Cardiac sympathetic nerves as the final common pathway in the induction of adaptive cardiac hypertrophy

Cardiac Morphology, Function, and Left Ventricular Geometric Pattern in Patients with Hypertensive Crisis: A Cardiovascular Magnetic Resonance-Based Study

(1) Background: Altered cardiac morphology and function are associated with increased risks of adverse cardiac events in hypertension. Our study aimed to assess left ventricular (LV) morphology, geometry, and function using cardiovascular magnetic resonance (CMR) imaging in patients with hypertensive crisis. (2) Methods: Patients with hypertensive crisis underwent CMR imaging at 1.5 Tesla to assess cardiac volume, mass, function, and contrasted study. Left ventricular (LV) function and geometry were defined according to the guideline recommendations. Late gadolinium enhancement (LGE) was qualitatively assessed and classified into ischemic and nonischemic patterns. Predictors of LGE was determined using regression analysis. (3) Results: Eighty-two patients with hypertensive crisis (aged 48.5 ± 13.4 years, and 57% males) underwent CMR imaging. Of these patients, seventy-eight percent were hypertensive emergency and twenty-two percent were urgency. Diastolic blood pressure was higher under hypertensive emergency (p = 0.032). Seventy-nine percent (92% of emergency vs. 59% of urgency, respectively; p = 0.003) had left ventricular hypertrophy (LVH). The most prevalent LV geometry was concentric hypertrophy (52%). Asymmetric LVH occurred in 13 (22%) of the participants after excluding ischemic LGE. Impaired systolic function occurred in 46% of patients, and predominantly involved hypertensive emergency. Nonischemic LGE occurred in 75% of contrasted studies (67.2% in emergency versus 44.4% in urgency, respectively; p < 0.001). Creatinine and LV mass were independently associated with nonischemic LGE. (5) Conclusion: LVH, altered geometry, asymmetric LVH, impaired LV systolic function, and LGE are common under hypertensive crisis. LVH and LGE more commonly occurred under hypertensive emergency. Longitudinal studies are required to determine the prognostic implications of asymmetric LVH and LGE in hypertensive crisis.

Factors associated with excess female mortality in obstructive hypertrophic cardiomyopathy

BACKGROUND

Several studies have reported excess female mortality in patients with hypertrophic cardiomyopathy, but the cause is unknown.

AIMS

To compare risk-factors for disease-related death in both sexes in a geographical cohort of patients with obstructive hypertrophic cardiomyopathy (oHCM).

METHODS AND RESULTS

Data-bases in all ten hospitals within West Götaland Region yielded 250 oHCM-patients (123 females, 127 males). Mean follow-up was 18.1 y. Risk-factors for disease-related death were evaluated by Cox-hazard regression and Kaplan-Meier survival-curves, with sex-comparisons of distribution of risk-factors and therapy in total and age-matched (n = 166) groups. At diagnosis females were older, median 62 y vs. 51 y, (P < 0.001), but not different in outflow-gradients and median NYHA-class. However, septal hypertrophy was more advanced: 10.6 [IQR = 3.2] vs. 9.6 [2.5] mm/m2 BSA; P = 0.002. Females had higher disease-related mortality than males (P = <0.001), with annual mortality 2.9% vs. 1.5% in age-matched groups (P = 0.010 log-rank). For each risk-category identified (NYHA-class ≥ III, outflow-gradient ≥50 mmHg), a higher proportion of females died (P = 0.0004; P = 0.001). Calcium-blocker therapy was a risk-factor (P = 0.005) and was used more frequently in females (P = 0.034). A beta-blocker dose above cohort-median reduced risk for disease-related death in both males (HR = 0.32; P = 0.0040) and in females (HR = 0.49; P = 0.020). Excess female deaths occurred in chronic heart-failure (P = 0.001) and acute myocardial infarctions (P = 0.015). Fewer females received beta-blocker therapy after diagnosis (64% vs. 78%, P = 0.018), in a smaller dose (P = 0.007), and less frequently combined with disopyramide (7% vs. 16%, P = 0.048).

CONCLUSION

Addressing sex-disparities in the timing of diagnosis and pharmacological therapy has the potential to improve the care of females with oHCM.

Use of Embryonic Heart Grafted In Oculo to Assess Neurohumoral Controls of Cardiac Development*

Culture of embryonic heart in the anterior eye chamber allows neurohumoral and genetic controls of cardiac development to be separated from the influence of hemodynamic load. Hearts from 12-day gestation rat embryos grafted into the anterior eye chamber of an adult host rat attach to the iris and become vascularized and innervated by collaterals from the host iris. The spontaneous beating of grafts is pacemaker-driven and under functional neural control. Grafts do not beat against a pressure load, allowing the influence of neurohumoral factors to be separated from altered hemodynamic load. In oculo, embryonic heart differentiates into mature myocardium by most morphologic and biochemical criteria. Mature intercalated disks and myofibrils with well-defined Z-lines and M-lines are observed. Mature grafts express the high levels of α-myosin heavy chain characteristic of young adult myocardium. Surgical sympathetic denervation of the anterior eye chamber prior to grafting of embryonic hearts compromises growth and increases the intrinsic pacemaker rate. Since the grafts are perfused by the host circulation, the hormonal milieu of the graft can be altered by treatment of the host. Thus, the interaction between hormones and innervation of grafts can be studied using the in oculo model system.

Canstatin suppresses isoproterenol-induced cardiac hypertrophy through inhibition of calcineurin/nuclear factor of activated T-cells pathway in rats

Pathological cardiac hypertrophy associated with cardiac dysfunction is an independent risk factor for arrhythmia, myocardial infarction and sudden death. Canstatin, a C-terminal fragment of type IV collagen α2 chain, is abundantly expressed in normal heart tissue. We previously demonstrated that canstatin inhibits isoproterenol (ISO)-induced dephosphorylation of nuclear factor of activated T-cells (NFAT)c4, which plays an important role in cardiac hypertrophy, in differentiated H9c2 cardiomyoblasts. Thus, we investigated whether in vivo canstatin administration prevents ISO-induced cardiac hypertrophy through the inhibition of NFATc4 pathway. Rats were subcutaneously injected with ISO (5 mg/kg) or saline (Cont) for 7 days. Simultaneously, recombinant mouse canstatin (20 μg/kg) or vehicle was intraperitoneally administered. After left ventricular wall thickness and cardiac function were measured by echocardiography, the hearts were isolated and left ventricular weight (LVW) was weighed. Azan staining was performed to measure cross-sectional diameter of cardiomyocytes. Activity of calcineurin, which dephosphorylates NFATc4, was measured by calcineurin phosphatase activity assay. Immunohistochemical staining was performed to evaluate nuclear translocation of NFATc4. Intracellular Ca²⁺ concentration in neonatal rat cardiomyocytes (NRCMs) was measured by using a calcium indicator. Canstatin significantly inhibited ISO-induced increase of LVW, left ventricular posterior wall thickness at end-diastole and diameter of cardiomyocytes. Canstatin significantly inhibited ISO-induced activation of calcineurin, nuclear translocation of NFATc4, increased mRNA expression of β-myosin heavy chain and α-skeletal actin, and intracellular Ca²⁺ rise in NRCMs. In summary, we for the first time demonstrated that canstatin administration suppresses ISO-induced cardiac hypertrophy possibly through the blockade of calcineurin/NFATc4 pathway in rats.

Right Atrial Deformation Mechanics in Children with Adenotonsillar Hypertrophy

BACKGROUND

Children with significant adenotonsillar hypertrophy (ATH) may show right ventricular (RV) dysfunction. We aimed to evaluate RV dysfunction in such children before adenotonsillectomy by evaluating peak longitudinal right atrial (RA) strain (PLRAS) in systole. PLRAS, electrocardiogram (ECG) and conventional echocardiographic parameters were compared to distinguish children with significant ATH with sleep-related breathing disorder (ATH-SRBD) from controls.

METHODS

Fifty-six children (23 controls and 33 children with ATH-SRBD without symptoms of heart failure) were retrospectively studied. Preoperative echocardiograms and ECGs of children with ATH-SRBD who underwent adenotonsillectomy were compared to those of controls. Available postoperative ECGs and echocardiograms were also analyzed.

RESULTS

Preoperatively, prolonged maximum P-wave duration (Pmax) and P-wave dispersion (PWD), decreased PLRAS, and increased tricuspid annulus E/E′ were found in children with ATH-SRBD compared to those of controls. From the receiver operating characteristic curves, PLRAS was not inferior compared to tricuspid annulus E/E′, Pmax, and PWD in differentiating children with ATH-SRBD from controls; however, the discriminative abilities of all four parameters were poor. In children who underwent adenotonsillectomy, echocardiograms 1.2 ± 0.4 years after adenotonsillectomy showed no difference in postoperative PLRAS and tricuspid annulus E/E′ when compared with those of the preoperative period.

