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In this study we have determined the ability of IGF-1 to protect cardiac fibroblasts against osmotic-induced apoptosis and investigated the potential mechanism(s) underlying this protection. Treatment with IGF-1 (1-100 ng/ml) promoted a dose dependent increase in cell survival against osmotic cell death. Both Akt and ERK1/2 were rapidly phosphorylated by IGF-1 and blocked by wortmannin and PD98059, inhibitors of their upstream activators respectively. However, IGF-1-induced protection was mediated via a wortmannin-dependent but PD98059-independent pathway as determined by cell survival assay suggesting a role of PI3-K/Akt. Furthermore, IGF-1 appeared to reduce the activation of a number of early components in the apoptotic pathway in a wortmannin dependent manner including the osmotic stress-induced perturbation in mitochondrial membrane potential, cleavage and activation of caspase-3 and DNA fragmentation. Thus, the results suggest that IGF-1 regulates osmotic stress-induced apoptosis via the activation of the PI3-K/Akt pathway at a point upstream of the mitochondria and caspase-3., (Copyright 2000 Academic Press.)

Over the last 50 years, studies investigating the pathogenesis of left ventricular dysfunction have resulted in many potential therapeutic targets being identified and novel classes of drugs designed to treat this condition. Despite this, the long-term prognosis of patients with clinical heart failure remains poor with mortality rates equivalent to many terminal malignancies. This article reviews our present understanding of the pathophysiology of post-infarction left ventricular dysfunction and provides a rationale for current drug usage, drugs undergoing clinical trials and compounds still under pre-clinical development. In addition, the complexities involved in deciphering intra-cellular signalling pathways mediating ventricular hypertrophy which may form the basis of future treatments are also discussed.

The postinfarction period is one of intense dynamic activity because the cardiovascular system undergoes a number of adaptive responses attempting to maintain cardiac output. These homeostatic responses contribute to the processes involved in postinfarction ventricular remodeling and involve acute, chronic, systemic, and local reactions. Almost immediately, neurohormones are activated that alter hemodynamic load, and, later, stimulate myocyte hypertrophy, while locally, inflammatory processes clear necrotic debris, reorganize the extracellular matrix, and orchestrate scar formation. Where the initial cardiac insult is sufficiently large (eg, necrosis of more than 40% of left ventricular mass), remodeling responses are exaggerated and may become maladaptive, contributing to the poor long-term prognosis associated with myocardial infarction. Although several studies have shown clear benefits after neurohormonal modulation and/or manipulation of ventricular loading forces in the postinfarction setting, relatively few studies have investigated the potential merits of a patent infarct-related artery during postinfarction ventricular remodeling. In particular, the salutary effects of late revascularization of previously occluded vessels remains controversial. Thus, though this issue remains speculative, our present practice must be governed by circumstantial evidence and hypothetical arguments. This article discusses the potential mechanisms whereby late reperfusion of an infarcted myocardial region may benefit long-term prognosis.

In the present study we have investigated whether Akt was activated during simulated ischemia (SI) and simulated ischemia/reperfusion (SI/R) in neonatal rat cardiomyocytes. Akt was phosphorylated on both S473 and T308 residues after 10 min of simulated SI/R and remained elevated for 60 min before returning to basal levels after 2 h. No phosphorylation was observed during SI alone. SI/R-stimulated Akt activation was inhibited by the phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin, the tyrosine kinase inhibitor genistein and the Src tyrosine kinase inhibitor PP2, indicating a requirement for tyrosine kinase activity in Akt activation. Furthermore, SB203580, a p38 MAPK inhibitor, partially inhibited Akt activation. SI/R also induced the phosphorylation of PHAS-I, a downstream Akt target, in a wortmannin-dependent manner. These results demonstrate for the first time that SI/R stimulates Akt activation via PI3-K-and Src tyrosine kinase-dependent pathways, whereas p38 MAPK appears to be involved in maintaining Akt activation., (Copyright 2000 Academic Press.)

