Mechanisms of disease: pathologic structural remodeling is more than adaptive hypertrophy in hypertensive heart disease

Changes in the composition of cardiac tissue develop in arterial hypertension and lead to structural remodeling of the myocardium. Structural remodeling is the consequence of a number of pathologic processes, mediated by mechanical, neurohormonal and cytokine routes, occurring in the cardiomyocyte and the noncardiomyocyte compartments of the heart. One of these processes is related to the disruption of the equilibrium between the synthesis and degradation of collagen type I and III molecules, which results in an excessive accumulation of collagen type I and III fibers in the interstitium and the perivascular regions of the myocardium. The clinical relevance of ventricular fibrosis is that it might contribute to the increased cardiac risk of patients with hypertensive heart disease. This review focuses on the mechanisms of hypertensive ventricular fibrosis and its clinical consequences. In addition, we discuss the noninvasive methods for the diagnosis of cardiac fibrosis and the therapeutic strategies aimed to promote its reduction.

Usefulness of plasma cardiotrophin-1 in assessment of left ventricular hypertrophy regression in hypertensive patients

OBJECTIVE

We investigated whether regression of left ventricular hypertrophy (LVH) in response to antihypertensive treatment is associated with plasma cardiotrophin-1 (CT-1) in hypertensive patients.

METHODS

The study was performed in 47 patients with mild to moderate essential hypertension, and LVH was assessed echocardiographically. The family doctor gave antihypertensive treatment and followed all patients. LVH regression was diagnosed if the baseline left ventricular mass index (LVMI) decreased to normal values after 1 year of treatment. Plasma CT-1 was determined by an enzyme-linked immunosorbent assay.

RESULTS

The LVMI was normalized in 23 patients (49%) and persisted at an abnormally increased level in 24 patients (51%) after 1 year of treatment, whereas the reduction in clinic and home blood pressure was similar in the two groups: CT-1 decreased (-48%, P < 0.005) and increased (+35%, P < 0.05) in patients in whom LVH regressed and LVH persisted, respectively. Final values of CT-1 were inversely correlated (r = 0.534, P < 0.001) with the decrease in LVMI after treatment in all patients. A significant association (chi2 = 16.87, P < 0.001) was found between normalization of CT-1 and regression of LVH with treatment. A cut-off value of 41 fmol/ml for CT-1 provided a relative risk of 43.13 (95% confidence interval, 4.88-380.48) for detecting LVH regression.

CONCLUSION

These results show an association between treatment-induced decrease of plasma CT-1 and LVH regression in essential hypertension. Although preliminary, these findings suggest that the determination of plasma CT-1 may be useful for the follow-up of hypertensive heart disease in routine clinical practice.

Myocardial fibrosis, impaired coronary hemodynamics, and biventricular dysfunction in salt-loaded SHR

Arterial pressure in most experimental and clinical hypertensions is exacerbated by salt. The effects of salt excess on right and left ventricular (RV and LV, respectively) functions and their respective coronary vasodilatory responses have been less explored. We therefore examined the effects of 8 wk of NaCl excess (8% in food) on arterial pressure, RV and LV functions (maximal rate of increase and decrease of ventricular pressure; dP/dt(max) and dP/dt(min)), coronary hemodynamics (microspheres), and collagen content (hydroxyproline assay and collagen volume fraction) in young adult normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR), aged 16 wk by the end of the study. Prolonged salt excess in WKY and SHR elevated pressure only modestly, but it markedly increased LV mass, especially in SHR. Moreover, salt excess significantly impaired RV and LV diastolic function in SHR but only LV diastolic function in WKY rats. However, salt loading affected neither RV nor LV contractile function in both strains. Interstitial and perivascular collagen deposition was increased, whereas coronary vasodilatory responses to dipyridamole diminished in both ventricles in the salt-loaded SHR but not in WKY rats. Therefore, accumulation of ventricular collagen as well as altered myocardial perfusion importantly contributed to the development of salt-related RV and LV dysfunctions in this model of naturally occurring hypertension. The unique effects of salt loading on both ventricles in SHR, but not WKY rats, strongly suggest that nonhemodynamic mechanisms in hypertensive disease participate pathophysiologically with salt-loading hypertension. These findings point to the conclusion that the concept of "salt sensitivity" in hypertension is far more complex than simply its effects on arterial pressure or the LV.

