Mechanisms and implications of autonomic nervous system dysfunction in heart failure

Association between beta-adrenoceptor antagonist-induced sympathicolysis and severity of coronary artery disease as assessed by coronary computed tomography angiography (CCTA)

Enhanced sympathetic nervous system activity is associated with increased mortality in many cardiac conditions including heart failure and coronary artery disease (CAD). To ensure adequate image quality of coronary CT angiography (CCTA), pre-scan β-adrenergic blockers (BB) are routinely administered. It is currently unknown whether sensitivity to sympathicolytic compounds is associated with severity of CAD. A total of 2633 consecutive patients (1733 [65.8%] men and 900 [34.2%] women, mean age 56.7 ± 11.5 years) undergoing CCTA for exclusion of significant CAD at our department between 06/2013 and 12/2016 were evaluated. Acute heart rate (HR) responses to BB administration were recorded in all patients. Coronary plaque burden as indicated by segment severity score (SSS), segment involvement score (SIS), and significant CAD (i.e. > 50% luminal narrowing) was higher in weak responders to BB as compared to strong responders to BB (p = 0.001 for SSS and SIS, and p = 0.021 for significant CAD). Accordingly, in a multiple linear regression model adjusted for known risk factors of CAD such as smoking, hypertension, diabetes and dyslipidaemia, as well as age, sex, body mass index (BMI), glomerular filtration rate, and HR during CCTA scan, a strong response to BB was selected as a significant independent negative predictor of coronary plaque burden (beta coefficient - 0.08, p = 0.001). We demonstrate that individuals with a weak acute response to BB administration encounter an increased risk of severe CAD. Taking into account sensitivity to sympatho-inhibition may add complementary information in patients undergoing CCTA for evaluation of CAD.

The Identification of Malnutrition in Heart Failure Patients

Heart failure (HF) is the only cardiovascular disease that is increasing in incidence, prevalence, and mortality. One of the major complications associated with HF is malnutrition. Fluctuations due to fluid make weight measurement an inaccurate parameter to identify malnutrition. Therefore, the purpose of this study is to assess clinical parameters that could assist in the recognition of malnutrition in HF patients. A convenience sample of 50 HF patients had anthropometric measurements, a review of their serum chemistry levels, a collection of standard hemodynamic measures plus electrical bioimpedance, and, each subject completed a gastrointestinal symptoms assessment with two meals. Eighteen (36%) subjects were classified as malnourished based on the selected criteria of a serum albumin <3.0 g/dl and/or being less than 90% of ideal body weight. Within this sample of malnourished subjects, 44% of the subjects were found to be obese based on skinfold measurement. A comparison between malnourished/not malnourished groups found that the mean heart rate was higher in the malnourished group (85 vs. 73 beats/min; P<0.017). There were no other parameters that differentiated between these groups. These results demonstrate the need for further research to identify predictive clinical parameters for malnutrition in this vulnerable population.

Terminalia arjuna enhances baroreflex sensitivity and myocardial function in isoproterenol-induced chronic heart failure rats

Chronic heart failure (CHF) is characterized by left ventricular (LV) dysfunction along with impaired autonomic control functions. Herbal drugs are increasingly being used in the treatment of cardiovascular disorders. The present study was designed to examine the protective effect of Terminalia arjuna (T arjuna) bark extract on LV and baroreflex function in CHF and to elucidate the possible mechanistic clues in its cardioprotective action. The baroreflex was evaluated by measuring the changes in heart rate (HR) with changes in arterial blood pressure induced by bolus injections of phenylephrine (vasoconstrictor) and sodium nitroprusside (vasodilator). T arjuna bark extract and fluvastatin were tested/administered therapeutically and prophylactically in isoproterenol-induced rat model of CHF. Fifteen days after isoproterenol administration, rats exhibited cardiac dysfunction, hypertrophy, and LV remodeling along with reduced baroreflex sensitivity. Prophylactic and therapeutic treatment with T arjuna improved cardiac functions and baroreflex sensitivity. It also attenuated hypertrophy and fibrosis of the LV. Fluvastatin treatment exerted a similar protective effect against myocardial remodeling and heart failure. Further, T arjuna and fluvastatin significantly reduced oxidative stress and inflammatory cytokine level in CHF rats. In conclusion, T arjuna exerts beneficial effect on LV functions, myocardial remodeling, and autonomic control in CHF possibly through maintaining endogenous antioxidant enzyme activities, inhibiting lipid peroxidation and cytokine levels.