We show here that exposure of cardiac cells to simulated ischemia results in apoptosis and is accompanied by phosphorylation and increased expression and transcriptional activity of STAT-1. Similarly, interferon-gamma, which is known to induce STAT-1 activation, also induced apoptosis in cardiac cells. STAT-1-transfected cells were more susceptible to ischemia-induced cell death than cells transfected with a control plasmid lacking the STAT-1 coding sequence. Furthermore, an antisense STAT-1 vector reduced both ischemia- and overexpressed STAT-1-induced cell death in cardiac cells. Both STAT-1 overexpression and interferon-gamma treatment or exposure to ischemia activated the promoter of the pro-apoptotic caspase-1 gene in cardiomyocytes. Finally, ischemia/reperfusion also induced STAT-1 activation and caspase-1 processing in ventricular myocytes in the intact heart ex vivo. Immunofluorescent staining demonstrated an increase in STAT-1-positive staining in cardiomyocytes in response to ischemia/reperfusion that co-localized with terminal deoxynucleotidyl transferase dVTP nick end-labeling-positive apoptotic cells. These results suggest that STAT-1 plays a critical role in the regulation of ischemia/reperfusion-induced apoptosis in cardiac cells, acting at least in part via a caspase-1 activation-dependent pathway.

The aim of this study was to investigate the role of nitric oxide (NO) in a cellular model of early preconditioning (PC) in cultured neonatal rat ventricular myocytes. Cardiomyocytes "preconditioned" with 90 min of stimulated ischemia (SI) followed by 30 min reoxygenation in normal culture conditions were protected against subsequent 6 h of SI. PC was blocked by N(G)-monomethyl-L-arginine monoacetate but not by dexamethasone pretreatment. Inducible nitric oxide synthase (NOS) protein expression was not detected during PC ischemia. Pretreatment (90 min) with the NO donor S-nitroso-N-acetyl-L,L-penicillamine (SNAP) mimicked PC, resulting in significant protection. SNAP-triggered protection was completely abolished by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) but was unaffected by chelerythrine or the presence of glibenclamide and 5-hydroxydecanoate. With the use of RIA, SNAP treatment increased cGMP levels, which were blocked by ODQ. Hence, NO is implicated as a trigger in this model of early PC via activation of a constitutive NOS isoform. After exposure to SNAP, the mechanism of cardioprotection is cGMP dependent but independent of protein kinase C or ATP-sensitive K(+) channels. This differs from the proposed mechanism of NO-induced cardioprotection in late PC.

Simulated ischaemia causes both necrotic and apoptotic death of primary cultures of neonatal rat cardiac myocytes. Simulated ischaemia is associated with increased expression of urocortin mRNA and with the release of urocortin peptide into the medium. Exogenous urocortin is more potent than corticotropin releasing hormone (CRH) in protecting cardiac myocytes from necrotic and apoptotic death induced by ischaemia, and the cardioprotective effects of ischaemia-preconditioned media are abrogated by antagonists to the CRH family of peptides. Simulated ischaemia increases cardiac myocyte expression of CCAAT enhancer binding (C/EBP) transcription factors, and of the p65 subunit of NFkappaB, and reporter activity of a construct incorporating a fragment of the urocortin promoter containing a C/EBP consensus site is also enhanced by simulated ischaemia. The data suggest that ischaemia, acting partly through increased expression of C/EBP transactivators, increases expression of urocortin mRNA, which is rapidly translated to the mature form. The mature peptide is rapidly released, and exerts autocrine/paracrine protective effects through the cardiac CRH-R2 receptor which preferentially binds urocortin.