New directions in the assessment and treatment of hypertensive heart disease

PURPOSE OF REVIEW

This article will review briefly the emerging new concepts in the diagnosis and treatment of myocardial fibrosis in patients with hypertensive heart disease.

RECENT FINDINGS

Although hypertensive heart disease is characterized clinically by development of left-ventricular hypertrophy in the absence of a cause other than arterial hypertension, changes in the composition of myocardial tissue also develop in arterial hypertension leading to structural remodeling of the myocardium (e.g. fibrosis). Recent available data on the determination of serum concentrations of collagen-derived serum peptides and quantitative analysis of echoreflectivity to address the presence of fibrosis in the myocardium of hypertensive patients are promising. In addition, preliminary data suggest that the goal of reducing myocardial fibrosis is achievable in patients with hypertensive heart disease using specific antihypertensive agents (e.g. those interfering with angiotensin II).

SUMMARY

The time has come to revisit the current management of hypertensive heart disease simply focused on detecting left-ventricular hypertrophy and controlling blood pressure to reduce left-ventricular mass. It is necessary to develop new approaches aimed at assessing and repairing alterations of myocardial structure and protect myocardial function and, in so doing, to reduce in a more-effective manner adverse risk associated with hypertensive heart disease.

The use of collagen-derived serum peptides for the clinical assessment of hypertensive heart disease

Given the importance of fibrous tissue in leading to myocardial dysfunction and failure in hypertensive heart disease, non-invasive assessment of fibrosis could prove a clinically useful tool in hypertensive patients, particularly given the potential for cardioprotective and cardioreparative pharmacological strategies. In this regard, an emerging experimental and clinical experience holds promise for the assessment of various serum peptides arising from the metabolism of collagen types I and III in arterial hypertension. More specifically, the measurement of serum concentrations of procollagen type I carboxy-terminal propeptide (a peptide that is cleaved from procollagen type I during the synthesis of fibril-forming collagen type I) may provide indirect diagnostic information on both the extent of myocardial fibrosis and the ability of antihypertensive treatment to diminish collagen type I synthesis and reduce myocardial fibrosis in hypertensive patients. The available data set the stage for large and long-term trials to definitively validate this approach.

Is plasma cardiotrophin-1 a marker of hypertensive heart disease?

OBJECTIVE

This study was designed to investigate whether plasma concentration of cardiotrophin-1 (CT-1), a cytokine that induces cardiomyocyte hypertrophy and stimulates cardiac fibroblasts, is related to hypertensive heart disease, as defined by the presence of echocardiographically assessed left ventricular hypertrophy (LVH).

METHODS

The study was performed in 31 normotensive subjects and 111 patients with never-treated essential hypertension (54 without LVH and 57 with LVH). Causes of LVH other than hypertension were excluded after a complete medical workup. A novel enzyme-linked immunosorbent assay was developed to measure plasma CT-1.

RESULTS

Plasma CT-1 was increased (P < 0.001) in hypertensives compared with normotensives. The value of CT-1 was higher (P < 0.001) in hypertensives with LVH than in hypertensives without LVH. Some 31% of patients without LVH exhibited values of CT-1 above the upper normal limit in normotensives. A direct correlation was found between CT-1 and left ventricular mass index (r = 0.319, P < 0.001) in all subjects. Receiver operating characteristic curves showed that a cutoff of 39 fmol/ml for CT-1 provided 75% specificity and 70% sensitivity for predicting LVH with a relative risk of 6.21 (95% confidence interval, 2.95 to 13.09).

CONCLUSIONS

These results show an association between LVH and the plasma concentration of CT-1 in essential hypertension. Although preliminary, these findings suggest that the determination of CT-1 may be an easy and reliable method for the initial screening and diagnosis of hypertensive heart disease.

Increased collagen type I synthesis in patients with heart failure of hypertensive origin: relation to myocardial fibrosis

BACKGROUND

We investigated whether increased collagen type I synthesis and deposition contribute to enhancement of myocardial fibrosis and deterioration of cardiac function in patients with hypertensive heart disease (HHD).

