Preconditioning improves myocardial function and reflow, but not vasodilator reactivity, after ischaemia and reperfusion in anaesthetized dogs

1. The present study examines whether three cycles of brief coronary artery occlusion and reperfusion (i.e. ischaemic preconditioning; PC) can prevent vasodilator dysfunction and the impairment of myocardial reflow caused by prolonged ischaemia. Coronary blood flow, left ventricular dP/dt, systemic arterial blood pressure and heart rate were measured in open-chest anaesthetized dogs. 2. Sixty minute occlusion of the left circumflex coronary artery (LCx) and 60 min LCx reperfusion (ISC/REP; group 1) significantly reduced resting coronary blood flow (CBF, initial 29 +/- 3 mL/min; ISC/REP 20 +/- 3 mL/min, P < 0.05 vs initial) and increased coronary vascular resistance (CVR, initial 4.1 +/- 0.6 mmHg/min per mL; ISC/REP 5.8 +/- 1.0 mmHg/min per mL, P < 0.05 vs initial). By contrast CBF and CVR were not affected in dogs subjected to preconditioning before ischaemia (group 2: CBF, initial 24 +/- 4 mL/min; PC+ISC/REP 23 +/- 4 mL/min; CVR, initial 4.7 +/- 0.6 mmHg/min per mL; PC+ ISC/REP 5.3 +/- 1.0 mmHg/min per mL). These data suggest that ischaemic preconditioning prevents the ischaemia-induced impairment of myocardial reflow. 3. Ischaemia and reperfusion impaired coronary dilator responses to the endothelium-dependent dilator acetylcholine (delta CBF, after ISC/REP: 50 +/- 6% of initial) and the endothelium-independent dilator glyceryl trinitrate (delta CBF, ISC/REP: 46 +/- 6% of initial). Despite the improvement in reperfusion in the preconditioned group, there was no significant improvement in responses to acetylcholine (PC+ISC/REP 52 +/- 6% of initial) or glyceryl trinitrate (PC+ISC/REP 59 +/- 6% of initial) after ischaemia and reperfusion. 4. The reduction in left ventricular dP/dt after ischaemia and reperfusion was significantly smaller in the preconditioned group indicating a lower level of impairment of cardiac contractility. In addition, we confirmed that preconditioning caused a significant reduction in infarct size and a reduction in the release of lactate dehydrogenase indicating less cardiac injury. 5. These results suggest that although ischaemic preconditioning was able to improve both myocardial reperfusion and contractility, it was not able to preserve vasodilator function. Such a reduction in vasodilator reserve could prevent adequate myocardial perfusion under conditions of elevated oxygen demand.     

Alpha 1-adrenoceptor activation mediates the infarct size-limiting effect of ischemic preconditioning through augmentation of 5'-nucleotidase activity

We have reported that ischemic preconditioning may limit infarct size by increasing 5'-nucleotidase activity. The present study tested whether alpha 1-adrenoceptor stimulation in ischemic preconditioning mediates the infarct size-limiting effect through augmentation of 5'-nucleotidase activity. The coronary artery was occluded four times for 5 min separated by 5 min of reperfusion (ischemic preconditioning) in 82 dogs. Then the coronary artery was occluded for 90 min followed by 6 h of reperfusion. Infarct size normalized by risk area was smaller after ischemic preconditioning than in the control group (40.6 +/- 2.3 vs 6.7 +/- 2.0%, P < 0.001), even though no difference existed in endomyocardial collateral flow during ischemia (8.7 +/- 1.0 vs 8.9 +/- 1.0 ml/100 g per min). Ectosolic and cytosolic 5'-nucleotidase activity was increased after ischemic preconditioning. However, prazosin blunted the infarct size-limiting effect of ischemic preconditioning (infarct size: 42.8 +/- 3.7%). Intermittent alpha 1-adrenoceptor stimulation by methoxamine mimicked the increase in 5'-nucleotidase activity and the infarct size-limiting effect, which were abolished by alpha, beta,-methyleneadenosine 5'-diphosphate. Identical results were obtained in the conscious model (n = 20). Therefore, we conclude that increases in ectosolic 5'-nucleotidase activity due to alpha 1-adrenoceptor activation may contribute to the infarct size-limiting effect of ischemic preconditioning.     

Gradual reperfusion reduces infarct size and endothelial injury but augments neutrophil accumulation