The signalling mechanisms involved in the induction of nitric oxide synthase and l-arginine transport were investigated in bacterial lipopolysaccharide (LPS)- and interferon-gamma (IFN-gamma)-stimulated rat cultured aortic smooth muscle cells (RASMCs). The expression profile of transcripts for cationic amino acid transporters (CATs) and their regulation by LPS and IFN-gamma were also examined. Control RASMCs expressed mRNA for CAT-1, CAT-2A and CAT-2B. Levels of all three transcripts were significantly elevated in activated cells. Stimulated CAT mRNA expression and l-arginine transport occurred independently of protein kinase C (PKC), protein tyrosine kinase (PTK) and p44/42 mitogen-activated kinases (MAPKs), but were inhibited by the p38 MAPK inhibitor SB203580, which at 3 microM caused maximum inhibition of both responses. Induction of NO synthesis was independent of p44/42 MAPK activation and only marginally dependent on PKC, but was attenuated markedly by the PTK inhibitors genistein and herbimycin A. SB203580 differentially regulated inducible NO synthase expression and NO production, potentiating both processes at low micromolar concentrations and inhibiting at concentrations of >/=1 microM. In conclusion, our results suggest that RASMCs constitutively express transcripts for CAT-1, CAT-2A and CAT-2B, and that expression of these transcripts is significantly enhanced by LPS and IFN-gamma. Moreover, stimulation of l-arginine transport and induction of NO synthesis by LPS and IFN-gamma appear to be under critical regulation by the p38 MAPK, since both processes were significantly modified by SB203580 at concentrations so far shown to have no effect on other signalling pathways. Thus, in RASMCs, the p38 MAPK cascade represents an important signalling mechanism, regulating both enhanced l-arginine transport and induced NO synthesis.

Over expression of heat shock proteins (hsps) by transfection of plasmid constructs in vitro and in transgenic animals in vivo can protect primary cardiac cells from subsequent exposure to severe thermal or hypoxic stress. Here we show that such protection can also be achieved by over-expressing the hsps using herpes simplex virus (HSV) vectors capable of efficient gene delivery in vivo. Moreover, the convenience and high efficiency of this system has allowed us to show, for the first time, that over-expression of hsp27 or hsp70 can protect cardiac cells against three different apoptosis-inducing stimuli as well as against thermal or hypoxic stress whereas hsp56 has no protective effect. The potential therapeutic use of inducing the over-expression of specific hsps in cardiac cells in vivo using pharmacological or gene therapy procedures is discussed.

The role of protein kinase C (PKC) in ischemic preconditioning remains controversial because of difficulties with both its measurement and pharmacological manipulation. We investigated preconditioning in isolated neonatal rat cardiocytes by expressing constitutively active isotypes of PKC. Observations at differing durations of simulated ischemia suggested beta-galactosidase (beta-gal) activity reflected viability within transfected myocytes. Preconditioning with 90 min of ischemia significantly increased beta-gal activity and myocyte survival after 6 h of ischemia; an effect abolished by PKC inhibitors. After co-transfection with plasmids encoding beta-gal and either constitutively active mutants of PKC-delta, PKC-alpha, wild type PKC-delta, or empty vector, cardiocytes were subjected to 6 h of ischemia. Only PKC-delta, rendered constitutively active by a limited deletion within the pseudosubstrate domain, consistently increased resistance to simulated ischemia (beta-gal activity was 85.6 +/- 11.9% versus 53.7 +/- 6.5% (p

Myocardial preconditioning describes the profound myocardial protection that follows a short episode of sublethal ischaemia. Adenosine is produced in ischaemic myocardium and is thought to be an important trigger of the protective mechanism. The exact pathway awaits full elucidation but activation of G proteins and subsequently protein kinase C appear to be important signals. End effectors responsible for delaying cell death include opening of K+ATP ion channels and the transcription of a family of cytoprotective proteins. Absolute proof that preconditioning occurs in man is still awaited, although cross clamping of the aorta during cardiac surgery, balloon inflation during coronary angioplasty, warm-up angina and preinfarction angina are surrogate models supporting its existence. A clearer understanding of the protective mechanisms involved could lead to the development of novel therapeutic agents that could save the infarcting myocardium.

There is substantial evidence that many patients with impaired left ventricular function secondary to coronary artery disease may have hibernating or stunned myocardium. The identification of these patients is important, as revascularisation is associated with an improvement in function, and there is some evidence that revascularisation of these patients will actually improve prognosis. The most useful investigations for the identification of reversible left ventricular dysfunction are dobutamine echocardiography, thallium scanning and, although not available in many centres, PET scanning.