CONCLUSIONS

Impaired RA deformation was reflected as decreased PLRAS in children with ATH-SRBD before adenotonsillectomy. Decreased PLRAS in these children may indicate subtle RV dysfunction and increased proarrhythmic risk. However, usefulness of PLRAS as an individual parameter in differentiating preoperative children with ATH-SRBD from controls was limited, similar to those of tricuspid annulus E/E′, Pmax, and PWD.

Prevalence and predictors of asymmetric hypertensive heart disease: insights from cardiac and aortic function with cardiovascular magnetic resonance

AIMS

We sought to determine the prevalence of asymmetric hypertensive heart disease (HHD) overlapping morphologically with hypertrophic cardiomyopathy (HCM) and to determine predictors of this pattern of hypertensive remodelling.

METHODS AND RESULTS

One hundred and fifty hypertensive patients underwent 1.5 T cardiovascular magnetic resonance imaging. Twenty-one patients were excluded due to concomitant cardiac pathology that may confound the hypertrophic response, e.g. myocardial infarction, moderate-severe valvular disease, or other cardiomyopathy. Asymmetric HHD was defined as a segmental wall thickness of ≥15 mm and >1.5-fold the opposing wall in ≥1 myocardial segments, measured from short-axis cine stack at end-diastole. Ambulatory blood pressure, myocardial replacement fibrosis, aortic distensibility and aortoseptal angle were investigated as predictors of asymmetric HHD by multivariate logistic regression. Out of 129 hypertensive subjects (age: 51 ± 15 years, 50% male, systolic blood pressure: 170 ± 30 mmHg, diastolic blood pressure: 97 ± 16 mmHg), asymmetric HHD occurred in 21%. Where present, maximal end-diastolic wall thickness (EDWT) was 17.8 ± 1.9 mm and located exclusively in the basal or mid septum. In asymmetric HHD, aortoseptal angle (114 ± 10° vs. 125 ± 9° vs. 123 ± 12°, P < 0.05, respectively) was significantly reduced compared to concentric left ventricular hypertrophy (LVH) and compared to no LVH, respectively. Aortic distensibility in asymmetric HHD (1.01 ± 0.60 vs. 1.83 ± 1.65 mm²/mmHg × 10³, P < 0.05, respectively) was significantly reduced compared to subjects with no LVH. Age (odds ratio [95th confidence interval]: 1.10 [1.02-1.18], P < 0.05) and indexed LV mass (1.09 [0.98-1.28], P < 0.0001) were significant, independent predictors of asymmetric HDD.

CONCLUSIONS

Asymmetric HHD morphologically overlapping with HCM, according to the current ESC guidelines, is common. Postulating a diagnosis of HCM on the basis of EDWT of ≥15 mm should be made with caution in the presence of arterial hypertension particular in male subjects with elevated LV mass.

Sustained exposure to catecholamines affects cAMP/PKA compartmentalised signalling in adult rat ventricular myocytes

In the heart compartmentalisation of cAMP/protein kinase A (PKA) signalling is necessary to achieve a specific functional outcome in response to different hormonal stimuli. Chronic exposure to catecholamines is known to be detrimental to the heart and disrupted compartmentalisation of cAMP signalling has been associated to heart disease. However, in most cases it remains unclear whether altered local cAMP signalling is an adaptive response, a consequence of the disease or whether it contributes to the pathogenetic process. We have previously demonstrated that isoforms of PKA expressed in cardiac myocytes, PKA-I and PKA-II, localise to different subcellular compartments and are selectively activated by spatially confined pools of cAMP, resulting in phosphorylation of distinct downstream targets. Here we investigate cAMP signalling in an in vitro model of hypertrophy in primary adult rat ventricular myocytes. By using a real time imaging approach and targeted reporters we find that that sustained exposure to catecholamines can directly affect cAMP/PKA compartmentalisation. This appears to involve a complex mechanism including both changes in the subcellular localisation of individual phosphodiesterase (PDE) isoforms as well as the relocalisation of PKA isoforms. As a result, the preferential coupling of PKA subsets with different PDEs is altered resulting in a significant difference in the level of cAMP the kinase is exposed to, with potential impact on phosphorylation of downstream targets.

A study of the physiological consequences of sympathetic denervation of the heart caused by the arterial switch procedure

BACKGROUND

The arterial switch operation is the corrective operation for transposition of the great arteries, defined as the combination of concordant atrioventricular and discordant ventriculo-arterial connections, but there have been concerns about silent subendocardial ischaemia on exercise and coronary artery growth. The arterial switch divides the majority of the sympathetic nerves entering the heart; we have studied the effects of coronary flow and sensitivity to catecholamine stimulation in an animal model.

METHODS

A total of 10 piglets were operated on cardiopulmonary bypass with section and resuturing of aortic trunk, pulmonary artery and both coronary arteries, with 13 sham-operated controls. After 5-7 weeks of recovery, seven simulated switch survivors and 13 controls were studied.

RESULTS

Basal heart rate was significantly higher in switch piglets: in vivo mean (standard deviation) 112 (12) versus sham 100 (10) beats per minute, (p = 0.042); in vitro (Langendorff preparation): 89 (9) versus sham 73 (8) beats per minute (p = 0.0056). In vivo maximal heart rate in response to epinephrine was increased in switch piglets, 209 (13) versus 190 (17) beats per minute (p = 0.044). In vitro dose-response curves to norepinephrine were shifted leftward and upwards (p = 0.0014), with an 80% increase in heart rate induced by 0.095 (0.053) norepinephrine micromole per litre perfusate in switch hearts versus 0.180 (0.035) norepinephrine micromole per litre (p = 0.023). Increase in coronary flow on norepinephrine stimulation and maximal coronary flow were significantly reduced in switch hearts: 0.3 (0.2) versus 0.8 (0.4) millilitre per gram heart weight (p = 0.045) and 2.5 (0.4) versus 3.1 (0.4) millilitre per gram heart (p = 0.030), respectively.

CONCLUSIONS

A combination of increased intrinsic heart rate, increased sensitivity to chronotropic actions of norepinephrine, and a decreased maximal coronary flow creates potential for a mismatch between perfusion and energy demands.

Signaling responses after exposure to 5 alpha-dihydrotestosterone or 17 beta-estradiol in norepinephrine-induced hypertrophy of neonatal rat ventricular myocytes

Androgens appear to enhance, whereas estrogens mitigate, cardiac hypertrophy. However, signaling pathways in cells for short (3 min) and longer term (48 h) treatment with 17beta-estradiol (E2) or 5 alpha-dihydrotestosterone (DHT) are understudied. We compared the effect of adrenergic stimulation by norepinephrine (NE; 1 microM) alone or in combination with DHT (10 nM) or E2 (10 nM) treatment in neonatal rat ventricular myocytes (NRVMs) by cell area, protein synthesis, sarcomeric structure, gene expression, phosphorylation of extracellular signal-regulated (ERK), and focal adhesion kinases (FAK), and phospho-FAK nuclear localization. NE alone elicited the expected hypertrophy and strong sarcomeric organization, and DHT alone gave a similar but more modest response, whereas E2 did not alter cell size. Effects of NE dominated when used with either E2 or DHT with all combinations. Both sex hormones alone rapidly activated FAK but not ERK. Long-term or brief exposure to E2 attenuated NE-induced FAK phosphorylation, whereas DHT had no effect. Neither hormone altered NE-elicited ERK activation. Longer term exposure to E2 alone reduced FAK phosphorylation and reduced nuclear phospho-FAK, whereas its elevation was seen in the presence of NE with both sex hormones. The mitigating effects of E2 on the NE-elicited increase in cell size and the hypertrophic effect of DHT in NRVMs are in accordance with results observed in whole animal models. This is the first report of rapid, nongenomic sex hormone signaling via FAK activation and altered FAK trafficking to the nucleus in heart cells.

The relation between cardiac hypertrophy and hypertension

Left ventricular mass determined echocardiographically was related to blood pressure in a stratified random sample (n = 120) of 49-year-old men selected from a blood pressure screening and covering a wide range of blood pressures. Only subjects not on antihypertensive treatment were studied. Left ventricular mass was also related to sympathetic activity, the renin-angiotensin-aldosterone system and glucose metabolism. A poor correlation between left ventricular mass and blood pressure was found in the entire study group. In the upper blood pressure range only blood pressure during isometric exercise was significantly correlated with left ventricular mass. In this range there were significant correlations between left ventricular mass and 24 hour urinary noradrenaline excretion and plasma aldosterone. In the intermediate blood pressure range there was an association between left ventricular mass and blood glucose and plasma insulin. It is concluded that in mild to moderate hypertension other factors probably modify the hypertrophic response to rising arterial pressure.

