Neuroendocrine changes in acute myocardial infarction

Glial cell activity in cardiovascular diseases and risk of acute myocardial infarction

Growing evidence indicates that the pathophysiological link between the brain and heart underlies cardiovascular diseases, specifically acute myocardial infarction (AMI). Astrocytes are the most abundant glial cells in the central nervous system and provide support/protection for neurons. Astrocytes and peripheral glial cells are emerging as key modulators of the brain-heart axis in AMI, by affecting sympathetic nervous system activity (centrally and peripherally). This review, therefore, aimed to gain an improved understanding of glial cell activity and AMI risk. This includes discussions on the potential role of contributing factors in AMI risk, i.e., autonomic nervous system dysfunction, glial-neurotrophic and ischemic risk markers [glial cell line-derived neurotrophic factor (GDNF), astrocytic S100 calcium-binding protein B (S100B), silent myocardial ischemia, and cardiac troponin T (cTnT)]. Consideration of glial cell activity and related contributing factors in certain brain-heart disorders, namely, blood-brain barrier dysfunction, myocardial ischemia, and chronic psychological stress, may improve our understanding regarding the pathological role that glial dysfunction can play in the development/onset of AMI. Here, findings demonstrated perturbations in glial cell activity and contributing factors (especially sympathetic activity). Moreover, emerging AMI risk included sympathovagal imbalance, low GDNF levels reflecting prothrombic risk, hypertension, and increased ischemia due to perfusion deficits (indicated by S100B and cTnT levels). Such perturbations impacted blood-barrier function and perfusion that were exacerbated during psychological stress. Thus, greater insights and consideration regarding such biomarkers may help drive future studies investigating brain-heart axis pathologies to gain a deeper understanding of astrocytic glial cell contributions and unlock potential novel therapies for AMI.

Involvement of Vasopressin in Tissue Hypoperfusion during Cardiogenic Shock Complicating Acute Myocardial Infarction in Rats

Acute heart failure (AHF) due to acute myocardial infarction (AMI) is likely to involve cardiogenic shock (CS), with neuro-hormonal activation. A relationship between AHF, CS and vasopressin response is suspected. This study aimed to investigate the implication of vasopressin on hemodynamic parameters and tissue perfusion at the early phase of CS complicating AMI. Experiments were performed on male Wistar rats submitted or not to left coronary artery ligation (AMI and Sham). Six groups were studied Sham and AMI treated or not with either a vasopressin antagonist SR-49059 (Sham-SR, AMI-SR) or agonist terlipressin (Sham-TLP, AMI-TLP). Animals were sacrificed one day after surgery (D₁) and after hemodynamic parameters determination. Vascular responses to vasopressin were evaluated, ex vivo, on aorta. AHF was defined by a left ventricular ejection fraction below 40%. CS was defined by AHF plus tissue hypoperfusion evidenced by elevated serum lactate level or low mesenteric oxygen saturation (SmO₂) at D₁. Mortality rates were 40% in AMI, 0% in AMI-SR and 33% in AMI-TLP. Immediately after surgery, a sharp decrease in SmO₂ was observed in all groups. At D₁, SmO₂ recovered in Sham and in SR-treated animals while it remained low in AMI and further decreased in TLP-treated groups. The incidence of CS among AHF animals was 72% in AMI or AMI-TLP while it was reduced to 25% in AMI-SR. Plasma copeptin level was increased by AMI. Maximal contractile response to vasopressin was decreased in AMI (32%) as in TLP- and SR- treated groups regardless of ligation. Increased vasopressin secretion occurring in the early phase of AMI may be responsible of mesenteric hypoperfusion resulting in tissue hypoxia. Treatment with a vasopressin antagonist enhanced mesenteric perfusion and improve survival. This could be an interesting therapeutic strategy to prevent progression to cardiogenic shock.

The Heart as a Target of Vasopressin and Other Cardiovascular Peptides in Health and Cardiovascular Diseases

The automatism of cardiac pacemaker cells, which is tuned, is regulated by the autonomic nervous system (ANS) and multiple endocrine and paracrine factors, including cardiovascular peptides. The cardiovascular peptides (CPs) form a group of essential paracrine factors affecting the function of the heart and vessels. They may also be produced in other organs and penetrate to the heart via systemic circulation. The present review draws attention to the role of vasopressin (AVP) and some other cardiovascular peptides (angiotensins, oxytocin, cytokines) in the regulation of the cardiovascular system in health and cardiovascular diseases, especially in post-infarct heart failure, hypertension and cerebrovascular strokes. Vasopressin is synthesized mostly by the neuroendocrine cells of the hypothalamus. There is also evidence that it may be produced in the heart and lungs. The secretion of AVP and other CPs is markedly influenced by changes in blood volume and pressure, as well as by other disturbances, frequently occurring in cardiovascular diseases (hypoxia, pain, stress, inflammation). Myocardial infarction, hypertension and cardiovascular shock are associated with an increased secretion of AVP and altered responsiveness of the cardiovascular system to its action. The majority of experimental studies show that the administration of vasopressin during ventricular fibrillation and cardiac arrest improves resuscitation, however, the clinical studies do not present consisting results. Vasopressin cooperates with the autonomic nervous system (ANS), angiotensins, oxytocin and cytokines in the regulation of the cardiovascular system and its interaction with these regulators is altered during heart failure and hypertension. It is likely that the differences in interactions of AVP with ANS and other CPs have a significant impact on the responsiveness of the cardiovascular system to vasopressin in specific cardiovascular disorders.

Bilateral Superior Cervical Sympathectomy Activates Signal Transducer and Activator of Transcription 3 Signal to Alleviate Myocardial Ischemia-Reperfusion Injury

Background

There is growing evidence about the effect of bilateral superior cervical sympathectomy on myocardial ischemia-reperfusion (I/R) injury. Studies have increasingly found that the signal transducer and activator of transcription 3 (STAT3) plays a protective role in myocardial I/R injury. However, the precise mechanism is unknown. The present study explored the bilateral superior cervical sympathectomy’s effect and potential mechanism in mice myocardial I/R injury.

Methods

The left heart I/R injury model was created by ligating the anterior descending branch of the coronary artery for 30 min followed by reperfusion. Bilateral superior cervical sympathectomy was performed before myocardial I/R injury. To evaluate the effect of bilateral superior cervical sympathectomy on the myocardium, we examined the myocardial infarct size and cardiac function. Then, myocardial apoptosis, inflammation, and oxidative stress were detected on the myocardium. Furthermore, the expression of STAT3 signal in myocardial tissue was measured by western blotting. To further examine the cardioprotective effect of STAT3 after bilateral superior cervical sympathectomy, the STAT3 inhibitor (static) was utilized to inhibit the phosphorylation of STAT3.

Results

The results showed that the myocardial I/R injury decreased and the cardiac function recovered in the myocardial I/R injury after cervical sympathectomy. Meanwhile, cervical sympathectomy reduced the myocardial distribution of the sympathetic marker tyrosine hydroxylase (TH) and systemic sympathetic tone. And levels of oxidative stress, inflammatory markers, and apoptosis were reduced in myocardial tissue. We also found that the STAT3 signal was activated in myocardial tissue after cervical sympathectomy. STAT3 inhibitor can partially reverse the myocardial protective effect of cervical sympathectomy.

Conclusion

Bilateral superior cervical sympathectomy significantly alleviated myocardial I/R injury in mice. And activation of the STAT3 signal may play an essential role in this.

Complementary Role of Oxytocin and Vasopressin in Cardiovascular Regulation

The neurons secreting oxytocin (OXY) and vasopressin (AVP) are located mainly in the supraoptic, paraventricular, and suprachiasmatic nucleus of the brain. Oxytocinergic and vasopressinergic projections reach several regions of the brain and the spinal cord. Both peptides are released from axons, soma, and dendrites and modulate the excitability of other neuroregulatory pathways. The synthesis and action of OXY and AVP in the peripheral organs (eye, heart, gastrointestinal system) is being investigated. The secretion of OXY and AVP is influenced by changes in body fluid osmolality, blood volume, blood pressure, hypoxia, and stress. Vasopressin interacts with three subtypes of receptors: V1aR, V1bR, and V2R whereas oxytocin activates its own OXTR and V1aR receptors. AVP and OXY receptors are present in several regions of the brain (cortex, hypothalamus, pons, medulla, and cerebellum) and in the peripheral organs (heart, lungs, carotid bodies, kidneys, adrenal glands, pancreas, gastrointestinal tract, ovaries, uterus, thymus). Hypertension, myocardial infarction, and coexisting factors, such as pain and stress, have a significant impact on the secretion of oxytocin and vasopressin and on the expression of their receptors. The inappropriate regulation of oxytocin and vasopressin secretion during ischemia, hypoxia/hypercapnia, inflammation, pain, and stress may play a significant role in the pathogenesis of cardiovascular diseases.