Cardiotrophin-1 (CT-1) was originally identified as a molecule capable of inducing cardiac hypertrophy. We show here that treatment of cultured neonatal cardiocytes with CT-1 induces enhanced synthesis of the heat shock proteins hsp70 and hsp90, with hsp70 levels being enhanced three-fold and hsp90 levels being enhanced seven-fold. Such CT-1-treated cells are protected against subsequent exposure to severe thermal or ischaemic stress, as assayed both by measures of total cell death, such as trypan blue exclusion and LDH release, and by measures of apoptosis, such as propidium-iodide-staining and TUNEL-labelling. Hence, CT-1 can induce the protective hsps and protect cardiac cells from diverse stresses.

The myocardium is a potential target for the expression of exogenous genes to treat inherited and acquired diseases. Although adenovirus-mediated gene transfer has resulted in high-level gene transfer in vivo via direct intramyocardial injection and via a percutaneous intra-arterial route, the time-course of gene expression is limited by host immune responses. It was the aim of this study to test whether cationic liposome-mediated gene transfer, which does not suffer from the aforementioned problems, was feasible in the adult rabbit myocardium via a percutaneous transluminal approach. Doses of plasmid DNA encoding lacZ from 200-800 micrograms complexed to cationic liposomes resulted in X-gal conversion at day 3 with associated myocardial damage. We hypothesised that the damage was associated with macro-aggregates of cationic liposomes-DNA occluding the microcirculation. When such aggregates were excluded no X-gal conversion was seen in vivo. In order to show that X-gal conversion occurs in areas of infarction in the myocardium we caused closed chest infarction by deploying a platinum micro-embolisation coil in the circumflex coronary artery. At day 3 X-gal conversion was observed in the territory supplied by the occluded artery. Thus, microinfarction causes the false positive appearance of gene transfer when using a lacZ reporter gene.

Herpes simplex virus 1 (HSV1), while usually thought of as neurotrophic, can also efficiently infect a wide variety of non-neuronal cell types and so might be developed as a vector for gene delivery to non-neuronal as well as neuronal cells. Here we have tested three different disabled HSV vectors for their ability to deliver a lacZ gene to primary cardiac myocytes and vascular smooth muscle cells in vitro, and used the most efficient virus to transfect the rat heart in vivo. We also assessed the degree of cytopathic effect of the various viruses on the cardiac myocytes in vitro by testing the effects on the frequency of beating in synchronously beating myocyte cultures. While an HSV mutant in which the essential immediate-early gene IE2 had been deleted gave high efficiency gene transfer to the cardiac myocytes in vitro and the rat heart in vivo, viruses in which ICP34.5 or ICP34.5 and VMW65 were inactive (and which were also unable to replicate in these cells) gave a much lower efficiency of gene transfer, mirroring the degree of cytopathic effect observed in the beating myocyte cultures. Gene transfer to the vascular smooth muscle cells was considerably less efficient than to the myocytes in all cases. These results indicate that while HSV may be inappropriate for highly efficient gene transfer to the arterial wall, efficient gene transfer can be achieved in the myocardium, and thus that HSV vectors may be suitable for the alteration of cardiac cell physiology in vivo.

Myocardial protection and changes in gene expression follow whole body heat stress. Circumstantial evidence suggests that an inducible 70-kD heat shock protein (hsp70i), increased markedly by whole body heat stress, contributes to the protection. Transgenic mouse lines were constructed with a cytomegalovirus enhancer and beta-actin promoter driving rat hsp70i expression in heterozygote animals. Unstressed, transgene positive mice expressed higher levels of myocardial hsp70i than transgene negative mice after whole body heat stress. This high level of expression occurred without apparent detrimental effect. The hearts harvested from transgene positive mice and transgene negative littermates were Langendorff perfused and subjected to 20 min of warm (37 degrees C) zero-flow ischemia and up to 120 min of reflow while contractile recovery and creatine kinase efflux were measured. Myocardial infarction was demarcated by triphenyltetrazolium. In transgene positive compared with transgene negative hearts, the zone of infarction was reduced by 40%, contractile function at 30 min of reflow was doubled, and efflux of creatine kinase was reduced by approximately 50%. Our findings suggest for the first time that increased myocardial hsp70i expression results in protection of the heart against ischemic injury and that the antiischemic properties of hsp70i have possible therapeutic relevance.

