The psychosocial and psychiatric side of cystic fibrosis in adolescents and adults

Increasing numbers of cystic fibrosis (CF) patients are surviving into adulthood. An understanding of the psychiatric and psychosocial aspects of CF in adults and adolescents is therefore more important than ever. There is a large body of evidence indicating that the psychological and psychosocial functioning of people with CF is similar to that of well people, until the disease becomes severe. However, there is also evidence that patients do suffer an increased likelihood of psychiatric problems, such as depression, and of scoring poorly on physical functioning measures of quality of life. Studies have found conflicting evidence as to any association between degree of respiratory impairment and psychological functioning. Coping styles seem to have a large effect upon the quality of life of CF patients. People with cystic fibrosis can have problems with sexuality, platonic relationships and independence. Families of patients also suffer problems, which can affect the patients themselves. Non-compliance is a complicated problem with many patients. New treatments for people with CF are emerging, such as lobe transplants from live donors and gene therapy, with possible new psychosocial problems resulting. Furthermore, older studies are becoming increasingly inapplicable as treatment and prognosis changes. Therefore, more research is needed in this field.

Activation of Cardiac c-Jun NH 2 -Terminal Kinases and p38-Mitogen–Activated Protein Kinases With Abrupt Changes in Hemodynamic Load

Abstract —The role of mitogen-activated protein kinase (MAPK) pathways as signal transduction intermediates of hemodynamic stress leading to cardiac hypertrophy in the adult heart is not fully established. In a rat model of pressure-overload hypertrophy, we examined whether activation of MAPK pathways, namely, the extracellular signal–regulated protein kinase (ERK), c-Jun NH 2 -terminal kinase (JNK), and the p38-MAPK pathways, occurs during rapid changes in hemodynamic load in vivo. A slight activation of ERK2 and marked increases in JNK1 and p38-MAPK activities were observed 30 minutes after aortic banding. The increase in p38-MAPK activity was accompanied by an increase in the phosphorylation of the p38 substrate MAPK–activated protein kinases 2 and 3. Activation of these kinases was coincident with an increase in phosphorylation of c-Jun and activating transcription factor-2 (ATF-2) and enhanced DNA binding of activator protein-1 factors. Thus, hemodynamic stress of the adult rat heart in vivo results in rapid activation of several parallel MAPK kinase cascades, particularly stress-activated MAPK and p38-MAPK and their target transcription factors c-Jun and ATF-2.

Endothelin-A receptor antagonism during acute myocardial infarction in rats

Endothelin levels are increased in rats with experimentally induced myocardial infarction. The purpose of this study was to determine whether endothelin-A (ET(A)) receptor antagonism alters ventricular remodeling and the development of heart failure after myocardial infarction (MI). We administered 10 mg/kg/day of A-127722 to rats post-MI for 6 weeks. A hemodynamic study was performed and passive pressure-volume curves obtained. In rats without infarcts, ET(A) receptor antagonist (n = 8; vehicle, n = 5) had no effect. However, in rats with infarcts ET(A) antagonism (n=14, MI = 35%; vehicle: n = 19, MI = 32%) reduced systemic arterial and LV systolic (but not end-diastolic) pressures and shifted the pressure-volume relationship to the right. Because LV mass was not changed, the volume-to-mass ratio was increased and was correlated inversely with the ability of the LV to maximally develop pressure. This increase in volume at low distending pressures was also coupled with a tendency (P < 0.06) for reduced scar thickness, suggesting that early initiation of an ET(A) receptor antagonism increased infarct expansion. The reduction in blood pressure offset the increase in volume such that wall stresses were unchanged, as was LV mass. The early use of ET(A) receptor antagonism in the rat model of myocardial infarction did not beneficially alter LV remodeling.

Temporal dissociation of left ventricular function and remodeling following experimental myocardial infarction in rats

BACKGROUND

Left ventricular function early after myocardial infarction (MI) predicts subsequent clinical outcome. Nevertheless, the relationship between early changes in left ventricular function and subsequent left ventricular remodeling has not been well defined.

METHODS AND RESULTS

To explore the temporal relationship between left ventricular function and remodeling after MI, rats (n = 63) underwent coronary artery ligation with and without reperfusion at 45 or 180 minutes or a sham operation. All animals were followed up by serial echocardiography preligation; 4, 24, and 48 hours; and 1, 2, 3, 4, 6, and 9 weeks after MI. Measures of global left ventricular size and function and regional wall motion were obtained at physiological heart rates. Histological infarct sizes (range, 0% to 52%) were determined in all animals. Within 4 hours of MI, fractional area change (FAC) decreased dramatically in association with an increase in left ventricular systolic cavity area, whereas diastolic area increased more gradually. Early FAC was related to infarct size (r = -0.82; P < .000), predicted the extent of left ventricular enlargement (P = .0001), and remained depressed throughout the duration of follow-up. Regional wall motion excursion and systolic wall thickness decreased in the infarcted and noninfarcted regions in animals with large infarctions.