Residual heart rate variability measures can better differentiate patients with acute myocardial infarction from patients with patent coronary artery

Purpose

It has been shown that the power spectral density (PSD) of heart rate variability (HRV) can be decomposed into a power-law function and a residual PSD (rPSD) with a more prominent high-frequency component than that in traditional PSD. This study investigated whether the residual HRV (rHRV) measures can better discriminate patients with acute myocardial infarction (AMI) from patients with patent coronary artery (PCA) than traditional HRV measures.

Materials and methods

The rHRV and HRV measures of 48 patients with AMI and 69 patients with PCA were compared.

Results

The high-frequency power of rHRV spectrum was significantly enhanced while the low-frequency and very low-frequency powers of rHRV spectrum were significantly suppressed, as compared to their corresponding traditional HRV spectrum in both groups of patients. The normalized residual high-frequency power (nrHFP = residual high-frequency power/residual total power) was significantly greater than the corresponding normalized high-frequency power in both groups of patients. Between-groups comparison showed that the nrHFP in AMI patients was significantly smaller than that in PCA patients. Receiver operating characteristic curve analysis showed that the nrHFP or nrHFP + normalized residual very low-frequency power (residual very low-frequency power/rTP) had better discrimination capability than the corresponding HRV measures for predicting AMI.

Conclusions

Compared with traditional HRV measures, the rHRV measures can slightly better differentiate AMI patients from PCA patients, especially the nrHFP or nrHFP + normalized residual very low-frequency power.

Temporal profile and mechanisms of the prompt sympathoexcitation following coronary ligation in Wistar rats

Our aim was to assess the timing and mechanisms of the sympathoexcitation that occurs immediately after coronary ligation. We recorded thoracic sympathetic (tSNA) and phrenic activities, heart rate (HR) and perfusion pressure in Wistar rats subjected to either ligation of the left anterior descending coronary artery (LAD) or Sham operated in the working heart-brainstem preparation. Thirty minutes after LAD ligation, tSNA had increased (basal: 2.5±0.2 µV, 30 min: 3.5±0.3 µV), being even higher at 60 min (5.2±0.5 µV, P<0.01); while no change was observed in Sham animals. HR increased significantly 45 min after LAD (P<0.01). Sixty minutes after LAD ligation, there was: (i) an augmented peripheral chemoreflex - greater sympathoexcitatory response (50, 45 and 27% of increase to 25, 50 and 75 µL injections of NaCN 0.03%, respectively, when compared to Sham, P<0.01); (ii) an elevated pressor response (32±1 versus 23±1 mmHg in Sham, P<0.01) and a reduced baroreflex sympathetic gain (1.3±0.1 versus Sham 2.0±0.1%.mmHg-1, P<0.01) to phenylephrine injection; (iii) an elevated cardiac sympathetic tone (ΔHR after atenolol: -108±8 versus -82±7 bpm in Sham, P<0.05). In contrast, no changes were observed in cardiac vagal tone and bradycardic response to both baroreflex and chemoreflex between LAD and Sham groups. The immediate sympathoexcitatory response in LAD rats was dependent on an excitatory spinal sympathetic cardiocardiac reflex, whereas at 3 h an angiotensin II type 1 receptor mechanism was essential since Losartan curbed the response by 34% relative to LAD rats administered saline (P<0.05). A spinal reflex appears key to the immediate sympathoexcitatory response after coronary ligation. Therefore, the sympathoexcitatory response seems to be maintained by an angiotensinergic mechanism and concomitant augmentation of sympathoexcitatory reflexes.

The spleen in local and systemic regulation of immunity

The spleen is the main filter for blood-borne pathogens and antigens, as well as a key organ for iron metabolism and erythrocyte homeostasis. Also, immune and hematopoietic functions have been recently unveiled for the mouse spleen, suggesting additional roles for this secondary lymphoid organ. Here we discuss the integration of the spleen in the regulation of immune responses locally and in the whole body and present the relevance of findings for our understanding of inflammatory and degenerative diseases and their treatments. We consider whether equivalent activities in humans are known, as well as initial therapeutic attempts to target the spleen for modulating innate and adaptive immunity.

Angiotensin II drives the production of tumor-promoting macrophages

Macrophages frequently infiltrate tumors and can enhance cancer growth, yet the origins of the macrophage response are not well understood. Here we address molecular mechanisms of macrophage production in a conditional mouse model of lung adenocarcinoma. We report that overproduction of the peptide hormone Angiotensin II (AngII) in tumor-bearing mice amplifies self-renewing hematopoietic stem cells (HSCs) and macrophage progenitors. The process occurred in the spleen but not the bone marrow, and was independent of hemodynamic changes. The effects of AngII required direct hormone ligation on HSCs, depended on S1P(1) signaling, and allowed the extramedullary tissue to supply new tumor-associated macrophages throughout cancer progression. Conversely, blocking AngII production prevented cancer-induced HSC and macrophage progenitor amplification and thus restrained the macrophage response at its source. These findings indicate that AngII acts upstream of a potent macrophage amplification program and that tumors can remotely exploit the hormone's pathway to stimulate cancer-promoting immunity.

RU28318, an aldosterone antagonist, in combination with an ACE inhibitor and angiotensin receptor blocker attenuates cardiac dysfunction in diabetes

AIMS

We evaluated the effects of RU28318 (RU), a selective mineralocorticoid receptor (MR) antagonist, Captopril (Capt), an angiotensin converting enzyme inhibitor, and Losartan (Los), an angiotensin receptor blocker, alone or in combination with ischemia/reperfusion- (I/R-) induced cardiac dysfunction in hearts obtained from normal and diabetic rats.

METHODS

Isolated hearts were perfused for 30 min and then subjected to 30 min of global ischemia (I) followed by a period of 30 min of reperfusion (R). Drugs were administered for 30 min either before or after ischemia. Drug regimens tested were RU, Capt, Los, RU + Capt, RU + Los, Capt + Los, and RU + Capt + Los (Triple). Recovery of cardiac hemodynamics was evaluated.

RESULTS

Recovery of cardiac function was up to 5-fold worse in hearts obtained from diabetic animals compared to controls. Treatment with RU was generally better in preventing or reversing ischemia-induced cardiac dysfunction in normal hearts compared to treatment with Capt or Los alone. In diabetic hearts, RU was generally similarly effective as Capt or Los treatment.

CONCLUSIONS

RU treatment locally might be considered as an effective therapy or preventative measure in cardiac I/R injury. Importantly, RU was the most effective at improving -dP/dt (a measure of diastolic function) when administered to diabetic hearts after ischemia.

Effects of Long-Term Exercise Training on Autonomic Control in Myocardial Infarction Patients

Autonomic dysfunction, including baroreceptor attenuation and sympathetic activation, has been reported in patients with myocardial infarction (MI) and has been associated with increased mortality. We tested the hypotheses that exercise training (ET) in post-MI patients would normalize arterial baroreflex sensitivity (BRS) and muscle sympathetic nerve activity (MSNA), and long-term ET would maintain the benefits in BRS and MSNA. Twenty-eight patients after 1 month of uncomplicated MI were randomly assigned to 2 groups, ET (MI-ET) and untrained. A normal control group was also studied. ET consisted of three 60-minute exercise sessions per week for 6 months. We evaluated MSNA (microneurography), blood pressure (automatic oscillometric method), heart rate (ECG), and spectral analysis of RR interval, systolic arterial pressure (SAP), and MSNA. Baroreflex gain of SAP-RR interval and SAP-MSNA were calculated using the α-index. At 3 to 5 days and 1 month after MI, MSNA and low-frequency SAP were significantly higher and BRS significantly lower in MI patients when compared with the normal control group. ET significantly decreased MSNA (bursts per 100 heartbeats) and the low-frequency component of SAP and significantly increased the low-frequency component of MSNA and BRS of the RR interval and MSNA. These changes were so marked that the differences between patients with MI and the normal control group were no longer observed after ET. MSNA and BRS in the MI-untrained group did not change from baseline over the same time period. ET normalizes BRS, low-frequency SAP, and MSNA in patients with MI. These improvements in autonomic control are maintained by long-term ET. These findings highlight the clinical importance of this nonpharmacological therapy based on ET in the long-term treatment of patients with MI.

Identification of splenic reservoir monocytes and their deployment to inflammatory sites

A current paradigm states that monocytes circulate freely and patrol blood vessels but differentiate irreversibly into dendritic cells (DCs) or macrophages upon tissue entry. Here we show that bona fide undifferentiated monocytes reside in the spleen and outnumber their equivalents in circulation. The reservoir monocytes assemble in clusters in the cords of the subcapsular red pulp and are distinct from macrophages and DCs. In response to ischemic myocardial injury, splenic monocytes increase their motility, exit the spleen en masse, accumulate in injured tissue, and participate in wound healing. These observations uncover a role for the spleen as a site for storage and rapid deployment of monocytes and identify splenic monocytes as a resource that the body exploits to regulate inflammation.