BACKGROUND: Reperfusion causes injury to the coronary artery endothelium primarily by neutrophil-mediated mechanisms. However, factors other than neutrophils may govern the extent of myocardial necrosis. This study tests the hypothesis that gradual initiation of reflow will reduce reperfusion injury and preserve postischemic endothelial function. METHODS: In 16 anesthetized dogs, the left anterior descending artery was ligated for 60 minutes. In one group, reperfusion was initiated abruptly (abrupt, n = 8), whereas in the gradual reperfusion group (ramp, n = 8), flow was slowly initiated during the first 30 minutes of reperfusion. After reperfusion, coronary artery segments were isolated to assess postischemic endothelial function. RESULTS: Infarct size (area of necrosis/area at risk) was significantly reduced in the ramp group (28.2% +/- 2.0%) compared with abrupt (41.6% +/- 1.4%). Neutrophil accumulation (myeloperoxidase) in the area at risk was significantly greater in the ramp group compared with abrupt (8.0 +/- 1.3 versus 3.5 +/- 0.8 U/g tissue). In isolated postischemic left anterior descending arterial rings, the concentration of acetylcholine that elicited a response 50% of the maximum possible response was significantly greater in abrupt (-6.88 +/- 0.04 log [mol/L]) than ramp (-7.62 +/- 0.04 log [mol/L]) and control (-7.68 +/- 0.003 log [mol/L]), suggesting endothelial dysfunction. The concentration of A23187 that elicited a response 50% of the maximum possible response was similarly greater in abrupt (-7.24 +/- 0.03 log [mol/L]) versus ramp (-7.62 +/- 0.03 log [mol/L]) and control (-7.8 +/- 0.04 log [mol/L]). Smooth muscle dysfunction (response to sodium nitrite) also occurred in the abrupt rings. CONCLUSIONS: Gradual reperfusion of an ischemic area reduces infarct size and preserves endothelial function but paradoxically increases neutrophil accumulation within the area at risk.     

Molecular basis of type III hyperlipoproteinemia in Germany

1. The aim of the present investigation was to evaluate the effect of cloricromene on myocardial infarct size, regional myocardial blood flow and neutrophil accumulation in a canine model of ischaemia-reperfusion. 2. Dogs were instrumented to measure blood pressure, left anterior descending (LAD) coronary flow (flow probe) and regional myocardial blood flow (coloured microspheres). Two groups were studied: (i) CLO (n = 8) received an infusion of cloricromene (15 micrograms/kg per min); and (ii) VEH (n = 8) received saline. Infusions began at the onset of ischaemia (60 min) and continued through reperfusion (180 min). 3. Haemodynamic responses were not different between groups. Cloricromene reduced the area of necrosis expressed as a percentage of the area at risk from 35 +/- 3% in the VEH group to 23 +/- 4% in the CLO group (P < 0.05). Regional myocardial blood flow in the ischaemic region was different between groups; VEH dogs showed an early reperfusion hyperaemia followed by a progressive reduction in flow, while CLO dogs exhibited a gradual increase in reflow in the absence of an early hyperaemic response (P < 0.05). Left anterior descending flow was enhanced during the reperfusion period in the CLO group compared with VEH (P < 0.05). Cloricromene reduced polymorphonuclear neutrophil (PMN) infiltration (myeloperuxidase activity) in all myocardial regions when compared with VEH (non-ischaemic zone, 0.34 +/- 0.54 vs 0.05 +/- 0.01 IU/100 mg; ischaemic zone, 2.03 +/- 0.80 vs 0.24 +/- 0.08 IU/100 mg; and necrotic zone, 0.56 +/- 0.04 vs 3.59 +/- 1.09 IU/100 mg for VEH vs CLO groups, respectively; P < 0.01). In a separate in vitro preparation, cloricromene reduced adherence of platelet-activating factor (PAF)-stimulated PMN to canine coronary endothelium. Stimulation of PMN by 100 nmol/L PAF resulted in adherence of 176 +/- 36 compared with 48 +/- 12 cells/mm2 in PAF-stimulated PMN treated with 100 mumol cloricromene (P < 0.001). 4. These data indicate that cloricromene reduces myocardial infarct size in a canine model of ischaemia-reperfusion injury. Postischaemic blood flow patterns are significantly different in cloricromene-treated dogs. Cloricromene-mediated reductions in infarct size, neutrophil accumulation and adherence may play a role in this effect.     

Cardioprotective effects of the novel adenosine A1/A2 receptor agonist AMP 579 in a porcine model of myocardial infarction

This study examined the cardioprotective effects and pharmacology of the novel adenosine A1/A2 receptor agonist ([1S-[1a,2b,3b, 4a(S*)]]-4-[7-[[2-(3-chloro-2-thienyl)-1-methylpropyl]amino]-3H-imida zo[4,5-b] pyridyl-3-yl] cyclopentane carboxamide) (AMP 579), in a model of myocardial infarction. Experiments were performed in pentobarbital-anesthetized pigs in which myocardial infarction was induced by a 40-min occlusion of the left anterior descending coronary artery, followed by 3 hr of reperfusion. This procedure resulted in approximately 20% of the left ventricle being made ischemic in all test groups. In untreated animals, an infarct size equal to 56 +/- 5% of the ischemic area was observed. Preconditioning, with two cycles of 5 min of ischemia followed by 10-min reperfusion, resulted in a 70% reduction in infarct size (17 +/- 5%) relative to risk area. Administration of AMP 579 30 min before ischemia (3 microg/kg i.v. followed by 0.3 microg/kg/min i.v. through 1 hr of reperfusion) did not change blood pressure, HR or coronary blood flow but resulted in marked cardioprotection: a 98% reduction in infarct size (1 +/- 1%) relative to risk area. Moreover, whereas approximately 90% of control pigs suffered ventricular fibrillation during ischemia, no fibrillation was observed in animals treated with AMP 579. Further experiments determined the effects of AMP 579 when administered 30 min after the onset of myocardial ischemia, 10 min before reperfusion. Two doses were studied: a low hemodynamically silent dose (3 microg/kg + 0.3 microg/kg/min through 1 hr of reperfusion) and a 10-fold higher dose that did cause reductions in blood pressure and HR. Both doses of AMP 579 produced a comparable cardioprotective effect, reducing infarct size to approximately 50% of that observed in control animals. The cardioprotective effect of AMP 579 was a consequence of adenosine receptor stimulation, because it was completely inhibited by pretreatment with the specific adenosine receptor antagonist CGS 15943 (1 mg/kg i.v.). However, the selective A1 receptor agonist GR 79236 (3 microg/kg + 0.3 microg/kg/min i.v.) did not reduce infarct size, which suggests that under these experimental conditions, stimulation of adenosine A2 receptors is important for the cardioprotective effect of AMP 579. The adenosine-regulating agent acadesine (5 mg/kg + 0.5 mg/kg/min i.v.) also failed to reduce infarct size. In conclusion, the novel adenosine A1/A2 receptor agonist AMP 579 produces marked cardioprotection whether administered before myocardial ischemia or reperfusion. Cardioprotection is not dependent on changes in afterload or myocardial oxygen demand and is a consequence of adenosine receptor stimulation. The pharmacological profile of AMP 579 in this model is consistent with its potential utility in the treatment of acute myocardial infarction.     