Increased cardiac output and lowered peripheral resistance during metoprolol treatment

Echocardiography was performed at every six months in hypertensives well controlled on metoprolol, 100 mg twice a day. After six months' treatment blood pressure was reduced from 177/110 mm Hg to 147/88 (p less than 0.02). LV wall thickness (septum + posterior wall) was unchanged 2.10 cm (2.14), and a significant drop in cardiac output (CO) to 5.0 l/min (6.1, p less than 0.02) was recorded (pretreatment values in brackets). After 24 months' treatment LV wall thickness was reduced to 1.94 cm (p less than 0.02), total peripheral resistance (TPR) to 17.3 mm Hg/l/min (23.4, p less than 0.02) and CO increased to 6.7 l/min (6.1, n.s.). After six months' treatment, there was thus a drop in BP with a significant drop in CO and unchanged TPR. After 24 months' treatment, however, CO was back to the pretreatment level and the drop in BP was entirely caused by a drop in TPR which was probably secondary to a reduction in the wall thickness of the arterial resistance vessels as judged by the relationship between the reduction in wall thickness in the LV and the reduction in TPR during the treatment.

Selective cardiac neuroadrenergic abnormalities in hypertensive patients with left ventricular hypertrophy

BACKGROUND

Increased sympathetic drive to the heart might contribute to the development and progression of myocardial damage in hypertensive patients (HTs). This study assessed the possible presence of abnormalities in myocardial uptake of (123)I-metaiodobenzylguanidine (MIBG), a marker of sympathetic activity, in HTs with left ventricular hypertrophy (LVH).

METHODS

Eleven HTs with LVH and 10 matched normotensive controls underwent clinical and laboratory examination, as well as LVH determination by echocardiography. The presence of myocardial ischemia was ruled out by exercise stress testing. Global and regional myocardial uptake of (123)I-MIBG was determined in both groups using planar and single proton emission tomography scintigraphy. In addition, thallium-201 (Tl-201) myocardial scintigraphy was performed in HTs. The heart/mediastinum (H/M) ratio on planar (123)I-MIBG images at different time points was compared between HTs and controls. Moreover, regional cardiac uptake of (123)I-MIBG was compared between groups and, within the HTs group, with regional Tl-201 uptake.

RESULTS

At all study times, the H/M ratio was lower in HTs than in controls (all p <0.05). A significant reduction in (123)I-MIBG uptake in the mid-inferolateral and mid-inferior segments was observed in HTs compared to controls. Also, a significant reduction in (123)I-MIBG uptake compared to Tl-210 uptake was observed in non-septal segments of HTs.

CONCLUSIONS

Cardiac abnormalities in global and regional uptake of (123)I-MIBG, as well as impaired (123)I-MIBG compared to Tl-201 uptake, are present in HTs with LVH. Given the effect of sympathetic nervous system on the heart, these abnormalities might play a role in hypertension-related cardiac damage.

Aortic Elastic Properties in Patients With Hypertensive Response to Exercise

BACKGROUND

The aim of this study was to evaluate whether there is a relationship between aortic elastic properties in patients with a suggestive response to treadmill exercise testing.

METHODS AND RESULTS

The study group comprised 32 patients suggesting hypertensive response to exercise and 20 patients suggesting normal blood pressure response to treadmill exercise testing. Baseline demographic characteristics were similar in both groups. However, the mean aortic stiffness index of patients suggesting hypertensive response to treadmill exercise testing was significantly higher (4.8+/-1.26 vs 2.36+/-1.09; p=0.001) whereas aortic distensibility was significantly lower (12.82 +/-5.84 vs 22.64+/-14.54; p=0.001) than the control group. The aortic strain of patients with hypertensive response to exercise was lower than the control group (12+/-3% vs 19.2+/-5%, p<0.001). The left ventricular mass (LVM) of these patients was also higher than control group (206.5+/-46.3 vs 134.2+/-19.97; p=0.01). A negative correlation between LVM and distensibility was found (r=-0.64; p=0.001) well as a positive correlation between LVM and aortic stiffness index (r=0.51; p=0.004) in patients suggesting hypertensive response to exercise. Pressure--rate product was also found to be correlated with LVM (r=0.47; p=0.006).

CONCLUSION

Elastic properties of the aorta may be impaired in subjects showing exaggerated blood pressure response to exercise long before clinically manifest hypertension, particularly if the LVM is increased.

Alpha1-adrenergic receptors prevent a maladaptive cardiac response to pressure overload

An alpha1-adrenergic receptor (alpha1-AR) antagonist increased heart failure in the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT), but it is unknown whether this adverse result was due to alpha1-AR inhibition or a nonspecific drug effect. We studied cardiac pressure overload in mice with double KO of the 2 main alpha1-AR subtypes in the heart, alpha 1A (Adra1a) and alpha 1B (Adra1b). At 2 weeks after transverse aortic constriction (TAC), KO mouse survival was only 60% of WT, and surviving KO mice had lower ejection fractions and larger end-diastolic volumes than WT mice. Mechanistically, final heart weight and myocyte cross-sectional area were the same after TAC in KO and WT mice. However, KO hearts after TAC had increased interstitial fibrosis, increased apoptosis, and failed induction of the fetal hypertrophic genes. Before TAC, isolated KO myocytes were more susceptible to apoptosis after oxidative and beta-AR stimulation, and beta-ARs were desensitized. Thus, alpha1-AR deletion worsens dilated cardiomyopathy after pressure overload, by multiple mechanisms, indicating that alpha1-signaling is required for cardiac adaptation. These results suggest that the adverse cardiac effects of alpha1-antagonists in clinical trials are due to loss of alpha1-signaling in myocytes, emphasizing concern about clinical use of alpha1-antagonists, and point to a revised perspective on sympathetic activation in heart failure.

The influence of aldosterone on the development of left ventricular geometry and hypertrophy in patients with essential hypertension

The identification of risk factors for the initiation of left ventricle hypertrophy (LVH), which is an independent risk factor for cardiovascular mortality and morbidity in hypertensive patients, is very important. The objective of the present study was to identify the relationship of aldosterone with LVH and different geometrical patterns of left ventricle that develop in patients with essential hypertension. A total of 83 patients with essential hypertension (44 females, mean age, 51 +/- 8 years, 39 males, mean age, 57 +/- 10 years) were included in this study. Thirty-two had LVH. When evaluated according to the geometrical patterns of LVH, 18 patients had concentric LVH, 14 had eccentric LVH, and 17 had concentric remodeling. Thirty-four patients had normal left ventricle geometry. Two weeks after the cessation of antihypertensive medications, sodium, potassium, and proteinuria in 24-hour urine samples and plasma aldosterone levels and plasma renin activity were measured. Plasma aldosterone levels of the patients with LVH were found to be significantly higher (9.92 +/- 6.34 ng/dL versus 5.83 +/- 3.5 ng/dL, P < 0.01). The difference between plasma renin activities was not statistically significant. Linear regression analysis revealed that plasma aldosterone level and age were independent parameters increasing left ventricle mass index. The plasma aldosterone levels of patients with concentric hypertrophy of the left ventricle were significantly higher than those of patients with normal geometry and concentric remodeling. There was no significant difference between plasma renin activities. Twenty-four hour urine protein concentrations of the patients with LVH were found to be significantly higher and sodium to be significantly lower. Plasma aldosterone levels seem to be correlated with LVH especially with concentric hypertrophy of the left ventricle in patients with essential hypertension.

Cardiovascular reactivity and left ventricular mass: An integrative review

Left ventricular hypertrophy has been shown to be an independent predictor of risk for cardiovascular morbidity and mortality. Behavioral scientists have focused on how hemodynamic factors influenced by psychosocial stress may be associated with left ventricular mass (LVM). We reviewed existing studies examining stress-related cardiovascular reactivity (CVR) and LVM, with a goal of examining the moderating role of population (age and hypertensive status) and methodological factors (task type, sample size, and study design) explaining the observed results. Twenty-one studies met the criteria for this review. Results showed only a modestly consistent relationship between CVR and LVM. Forty-three percent of the studies reported 1 or more significant results linking systolic blood pressure reactivity with LVM, and 14% of the studies showed that diastolic blood pressure reactivity was significantly related to LVM. Hypertensive status, task type, and sample size did not play a major role in moderating the relationship between LVM and CVR. A somewhat larger percentage of positive results was shown in prospective and adult studies. The association between CVR and LVM may be real, although the effect size is modest, and we discuss methodological strategies for enhancing statistical power in future investigations. Additional sampling factors (e.g., race, gender) may also impact this relationship. Finally, greater attention is warranted to the role of the psychosocial environment, as this may interact with reactivity to influence LVM.

Adaptations to iron deficiency: cardiac functional responsiveness to norepinephrine, arterial remodeling, and the effect of beta-blockade on cardiac hypertrophy

BACKGROUND

Iron deficiency (ID) results in ventricular hypertrophy, believed to involve sympathetic stimulation. We hypothesized that with ID 1) intravenous norepinephrine would alter heart rate (HR) and contractility, 2) abdominal aorta would be larger and more distensible, and 3) the beta-blocker propanolol would reduce hypertrophy.