Comparison of myocardial performance index versus ratio of isovolumic contraction time/ejection time in left ventricular systolic dysfunction

Myocardial performance index (MPI) has been regarded as an important parameter in the evaluation of ventricular systolic function in congestive heart failure. This study was designed to investigate the relationship between the ratio of isovolumic contraction time/left ventricular ejection time (IVCT/LVET), MPI, and LV systolic function. A total of 43 patients (patient group) with LV ejection fractions (LVEFs) <55% were compared with 43 patients (control group) with LVEF values >or=55%. LVEF was measured in all cases by 2-dimensional echocardiography via the modified Simpson method. Isovolumic relaxation time (IVRT), IVCT, LVET, ratio of IVCT/LVET, and MPI ([IVRT+IVCT]/LVET) were measured via Doppler echocardiography. The mean value for IVCT was found to be significantly higher (P<.001) and concomitant mean LVET value significantly lower (P=.027) in the patient group. Similarly, the mean value of MPI and the ratio of IVCT/LVET were found to be significantly higher (P<.001 for both) in the patient group. The value of the ratio of IVCT/LVET was found to have a significant negative correlation with the value of LVEF (r=-.947; P<.001) and a significant positive correlation with the value of MPI (r=.796; P<.001). The study reported here clearly demonstrates the noninferiority of the ratio of IVCT/LVET to MPI and the possibility of its substitution for MPI in the evaluation of LV systolic function.

Design and features of the Acorn CorCap Cardiac Support Device: the concept of passive mechanical diastolic support

The Laplace equation points to the importance of ventricular wall stress as a factor in heart failure development and progression. Based on animal and clinical experience with active and passive cardiomyoplasty, a synthetic passive constraint was proposed as a means of reducing excessive wall stress, and thus assuaging disease progression. The Acorn CorCap CSD Cardiac Support Device was designed to provide passive diastolic support and serve as a constraint against chronic cardiac dilation in heart failure. Basic and uncomplicated in appearance, the device nevertheless incorporates numerous sophisticated structural and functional features intended maximize therapeutic value. The device is fabricated from medical grade multifilament polyester yarn, in a specific knit construction chosen to provide structural integrity, low physical profile, pliability for intimate contact with the epicardial surface, ease of manipulation during implantation, and anisotropic compliance characteristics to encourage beneficial reverse remodeling.

Impact of 6 months of therapy with carvedilol on muscle sympathetic nerve activity in heart failure patients

BACKGROUND

The long-term effects of carvedilol on muscle sympathetic nerve activity (MSNA) and muscle blood flow at rest and exercise in patients with chronic heart failure (CHF) remain unknown.

METHODS AND RESULTS

Twenty-six patients (New York Heart Association class II-III) were randomized to carvedilol or placebo. Blood pressure, heart rate, MSNA, and forearm vascular resistance (FVR) at rest and during isometric forearm exercise (10% and 30% maximal voluntary contraction) were assessed before and after 6 months. Seven patients did not complete the study. Paired data were obtained in 19 (carvedilol 12, placebo 7). Carvedilol significantly decreased MSNA levels and heart rate at rest (-13 +/- 2 versus 3 +/- 8 bursts/min, P = .0001 and -16 +/- 3 vs -4 +/- 6 bpm, P = .05, respectively) and peak exercise (30% = -20 +/- 5 versus -3 +/- 7 bursts/min, P = 0.05 and -19 +/- 4 versus -4 +/- 6 bpm, P = 0.03, respectively) when compared with placebo. Carvedilol did not change a magnitude of response of MSNA and heart rate during exercise (-10 +/- 3 versus -7 +/- 2 bursts/min, P = 0.7 and 11 +/- 3 versus 6 +/- 1, P = .6, respectively). FVR was unchanged by carvedilol. When MSNA was quantified by burst incidence, the strength of reduction in MSNA was attenuated but still greater than placebo.

CONCLUSIONS

Carvedilol reduces MSNA in patients with CHF. Carvedilol does not reduce FVR at rest or during isometric exercise.