A Ca channel blocker, benidipine, increases coronary blood flow and attenuates the severity of myocardial ischemia via NO-dependent mechanisms in dogs

OBJECTIVES: This study was undertaken to examine whether a dihydropyridine Ca channel blocker, benidipine, increases cardiac NO levels, and thus coronary blood flow (CBF) in ischemic hearts. BACKGROUND: Benidipine protects endothelial cells against ischemia and reperfusion injury in hearts. METHODS AND RESULTS: In open chest dogs, coronary perfusion pressure (CPP) of the left anterior descending coronary artery was reduced so that CBF decreased to one-third of the control CBF, and thereafter CPP was maintained constant (103+/-8 to 42+/-1 mmHg). Both fractional shortening (FS: 6.1+/-1.0%) and lactate extraction ratio (LER: -41+/-4%) decreased. Ten minutes after the onset of an intracoronary infusion of benidipine (100 ng/kg/min), CBF increased from 32+/-1 to 48+/-4 ml/100g/ min during 20 min without changing CPP (42+/-2 mmHg). Both FS (10.7+/-1.2%) and LER (-16+/-4%) also increased. Benidipine increased cardiac NO levels (11+/-2 to 17+/-3 nmol/ml). The increases in CBF, FS, LER and cardiac NO levels due to benidipine were blunted by L-NAME. Benidipine increased cyclic GMP contents of the coronary artery of ischemic myocardium (139+/-13 to 208+/-15 fmol/mg protein), which was blunted by L-NAME. CONCLUSION: Thus, we conclude that benidipine mediates coronary vasodilation and improves myocardial ischemia through NO-cyclic GMP-dependent mechanisms.     

Peroxynitrite: a biologically significant oxidant

A prolongation of the intracellular acidosis after myocardial ischemia can protect the myocardium against reperfusion injury. In isolated hearts, this was achieved by prolongation of the extracellular acidosis. The aim of this study was to investigate whether regional reperfusion with acidotic blood after coronary artery occlusion can reduce infarct size and improve myocardial function in vivo. Anesthetized open-chest dogs were instrumented for measurement of regional myocardial function, assessed by sonomicrometry as systolic wall thickening (sWT). Infarct size was determined by triphenyltetrazolium staining after 3 h of reperfusion. The left anterior descending coronary artery (LAD) was perfused through a bypass from the left carotid artery. The animals underwent 1 h of LAD occlusion and subsequent bypass-reperfusion with normal blood (control, n = 6) or blood equilibrated to pH = 6.8 by using 0.1 mM HCl during the first 30 min of reperfusion (HCl, n = 5). Regional collateral blood flow (RCBF) at 30-min occlusion was measured by using colored microspheres. There was no difference in recovery of sWT in the LAD-perfused area between the two groups at the end of the experiments [-2.8+/-1.2% (HCl) vs. -4.4+/-2.5% (control); mean +/- SEM; p = NS]. RCBF was comparable in both groups. Infarct size (percentage of area at risk) was reduced in the treatment group (12.8+/-2.8%) compared with the control group (26.2+/-4.8%; p < 0.05). These results indicate that reperfusion injury after coronary artery occlusion can be reduced by a prolonged local extracellular acidosis in vivo.     