METHODS

1) 30 CD rats were fed an ID or replete diet for 1 week or 1 month. Norepinephrine was infused via jugular vein; pressure was monitored at carotid artery. Saline infusions were used as a control. The pressure trace was analyzed for HR, contractility, systolic and diastolic pressures. 2) Abdominal aorta catheters inflated the aorta, while digital microscopic images were recorded at stepwise pressures to measure arterial diameter and distensibility. 3) An additional 10 rats (5 ID, 5 control) were given a daily injection of propanolol or saline. After 1 month, the hearts were excised and weighed.

RESULTS

Enhanced contractility, but not HR, was associated with ID hypertrophic hearts. Systolic and diastolic blood pressures were consistent with an increase in arterial diameter associated with ID. Aortic diameter at 100 mmHg and distensibility were increased with ID. Propanolol was associated with an increase in heart to body mass ratio.

CONCLUSIONS

ID cardiac hypertrophy results in an increased inotropic, but not chronotropic response to the sympathetic neurotransmitter, norepinephrine. Increased aortic diameter is consistent with a flow-dependent vascular remodeling; increased distensibility may reflect decreased vascular collagen content. The failure of propanolol to prevent hypertrophy suggests that ID hypertrophy is not mediated via beta-adrenergic neurotransmission.

Blood pressure determinants of left ventricular wall thickness and mass index in hypertension: comparing office, ambulatory and exercise blood pressures

Left ventricular (LV) mass relates positively and continuously to cardiac mortality and thus its regression is a rational therapeutic aim. Whilst the office blood pressure (BP) relates poorly to LV mass, it was unclear whether the 24-h ambulatory BP or the exercise systolic BP (ExSBP) was the stronger correlate of LV structural indices. We studied 49 hypertensive patients with a mean age of 45 (s.d. 12) years with a mean body mass index of 27.1(3.9) kg/m(2). The mean (s.d.) of office BP, ambulatory BP and ExSBP measured at the end of the first three stages of Bruce protocol treadmill exercise I, II and III were 161(20)/99(10), 140(13)/89(10), 190(30), 198(30) and 201(33) mm Hg respectively. The LV indices measured echocardiographically were LV septal thickness (IVSd) (1.1(0.2) cm), LV posterior wall thickness (LVPWd) (1.0(0.1) cm) and LV mass indexed to body surface area (LVMI) (123(30) g/m(2)). Age and gender (male) had the highest correlations with the LV indices. Of the BP measures, the stage II ExSBP's correlation with the LV indices was consistently higher than all other ExSBP, office systolic BP and 24-h systolic ambulatory BP. In a stepwise multiple regression analysis on IVSd, after adjusting for age and gender, the stage II ExSBP was independently associated with IVSd (beta= 0.018 (s.e. 0.008), P = 0.024). When only BP measures were considered as explanatory variables only stage II ExSBP was a significant predictor (P = 0.0001) of IVSd as was the case with LVPWd (P = 0.006) and LVMI (P = 0.0008). Submaximal exercise BP measured at a workload comparable to physical activity encountered in daily life correlated more closely with the left ventricular wall thickness and mass. The exercise BP should perhaps be normalised in hypertension management to optimise regression of LV hypertrophy.

Catecholamines stimulate interleukin-6 synthesis in rat cardiac fibroblasts

Proinflammatory cytokines have been implicated in the pathophysiology of different heart diseases. Recent evidence suggests that interleukin-6 (IL--6) may play a role in mechanisms leading to cardiac hypertrophy. In addition, catecholamines are known to induce cardiac hypertrophy. In the present study, we examined whether cardiac fibroblasts may be a potential source of IL--6 production in the rat heart and whether catecholamines can modulate the IL--6 synthesis. Only a small amount of IL--6 mRNA was detected in unstimulated rat cardiac fibroblasts. However, a 50-fold increase of IL--6 mRNA was found after stimulation with norepinephrine (NE). Addition of carvedilol, a alpha- and beta-adrenergic receptor antagonist, prevented almost completely the NE-induced synthesis of IL--6 mRNA. Phenylephrine, an alpha-adrenergic agonist, and isoproterenol, a beta-adrenergic agonist, also induced an increase in IL--6. However, the stimulation via beta-receptors led to a more pronounced elevation. These data show that NE increases IL--6 expression in rat cardiac fibroblasts and that IL--6 may play an important autocrine/paracrine role in cardiac disease states associated with hypertrophy.

Renin-angiotensin system and sympathetic nervous system in cardiac pressure-overload hypertrophy

Angiotensin II and norepinephrine (NE) have been implicated in the neurohumoral response to pressure overload and the development of left ventricular hypertrophy. The purpose of this study was to determine the temporal sequence for activation of the renin-angiotensin and sympathetic nervous systems in the rat after 3-60 days of pressure overload induced by aortic constriction. Initially on pressure overload, there was transient activation of the systemic renin-angiotensin system coinciding with the appearance of left ventricular hypertrophy (day 3). At day 10, there was a marked increase in AT(1) receptor density in the left ventricle, increased plasma NE concentration, and elevated cardiac epinephrine content. Moreover, the inotropic response to isoproterenol was reduced in the isolated, perfused heart at 10 days of pressure overload. The affinity of the beta(2)-adrenergic receptor in the left ventricle was decreased at 60 days. Despite these alterations, there was no decline in resting left ventricular function, beta-adrenergic receptor density, or the relative distribution of beta(1)- and beta(2)-receptor sites in the left ventricle over 60 days of pressure overload. Thus activation of the renin-angiotensin system is an early response to pressure overload and may contribute to the initial development of cardiac hypertrophy and sympathetic activation in the compensated heart.

Anticipatory blood pressure responses to exercise are associated with left ventricular mass in Finnish men: Kuopio Ischemic Heart Disease Risk Factor Study

BACKGROUND

Exaggerated cardiovascular reactivity to psychological demands may contribute to the development of left ventricular (LV) hypertrophy. We examined the cross-sectional association between anticipatory blood pressure (BP) responses to bicycle exercise and LV mass in the Kuopio Ischemic Heart Disease Risk Factor Study, a population-based epidemiological sample.

METHODS AND RESULTS

Among 876 men from 4 age cohorts (ages 42, 48, 58, and 64 years), we collected echocardiographic assessments of LV mass along with measures of BP response taken before bicycle ergometry testing. Anticipatory BP responses were positively associated with LV mass, with significant associations only among younger (age <50 years) subjects with elevated resting pressures (3-way interactions for anticipatory BP x age x resting pressure for systolic and diastolic BP, all P:<0.05; for younger subjects with elevated systolic BP, P:<0. 01; and for younger subjects with elevated diastolic BP, P:<0.001). Among these subgroups, exaggerated anticipatory BP responses (top quartile) were associated with an incremental increase in LV mass of 10% or greater, corrected for body surface area. Results remained significant after adjusting for age, education, salt consumption, and resting BP, and the pattern of findings was maintained among men with no previous history of cardiovascular disease.

CONCLUSIONS

The tendency to show exaggerated pressor responses to psychological demands may be a significant independent correlate of LV mass, especially among young men with high resting pressures. This is the first study to examine such associations in a middle-aged population sample.

Effects of beta-adrenoceptor stimulation on pacing-induced failure of dog hypertrophic hearts

1. We tested the hypothesis that the transition to pacing-induced failure in hypertrophic hearts would result in reduced functional and metabolic responses to beta-adrenoceptor stimulation. 2. Isoproterenol (ISO; 0.1 microg/kg per min) was infused into a coronary artery in five anaesthetized open-chest control, five aortic stenosis-induced left ventricular hypertrophy (LVH) and five LVH pacing-induced failure dogs. 3. In both control and LVH dogs, but not in failure dogs, ISO significantly increased local regional work (1,923+/-665 vs 2,656+/-715, 1,185+/-286 vs 1,906+/-562 and 835+/-106 vs 849+/-216g.mm/min, respectively), force (11.1+/-1.4 vs 16.9+/-2.6, 8.6+/-1.5 vs 13.7+/-2.3 and 12.2+/-1.1 vs 11.0+/-1.8g, respectively) and myocardial O2 consumption (7.3+/-2.0 vs 10.0+/-1.5, 8.2+/-1.6 vs 11.6+/-2.6 and 4.4+/-1.5 vs 5.5+/-1.8 mL O2/min per 100 g, respectively). 4. Isoproterenol also significantly increased cAMP in control and LVH dogs (474+/-67 vs 600+/-91 and 473+/-34 vs 619+/-53 pmol/g, respectively). In heart failure, cAMP was significantly lower and there was no significant increase in cAMP in response to ISO (245+/-43 vs 314+/-40pmol/g, respectively). 5. We conclude that there were no significant myocardial functional, O2 consumption or cAMP responses to ISO after the transition from hypertrophy to cardiac failure.