Background: We previously reported a delayed phase of protection against infarction 24 hours after ischemic preconditioning in the rabbit. In the present study, we investigated the possibility that this "second window of protection," like the well-described early phase of protection in the rabbit, might be associated with adenosine receptor activation., Methods and Results: In the first series of experiments, we examined whether adenosine receptor blockade with 8-(p-sulfophenyl)-theophylline (SPT) during preconditioning could abolish the delayed protection against infarction 24 hours later. Open-chest rabbits were subjected to myocardial preconditioning (PC) with the four 5-minute coronary occlusions or they were sham operated on (SHAM). During these procedures, animals received either SPT (PC + SPT, n = 6; and SHAM + SPT, n = 6) or vehicle (PC + VEH, n = 12; and SHAM + VEH, n = 11). Twenty-four hours later, infarct development after a 30-minute coronary occlusion/120-minute reperfusion insult was assessed with triphenyltetrazolium staining. In vehicle-treated rabbits, the infarct-to-risk ratio (I/R) was reduced from 53.6 +/- 5.7% (SHAM + VEH) to 32.9 +/- 4.6% (PC + VEH) (P < .05), clearly indicating a delayed phase of protection. Although I/R was not significantly different between SHAM + VEH (53.6 +/- 5.7%) and SHAM + SPT (61.7 +/- 5.4%), in PC + SPT the delayed protection was abolished (I/R = 56.8 +/- 3.8%). In the second series of experiments, we examined if pharmacological adenosine A1 receptor stimulation could evoke a delayed phase of protection. Conscious rabbits were pretreated with intravenous boluses of saline or the A1 receptor-selective agonist 2-chloro-N6-cyclopentyladenosine (CCPA), and infarct size in response to 30-minute ischemia/120-minute reperfusion was assessed 24 hours later. I/R was 54.5 +/- 2.7% in saline-pretreated controls (n = 12). Pretreatment with 25 micrograms/kg CCPA (n = 6), 50 micrograms/kg CCPA (n = 6), or 100 micrograms/kg CCPA (n = 6) resulted in I/R ratios of 37.1 +/- 4.2% (P < .01), 37.7 +/- 2.2% (P < .01), and 26.3 +/- 5.7% (P < .01), respectively. In both series of experiments, there were no differences in systemic hemodynamics during the infarct protocol, assessed as rate-pressure product, between the different experimental groups., Conclusions: Twenty-four hours after repetitive brief coronary occlusions, susceptibility to infarction in rabbit myocardium is reduced, an effect that may have clinical relevance. Results of the present study suggest that this second window of protection following preconditioning may, like the early phase of protection, be initiated by an adenosine-related mechanism.

Numerous reports suggest that stress protein accumulation confers protection in various mammalian tissues against differing stresses. The purpose of this article is to review the evidence that stress proteins, in particular hsp70, are able to alter the resistance of the heart to subsequent ischaemic and non-ischaemic injury and to discuss the possible physiological basis for this apparent protection. The possible, though unlikely involvement of heat stress proteins in classical ischaemic preconditioning is addressed as is the possibility of their involvement in a delayed second window of protection.

