Precorneal retention time of ocular lubricants measured with fluorophotometry in healthy dogs.

OBJECTIVE: Determine the precorneal retention time of five different ocular lubricants commonly used in dogs. ANIMALS STUDIED: Six healthy Beagle dogs (n = 12 eyes). PROCEDURES: Five ocular lubricants were studied: Artificial Tears Solution® (1.4% polyvinyl alcohol), I-Drop® Vet Plus (0.25% hyaluronate), Optixcare® Eye Lube Plus (0.25% hyaluronate), Systane® Ultra (0.4% polyethylene glycol 400 and 0.3% propylene glycol), and Artificial Tears Ointment® (mineral oil/white petrolatum). Each lubricant was mixed with 10% sodium fluorescein to achieve 1% fluorescein formulations. Following topical administration of 35 mg in each eye, tear fluid was collected with capillary tubes at selected times (0, 1, 5, 10, 20, 30, 40, 50, 60, 90, 120, 180 min) and fluorescein concentrations were measured with a computerized scanning ocular fluorophotometer. RESULTS: Tear fluorescence was significantly greater with Artificial Tears Ointment® compared with other lubricant formulations from 1 to 20 min post-administration. Median (range) precorneal retention times were significantly different among the 5 lubricants, ranging from 40 minutes (20-90 min) for Artificial Tears Ointment®, 35 min (20-90 min) for Systane® Ultra, 30 min (10-60 min) for I-Drop® Vet Plus, 25 min (10-60 min) for Optixcare® Eye Lube Plus, and 10 min (10-20 min) for Artificial Tears Solution®. Precorneal retention time was significantly lower for Artificial Tears Solution® compared with the other 4 formulations. CONCLUSIONS: This study established normative data for the retention time of common lubricants on the ocular surface of dogs, which may be used to guide clinicians with their choice of lubricant and frequency of administration.

Lack of effect of a topical regenerative agent on re-epithelialization rate of canine spontaneous chronic corneal epithelial defects: A randomized, double-masked, placebo-controlled study.

Spontaneous chronic corneal epithelial defects (SCCEDs) are characteristic ulcers in dogs that are refractory to healing. The aim of the study was to evaluate the use of a topical regenerative agent to promote healing of SCCEDs. Nineteen dogs (20 eyes) were randomized to receive either regenerative agent (10 eyes) or placebo (10 eyes) every 48h following corneal debridement, which was repeated 1 week later if the SCCED had not yet healed. The mean±standard deviation time to re-epithelialization was 17.3±12.8 days for the group treated with a topical regenerative agent and 19.3±11.7 days for the group treated with a placebo; the cumulative healing rates were not statistically different (P>0.650). A positive association was found between the initial size of the ulcer and the time to re-epithelialization (r=0.555, P=0.011). Although well tolerated by dogs, there was no therapeutic advantage in using a topical regenerative agent for re-epithelialization of SCCEDs.

Proliferation signal inhibitors and post-transplant malignancies in heart transplantation: practical clinical management questions.

Although malignancy is a major threat to long-term survival of heart transplant (HT) recipients, clear strategies to manage immunosuppression in these patients are lacking. Several lines of evidences support the hypothesis of an anticancer effect of proliferation signal inhibitors (PSIs: mammalian target of rapamycin [mTOR] inhibitors) in HT recipients. This property may arise from PSI's ability to replace immunosuppressive therapies that promote cancer progression, such as calcineurin inhibitors or azathioprine, and/or through their direct biological actions in preventing tumor development and progression. Given the lack of randomized studies specifically exploring these issues in the transplant setting, a collaborative group reviewed current literature and personal clinical experience to reach a consensus aimed to provide practical guidance for the clinical conduct in HT recipients with malignancy, or at high risk of malignancy, with a special focus on advice relevant to potential role of PSIs.

Optimal pressure for low pressure controlled reperfusion to efficiently protect ischemic heart: an experimental study in rats.