Preconditioning of rat heart with monophosphoryl lipid A: a role for nitric oxide

Preconditioning with monophosphoryl lipid A (MLA) protects rabbit hearts from prolonged ischemic reperfusion injury by a mechanism involving inducible nitric oxide synthase (iNOS) activation. This study was undertaken to determine whether MLA also could precondition rat hearts in a similar manner. Rats were injected with two different doses of MLA (300 microg/kg or 450 microg/kg i.v.) or vehicle (control), and after 24 hr the animals were sacrificed for preparation of isolated perfused rat hearts. Hearts were then perfused by working mode, and then made ischemic for 30 min followed by 30 min of reperfusion. Another group of hearts were treated simultaneously with a nitric oxide (NO) blocker, L-nitro-arginine-methyl-ester (L-NAME) (10 mg/kg) and MLA (450 microg/kg). For arrhythmia studies, 12 hearts were used in each group (total, 48 hearts). Cardiac functions were examined in a separate group of 24 hearts (n = 6/group). MLA-treated hearts (either dose) were tolerant to ischemic reperfusion injury as evidenced by improved postischemic ventricular recovery [coronary flow (ml/min) 19.1 +/- 0.8 (300 microg/kg MLA), 22.6 +/- 1.0 (450 microg/kg MLA) vs. 15.9 +/- 0.7 (control); aortic flow (ml/min) 20.7 +/- 1.8 (300 microg/kg MLA), 25.8 +/- 1.4 (450 microg/kg MLA) vs. 11. 0 +/- 0.8 (control); left ventricular developed pressure (kPa) 13.3 +/- 0.6 (300 microg/kg MLA), 14.6 +/- 0.2 (450 microg/kg MLA) vs. 10. 3 +/- 0.7 (control)]. Incidences of ventricular fibrillation and ventricular tachycardia were decreased compared with the control group only in the 450 microg/kg dose of MLA-treated hearts (92% to 33%). Pretreatment of the hearts with L-NAME inhibited the preconditioning effect of MLA. To examine the induction of the iNOS expression, RNAs were extracted from the control and MLA-treated hearts (after 2, 4,6, 8, 12 and 24 hr of treatment) and Northern blot analyses were performed with a specific cDNA probe for iNOS. A single band of approximately 4.6 kb corresponding to iNOS mRNA was detected after 4 hr of MLA treatment, whereas the maximal iNOS expression was found between 6 and 8 hr of MLA treatment. The results of this study demonstrated that MLA induced the expression of iNOS and protected the myocardium from ischemic reperfusion injury which is blocked by an inhibitor of NO synthesis, which suggests a role of NO in MLA-mediated cardioprotection.     

Fastigial stimulation increases ischemic blood flow and reduces brain damage after focal ischemia

Electrical stimulation of the cerebellar fastigial nucleus (FN) increases CBF and reduces brain damage after focal ischemia. We studied whether FN stimulation "protects" the brain from ischemic damage by increasing blood flow to the ischemic territory. Sprague-Dawley rats were anesthetized (halothane 1-3%) and artificially ventilated through a tracheal cannula inserted transorally. CBF was monitored by a laser-Doppler probe placed over the convexity at a site corresponding to the area spared from infarction by FN stimulation. Arterial pressure (AP), blood gases, and body temperature were controlled, and the electroencephalogram (EEG) was monitored. The stem of the middle cerebral artery (MCA) was occluded. After occlusion, the FN was stimulated for 60 min (100 microA; 50 Hz; 1 s on-1 s off) while AP was maintained at 97 +/- 11 mm Hg (mean +/- SD) by controlled hemorrhage. Rats were then allowed to recover, and infarct volume was determined 24 h later in thionin-stained sections. In unstimulated rats (n = 7), proximal MCA occlusion reduced CBF and the amplitude of the EEG. One day later, these rats had infarcts involving neocortex and striatum. FN stimulation after MCA occlusion (n = 12) enhanced CBF and EEG recovery [61 +/- 34 and 73 +/- 43%, respectively at 60 min; p < 0.05 vs. unstimulated group; analysis of variance (ANOVA)] and reduced the volume of the cortical infarct by 48% (p < 0.05). In contrast, hypercapnia (PCO2 = 64 +/- 4; n = 7) did not affect CBF and EEG recovery or infarct volume (p > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Myocardial blood flow and coronary flow reserve late after anatomical correction of transposition of the great arteries

OBJECTIVES: Myocardial blood flow (MBF) in children late after arterial switch operation (ASO) was investigated quantitatively by positron emission tomography (PET). BACKGROUND: In children with transposition of the great arteries (TGA), ASO is widely accepted as the management of choice. The long-term patency of coronary arteries after surgical transfer to the neo-aorta, however, remains a concern. METHODS: Twenty-two normally developed, symptom-free children were investigated by PET with nitrogen-13 ammonia at rest and during adenosine vasodilation 10+/-1 years after ASO. A subgroup of 15 children (9+/-1 years; group A) had simple TGA and underwent ASO within 20 days after birth while 7 (13+/-3 years; group B) had complex TGA and underwent ASO and correction of associated anomalies later after birth. Ten young, healthy adults (26+/-6 years) served as the control group. RESULTS: Resting MBF was not different between groups. After correction for the rate-pressure product as an index of cardiac work, younger children of group A had significantly higher MBF at rest compared to healthy adults (102+/-29 vs. 77+/-6 ml/100 g/min; p = 0.012) while flow in group B was not different from the other groups (85+/-22 ml/100 g/min; p = NS). Hyperemic blood flows were significantly lower in both groups after ASO compared to normals (290+/-42 ml/100 g/min for group A, 240+/-28 for group B, 340+/-57 for normals; p < 0.01); thus, coronary flow reserve was significantly lower in both groups after ASO compared to healthy adults (3.0+/-0.6 for group A, 2.9+/-0.6 for group B, 4.6+/-0.9 for normals; p < 0.01). CONCLUSIONS: Blood flow measurements suggest decreased coronary reserve in the absence of ischemic symptoms in children late after arterial switch repair of TGA. The global impairment of stress flow dynamics may indicate altered vasoreactivity; however, the prognostic significance of these findings needs to be determined.     