CONCLUSIONS

The rate of left ventricular dilatation after MI in rats is proportional to initial left ventricular function, although left ventricular function remains relatively constant as the ventricle progressively enlarges. Regional myocardial function after a large MI is abnormal in noninfarcted as well as infarcted regions.

Inducible nitric oxide synthase and tumor necrosis factor in animal models of myocardial necrosis induced by coronary artery ligation or isoproterenol injection

BACKGROUND

Increased expression of inducible nitric oxide synthase (iNOS) has been described in humans with cardiomyopathies. Most animal models of ischemia-induced heart failure use the surgical ligation of coronary arteries. However, studies of iNOS expression in these models may be confounded by a robust immune response because of the surgical procedure itself leading to iNOS expression in the heart, as well as in other tissues.

METHODS AND RESULTS

iNOS expression was studied in adult male rats injected subcutaneously with either 250 mg/kg of isoproterenol (ISO) or vehicle on 2 consecutive days. This approach induces diffuse myocardial necrosis and leads to the development of a dilated cardiomyopathy. Hearts from ISO-injected animals harvested at 6 weeks had evidence of apical and subendocardial scarring. These hearts showed a 9.6-fold (left ventricle [LV], P = .004) and an 11.9-fold (right ventricle, P = .002) increase in the expression of tumor necrosis factor (TNF), and a 6.8-fold increase (LV, P = .0183) in iNOS messenger RNA compared with vehicle-injected controls. iNOS protein also was detectable by immmunoprecipitation in left ventricular muscle from ISO-injected animals, as well as by immunohistochemical analysis.

CONCLUSION

Expression of TNF and iNOS in the heart is increased in an experimental model of dilated cardiomyopathy that minimizes the confounding effects of surgery, supporting a role for the activation of innate immunity signaling pathways in the pathogenesis of heart failure.

Effects of reperfusion on arrhythmias and death after coronary artery occlusion in the rat: increased electrical stability independent of myocardial salvage

OBJECTIVES

This study sought to delineate salvage-dependent from salvage-independent coronary reperfusion in acute myocardial infarction and the effects on spontaneously occurring arrhythmias and arrhythmic death in rats.

BACKGROUND

Reperfusion of the infarct-related artery might increase electrical stability independently of salvage of ischemic myocardium.

METHODS

In 98 conscious rats the electrocardiogram was monitored by telemetry for 48 h after MI, and all episodes of ventricular tachycardia (VT) and ventricular fibrillation (VF) were analyzed. Reperfusion at 45 min (RP45) (n = 15), 90 min (RP90) (n = 18) and 180 min (RP180) (n = 30) min was compared with permanent coronary artery occlusion (CAO) (n = 35) with respect to the post-reperfusion periods.

RESULTS

RP45, RP90 and RP180 reduced the incidence of VT by 93%, 98% and 88% and VF by 89%, 97% and 92%, respectively (all p < 0.01 vs. CAO). The all-cause mortality rate was reduced from 47% (CAO) to 8% (RP45, p < 0.05) and 0% (RP90, p < 0.01); after RP180 it was 17% (CAO 42%, p = 0.08). All reperfusion regimens reduced arrhythmic deaths: 47% to 8% (RP45, p < 0.05), 47% to 0% (RP90, p < 0.01) and 42% to 8% (RP180, p < 0.05). Infarct size was identical to that during CAO (49 +/- 10% [mean +/- SD]) and RP180 (49 +/- 10%), whereas preferentially epicardial salvage occurred at RP45 (36 +/- 8%, p < 0.001) and RP90 (38 < 10%, p < 0.001).

CONCLUSIONS

Early and late reperfusion reduce the incidence and duration of VT and VF in conscious rats with acute MI. Thereby, arrhythmia-related mortality is improved through the prevention of fatal VF episodes. Thus, reperfusion increases the electrical stability of the heart independently of myocyte salvage, as proposed by the open artery hypothesis.

Effect of left ventricular sphericity on the evolution of ventricular dysfunction in rats with diffuse isoproterenol-induced myocardial necrosis

BACKGROUND

Previous studies in heart failure have suggested that increased left ventricular (LV) sphericity is a precursor to hemodynamic deterioration, although these studies have predominantly used models with segmental damage due to coronary vessel occlusion and have only made baseline assessments of LV function. The purpose of this study was to examine the relationship between LV geometry and hemodynamic compromise through time in heart failure due to graded, diffuse myocardial injury with a patent coronary circulation.

METHODS AND RESULTS

Rats received two injections of either 0, 85, 170, or 340 mg/kg isoproterenol. At 2, 6, and 16 weeks after injection, baseline hemodynamics, peak pressure-generating (aortic occlusion) and flow-generating (Tyrode's volume loading) capacities, and ventricular pressure-volume curves, dimensions, and histological scoring were measured. Increased LV sphericity preceded deterioration in baseline cardiac output, although it was the most powerful correlate of the dose-dependent decreases in peak cardiac output and ejection fraction. Time-dependent increases in pressure-generating capacity at a given volume were also due to compensatory increases in LV sphericity. The extent of right ventricular damage was also a strong correlate of peak flow-generating capacity.