Carnitine palmitoyltransferase-I, a new target for the treatment of heart failure: perspectives on a shift in myocardial metabolism as a therapeutic intervention

Although the heart is capable of extracting energy from different types of substrates such as fatty acids and carbohydrates, fatty acids are the preferred fuel under physiological conditions. In view of the presence of diverse defects in myocardial metabolism in the failing heart, changes in metabolism of glucose and fatty acids are considered as viable targets for therapeutic modification in the treatment of heart failure. One of these changes involves the carnitine palmitoyltransferase (CPT) enzymes, which are required for the transfer of long chain fatty acids into the mitochondrial matrix for oxidation. Since CPT inhibitors have been shown to prevent the undesirable effects induced by mechanical overload, e.g. cardiac hypertrophy and heart failure, it was considered of interest to examine whether the inhibition of CPT enzymes represents a novel approach for the treatment of heart disease. A shift from fatty acid metabolism to glucose metabolism due to CPT-I inhibition has been reported to exert beneficial effects in both cardiac hypertrophy and heart failure. Since the inhibition of fatty acid oxidation is effective in controlling abnormalities in diabetes mellitus, CPT-I inhibitors may also prove useful in the treatment of diabetic cardiomyopathy. Accordingly, it is suggested that CPT-I may be a potential target for drug development for the therapy of heart disease in general and heart failure in particular.

Linguistic analysis of the human heartbeat using frequency and rank order statistics

Complex physiologic signals may carry unique dynamical signatures that are related to their underlying mechanisms. We present a method based on rank order statistics of symbolic sequences to investigate the profile of different types of physiologic dynamics. We apply this method to heart rate fluctuations, the output of a central physiologic control system. The method robustly discriminates patterns generated from healthy and pathologic states, as well as aging. Furthermore, we observe increased randomness in the heartbeat time series with physiologic aging and pathologic states and also uncover nonrandom patterns in the ventricular response to atrial fibrillation.

Increased cardiac sympathetic drive in renovascular hypertension

BACKGROUND

Patients with renovascular hypertension (RVH) have high cardiovascular mortality and morbidity. In these patients, overall sympathetic nerve activity is increased. It is unknown, however, whether this increase also involves the heart.

OBJECTIVE

We tested the hypothesis that cardiac sympathetic activity is increased in patients with hypertension and renal artery stenosis.

METHODS AND RESULTS

A total of 14 patients with hypertension were studied before angioplasty of angiographically identified renal artery stenosis. Nine out of 14 patients had renovascular hypertension proven at the 1-year follow-up visit. A total of 19 healthy subjects served as a control group. A right heart catheterization, including the positioning of a coronary sinus thermodilution catheter was performed for hemodynamic recordings and blood sampling. Using a radiotracer dilution technique with infusion of tritiated noradrenaline ([3H]NA) and adrenaline ([3H]A), fractional extraction and clearance were calculated. Total body and cardiac NA spillovers were used as indices of systemic and cardiac sympathetic nervous activity. The study group had normal left ventricular ejection fraction and cardiac pressures. Cardiac NA spillover was increased by 127% in the hypertensive patients compared with healthy subjects (200 +/- 53 versus 88 +/- 10 pmol/min in controls, P < 0.05). Total body NA spillover was similar in both groups. Cardiac fractional extraction of [3H]NA and [3H]A was decreased by 26 and 47%, respectively, compared with normotensive subjects (P < 0.01 for both).

CONCLUSIONS

Patients with renovascular hypertension have altered cardiac sympathetic function with increased sympathetic drive and impaired catecholamine extraction. The increased cardiac sympathetic drive may have adverse long-term effects on prognosis in this patient group with high cardiovascular mortality.

Increased baroreceptor response in mice deficient in monoamine oxidase A and B

The recent development of mice doubly deficient for monoamine oxidase A and B (MAO-A/B, respectively) has raised questions about the impact of these mutations on cardiovascular function, in so far as these animals demonstrate increased tissue levels of the vasoactive amines serotonin, norepinephrine, dopamine, and phenylethylamine. We recorded femoral arterial pressures and electrocardiograms in adult MAO-A/B-deficient mice during halothane-nitrous oxide anesthesia as well as 30 min postoperatively. During both anesthesia and recovery, systolic, diastolic, and mean arterial pressures were 10-15 mmHg lower in MAO-A/B-deficient mice compared with normal controls (P < 0.01). Mutants also showed a greater baroreceptor-mediated reduction in heart rate in response to hypertension after intravenous pulses of phenylephrine or angiotensin II. Tachycardia elicited in response to hypotension after nitroprusside was greater in mutants than in controls. Heart rate responsiveness to changes in arterial pressure was abolished after administration of glycopyrrolate, with no differences in this phenomenon noted between genotypes. These data suggest that prevention of hypertension may occur in chronic states of catecholaminergic/indoleaminergic excess by increased gain of the baroreflex.