The rate zonal separation of organelles from dilute suspensions: the problem of a large sample volume

We previously showed that preoperative nicorandil, a hybrid potassium channel opener and nitrate compound, conferred cardioprotective effects in a hypoxia/reoxygenation model of isolated human atrial muscle by using functional recovery as an end point, and that ischaemic preconditioning surprisingly abolished the protection afforded by nicorandil. In view of this paradoxic result, this study was undertaken to assess whether ischaemic preconditioning influences any protective effect of nicorandil by using infarct size as an end point. In addition, we investigated the underlying mechanisms of the protective action of nicorandil. Rabbits underwent a midline sternotomy under anaesthesia. A left coronary branch was occluded for 30 min followed by 120 min of reperfusion. Nicorandil (100 microg/kg bolus + 10 microg/kg/min) was given intravenously 30 min before coronary occlusion and continued to the time of reperfusion (early treatment) or 5 min before reperfusion and continued throughout reperfusion (late treatment). Ischaemic preconditioning was achieved by a single episode of 5-min coronary occlusion followed by 10-min reperfusion before the 30-minute occlusion in the presence or absence of nicorandil. Risk volume and infarct volume were determined by fluorescent microspheres and tetrazolium staining, respectively. Early treatment with nicorandil conferred a significant decrease in percentage of infarct size within the risk zone (24.9 +/- 2.9%) when compared with control (39.2 +/- 4.3%; p < 0.01). Late treatment with nicorandil had no effect on infarct size (43.5 +/- 3.4%). Ischaemic preconditioning also resulted in significant reduction in infarct size (13.4 +/- 4.3%; p < 0.01 vs. control). The combination of ischaemic preconditioning with nicorandil (early treatment) showed an intermediate protective efficacy between early treatment with nicorandil alone and ischaemic preconditioning alone (18.1 +/- 4.2%; p < 0.01 vs. control). Nitroglycerin (10 microg/kg bolus + 1 microg/kg/kg/min, i.v.) given before and during ischaemia tended to reduce infarct size, but the effect was not statistically significant (28.9 +/- 2.9%; p > 0.05 vs. control). Although an adenosine triphosphate (ATP)-sensitive potassium channel blocker, 5-hydroxydecanoate (5 mg/kg, i.v.) by itself had no effect on infarct size (38.8 +/- 3.6%), the protective effect of nicorandil was abolished by 5-hydroxydecanoate (37.7 +/- 5.8%; p < 0.05 vs. early treatment of nicorandil). There were no differences in area at risk or haemodynamics between groups. Our results show that nicorandil has a protective effect against myocardial infarction in our rabbit model when infused before and during ischaemia, but not during reperfusion, and the protective effect is abolished by an ATP-sensitive potassium channel blocker. Furthermore, the addition of ischaemic preconditioning does not detrimentally influence the effect of nicorandil. This suggests that nicorandil can confer an infarct-limiting effect by opening of ATP-sensitive potassium channels with or without intermittent ischaemia, as may happen in patients with unstable angina.     

The effect of CY1503, a sialyl Lewisx analog blocker of the selectin adhesion molecules, on infarct size and "no-reflow" in the rabbit model of acute myocardial infarction/reperfusion

CY1503, an analogue of sialyl-Lewisx, is an inhibitor of the selectin adhesion molecules. CY1503 has been found to limit myocardial infarct size in canine and feline models. However, the effect of CY1503 on the "no-reflow" phenomenon is still unknown. Anesthetised rabbits were subjected to 30 min of coronary artery occlusion and 4 h of reperfusion. Protocol 1: after 27 min of ischemia, rabbits were randomised to an iv bolus of either CY1503 (30 mg/kg) (n=9) or saline (n=9). Protocol 2: rabbits were randomly given two iv boluses of CY1503 (30 mg/kg) (n=6) or saline (n=6), administered after 10 and 25 min of ischemia. Protocol 3: after 27 min of ischemia rabbits were randomly given an iv bolus of CY1503 (30 mg/kg) (n=6) and infusion of 20 mg/kg over 4 h or saline bolus+infusion (n=6). Regional myocardial blood flow (RMBF) was assessed after 30 min and 4 h of reperfusion. The risk zone (RZ) was assessed by blue dye and the necrotic zone (NZ) by tetrazolium staining. RMBF: protocol 1: RMBF in the RZ was 2.19+/-0.33 v 2. 34+/-0.34 ml/g/min in CY1503 and controls at 30 min (P=0.75), and 0. 43+/-0.07 v 0.41+/-0.08 at 4 h of reperfusion (P=0.85). The corresponding results for protocol 2 were 1.77+/-0.29 v 1.53+/-0.34 at 30 min (P=0.61) and 0.53+/-0.16 v 0.91+/-0.55 at 4 h (P=0.53). RMBF in RZ in protocol 3 were 1.52+/-0.25 v 1.32+/-0.20 at 30 min (P=0.56) and 0.30+/-0.05 v 0.29+/-0.09 (P=0.90) after 4 h of reperfusion. The RZ was similar in both groups in all protocols. The NZ/RZ ratio was comparable in the CY1503 and control group in all three protocols (0.32+/-0.04 v 0.37+/-0.06, 0.37+/-0.08 v 0.33+/-0. 07, and 0.51+/-0.05 v 0.38+/-0.05 in protocols 1, 2, and 3, respectively). CY1503 did not limit infarct size or prevent the "no-reflow" phenomenon in the rabbit.     