Recent work has demonstrated the benefit of low pressure (LP) reperfusion to protect the heart undergoing an ischemic insult. The goal of the present study was to determine the optimal pressure for the application of LP reperfusion. Isolated rats hearts (n = 30) were exposed to 40 minutes of global warm ischemia followed by 70 minutes of reperfusion with a pressure fixed at 100 cm H(2)O (normal pressure [NP] = control group), 85 cm (group LP [low pressure]-85), 70 cm (group LP-70), or 55 cm (group LP-55). Cardiac function was assessed during reperfusion using the Langendorff model. Myocardial necrosis was assessed by measuring lactate dehydrogenase (LDH) and creatine kinase (CK) leakage in the coronary effluents. Functional recovery was progressively and significantly improved with decreased perfusion pressure. Rate-pressure product (RPP) averaged 3765 +/- 408, 6824 +/- 439, and 12,036 +/- 664 mm Hg/min, respectively, among the control, LP-85, and LP-70 groups (P < .001, LP-70 vs other groups). However, RPP collapsed in the LP-55 group. Similarly, necrosis as measured by LDH and CK leakage progressively reduced between LP-100 and LP-70 hearts (P < .01), with a drastic increase in enzyme in the LP-55 group. In conclusion, this study demonstrated that 70 cm H(2)O is an optimal LP to improve postischemic contractile dysfunction and attenuate necrosis during reperfusion.

Cyclosporine-related posterior reversible encephalopathy syndrome after heart transplantation: should we withdraw or reduce cyclosporine?: case reports.

Cyclosporine (CsA) related encephalopathy has not been well documented after heart transplantation. We report 2 cases of posterior reversible encephalopathy syndrome (PRES). The first case was a 68-year-old woman who underwent heart transplantation and received immunosuppression with mycophenolate mofetil, prednisone, and CsA. On day 14, she developed arterial hypertension, headache, visual disturbances, and generalized seizures. Fluid-attenuated inversion recovery magnetic resonance imaging (MRI) of the brain showed diffuse and bilateral high signals in the frontal posterior and the occipital areas. The second case was a 19-year-old man with a heart transplant receiving immunosuppression with prednisone and CsA. On day 44, he developed acute headache and generalized seizures. T2-weighted MRI of the brain showed diffuse high signals in the cerebellum, right lenticular and occipital areas. In both cases blood CsA concentration was therapeutic. Both cases recovered but in the first case neurologic findings were reversed only after CsA withdrawal.

Optimal time duration for low-pressure controlled reperfusion to efficiently protect ischemic rat heart.

Previous studies have shown the capacity of low-pressure (LP) reperfusion to protect the ischemic heart. The present study sought to determine the optimal time for the application of LP reperfusion. Isolated rat hearts (n = 30) were exposed to 40 minutes of global warm ischemia followed by 70 minutes of reperfusion. Reperfusion was performed under LP (LP = 70 cm H(2)O) for 0 (control group), 5 (group LP-5), 10 (group LP-10), 30 (group LP-30), or 60 (group LP-60) minutes. Following the LP period the hearts were reperfused with normal pressure (100 cm H(2)O) until the end of reperfusion. Cardiac function was assessed during reperfusion using the Langendorff model. Myocardial necrosis was assessed by measuring LDH leakage in the coronary effluents. Functional recovery was reduced among the control and LP-5 groups with rate-pressure products (RPP) averaging 3788 +/- 499 and 5333 +/- 892 mm Hg/min, respectively. RPP was significantly improved in other groups with RPP averaging 7363 +/- 1159, 7441 +/- 863, and 7269 +/- 692 mm Hg/min in LP-10, LP-30, and LP-60 (P < .01). Similarly, necrosis measured by LDH leakage was significantly reduced in LP-10, LP-30, and LP-60 hearts (P < .01). This study demonstrated that LP reperfusion improves postischemic contractile dysfunction and attenuates necrosis when applied for at least 10 minutes.

Identification and characterization of two genes (MIP-1beta, VE-CADHERIN) implicated in acute rejection in human heart transplantation: use of murine models in tandem with cDNA arrays.

