alogliptin and Heart-Failure

Dipeptidyl peptidase-4 (DPP-4) inhibitors are oral antidiabetic drugs that safely reduce the blood glucose level over the long term. In Japan, DPP-4 inhibitors have become the oral antidiabetic drugs most frequently prescribed for patients with type 2 diabetes. However, the results of several cardiovascular outcomes studies have suggested that some DPP-4 inhibitors may increase the risk of hospitalization for heart failure. In patients with diabetes, heart failure is the most frequent cardiovascular condition, and it has a negative impact on the quality of life as well as being a potentially fatal complication. Therefore, it is important to determine whether an increased risk of heart failure is associated with certain DPP-4 inhibitors or is a class effect of these drugs. This review explores the mechanism by which DPP-4 inhibitors may increase the risk of heart failure and possible differences among these drugs. The available research suggests that DPP-4 inhibitors cause sympathetic activation as a class effect and this may increase the risk of heart failure. Unlike other DPP-4 inhibitors, sitagliptin and alogliptin are mainly excreted in the urine and suppress renal sodium-hydrogen exchanger 3 activity. These two drugs did not increase the risk of hospitalization for heart failure in large-scale cardiovascular outcomes studies.

Topics: Adult; Cardiovascular Diseases; Diabetes Mellitus, Type 2; Dipeptidyl-Peptidase IV Inhibitors; Female; Heart Failure; Hospitalization; Humans; Hypoglycemic Agents; Japan; Male; Middle Aged; Piperidines; Quality of Life; Sitagliptin Phosphate; Uracil

The incretin-based therapies, dipeptidyl peptidase-4 (DPP4) inhibitors and glucagon-like peptide-1 (GLP-1) analogs, are important new classes of therapy for type 2 diabetes mellitus (T2DM). These agents prolong the action of the incretin hormones, GLP-1 and glucose-dependent insulinotropic polypeptide (GIP), by inhibiting their breakdown. The incretin hormones improve glycemic control in T2DM by increasing insulin secretion and suppressing glucagon levels. The cardiovascular (CV) effects of the incretin-based therapies have been of substantial interest since 2008, when the US Food and Drug Administration began to require that all new therapies for diabetes undergo rigorous assessment of CV safety through large-scale CV outcome trials. This article reviews the most recent CV outcome trials of the DPP-4 inhibitors (SAVOR-TIMI 53, EXAMINE, and TECOS) as evidence that the incretin-based therapies have acceptable CV safety profiles for patients with T2DM. The studies differ with regard to patient population, trial duration, and heart failure outcomes but show similar findings for CV death, nonfatal myocardial infarction, and stroke, as well as hospitalization for unstable angina.

Topics: Adamantane; Cardiovascular Diseases; Cardiovascular System; Clinical Trials as Topic; Diabetes Mellitus, Type 2; Dipeptides; Dipeptidyl-Peptidase IV Inhibitors; Glucagon-Like Peptide 1; Heart Failure; Humans; Hypoglycemic Agents; Incretins; Piperidines; Sitagliptin Phosphate; Uracil

Several randomized, controlled clinical trials were initiated some years ago in order to evaluate the cardiovascular safety of the new antidiabetic drugs in patients with type 2 diabetes due to requirements from regulatory bodies. Four trials with incretin-based drugs (saxagliptin, alogliptin, sitagliptin and lixisenatide) have been completed so far. Based on the primary outcome endpoints of these trials no cardiovascular risks were found with incretins in patients with type 2 diabetes. As for saxagliptin, the hospitalization for heart failure was investigated as a secondary endpoint, and an increased risk was observed in the respective trial; however, this observation was widely debated later in the literature. Together with ongoing trials of other novel antihyperglycemic agents, these data will provide more robust evidence about the cardiovascular safety of incretin-based antidiabetic treatment in patients with type 2 diabetes.