Effects of Carolina rinse and adenosine rinse on microvascular perfusion and intrahepatic leukocyte-endothelium interaction after liver transplantation in the rat

Flushing hepatic grafts immediately before revascularization with a specially designed rinse solution such as "Carolina rinse" has been reported to improve survival after liver transplantation in the rat. This study investigated the influence of Carolina rinse and adenosine rinse on early graft function, microcirculation, and leukocyte (WBC)-endothelial cell interaction of arterialized syngeneic orthotopic liver transplants in Lewis rats. Livers were preserved for 24 hr in University of Wisconsin solution and flushed immediately before reperfusion with either Ringer's lactate (group A: n = 7), Ringer's lactate + 0.2 mmol/liter adenosine (group B: n = 6), or Carolina rinse (group C: n = 7). Microvascular perfusion and WBC accumulation were assessed by intravital fluorescence microscopy. In group C, acinar perfusion was significantly improved, accompanied by a lower percentage of nonperfused sinusoids 1 hr after reperfusion (mean +/- SEM: 26 +/- 2% [group A], 21 +/- 2% [B], 11 +/- 1% [C], P < 0.01 for C vs. A or B). In addition, Carolina rinse and, to a lesser extent, adenosine rinse reduced the number of WBC sticking in sinusoids and postsinusoidal venules. Better graft function in group C was indicated by increased bile flow during the observation period of 90 min after reperfusion (0.5 +/- 0.3 ml/100 g liver [group A], 1.5 +/- 0.7 [B], 3.7 +/- 0.6 [C], P < 0.01 for C vs. A or B). We conclude that Carolina rinse is able to improve early excretory hepatocellular function, microvascular perfusion, and intrahepatic WBC accumulation after prolonged cold ischemia and reperfusion, but adenosine is unlikely to be the key component of this rinse solution.     

Vasoreactive effect of acetazolamide as a function of time with sequential PET 15O-water measurement

The accurate assessment of vascular flow reserve is crucial for the evaluation of risk among patients with cerebrovascular disease. In six patients with unilateral occlusion of the internal carotid artery and one patient with unilateral occlusion of the middle cerebral artery (mean +/- S.D. age = 68 +/- 3 years), we measured cerebral blood flow (CBF) after the administration of 940 MBq 15O-water using a remotely controlled power injector. Studies were performed at rest, after 10 min, and then 10, 20 and 30 min after the administration of 1 mg acetazolamide to evaluate the vasoreactive effect, as reflected by an increase in CBF. Sixteen regions of interest (ROIs) were drawn over the CBF images. These ROIs were as follows in each hemisphere: Area I, four areas in the cortical middle cerebral arterial territory (superior frontal, frontal, temporal and parietal areas); Area II, four areas of the deep middle cerebral and vertebral arterial territory (occipital area, basal ganglia, thalamus and cerebellum). Taking normalized resting CBF to be 100%, the mean CBF measured 10, 20 and 30 min post-injection using sequential positron emission tomography was as follows: Area I, 141.4 +/- 16.3, 127.7 +/- 15.3 and 128.2 +/- 17.4% for non-occluded sites and 116.3 +/- 22.8, 112.7 +/- 16.4 and 114.9 +/- 17.1% for occluded sites; Area II, 143.4 +/- 14.5, 126.2 +/- 10.4 and 125.0 +/- 12.9% for non-occluded sites and 141.9 +/- 28.9, 126.0 +/- 20.5 and 124.1 +/- 17.1% for occluded sites. A significant difference in mean CBF was noted between the non-occluded and occluded sites in Area I, the most marked difference of 25.1% being observed 10 min after the administration of the acetazolamide. We conclude that for an accurate assessment of vascular reserve in patients with cerebrovascular disease, CBF should be measured 10 min post-administration of the acetazolamide.     

Influence of an early adrenergic blockade on thrombotic infarct size and myocardial metabolism

To evaluate the extent to which the protective effect of metoprolol was accompanied by changes in myocardial oxygen consumption and metabolism, thrombotic occlusion of coronary artery followed by infusion of metoprolol or placebo was performed in twenty four German Shepherds. To restore a coronary blood flow rt-PA was administered. Plasma levels of oxygen, glucose, lactic acid, non esterified fatty acids, triacylglyceride and adenosine breakdown products were measured before and at the end of the occlusion and in the early and late reperfusion periods. Regional myocardial blood flow was measured by means of radioactive tracer microspheres. Infarct size was estimated after perfusion and staining of excised hearts with Evans blue. Plasma levels of metoprolol were determinated before the end of occlusion and during reperfusion and therapeutic concentrations were confirmed. The infarct size was smaller in dogs receiving metoprolol (21.6 +/- 20.7 vs 43.0 +/- 17.3% p. < 0.02). Coronary collateral blood flow was greater in metoprolol than in placebo dogs (18.68 +/- 7.58 vs 11.05 +/- 6.10 ml/min/100g, p. < 0.01). As a consequence of myocardial ischemia a shift toward carbohydrate utilization, the myocardial lactate release and the accompanying symptoms of diminished myocardial lipid uptake were observed. A washout of adenosine degradation products during early reperfusion was also noticed. In beta 1 blocked animals the reduction of myocardial oxygen consumption and preserved myocardial uptake of lactate and non esterified fatty acids were documented.     