BACKGROUND: Genes and mechanisms of action involved in human acute rejection after allogeneic heart transplantation remain to be elucidated. The use of a murine allograft model in tandem with cDNA arrays and quantitative real-time polymerase chain reaction (Q-PCR) can greatly help in identifying key genes implicated in human heart acute rejection. METHODS AND RESULTS: Hearts from Balb/c mice were either not transplanted or transplanted heterotopically in the abdomen of Balb/c (isografts) and C57BL/6 (allografts) mice. Histological analysis showed acute rejection only in allografts. Total RNA was extracted from isografts (n=3), allografts (n=4), and not transplanted hearts (n=4); reverse transcribed; and labeled with P32. Each probe was hybridized to cDNA macroarrays. Eight genes were overexpressed and 7 genes were underexpressed in allografts compared with isografts. Macrophage inflammatory protein-1beta (MIP-1beta), an overexpressed gene, and VE-cadherin, an underexpressed gene, were validated by immunohistochemistry and Q-PCR in the murine models. Genes of interest, validated in the 3 murine groups, were then investigated in human heart tissues. Immunohistochemistry and Q-PCR performed on endomyocardial biopsies after heart transplantation showing no rejection (n=10) or grade IB (n=10) or IIIA (n=10) rejection, according to International Society of Heart and Lung Transplantation criteria, confirmed the results obtained from the murine model. CONCLUSIONS: We have demonstrated that the upregulation of MIP-1beta and downregulation of VE-cadherin may strongly participate in human acute heart rejection.

Chronic renal failure and end-stage renal disease are associated with a high rate of mortality after heart transplantation.

The aim of the study was to analyze the etiology, the factors for progression of chronic renal failure to end-stage-renal disease (ESRD), and the influence of ESRD on the survival rate among a cohort of 59 heart transplant patients (HTP) referred for the management of chronic renal failure (CRF). At the time of the first nephrology consultation (6 +/- 4.25 years after cardiac transplantation) the mean creatininemia was 261.5 +/- 99 micromol/L and mean creatinine clearance (Cockcroft formula) was 32 +/- 15 mL/min. The cause of CRF were calcineurin inhibitor toxicity in 38.9% of patients, vascular events in 15.2%, hemolytic uremic syndrome in 5%, membranous glomerulopathy in 3.3%, diabetes in two patients, focal/segmental glomerulosclerosis in 3.3%, renal hypoplasia in 1.7%, and unknown in 27%. Evolution to ESRD occurred in 38.9% of patients: 17 patients started hemodialysis, three peritoneal dialysis, and two received a preemptive kidney transplantation. Creatininemia (micromol/L) at the time of nephrology referral was 229.2 +/- 72.6 versus 315.8 +/- 113.4 (P < .001) and creatinine clearance (mL/min) was 34.9 +/- 15.1 versus 27.3 +/- 13.7 (P = .049) for patients with CRF versus ESRD, respectively. Both proteinuria (g/24 hours) of 1 +/- 2.2 versus 2.3 +/- 1.8 (P = .02) and tobacco use in 35.1% versus 54.4% (P = .045) were significantly associated with progression of CRF, while age at the time of heart transplantation, cause of cardiac failure and renal failure, high blood pressure, type 2 diabetes, dyslipidemia, alcoholism, cirrhosis, and cerebral vascular accident were not. Death occurred in 18 HTP: 50% of patients with ESRD and 18.5% of patients with CRF-a 2.6 relative risk of of death in HTP patients with ESRD compared with HTP with CRF only (P < .01).

Alteration of the left ventricular contractile reserve in heart transplant patients: a dobutamine stress strain rate imaging study.