Preconditioning has only been demonstrated in arterially perfused myocardium. Our aim was to develop a model of preconditioning in isolated, superfused, isometrically contracting rabbit right ventricular papillary muscle. This would eventually allow us to evaluate isolated human muscles. Papillary muscles were suspended in an organ bath, superfused with oxygenated Tyrode solution, and field stimulated at 1 Hz. Muscles were assigned either to control or to preconditioning groups. Preconditioning was induced with 3 min of rapid pacing (3 Hz) with substrate-free hypoxic buffer and was followed by 15 min of reoxygenation with substrate. Subsequently, both groups were exposed to 45 min of substrate-free hypoxia followed by 120 min of reoxygenation with substrate. Preconditioning protected the myocardium with better recovery of developed force (50.6 +/- 6.7 vs. 27.4 +/- 4.2% of baseline developed force, P < 0.01). This effect could be blocked by 8-(p-sulfophenyl)theophylline (SPT) given during preconditioning at a dose that did not increase hypoxic damage in controls (percent developed force compared to baseline: preconditioned muscles + SPT = 30.9 +/- 2.8% and control muscles + SPT = 27.1 +/- 2.3%). In addition, pretreatment with (-)N6(2-phenylisopropyl)adenosine similarly protected the myocardium (49.5 +/- 5.5% recovery, P < 0.01). We conclude that isolated superfused muscles can be preconditioned. This preconditioning does not depend on coronary flow and involves activation of adenosine receptors.

The aims of this study were to examine the effects of whole body heat stress and subsequent stress protein induction on glycolytic metabolism, mitochondrial metabolism, and calcium handling within the heart. The effect of heat stress on glycolytic and mitochondrial pathways was examined by measuring contractile performance in the presence of glucose and pyruvate, respectively. Calcium handling was assessed using force-interval relationships. Right ventricular papillary muscles taken from heat-stressed and control rabbit hearts were superfused with Kreb's solution containing either glucose or pyruvate and rendered hypoxic for 30 min. After reoxygenation, the greatest recovery of contractile function occurred in the heat-stressed muscles with pyruvate as substrate; there was, however, no difference in the force-interval relationship between the groups. The degree of contractile recovery was related to the content of the inducible 70-kD but not the 65-kD, heat stress protein. This study suggests that heat stress enhances the ability of rabbit papillary muscle to use pyruvate, but not glucose, after reoxygenation, and that the differences seen in contractility may be secondary to induction of the 72-kD stress protein.

Heat stress limits the injury associated with myocardial ischaemia and reperfusion, an effect previously attributed to enhanced endogenous anti-oxidant activity. We examined the influence of heat stress on the calcium paradox, an injury in which oxidant stress is not thought to play a major role. Twenty-four hours following sham or true heat stress, rabbits were re-anaesthetized and hearts either removed for stress protein analysis (n = 8), or Langendorff-perfused (n = 20) and subjected to a calcium paradox. Ten minutes following calcium repletion (Ca2+ = 1.3 mM), left ventricular developed pressure was better preserved in heat stress vs control hearts (38.3 +/- 5.0 vs 18.8 +/- 4.1 mmHg, respectively, P = 0.003) whilst contracture, measured by left ventricular end-diastolic pressure, was diminished (21.6 +/- 4.7 vs 39.9 +/- 5.2 mmHg, respectively, P = 0.02). Creatine phosphokinase release at 1 min was less in heat stress vs control hearts (10.6 +/- 8.6 vs 86.4 +/- 33.7 U/min/g, respectively, P = 0.01). The myocardial content of the 72 kDa stress protein was elevated eight-fold in heat stress vs control hearts (2.8 +/- 0.2 vs 0.4 +/- 0.1 U, respectively, P = 0.01). This study suggests that some portion of the stress protein response represents a form of cardiac adaptation capable of limiting myocyte injury independent of antioxidant mechanisms.