METHODS AND RESULTS

We studied 65 hypertensives with left ventricular hypertrophy subdivided into 2 groups: 34 patients without heart failure (HF) and 31 patients with HF. Transvenous endomyocardial biopsies of the interventricular septum were performed to quantify the amount of fibrotic tissue and the extent of collagen type I deposition. The carboxy-terminal propeptide of procollagen type I (PIP), an index of collagen type I synthesis, was measured by radioimmunoassay in serum samples from the coronary sinus and the antecubital vein. Compared with normotensives, the amount of collagen tissue, the extent of collagen type I deposition, and coronary and peripheral PIP were increased (P<0.01) in the 2 groups of hypertensives. These parameters were also increased (P<0.01) in HF hypertensives compared with non-HF hypertensives. Coronary PIP was higher (P<0.01) than peripheral PIP in hypertensives but not in normotensives. The amount of collagen tissue was inversely correlated with the ejection fraction and directly correlated with both coronary and peripheral PIP in all hypertensives.

CONCLUSIONS

These findings suggest that an excess of cardiac collagen type I synthesis and deposition may be involved in the enhancement of myocardial fibrosis that accompanies the development of HF in HHD. In addition, our data show that the heart secretes PIP via the coronary sinus into the peripheral circulation in patients with HHD. Thus, PIP determined in peripheral blood can be a useful marker of myocardial fibrosis in these patients.

Different effects of antihypertensive therapies based on losartan or atenolol on ultrasound and biochemical markers of myocardial fibrosis: results of a randomized trial

BACKGROUND

In hypertensive left ventricular hypertrophy (LVH), myocardial texture is altered by a disproportionate increase in fibrosis, but there is insufficient clinical evidence whether antihypertensive therapy or individual agents can induce regression of myocardial fibrosis.

METHODS AND RESULTS

We compared the effects of an angiotensin II receptor antagonist with a beta-blocker on myocardial collagen volume (assessed by echoreflectivity and serum collagen markers) in 219 hypertensive patients with echocardiographically documented LVH. Patients were allocated randomly to receive losartan 50 to 100 mg/d (n=111) or atenolol 50 to 100 mg/d (n=99) with or without hydrochlorothiazide 12.5 to 25 mg/d for 36 weeks. Echoreflectivity analysis was conducted on ultrasound tracings of the midapex septum with specifically designed and validated software. A color histogram of reflecting echoes was obtained, and its spread (broadband [BB], previously shown to correlate directly with collagen volume fraction on endomyocardial biopsies) was used as the primary outcome measure. Mean color scale and serum markers of collagen synthesis (PIP, PIIIP) or degradation (CITP) were secondary outcome variables. Echoreflectivity analysis proved feasible in 106 patients (losartan 52, atenolol 54). Losartan reduced BB over 36 weeks (from 114.5 to 104.3 color levels, P<0.02), whereas atenolol treatment was associated with an increase in BB (from 109.0 to 113.6 color levels, P=NS), the difference between treatments being -12.8 color levels (95% CI -23.6 to -2.0, P=0.02). Secondary end points (mean color scale and collagen markers) also changed in the direction of decreased collagen in patients receiving losartan, but differences between groups were not statistically significant.

CONCLUSIONS

In hypertensive patients with LVH, losartan decreases myocardial collagen content, whereas atenolol does not. The difference between the 2 treatments is statistically significant.

Role of matrix metalloproteinases in hypertension-associated cardiac fibrosis

PURPOSE OF REVIEW

The potential contribution of alterations in matrix metalloproteinase activity to the development of myocardial fibrosis in hypertensive heart disease is reviewed.

RECENT FINDINGS

A number of experimental and clinical studies provide information on alterations in the balance between matrix metalloproteinase-1 or collagenase and tissue inhibitor of matrix metalloproteinases-1, which result in depressed proteolytic activity of the enzyme in animals and humans with hypertensive heart disease. While some recent data point to a genetic origin of such an imbalance, other findings suggest that depressed collagenase activity may contribute to disturbances of cardiac function via facilitation of myocardial fibrosis. On the other hand, emerging information is providing the basis for the notion that other matrix metalloproteinases, namely gelatinases, may participate in the process of myocardial fibrosis through stimulation of fibrillar collagen synthesis. Some fragmented matrix peptides or matrikines may be the mediators of the profibrotic action of these matrix metalloproteinases.

