Activation of neurohumoral systems following acute myocardial infarction

Prediction of adverse cardiovascular events in children using artificial intelligence-based electrocardiogram

BACKGROUND

Convolutional neural networks (CNNs) have emerged as a novel method for evaluating heart failure (HF) in adult electrocardiograms (ECGs). However, such CNNs are not applicable to pediatric HF, where abnormal anatomy of congenital heart defects plays an important role. ECG-based CNNs reflecting neurohormonal activation (NHA) may be a useful marker of pediatric HF. This study aimed to develop and validate an ECG-derived marker of pediatric HF that reflects the risk of future cardiovascular events.

METHODS

Based on 21,378 ECGs from 8324 children, a CNN was trained using B-type natriuretic peptide (BNP) and the occurrence of major adverse cardiovascular events (MACEs). The output of the model, or the electrical heart failure indicator (EHFI), was compared with the BNP regarding its ability to predict MACEs in 813 ECGs from 295 children.

RESULTS

EHFI achieved a better area under the curve than BNP in predicting MACEs within 180 days (0.826 versus 0.691, p = 0.03). On Cox univariable analyses, both EHFI and BNP were significantly associated with MACE (log10 EHFI: hazard ratio [HR] = 16.5, p < 0.005 and log10 BNP: HR = 4.4, p < 0.005). The time-dependent average precisions of EHFI in predicting MACEs were 32.4%-67.9% and 1.6-7.5-fold higher than those of BNP in the early period. Additionally, the MACE rate increased monotonically with EHFI, whereas the rate peaked at approximately 100 pg/mL of BNP and decreased in the higher range.

CONCLUSIONS

ECG-derived CNN is a novel marker of HF with different prognostic potential from BNP. CNN-based ECG analysis may provide a new guide for assessing pediatric HF.

A review of therapeutic approaches for post-infarction left ventricular remodeling

Left ventricular remodeling is an adaptive process initially developed in response to acute myocardial infarction (AMI), but it ends up with negative adverse outcomes such as infarcted wall thinning, ventricular dilation, and cardiac dysfunction. A prolonged excessive inflammatory reaction to cardiomyocytes death and necrosis plays the crucial role in the pathophysiological mechanisms. The pharmacological treatment includes nitroglycerine, β-blockers, ACEi/ARBs, SGLT2i, mineralocorticoid receptor antagonists, and some miscellaneous aspects. Stem cells therapy, CD34+ cells transplantation and gene therapy constitute the promissing therapeutic approaches for post AMI cardiac remodeling, thereby enhancing angiogenesis, cardiomyocytes differenciation and left ventricular function on top of inhibiting apoptosis, inflammation, and collagen deposition. All these lead to reduce infarct size, scar formation and myocardial fibrosis.

Clinical factors associated with arrhythmia and short-term prognosis following mitral valve repair: a retrospective cohort study

BACKGROUND

Postoperative arrhythmia (POA) is one of the common and serious postoperative complications. This retrospective study was conducted to investigate the clinical factors associated with POA and its short-term prognosis following mitral valve repair.

METHODS

A total of 618 patients receiving mitral valve repair between January 2015 and November 2020 in our hospital were included in this retrospective study, including 318 males and 300 females and aged 53.9±9.3 years. The patients were grouped into arrhythmia and non-arrhythmia groups and investigated for risk factors associated with the prognosis of POA using multivariate logistic regression based on their clinical data.

RESULTS

POA was observed in 314 (50.8%) patients and atrial fibrillation (AF) was the most frequent (43.3%) type of POA. Compared with non-arrhythmia patients, arrhythmia patients had significantly longer time to use vasoactive drug use, longer intensive care unit (ICU) stay and longer hospital stay. In addition, the incidence of postoperative heart failure was significantly higher (P<0.05). Logistic regression analysis showed that preoperative arrhythmia [odds ratio (OR) =9.17; 95% confident interval (CI): 4.49-18.10], postoperative pain (OR =4.70; 95% CI: 1.55-6.12) and postoperative hypoxemia (OR =3.25; 95% CI: 1.04-6.28) were independently associated with POA.

CONCLUSIONS

This study demonstrates that the incidence of arrhythmia is relatively high after mitral valve repair and is associated with preoperative arrhythmia, postoperative pain and postoperative hypoxemia.

Neurohormonal activation in heart failure with reduced ejection fraction

Heart failure with reduced ejection fraction (HFrEF) develops when cardiac output falls as a result of cardiac injury. The most well-recognized of the compensatory homeostatic responses to a fall in cardiac output are activation of the sympathetic nervous system and the renin-angiotensin-aldosterone system (RAAS). In the short term, these 'neurohormonal' systems induce a number of changes in the heart, kidneys, and vasculature that are designed to maintain cardiovascular homeostasis. However, with chronic activation, these responses result in haemodynamic stress and exert deleterious effects on the heart and the circulation. Neurohormonal activation is now known to be one of the most important mechanisms underlying the progression of heart failure, and therapeutic antagonism of neurohormonal systems has become the cornerstone of contemporary pharmacotherapy for heart failure. In this Review, we discuss the effects of neurohormonal activation in HFrEF and highlight the mechanisms by which these systems contribute to disease progression.

Highly sensitive index of sympathetic activity based on time-frequency spectral analysis of electrodermal activity

Time-domain indices of electrodermal activity (EDA) have been used as a marker of sympathetic tone. However, they often show high variation between subjects and low consistency, which has precluded their general use as a marker of sympathetic tone. To examine whether power spectral density analysis of EDA can provide more consistent results, we recently performed a variety of sympathetic tone-evoking experiments (43). We found significant increase in the spectral power in the frequency range of 0.045 to 0.25 Hz when sympathetic tone-evoking stimuli were induced. The sympathetic tone assessed by the power spectral density of EDA was found to have lower variation and more sensitivity for certain, but not all, stimuli compared with the time-domain analysis of EDA. We surmise that this lack of sensitivity in certain sympathetic tone-inducing conditions with time-invariant spectral analysis of EDA may lie in its inability to characterize time-varying dynamics of the sympathetic tone. To overcome the disadvantages of time-domain and time-invariant power spectral indices of EDA, we developed a highly sensitive index of sympathetic tone, based on time-frequency analysis of EDA signals. Its efficacy was tested using experiments designed to elicit sympathetic dynamics. Twelve subjects underwent four tests known to elicit sympathetic tone arousal: cold pressor, tilt table, stand test, and the Stroop task. We hypothesize that a more sensitive measure of sympathetic control can be developed using time-varying spectral analysis. Variable frequency complex demodulation, a recently developed technique for time-frequency analysis, was used to obtain spectral amplitudes associated with EDA. We found that the time-varying spectral frequency band 0.08-0.24 Hz was most responsive to stimulation. Spectral power for frequencies higher than 0.24 Hz were determined to be not related to the sympathetic dynamics because they comprised less than 5% of the total power. The mean value of time-varying spectral amplitudes in the frequency band 0.08-0.24 Hz were used as the index of sympathetic tone, termed TVSymp. TVSymp was found to be overall the most sensitive to the stimuli, as evidenced by a low coefficient of variation (0.54), and higher consistency (intra-class correlation, 0.96) and sensitivity (Youden's index > 0.75), area under the receiver operating characteristic (ROC) curve (>0.8, accuracy > 0.88) compared with time-domain and time-invariant spectral indices, including heart rate variability.