Background: To test the hypothesis that the heat shock response is associated with myocardial salvage, the heat stress protein (HSP) content of cardiac tissue was increased by either ischemic or thermal stress., Methods and Results: Rabbits were divided into four groups. Ischemic pretreatment (n = 15) comprised four 5-minute episodes of coronary ligation separated by 10 minutes of reperfusion. The corresponding control group (n = 21) underwent surgical preparation without coronary ligation. Thermal pretreatment (n = 16) involved whole-body temperature elevation to 42 degrees C for 15 minutes; corresponding controls (n = 15) were treated with anesthetic alone. Twenty-four hours later, hearts were removed for HSP estimation or infarct size assessment after a 30-minute coronary ligation. Myocardial HSP72 content assessed by Western blotting was elevated by both ischemic and thermal pretreatments (2.5 +/- 0.2 units, n = 4, and 2.8 +/- 0.3 units, n = 4, mean +/- SEM; P = NS, respectively) compared with the corresponding control groups (1.0 +/- 0.3, n = 4, P < or = .01 and 0.3 +/- 0.1, n = 4, P < or = .01, respectively). HSP60 was preferentially elevated by ischemic pretreatment. After a 30-minute coronary occlusion and 120 minutes of reperfusion, ischemic and thermal pretreatments limited infarct size as a percentage of the volume at risk by 28.8 +/- 5.2% vs 52.0 +/- 5.2%, P < or = .01 and 32.8 +/- 3.8% vs 56.9 +/- 6.5%, P < or = .01, respectively., Conclusions: Myocardial stress protein induced by either sublethal thermal or ischemic injury is associated with myocardial salvage. Our findings suggest that stress protein elevation, rather than the nonspecific effects of thermal or ischemic stress, may be responsible for the myocardial protection seen in this model. Our observations may have important implications regarding myocardial adaptation to brief periods of ischemia.

Objective: Heat stress, with the expression of heat stress proteins, has been shown to protect the rabbit heart in vitro against global ischaemia/reperfusion injury, though no benefit is apparent in an in vivo rabbit model of infarct size. The aim of this study was therefore to investigate this discrepancy and to discover whether heating itself has any effect which could negate the protection derived from myocardial stress protein synthesis., Methods: (1) To ascertain whether heat stress could limit infarct size in the absence of blood, isolated buffer perfused hearts, with or without prior heat stress, were subjected to 45 min of regional ischaemia and 120 min reperfusion, and the resulting infarct size was expressed as a percentage of the risk area (I/R%). (2) The observations were repeated in an isolated blood perfused heart model in which a support rabbit (heat stressed or control) was used to perfuse the isolated heart., Results: In the buffer perfused heart, prior heat stress reduced I/R from 70.8(SEM 4.4)%, n = 10, in controls to 51.5(5.7)%, n = 12 (p < 0.05). In hearts perfused by support rabbits, prior heat stress reduced I/R [from 34.7(3.7)%, n = 16, to 23.5(3.3)%, n = 15 (p < 0.05)] only when the perfusing rabbit was a control (not heat stressed). If the perfusing rabbit had been heated, I/R was greater in both heat stressed and control hearts [51.9(7.0)% and 44.9(3.3)%, p < 0.05 v control support rabbit]., Conclusions: Heat stress limits infarct size in this rabbit model. However it appears to have additional adverse effects, probably on the blood, which may override any benefit associated with myocardial stress protein synthesis.

Objective: Rapid pacing has been shown to precondition the dog heart against ischaemic dysrhythmia. The aim of this study was to determine whether rapid pacing could also limit infarct size., Methods: Rabbits (n = 5) were rapidly paced via the left atrium at 420-480 beats.min-1. Five min of rapid pacing and 10 min of recovery in sinus rhythm were followed by 45 min of regional ischaemia and 120 min of reperfusion. Control rabbits (n = 9) were treated identically without prior rapid pacing. Infarct size was determined in both groups using tetrazolium and expressed as a percentage of the area at risk demarcated by fluorescent microspheres. In a separate series of experiments, rapidly paced Langendorff perfused rabbit hearts (n = 9) were used to determine coronary flow under perfusion conditions designed to simulate the in vivo situation during rapid pacing., Results: Rapid pacing caused a fall in systolic pressure from 91.4(SEM 4.5) to 47.0(5.9) mm Hg (p < 0.01) and diastolic pressure from 67.2(2.9) to 23.6(3.2) mm Hg (p < 0.01). Both recovered within 30 s of cessation of pacing. During rapid pacing the action potential duration shortened from 192(13) to 128(5) ms (p = 0.01) and developed electrical alternans (n = 4). Following rapid pacing the ECG showed either ST depression or T wave inversion (n = 4). Despite these profound changes, rapid pacing did not reduce infarct size v control [52.7(4.6)% v 60.8(9.1)% of the area at risk, respectively]. The in vitro experiments estimated that rapid pacing would result in a reduction in coronary flow to 44% of that in sinus rhythm without a significant rise in lactate efflux., Conclusions: In our model, pretreatment with rapid pacing fails to reduce infarct size. The most likely reason for this is that rapid pacing at a rate of 480 beats.min-1 does not cause myocardial ischaemia of sufficient severity to trigger the preconditioning response.