SUMMARY

The matrix metalloproteinases represent an important biological system within the myocardium designed to maintain the complex and dynamic microenvironment of the extracellular matrix. Improved understanding of how this system is dysregulated in hypertensive heart disease will probably provide new insights into, and strategies for, heart failure.

The A1166C polymorphism of the AT1 receptor gene is associated with collagen type I synthesis and myocardial stiffness in hypertensives

OBJECTIVES

We have investigated whether the A1166C polymorphism of the angiotensin II type 1 (AT1) receptor gene modulates the effects of angiotensin II on collagen type I turnover and myocardial stiffness in hypertension.

METHODS

We studied 255 hypertensive patients before and after 1 year of treatment with either losartan (n = 185) or atenolol (n = 70). Serum concentrations of the carboxy-terminal propeptide of procollagen type I (PIP) and the carboxy-terminal telopeptide of collagen type I (CITP), markers of extracellular collagen type I synthesis and degradation, respectively, were measured by specific radioimmunoassays. Left ventricular chamber stiffness (KLV), was determined from the deceleration time of the early mitral filling wave, as measured by Doppler echocardiography. Hypertensives were genotyped by polymerase chain reaction and divided in two subgroups: AA (n = 126) and AC/CC (n = 129).

RESULTS

Baseline PIP and KLV were increased (P < 0.01) in AA hypertensives compared with AC/CC hypertensives. No changes in baseline CITP were observed between the two subgroups of hypertensives. Confounding factors were similar between the two subgroups of hypertensives. Administration of losartan was associated with reduction (P < 0.01) in PIP and KLV in AA hypertensives but not in AC/CC hypertensives. Treatment with atenolol did not change PIP and KLV in either subgroup of hypertensives. No changes in CITP were observed with the two treatments.

CONCLUSION

These findings suggest that the A1166C polymorphism of the AT1 receptor gene is associated with collagen type I synthesis and myocardial stiffness in patients with hypertensive heart disease.

Effects of loop diuretics on myocardial fibrosis and collagen type I turnover in chronic heart failure

OBJECTIVES

This individually randomized, open-label, parallel-group pilot study was designed to test the hypothesis that the ability of loop diuretics to interfere with cardiac fibrosis in chronic heart failure (CHF) may be different between compounds.

BACKGROUND

The apparent mortality and cardiac benefits seen in studies comparing torasemide with furosemide in CHF suggest that torasemide may have beneficial effects beyond diuresis (e.g., on the process of cardiac fibrosis).

METHODS

Patients with New York Heart Association functional class II to IV CHF received diuretic therapy with either 10 to 20 mg/day oral torasemide (n = 19) or 20 to 40 mg/day oral furosemide (n = 17), in addition to their existing standard CHF therapy for eight months. At baseline and after eight months, right septal endomyocardial biopsies were obtained to quantify collagen volume fraction (CVF) with an automated image analysis system. Serum carboxy-terminal peptide of procollagen type I (PIP) and serum carboxy-terminal telopeptide of collagen type I (CITP), indexes of collagen type I synthesis and degradation, respectively, were measured by specific radioimmunoassays.

RESULTS

In torasemide-treated patients, CVF decreased from 7.96 +/- 0.54% to 4.48 +/- 0.26% (p < 0.01), and PIP decreased from 143 +/- 7 to 111 +/- 3 microg/l (p < 0.01). Neither CVF nor PIP changed significantly in furosemide-treated patients. In all patients, CVF was directly correlated with PIP (r = 0.88, p < 0.001) before and after treatment. No changes in CITP were observed with treatment in either group.

CONCLUSIONS

These findings suggest that loop diuretics possess different abilities to reverse myocardial fibrosis and reduce collagen type I synthesis in patients with CHF.