Topics: Adamantane; Cardiovascular System; Diabetes Mellitus, Type 2; Dipeptides; Dipeptidyl-Peptidase IV Inhibitors; Evidence-Based Medicine; Heart Failure; Humans; Hypoglycemic Agents; Incretins; Peptides; Piperidines; Randomized Controlled Trials as Topic; Sitagliptin Phosphate; Time Factors; Uracil

The treatment of diabetes mellitus type 2 is effective, but still is not optimal. DPP4 inhibitors (gliptins) are a new group of peroral antidiabetic drugs. The third clinical mortality study with gliptins in patients with diabetes mellitus type 2 was finished in 2015. The studies are known under acronym TECOS, SAVOR and EXAMINE and the tested drugs are sitagliptin, saxagliptin and alogliptin. The studies included about 37,000 patients. The studies confirmed the cardiovascular safety of the DPP4 inhibitors, but the question about increased heart failure remains open. The effectiveness of lowering glycaemia (glycated haemoglobin) was confirmed and also the pancreatic safety is confirmed.

Topics: Adamantane; Blood Glucose; Diabetes Mellitus, Type 2; Dipeptides; Dipeptidyl-Peptidase IV Inhibitors; Glycated Hemoglobin; Heart Failure; Humans; Hypoglycemic Agents; Piperidines; Sitagliptin Phosphate; Uracil

Although recent reports suggest an association between saxagliptin and an increased risk of admissions for heart failure, it is not clear whether dipeptidyl peptidase IV (DPP-IV) inhibition contributes to heart failure in high-risk patients. The purpose of this research is to understand heart failure risk among high-risk patients with type 2 diabetes.. This is a systematic review of data published in full papers and abstract form using the terms DPP-IV inhibitors and heart failure published since October 2013. Data from insurance and hospital databases were combined with those from multiple published trials, including the Saxagliptin Assessment of Vascular Outcomes Recorded in Patients with Diabetes Mellitus-Thrombolysis in Myocardial Infarction 53 (SAVOR-TIMI 53) trial; Examination of Cardiovascular Outcomes With Alogliptin Versus Standard of Care (EXAMINE), and Vildagliptin in Ventricular Dysfunction Diabetes (VIVIDD) trial as well as pooled analyses of linagliptin and saxagliptin placebo-controlled trials to examine heart failure among patients represented in those datasets.. A meta-analysis of the 9 datasets showed an increase in heart failure with dipeptidyl peptidase IV inhibitors of 15% (P = 0.017). There was no statistical heterogeneity, nor was there a statistical difference between cohort studies and randomized, controlled trials (P = 0.3), even though cohort studies alone were not significant (relative risk: 1.1; P = 0.32). Removing SAVOR-TIMI 53 data produced an insignificant increase in heart failure of 12% (P = 0.09) in the rest of the studies. In the randomized, controlled trials, the increased risk was 24% (P = 0.002). There was no statistical difference between those studies with and without baseline cardiovascular disease (P = 0.58), although the cardiovascular disease studies were borderline significant (P = 0.06). There was no publication bias.. There are data from studies using sitagliptin, saxagliptin, and alogliptin showing that these agents may increase the risk of hospitalization for heart failure. More data are required for a definitive conclusion.

Topics: Adamantane; Diabetes Mellitus, Type 2; Dipeptides; Dipeptidyl-Peptidase IV Inhibitors; Heart Failure; Hospitalization; Humans; Nitriles; Piperidines; Pyrrolidines; Sitagliptin Phosphate; Uracil; Vildagliptin

Topics: Acute Coronary Syndrome; Aged; Biomarkers; Blood Proteins; Diabetes Mellitus, Type 2; Dipeptidyl-Peptidase IV Inhibitors; Double-Blind Method; Female; Galectin 3; Galectins; Growth Differentiation Factor 15; Heart Disease Risk Factors; Heart Failure; Hospitalization; Humans; Male; Middle Aged; Natriuretic Peptide, Brain; Peptide Fragments; Piperidines; Prognosis; Risk Assessment; Troponin I; Uracil