Power Spectral Density Analysis of Electrodermal Activity for Sympathetic Function Assessment

Time-domain features of electrodermal activity (EDA), the measurable changes in conductance at the skin surface, are typically used to assess overall activation of the sympathetic system. These time domain features, the skin conductance level (SCL) and the nonspecific skin conductance responses (NS.SCRs), are consistently elevated with sympathetic nervous arousal, but highly variable between subjects. A novel frequency-domain approach to quantify sympathetic function using the power spectral density (PSD) of EDA is proposed. This analysis was used to examine if some of the induced stimuli invoke the sympathetic nervous system's dynamics which can be discernible as a large spectral peak, conjectured to be present in the low frequency band. The resulting indices were compared to the power of low-frequency components of heart rate variability (HRVLF) time series, as well as to time-domain features of EDA. Twelve healthy subjects were subjected to orthostatic, physical and cognitive stress, to test these techniques. We found that the increase in the spectral powers of the EDA was largely confined to 0.045-0.15 Hz, which is in the prescribed band for HRVLF. These low frequency components are known to be, in part, influenced by the sympathetic nervous dynamics. However, we found an additional 5-10% of the spectral power in the frequency range of 0.15-0.25 Hz with all three stimuli. Thus, dynamics of the normalized sympathetic component of the EDA, termed EDASympn, are represented in the frequency band 0.045-0.25 Hz; only a small amount of spectral power is present in frequencies higher than 0.25 Hz. Our results showed that the time-domain indices (the SCL and NS.SCRs), and EDASympn, exhibited significant increases under orthostatic, physical, and cognitive stress. However, EDASympn was more responsive than the SCL and NS.SCRs to the cold pressor stimulus, while the latter two were more sensitive to the postural and Stroop tests. Additionally, EDASympn exhibited an acceptable degree of consistency and a lower coefficient of variation compared to the time-domain features. Therefore, PSD analysis of EDA is a promising technique for sympathetic function assessment.

Biomarkers of activation of renin-angiotensin-aldosterone system in heart failure: how useful, how feasible?

Renin-angiotensin-aldosterone system (RAAS), participated by kidney, liver, vascular endothelium, and adrenal cortex, and counter-regulated by cardiac endocrine function, is a complex endocrine system regulating systemic functions, such as body salt and water homeostasis and vasomotion, in order to allow the accomplishment of physiological tasks, such as orthostasis, physical and emotional stimuli, and to react towards the hemorrhagic insult, in tight conjunction with other neurohormonal axes, namely the sympathetic nervous system, the endothelin and vasopressin systems. The systemic as well as the tissue RAAS are also dedicated to promote tissue remodeling, particularly relevant after damage, when chronic activation may configure as a maladaptive response, leading to fibrosis, hypertrophy and apoptosis, and organ dysfunction. RAAS activation is a fingerprint of systemic arterial hypertension, kidney dysfunction, vascular atherosclerotic disease, and is definitely an hallmark of heart failure, which rapidly shifts from organ disease to a disorder of neurohormonal regulatory systems. Chronic RAAS activation is an indirect or direct target of most effective pharmacological treatments in heart failure, such as beta-blockers, inhibitors of angiotensin converting enzyme, angiotensin receptor blockers, direct renin inhibitors, and mineralocorticoid receptor blockers. Biomarkers of RAAS activation are available, with different feasibility and accuracy, such as plasma renin activity, renin, angiotensin II, and aldosterone, which all accompany the increasing clinical severity of heart failure disease, and are well recognized prognostic factors, even in patients with optimal therapy. Polymorphisms influencing the expression and activity of RAAS pathways have been recognized as clinically relevant biomarkers, likely influencing either the individual clinical phenotype, or the response to drugs. This solid, growing evidence strongly suggests the rationale for the use of biomarkers of the RAAS activation, as a guide to tailor individual therapy in the current practice, and their implementation as a rule-in marker for future trials on novel drugs in the heart failure setting.

Lipoproteins as biomarkers and therapeutic targets in the setting of acute coronary syndrome

The period following an acute coronary syndrome (ACS) represents a critical time frame with a high risk for recurrent events and death. The pathogenesis of this increase in clinical cardiovascular disease events after ACS is complex, with molecular mechanisms including increased thrombosis and inflammation. Dyslipoproteinemia is common in patients with ACS and predictive of recurrent cardiovascular disease events after presentation with an ACS event. Although randomized clinical trials have provided fairly convincing evidence that high-dose statins reduce the risk of recurrent cardiovascular events after ACS, there remain questions about how aggressively to reduce low-density lipoprotein cholesterol levels in ACS. Furthermore, no other lipid-related interventions have yet been proven to be effective in reducing major cardiovascular events after ACS. Here, we review the relationship of lipoproteins as biomarkers to cardiovascular risk after ACS, the evidence for lipid-targeted interventions, and the potential for novel therapeutic approaches in this arena.

Hospitalization and cognitive decline: Can the nature of the relationship be deciphered?

BACKGROUND

Evidence for a relationship between hospitalization and incident cognitive decline exists mainly in the literature focusing on critical care hospitalization. Recent studies, however, have also found an association between noncritical care hospitalization and the development of cognitive decline.

OBJECTIVE

This article will review the literature pertaining to hospitalization and cognitive decline, including hospitalizations for both critical and noncritical care, and in medical and surgical patients. The article will also explore the various factors that have been implicated in the development of cognitive decline and dementia.

METHODS

Review of the literature was completed using PubMed and Medline search programs.

RESULTS

Several articles supporting evidence for the association between hospitalization and cognitive decline are available. Evidence for potential mediating factors also does exist.

CONCLUSIONS

There is evidence to support an association between hospitalization and development of cognitive decline. Factors that could mediate this association include, but may not be limited to, delirium, medications, stress, and depression. There is a need for further research in this area in order to better understand the underlying pathophysiology involved in the development of cognitive decline and dementia and to determine if preventive measures might be beneficial in decreasing risk for cognitive decline for patients who are hospitalized.

Dramatic changes in catestatin are associated with hemodynamics in acute myocardial infarction

Acute myocardial infarction (AMI) is characterized by complex neuroendocrine activation. To investigate catestatin profiles, serial catestatin levels were determined by enzyme-linked immunosorbent assay in the first week after AMI in 50 patients. Catestatin levels reduced at admission and negatively correlated with heart rates; it increased significantly on the third day but remained decreased at 1 week and positively with blood pressure. In a subgroup of 20 patients admitted within 4 h after onset, circulating catestatin correlated inversely with norepinephrine. Catestatin might be involved in the course of AMI and act as a tool in monitoring the progression of AMI.