Cardiomyocyte apoptosis in hypertensive cardiomyopathy

It is widely accepted that there are two principal forms of cell death; namely, necrosis and apoptosis. According to the classical view, necrosis is the major mechanism of cardiomyocyte death in cardiac diseases. However, in the past few years observations have been made showing that cardiomyocyte apoptosis occurs in diverse conditions and that apoptosis may be a contributing cause of the loss and functional abnormalities of cardiomyocytes with important pathophysiological consequences. In this regard, although a number of formal proofs are pending, it is conceivable that cardiomyocyte apoptosis may be an important variable in the clinical evolution of hypertensive cardiomyopathy. This review summarizes recent evidence demonstrating that cardiomyocyte apoptosis is abnormally stimulated in the heart of animals and humans with arterial hypertension. In addition, the potential mechanisms of cardiomyocyte apoptosis in hypertension and its detrimental impact on cardiac function will be addressed. Finally, the perspectives of strategies aimed to detect and modulate apoptosis of cardiomyocytes in hypertensive cardiomyopathy will be considered.

Fibrosis in hypertensive heart disease: role of the renin-angiotensin-aldosterone system

Structural homogeneity of cardiac tissue is governed by mechanical and humoral factors that regulate cell growth, apoptosis, phenotype, and extracellular matrix turnover. ANGII has endocrine, autocrine, and paracrine properties that influence the behavior of cardiac cells and matrix by AT1 receptor binding. Various paradigms have been suggested, including ANGII-mediated up-regulation of collagen types I and III formation and deposition in cardiac conditions, such as HHD. A growing body of evidence, however, deals with the potential role of aldosterone, either local or systemic, in inducing cardiac fibrosis. Aldosterone might also mediate the profibrotic actions of ANGII. To reduce the risk of heart failure that accompanies HHD, its adverse structural remodeling (eg, myocardial hypertrophy and fibrosis) must be targeted for pharmacologic intervention. Cardioprotective agents must reverse not only the exaggerated growth of cardiac cells, but also regress existing abnormalities in fibrillar collagen. Available experimental and clinical data suggest that agents interfering with ACE, the AT1 receptor, or the mineralocorticoid receptor may provide such a cardioprotective effect.

A marked difference in pathogenesis and immune response induced by different Mycobacterium tuberculosis genotypes

In the last decade, an unprecedented genetic diversity has been disclosed among Mycobacterium tuberculosis strains found worldwide. However, well-conserved genotypes seem to prevail in areas with high incidence of tuberculosis. As this may be related to selective advantages, such as advanced mechanisms to circumvent [M. bovis Bacille Calmette-Guerin (BCG)-induced] host defence mechanisms, we investigated the influence of strain diversity on the course of experimental disease. Twelve M. tuberculosis strains, representing four major genotype families found worldwide today, and the laboratory strain H37Rv were each used to infect BALB/c mice by direct intratracheal injection. Compared with H37Rv, infections with Beijng strains were characterized by extensive pneumonia, early but ephemeral tumour necrosis factor-alpha (TNF-alpha) and inducible isoform of nitric oxide synthetase (iNOS) expression, and significantly higher earlier mortality. Conversely, Canetti strains induced limited pneumonia, sustained TNF-alpha and iNOS expression in lungs, and almost 100% survival. Strains of the Somali and the Haarlem genotype families displayed less homogeneous, intermediate rates of survival. Previous BCG vaccination protected less effectively against infection with Beijing strains than against the H37Rv strain. In conclusion, genetically different M. tuberculosis strains evoked markedly different immunopathological events. Bacteria with the Beijing genotype, highly prevalent in Asia and the former USSR, elicited a non-protective immune response in mice and were the most virulent. Future immunological research, particularly on candidate vaccines, should include a broad spectrum of M. tuberculosis genotypes rather than a few laboratory strains.