Structural and functional alterations of the intramyocardial coronary arterioles in patients with arterial hypertension

BACKGROUND: In hypertensive patients with angina pectoris, the coronary vasodilator reserve is frequently impaired despite a normal coronary angiogram. Experimental data indicate that structural alterations of the intramyocardial coronary vasculature contribute to an increased minimal coronary resistance and a diminished coronary flow reserve. METHODS AND RESULTS: In 14 patients (10 men and 4 women) with arterial hypertension and 8 normotensive subjects, minimal coronary resistance and vasodilator reserve (dipyridamole: 0.5 mg/kg body wt, gas chromatographic argon method) were determined after the angiographic exclusion of relevant coronary artery disease. Coronary reserve was depressed in hypertensive patients (2.7 +/- 2.3 vs 4.6 +/- 1.3, P < or = .05) due to increased minimal coronary resistance (0.64 +/- 30 vs 0.24 +/- 0.055 mm Hg.min.100 g.mL-1, p < or = 0.002). In right septal biopsies, mean external arteriolar diameter (21.6 +/- 2.3 vs 17.2 +/- 2.5 microns, P < or = .001), mean arteriolar wall area (271 +/- 61 vs 172 +/- 62 microns 2, P < or = .01), percent medial wall area (69.9 +/- 4.0 vs 66.0 +/- 3.2%W, P < or = .05), mean periarteriolar fibrosis area (216 +/- 122 vs 104 +/- 68 microns 2, P < or = .05), and volume density of total interstitial fibrosis (3.6 +/- 1.8 vs 1.9 +/- 0.5Vv% fibrosis, P < or = .05) were increased in hypertensive patients compared with normotensive subjects. Minimal coronary resistance correlated with %W (r = .6, P < or = .003) and Vv% fibrosis (r = .62, P < or = .002). Left ventricular mass index (111 +/- 21 vs 97 +/- 17 g/m2, P = NS) and left ventricular end-diastolic pressure (12 +/- 6 vs 8 +/- 3 mm Hg, P = NS) did not correlate significantly with minimal coronary resistance. In multivariate analysis, both %W and Vv% fibrosis explained half of the variability of minimal coronary resistance (r2 = .5, P < or = .002). CONCLUSIONS: Structural remodeling of the intramyocardial coronary arterioles and the accumulation of fibrillar collagen are decisive factors for a reduced coronary dilatory capacity in patients with arterial hypertension and angina pectoris in the absence of relevant coronary artery stenoses.     

Dietary and non-dietary factors associated with iron status in a cohort of Danish adults followed for six years

PURPOSE: Suboptimal distal coronary flow reserve after successful balloon angioplasty has been attributed to angiographically unrecognized inadequate lumen expansion, and adjunct coronary stenting has been shown to improve coronary flow reserve. The aim of this study was to investigate whether myocardial fractional flow reserve (FFRmyo) would increase further after coronary stenting compared with balloon angioplasty alone in the same patient group. METHODS: FFRmyo and quantitative coronary angiography were obtained before and after pre-stent balloon dilation, and again after stent placement in 11 patients (7 left anterior descending artery, 3 right coronary artery and 1 left circumflex artery). FFRmyo was calculated as the ratio of Pd/Pa during intracoronary adenosine 5'-triphosphate (50 micrograms and 20 micrograms in the left and right coronary arteries, respectively)-induced maximum hyperemia, where Pd represents mean distal coronary pressure measured by a 2.1 Fr infusion catheter and Pa represents mean aortic pressure measured by the guiding catheter. RESULTS: Percent diameter stenosis significantly decreased after balloon angioplasty (74% +/- 15% vs 37% +/- 17%, p < 0.001), and decreased further after stent placement (18% +/- 10%, p < 0.001 vs baseline and balloon angioplasty). FFRmyo after coronary stenting (0.85 +/- 0.09) was significantly higher than that at baseline (0.51 +/- 0.16, p < 0.001) and after balloon angioplasty (0.77 +/- 0.11, p < 0.05). There was a significant correlation between angiographic variables and FFRmyo. The increase in lumen dimensions after coronary stenting was followed by a further significant improvement of FFRmyo. CONCLUSION: These results suggest that coronary stenting may provide a more favorable functional status and lumen geometry of residual coronary stenosis compared with balloon angioplasty alone.     