We sought to assess the risk of major adverse cardiovascular events (MACE) by utilizing high-sensitivity C-reactive protein (hsCRP) level and low-density lipoprotein cholesterol (LDL-C) in patients with type 2 diabetes and recent acute coronary syndrome.. Study participants enrolled in the EXAMINE trial (Clinical trials registration number: NCT00968708) and were stratified by baseline hsCRP levels (<1, 1-3 and >3 mg/L). They were also sub-divided into 4 groups according to baseline hsCRP (≤3 or >3 mg/L) and achieved LDL-C (<70 or ≥70 mg/dL) levels. Among 5380 patients, the MACE rate, a composite of cardiovascular death, non-fatal acute myocardial infarction and non-fatal stroke, was evaluated during the 30 months of follow-up.. Cumulative incidence of MACE was 11.5% (119 events), 14.6% (209 events) and 18.4% (287 events) in patients with hsCRP levels of <1, 1 to 3 and >3 mg/L, respectively (P < .001). In patients with hsCRP >3 mg/L, the adjusted hazard ratio (95% confidence interval) was 1.42 (1.13, 1.78; P = .002) for MACE compared with patients with hsCRP <1 mg/L. MACE cumulative incidences were 11.0% (128 events), 14.4% (100 events), 15.6% (194 events) and 21.3% (182 events) in patients with low LDL-C and low hsCRP, low LDL-C and high hsCRP, high LDL-C and low hsCRP, and high LDL-C and high hsCRP levels, respectively (P < .001).. Levels of hsCRP were associated with recurrent cardiovascular events in patients with type 2 diabetes and recent acute coronary syndrome, and this association appears to be independent of and additive to the achieved LDL-C level.

Topics: Acute Coronary Syndrome; C-Reactive Protein; Cholesterol, LDL; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Double-Blind Method; Female; Heart Failure; Humans; Hypoglycemic Agents; Male; Middle Aged; Myocardial Infarction; Myocardial Revascularization; Piperidines; Standard of Care; Treatment Outcome; Uracil

Antihyperglycemic therapies may increase the risk of cardiovascular events including hospitalization for heart failure. There is a paucity of data evaluating the cardiovascular safety of antihyperglycemic therapies in the high-risk period following an acute coronary syndrome (ACS).. The EXAMINE (Examination of Cardiovascular Outcomes with Alogliptin versus Standard of Care) trial randomized 5380 patients who were 15 to 90 days post ACS to the dipeptidyl dipeptidase-IV (DPP-IV) inhibitor alogliptin versus placebo; mean follow-up was 18 months. Using a landmark analysis, we assessed the (1) burden of cardiovascular events from randomization to 6 months (early period) and from 6 months to the end of follow-up (late period) and (2) the risk of cardiovascular events associated with early (up to 6 months) and chronic (6 months to end of follow-up) DPP-IV inhibition with alogliptin. Patients with early versus late events had similar baseline demographic profiles. Overall, 42.1% of the composite of cardiovascular death/myocardial infarction/stroke and 47.5% of hospitalization for heart failure occurred in the early period. Early DPP-IV inhibition did not increase the risk of early cardiovascular death/myocardial infarction/stroke (hazard ratio 0.96, 95% confidence interval, 0.76-1.21) or hospitalization for heart failure (1.23, 95% confidence interval, 0.84-1.82). Similarly, chronic DPP-IV inhibition did not increase the risk of late cardiovascular death/myocardial infarction/stroke (hazard ratio 1.03, 95% confidence interval, 0.89-1.26) or hospitalization for heart failure (hazard ratio 1.02, 95% confidence interval, 0.85-1.22).. Early after an ACS, patients with type 2 diabetes mellitus experience a significant burden of HF events and recurrent ACS. DPP-IV inhibition with alogliptin appears to be safe even in the high-risk period following an ACS.

Topics: Acute Coronary Syndrome; Aged; Diabetes Mellitus, Type 2; Dipeptidyl-Peptidase IV Inhibitors; Double-Blind Method; Female; Heart Failure; Humans; Male; Middle Aged; Myocardial Infarction; Piperidines; Recurrence; Risk Assessment; Risk Factors; Stroke; Time Factors; Treatment Outcome; Uracil