[ROC curve analysis of factors predictive of response to treatment with interferon plus ribavirin in patients with chronic hepatitis C relapse after previous interferon treatment]

This study aimed to identify the factors predictive of response before the initiation of treatment and throughout the treatment period in patients with chronic hepatitis C relapse after treatment with interferon-a who were retreated with a standard regimen of interferon-a plus ribavirine and followed up for 40 months. Forty-four patients (40 with genotype 1, four without genotype 1) were included in the study. Four patients (genotype 1) were excluded because of adverse effects. The rate of maintained response was 55% (50% genotype 1, 100% non-genotype 1). The stage of histological damage (>2), glutamic-pyruvic transaminase (GPT) concentration (< or = 26 UI/l) and the association between the GPT concentration and the detection of the RNA-HCV in the first and third treatment months were the variables with an area under the ROC curve and a confidence interval >0.5. The probability of predicting a maintained response (negative predictive value) if the stage of histological lesion was <2 was 62.9%, while the positive predictive value was 100%. During the treatment, the disappearance of the RNA-HCV together with GPT values < or =26 in the first treatment month were the best predictive values. In this case, the negative predictive value was 78.3% and the positive predictive value was 76.5% (OR: 11.7, 2.6-52.2). Furthermore, the GPT value with the best predictive value (<26 UI/l) was a more effective predictor of the response to treatment than the normal value of the GPT. Finally, the GPT values >26 UI/l and the detection of RNA/HCV in the first or third treatment month were certain predictors of the absence of response but with low sensitivity (10-12%). It was concluded that is possible to predict the response to the combined treatment with an acceptable level of confidence, although not unequivocally. Ninety percent of the patients would be candidates for maintaining treatment for at least 6-12 months, while approximately 10% could undergo early interruption of treatment due to the absence of response.

Regulation of myocardial fibrillar collagen by angiotensin II. A role in hypertensive heart disease?

Collagen types I and III (Col I and Col III) are the major fibrillar collagens produced by fibroblasts and myofibroblasts in the adult heart. Fibrillar collagen of the heart provides the structural scaffolding for cardiomyocytes and coronary vessels and imparts cardiac tissue with physical properties that include stiffness and resistance to deformation. In addition, fibrillar collagen may also act as a link between contractile element of adjacent cardiomyocytes and as a conduit of information that is necessary for cell function. As in other organs, collagen turnover of normal adult heart results from the equilibrium between the synthesis and degradation of Col I and Col III. A number of factors have been described that may alter the balance in favor of either the synthesis (e.g., angiotensin II-ANG II-) or the degradation. Predominance of synthesis over degradation leads to increased Col I and Col III deposition or fibrosis that accompanies cardiac diseases such as hypertensive heart disease. Fibrosis alters myocardial structure and function and adversely afects the clinical outcome of hypertensive patients. Various lines of evidence suggest that besides hypertension, systemically and/or locally produced ANG II may participate in the development of hypertensive myocardial fibrosis via activation of ANG II type 1 receptors (AT(1)R). The potential clinical relevance of this possibility is linked to the ability of antihypertensive drugs such as angiotensin converting enzyme inhibitors (ACEIs) and AT(1)R antagonists (ARAs) to reverse myocardial fibrosis beyond their antihypertensive efficacy.

[False-positive cultures due to cross contamination in tuberculosis laboratories]

Fifteen episodes of Mycobacterium tuberculosis laboratory cross-contamination suspected between 1996 and 2001 at 6 laboratories in Buenos Aires City and suburbs were investigated by IS6110 RFLP. Thirteen episodes were confirmed. Even though BACTEC 460 produced the highest number of confirmed episodes in a single laboratory, the most extended one occurred while employing conventional culture procedures in solid medium. The double repetitive element-polymerase chain reaction (DRE-PCR) was applied to 8 of these episodes and produced concordant results with those of the RFLP. The DRE-PCR appears to be a valuable tool for the prompt identification of false positive cultures. The timely rectification of defects in laboratory protocols can avert false diagnoses of tuberculosis and unnecessary prolonged treatments.

Losartan-dependent regression of myocardial fibrosis is associated with reduction of left ventricular chamber stiffness in hypertensive patients

BACKGROUND

This study was designed to investigate whether myocardial collagen content is related to myocardial stiffness in patients with essential hypertension.