A cohort study of childhood hypertrophic cardiomyopathy: improved survival following high-dose beta-adrenoceptor antagonist treatment

OBJECTIVES

The study analyzed factors, including treatment, affecting disease-related death in patients with hypertrophic cardiomyopathy (HCM) presenting in childhood.

BACKGROUND

Previous smaller studies suggest that mortality is higher in patients with HCM presenting in childhood compared with presentation in adulthood, but these studies have all originated from selected patient populations in tertiary referral centers, and reported no significant protection by treatment.

METHODS

Retrospective comparisons of mortality were done in total cohort of patients presenting to three regional centers of pediatric cardiology. There were 66 patients (25 with Noonan's syndrome) with HCM presenting at age <19 years; mean follow-up was 12.0 years.

RESULTS

Among risk factors for death were congestive heart failure (p = 0.008), large electrocardiogram voltages (Sokolow-Lyon index p = 0.0003), and degree of septal (p = 0.004) and left ventricular (p = 0.028) hypertrophy expressed as percent of 95th centile value. The only treatment that significantly reduced the risk of death on multifactorial analysis of variance was high-dose beta-adrenoceptor antagonist therapy (propranolol 5 to 23 mg/kg/day or equivalent; p = 0.0001). Nineteen out of 40 patients managed conventionally (no treatment, 0.8 to 4 mg/kg of propranolol, or verapamil) died, median survival 15.8 years, with no deaths among 26 patients on high-dose beta-blockers (p = 0.0004); survival proportions at 10 years were 0.65 (95% confidence interval 0.49-0.80) and 1.0, respectively (p = 0.0015). Survival time analysis shows better survival in the high-dose beta-blocker group compared with the "no specific therapy" group (p = 0.0009) and with the conventional-dose beta-blocker group (p = 0.002). Hazard ratio analysis suggests that high-dose beta-blocker therapy produces a 5-10-fold reduction in the risk of disease-related death.

CONCLUSIONS

High-dose beta-blocker therapy improves survival in childhood HCM.

Pacing-induced cardiac failure of hypertrophic hearts: effects of cyclic GMP reduction

BACKGROUND

We tested the hypothesis that pacing-induced cardiac failure of hypertrophic hearts would reduce the functional and metabolic responses of these hearts to guanylate cyclase inhibition and this was associated with alterations in cyclic GMP.

MATERIALS AND METHODS

Methylene blue (MB, 2 mg/kg/min, guanylate cyclase inhibitor) was infused into the left anterior descending coronary artery in 5 control, 5 left ventricular hypertrophy (LVH), and 5 LVH pacing-induced failure dogs. Regional myocardial work was calculated as the integrated product of force and segment shortening and regional myocardial O(2) consumption (VO(2)) from coronary blood flow and O(2) extraction measurements. Cyclic GMP was determined by radioimmunoassay.

RESULTS

MB increased regional work (635 +/- 169 vs 1649 +/- 500, 781 +/- 184 vs 1569 +/- 203 g * mm/min) and VO(2) (8.3 +/- 1.4 vs 10.9 +/- 1.4, 7.3 +/- 0.7 vs 9.1 +/- 0.7 ml O(2)/min/100 g) in both control and LVH dogs but not in failure dogs (536 +/- 234 vs 623 +/- 193, 3.6 +/- 1.1 vs 4.7 +/- 1.9). MB also decreased cyclic GMP in control dogs (1170 +/- 142 vs 812 +/- 105 pmol/g). LVH dogs had elevated baseline cyclic GMP (5875 +/- 949) compared to control dogs but also demonstrated decreased cyclic GMP in response to MB (2820 +/- 372). In failure dogs, basal cyclic GMP was also elevated (4650 +/- 613) compared to control dogs but there was a lack of response to MB (3670 +/- 640).

CONCLUSIONS

We conclude that the myocardial function, VO(2) and cyclic GMP responses to methylene blue are diminished in the transition from hypertrophy to cardiac failure.

Expression of immediate early genes, GATA-4, and Nkx-2.5 in adrenergic-induced cardiac hypertrophy and during regression in adult mice

Adrenoreceptor agonists induce a hypertrophic phenotype in vitro and in vivo. To investigate the molecular remodeling in chronic cardiac hypertrophy we infused adult male mice with vehicle. isoproterenol, phenylephrine or both agonists for 3, 7 or 14 days. All drugs increased cardiac mass. After minipump removal cardiac mass regressed to control levels within 7 days after PE and ISO treatment whereas ISO + PE treated hearts were incompletely regressed. ANF and beta-MHC, but not alpha-MHC, expression were increased by agonists at all time points. GATA-4, Nkx-2.5, Egr-1, c-jun and c-fos expression were increased after 3, 7 and 14 days of treatment. Expression was greatest after ISO+PE> >ISO>PE>vehicle infusion suggesting a synergistic effect of adrenoreceptor stimulation and indicating a greater effect of beta- than alpha-adrenergic action in vivo. After PE or ISO drug withdrawal the HW/BW was normal and Egr-1, c-jun, c-fos and GATA-4, but not Nkx2.5, expression dropped to control levels. HW/BW regression was incomplete after ISO+PE and elevated levels of Egr-1, c-jun and Nkx2.5 expression remained. A hydralazine-mediated reduction in blood pressure had no effect on the agonist-induced cardiac hypertrophy or gene expression. In conclusion, we found that continued agonist stimulation, and not blood pressure. is responsible for the maintained increase in gene expression. Further, we found the decrease in gene expression in the regression after drug withdrawal was gene specific.

Catecholamines in cardiac hypertrophy

There has been intense interest in the roles catecholamines may play in compensatory myocardial hypertrophy. This article reviews the following: (1) chronic infusions of catecholamines in experimental animals result in cardiac hypertrophy, but in many of the studies mechanical factors have played a role; (2) experiments using isolated papillary muscles and isolated hearts, stretched isolated myocytes, and denervated hearts in vivo demonstrate that mechanical activity is sufficient to cause increased protein synthesis and cell growth; (3) in neonatal myocyte cell cultures, alpha-adrenergic agonists are powerful stimulants for protein synthesis and cell growth. Beta-adrenergic stimulation of nonmyocyte myocardial cells causes release of a factor that promotes protein synthesis in neonatal myocytes. Either alpha or beta stimulation, probably through different mechanisms, appears to have growth-promoting effects on isolated adult myocytes in culture; (4) alpha stimulation is transduced through the Gq pathway and its activation of phospholipase C, cleavage of phosphatidylinositol (4,5)-bisphosphate, and then further through the ras/raf, mitogen-activated protein (MAP) kinase system; (5) transgenic mice with upregulation of catecholamine-related systems have not clarified the independent role of either the alpha- or beta-adrenergic pathway; and (6) observations in humans suggest that mechanical factors predominate in the development and regression of cardiac hypertrophy. Humoral mechanisms, including catecholamines, may play a role, but their quantitative importance has not been determined. It is hypothesized that catecholamines may play a role in transition from the adaptive to the maladaptive state.

Effects of chronic adenosine uptake blockade on adrenergic responsiveness and left ventricular chamber function in pressure overload hypertrophy in the rat

BACKGROUND

Increased sympathetic activity contributes to the progression of heart failure. Adenosine counteracts sympathetic activity by inhibition of presynaptic norepinephrine release and attenuation of the metabolic and contractile responses to beta-adrenergic stimulation. In this study, we tested the hypothesis that the adenosinergic effects (uptake blockade) of dipyridamole may retard the progression of pressure overload hypertrophy in the rat.

METHODS AND RESULTS

To verify that the administration of dipyridamole increases myocardial adenosine levels in the rat, epicardial adenosine concentrations were measured from 12 isolated, perfused rat hearts exposed to 10(-7) and 10(-6) mol/l dipyridamole. Adenosine concentrations were increased with both doses of dipyridamole. Also, 9 weeks of dipyridamole treatment resulted in decreased sensitivity to the adenosine A1-receptor agonist, 2-chloro-N6-cyclopentyl adenosine, suggesting that dipyridamole increases adenosine levels in the intact rat. In the second part of the study, rats were divided into either abdominal aortic-banded or sham-operated groups and were treated with either dipyridamole or saline. After 9 weeks of treatment, two-dimensional Doppler echocardiographic studies were performed and the adrenergic responsiveness to 10(-8) mol/l isoproterenol was assessed in vitro. The saline-treated banded group demonstrated concentric left ventricular hypertrophy, abnormal diastolic filling, increased wet lung weights and attenuation of adrenergic responsiveness. In contrast, the dipyridamole-treated banded rats exhibited more concentric geometry (higher relative wall thickness with similar left ventricular mass), normal left ventricular filling characteristics and preserved adrenergic responsiveness. Systolic left ventricular chamber and myocardial function, as assessed by stress-endocardial and midwall shortening relationships, were not significantly altered by banding or dipyridamole treatment.

CONCLUSIONS

Dipyridamole treatment prevented the development of abnormal left ventricular chamber filling, preserved adrenergic responsiveness and appeared to attenuate detrimental chamber remodeling in rats with pressure overload hypertrophy.