Continual recordings of cardiac sympathetic nerve activity in conscious sheep

Cardiac sympathetic nerve activity (CSNA) is of major importance in the etiology of heart disease but is impossible to measure directly in humans. Ovine and human cardiovascular systems are similar; therefore, we have developed a method for the daily recording of CSNA in conscious sheep. After thoracotomy, electrodes were glued into the left thoracic cardiac nerve and CSNA, blood pressure (BP), and heart rate were recorded daily. Satisfactory recordings > or =7 days of CSNA were obtained in 11 of 28 sheep (40%), mean recording time 10.6 days, range 7-47. During the first week, CSNA decreased gradually from 78 +/- 8 at baseline to 60 +/- 7 bursts/min on day 5 (P = 0.02) or from 76 +/- 9 to 57 +/- 7 bursts/100 beats on day 7 (P = 0.04). Similarly, BP decreased from 103 +/- 4 to 94 +/- 4 mmHg (P = 0.03). Low-frequency heart rate variability decreased from 0.12 +/- 0.02 to 0.06 +/- 0.02 ms(2) on day 6 (P = 0.004) but was not correlated to CSNA. In conclusion, CSNA that can be continually recorded in conscious sheep decreases during the first week postsurgery and, thereafter, stabilizes. This model should provide valuable insights in future investigations of cardiac disease.

Effects of ACE inhibition and angiotensin II type 1 receptor blockade on cardiac function and G proteins in rats with chronic heart failure

1. Inhibition of the renin-angiotensin system (RAS) improves symptoms and prognosis in heart failure. The experimental basis for these benefits remains unclear. We examined the effects of inhibition of ACE or blockade of angiotensin II type 1 (AT1) receptor on the haemodynamics, cardiac G-proteins, and collagen synthesis of rats with coronary artery ligation (CAL), a model in which chronic heart failure (CHF) is induced. 2. Rats were orally treated with the ACE inhibitor trandolapril (3 mg kg(-1) day(-1)) or the AT1 receptor blocker L-158809 (1 mg kg(-1) day(-1)) from the 2nd to 8th week after CAL. CAL resulted in decreases in the left ventricular systolic pressure and its positive and negative dP/dt, an increase in the left ventricular end-diastolic pressure, and the rightward shift of the left ventricular pressure-volume curve. Long-term treatment with either drug improved these signs of CHF to a similar degree. 3. Cardiac Gsalpha and Gqalpha protein levels decreased, whereas the level of Gialpha protein increased in the animals with CHF. Long-term treatment with trandolapril or L-158809 attenuated the increase in the level of cardiac Gialpha protein of the animals with CHF without affecting Gsalpha and Gqalpha protein levels. Cardiac collagen content of the failing heart increased, whose increase was blocked by treatment with either drug. 4. Exogenous angiotensin I stimulated collagen synthesis in cultured cardiac fibroblasts, whose stimulation was attenuated by either drug. 5. These results suggest that blockade of the RAS, at either the receptor level or the synthetic enzyme level, may attenuate the cardiac fibrosis that occurs after CAL and thus affect the remodelling of the failing heart.

Differentiation in the angiotensin II receptor 1 blocker class on autonomic function