Sympathomimetic inefficiency in restoring contractility in the acute or chronic beta-blocker-treated ischaemic heart: comparison with a new agent

BACKGROUND

Adequate pharmacologic cardiac support in acute myocardial infarction (MI), as well as in chronic MI patients under beta-blocker therapy, is problematic due to the impaired cardiac response to beta-adrenergic agonists. New therapeutic approaches could resolve this problem. Istaroxime (ISTA) is a new Na(+),K(+)-ATPase inhibitor and SERCA(2) agonist.

AIMS

To evaluate: 1) the effects of dobutamine (DOB) on left ventricular function in early (48-72 h) and late (14 days) phases of a post-MI canine model, compared to ISTA, and 2) the efficacy of DOB in chronic left ventricular dysfunction (6 months post-MI) in dogs pre-treated or not with a beta-blocker, compared with ISTA and milrinone (MIL).

RESULTS

When compared to the effects in healthy animals, DOB increased contractility only slightly in the first 48-72 h post-MI, whereas its efficacy recovered partially by day 14 and fully by 6 months after MI. ISTA had a greater effect on contractility than DOB and improved relaxation, while DOB did not. Moreover, beta-adrenergic blockade inhibited the inotropic action of DOB, without altering the effect of ISTA. Surprisingly, beta-adrenergic blockade blunted the effects of MIL.

CONCLUSION

ISTA may represent a novel strategy for enhancing left ventricular performance even in the context of acute MI and/or concomitant beta-adrenergic blockade.

Skin blood flow and its oscillatory components in patients with acute myocardial infarction

BACKGROUND/AIMS

Laser Doppler flowmetry (LDF) was used to determine the influence of acute myocardial infarction (AMI) and of successful reperfusion treatment on basal skin blood flow and its oscillatory components.

METHODS

Skin LDF was performed on all extremities in 58 patients 4-9 days after AMI (Killip class I), and in 71 healthy age- and sex-matched controls. Wavelet analysis was applied to evaluate oscillatory components within the interval 0.005-2 Hz.

RESULTS

AMI patients had reduced mean flow (p < 0.01) and oscillatory components (p < 0.04) in all extremities. Reperfused (n = 40), compared to nonreperfused (n = 18), patients had higher mean flow and total spectral amplitude at all recording points. The difference was statistically significant only in legs (group median LDF in the left leg was 9.68 AU for reperfused and 5.71 AU for nonreperfused patients, p < 0.04, and 11.47 and 4.24 AU in the right leg, p < 0.01). Reperfused patients had significantly higher total spectral amplitude in both legs (p < 0.04).

CONCLUSIONS

In AMI patients, reduced skin blood flow and its oscillatory components may reflect ongoing neurohumoral activation despite absence of clinically apparent heart failure. The reduction of blood flow and its oscillatory components was larger in nonreperfused AMI patients, although they had a comparable left ventricular function.

Association of high levels of plasma free dopamine with future coronary events in patients with coronary artery disease

BACKGROUND

There is an intimate relationship between activation of the sympathetic nervous system and myocardial ischemia. This study examined whether plasma levels of dopamine, a precursor of norepinephrine, may provide prognostic information in coronary artery disease (CAD).

METHODS AND RESULTS

Plasma levels of free dopamine were measured by high-performance liquid chromatography in 210 consecutive patients with stable CAD. The patients were prospectively followed up for a period of < or =36 months until occurrence of a clinical coronary event. Coronary events occurred in 37 patients during follow-up. In Kaplan-Meier survival analysis, higher dopamine levels (> or =30 pg/ml) resulted in a higher event probability (p<0.01). Multivariate Cox hazards analysis showed that higher dopamine levels were a significant and independent risk factor for future coronary events (hazard ratio 3.3, 95% confidence interval 1.3-8.1, p<0.01). Furthermore, patients with higher dopamine levels had lower left ventricular (LV) ejection fraction and higher levels of brain natriuretic peptide, C-reactive protein, and fibrinogen than those with lower dopamine levels.

CONCLUSIONS

Plasma levels of free dopamine are increased in association with a decrease in LV function and an increase in inflammatory risk markers. Higher free dopamine levels are an independent risk factor for future coronary events in CAD patients.

The antioxidative effects of long-term treatment are more pronounced for carvedilol than for atenolol in post-myocardial infarction patients

Oxidative stress might exert deleterious cardiovascular effects. The aim of the present study was to compare the antioxidative effects of carvedilol and atenolol. Levels of oxidized low-density lipoprotein cholesterol (ox-LDL), vitamin E, and thiobarbituric acid reactive substances (TBARS) were measured. In a prospective, open, and end-point-blinded study, 232 patients with an acute myocardial infarction (AMI) were randomized to receive either carvedilol or atenolol at equipotent doses, and the previously mentioned 3 parameters were measured at baseline and after 12 months of active treatment, with changes during the study period being compared both within and between the groups. Ox-LDL decreased in both treatment modalities, from 40.5 +/- 15.6 to 35.0 +/- 13.8 U/L, P = 0.0001, in the carvedilol group and from 40.3 +/- 16.5 to 37.4 +/- 13.1 U/L, P = 0.044, in the atenolol group, with a significant between-group difference in the changes (P = 0.036). The levels of vitamin E did not change during carvedilol treatment (31.0 +/- 10.2 vs 31.7 +/- 11.1 micromol/L), but it decreased marginally in the atenolol group (30.8 +/- 12.1 vs 27.2 +/- 9.1 micromol/L, P = 0.056), with a significant between-group difference (P = 0.008). No significant change in TBARS was observed between the carvedilol and atenolol groups (P = 0.454). These results indicate that carvedilol has a more pronounced antioxidative effect than atenolol in post-AMI patients, which might be of clinical importance.

High plasma aldosterone levels on admission are associated with death in patients presenting with acute ST-elevation myocardial infarction

BACKGROUND

Aldosterone, the final mediator of the renin-angiotensin-aldosterone pathway, is at its highest plasma levels at presentation for ST-elevation myocardial infarction (STEMI). Whether aldosterone level at presentation for STEMI is associated with adverse outcome remains unknown.

METHODS AND RESULTS

Plasma aldosterone levels were measured at presentation in consecutive patients referred for primary percutaneous coronary intervention for STEMI. We assessed the association between aldosterone levels and in-hospital events and mortality during a 6-month follow-up. Of 356 STEMI patients, 23 and 36 died during the hospital stay and 6-month follow-up period, respectively. Nine other patients survived in-hospital cardiac arrest. High aldosterone levels were associated with an almost stepwise increase in rates of in-hospital death (P=0.01), cardiovascular death (P=0.03), heart failure (P=0.005), ventricular fibrillation (P=0.02), and resuscitated cardiac arrest (P=0.01). After adjustment for age, Killip class, and reperfusion status, compared with patients in the first aldosterone quartile group, those in the highest quartile were at higher risk of death (hazard ratio 3.28, 95% CI 1.09 to 9.89, P=0.035) and death or resuscitated cardiac arrest (hazard ratio 3.74, 95% CI 1.40 to 9.98, P=0.008) during the follow-up.

CONCLUSIONS

Plasma aldosterone levels on admission among patients referred for primary percutaneous coronary intervention for STEMI are associated with early and late adverse clinical outcomes, including mortality. The association between high aldosterone levels and late mortality is independent of age, heart failure, and reperfusion status. Such results underline the pivotal role of aldosterone and justify a randomized trial to assess the early administration of aldosterone antagonists in the setting of STEMI.

Addition of an angiotensin receptor blocker to full-dose ACE-inhibition: controversial or common sense?

Both angiotensin-converting enzyme (ACE)-inhibitors and angiotensin receptor blockers (ARBs) interfere with the activity of the renin-angiotensin system (RAS) in a different way. Theoretically, one might expect beneficial effects when they are used in combination, as a more complete suppression of the RAS can be achieved. But can this additional effect still be seen in patients on full-dose ACE-inhibition? Several controlled trials demonstrated that combination therapy can have additional benefits in hypertensive patients, in chronic heart failure patients, and in both diabetic and non-diabetic nephropathy patients. However, the clinical benefit was not always as pronounced as expected and not every patient will benefit from dual blockade of the RAS. There is some evidence of a less pronounced effect of combination therapy when a full dose of the ACE-inhibitor is given. However, it is well known that ACE-inhibitors cannot completely suppress the formation of angiotensin II, in particular, when the RAS is activated. Indeed, clinical trials indicated that add-on therapy with an ARB was especially of use when the RAS remained activated despite full-dose ACE-inhibitor treatment. In summary, combination of a full-dose ACE-inhibitor and an ARB can be a rational choice in selected patients.