Managing hyponatremia in patients with heart failure

Approximately 20% of heart failure patients have low levels of serum sodium, often at a time when they are hospitalized during a period of decompensation. The presence of hyponatremia adversely affects outcomes in heart failure and is associated with impaired cognitive and neuromuscular function. Current strategies for treating hyponatremia in heart failure patients have limited efficacy. Although the development of hyponatremia in heart failure patients is polyfactorial, the nonosmotic release of arginine vasopressin (AVP) from the posterior pituitary plays a dominant role in this process through its effects on regulating the absorption of free water in the distal portion of the nephron. Drugs which block the effects of AVP on the V2 receptor have been shown to increase serum sodium by promoting the excretion of free water from the kidney. In this review, the theoretical basis supporting the use of AVP blockers is discussed and results from clinical trials in which they were administered to euvolemic and hypervolemic patients are reviewed. Administration of AVP blockers to heart failure patients increases free water excretion, promotes weight loss, and increases serum sodium levels without significant major adverse effects. Clinical trial results demonstrate safety during long-term administration. These findings indicate that the use of AVP receptor antagonists should be considered in heart failure patients who have evidence of significant hyponatremia.

Early use of angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers: evidence from clinical trials

Following acute myocardial infarction, patients are at increased risk of developing heart failure, which is more prevalent in those with reduced ventricular systolic function. Activation of the renin-angiotensin-aldosterone system, which occurs early after myocardial injury, plays a central role in the pathogenesis of subsequent cardiac structural and functional abnormalities. The early use of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers has been tested in several large randomized clinical trials. The results of these trials show that this treatment strategy reduces the incidence of heart failure and mortality in the postmyocardial infarction patient. The magnitude of benefit is larger in patients with high-risk features, particularly those with large infarct size and the presence of heart failure or left ventricular systolic dysfunction at the time of myocardial injury. Careful use of these agents is essential in avoiding clinically significant hypotension in the critical period.

Lipid management: considerations in acute coronary syndrome

Managing dyslipidemia is an important part of the primary and secondary prevention of coronary heart disease. Low-density lipoprotein cholesterol reduction remains the primary lipid goal. Patients who have experienced an acute coronary syndrome (ACS) are at very high risk of recurrent adverse cardiovascular events. A growing body of literature supports the concept that early and intensive treatment with statins after an ACS event decreases recurrent adverse cardiovascular events. We review available evidence pertaining to lipid alterations in ACS.

Vasopressin dysregulation: Hyponatremia, fluid retention and congestive heart failure

Arginine vasopressin (AVP) plays a central role in the regulation of water and electrolyte balance. Dysregulation of AVP secretion, along with stimulation of AVP V2 receptors, is responsible for hyponatremia (serum sodium concentration <135 mEq/L) in congestive heart failure (CHF). The stimulation of atrial and arterial baroreceptors in response to hypotension and volume depletion results in the nonosmotic release of AVP. The predominance of nonosmotic AVP secretion over osmotic AVP release plays a key role in the development of water imbalance and hyponatremia in CHF and other edematous disorders. The AVP-receptor antagonists are a new class of agents that block the effects of AVP directly at V2 receptors in the renal collecting ducts. AVP-receptor antagonism produces aquaresis, the electrolyte-sparing excretion of water, thereby allowing specific correction of water and sodium imbalance. This review summarizes recent data from clinical trials evaluating the efficacy and safety of these promising agents for the treatment of hyponatremia.

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.

Plasma cathepsin D isoforms and their active metabolites increase after myocardial infarction and contribute to plasma renin activity

Plasma renin activity (PRA) is often found to increase after myocardial infarction (MI). Elevated PRA may contribute to increased myocardial angiotensin II that is responsible for maladaptive remodeling of the myocardium after MI. We hypothesized that MI would also result in cardiac release of cathepsin D, a ubiquitous lysosomal enzyme with high renin sequence homology. Cathepsin D release from damaged myocardial tissue could contribute to angiotensin formation by acting as an enzymatic alternate to renin. We assessed circulating renin and cathepsin D from both control and MI patient plasma (7-20 hours after MI) using shallow gradient focusing that allowed for independent measurement of both enzymes. Cathepsin D was increased significantly in the plasma after MI (P < 0.001). Furthermore, circulating active cathepsin D metabolites were also significantly elevated after MI (P < 0.04), and contained the majority of cathepsin D activity in plasma. Spiking control plasma with cathepsin D resulted in a variable but significant (P = 0.005) increase in PRA using a clinical assay. We conclude that 7-20 hours after MI, plasma cathepsin D is significantly elevated and most of the active enzymatic activity is circulating as plasma metabolites. Circulating cathepsin D can falsely increase clinical PRA determinations, and may also provide an alternative angiotensin formation pathway after MI.

Fiftieth anniversary of aldosterone: from discovery to cardiovascular therapy

Half a century after the elucidation of its molecular structure, aldosterone is generating the greatest interest, not in the fields of endocrinology or renal medicine but in cardiology-where aldosterone over-activation is now perceived as detrimental in heart failure (HF) and ischaemic heart disease. Clinically, excess aldosterone is associated with higher morbidity and mortality after myocardial infarction (MI) and HF. The Randomised Aldactone Evaluation Study (RALES) study in severe chronic heart failure and the Eplerenone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival (EPHESUS) study in post-MI heart failure have shown that use of non-selective and selective aldosterone receptor antagonists, respectively, improves prognosis. The pathophysiological mechanisms underpinning these damaging aldosterone-mediated cardiovascular effects are still being elucidated, but prime candidates include cardiomyocyte necrosis and apoptosis, and myocardial fibrosis resulting in adverse cardiac remodelling, coronary vasculopathy, tachyarrhythmia and positive feedback activation of the renin-angiotensin-aldosterone system. Practical points for consideration when instigating therapy include preferential use of aldosterone receptor antagonists to maintain electrolyte balance whenever loop or thiazide diuretics are used (vulnerable HF patients require higher ranges of potassium and magnesium to minimise propensity for tachyarrthythmia), for renoprotection and for counteracting aldosterone breakthrough despite adequate ACE inhibition; use of the minimum doses of loop diuretics required to lessen activation of the renin-angiotensin-aldosterone system in HF; use of selective aldosterone receptor antagonists to avoid gynaecomastia/mastalgia and impotence; and prophylactic use of aldosterone receptor antagonists to improve prognosis.

Myocardial beta-adrenoceptor density one month after acute myocardial infarction predicts left ventricular volumes at six months

OBJECTIVE

To investigate whether myocardial beta-adrenoceptor (beta-AR) downregulation precedes and predicts left ventricular (LV) dilation after acute myocardial infarction (AMI), we measured beta-AR density within four weeks of AMI and correlated it with serial measurements of LV volumes.

BACKGROUND

Patients who develop heart failure following AMI have an increased sympathetic drive to the heart within the first four weeks after infarction.

METHODS

We prospectively studied 61 patients in whom AMI was the first presentation of coronary artery disease (CAD) and with no signs of heart failure. The LV volumes were measured one, three, and six months after AMI by echocardiography. Beta-AR density was measured using positron emission tomography with S-[(11)C]CGP 12177. Seventeen matched healthy volunteers served as controls.

RESULTS

Whole heart beta-AR density was lower in patients than in controls (6.25 +/- 0.98 pmol/g vs. 8.32 +/- 2.14 pmol/g, p < 0.0001). In patients, beta-AR density was inversely correlated with end-systolic and end-diastolic volumes six months after AMI. Patients whose LV was dilated at six months had a lower beta-AR density in noninfarcted myocardium than patients without dilation (6.15 pmol/g vs. 6.98 pmol/g, p = 0.008). In addition, beta-AR density in noninfarcted myocardium was higher when the infarct-related artery was patent (6.87 +/- 1.14 pmol/g vs. 5.76 +/- 0.86 pmol/g occluded, p < 0.01).