Autonomic function is disordered in cardiovascular disease states such as chronic heart failure (CHF) and hypertension. Interactions between the renin-angiotensin-aldosterone system (RAAS) and the sympathetic nervous system (SNS) may potentially occur at a number of sites. These include central sites (eg, rostral ventrolateral medulla), at the level of baroreflex control, and at the sympathetic prejunctional angiotensin II receptor 1 (AT(1)) receptor, which is facilitatory for norepinephrine release from the sympathetic nerve terminal. Therefore, drugs that block the RAAS may be expected to improve autonomic dysfunction in cardiovascular disease states. In order to test the hypothesis that RAAS inhibition directly reduces SNS activity, a pithed rat model of sympathetic stimulation has been established. In this model, an increase in frequency of stimulation results in a pressor response that is sympathetically mediated and highly reproducible. This pressor response is enhanced in the presence of angiotensin II and is reduced in the presence of nonselective AIIRAs that block both AT(1) and AT(2) receptor subtypes (eg, saralasin). AT(1)-selective antagonists have also been studied in this model, at pharmacologically relevant doses. In one such study, only the AT(1) blocker eprosartan reduced sympathetically stimulated increases in blood pressure, whereas comparable doses of losartan, valsartan, and irbesartan did not. The reason(s) for the differences between eprosartan and other agents of this class on sympathetic modulation are not clear, but may relate to the chemical structure of the drug (a non- biphenyl tetrazole structure that is chemically distinct from the structure of other AIIRAs), receptor binding characteristics (competitive), or unique effects on presynaptic AT(1) receptors.

Baroreflex sensitivity and oxidative stress in adriamycin-induced heart failure

Adriamycin cardiotoxicity is associated with oxidative stress in the presence of globally depressed cardiac function. It is unknown if there is a similar profile with early diastolic changes and how it relates to baroreflex control of circulation. In this study, we evaluated baroreflex control of circulation in adriamycin-treated Wistar rats compared with controls, using invasive blood pressure recording processed by a data acquisition system (CODAS, 1 KHz). Baroreflex sensitivity was evaluated by modulating blood pressure with phenylephrine and sodium nitroprusside. Oxidative stress was quantified by chemiluminescence and by glutathione peroxidase enzyme activity. Diastolic dysfunction was characterized by increased left ventricle end-diastolic pressure in adriamycin-treated rats compared with controls with preserved ascending aortic flow. Baroreflex sensitivity in response to blood pressure elevation and reduction were similar in adriamycin (-2+/-0.27 and -3.19+/-0.56 bpm/mm Hg) and control rats (-1.35+/-0.15 and -2.52+/-0.39 bpm/mm Hg). Chemiluminescence was higher (20450+/-1286 versus 16517+/-1020 counts per second/mg protein) and glutathione peroxidase activity was lower (45.6+/-4.3 versus 76.4+/-6.9 micromol. min(-1). mg(-1) protein) in adriamycin rats compared with controls. Inverse correlations were observed between glutathione peroxidase activity and left ventricle end-diastolic pressure (r=-0.72, P=0.02), between baroreflex sensitivity to phenylephrine and left ventricle end-diastolic pressure (r=-0.77, P=0.004), and between chemiluminescence and baroreflex sensitivity to sodium nitroprusside (r=-0.75, P=0.02), whereas a positive correlation was observed between baroreflex sensitivity to sodium nitroprusside and glutathione peroxidase activity (r=0.7, P=0.04). Thus, adriamycin led to increased left ventricle end-diastolic pressure without changes in baroreflex sensitivity, and associated increased oxidative stress appeared to be related to reduction of reflex control of circulation.

Pathophysiology of pediatric heart failure

Our understanding of the syndrome of heart failure has undergone several revisions, most importantly in the second half of the 20th century. New insights into the mechanisms of diseases offer new, challenging, controversial and sometimes counterintuitive forms of therapy. The development and progression of heart failure results from a complex interplay of hemodynamic and neurohormonal, cellular and genetic factors, rather than simply changes in cardiac function. It is because of this reason that our therapeutic focus can no longer be solely based on supply and demand models. Since the description of the pulsatile nature of the heart function and the flow of blood around a circuit by W. Harvey, numerous new paradigms have been put forward to explain the nature of heart failure. However, no single new model thus far proposed has been able to displace previous ones and successfully dictate therapy. It is the purpose of this manuscript to review the overall current understanding of the heart failure syndrome and how these new ideas may affect our therapeutic approach.