Predictors of mortality in patients with acute myocardial infarction and cardiogenic shock

BACKGROUND

Although cardiogenic shock (CS) is the leading cause of death for acute myocardial infarction (AMI) patients, reliable predictive factors in the acute stage, such as cardiovascular peptides, have not yet been identified.

METHODS AND RESULTS

In 42 consecutive AMI patients with CS on admission, successfully treated by primary percutaneous coronary intervention (PCI) within 12 h of onset, related factors including brain natriuretic peptide (BNP), atrial natriuretic peptide (ANP), renin, aldosterone, catecholamines, and adrenomedullin, were investigated 24 h from onset, as well as the 1-year mortality rates. During the 12-month follow-up period, 15 patients died from cardiovascular causes (group D). There were no significant differences in patient characteristics, angiographic findings, and left ventricular systolic function between group D subjects and the survivors (group S: n=27). Multivariate analysis identified high levels of adrenomedullin as an independent predictor of 1-year mortality (risk ratio: 6.42, 95% confidence interval, 1.49-43.31, p<0.05).

CONCLUSIONS

The acute-phase plasma concentration of adrenomedullin may be a reliable predictor of mortality in patients with AMI complicated by CS and successfully treated by direct PCI, as may be BNP concentration, peak-creatine kinase value, and ventricular fibrillation.

Evaluation of neurohumoral activation (adrenomedullin, BNP, catecholamines, etc.) in patients with acute myocardial infarction

OBJECTIVE

The object of our study was to identify the most useful predictor of patient prognosis in acute myocardial infarction (AMI), from 7 acute-phase cardiovascular peptides which take part in neurohumoral activation [brain natriuretic peptide (BNP), atrial natriuretic peptide (ANP), renin, aldosterone, adrenomedullin, epinephrine and norepinephrine].

METHODS

In 141 consecutive AMI patients, 24 hours from onset, we evaluated plasma concentration levels of the 7 types of cardiovascular peptides and the relationships between the values of these peptides and short-term clinical prognosis, including mortality.

RESULTS

Plasma levels of all cardiovascular peptides were significantly higher in patients who suffered mortality than in surviving patients (BNP: 1,267+/-997 pg/ml vs. 293+/-327 pg/ml, p<0.0001; ANP: 164+/-186 pg/ml vs. 64+/-76 pg/ml, p<0.001; adrenomedullin: 13.61+/-3.29 Fmol/l vs. 3.45+/-1.52 Fmol/I, p<0.0001; renin: 8.79+/-7.15 ng/ml/h vs. 4.34+/-5.10 ng/ml/h, p<0.01; aldosterone: 249+/-210 pg/ml vs. 68+/-74 pg/ml, p<0.0001; epinephrine: 3,191+/-8,360 pg/ml vs. 68+/-74 pg/ml, p<0.0001; norepinephrine: 21.8+/-46.2 ng/ml vs. 0.9+/-0.8, ng/ml p<0.0001). Multivariate analysis identified only high levels of adrenomedullin as an independent related factor of cardiogenic shock (risk ratio: 5.84, 95% C.I.: 1.80-18.95, p=0.003), and as an independent predictor of short-term mortality (risk ratio: 16.16, 95% C.I.: 1.38-189.71, p=0.03).

CONCLUSIONS

Acute-phase neurohumoral activation, involving renin, aldosterone, epinephrine, norepinephrine, BNP, ANP, and adrenomedullin may be closely related to poor patient outcomes, including mortality. Our results suggest that acute-phase plasma adrenomedullin concentrations may be the most useful predictor of patient prognosis in the setting of AMI, out of the 7 types of cardiovascular peptides involved in neurohumoral activation.

Sympathetic Drive in Anterior and Inferior Uncomplicated Acute Myocardial Infarction

Background— The sympathetic activation that follows acute myocardial infarction (AMI) has been associated with increased morbidity and mortality. Because the prognosis after anterior AMI (ant-AMI) is worse than that after inferior AMI (inf-AMI), we planned to determine whether the magnitude of sympathetic hyperactivity differs between the two.

Methods and Results— Thirty-nine patients with uncomplicated AMI, comprising 2 matched groups of 17 patients with ant-AMI, and 22 patients with inf-AMI were examined. Measurements were obtained 2 to 4 days after AMI and compared with 20 normal subjects (NC) who were matched in terms of age and body weight to the AMI groups. Resting muscle sympathetic nerve activity was quantified from multiunit bursts (MSNA) and from single units (s-MSNA). Both groups of AMI patients were matched with regard to hemodynamic variables, left ventricular function, and infarct size. Both groups had greater (at least P <0.01) sympathetic nerve activity than NC (60±4.3 bursts/100 cardiac beats and 68±4.9 impulses/100 cardiac beats), but the magnitude of sympathetic nerve hyperactivity in ant-AMI (81±4.0 bursts/100 cardiac beats and 91±4.9 impulses/100 cardiac beats) was similar ( P >0.05) to that in inf-AMI (80±3.2 bursts/100 cardiac beats and 90±4.0 impulses/100 cardiac beats)

Conclusions— Both ant-AMI and inf-AMI resulted primarily in a similar magnitude of sympathetic nerve hyperactivity. These findings suggest that the worse prognosis after ant-AMI compared with after inf-AMI would not be related primarily to the degree of sympathetic hyperactivity.

Time course of sympathetic neural hyperactivity after uncomplicated acute myocardial infarction

BACKGROUND

Little information is available on sympathetic activity after acute myocardial infarction (AMI), despite the belief that sympathetic drive is important in relation to morbidity and mortality. Indirect indices such as plasma catecholamines are transiently elevated after uncomplicated AMI, whereas other prognostically important autonomic indices may be affected longer. We planned to quantify central sympathetic output to the periphery after uncomplicated AMI and to investigate its progress over time.

METHODS AND RESULTS

After uncomplicated AMI, 13 patients had muscle sympathetic nerve activity (MSNA) assessed from multiunit discharges and from single units with defined vasoconstrictor properties (s-MSNA). Measurements were obtained 2 to 4 days after AMI and were repeated after 3 and 6 months. We also examined 3 matched control groups comprising normal subjects, patients with coronary artery disease, and hospitalized patients without AMI. MSNA and s-MSNA after AMI (84+/-4.6 bursts/100 beats and 95+/-5.8 impulses/100 beats) were unchanged at 3 months but decreased (P<0.01 and P<0.001) after 6 months (75+/-4.0 bursts/100 beats and 80+/-4.4 impulses/100 beats). These were still greater (at least P<0.01) than values in normal subjects, patients with coronary artery disease, and hospitalized patients without AMI (51+/-3.9 bursts/100 beats, 58+/-4.7 impulses/100 beats; 56+/-2.2 bursts/100 beats, 61+/-2.2 impulses/100 beats; and 55+/-3.6 bursts/100 beats, 61+/-3.3 impulses/100 beats, respectively). This sympathetic hyperactivity was inversely correlated to left ventricular ejection fraction but not to changes in blood pressure.

CONCLUSIONS

A protracted state of sympathetic hyperactivity was shown to occur after uncomplicated AMI. It is suggested that this hyperactivity may explain delayed cardiovascular morbidity and mortality and that it arises because of an impairment of reflexes from cardiac receptors.

Angiotensin II as a cardiovascular risk factor

A renin-angiotensin level that is inappropriately high for the systemic blood pressure and the state of sodium balance is now recognized to be one of the modifiable cardiovascular risk factors. Angiotensin acts both as a circulating hormone and as a locally acting paracrine/autocrine/intracrine factor. The adverse effects of angiotensin on the heart include the mechanical results of elevated resistance to the pumping function of the myocardium, as well as the effects of neurohumoral abnormalities on various cardiac structures. In addition, cardiac damage follows acute ischaemic injury or chronic energy starvation due to coronary artery disease, attributable to either mechanical obstruction (atherosclerotic and/or thrombotic) or functional stenosis (vasospasm). Activation of the renin-angiotensin system has several haemodynamic and humoral consequences, all of which may damage the myocardium. These include acute myocardial ischaemia, left-ventricular hypertrophy, arrhythmias, alterations in the coagulation-fibrinolysis equilibrium, increased oxidative stress, and pro-inflammatory activity. A brief review of some of the mechanisms by which activation of the renin-angiotensin system can inflict damage on the heart is presented.