CONCLUSIONS

Myocardial beta-AR density is reduced after AMI in the absence of heart failure, and the reduction predicts later LV dilation. These data are suggestive of an enhanced sympathetic drive to the heart, having an important etiologic role in LV remodeling after AMI.

Chronic vasopressin V(1A) but not V(2) receptor antagonism prevents heart failure in chronically infarcted rats

Evidence is increasing that therapeutic modulation of neurohormonal activation with vasopressin receptor antagonists via V(1A) and V(2) receptors may favourably affect prognosis of heart failure. This study was designed to compare in vivo hemodynamic effects of early treatment (1-21 days after infarction) with a V(1A) (SR-49059 or ((2S)1-[(2R3S)-5-chloro-3-(2-chlorophenyl)-1-(3,4-dimethoxybenzene-sulfonyl)-3-hydroxy-2,3-dihydro-1H-indole-2-carbonyl]-pyrrolidine-2-carboxamide); 0.3 mg/kg/day) and a V(2) (SR-121463B or (1-[4-(N-tert-Butylcarbamoyl)-2-methoxybenzene sulfonyl]-5-ethoxy-3-spiro-[4-(2-morpholinoethyoxy)-cyclo-hexane]indol-2one,furmate; 0.5 mg/kg/day) receptor antagonist in myocardial infarcted rats, chronically instrumented for hemodynamic measurements. Left ventricular dysfunction in conscious myocardial infarcted rats, which was evidenced by a significantly decreased cardiac output (myocardial infarction: 70+/-3 vs. sham: 81 +/- 3 ml/min) and stroke volume (myocardial infarction: 190 +/- 10 vs. sham: 221 +/- 7 microl), was restored by the vasopressin V(1A) (81+/-2 ml and 224 +/- 5 microl, respectively) but not V(2) receptor antagonist. Improved cardiac output with the vasopressin V(1A) receptor antagonist resulted from an increased stroke volume at a reduced myocardial infarction induced tachycardia. In addition to the hemodynamic measurements, left ventricular hypertrophy and capillary density were determined, histologically measured as the cross-sectional area of Gomori-stained myocytes and Lectin-stained capillaries per tissue area, respectively. The observed left ventricular concentric hypertrophy (myocardial infarction: 525 +/- 38 vs. sham: 347 +/- 28 microm(2); P < 0.05) and reduced capillary density (myocardial infarction: 2068 +/- 162 vs. sham: 2800 +/- 250 number/mm(2); P<0.05) in the spared myocardium of myocardial infarcted rats, remained unaffected by the vasopressin V(1A) or V(2) receptor antagonist. Thus, chronic vasopressin V(1A) but not V(2) receptor blockade prevents heart failure in 3-week-old infarcted rats. Moreover, the improved cardiac function could not attributed to changes in left ventricular hypertrophy and/or capillary density.

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.

Neurohormonal activation in heart failure after acute myocardial infarction treated with beta-receptor antagonists

BACKGROUND

Few studies have described how neurohormonal activation is influenced by treatment with beta-receptor antagonists in patients with heart failure after acute myocardial infarction. The aims were to describe neurohormonal activity in relation to other variables and to investigate treatment effects of a beta(1) receptor-antagonist compared to a partial beta(1) receptor-agonist.

METHODS

Double-blind, randomized comparison of metoprolol 50-100 mg b.i.d. (n=74), and xamoterol 100-200 mg b.i.d (n=67). Catecholamines, neuropeptide Y-like immunoreactivity (NPY-LI), renin activity, and N-terminal pro-atrial natriuretic factor (N-ANF) were measured in venous plasma before discharge and after 3 months. Clinical and echocardiographic variables were assessed.

RESULTS

N-ANF showed the closest correlations to clinical and echocardiographic measures of heart failure severity, e.g. NYHA functional class, furosemide dose, exercise tolerance, systolic and diastolic function. Plasma norepinephrine, dopamine and renin activity decreased after 3 months on both treatments, in contrast to a small increase in NPY-LI which was greater (by 3.9 pmol/l, 95% CI 1.2-6.6) in the metoprolol group. N-ANF increased on metoprolol, and decreased on xamoterol (difference: 408 pmol/l, 95% CI 209-607). Increase above median of NPY-LI (>25.2 pmol/l, odds ratio 2.8, P=0.0050) and N-ANF (>1043 pmol/l, odds ratio 2.8, P=0.0055) were related to long term (mean follow-up 6.8 years) cardiovascular mortality.

CONCLUSIONS

Decreased neurohormonal activity, reflecting both the sympathetic nervous system and the renin-angiotensin system, was found 3 months after an acute myocardial infarction with heart failure treated with beta-receptor antagonists. The small increase in NPY-LI may suggest increased sympathetic activity or reduced clearance from plasma. The observed changes of N-ANF may be explained by changes in cardiac preload, renal function, and differences in beta-receptor mediated inhibition of atrial release of N-ANF. NPY-LI, and N-ANF at discharge were related to long term cardiovascular mortality.

Changes in vasoconstrictive hormones, natriuretic peptides, and left ventricular remodeling soon after anterior myocardial infarction

OBJECTIVE

Our purpose was to study the changes in vasoconstrictive neurohormones, N-terminal proatrial natriuretic peptide (Nt-proANP), and brain natriuretic peptide (BNP) and their relationship with left ventricular (LV) remodeling soon after anterior myocardial infarction (MI).

BACKGROUND

The Healing and Afterload Reducing Therapy (HEART) trial has shown that early use of ramipril improves left ventricular ejection fraction (LVEF) and attenuates LV remodeling when initiated soon after MI. This neurohumoral substudy of HEART investigates the changes in vasoconstrictive and natriuretic peptides and their relationship with LV remodeling.

METHODS

One hundred twenty-two patients had blood drawn for the measurement of catecholamines, endothelin-I, angiotensin II, Nt-proANP and BNP, and prostacyclins within 24 hours of an MI, and at 3, 14, and 90 days after the MI. Quantitative echocardiograms were performed at baseline and at 14 days.

RESULTS

All neurohormones except angiotensin II (P =.12) and prostaglandins were significantly elevated at baseline. Vasoconstrictive neurohormones decreased significantly over time but remained elevated at 14 days. Both Nt-proANP and BNP were elevated within the first 14 days. BNP decreased significantly by 90 days, whereas Nt-proANP exhibited no change between 14 and 90 days. Ramipril decreased plasma levels of angiotensin II at 3 days but had no effect on the other neurohormones.

CONCLUSIONS

Neurohumoral activation occurs and persists in patients with anterior MI and overall preserved LV function. Ramipril had only a modest impact on neurohormones despite its significant benefits on LV remodeling soon after MI.

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.