BACKGROUND: Strain rate imaging (SRI), a recently developed Doppler-derived process, allows quantification of myocardial systolic function. We investigate whether SRI quantifies the contractile reserve during dobutamine stress tests in heart transplant patients (HT), when compared with normal individuals. METHODS: An incremental dobutamine test (5 to 40 microg/kg per minute) was performed in 10 HT and 15 control subjects, all of whom displayed normal coronary angiography. Gray-scale and color myocardial Doppler data were acquired in standard B-mode views at baseline, low-dose, peak, and recovery. Longitudinal SR was processed from the myocardial velocities for each segment. The changes in maximal systolic SR were used to quantify myocardial contractile reserve. RESULTS: Dobutamine infusion failed to induce clinical symptoms or electrocardiographic (ECG) changes in either group. Visually determined wall motion score was considered normal in all segments for each stage of the dobutamine stress. Heart rate was augmented similarly in both groups during dobutamine infusion. In controls, systolic SR increased gradually with incremental dobutamine dose and returned to baseline values upon recovery. Conversely, in HT patients, the increase in systolic SR was blunted at peak dobutamine, at which point it was significantly different vs controls. CONCLUSIONS: Quantitative assessment of myocardial function using SRI during dobutamine stress revealed an impaired contractile reserve in HT patients with normal coronary angiography. These subtle changes in regional myocardial function could not be identified using visual wall motion scoring. Additional studies are necessary to evaluate whether SR imaging detection of contractile reserve impairment will improve clinical efficiency or event prediction in this population.

Should we still perform angioplasty and stenting of an unprotected left main coronary artery stenosis in heart transplant patients? Two new cases and a review of the literature.

Coronary balloon angioplasty with stent implantation has emerged as a possible alternative to bypass grafting or repeat transplantation in left main coronary stenosis in heart transplant patients. We report 2 new cases of stent implantation for unprotected and isolated left main stenosis in heart transplant patients. Despite an initially successful procedure, restenosis prompted the performance of bypass surgery in both patients. The relative advantages and disadvantages of available techniques of revascularization are discussed in the context of the literature.

Duration and reinstatement of myocardial protection against infarction by ischemic preconditioning in open chest dogs.

These studies were undertaken to determine the duration of protection against myocardial infarction provided by ischemic preconditioning in the canine heart, and to learn if cardioprotection can be restored by another preconditioning stimulus when the initial effect is lost. Control and four preconditioning groups of anesthetized, open-chest dogs were compared. All underwent a test 60 min episode of ischemia, induced by occlusion of the anterior descending (LAD) artery, followed by 3 h of reperfusion. Preconditioning was induced by one 10 min LAD occlusion, followed by either 10 min, 2, 3, or 5 h of reperfusion. In order to test whether preconditioning could be reinstated, another group of dogs with preconditioning plus 3 h reperfusion underwent a second 10 min preconditioning stimulus with 10 min reperfusion before the 60 min test-occlusion. Infarct size (as percent of area-at-risk) was analyzed (using analysis of covariance) with respect to coronary collateral blood flow measured with radioactive microspheres. Infarct size was limited markedly by preconditioning (23+/-6 v 6+/-2%, P<0.05) but the protective effect was dissipated partially after 2 h reperfusion and was dissipated completely after 3 h reperfusion (20+/-4%, non-significant v Control and significant P<0.05 v preconditioning). Protection was restored in three of six dogs with preconditioning +5 h reperfusion, suggesting that the second window of protection appears early in some canine hearts. When preconditioning was repeated after 3 h reperfusion, cardioprotection was reinstated fully (7+/-2%, P<0.05 v Control and NS v preconditioning). The results show that maximal preconditioning cardioprotection is present in the dog heart after 10 min of reperfusion and is dissipated totally following 3 h of reperfusion. However, a second preconditioning stimulus of 10 min of ischemia followed by 10 min of reperfusion to the dissipated preconditioned heart reinstates full preconditioning. Thus, this model provides a system to test for theoretical causes of the preconditioned state. Final mediators should be present when preconditioning is present and absent when preconditioning is dissipated. It is noteworthy that a second window of protection appeared in 50% of dogs when the period of reperfusion was extended to 5 h.

Metabolism of preconditioned myocardium: effect of loss and reinstatement of cardioprotection.