Effects of an HMG-CoA reductase inhibitor in combination with an ACE inhibitor or angiotensin II type 1 receptor antagonist on myocardial metabolism in ischemic rabbit hearts

We investigated the effects of a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, pravastatin, an angiotensin converting enzyme (ACE) inhibitor, temocaprilat, and an angiotensin II type 1 (AT1) receptor antagonist, CV-11974, on myocardial metabolism during ischemia in isolated rabbit hearts using phosphorus 31-nuclear magnetic resonance (31P-NMR) imaging. Forty-five minutes of continuous normothermic global ischemia was carried out. Pravastatin, temocaprilat, CV-11974 or a nitric oxide synthase inhibitor, L-NAME was administered from 60 min prior to the global ischemia. Japanese white rabbits were divided into the following experimental groups, a control group (n=7), a group treated with pravastatin (P group; n=7), a group treated with pravastatin and temocaprilat (P+T group; n=7), a group treated with pravastatin and CV-11974 (P+CV group; n=7), and a group treated with pravastatin and L-NAME (P+L-NAME group; n=7). During ischemia, P group, as well as either P+T group or P+CV group, showed a significant inhibition of the decreases in adenosine triphosphate (ATP) and intracellular pH (pHi) (p<0.01, respectively, at the end of ischemia compared to the control group as well as P+L-NAME group), and a significant inhibition of the increase in inorganic phosphate (Pi) (p<0.01, respectively, compared with the control group as well as P+L-NAME group). These results suggest that pravastatin significantly improved myocardial energy metabolism during myocardial ischemia. This beneficial effect was dependent on NO synthase. However, this beneficial effect was not enhanced by either temocaprilat or CV-11974.

Vascular and renal effects of vasopressin and its antagonists in conscious rats with chronic myocardial infarction; evidence for receptor shift

Acute myocardial infarction evokes activation of, among others, the arginine-vasopressin system, resulting in vasoconstriction and fluid retention. In the present study, the vasoconstrictor and antidiuretic effects of vasopressin were examined in vivo in conscious rats with chronic myocardial infarction, in the absence or presence of the V(1a) receptor antagonist SR-49059 or the V(2) receptor antagonist OPC-31260. In sham rats, vasopressin dose-dependently increased mean arterial pressure (maximum response: 45+/-3 mm Hg), which was significantly suppressed in infarcted rats (maximum response: 32+/-3 mm Hg). SR-49059, but not OPC-31260, caused a significant rightward shift of the dose pressure response curve in sham rats, indicating V(1a) receptor mediation. This rightward shift by SR-49059 was significantly more in infarcted rats. The suppressed response to the agonist and enhanced sensitivity to the antagonist suggest a reduction of V(1a) receptor number in infarcted rats. In both sham and infarcted rats, the urine production after OPC-31260 (337+/-14 and 329+/-30 microl/min, respectively) was about twice of that in vehicle-treated rats (188+/-25 and 155+/-24 microl/min, respectively). However, the response in infarcted rats reached its peak quicker and lasted for a shorter period, resulting in a 40% lower area under the curve. Although only measurable during V(2) receptor blockade, the reduction of urine production by vasopressin was significantly more in infarcted compared to sham rats. The enhanced renal response to the agonist and reduced response to the antagonist suggest an increase in V(2) receptor number in infarcted rats. In conclusion, in chronically infarcted rats, vasopressin causes vasoconstriction and fluid retention through the V(1a) and V(2) receptors, respectively. Altered responses after infarction indicate a shift from V(1a) to V(2) receptors.

Cardioprotection with angiotensin converting enzyme inhibitor and angiotensin II type 1 receptor antagonist is not abolished by nitric oxide synthase inhibitor in ischemia-reperfused rabbit hearts

Although angiotensin converting enzyme (ACE) inhibitor and/or angiotensin II type 1 (AT1) receptor antagonist can protect the myocardium against ischemia-reperfusion injury, the mechanisms of the effect have not yet been characterized at the cellular level. We here examined the effect of the combination of an ACE inhibitor, temocaprilat, an AT1 receptor antagonist, CV-11974 and/or a nitric oxide synthase inhibitor, L-NAME, on the myocardial metabolism and contraction during ischemia and reperfusion by using phosphorus 31-nuclear magnetic resonance (31P-NMR) in Langendorff rabbit hearts. After normothermic 20 min global ischemia, postischemic reperfusion of 30 min was carried out. Twenty-one hearts were divided into three experimental groups consisting of 7 hearts each: a Tem+CV group perfused with a combination of temocaprilat and CV-11974; a Tem+CV+L-NAME group perfused with a combination of temocaprilat and CV-11974 plus L-NAME, and a control group. During ischemia, both the Tem+CV group and Tem+CV+L-NAME group showed a significant inhibition of the decrease in adenosine triphosphate (ATP) compared with the control group (p<0.01); the increase in ATP was 50+/-3%, 42+/-4%, and 19+/-4% in the Tem+CV group, Tem+CV+L-NAME group, and control group, respectively. Both experimental groups also showed a significant inhibition of the increase in left ventricular end-diastolic pressure (LVEDP) compared with the control group (p<0.01). After postischemic reperfusion, the Tem+CV group and Tem+CV+L-NAME group again showed a significant improvement of ATP as compared with the control group (p<0.01); the increase in ATP was 73+/-3%, 64+/-3%, and 47+/-4% in the Tem+CV group, Tem+CV+L-NAME group, and control group, respectively, and a significant decrease of LVEDP as compared with the control group (p<0.01). There were no differences in ATP, or LVEDP during ischemia and reperfusion between the Tem+CV group and Tem+CV+ L-NAME group. In conclusion, the combination of temocaprilat and CV-11974 showed significant potential for improving myocardial energy metabolism and relaxation during both myocardial ischemia and reperfusion. This beneficial effect was not dependent on NO synthase.

Modulation of oxidative stress by a selective inhibition of angiotensin II type 1 receptors in MI rats

OBJECTIVES

To examine whether blocking of the renin-angiotensin system (RAS) at the angiotensin II type 1 (AT1) receptor site is accompanied by changes in the oxidative stress parameters.

BACKGROUND

Congestive heart failure in rats after myocardial infarction (MI) has been shown to correlate with a decrease in antioxidant enzyme activities and an increase in oxidative stress. Inhibition of the RAS with captopril improves cardiac function and survival in MI rats with a reduction in oxidative stress.

METHODS

Myocardial infarction in rats was produced by ligation of the left coronary artery. At four weeks after surgery, animals from the sham as well as MI groups were treated with losartan (2 mg/ml in drinking water daily). At 16 weeks after surgery, the animals were examined for hemodynamic function and the hearts were analyzed for antioxidant enzyme activities (superoxide dismutase, glutathione peroxidase and catalase) and oxidative stress (lipid hydroperoxides, reduced and oxidized glutathione and redox ratio).

RESULTS

Congestive heart failure was characterized by dyspnea, depressed hemodynamic function and presence of lung and liver congestion. This was also associated with a decrease in the myocardial catalase (-25%), glutathione peroxidase (-38%) and superoxide dismutase (-42%) activities. An increase in oxidative stress in these hearts was indicated by an increase in lipid hydroperoxides (+67%) and reduction in the redox ratio (-75%). Hemodynamic function was better maintained and there were no indications of dyspnea or lung or liver congestion in the losartan-treated MI rats. In these animals, myocardial oxidative stress was markedly reduced and glutathione peroxidase and catalase activities were significantly improved compared with the untreated MI group.

CONCLUSIONS

Blocking of RAS at the AT1 receptor site without the inhibition of angiotensin-converting enzymes modulates heart failure after MI, and this beneficial effect is associated with a decrease in oxidative stress. This study suggests a newer role for losartan in the treatment of heart failure.

Role of Cardiac ATP-Sensitive K+ Channels Induced by Angiotensin II Type 1 Receptor Antagonist on Metabolism, Contraction and Relaxation in Ischemia-Reperfused Rabbit Heart

The role of cardiac adenosine triphosphate-sensitive K+ (K(ATP)) channels induced by angiotensin II type 1 (AT1) receptor antagonist, CV-11974, on myocardial metabolism and contraction during ischemia, and reperfusion by the phosphorus 31-nuclear magnetic resonance in Langendorff-perfused rabbit hearts was investigated. After 20 min of continuous normothermic global ischemia, 30 min of postischemic reperfusion was carried out. CV-11974 with or without the K(ATP) channel blocker, glibenclamide, or the bradykinin B2 receptor antagonist, D-Arg-[Hyp3,D-Phe7]bradykinin, was administered 40 min prior to the global ischemia. Adenosine triphosphate (ATP), creatine phosphate (PCr), inorganic phosphate (Pi), intracellular pH (pHi), left ventricular systolic developed pressure, left ventricular end-diastolic pressure (LVEDP), and coronary flow were measured. Twenty-eight hearts were divided into 4 experimental groups consisting of 7 hearts each. Group I consisted of controls, Group II perfused with CV-11974 (10(-6) mol/L), Group III perfused with CV-11974 (10(-6) mol/L) in combination with glibenclamide (10(-6) mol/L), and Group IV perfused with CV-11974 (10(-6) mol/L) in combination with D-Arg-[Hyp3,D-Phe7]bradykinin (10(-6) mol/L). Group II showed a significant inhibition of the decrease in ATP during ischemia and reperfusion compared with Group I (p<0.01), being 42+/-3% and 19+/-4% at ischemia, 69+/-3% and 47+/-4% at reperfusion in Group II and Group I, respectively. Group II also showed a significant inhibition of the increase in LVEDP during ischemia and reperfusion compared with Group I (p<0.01), being 13+/-4 mmHg and 52+/-8 mmHg at ischemia, 8+/-2 mmHg and 26+/-5 mmHg at reperfusion in Group II and Group I, respectively. However, Group II did not inhibit the decrease in ATP and the increase in LVEDP during ischemia and reperfusion. Group IV also showed no inhibition of the aforementioned parameters during the same period. These results suggest that CV-11974 has a significant beneficial effect for improving myocardial energy metabolism and relaxation during both myocardial ischemia and reperfusion, which is provided by K(ATP) channels and bradykinin B2 receptor. The cardioprotective quality of the AT1 receptor antagonist is caused by the K(ATP) channels that are mediated by the bradykinin B2 receptor.