Beyond remodeling: a new paradigm for angiotensin-converting enzyme inhibitors following myocardial infarction

Angiotensin converting enzyme (ACE) inhibitors, originally designed to treat hypertension, were quickly demonstrated to confer hemodynamic and survival benefit to patients with congestive heart failure. Extending this paradigm to patients with left ventricular dysfunction (LVD) post-myocardial infarction (MI), ACE inhibitors were shown to attenuate ventricular remodeling and reduce mortality. An unexpected finding that ACE inhibitors could reduce the incidence of myocardial infarction, prompted enormous interest in their anti-ischemic potential. Indeed, a significant body of experimental literature supports the concept that ACE inhibitors have direct anti-atherosclerotic and anti-ischemic effect. Recent clinical trials have shown that ACE inhibitors confer significant protection from ischemic events.

Regional wall stress predicts ventricular remodeling after anteroseptal myocardial infarction in the Healing and Early Afterload Reducing Trial (HEART): an echocardiography-based structural analysis

BACKGROUND

Increased left ventricular (LV) wall stress after myocardial infarction (MI) has been implicated in LV remodeling. However, the relationship between LV wall stress and LV remodeling is incompletely defined.

METHOD

We prospectively studied the relationship between regional wall stress and LV remodeling by application of the finite element method to end-systolic LV models from patients enrolled in the Healing and Early Afterload Reducing Therapy (HEART) Trial. Individual LV models were constructed from orthogonal apical echocardiographic views obtained at day 14 after anteroseptal MI in 64 patients. Of these, 31 patients received low-dose (0.625 mg) ramipril and 33 patients received full-dose (10 mg) ramipril. LV wall stress was calculated by the finite element method and correlated with change in LV volume from day 14 to day 90 after MI.

RESULTS

Among all patients, increases in apical regional wall stress were associated with LV volume changes (P -trend =.015). The relationship between apical regional wall stress and change in LV volume was strongest in the low-dose ramipril group (r = 0.53, P =.002) and remained significant after adjustment for end-diastolic volume, infarct size, ejection fraction, and systolic blood pressure yet was attenuated in the full-dose ramipril group.

CONCLUSIONS

Apical regional wall stress is an independent predictor of subsequent LV remodeling after MI. The relationship between increased apical wall stress and LV dilatation appears to be attenuated by full-dose angiotensin-converting enzyme inhibition.

Early neurohormonal effects of trandolapril in patients with left ventricular dysfunction and a recent acute myocardial infarction: a double-blind, randomized, placebo-controlled multicentre study

Angiotensin-converting enzyme inhibitors improve long-term survival in patients with left ventricular dysfunction after a myocardial infarction, but their mechanism of action is not entirely clear. The neurohormonal effects may be important in this respect, as well as an early hemodynamic unloading induced by these drugs. The primary objective was to assess the effect of trandolapril on plasma levels of atrial natriuretic peptide. A secondary objective was to assess the effects of trandolapril on selected neurohormones, vasoactive peptides and enzymes, which may be important in the development of left ventricular remodeling and heart failure following an acute myocardial infarction. A total of 119 patients with an acute myocardial infarction and a wall motion index < or =1.2 (16-segment echocardiographic model) were randomized to double blind treatment with trandolapril or placebo within 3-7 days after the onset of infarction. Blind treatment was discontinued 21 days after the index infarction. Venous blood samples were collected at rest, before randomization and on the day after treatment was discontinued. At the end of the study, there were no differences in plasma levels of atrial natriuretic peptide between the two treatment groups. Angiotensin-converting enzyme activity was suppressed and plasma renin activity was higher in the trandolapril group. No differences in plasma levels of N-terminal pro-atrial natriuretic peptide, brain natriuretic peptide, aldosterone, noradrenaline, adrenaline, vasopressin, big endothelin-1 and neuropeptide Y were found between the two treatment groups. There were positive correlations between several markers of neurohormonal activation at baseline and variables expressing left ventricular dysfunction and clinical heart failure. Neurohormonal activation is related to left ventricular dysfunction. The effects of 2-3 weeks of angiotensin-converting enzyme inhibition on neurohormonal activation does not predict the already established beneficial long-term effects after myocardial infarction. Thus, early modulation of circulatory neurohormone levels may not be a major mechanism for the efficacy of angiotensin-converting enzyme inhibitors in these patients. Selected plasma hormone markers may still be used to identify patients who might get the greatest benefit from treatment.

[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.

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.

Alveolar epithelial fluid transport and the resolution of clinically severe hydrostatic pulmonary edema

To characterize the rate and regulation of alveolar fluid clearance in the uninjured human lung, pulmonary edema fluid and plasma were sampled within the first 4 h after tracheal intubation in 65 mechanically ventilated patients with severe hydrostatic pulmonary edema. Alveolar fluid clearance was calculated from the change in pulmonary edema fluid protein concentration over time. Overall, 75% of patients had intact alveolar fluid clearance (>/=3%/h). Maximal alveolar fluid clearance (>/=14%/h) was present in 38% of patients, with a mean rate of 25 +/- 12%/h. Hemodynamic factors (including pulmonary arterial wedge pressure and left ventricular ejection fraction) and plasma epinephrine levels did not correlate with impaired or intact alveolar fluid clearance. Impaired alveolar fluid clearance was associated with a lower arterial pH and a higher Simplified Acute Physiology Score II. These factors may be markers of systemic hypoperfusion, which has been reported to impair alveolar fluid clearance by oxidant-mediated mechanisms. Finally, intact alveolar fluid clearance was associated with a greater improvement in oxygenation at 24 h along with a trend toward shorter duration of mechanical ventilation and an 18% lower hospital mortality. In summary, alveolar fluid clearance in humans may be rapid in the absence of alveolar epithelial injury. Catecholamine-independent factors are important in the regulation of alveolar fluid clearance in patients with severe hydrostatic pulmonary edema.

Tumor necrosis factor-alpha upregulates angiotensin II type 1 receptors on cardiac fibroblasts

Angiotensin II (Ang II) plays an important role in post-myocardial infarction (MI) remodeling. Most Ang II effects related to remodeling involve activation of the type 1 receptor (AT(1)). Although the AT(1) receptor is upregulated on cardiac fibroblasts post-MI, little is known about the mechanisms involved in the process. Consequently, we tested whether growth factors known to be present in the remodeling heart increased AT(1) mRNA levels. Using quantitative competitive reverse transcription-polymerase chain reaction, we found that norepinephrine, endothelin, atrial natriuretic peptide, and bradykinin had no significant effect on AT(1) mRNA levels. Ang II, transforming growth factor-beta(1), and basic fibroblast growth factor reduced AT(1) mRNA levels (P<0.02). Tumor necrosis factor-alpha (TNF-alpha), however, produced a marked increase in AT(1) mRNA. After 24 hours of TNF-alpha incubation, AT(1) mRNA increased by 5-fold above control levels (P<0.01). The EC(50) for the TNF-alpha effect was 4.6 ng/mL (0.2 nmol/L). Interleukin (IL)-1beta caused a 2.4-fold increase, whereas IL-2 and IL-6 had no significant effect. Studies of TNF-alpha enhancement of AT(1) mRNA levels demonstrate that the increase was not due to a change in transcript stability. TNF-alpha treatment for 48 hours also resulted in a 3-fold increase in AT(1) surface receptor and a 2-fold increase in Ang II-induced production of inositol phosphates. The present findings provide evidence for TNF-alpha regulation of AT(1) receptor density on cardiac fibroblasts. Because TNF-alpha concentration and AT(1) receptor density increase in the myocardium after MI, these results raise the possibility that TNF-alpha modulates post-MI remodeling by enhancing Ang II effects on cardiac fibroblasts.