Background Blood pressure ( BP ) treatment goals in patients with diabetes mellitus and increased cardiovascular risk remain controversial. Our study objective was to determine cardiovascular outcomes according to achieved BP s over the average follow-up period in the EXAMINE (Examination of Cardiovascular Outcomes With Alogliptin Versus Standard of Care) trial. Methods and Results EXAMINE was a cardiovascular outcomes trial in 5380 patients with type 2 diabetes mellitus and recent acute coronary syndromes. Risks of major adverse cardiac events and cardiovascular death or heart failure were analyzed using a Cox proportional hazards model with adjustment for baseline covariates in 10-mm Hg increments of clinician-measured systolic BP from ≤100 to >160 mm Hg and diastolic BP from ≤60 to >100 mm Hg averaged during the 24 months after randomization. Based on 2015 guidelines from the American College of Cardiology, the American Heart Association and the American Society of Hypertension and 2017 American Diabetes Association guidelines, systolic BP s of 131 to 140 mm Hg and diastolic BP s of 81 to 90 mm Hg were the reference groups. A U-shaped relationship between cardiovascular outcomes and BP s was observed. Importantly, compared with the systolic BP reference group, adjusted hazard ratios for major adverse cardiac events and cardiovascular death or heart failure were significantly higher in patients with systolic BP s <130 mm Hg. Similarly, compared with the diastolic BP reference group, adjusted hazard ratios for major adverse cardiac events and for cardiovascular death or heart failure were significantly higher for diastolic BP s <80 mm Hg. Conclusions In patients with type 2 diabetes mellitus and recent acute coronary syndrome, average BP s <130/80 mm Hg were associated with worsened cardiovascular outcomes. These data suggest that intensive control of BP in patients with type 2 diabetes mellitus and ischemic heart disease should be evaluated in a prospective randomized trial. Clinical Trial Registration URL : https://www.clinicaltrials.gov . Unique identifier: NCT 00968708.

Topics: Aged; Analysis of Variance; Blood Pressure Determination; Cause of Death; Diabetes Mellitus, Type 2; Diabetic Cardiomyopathies; Double-Blind Method; Female; Heart Failure; Hospitalization; Humans; Hypertension; Hypoglycemic Agents; Male; Middle Aged; Myocardial Ischemia; Piperidines; Prognosis; Prospective Studies; United States; Uracil

The EXAMINE trial showed non-inferiority of the DPP-4 inhibitor alogliptin to placebo on major adverse cardiac event (MACE) rates in patients with type 2 diabetes and recent acute coronary syndromes. Concerns about excessive rates of in-hospital heart failure in another DPP-4 inhibitor trial have been reported. We therefore assessed hospital admission for heart failure in the EXAMINE trial.. Patients with type 2 diabetes and an acute coronary syndrome event in the previous 15-90 days were randomly assigned alogliptin or placebo plus standard treatment for diabetes and cardiovascular disease prevention. The prespecified exploratory extended MACE endpoint was all-cause mortality, non-fatal myocardial infarction, non-fatal stroke, urgent revascularisation due to unstable angina, and hospital admission for heart failure. The post-hoc analyses were of cardiovascular death and hospital admission for heart failure, assessed by history of heart failure and brain natriuretic peptide (BNP) concentration at baseline. We also assessed changes in N-terminal pro-BNP (NT-pro-BNP) from baseline to 6 months. This study is registered with ClinicalTrials.gov, number NCT00968708.. 5380 patients were assigned to alogliptin (n=2701) or placebo (n=2679) and followed up for a median of 533 days (IQR 280-751). The exploratory extended MACE endpoint was seen in 433 (16·0%) patients assigned to alogliptin and in 441 (16·5%) assigned to placebo (hazard ratio [HR] 0·98, 95% CI 0·86-1·12). Hospital admission for heart failure was the first event in 85 (3·1%) patients taking alogliptin compared with 79 (2·9%) taking placebo (HR 1·07, 95% CI 0·79-1·46). Alogliptin had no effect on composite events of cardiovascular death and hospital admission for heart failure in the post hoc analysis (HR 1·00, 95% CI 0·82-1·21) and results did not differ by baseline BNP concentration. NT-pro-BNP concentrations decreased significantly and similarly in the two groups.. In patients with type 2 diabetes and recent acute coronary syndromes, alogliptin did not increase the risk of heart failure outcomes.. Takeda Development Center Americas.