[Arg8]-vasopressin-induced responses on coronary and mesenteric arteries of rats with myocardial infarction: the effects of V1a- and V2-receptor antagonists

After myocardial infarction, plasma levels of [Arg8]-vasopressin rise to recover hemodynamics. The vascular responses to [Arg8]-vasopressin were studied in vitro in isolated hearts and mesenteric artery segments of rats with 1-day and 3-week-old infarcts, in absence and presence of the V1a-receptor antagonist SR-49059 and the V2-receptor antagonist OPC-31260. Vascular responses of coronary arteries were similar in sham and infarcted hearts. On average, coronary flow was maximally decreased by 70 +/- 3% from baseline values of 11.1 +/- 0.3 ml/min, with pD2 values of 10.52 +/- 0.05. In mesenteric artery segments of sham and infarcted rats, maximal contractile forces, expressed as percentage of contraction to 125 mM KCl, were similar (232 +/- 23% and 239 +/- 8%, respectively). However, pD2 values from infarcted rats (9.22 +/- 0.07) were significantly lower compared with sham (9.55 +/- 0.07) rats. In coronary as well as mesenteric vessels, the vasoconstrictor responses, being more susceptible to SR-49059 (apparent pA2, between 9.12 and 9.82) than to OPC-31260 (apparent pA2, between 6.21 and 6.92), seemed mediated by the V1a receptor. These data indicate that in mesenteric but not in coronary vessels, an altered responsiveness to vasopressin could be observed. Responses are mediated mainly by the V1a receptor.

Effect of angiotensin converting enzyme inhibitor and angiotensin II type 1 receptor antagonist on metabolism and contraction in ischemia-reperfused rabbit heart

The effect of angiotensin converting enzyme (ACE) inhibitor, temocaprilat and/or angiotensin II type 1 (AT1) receptor antagonist, CV-11974 on myocardial metabolism and contraction during ischemia and reperfusion was examined by phosphorus 31-nuclear magnetic resonance (31P-NMR) in Langendorff rabbit hearts. After normothermic 15 min global ischemia, postischemic reperfusion of 60min was carried out. Temocaprilat and/or CV-11974 were administered from 40 min prior to the global ischemia. Adenosine triphosphate (ATP), creatine phosphate (PCr), inorganic phosphate (Pi), intracellular pH (pHi), left ventricular developed pressure (LVDevP), left ventricular end-diastolic pressure (LVEDP) and coronary flow were measured. Twenty-eight hearts were divided into 4 experimental groups consisting of 7 hearts each: group I consisted of controls, group II was perfused with temocaprilat (10(-6)mol/L), group III was perfused with CV-11974 (10(-6)mol/L), and group IV was perfused with temocaprilat (10(-6)mol/L) in combination with CV-11974 (10(-6) mol/L). Groups II and III showed a significant (p<0.05) inhibition of an overshoot phenomenon of PCr during postischemic reperfusion compared with group I. Group IV also showed a more pronounced significant (p<0.01) inhibition of the overshoot of PCr during reperfusion compared with group I. Groups II, III and IV showed a significant (p<0.05) inhibition of the decrease in ATP during global ischemia (59+/-2, 54+/-3 and 54+/-7%, respectively) compared with group I (45+/-3%). Groups II and IV showed a significant (p<0.05) early recovery of ATP during reperfusion (81+/-2, 80+/-6%) compared with group I (71+/-3%) and group II (73+/-2%). Group IV showed no more significant recovery in ATP than group III. There were no differences in LVDevP, LVEDP and coronary flow among these groups. In conclusion, temocaprilat in combination with CV-11974 has significant potential for improving myocardial energy metabolism during both myocardial ischemia and reperfusion.

Differential effects of long-term renin-angiotensin system blockade on limitation of infarct size in cholesterol-fed rabbits

We evaluated the effects of chronic inhibition of angiotensin-converting enzyme (ACE) or receptor blockade of angiotensin II type I on the size of myocardial infarcts induced by coronary occlusion-reperfusion in rabbits fed a high-cholesterol or normal diet for 10 weeks. In treated rabbits, myocardial infarction occurred 24 h after the last dose of enalapril or L-158809, an angiotensin II type I receptor antagonist, because of the drugs' waning effects on hemodynamic parameters. The size of the infarct was significantly larger in cholesterol-fed rabbits than in rabbits fed a normal diet. This augmentation of infarct size in cholesterol-fed rabbits was reversed by long-term treatment with enalapril, but not L-158809. The favorable effects of enalapril treatment disappeared after pretreatment with the bradykinin B(2) receptor blocker HOE 140. Long-term enalapril or L-158809 administration did not reduce the size of the infarct in rabbits fed a normal diet. ACE activity in ischemic myocardium significantly exceeded that in nonischemic myocardium and was further increased in cholesterol-fed rabbits, but was significantly reduced by long-term enalapril, but not L-158809. Moreover, treatment with enalapril, but not L-158809, restored acetylcholine-induced endothelium-dependent relaxation of aortic rings from cholesterol-fed rabbits. These results demonstrate that long-term ACE inhibition, but not angiotensin II type I receptor blockade, effectively reduces the size of myocardial infarcts in cholesterol-fed rabbits. The favorable effects of enalapril treatment may involve primarily a bradykinin B(2) receptor-mediated pathway.

A comparison of intervention with losartan or captopril in acute myocardial infarction

AIM OF STUDY

Angiotensin-converting enzyme (ACE) inhibitors prolong life, lower the progression of heart failure, and decrease the need for hospitalizations in patients after myocardial infarctions. It is still unclear whether these effects could also be achieved by blocking the angiotensin II (ATII) type 1 receptor.

METHODS AND RESULTS

We randomized 201 patients with acute myocardial infarction treated with either direct angioplasty, thrombolysis, or heparin alone to the ACE inhibitor captopril or the ATII antagonist losartan. The primary endpoints were safety, tolerability, and left ventricular parameters. The patients were followed for at least 15 days. The incidence of severe adverse events was similar in both groups, although cough presented less often in the losartan group. Captopril failed to prevent an increase in end-diastolic volume and did not influence left ventricular end-systolic volume. This effect led to an increase in the left ventricular ejection fraction (P<0. 001) without a change in wall-motion index. Losartan did not affect end-diastolic volume but decreased end-systolic volume (P<0.001), resulting in a significant increase in left ventricular ejection fraction (P<0.001) and a decrease in wall-motion index (P<0.001).

CONCLUSION

This study suggests that losartan is safe and well tolerated in patients after myocardial infarction. ATII antagonists seem to have a more pronounced effect on left ventricular remodeling than ACE inhibitors.

Participation of angiotensin II and bradykinin in contractile function in dog stunned myocardium

We examined the effects of enalapril and 4'-[(1, 4'-dimethyl-2'-propyl-[2,6'-bi-1H-enzimidazole]-1'-yl)methyl]-[1, 1'-biphenyl]-2-carboxylic acid (BIBR-277), an angiotensin II receptor antagonist, on contractile dysfunction in the stunned myocardium. Dogs were subjected to 20-min ligation of the coronary artery, followed by 60-min reperfusion. Saline, enalapril (1 mg/kg or 3 mg/kg), or BIBR-277 (3 mg/kg) was injected i.v. 10 min before ligation. D-Arginyl-L-arginlyl-L-prolyl-trans-4-hydroxy-L-prolylglycyl -3-(2-thi enyl)-L-alanyl-L-seryl-D-1,2,3, 4-tetrahydro-3-isoquinolinecarbonyl-L-(2alpha, 3beta, 7abeta)-octahydro-1H-indole-2-carbonyl-L-arginine (Hoe-140), a bradykinin B(2) receptor antagonist, at 300 microg/kg was injected i. v. 10 min before drug injection. Contractile function was assessed on the basis of percentage segment shortening (%SS). ATP levels were measured in 60-min reperfused hearts. %SS significantly decreased during ischemia, and recovered during reperfusion, although the %SS was significantly less than the pre-ischemic level. Both enalapril at either dose and BIBR-277 significantly enhanced %SS recovery during reperfusion, an effect which was associated with a tendency toward energy preservation. Hoe-140 completely abolished the effect of enalapril at either dose, while it did not modify that of BIBR-277. Inhibition of angiotensin II formation and bradykinin breakdown may be separately related to the improvement of myocardial stunning.