QT dispersion as a predictor of long-term mortality in patients with acute myocardial infarction and clinical evidence of heart failure

BACKGROUND

QT interval dispersion is a marker of inhomogeneous ventricular repolarization, and therefore has the potential to predict re-entry arrhythmias. Following acute myocardial infarction, increased QT dispersion has been associated with a higher risk of ventricular arrhythmias. However, whether or not QT dispersion predicts prognosis post-acute myocardial infarction is not clear. We addressed this issue by analysing the AIREX study registry.

METHODS

AIREX was a follow-up study of 603 post-acute myocardial infarction patients who exhibited clinical signs of heart failure and were randomly allocated to ramipril or placebo. An interpretable 12-lead ECG obtained between day 0 and day 9 after the index infarction (median time 2 days) was available in 501 patients. We examined whether QT dispersion was a predictor of all-cause mortality in the AIREX study registry (mean follow-up 6 years).

RESULTS

QT dispersion measurements were significantly increased in patients who subsequently died (QT dispersion: 92.0 +/- 38.5 ms vs 82.7 +/- 34.3 ins. P=0.005; rate corrected QT dispersion: 105.7 +/- 42.7 ms vs 93.1 +/- 35.9 ms, P<0.001). Univariate analysis showed that QT dispersion as a predictor of all-cause mortality risk (QT dispersion: hazard ratio per l0 ms 1.05, [95% CI 1.02 to 1.09]. P= 0.004; rate corrected QT dispersion: 1-07 [1.03 to 1.10], P<0.001): an increase of 10 ms added a 5-7%, relative risk of death. QT dispersion remained an independent predictor of all-cause mortality risk on multivariate analysis (QT dispersion: 1.05 [1.01 to 1.09], P=0.027; rate corrected QT dispersion: 1.05 [1.01 to 1.09]. P=0.022).

CONCLUSION

QT dispersion. measured from Li routine 12-lead ECG following acute myocardial infarction complicated by heart failure provides independent information regarding the probability of long-term survival. However. the low sensitivity of this electrocardiographic marker limits its usefulness for risk stratification if used in isolation.

Active renin and angiotensinogen in cardiac interstitial fluid after myocardial infarction

The renin-angiotensin system promotes cardiac hypertrophy after myocardial infarction. The purpose of this study was to measure renin and angiotensinogen in plasma and myocardium 10 days after myocardial infarction. Infarction involving 45 +/- 4% of left ventricular circumference with accompanying hypertrophy was induced in rats (n = 14). Plasma and myocardial renin were increased after infarction compared with sham controls (n = 8) (27.4 +/- 3.2 vs. 7.5 +/- 1.8 ng ANG I. ml plasma. h-1, P < 0.0002; and 8.8 +/- 1.6 vs. 2. 5 +/- 0.1 ng ANG I. g myocardium-1. h-1, P < 0.008, respectively). After infarction, myocardial renin was correlated with infarct size (r = 0.62, P < 0.02) and plasma renin (r = 0.55, P < 0.04). Plasma angiotensinogen decreased in infarct animals, but myocardial angiotensinogen was not different from shams (1.1 +/- 0.08 vs. 2.03 +/- 0.06 nM/ml plasma, P < 0.002; and 0.081 +/- 0.008 vs. 0.070 +/- 0.004 nM/g myocardium, respectively). In conclusion, myocardial renin increased after infarction in proportion to plasma renin and infarct size, and myocardial angiotensinogen was maintained after infarction despite decreased plasma angiotensinogen and increased levels of myocardial renin.

How to assess sympathetic activity in humans

Sympathetic factors play a central role not only in cardiovascular homeostatic control but also in the pathogenesis and/or in the progression of several cardiovascular diseases, such as essential hypertension, myocardial infarction, cardiac arrhythmias and congestive heart failure. This explains why assessment of adrenergic neural function in humans has been, and certainly still remains, one of the major fields in cardiovascular research. The present paper will review in detail the haemodynamic, pharmacological, biochemical, neurophysiological, neurochemical and neural imaging techniques by which sympathetic activity is assessed in humans, highlighting the main advantages and limitations of each of them. Although plasma noradrenaline measurement represents a useful guide to assess sympathetic neural function, direct recording of sympathetic nerve traffic via microneurography and noradrenaline radiotracer methods have in recent years largely supplanted the plasma noradrenaline approach. This is because they allow (1) discrimination between the central or peripheral nature of increased plasma noradrenaline levels, and (2) precise estimation of the behaviour of regional sympathetic neural function both under physiological and pathological conditions. In contrast, the approach based on spectral analysis of heart rate and blood pressure signals has been shown to have important limitations which prevent the method from faithfully reflecting sympathetic cardiovascular drive. Neural imaging techniques, which require expensive technical support, allow direct visualization of sympathetic enervation of human organs, thus providing information on the 'in vivo' metabolism of noradrenaline in different cardiovascular districts. Although technical improvements have allowed a more precise assessment of human adrenergic function, no technique so far available can be viewed as a 'gold standard' with which the others might be compared. Limitations and disadvantages of the various techniques may be reduced if these methods are seen as being complementary and employed in combination, allowing more reliable information to be achieved on the sympathetic abnormalities characterizing cardiovascular diseases, and thus hopefully providing a stronger rationale for newer therapeutic approaches involving pharmacological modification of the sympathetic nervous system and adrenoreceptors.

Changes in cardiac ANG II postmyocardial infarction in rats: effects of nephrectomy and ACE inhibitors

We evaluated in rats the time course of changes in cardiac versus plasma ANG I and II postmyocardial infarction (MI) and the effects of nephrectomy and angiotensin-converting enzyme (ACE) inhibitors on the early changes post-MI. Acute coronary artery ligation was induced in conscious rats using the two-stage model, and plasma and cardiac tissue were obtained shortly (6 h, 1 and 3 days) and chronically (1, 4, and 8-9 wk) after MI. In an additional group of rats, bilateral nephrectomy was performed 18 h before the coronary artery ligation, and samples were obtained at 6 h post-MI. Furthermore, in two additional groups of rats, treatment with enalapril and quinapril was started 3 days before the ligation, and samples were obtained at 1 or 3 days post-MI. In these groups of rats, plasma and left ventricular (LV) (infarct and infarct free) ANG I and II were measured by RIA after separation on HPLC. In control rats, plasma ANG I and II showed a clear increase at 6 h post-MI but subsequently only minor increases were observed. In contrast, LV ANG II showed major increases at 6 h and 1 day post-MI, which had returned to normal by 3 days in the infarct-free LV and after 1(-2) wk in the infarct LV. LV ANG I showed a more gradual increase and remained elevated in the infarct up to 8-9 wk. Nephrectomy preceding the MI lowered ANG I and II in plasma but enhanced their increases in the heart at 6 h post-MI. Both ACE inhibitors decreased plasma ANG II associated with large increases in plasma ANG I. They also inhibited the increases in LV ANG II in both the infarct and infarct-free LV at 1 and 3 days post-MI with however no significant increase in LV ANG I. In conclusion, induction of a MI in conscious rats leads to rapid and marked, but only short-lived, increases in cardiac tissue ANG II in both the infarct and infarct-free parts of the LV. Pretreatment with ACE inhibitors, but not nephrectomy, blocks this increase. Local production appears to play a major role in the increases in cardiac ANG II post-MI.