The sympathetic nervous system in chronic heart failure

The sympathetic nervous system plays a pivotal role in the natural history of chronic heart failure (CHF). There is early activation of cardiac adrenergic drive, which is followed by an increasing magnitude of generalized sympathetic activation, with worsening heart failure. The adverse consequences predominate over the short-term compensatory effects and are mediated through downregulation of beta-receptor function and harmful biological effects on the cardiomyocyte. beta-blockers exert a beneficial effect on the natural history of CHF by attenuating the negative biological effects, restoring homogeneity of contractile/relaxant mechanisms, and reducing the risk of myocardial ischemia and arrhythmias. After pioneering work conducted over 20 years ago, numerous studies have shown the beneficial effects of beta-blockade on left ventricular function, and survival, morbidity, and mortality rates in CHF. Large-scale trials are underway to determine the overall benefits of beta-blockade in heart failure.

Diverse effects of renal denervation on ventricular hypertrophy and blood pressure in DOCA-salt hypertensive rats

Cardiac hypertrophy that accompanies hypertension seems to be a phenomenon of multifactorial origin whose development does not seem to depend on an increased pressure load alone, but also on local growth factors and cardioadrenergic activity. The aim of the present study was to determine if sympathetic renal denervation and its effects on arterial pressure level can prevent cardiac hypertrophy and if it can also delay the onset and attenuate the severity of deoxycorticosterone acetate (DOCA)-salt hypertension. DOCA-salt treatment was initiated in rats seven days after uninephrectomy and contralateral renal denervation or sham renal denervation. DOCA (15 mg/kg, s.c.) or vehicle (soybean oil, 0.25 ml per animal) was administered twice a week for two weeks. Rats treated with DOCA or vehicle (control) were provided drinking water containing 1% NaCl and 0.03% KCl. At the end of the treatment period, mean arterial pressure (MAP) and heart rate measurements were made in conscious animals. Under ether anesthesia, the heart was removed and the right and left ventricles (including the septum) were separated and weighted. DOCA-salt treatment produced a significant increase in left ventricular weight/body weight (LVW/BW) ratio (2.44 +/- 0.09 mg/g) and right ventricular weight/body weight (RVW/BW) ratio (0.53 +/- 0.01 mg/g) compared to control (1.92 +/- 0.04 and 0.48 +/- 0.01 mg/g, respectively) rats. MAP was significantly higher (39%) in DOCA-salt rats. Renal denervation prevented (P > 0.05) the development of hypertension in DOCA-salt rats but did not prevent the increase in LVW/BW (2.27 +/- 0.03 mg/g) and RVW/BW (0.52 +/- 0.01 mg/g). We have shown that the increase in arterial pressure level is not responsible for cardiac hypertrophy, which may be more related to other events associated with DOCA-salt hypertension, such as an increase in cardiac sympathetic activity.

Pathological versus physiological left ventricular hypertrophy: a review

Left ventricular hypertrophy is recognized as an independent risk factor for cardiovascular morbid events. The primary mechanisms responsible for stimulating it are unknown. Epidemiological theories suggest that left ventricular hypertrophy is a continuous variable with no threshold, while morphological studies argue that it is the structure, or quality, and function of the myocardium (and therefore non-continuous), not the quantity of the myocardial mass, that poses the cardiovascular risk. Although left ventricular hypertrophy has been classically viewed as an adaptive response of the cardiovascular system to an imposed load, it has been demonstrated that haemodynamic overloading in selected hypertensive patients is not the sole determinant of left ventricular structure and function. Pathological and physiological states of left ventricular hypertrophy have been described primarily using criteria focusing on normal chamber performance and oxygen delivery as well as the reversibility of the hypertrophy once the overload is removed. Both states are also defined by the nature of the imposed load and the resulting myocardial adaptations. This review addresses the pathological and physiological states of left ventricular hypertrophy, the hypertrophy patterns, and the corresponding structural and functional characteristics, together with some of the biochemical factors thought to influence remodelling.

Effects of norepinephrine on expression of IGF-1/IGF-1R and SERCA2 in rat heart

OBJECTIVES

The effects of norepinephrine on expression of cardiac genes during pathological cardiac growth and heart failure are not fully understood. Tissue insulin-like growth factor 1 (IGF-1) and its receptor (IGF-1R) play an important role in the regulation of the hyperplastic capacity of cardiac myocytes. Sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2), on the other hand, is important in regulating cardiac contractile function. The present study examined the effects of elevated levels of NE on expression of IGF-1/IGF-1R and SERCA2 mRNAs.

METHODS

Rats were infused with NE using osmotic minipumps for 3 and 6 days at a rate of 50 micrograms/kg/h and also at a higher dose (130 micrograms/kg/h) for 6 and 14 days. Levels of expression of IGF-1/IGF-1R and SERCA2 mRNAs were determined by ribonuclease protection assay and by Northern blotting, respectively.

RESULTS

NE treatment significantly increased IGF-1 mRNA levels in both left- and right-ventricle; however, levels of IGF-1R increased in the left- but not the right-ventricle. By contrast, NE infusion at both the lower dose and the higher dose failed to alter expression of SERCA2 mRNA.

CONCLUSION

Our results suggest that NE treatment differentially regulates expression of IGF-1 and IGF-1R in the ventricles of rat heart and that NE appears not to affect expression of SERCA2 mRNA.

Myocardial ventricular mass related to coronary artery distribution in human hearts

This prospective study of 120 autopsy collected human hearts correlates the "Right Ventricle/Left Ventricle" free walls mass ratio and the ventricular mass fraction supplied by the right coronary ("Right Coronary/Ventricular Weight"). Different coloured gel injected through both coronary artery's capillary beds allowed ventricular myocardium separation to obtain the weights. In hearts without hypertrophy, mean +/- standard deviation of the "Right Ventricle/Left Ventricle" mass ratio was 0.54 +/- 0.09 for males and 0.62 +/- 0.23 for females; "Right Coronary/Ventricular Weight" mass ratios were 0.39 +/- 0.08 and 0.39 +/- 0.04, respectively. Mean +/- standard deviation of the "Right Ventricle/Left Ventricle" and "Right Coronary/Ventricular Weight" ratios were 0.37 +/- 0.05 and 0.36 +/- 0.10, respectively in hearts with "Left Ventricle Hypertrophy"; 0.56 +/- 0.07 and 0.38 +/- 0.11 in hearts "Without Hypertrophy"; 0.54 +/- 0.08 and 0.39 +/- 0.08 in hearts with "Biventricular Hypertrophy"; 0.89 +/- 0.16 and 0.49 +/- 0.06 in hearts with "Right Ventricle Hypertrophy". Means and variances are narrower for the "Right Coronary/Ventricular Weight" than that observed for the "Right Ventricle/Left Ventricle" mass ratio. It is due to the special double coronary arrangement in which every artery irrigates both ventricles. These results suggest that the usual pattern of the human coronary arteries' anatomy acts as a buffer for the ventricular mass distribution to be irrigated by both arteries in hypertrophy.

Treatment and post-treatment effects of alpha- versus beta-receptor blockers on left ventricular structure and function in essential hypertension

This study was undertaken to compare the effects of alpha-receptor blockade and beta-receptor blockade on left ventricular structure and function in essential hypertension. The increase in left ventricular mass in patients with essential hypertension is at least partly induced by the sympathetic nervous system. We conducted a double-blind, randomized, controlled clinical trial to compare the effects of alpha-blockers and beta-blockers on left ventricular structure and function. Forty-three patients with mild to moderate essential hypertension were randomly allocated to receive antihypertensive therapy with either the alpha-blocker bunazosin (n = 23) or the beta-blocker metoprolol (n = 20). Twenty-four-hour blood pressure measurements and echocardiographic measurements of left ventricular structure and function were performed before therapy, after 6 months of therapy, and 4 weeks after discontinuation of therapy. Bunazosin and metoprolol led to similar reductions in systolic/diastolic blood pressure (-11 +/- 11/-9 +/- 8 mm Hg vs -11 +/- 12/-8 +/- 9 mm Hg, respectively) and left ventricular mass (-25 +/- 42 gm vs -28 +/- 44 gm, respectively) (p = no significant difference, bunazosin vs metoprolol). Neither metoprolol nor bunazosin significantly affected left ventricular systolic function. Diastolic left ventricular filling, however, was increased with beta-blocker medication, as indicated by a decrease in atrial filling fraction (39% +/- 5% to 34% +/- 5%; p < 0.05), but not with the alpha-blocker. The effect of metoprolol resulted from its bradycardiac effect. Four weeks after discontinuation of therapy, blood pressure and left ventricular mass increased to pretreatment levels in both groups similarly. Furthermore, the increase in diastolic filling was lost shortly after withdrawal of metoprolol concomitant with the increase in heart rate. We conclude that alpha-blockers and beta-blockers are equally capable of reducing left ventricular mass in hypertensive patients. beta-Blockers lead to an increase in diastolic left ventricular filling. This effect may be of therapeutic value because diastolic dysfunction may precede systolic dysfunction in hypertensive heart disease.