Effects of the insurmountable angiotensin AT1 receptor antagonist candesartan and the surmountable antagonist losartan on ischemia/reperfusion injury in rat hearts

Two angiotensin AT1 receptor antagonists with different receptor binding characteristics, candesartan (insurmountable antagonism) and losartan (surmountable antagonism), were compared as regards their effects on angiotensin II-induced vasoconstriction and on myocardial ischemia/reperfusion injury. In isolated rat hearts perfused under constant flow, it was found that at equipotent concentrations candesartan (10 nM) and losartan (3 microM) almost completely inhibited the angiotensin II-induced increase in coronary perfusion pressure. However, if a washout period was introduced before the angiotensin II challenge, the effect of losartan quickly vanished, while that of candesartan remained. In hearts subjected to 25 min of global ischemia and 45 min of reperfusion, pre-treatment with candesartan (10 nM) or losartan (3 microM) immediately prior to ischemia improved the recovery of left ventricular developed pressure as compared to the effect of vehicle (69 +/- 3.2 and 64 +/- 2.3 vs. 44 +/- 6.2%, respectively; mean +/- S.E.M, P < 0.05). When ischemia was initiated following 30 min of washout after drug administration, the recovery of left ventricular developed pressure was higher in the candesartan group (73 +/- 3.2%, P < 0.05), but not in the losartan group (63 +/- 2.8%), than in the vehicle group (58 +/- 4.8%). The cumulative creatine kinase release during the first 30 min of reperfusion in the washout experiments was lower in the candesartan group (28.5 +/- 2.30 U, P < 0.05), but not in the losartan (40.8 +/- 6.73 U) group, than in the vehicle group (48.1 +/- 4.35 U). No significant difference between groups in left ventricular end-diastolic pressure and coronary perfusion pressure was found. The present results demonstrate that angiotensin AT1 receptor antagonists at equipotent concentrations could differ in their cardioprotective effects in hearts subjected to ischemia/reperfusion. It is suggested that the insurmountable AT1 receptor characteristics of candesartan could provide more persistent cardioprotection than the surmountable receptor characteristics of losartan.

EXP3174, the AII antagonist human metabolite of losartan, but not losartan nor the angiotensin-converting enzyme inhibitor captopril, prevents the development of lethal ischemic ventricular arrhythmias in a canine model of recent myocardial infarction

OBJECTIVES

The antiarrhythmic efficacies of the competitive angiotensin II (AII) antagonist losartan, losartan's more potent noncompetitive AII antagonist human metabolite EXP3174 and the angiotensin-converting enzyme inhibitor captopril were assessed in a canine model of recent myocardial infarction.

BACKGROUND

Multiple hemodynamic and electrophysiologic effects of AII may contribute to cardiac electrical instability. In the recent Losartan Heart Failure Study, Evaluation of Losartan in the Elderly (ELITE), a 722-patient trial primarily designed to assess effects on renal function, an unexpected survival benefit was observed with losartan compared with captopril, with the lower mortality using losartan primarily confined to a reduction in sudden cardiac death.

METHODS

Intravenous losartan (1 mg/kg + 0.03 mg/kg/min), EXP3174 (0.1 mg/kg + 0.01 mg/kg/min), captopril (1 mg/kg + 0.5 mg/kg/h) or vehicle were infused in anesthetized dogs with recent (8.1 +/- 0.4 days) anterior myocardial infarction. Electrolytic injury of the left circumflex coronary artery to induce thrombotic occlusion and posterolateral ischemia was initiated 1 h after the start of treatment.

RESULTS

Losartan, EXP3174 and captopril elevated plasma renin activities and comparably and significantly reduced mean arterial pressure. No significant electrocardiographic or cardiac electrophysiologic effects were noted with any treatment. Incidences of acute posterolateral ischemia-induced lethal arrhythmias were: vehicle, 7/9 (77%); losartan, 6/8 (75%); EXP3174, 2/8 (25%; p < 0.05 vs. vehicle control); captopril, 7/10 (70%). There were no among-group differences in time to onset of acute posterolateral ischemia or underlying anterior infarct size.

CONCLUSIONS

EXP3174, but not losartan nor captopril, reduced the incidence of lethal ischemic ventricular arrhythmia in this preparation. The antiarrhythmic efficacy of EXP3174 may be due to an attenuation of deleterious effects of local cardiac AII formed during acute myocardial ischemia or, alternatively, a non-AII-related activity specific to EXP3174. These findings suggest that in humans, metabolic conversion of losartan to EXP3174 may afford antiarrhythmic protection.

Infarct size reduction by AT1-receptor blockade through a signal cascade of AT2-receptor activation, bradykinin and prostaglandins in pigs

OBJECTIVE

We studied the effect of the angiotensin II type 1 (AT1)-receptor antagonist candesartan on infarct size resulting from regional myocardial ischemia in pigs.

BACKGROUND

The effects of AT1-receptor blockade on infarct size in different species remain controversial and its potential cardioprotective mechanisms are still unclear. In pigs, infarct development closely resembles that observed in humans.

METHODS

A total of 62 enflurane-anesthetized pigs underwent a protocol of 90-min low-flow ischemia and 120-min reperfusion. Systemic hemodynamics (micromanometer), regional myocardial function (sonomicrometry), regional myocardial blood flow (microspheres) and infarct size (TTC [triphenyl tetrazolium chloride]-staining) were determined.

RESULTS

Left ventricular peak pressure decreased with candesartan (1 mg/kg i.v.) from 97+/-2 standard error of the mean (SEM) to 86+/-5 mm Hg and was then readjusted by aortic banding. In placebo pigs (n=9), infarct size was 21.8+/-4.8% of the area at risk. Candesartan (n=7) reduced infarct size to 9.7+/-2.5% (p < 0.05). Pretreatment with the AT2-receptor antagonist PD123319 (3 microg/kg/min intracoronarily [i.c.]; n=8), the bradykinin B2-receptor antagonist HOE140 (0.01 microg/kg/min i.c.; n=8) or the cyclooxygenase inhibitor indomethacin (10 mg/kg i.v.; n= 8) per se did not affect infarct size but did abolish the reduction of infarct size achieved by candesartan (PD123319 + candesartan (n=7): 23.2+/-4.7%; HOE140 + candesartan (n=7): 18.2+/-4.0%; indomethacin + candesartan (n=8): 21.1+/-5.2%). Hemodynamics, regional myocardial blood flow during ischemia and the area at risk were comparable among all groups of pigs.

CONCLUSIONS

Reduction of infarct size by the AT1-receptor antagonist candesartan in pigs involves angiotensin II type 2 receptor (AT2) activation, bradykinin and prostaglandins.

Relative effects of alpha 1-adrenoceptor blockade, converting enzyme inhibitor therapy, and angiotensin II subtype 1 receptor blockade on ventricular remodeling in the dog

BACKGROUND

Progressive ventricular remodeling after myocardial damage is associated with a poor prognosis. Optimal prevention of the histopathological processes involved in remodeling requires a more complete understanding of the mechanisms involved in initiating and maintaining these structural changes. Since the sympathetic nervous system and the renin-angiotensin system may be involved in the remodeling process, the structural effects of pharmacological inhibitors have been evaluated in a canine model of localized myocardial injury resulting from transmyocardial DC shock.

METHODS AND RESULTS

The study is comprised of two protocols run in series. In protocol 1, zofenopril (Z), a converting enzyme inhibitor (CEI), prevented the increase in left ventricular mass (LVM) and end-diastolic volume (LVV) observed in the control group (C) at 16 weeks (Z: LVM, 69.8 +/- 3.4 to 65.4 +/- 2.6 g, P = NS; LVV, 45.4 +/- 2.7 to 51.6 +/- 2.7 mL, P = NS; C: LVM, 68.4 +/- 3.2 to 91.4 +/- 2.9 g, P = .0001; LVV, 56.6 +/- 3.0 to 71.9 +/- 2.4 mL, P = .0003). Terazosin, an alpha 1-adrenoceptor antagonist, failed to prevent remodeling at 16 weeks despite continued receptor blockade. In protocol 2, the antiremodeling effect of full-dose CEI therapy with ramipril was confirmed. Low-dose ramipril that exerted no hemodynamic effect failed to prevent remodeling (LVM, 89.7 +/- 4.6 to 105.7 +/- 3.4 g, P = .01; LVV, 61.8 +/- 3.8 to 76.8 +/- 3.3 mL, P = .002). An angiotensin II subtype 1 receptor blocker also failed to prevent the increase in LVM or LVV (LVM, 89.0 +/- 4.6 to 109.7 +/- 5.3 g, P = .0001; LVV, 66.0 +/- 1.9 to 78.4 +/- 3.6 mL, P = .007).