Time-related adaptations in plasma neurohormone levels and hemodynamics after myocardial infarction in the rat

BACKGROUND

Neurohormonal activation plays an important role in the progression of heart failure. In this study, we investigated the progression of neurohormonal activation in conjunction with the hemodynamic status of the rat after myocardial infarction (MI).

METHODS AND RESULTS

Male Wistar rats were subjected to sham or MI surgery. At 1, 3, 5, and 13 weeks after surgery, cardiac output (CO), mean arterial pressure (MAP), and total peripheral resistance (TPR), were measured. In separate groups of rats, blood was sampled at 1, 5, and 13 weeks after surgery and analyzed for various neurohormones. At 1 week after surgery, CO and TPR were not altered in MI rats, but plasma neurohormonal levels were elevated. At 3 and 5 weeks after surgery, reduced CO, increased TPR, and normal MAP were measured in MI rats compared to sham rats, but only endothelin levels were elevated. At 13 weeks after surgery, MAP was reduced in MI rats and CO and TPR were comparable between groups. Neurohormonal activation was again apparent in MI rats.

CONCLUSIONS

Myocardial infarction in the rat induces early neurohormonal activation, which normalizes hemodynamic parameters. A compensatory phase follows. At 13 weeks after MI, plasma concentrations of neurohormones are again elevated, perhaps as a sign of transition to decompensation.

Plasma N-terminal atrial natriuretic factor: a predictor of survival in patients with congestive heart failure

BACKGROUND

Congestive heart failure results in biatrial stretch, which stimulates myocyte release of atrial natriuretic factor (1-126). The N-terminal fragment, proatrial natriuretic factor(1-98), (proANF), is released on an equimolar basis with the C-terminal (99-126) active hormone and may be assayed simply because of prolonged in vitro stability. Proatrial natriuretic factor has been shown to be predictive of clinical status in patients with congestive heart failure. This retrospective analysis was undertaken to evaluate the relationship between N-terminal atrial natriuretic factor(1-98) and survival in patients with stable congestive heart failure.

METHODS AND RESULTS

Proatrial natriuretic factor was sampled from 316 patients (mean age, 68 (+/-) 11 years; 71% men) recruited from an outpatient heart failure clinic. The mean ejection fraction was 34 (+/-) 13%. Seventy-three deaths were registered during the period of data collection (42 months). Deaths per proANF quartile (n = 79) were as follows: 2 (2.5%) in quartile I. 13 (16.5%) in quartile II, 21 (26.6%) in quartile III, and 37 (46.8%) in quartile IV. The odds ratio estimates for death adjusted for age and sex were 7.6, 13.9, and 33.9 for the second, third, and fourth quartiles, respectively. Survival curves constructed according to proANF quartiles demonstrate significant differences in mortality rates. The correlation with death was greater for proANF as compared with left ventricular end-diastolic diameter (P < .001), systolic pulmonary artery pressure (P < .005), or ejection fraction (P < .05).

CONCLUSION

These data indicate that the concentration of proANF is related to prognosis in patients with heart failure and that moderate elevation is associated with markedly decreased survival. Analysis should be of practical value in the assessment of prognosis in this heterogeneous population.

Changes of the left ventricle after myocardial infarction--estimation with cine magnetic resonance imaging during the first six months

BACKGROUND

In recent years, the interest of cardiologists has focused increasingly on the morphologic and functional changes of the left ventricle after myocardial infarction (MI), due to their great prognostic significance for the patient.

HYPOTHESIS

The aim of this study was to evaluate changes in left ventricular morphology and function during the first 6 months following MI.

METHODS

In all, 61 patients (17 women, 44 men, age 36-83 years) were examined with cine magnetic resonance imaging (CMRI) 1, 4, and 26 weeks after myocardial infarction. Thirty-two patients had anterior MI and 29 patients had posterior MI. According to enzyme-derived infarct weight, 15 patients had small infarcts (< 20 g), 19 had intermediate-sized infarcts (20-40 g), and 27 patients had large infarcts (> 40 g). CMRI was performed in the true short axis of the left ventricle. In each examination, left ventricular end-diastolic and end-systolic volume indices (LVEDVI, LVESVI), stroke volume index (LVSVI), ejection fraction (LVEF), and regional thickness, mass, and motility of the myocardial wall-diastolic thickness (IDdia), infarct mass (IM) and motility (IMOT) of the infarct area and diastolic and systolic thickness (VDdia, VDsys), muscular mass (VM), and motility (VMOT)-were determined. In addition, patients were divided into subgroups according to New York Heart Association (NYHA) functional status at baseline.

RESULTS

In the total group, LVEDVI increased from 73.9 +/- 23.5 ml/m2 to 85.4 +/- 28.1 ml/m2 (p < 0.001) and LVESVI from 40.5 +/- 19.4 ml/m2 to 51.2 +/- 29.0 ml/m2 (p < 0.001). In the subgroups the development depended on infarct size and location. LVSVI and LVEF remained more or less constant except for large anterior infarctions. All changes of the myocardial wall depended on infarct size and location: In all patients IDdia decreased from 10.4 +/- 1.6 mm to 8.9 +/- 1.7 mm (p < 0.001), IMOT from 2.0 +/- 1.6 mm to 0.5 +/- 2.9 mm (p < 0.001). IM increased from 41 +/- 21 g to 45 +/- 25 g (p < 0.001). In the total group, VDdia increased from 11.9 +/- 1.6 mm to 12.4 +/- 1.8 mm (p < 0.05), VDsys from 16.6 +/- 2.5 mm to 17.2 +/- 3.1 mm (p < 0.05). In the subgroups changes varied: VDdia and VDsys decreased markedly in large anterior wall infarctions. VM increased in the total cohort from a mean of 246 +/- 66 g to 276 +/- 80 g (p < 0.001). VMOT decreased from 7.1 +/- 2.4 mm to 6.3 +/- 2.7 mm (p < 0.05). Loss of motility was most pronounced in anterior infarctions. The volume-mass ratio, a measure of the success of compensation of volume increase by myocardial hypertrophy, decreased in small infarcts, remained unchanged in intermediate infarcts, and increased in large infarcts. There was a trend toward improvement of the NYHA functional status during the observation period.

CONCLUSIONS

Changes of the left ventricular chamber during the first 6 months following MI are dependent on its size and location, with large anterior infarctions having the worst course. Myocardial wall remodeling is also dependent on infarct size and location, and the volume-mass ratio increases in the presence of large areas of necrosis, indicating the non-compensatory effect of myocardial hypertrophy. However, these changes have no clinical effect during the first half year after MI.