Cells subjected to increases in temperature induce the expression of several proteins known as heat shock or stress proteins. This process enhances the cell's ability to overcome the effects of further stress. In this respect, the effects of heat stress have been reported to protect the hearts of rats following ischaemia and reperfusion. We have confirmed and extended this observation, not only using different indices of myocardial injury but also in another species, namely the rabbit. Animals were anaesthetized and the body temperature raised to 42 degrees C for a 15-min period. Controls were treated in the same way but without heating. Twenty-four hours later the rabbits were re-anaesthetized and the hearts removed for either heat stress protein analysis or perfusion with Krebs buffer using an isolated perfused heart apparatus. Hearts were subjected to 60 min of low flow (1 ml/min) ischaemia followed by 30 min of reperfusion. All hearts subjected to heat stress showed an enhanced recovery of function upon reperfusion as measured by improvements in developed pressure (27.3 +/- 3.6 vs 16.3 +/- 3.0 mmHg) and diastolic pressure (37.3 +/- 7.4 vs 54.7 +/- 3.1 mmHg). In addition, creatine kinase release, associated with reperfusion, was significantly reduced in the heat-stressed hearts (532 +/- 102 vs 1138 +/- 73 mU/min/g wet wt). Myocardial accumulation and release of oxidized glutathione, an index of oxidative stress, was significantly reduced in the heat-stressed group (0.003 +/- 0.003 vs 0.376 +/- 0.113 nmol/min/g wet wt). The improved metabolic status of the reperfused heat-stressed hearts was further demonstrated by a significant conservation in the levels of ATP (6.1 +/- 0.9 vs 2.8 +/- 0.8 mumol/g dry wt) and CP (36.9 +/- 6.4 vs 16.4 +/- 5.1 mumol/g dry wt). Finally, isolated mitochondrial function in terms of respiratory control index (RCI) was maintained in the heat-stressed hearts (9.2 +/- 0.9 vs 5.7 +/- 0.2) and overloading with calcium was reduced. These data extend the hypothesis that heat stress protects the heart following ischaemia and reperfusion in this in vitro model, in a way as yet undetermined.

Two patients with systemic embolism were studied with transoesophageal contrast echocardiography which demonstrated its probable paradoxical nature. In both cases paradoxical embolism was associated with pulmonary embolism. Precordial contrast echocardiography demonstrated a right-to-left shunt in one patient but was unable to demonstrate a shunt in the second. Transoesophageal echocardiography suggested that the shunt was across a patent foramen oval in both cases and revealed large thrombi in the pulmonary arteries in one. When precordial contrast echocardiography reveals a right-to-left shunt or when it is technically inadequate in patients suspected of having one, transoesophageal contrast echocardiography can demonstrate the nature of the shunt and is an alternative to cardiac catheterisation techniques. In addition, it can reveal large thrombi in the pulmonary arteries.

The uptake of invasive cardiological investigation and cardiopulmonary bypass procedures by the North West Surrey Health District was audited over the years 1979-88. Growth was almost continuous throughout the ten year period. The need within the district each year for coronary angiography seemed to be between 111 and 171 and for surgical revascularisation of the myocardium between 63 and 96 procedures; the first figure is the mean of the second quinquennial period (1984-88) and the second figure the total for 1988. After correction for the standardised mortality ratio and catchment area, the national requirement should lie between 690 and 1070 coronary angiograms and 390 and 600 coronary artery bypass graft operations per million population each year. There is a further national requirement for 70 valvar heart operations and 30 miscellaneous procedures per million population each year. Owing to delays in the provision of services, 20 patients died of a cardiovascular cause while they were on the waiting list for investigation or surgery. In the United Kingdom the annual target to be achieved by 1990 was 300 coronary artery bypass procedures per million population.