Topics: Acute Coronary Syndrome; Aged; Angina, Unstable; Diabetes Mellitus, Type 2; Diabetic Cardiomyopathies; Double-Blind Method; Female; Heart Failure; Hospitalization; Humans; Hypoglycemic Agents; Male; Middle Aged; Myocardial Infarction; Natriuretic Peptide, Brain; Peptide Fragments; Piperidines; Risk Factors; Stroke; Uracil

In 2008, the US Food and Drug Administration (FDA) issued Draft Guidance on investigating cardiovascular risk with oral diabetic drugs, including dipeptidyl peptidase-4 inhibitors (DPP-4i). In 2014, underpowered, post hoc analyses of clinical trials suggested an increased risk of heart failure with the use of these products. As such, we assessed disproportionate reporting of major adverse cardiac events (MACE) among reports for DPP-4i submitted to the FDA Adverse Event Reporting System (FAERS) from 2006 to 2015.. We assessed the empirical Bayes geometric mean (EBGM) and its lower bound (EB05) of the relative reporting ratio for MACE among DPP-4i reports in the full FAERS database and in a subset of reports limited to cardiovascular and diabetic drugs. We then compared the EB05 in these 2 analyses and calculated the percent positive agreement for signals of disproportional reporting (SDRs) involving MACE.. Of 180.3 million adverse event reports, 13.4 million were for diabetic and cardiovascular drugs. In the cardiovascular subset, there was an SDR for heart failure with linagliptin (EB05 = 2782.47) and saxagliptin (EB05 = 2.40), myocardial infarction with alogliptin (EB05 = 290.11), and cerebral infarction with sitagliptin (EB05 = 2.80). Of the 14 MACE, 8 had a percent positive agreement ≥50% for an SDR in both analyses. Overall, the cardiovascular subset elicited 11 more SDRs for DPP-4i than the full dataset.. Postmarketing surveillance of DPP-4i through FAERS suggest increased reporting of MACE, supporting the current FDA warning of heart failure risk. This suggests the need for additional longitudinal, observational research into the association of DPP-4i and other MACE.

Topics: Adamantane; Administration, Oral; Adverse Drug Reaction Reporting Systems; Aged; Bayes Theorem; Databases, Factual; Diabetes Mellitus, Type 2; Dipeptides; Dipeptidyl-Peptidase IV Inhibitors; Female; Heart Failure; Humans; Linagliptin; Male; Middle Aged; Piperidines; Practice Guidelines as Topic; Sitagliptin Phosphate; United States; United States Food and Drug Administration; Uracil

Saxagliptin statistically significantly increased the risk of hospitalization for heart failure compared with placebo in the clinical trial of SAVOR-TIMI 53. Neither the reason why only saxagliptin among several dipeptidyl peptidase-4 (DPP-4) inhibitors increased the risk, nor the clinical implication of the result has been explained.. To evaluate the risk of hospitalization for heart failure associated with DPP-4 inhibitors by using an alternative measure to the hazard ratio.. We used the difference in restricted mean survival time (RMST) between DPP-4 inhibitors and placebo to evaluate the risk of cardiovascular events, including hospitalization for heart failure associated with DPP-4 inhibitors. Three randomized clinical trials with cardiovascular events as a primary end point-EXAMINE (alogliptin), SAVOR-TIMI 53 (saxagliptin), and TECOS (sitagliptin)-were reevaluated by estimating the RMSTs for the DPP-4 inhibitors and placebo based on the reconstructed individual patient data for each time-to-event outcome from publicly available information.. The differences of RMSTs (DPP-4 inhibitors minus placebo) for hospitalization for heart failure were -4 days [-6, -2] in the SAVOR-TIMI 53 (720 days follow-up), -3 days [-9, 3] in the EXAMINE (900 days follow-up), and 1 day [-5, 7] in the TECOS (1440 days follow-up). There were no substantial differences in the risk of other cardiovascular outcomes between DPP-4 inhibitors and placebo.. There are no substantial clinically relevant differences in the risk of cardiovascular events, including hospitalization for heart failure, between 3 of the DPP-4 inhibitors and placebo.

Topics: Adamantane; Diabetes Mellitus, Type 2; Dipeptides; Dipeptidyl-Peptidase IV Inhibitors; Heart Failure; Hospitalization; Humans; Piperidines; Proportional Hazards Models; Randomized Controlled Trials as Topic; Risk; Sitagliptin Phosphate; Uracil