Angiotensin-converting enzyme inhibitor therapy affects left ventricular mass in patients with ejection fraction > 40% after acute myocardial infarction

OBJECTIVES

We tested the hypothesis that angiotensin-converting enzyme (ACE) inhibitor therapy decreases left ventricular (LV) mass in patients with a left ventricular ejection fraction (LVEF) > 40% and no evidence of heart failure after their first acute Q wave myocardial infarction (MI).

BACKGROUND

Recently, ACE inhibitor therapy has been shown to have an early mortality benefit in unselected patients with acute MI, including patients without heart failure and a LVEF > 35%. However, the effects on LV mass and volume in this patient population have not been studied.

METHODS

Thirty-five patients with a LVEF > 40% after their first acute Q wave MI were randomized to titrated oral ramipril (n = 20) or conventional therapy (control, n = 15). Magnetic resonance imaging (MRI) performed an average of 7 days and 3 months after MI provided LV volumes and mass from summated serial short-axis slices.

RESULTS

Left ventricular end-diastolic volume index did not change in ramipril-treated patients (62 +/- 16 [SD] to 66 +/- 17 ml/m2) or in control patients (62 +/- 16 to 68 +/- 17 ml/m2), and stroke volume index increased significantly in both groups. However, LV mass index decreased in ramipril-treated patients (82 +/- 18 to 73 +/- 19 g/m2, p = 0.0002) but not in the control patients (77 +/- 15 to 79 +/- 23 g/m2). Systolic arterial pressure did not change in either group at 3-month follow-up.

CONCLUSIONS

In patients with a LVEF > 40% after acute MI, ramipril decreased LV mass, and blood pressure and LV function were unchanged after 3 months of therapy. Whether the decrease in mass represents a sustained effect that is associated with a decrease in morbid events requires further investigation.

Increased plasma adrenomedullin in acute myocardial infarction

Adrenomedullin has a potent vasodilating effect comparable to that of calcitonin gene-related peptide. To investigate the pathophysiologic role of endogenous adrenomedullin, we determined sequentially the plasma adrenomedullin level in 15 consecutive patients with acute myocardial infarction (AMI). Plasma adrenomedullin was higher immediately after the onset of AMI and decreased gradually; plasma levels during the 3-week period after the AMI were higher than plasma levels in 15 healthy control subjects (p < 0.001), with higher levels in patients with congestive heart failure than in patients without congestive heart failure throughout the period of the study (p < 0.05). Plasma adrenomedullin was positively correlated with pulmonary capillary wedge pressure, pulmonary arterial pressure, right atrial pressure, and heart rate in the early stage of AMI. These findings suggest that the elevation of plasma adrenomedullin is related to the retention of body fluid volume, the enhancement of sympathetic activity, and/or the elevation of pressure in pulmonary vascular beds. Adrenomedullin may act against excessive vasoconstrictors increased in AMI.

Mechanisms of subcellular remodelling in post-infarct heart failure

Occlusion of a coronary artery results in myocardial ischemia and subsequent myocardial infarction. Whenever the infarct size is more than 30% of the ventricular wall, the remaining myocardium attempts to compensate for the loss of muscle mass by changing the size and shape of cardiocytes in addition to developing cardiac hypertrophy, cardiac dilatation and congestive heart failure. This remodeling of the heart is associated with changes in the extracellular matrix including collagen proteins and is most probably due to the activation of both sympathetic nervous system and renin-angiotensin system as well as increased formation of various growth factors. Alterations in contractile function of the infarcted heart are associated with remodelling of the sarcoplasmic reticulum with respect to Ca(2+)-pump and Ca(2+)-release channels as well as contractile and regulatory proteins of the myofibrils. Myocardial infarction has also been shown to result in remodelling of the sarcolemmal membrane with respect to Ca(2+)-channels, Ca(2+)-transport systems, cardiac receptors and signal transduction mechanisms. Although information regarding remodelling of mitochondria in the infarcted heart is limited, alterations in energy yielding and Ca(2+)-accumulating systems are suspected. Accordingly, it is suggested that changes in cardiac contractile dysfunction due to myocardial infarction are associated with remodeling of both extracellular matrix and subcellular organelles in the heart.

Plasma proatrial natriuretic factor is predictive of clinical status in patients with congestive heart failure

Atrial stretch results in myocyte release of the prohormone atrial natriuretic factor (1-126). The N-terminal (1-98) fragment, proatrial natriuretic factor (proANF) is released on an equimolar basis with the C-terminal (99-126) active hormone and may be assayed simply due to in vitro stability. This study was undertaken to evaluate the relation between proANF and routinely available measures of clinical status. ProANF was sampled from 202 patients (median age 68 years [range 15 to 85], 77% men) recruited from an active outpatient heart failure clinic. Patients were subgrouped according to New York Heart Association functional class, radionuclide ejection fraction (EF), echocardiographic left ventricular (LV) end-diastolic diameter, and Doppler-determined systolic pulmonary arterial pressure. The median proANF (pmol/L) values for patients in New York Heart Association classes I, II, III, IV were 725, 1,527, 1,750, and 5,172, respectively. The proANF value for the group with EF > 40% was 1,534 versus 1,993 for EF < or = 40% (p < 0.05). The value for the group with LV diameter < 60 mm ws 838 versus 1,751 for LV diameter > or = 60 mm (p < 0.01). The value for the group with systolic pulmonary artery pressure < 45 mm Hg was 1,241 versus 2,660 for systolic pulmonary artery pressure > or = 45 mm Hg (p < 0.01). ProANF correlated better than the other variables with New York Heart Association functional class and was more closely associated with noninvasive measurements than New York Heart Association functional class.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of enalapril on T and B cell function in rats after myocardial infarction

The cellular mechanisms following myocardial infarction remain poorly characterized. It is believed that an inflammatory and immunologic process may be involved and that the beneficial effects of enalapril on remodeling may, in part, work through an immune mechanism. To characterize the effect of enalapril on immune alterations in the late phase of ventricular remodeling after myocardial infarction, rats underwent left coronary artery ligation followed by 6 weeks of either enalapril or placebo treatment. Infarct sizes, heart weights, and volumes were compared. Peripheral and splenic leukocyte and lymphocyte subsets, along with T cell blastogenesis, were quantified in enalapril treated rats 6 weeks after coronary ligation and compared to untreated control rats. Additionally, antibody production to a de novo antigen, keyhole limpet hemocyanin, was assessed with and without treatment. Average infarct size was equivalent among enalapril-treated myocardial infarction rats and untreated infarct rats. There was, however, less left and right ventricular hypertrophy in the enalapril treated group. Enalapril completely prevented the 42% increase in white blood count, the 88% increase in neutrophils, and the 28% increase in lymphocyte count seen in untreated infarct rats. Both untreated and enalapril treated rats tended toward a decrease in T helper:suppressor ratio. All rats treated with enalapril, however, had a significant increase in the T helper:suppressor ratio versus untreated control rats (F = 3.6, P = .018). Blastogenesis was markedly increased in T cells from infarcted animals. This was mitigated by treatment with enalapril. Additionally, immunoglobulin G antibody production was significantly lessened in rats treated with enalapril. The results of this study suggest that alterations in immunoregulatory cell type and function occurs following myocardial infarction. The beneficial effects of the angiotensin-converting enzyme inhibitor enalapril may be, in part, due to its mitigating effects on immune cell release and activation following myocardial infarction.