METHODS AND RESULTS

The study was performed in 34 patients with hypertensive heart disease. Nineteen of these patients were also evaluated after 12 months of treatment with losartan. Transvenous endomyocardial biopsies of the interventricular septum were performed to quantify collagen volume fraction (CVF). Left ventricular (LV) chamber stiffness (K(LV)) was determined from the deceleration time of the early mitral filling wave as measured by Doppler echocardiography. Histological analysis at baseline revealed the presence of 2 subgroups of patients: 8 with severe fibrosis and 26 with nonsevere fibrosis. Values of CVF and K(LV) were significantly higher in the 2 subgroups of hypertensives than in normotensives. In addition, compared with patients with nonsevere fibrosis, patients with severe fibrosis exhibited significantly increased values of CVF and K(LV). After treatment, CVF and K(LV) decreased significantly in patients with severe fibrosis (n=7). None of these parameters changed significantly after treatment in patients with nonsevere fibrosis (n=12). CVF was directly correlated with K(LV) (r=0.415, P<0.02) in all hypertensives.

CONCLUSIONS

These findings show a strong association between myocardial collagen content and LV chamber stiffness in patients with essential hypertension. Our results also suggest that the ability of losartan to induce regression of severe myocardial fibrosis is associated with diminution of myocardial stiffness in hypertensive patients.

Stimulation of cardiac apoptosis in essential hypertension: potential role of angiotensin II

We investigated whether cardiac apoptosis is stimulated in the heart of hypertensive patients and whether angiotensin II plays a role in such alteration. The study was performed in 28 patients with essential hypertension and no evidence of either ischemic cardiomyopathy or heart failure. After randomization, 14 patients were assigned to losartan and 14 patients to amlodipine treatment. At baseline and after 12 months, right septal endomyocardial biopsies were performed, and the number of apoptotic nuclei was assessed by DNA end-labeling (TUNEL). In addition, immunostaining for the active form of caspase-3 was also performed to assess apoptosis. Compared with normotensive autopsied hearts, both cardiomyocyte and noncardiomyocyte apoptosis were increased (P<0.001) in hypertensive hearts. Time-course changes in blood pressure during treatment were similar in the 2 groups of patients. In losartan-treated patients, both cardiomyocyte and noncardiomyocyte apoptosis decreased (P<0.05). Neither cardiomyocyte nor noncardiomyocyte apoptosis changed significantly in amlodipine-treated patients. These findings indicate that apoptosis is abnormally stimulated in the heart of patients with essential hypertension. Our data also suggest that the ability of antihypertensive treatment to inhibit cardiac apoptosis is independent of its antihypertensive efficacy. We propose that angiotensin II may participate in the stimulation of cardiac apoptosis in essential hypertension.

[Study of Mycobacterium bovis in milk using bacteriological methods and the polymerase chain reaction]

The frequency of Mycobacterium bovis detection in milk samples obtained from infected animals was explored in an intensive dairy area in Argentina. To this end, an "in house" polymerase chain reaction (PCR) method was developed using Mycobacterium tuberculosis Complex specific INS1-INS2 primers, and its performance was compared with that of bacteriological methods. The decontamination procedures previous to culture reduced M. bovis viability. The pathogen was identified in milk samples from 1 of 143 infected cows and in none of 43 uninfected ones. Even though PCR sensitivity was found to be 2-20 times higher than that of bacteriology in experimentally inoculated milk samples, all 186 field samples resulted negative by PCR, including the bacteriologically-confirmed one. In spite of the high prevalence of bovine tuberculosis in Argentinian dairy herds, the detection of M. bovis in milk is an unusual finding.

Clinical aspects of hypertensive myocardial fibrosis

Myocardial fibrosis is one of the histologic constituents of myocardial remodeling present in hypertensive patients with hypertensive heart disease. In fact, an exaggerated interstitial and perivascular accumulation of fibrillar collagens type I and type III has been found in the myocardium of patients with arterial hypertension and left ventricular hypertrophy. Hypertensive myocardial fibrosis has been shown to facilitate abnormalities of cardiac function, coronary reserve, and electrical activity that adversely affect the clinical outcome of hypertensive patients. Therefore, development of noninvasive tools for the monitoring of myocardial fibrosis and pharmacological strategies aimed to promote the regression of fibrosis could be of particular relevance in the clinical treatment of patients with hypertensive heart disease.