Recent insight into therapy of congestive heart failure: focus on ACE inhibition and angiotensin-II antagonism

One possible intervention to interrupt the deleterious effects of the renin-angiotensin system is suppression of angiotensin II (Ang II) formation by inhibition of angiotensin-converting enzyme (ACE). However, ACE inhibition incompletely suppresses Ang II formation and also leads to accumulation of bradykinin. Angiotensin II type 1 (AT1) receptors are believed to promote the known deleterious effects of Ang II. Therefore, AT1 receptor antagonists have been recently introduced into therapy for hypertension and congestive heart failure (CHF). Although there are significant differences between the effects of AT1 receptor antagonists and ACE inhibitors including the unopposed stimulation of angiotensin II type 2 (AT2) receptors by AT1 receptor antagonists, the discussion of whether ACE inhibitors, AT1 receptor antagonists or the combination of both are superior in the pharmacotherapy of CHF is still largely theoretical. Accordingly, AT1 receptor antagonists are still investigational. Angiotensin-converting enzyme inhibitors remain first line therapy in patients with CHF due to systolic dysfunction. However, in patients not able to tolerate ACE inhibitor induced side effects, in particular cough, AT1 receptor antagonism is a good alternative. In clinical practice, emphasis should be placed on increasing the utilization of ACE inhibitors, as more than 50% of patients with CHF do not receive ACE inhibitors. In addition, the majority of those on ACE inhibitors receive doses lower than the dosage used in the large clinical trials. Although not yet completely proved, it is likely that high doses of ACE inhibition are superior to low doses with respect to prognosis and symptoms.

Heart rate variability in patients with the first and recurrent myocardial infarction

Impairment of heart rate variability (HRV) has been reported in patients after myocardial infarction (MI). However, it is currently unknown whether the similar alterations of autonomic profile that accompany the first MI will evolve after a recurrent MI. Forty male outpatients with a previous first MI (group I) and 20 age-matched male patients with a recurrent MI (group II) were studied and measures of HRV were estimated from 24-hour electrocardiograms. In comparison with group I, group II had significantly higher values of ratio of low- to high-frequency power (6.9 +/- 5.7 vs 3.7 +/- 1.8, respectively, p < 0.05), and a tendency to lower values of all other measures of HRV. We conclude our study indicates that in comparison to group I, group II demonstrated augmented sympathetic drive as assessed by the indices of HRV. The shift toward adrenergic predominance detected after recurrent MI may result from altered afferent feedback from abnormally contracting left ventricular segments to the autonomic modulation of sinus node, or accompany subclinical state of heart failure not readily accessible with hemodynamic measurements.

Endogenous or overexpressed cGMP-dependent protein kinases inhibit cAMP-dependent renin release from rat isolated perfused kidney, microdissected glomeruli, and isolated juxtaglomerular cells

An overactive renin-angiotensin-aldosterone system (RAAS) has a central role in the pathogenesis of hypertension and cardiac hypertrophy, precursors of cardiac failure. Natriuretic peptides and NO acting through their second messenger, cGMP, increase natriuresis and diuresis, and inhibit renin release; however the mechanism by which this inhibition of the RAAS system functions is obscure. We recently reported cloning of the cDNA for type II cGMP-dependent protein kinase (cGK II), elucidated its first known function of inhibiting the cystic fibrosis transmembrane conductance regulator in rat intestine, and initially described its location in rat kidney juxtaglomerular (JG) cells, the ascending thin limb, and the brush border of proximal tubules. Here, we demonstrate inhibition of isoproterenol- or forskolin-stimulated renin release by 8-para-chlorophenylthio-cGMP (8-pCPT-cGMP), a selective activator of cGK, and prevention of this inhibition by a selective inhibitor of cGK, Rp-8-pCPT-cGMPS. In systems of differing complexity, inhibition by 8-pCPT-cGMP was nearly complete in isolated perfused kidney and microdissected afferent arterioles but only approximately 25% in isolated JG cells. Expression of either cGK II or cGK I in JG cells by using adenoviral vectors enhanced the inhibition of forskolin-stimulated renin release by 8-pCPT-cGMP to 50%. Our results indicate that cGK II, and possibly cGK I, can mediate cGMP inhibitory effects on renin release and are physiological components of the cGMP signal transduction system which opposes the RAAS.

Pathophysiology of heart failure update: the role of neurohumoral activation in the progression of heart failure

Understanding the pathophysiologic mechanisms responsible for producing heart failure is necessary before effective treatments can be developed that increase survival and improve quality of life. Recent advances in the treatment of heart failure can be traced directly to improved appreciation of the role of neurohumoral activation in the pathophysiology of heart failure. Initially adaptive, neurohumoral activation ultimately results in a series of overadjustments that actively participate in the progression of heart failure. In this article, the role of neurohumoral activation, ventricular remodeling, and various peripheral vascular abnormalities in the pathophysiology of heart failure are explored.