-D rats, insulin added to hearts perfused with palmitate and glucose resulted in a small but significant increase in pantothenic acid uptake (from 118.0 +/- 6.1 to 130.6 +/- 4.0 nmol.g-1 dry wt.30 min-1). Insulin had no effect on pantothenic acid uptake in control hearts perfused either in the presence or absence of glucose. These data suggest that insulin, in the presence of glucose, can increase pantothenic acid uptake in diabetic rats.     

Adenosine cardioplegia. Adenosine versus potassium cardioplegia: effects on cardiac arrest and postischemic recovery in the isolated rat heart

Adenosine is a potential cardioplegic agent by virtue of its specific inhibitory properties on nodal tissue. We tested the hypothesis that adenosine could be more effective than potassium in inducing rapid cardiac arrest and enhancing postischemic hemodynamic recovery. Isolated rat hearts were perfused with Krebs-Henseleit buffer or cardioplegic solutions to determine the time to cardiac arrest and the high-energy phosphate levels at the end of cardioplegia. Cardioplegic solutions contained adenosine 10 mmol/L, potassium 20 mmol/L, or adenosine 10 mmol/L + potassium 20 mmol/L and were infused at a rate of 2 ml/min for 3 minutes at 10 degrees C. Both time taken and total number of beats to cardiac arrest during 3 minutes of cardioplegia were reduced by adenosine 10 mmol/L and adenosine 10 mmol/L + potassium 20 mmol/L when compared with potassium 20 mmol/L alone (p less than 0.001). Tissue phosphocreatine was conserved by adenosine 10 mmol/L when compared with potassium 20 mmol/L, being 7.1 +/- 0.2 (mumol/gm wet weight (n = 7) and 6.0 +/- 0.3 mumol/gm wet weight (n = 5), respectively (p less than 0.05). Postischemic hemodynamic recovery was tested in isolated working rat hearts. After initial cardiac arrest, the cardioplegic solution was removed with Krebs-Henseleit buffer at a rate of 2 ml/min for 3 minutes at 10 degrees C, and thereafter total ischemia was maintained for 30 or 90 minutes at 10 degrees C before reperfusion. Adenosine 10 mmol/L enhanced recovery of aortic output when compared with potassium 20 mmol/L or adenosine 10 mmol/L + potassium 20 mmol/L, the percentage recovery after 30 minutes of ischemia being 103.0% +/- 4.4% (n = 6), 89.0% +/- 5.8% (n = 6), and 86.6% +/- 4.3% (n = 6), respectively (p less than 0.05 for comparison between adenosine 10 mmol/L and potassium 20 mmol/L). Thus adenosine cardioplegia caused rapid cardiac arrest and improved postischemic recovery when compared with potassium cardioplegia and with a combination of these two agents.     

Low-potassium University of Wisconsin solution for cardioplegia: improved protection of the isolated ischemic neonatal rabbit heart

Recovery of cardiac function and high-energy phosphates following ischemia and reperfusion were determined for hearts perfused with low potassium University of Wisconsin solution, high potassium University of Wisconsin solution, St Thomas' solution, or subjected to hypothermia alone. Isolated hearts were arrested for either 3 h at 15 degrees C or 6 h at 20 degrees C (n = 7 for each group) with one of the four solutions and then reperfused. Aortic flow after ischemic arrest at 20 degrees C was 40.3 +/- 13.3%, 79.3 +/- 10.0%, 64.3 +/- 11.9% and 43.9 +/- 15.9% of control values for high potassium University of Wisconsin solution, low potassium University of Wisconsin solution, St Thomas' solution and hypothermia alone, respectively. Similar results were observed in hearts subjected to ischemic arrest at 15 degrees C. Myocardial adenosine triphosphate and creatine phosphate after reperfusion tended to be higher in the low potassium University of Wisconsin solution group. It is concluded that low potassium University of Wisconsin solution may provide reliable cardioplegia during surgery that requires prolonged cardiac arrest in neonates and infants.     

The effect of graft perfusion with warm blood cardioplegia for cadaver heart transplantation

This study was designed to verify the effect of reperfusion of donor hearts in a perfusion apparatus after 60 min of global ischemia prior to heart transplantation. Thirteen dogs were exsanguinated from the femoral artery and cardiac arrest was achieved. The hearts were left in situ at room temperature (25°C)for 60 min. In group A (n=7), the hearts were excised and reperfused 60 min after cardiac arrest in the perfusion apparatus with substrate-enriched warm blood cardioplegia (WBCP) containing a hydroxyl radical scavenger, EPC, followed by 45 min of blood perfusion, Next, the hearts were preserved in cold (4°C) University of Wisconsin (UW) solution. In group B (n=6), the hearts were perfused with cold (4°C) St. Thomas' solution 60 min after cardiac arrest and preserved in cold UW solution. Thereafter, all hearts in both groups were transplanted orthotopically to recipient dogs. In group A, 6 of 7 dogs were weaned from cardiopulmonary bypass (CPB). In group B, only 2 of 6 dogs were weaned from CPB. Moreover, 3 of the 6 hearts in group B did not start beating after transplantation (stone heart). This study suggested reperfusion of the donor heart in the perfusion apparatus with WBCP to be a beneficial preconditioning method when utilizing 60-min arrested hearts for transplantation. This study was supported in part by Senju Pharmaceutical Co. Ltd., Osaka, Japan