Alterations of the architecture of subendocardial arterioles in patients with hypertrophic cardiomyopathy and impaired coronary vasodilator reserve: a possible cause for myocardial ischemia

OBJECTIVES: The study was designed to investigate the architecture of subendocardial arterioles of patients with hypertrophic cardiomyopathy (HCM) and angina pectoris with respect to coronary vasodilator reserve. BACKGROUND: There is growing evidence that the coronary microvasculature is abnormal in HCM. Arterioles, which mainly regulate intramyocardial blood flow, are especially suspect. METHODS: Thirteen patients with HCM (50.1+/-12.6 years old, mean value +/- SD) were studied after exclusion of any relevant coronary stenoses. Subendocardial arterioles (density [n/mm2], wall area [microm2], percent lumen area [%lumen], periarteriolar collagen area [microm2]), myocyte diameter (microm) and interstitial collagen fraction (Vv%) were evaluated by means of stereologic morphometry of transvenous biopsy samples. Coronary blood flow was measured quantitatively with the inert chromatographic argon method at basal conditions and after dipyridamole (0.5 mg/kg body weight over 4 min intravenously), and coronary vasodilator reserve was calculated as the ratio of coronary resistance at basal conditions and after pharmacologic vasodilation. Data from five normotensive subjects (45.4+/-11 years old, p = NS) served as control data. RESULTS: Arteriolar density was diminished by 38% (p = 0.004) and %lumen by 13% (p = 0.009) in patients with HCM compared with control subjects. Coronary reserve was impaired in patients with HCM (2.28+/-0.6 vs. 5.34+/-1.49, p = 0.003) because of higher coronary resistance after vasodilation (0.48+/-0.14 vs. 0.22+/-0.06 mm Hg x min x 100 g/ml, p = 0.004). Coronary vasodilator reserve correlated with arteriolar density (r = +0.47, p = 0.045) and with %lumen (r = 0.65, p = 0.003). CONCLUSIONS: In HCM, the architecture of preterminal subendocardial arterioles is altered by a reduced total cross-sectional lumen area, corresponding to an impaired coronary vasodilator capacity that may predispose to myocardial ischemia.     

Mirror, mirror on the wall, who''s the thinnest one of all? Effects of self-awareness on consumption of full-fat, reduced-fat, and no-fat products

The aim of this study was to determine whether adenosine receptor blockade before ischemia would enhance the degree of stunning and induce a sustained decrease in glucose uptake after reperfusion. METHODS: Stunning was induced in 14 anesthetized swine by partially occluding the left anterior descending artery (LAD) for 20 min (> 80% flow reduction). Seven animals were pretreated with the nonspecific adenosine receptor blocker 8-phenyltheophylline (8-PT; 5 mg/kg), which decreased reactive hyperemia by an average of 38%. Myocardial glucose uptake was assessed 1 hr following reperfusion with PET and the glucose analog 18F-fluorodeoxyglucose (FDG). RESULTS: Before ischemia, systolic shortening in the LAD region was 15% +/- 6% in the control group and 16% +/- 4% in the 8-PT group and in both groups was reduced to - 1% +/- 2% during ischemia. After reperfusion, systolic shortening was 7% +/- 3% in the control group and 2% +/- 3% in the 8-PT group (p < 0.05). Myocardial oxygen consumption before ischemia was 4.58 +/- 3.03 micromol/min/g in the control group and 4.44 +/- 1.83 micromol/min/g in the 8-PT group (ns) and neither were different after reperfusion. In the postischemic LAD region, myocardial glucose uptake was 0.18 +/- 0.15 micromol/min/g in the control group and was similar to that of the 8-PT group (0.17 +/- 0.08 micromol/min/g; ns). CONCLUSION: The nonspecific adenosine blocker 8-PT enhanced the degree of stunning when given before ischemia but did not induce a sustained effect on myocardial glucose uptake after reperfusion.     

Normal coronary flow reserve in patients with mitral valve prolapse, a positive exercise test and normal coronary arteries

We studied 12 patients (eight females and four males), ages 30-46 years, with echocardiographically documented mitral valve prolapse and clinical suspicion of coronary artery disease, based on a history of chest pain (five patients), angina-like pain (three patients), a positive exercise stress electrocardiogram (12 patients) and a focally positive thallium-201 stress perfusion scan (three patients), who were referred for cardiac catheterization and found to have normal coronary arteries. Ten patients without evidence of heart disease served as controls. In all mitral valve prolapse patients, coronary flow velocity reserve was determined successively in the left anterior descending, left circumflex and right coronary arteries as the ratio of the maximum (after intracoronary papaverine) to the resting mean coronary flow velocity. Coronary flow reserve values were fairly similar in the mitral valve prolapse and control patients; all 12 mitral valve prolapse patients had normal coronary flow reserve ( > or = 3.5) in all three coronary arteries with no significant differences among the arteries tested. Mean values +/- 1 standard deviation of the coronary flow reserve (mitral valve prolapse vs control patients) were 4.7 +/- 0.5 vs 4.6 +/- 0.6 for the left anterior descending, 4.6 +/- 0.4 vs 4.6 +/- 0.3 for the left circumflex and 4.5 +/- 0.4 vs 4.4 +/- 0.5 for the right coronary artery (all P = non-significant). The subsets of mitral valve prolapse patients with different clinical "ischaemic' manifestations were similar in terms of the calculated coronary flow reserve in all three major epicardial coronary arteries. In conclusion, this study demonstrated that an inadequate regional coronary flow reserve does not account for the clinical manifestations of myocardial ischaemia and positive exercise tests in patients with mitral valve prolapse and normal coronary arteries.