Catecholamines and cardiac growth

The present knowledge concerning the alpha- and beta-adrenergic systems in the regulation of cardiac growth and gene expression is reviewed. To investigate the mechanism by which cAMP regulates the expression of cardiac genes we have used cultured myocytes derived from fetal rat hearts. We have shown previously that the addition of Br cAMP to the culture medium produced an increase in alpha-myosin heavy chain (alpha-MHC) mRNA level, in its rate of transcription as well as in the amount of V1 isomyosin. To characterize the promoter element(s) involved in cAMP responsive regulation of alpha-MHC expression we performed transient transfection analysis with a series of alpha-MHC gene promoter-CAT constructs. We have identified a 13 bp E-box/M-CAT hybrid motif (EM element) which conferred a basal muscle specific and cAMP inducible expression of the alpha-MHC gene. Using mobility shift assay we have documented that one of the EM element binding protein is TEF-1. Moreover, by incubating cardiac nuclear extracts with the catalytic subunit of PK-A we have found that factor(s) binding to the EM element is a substrate for cAMP dependent phosphorylation.

Improvement of coronary flow reserve after long-term therapy with enalapril

To date, no clinical study shows an improvement in coronary flow reserve due to long-term antihypertensive therapy. in view of the contribution of the renin-angiotensin system to the process of hypertensive remodeling of the heart and coronary circulation, angiotensin-converting enzyme (ACE) inhibitors might act as cardioreparative drugs in arterial hypertension. Accordingly, our objective in this investigation was to examine under clinical conditions to what extent long-term antihypertensive treatment with an angiotensin-converting enzyme inhibitor improved the diminished coronary flow reserve in hypertensive patients with microvascular angina pectoris. For the purpose of comparison, we also treated a normotensive control group of 6 patients with hypertrophic nonobstructive cardiomyopathy. Fifteen hypertensive individuals (10 men, 5 women; age, 58 +/- 6 years) were treated with enalapril (10 to 20 mg/d; mean, 16.7 +/- 4.9 mg/d) for 11 to 13 months. At the end of the treatment period, systolic pressure decreased from 178 +/- 14 to 137 +/- 12 mm Hg and diastolic pressure from 102 +/- 11 to 86 +/- 4 mm Hg under ambulatory conditions. Left ventricular muscle mass index decreased by 8%, from 149 +/- 32 to 137 +/- 28 g/m2 (P < .05). Maximal coronary blood flow after dipyridamole was increased by 43%, from 181 +/- 69 to 258 +/- 116 mL/min per 100 g (P < .001), and minimal coronary vascular resistance was diminished by 29%, from 0.66 +/- 0.23 to 0.47 +/- 0.24 mm Hg x min x 100g x mL-1 (P < .001) after enalapril treatment. Consequently, the calculated coronary reserve increased from 2.2 +/- 0.6 to 3.3 +/- 1.2 (P < .001). After enalapril therapy, the functional class of angina pectoris according to the Canadian classification system had changed from 2.5 +/- 0.6 to 1.5 +/- 0.6 (P < .01). The maximal working capacity had increased from 23.775 +/- 3.970 to 26.255 +/- 4.598 J (mean +/- SE, P < .05). The maximal ST-segment depression at maximal work-load was reduced from 0.18 +/- 0.02 to 0.06 +/- 0.02 (mean +/- SE, (P < .01). In summary, long-term therapy with the angiotensin-converting enzyme inhibitor enalapril must be considered a cardioreparative treatment with respect to the coronary microcirculation in hypertensive heart disease.

Alpha1-adrenergic receptor subtype mRNAs are differentially regulated by alpha1-adrenergic and other hypertrophic stimuli in cardiac myocytes in culture and in vivo. Repression of alpha1B and alpha1D but induction of alpha1C

The three cloned alpha1-adrenergic receptor (AR) subtypes, alpha1B, alpha1C, and alpha1D, can all couple to the same effector, phospholipase C, and the reason(s) for conservation of multiple subtypes remain uncertain. All three alpha1-ARs are expressed natively in cultured neonatal rat cardiac myocytes, where chronic exposure to the agonist catecholamine norepinephrine (NE) induces hypertrophic growth and gene transcription. We show here, using RNase protection, that the alpha1-AR subtype mRNAs respond in distinctly different ways during prolonged NE exposure (12 72 h). Alpha1B and alpha1D mRNA levels were repressed by NE, whereas alpha1C mRNA was induced. Changes in mRNA levels were mediated by an alpha1-AR, were not explained by altered mRNA stability, and were reflected in receptor proteins by [3H]prazosin binding. alpha1-AR-stimulated phosphoinositide hydrolysis and myocyte growth were not desensitized. Three other hypertrophic agonists in culture, endothelin-1, PGF2alpha, and phorbol 12-myristate 13-acetate, also induced alpha1C mRNA and repressed alpha1B mRNA. In myocytes from hearts with pressure overload hypertrophy, alpha1 mRNA changes were identical to those produced by NE in culture. These results provide the first example of a difference in regulation among alpha1-AR subtypes expressed natively in the same cell. Transcriptional induction of the alpha1C-AR could be a mechanism for sustained growth signaling through this receptor and is a common feature of a hypertrophic phenotype in cardiac myocytes.

Cardiac insulin-like growth factor I and growth hormone receptor expression in renal hypertension

The aim of the present study was to investigate the role of insulin-like growth factor I in the development of cardiac hypertrophy in two-kidney, one clip hypertension by relating growth hormone receptor and insulin-like growth factor I receptor mRNA levels to insulin-like growth factor I gene transcription using a solution hybridization/RNase protection assay. Two-kidney, one clip hypertension was induced in male Wistar rats, and experiments were performed 2, 4, 7, and 12 days after surgery. Systolic blood pressure was elevated 2, 7, and 12 days after clipping (P < .001). Left ventricular weights were increased 2, 4, 7, and 12 days after surgery (P < .01). Associated with the rise in blood pressure, left ventricular insulin-like growth factor I mRNA was increased 2, 7, and 12 days after surgery (P < .01). Furthermore, growth hormone receptor and insulin-like growth factor I receptor gene expression increased specifically in the left ventricle of renal hypertensive rats (P < .05 and P < .001, respectively). Left ventricular growth hormone receptor mRNA peaked 7 days after induction of renal artery stenosis. These results show that insulin-like growth factor I, growth hormone receptor, and insulin-like growth factor I receptor mRNA increase in the pressure-overloaded left ventricle of two-kidney, one clip rats, suggesting a role for insulin-like growth factor I and the growth hormone/insulin-like growth factor I axis in the development of cardiac hypertrophy.

Is blood pressure the major determinant of left ventricular mass in subjects over 50 years of age?

The weak relation of systolic blood pressure to left ventricular (LV) mass in hypertension has frequently been regarded as evidence of non-hemodynamic stimuli to muscle growth. Anyway, left ventricular hypertrophy (LVH) is associated with a significantly increased risk for cardiovascular events. Data were obtained from M-mode echocardiograms in 10 normotensives and 58 hypertensives over 50 years (range 50-85 years); 18 hypertensives; were without (LVH -) and 40 were with LVH (LVH +) - when LV mass, normalized for body surface area, was calculated according to the Penn's Convention. Cardiac output was derived by Teicholz formula for LV volumes. End-systolic stress/end-systolic dimension ratio (ESS/ ESD r), an index of myocardial contractility, was calculated as previously validated in the literature. We found that, in subjects ranging from 50 to 85 years of age, the presence of LV hypertrophy is not necessarily associated with raised blood pressure levels. Systolic function was substantially preserved among the study groups, irrespective of their age, hypertensive condition and/or presence of LVH. The increased wall thickness in subjects with LVH was associated with a significant reduction in wall stress (thus suggesting an adequateness of the compensatory role of LVH - at least at the observed stage of the hypertrophy process) and with a significant decrease of the contractile performance. On the multivariate analysis, the observed relation of LV mass to blood pressure and myocardial contractility (r = 0.621, P < 0.001) may explain some apparently conflicting findings, such as the lack of LV hypertrophy in a number of hypertensive patients.

Response of hypertensive left ventricular hypertrophy and coronary microvascular disease to calcium antagonists

Hypertensive left ventricular hypertrophy comprises not only myocyte hypertrophy, but is often associated with interstitial fibrosis and structural alterations of the coronary microcirculation. The consequences are early diastolic dysfunction and often later systolic dysfunction of the left ventricle, resulting in congestive heart failure. Involvement of the coronary resistance vessels leads to an impairment of coronary flow reserve despite normal epicardial arteries. Therefore, antihypertensive treatment should aim at reversing myocyte hypertrophy, restoring myocardial structure, and improvement in coronary flow reserve apart from blood pressure lowering. Many clinical studies have shown that calcium antagonists are effective in lowering blood pressure and can induce regression of left ventricular hypertrophy. Moreover, experimental studies have shown a restoration of myocardial structure. Recent clinical studies have demonstrated a marked improvement of the impaired coronary vasodilator reserve in hypertensive patients after long-term treatment with calcium antagonists. In summary, calcium antagonists can be regarded as an antihypertensive treatment modality that is able to restore myocardial structure and to repair coronary microcirculation and therefore can be considered as causative treatment of hypertensive cardiac remodeling.