Ischemic preconditioning is associated with slower destruction of the adenine nucleotide pool and a slower rate of anaerobic glycolysis during subsequent ischemic stress. Whether this association is causal is uncertain. Using metabolite levels found at baseline and after a 15 min test episode of ischemia, this study tested for concordance, or lack thereof, between the presence or absence of metabolic features v the presence or absence of the preconditioned state. Dogs were assigned to one of four groups: non-preconditioned control (C), full preconditioning (PC) caused by 10 min ischemia (I)+10 min reperfusion (R), dissipated PC (DPC) caused by 10 min I and 180 min R, or reinstated PC in which PC was reinstated in DPC hearts by another 10 min I and 10 min R. At baseline, PC and RPC hearts had a 25% or more decrease in the adenine nucleotide pool (summation operatorAd), a substantial creatine phosphate (CP) overshoot, and a 4-6 times elevation in tissue glucose (G). Of these changes, the decreased summation operatorAd and the CP overshoot persisted during DPC, whereas only G returned to control. Thus, increased G was the only baseline feature, which was concordant with the preconditioned state. The response to ischemic stress in PC and RPC tissue included less lactate production and much less degradation of the summation operatorAd pool to nucleosides and bases than in the C or DPC groups. Thus, slower destruction of the summation operatorAd pool and slower lactate production during ischemia also were concordant with the PC state. The results support the hypothesis that a reduction in energy demand is an essential component of the mechanism of cardioprotection in preconditioned myocardium. However, the mechanism through which ischemic preconditioning results in lower energy demand remains to be established.

Thiopurine S-methyltransferase gene polymorphism is predictive of azathioprine-induced myelosuppression in heart transplant recipients.

Azathioprine (AZA) is metabolized via the cytosolic enzyme thiopurine S-methyltransferase (TPMT). TPMT activity exhibits genetic polymorphism with four prevalent (75%) mutant alleles TPMT*2 (G238C) and TPMT*3 (A719G and/or G460A) and a wild-type allele TPMT*1. To test the hypothesis that presence of these mutations is associated with greater toxicity of AZA in heart transplant recipients, 30 consecutive patients treated with AZA were followed up for the first month after heart transplant. Mutation of TPMT gene (mutation-specific polymerase chain reaction-based methods) was observed in four patients (A719G: n = 2; A719G plus G460: n = 2). Agranulocytosis did not occur in patients with the wild genotype. It occurred in the two patients with mutation A719G and there was a 40% drop in neutrophils in the two other patients. Discontinuation of AZA in the four mutant patients corrected for the drop. Presence of TPMT mutations is associated with a greater likelihood of agranulocytosis. Determination of these mutations could reduce the risk for hematological side-effects.

Improved myocardial tolerance to ischaemia in the diabetic rabbit.

Because cardiac complications after myocardial infarction are more frequent in diabetics, we tested whether experimentally-induced diabetes may increase ischaemic myocardial injury in 23 rabbits. Diabetes was induced in randomized rabbits with the alloxan method. After 2 months, diabetic rabbits underwent a 30-min coronary occlusion followed by 3-h reperfusion and were compared with controls. Collateral flow was measured by the radioactive microsphere technique and infarct size by tetrazolium staining. Infarct size represented 28.6+/-4% of area-at-risk in controls and 16.5+/-3% in diabetics (P<0.05). Collateral flow (0.06+/-0.03 ml/min/g in controls and 0.014+/-0.004 ml/min/g in diabetics) and area-at-risk (50.2+/-4.2% of left ventricle in controls and 53.9+/-5. 4% in diabetics) were similar in both groups. There was a significant positive correlation between area-at-risk and infarct size in both groups (r=0.60 and 0.70, respectively) and for a given area-at-risk, diabetic rabbits developed smaller myocardial infarction than controls (covariance analysis, P<0.01). In additional experiments, hyperglycemia induced by intravenous glucose infusion in non-diabetic rabbits did not protect the ischaemic myocardium (infarct size: 37.9+/-12.5%). In conclusion, diabetes in the rabbit induces a chronic and metabolic form of preconditioning. Further studies are needed to explore the mechanism and time course of this protection.