Ample evidence demonstrates cardiovascular protection by incretin-based therapy using dipeptidyl peptidase 4 inhibitor (DPP4i) and glucagon-like peptide-1 (GLP-1) under either diabetic or nondiabetic condition. Their action on myocardium is mediated by the cyclic AMP (cAMP) signal; however, the pathway remains uncertain. This study was conducted to address the effect of DPP4i/GLP-1/cAMP axis on cardiac dysfunction and remodeling induced by pressure overload (thoracic aortic constriction [TAC]) independently of diabetes mellitus.. DPP4i (alogliptin, 10 mg/kg per day for 4 weeks) prevented TAC-induced contractile dysfunction, remodeling, and apoptosis of myocardium in a GLP-1 receptor antagonist (exendin [9-39])-sensitive fashion. In TAC, circulating level of GLP-1 (in pmol/L; 0.86 ± 0.10 for TAC versus 2.13 ± 0.54 for sham control) unexpectedly declined and so did the myocardial cAMP concentration (in pmol/mg protein; 33.0 ± 1.4 for TAC versus 42.2 ± 1.5 for sham). Alogliptin restored the decline in the GLP-1/cAMP levels observed in TAC, thereby augmented cAMP signaling effectors (protein kinase A [PKA] and exchange protein directly activated by cAMP 1 [EPAC1]). In vitro assay revealed distinct roles of PKA and EPAC1 in cardiac apoptosis. EPAC1 promoted cardiomyocyte survival via concomitant increase in B cell lymphoma-2 (Bcl-2) expression and activation of small G protein Ras-related protein 1 (Rap1) in a cAMP dose-dependent and PKA-independent fashion.. DPP4i restores cardiac remodeling and apoptosis caused by the pathological decline in circulating GLP-1 in response to pressure overload. EPAC1 is essential for cardiomyocyte survival via the cAMP/Rap1 activation independently of PKA.

Topics: Animals; Apoptosis; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Dipeptidyl Peptidase 4; Dipeptidyl-Peptidase IV Inhibitors; Disease Models, Animal; Dose-Response Relationship, Drug; Glucagon-Like Peptide 1; Guanine Nucleotide Exchange Factors; Heart Failure; Male; Mice, Inbred C57BL; Myocytes, Cardiac; Peptide Fragments; Piperidines; Proto-Oncogene Proteins c-bcl-2; rap1 GTP-Binding Proteins; Signal Transduction; Uracil; Ventricular Remodeling

Topics: Adamantane; Cardiovascular Diseases; Diabetes Mellitus, Type 2; Dipeptides; Dipeptidyl-Peptidase IV Inhibitors; Heart Failure; Humans; Hypoglycemic Agents; Piperidines; Risk Factors; Sitagliptin Phosphate; Uracil

Dipeptidyl peptidase-4 (DPP-4) inhibitors were recently reported to have cardioprotective effects via amelioration of ventricular function. However, the role of DPP-4 inhibition in atrial remodeling, especially of the arrhythmogenic substrate, remains unclear.. We investigated the effects of a DPP-4 inhibitor, alogliptin, on atrial fibrillation (AF) in a rabbit model of heart failure caused by ventricular tachypacing (VTP).. Rabbits subjected to VTP at 380 bpm for 1 or 3 weeks, with or without alogliptin treatment, were assessed using echocardiography, electrophysiology, histology, and immunoblotting and compared with nonpaced animals.. VTP rabbits exhibited increased duration of atrial burst pacing-induced AF, whereas administration of alogliptin shortened this duration by 73%. The extent of atrial fibrosis after VTP was reduced by 39% in the alogliptin-treated group. VTP rabbits treated with alogliptin displayed a 1.6-fold increase in left atrial myocardial capillary density compared with nontreated rabbits. A 2-fold increase in endothelial nitric oxide synthase (eNOS) phosphorylation was observed in the left atrium of alogliptin-treated rabbits compared with nontreated rabbits. Moreover, a nitric oxide synthase inhibitor (N(ω)-nitro-l-arginine methyl ester) blocked the beneficial effects of alogliptin on AF duration, fibrosis, and capillary density.. Alogliptin shortened the duration of AF caused by VTP-induced fibrotic atrial tissue by augmenting atrial angiogenesis and activating eNOS. Our findings suggest that DPP-4 inhibitors may be useful in the prevention of heart failure-induced AF.

Topics: Animals; Atrial Fibrillation; Blotting, Western; Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; Echocardiography; Electrophysiology; Endothelium; Enzyme-Linked Immunosorbent Assay; Fibrosis; Fluorescent Antibody Technique; Heart Atria; Heart Failure; Male; Neovascularization, Physiologic; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Phosphorylation; Piperidines; Rabbits; Tachycardia, Ventricular; Uracil