Reduction by oral propranolol treatment of left ventricular hypertrophy secondary to pressure-overload in the rat

1. Studies on cardiac myocyte cell cultures have postulated a role for alpha 1-adrenoceptors and mechanical stretch in the induction of cellular changes thought to be important in compensatory cardiac hypertrophy. However, in vivo work suggests that beta-adrenoceptors are important and the present study was designed to analyse the effect of propranolol on the cardiac hypertrophy caused by a pressure-overload in a way that takes account of the effects of propranolol on the work load itself. 2. The compensatory cardiac hypertrophy that develops in response to experimental coarctation of the aorta was studied in the rat. Pressure gradients and total cardiac work load (expressed as rate x pressure product) were assessed, and the relationship between increasing cardiac work load and the resulting left ventricular hypertrophy was established in a control group and compared with left ventricular hypertrophy in a group treated with a high dose of oral propranolol (80 mg kg-1 body weight). 3. In the rats with mean pressure gradients over the coarctation in the range of 15-31 mmHg, the animals on control diet showed a 38% increase in left ventricular weight/body weight ratio (LV ratio) and a 30% increase in heart weight/body weight ratio (heart ratio), whereas rats given high dose oral propranolol-treatment showed increases of only 13% and 9%, respectively. 4. In a second series of rats with a wider range of pressure gradients, the regression lines of LV ratio versus mean pressure gradient, and of LV ratio versus cardiac work, were different in the two groups with a slope that was only half as steep in the propranolol-treated rats as in the controls. Thus, for the same increment in cardiac work load, the degree of compensatory cardiac hypertrophy in propranolol-treated rats was half that observed in controls. 5. The reduction in compensatory cardiac hypertrophy was not associated with an increase in incidence of congestive heart failure and the propranolol-treated rats were able to sustain equally high (or higher) degrees of pressure over-load as controls did. 6. It is concluded that propranolol treatment approximately halves the compensatory cardiac hypertrophy occurring in response to a left ventricular pressure over-load by a mechanism independent of its effect on cardiac work load. This finding provides further support for the view that noradrenaline released from sympathetic nerve terminals in the heart exerts a trophic effect on cardiac myocytes, and that the sympathetic nervous system may be the final common pathway in many forms of compensatory cardiac hypertrophy. In contrast to in vitro models, this effect appears to be largely mediated via beta-adrenoceptors in the intact animal.

Reduction by beta-adrenoceptor blockade of hypoxia-induced right heart hypertrophy in the rat

1. The study was undertaken to assess the role of beta-adrenoceptors in the induction of compensatory cardiac hypertrophy in an in vivo model. 2. In the rat, exposure to severe hypoxia (6% inspired oxygen for 8 h day) caused a 51% increase in right heart weight and a 75% increase in haematocrit. 3. The hypoxia-induced right ventricular hypertrophic response was reduced by 65% by oral treatment with a high dose of the non-selective beta-adrenoceptor antagonist, propranolol (80 mg kg-1 body weight); the drug treatment caused only a minor reduction (6%) in secondary polycythaemia. 4. With a less severe degree of hypoxia (7% inspired oxygen) there was only minimal secondary polycythaemia (+15%), and a lesser degree of compensatory right ventricular hypertrophy in untreated rats (+33%). 5. Treatment with the beta 1-adrenoceptor antagonist, atenolol, in a dose of 80 mg kg-1 body weight abolished right ventricular hypertrophy in response to 7% inspired oxygen, without affecting haematocrit and caused a small reduction in the ratio of heart weight to body weight in normoxic rats. 6. The results show that the effect of propranolol on hypoxic right ventricular hypertrophy is not secondary to any effect on secondary polycythaemia as has previously been suggested and that a marked reduction of compensatory cardiac hypertrophy can be obtained by a beta 1-selective adrenoceptor antagonist. Thus these findings support the view that noradrenaline released from cardiac sympathetic nerve terminals exerts a trophic effect on myocardial cells and demonstrates that in vivo, this trophic effect can be reduced by beta 1-adrenoceptor blockade.

Improvement of cardiovascular effects of metoprolol by replacement of common salt with a potassium- and magnesium-enriched salt alternative

1. The influence of sodium chloride (NaCl)-enrichment of the diet (6% of the dry weight) and that of a novel sodium-reduced, potassium-, magnesium-, and L-lysine-enriched salt alternative on the cardiovascular effects of the beta 1-adrenoceptor blocking drug, metoprolol, was studied in stroke-prone spontaneously hypertensive rats. 2. Increased dietary sodium chloride intake produced a marked rise in blood pressure and induced left ventricular and renal hypertrophy. By contrast, the salt alternative did not increase blood pressure and caused remarkably less cardiac and renal hypertrophy than did sodium chloride. 3. Metoprolol treatment at a daily dose of 250 mg kg-1 lowered blood pressure and decreased left ventricular hypertrophy index during the control diet. Sodium chloride-enrichment blocked the antihypertensive effect of metoprolol, while a partial protective effect on left ventricular and renal hypertrophy persisted. In the presence of the salt alternative-enrichment both at the level of 6% and 10.5% (corresponding to a NaCl level of 6%), metoprolol was fully able to exert its beneficial cardiovascular and renal effects. 4. Both salt supplementations, irrespective of metoprolol treatment, induced a 3 to 4 fold increase in the urinary excretion of calcium. There was a linear correlation between the urinary excretions of sodium and calcium. The urinary excretion of magnesium rose by 90% and that of potassium by 110% in the salt alternative group. 6. Our findings suggest that replacement of common salt by a potassium-, and magnesium-enriched salt alternative in the diet produces beneficial cardiovascular effects and improves the antihypertensive efficacy of metoprolol in stroke-prone spontaneously hypertensive rats. Increased intake of potassium and/or magnesium and L-lysine from the salt alternative is involved in the beneficial effects of the salt alternative. The NaCl-induced myocardial and renal hypertrophies appear to be partially mediated by Beta-adrenoceptor activation.

Salt intake, blood pressure, and cardiovascular structure

Epidemiologic data revealed that a low sodium intake might have a favorable influence on blood pressure throughout an individual's lifetime. Sodium restriction was reported to lead to a modest fall in blood pressure in some studies, although a few groups of hypertensive patients experienced a rise in blood pressure. Left ventricular hypertrophy has been demonstrated to be related to cardiovascular morbidity and mortality independent of other risk factors. Dietary salt intake participates in the hypertrophic process independent of other determinants. Thus, 24-hour urinary sodium excretion has been reported to correlate with left ventricular mass independent of levels of arterial pressure. Three different mechanisms may link dietary salt intake to myocardial hypertrophy: the renin-angiotensin-aldosterone system, the sympathetic nervous system, and fluid volume homeostasis. Whether salt restriction reduces cardiovascular structural damage independent of arterial pressure has not been determined.

Cardiovascular effects of felodipine are not antagonized by dietary salt

Increased dietary intake of regular salt (sodium chloride) interferes markedly with the therapeutic effects of angiotensin converting enzyme inhibitors. To study further the interactions between dietary salt intake and antihypertensive drug treatment, we examined the effects of felodipine, a dihydropyridine derivative Ca2+ channel antagonist with natriuretic properties, on blood pressure and the development of left ventricular hypertrophy in the stroke-prone spontaneously hypertensive rats during different levels of sodium chloride in the diet. We also compared the influence of regular salt on the cardiovascular effects of felodipine with that of a novel K(+)-, Mg(2+)- and l-lysine-enriched and Na(+)-reduced salt alternative, which in previous studies markedly improved the therapeutic effects of enalapril and ramipril. During the 28-day experiment regular salt produced a marked rise in blood pressure and induced left ventricular hypertrophy, while the salt alternative neither induced any rise of blood pressure nor caused cardiac hypertrophy. Felodipine had an enhanced antihypertensive effect during the increased intake of sodium chloride, and lowered the blood pressure to the same normotensive level as it did during the control and the salt alternative diets. Felodipine also completely blocked the development of the sodium chloride-induced cardiac hypertrophy. The heart rate of the felodipine-treated animals was significantly increased during the first two study weeks but thereafter it did not differ from that of the controls. Hence, unlike regular salt, the novel Na(+)-reduced, K(+)-, Mg(2+)-, and l-lysine-enriched salt alternative did not raise blood pressure and produced little if any left ventricular hypertrophy.(ABSTRACT TRUNCATED AT 250 WORDS)