CONCLUSIONS

High-dose CEI therapy can prevent progressive structural changes resulting from localized myocardial damage induced by DC shock. the failure of alpha 1-adrenoceptor blockade and angiotensin II subtype 1 blockade to attenuate remodeling argues against an important direct role for norepinephrine acting through alpha 1-receptors or angiotensin II acting through the type 1 receptor in the remodeling process in this model.

Effects of converting enzyme inhibition on heart period variability in patients with acute myocardial infarction

BACKGROUND

Heart period variability provides useful prognostic information on autonomic cardiac control, and a strong association has been demonstrated after myocardial infarction (MI) between cardiac mortality, sudden death, and reduced total power, ultralow-frequency (ULF) power, and very-low-frequency (VLF) power. Converting enzyme inhibitors are widely used in MI patients, but their influence on heart period variability remains to be defined.

METHODS AND RESULTS

Time- and frequency-domain measures of heart period variability were calculated from 24-hour Holter monitoring in 40 patients with a first uncomplicated MI. After baseline examination between 48 and 72 hours after symptom onset, patients were randomly assigned to placebo or captopril administration, and on the third day, 24-hour Holter monitoring was repeated. No changes in time and frequency domain were detectable after placebo. After captopril, the SD of all normal RR (NN) intervals (SDNN) increased from 90 +/- 29 to 105 +/- 30 milliseconds (P < .01); the SD of the average NN intervals for all 5-minute segments (SDANN index) and the mean of the SDs of all NN intervals for all 5-minute segments (SDNN index) also increased from 74 +/- 24 to 90 +/- 26 milliseconds (P < .01) and from 45 +/- 17 to 49 +/- 15 milliseconds (P < .05), respectively. The root mean square successive difference (r-MSSD) and the percent of differences between adjacent NN intervals > 50 milliseconds (pNN50) remained unchanged. In regard to frequency-domain measures, after captopril, total power (ln unit) increased from 8.28 +/- 0.42 to 8.47 +/- 0.30 (P < .01); considering the frequency bands, a significant increase was observed in ULF (P < .01), VLF (P < .05), and low-frequency (LF) power (P < .05), whereas high-frequency (HF) power remained unchanged.

CONCLUSIONS

This study supports the hypothesis that the renin-angiotensin system modulates the amplitude of ULF and VLF power. Furthermore, it demonstrates that in MI patients, converting enzyme inhibition favorably modifies measures of heart period variability strongly associated with a poor prognosis.

Relation between tonic sympathetic and vagal control of human sinus node function

BACKGROUND

Clinical conditions, such as heart failure or myocardial infarction are associated with enhanced sympathetic and reduced parasympathetic activity as compared to normal controls. The reciprocal alteration in cardiac autonomic tone likely contributes to the electrical instability of the myocardium. Little information is available on the relation between sympathetic and vagal cardiac control in healthy human subjects.

METHODS AND RESULTS

Heart period changes in response to autonomic blockades were measured in 16 young, healthy human subjects. Adrenergic and cholinergic blockades were induced by i.v. propranolol (0.2 mg/kg) and atropine (0.04 mg/kg) in two opposite orders on two occasions; interindividual correlations were performed between the R-R interval responses to propranolol and to atropine obtained under the various blockade conditions, and the magnitude of the responses were compared by a drug x order two factorial ANOVA design. It was found, that previous adrenergic blockade did not reduce the extent of cardioacceleration produced by subsequent cholinergic blockade and that the R-R interval responses to atropine and to subsequently given propranolol did not share significant variance across subjects (r = 0.22, P = 0.234). Also, no interindividual correlation was found between the R-R interval responses to propranolol and to atropine, with the influence of the other, respective, autonomic division already blocked (r = 0.42, P = 0.114).

CONCLUSIONS

Under resting conditions, activity levels of cardiac vagal and sympathetic outflows are not related across young, healthy human subjects and peripheral interaction is not manifest between the autonomic divisions.

The effect of early converting enzyme inhibition on neurohumoral activation in acute myocardial infarction

The effect of early converting enzyme inhibition with enalapril on the extent of neurohumoral activation in acute myocardial infarction was evaluated in a randomized, placebo-controlled double blind fashion. Plasma levels of atrial natriuretic factor and noradrenaline on day 1, i.e. prior to randomization (n = 99), and on days 3 (n = 145) and 30 (n = 69) following myocardial infarction were determined. Enalapril did not significantly affect neurohumoral activation on day 3 (enalapril vs. placebo (mean (S.E.M.); atrial natriuretic factor: 35.3 (3.0) vs. 37.2 (2.9) pmol/l; noradrenaline: 2.82 (0.20) vs. 3.70 (1.02) nmol/l) or at 1 month (atrial natriuretic factor: 33.1 (3.0) vs. 32.4 (3.9) pmol/l; noradrenaline: 2.77 (0.25) vs. 2.82 (0.28) nmol/l). However, in myocardial infarction patients developing heart failure, a significant attenuation of the day 3 atrial natriuretic factor, but not of the noradrenaline response, was seen (atrial natriuretic factor: 47.0 (7.7) vs. 59.0 (6.4) pmol/l, P < 0.05; noradrenaline: 3.37 (0.42) vs. 6.59 (3.26) nmol/l, P = ns). In conclusion, enalapril did not significantly reduce neurohumoral activation in acute myocardial infarction, possibly because the activation in most patients is modest and confined to the early convalescent phase. However, in patients with myocardial infarction and heart failure enalapril therapy was associated with a reduction in early plasma atrial natriuretic factor levels, compatible with decreased cardiac filling pressures.

Myocardial injury: the acute phase response and lipoprotein metabolism

Myocardial infarction and other types of tissue injury generate changes in plasma proteins known as the acute phase response. Variations in lipid and lipoprotein levels after acute myocardial infarction are manifest within 24 to 48 h after the onset of chest pain. Maximal postinfarction reductions in total cholesterol occur at days 4 to 5 with levels 47% below baseline; low and high density lipoprotein cholesterol fractions decrease to their nadir on day 7 to concentrations that are 48% and 32% below baseline, respectively. Triglyceride levels increase after acute myocardial infarction to a maximal level that is 58% above baseline on day 7. These alterations in lipid and lipoprotein levels generally stabilize by 2 months after the acute event. Screening for dyslipidemias in survivors of myocardial infarction requires clinical decision-making based on accurate and reliable measurements. The clinician must be familiar with characteristic changes in acute phase lipids and lipoproteins to ensure that patients receive appropriate, potentially life-saving therapy.

"Cardioprotection" by ACE-inhibitors in acute myocardial ischemia and infarction?

Coronary artery occlusion results in the acute activation of the renin-angiotensin system and production of angiotensin II, a potent vasoconstrictor and positive inotropic agent. This has raised the possibility that angiotensin converting enzyme (ACE) inhibitors might be "cardioprotective" (that is, might attenuate myocardial injury, dysfunction and necrosis) in the setting of acute ischemia and infarction. Captopril, enalapril and ramipril have, in fact, been reported to acutely limit myocardial injury and necrosis in models of permanent coronary artery occlusion. The mechanisms responsible for this cardioprotection are complex, but include favorable alterations in myocardial oxygen supply/demand, and, in some instances, inhibition of bradykinin metabolism and/or increased prostaglandin synthesis. Other studies, however, have failed to document a reduction in infarct size with ACE inhibitor treatment. Results obtained in models of coronary occlusion/reperfusion have also been mixed. In models of brief transient ischemia not associated with necrosis, captopril and zofenopril have consistently been found to attenuate postischemic contractile dysfunction of the viable but "stunned" myocardium during the early hours following relief of ischemia. In contrast, there is no consensus on the effects of enalapril on the stunned myocardium: both positive and negative results have been obtained. Similar disparity has been reported in models of more prolonged ischemia/reperfusion resulting in subendocardial necrosis: some studies have reported myocardial salvage, while others have provided disturbing evidence of apparent exacerbation of myocardial necrosis with captopril and enalapril therapy. Thus, after a decade of investigative effort, the question of whether ACE inhibitors are "cardioprotective" in the setting of acute myocardial ischemia and infarction remains unresolved. Nonetheless, clinical protocols are in progress to assess the effects of early ACE inhibitor treatment in patients with acute myocardial infarction.