CONCLUSIONS

This study demonstrates that isoproterenol-induced myocardial necrosis resulted in progressive hemodynamic dysfunction of the left ventricle which most closely correlated with alterations in LV geometry. Although increases in LV sphericity preceded decrements in baseline function, techniques that assessed peak LV function demonstrated that increased LV sphericity was directly correlated with decreased peak flow-generating capacity, underscoring the clinical importance of these geometric alterations.

The heart and conduit vessels in hypertension

The heart and conduit vessels, integral components of a pulsatile pumping system, undergo complex adaptive and degenerative changes in response to the increased load of hypertension. Over the last two decades, great technological strides have been made with regards to further discovering the role of the heart and conduit vessels in hypertension. This article reviews the adaptation of the heart and vessels to hypertension, the clinical implications of these structural and functional changes, and the effects of therapy on cardiovascular function.

Cardiac myocyte membrane wounding in the abruptly pressure-overloaded rat heart under high wall stress

The potential role of transient sarcolemmal membrane wounding as a signal transduction event for cardiomyocyte hypertrophy was evaluated in rats with short-term pressure overload caused by banding of the proximal aorta. This procedure resulted in significant increases in left ventricular systolic (1.5-fold) and end-diastolic (2.6-fold) pressures and wall stresses that were associated with significant wall thinning and cavitary enlargement. Quantitative image analysis of frozen sections of the stressed ventricles obtained 60 minutes after banding demonstrated a 6- to 10-fold increase in cytosolic staining with a horseradish peroxidase-labeled anti-albumin antibody compared with sham-operated controls, indicating that an increase in transient sarcolemmal membrane permeability (wounding) is an early response to an abrupt increase in hemodynamic load in vivo. We conclude that an intense hemodynamic stress in vivo can result in histologically detectable cardiomyocyte wounding.

Comparison of techniques for measuring pulse-wave velocity in the rat

We evaluated methods for measuring average and regional pulse-wave velocity along the full length of the aorta in 18-mo-old ether-anesthetized male spontaneously hypertensive rats. Catheter-tip manometers were placed in the ascending and descending thoracic aorta via the right carotid and left femoral arteries, respectively. As the distal catheter was withdrawn at 1-cm intervals, the relationship between the distal catheter insertion distance and distance between transducers was determined from the intercept of the insertion distance vs. transmission delay regression line. Methods that assessed the foot-to-foot time delay between pressures accurately predicted the separation between catheters (measured distance of 1.43 cm; intercept of 1.40 +/- 0.5 cm; P = not significant) were highly reproducible (coefficient of variation of 2.3% for repeated measurements) and showed minimal variability (range 509 +/- 30 to 600 +/- 29 cm/s) along the full length of the aorta. Methods that made use of the pressure-pressure transfer function were spatially (range of values along the aorta 367 +/- 17 to 722 +/- 39 cm/s) and temporally more variable, especially during vasoconstriction with methoxamine, due to the effects of reflected waves.

Equipotent antihypertensive agents variously affect pulsatile hemodynamics and regression of cardiac hypertrophy in spontaneously hypertensive rats

BACKGROUND

Converting enzyme inhibitors are more effective than arteriolar vasodilators at regressing left ventricular hypertrophy in spontaneously hypertensive rats (SHR), possibly because of nonhemodynamic factors. However, the pulsatile component of hemodynamic load has not been evaluated in this model.

METHODS AND RESULTS

We measured pulsatile hemodynamics in 18-month-old male SHR after 6 months of therapy with either zofenopril (Z), hydralazine (H), or water (W). Hydralazine and zofenopril reduced mean arterial pressure comparably (W, 106 +/- 23 versus H, 81 +/- 12 versus Z, 84 +/- 18 mm Hg, P = .002) yet had a differential effect on the ratio of left ventricular weight to body weight (W, 3.9 +/- 0.5 versus H, 3.3 +/- 0.4 versus Z, 2.4 +/- 0.2 g/kg, P < .005). Hydralazine-treated SHR had increased characteristic impedance (P = .0011) and a persistently low ratio of the reflected-wave transit time to left ventricular ejection time (P < .001), which contributed to early and late systolic loading, respectively, of the left ventricle. Consequently, only zofenopril-treated SHR had a significant reduction in left ventricular systolic force-time integral (P = .02), a measure of total ventricular load. There were no differences in systolic stress-time integral, suggesting that mass was appropriate to load when all elements of steady-flow and pulsatile load were considered.

CONCLUSIONS

A blunted reduction in total left ventricular load, due to increased pulsatile load in SHR treated with hydralazine, provided a hemodynamic basis for the differential regression of hypertrophy in this model of genetic hypertension.

Arrhythmias and death after coronary artery occlusion in the rat. Continuous telemetric ECG monitoring in conscious, untethered rats

BACKGROUND

The onset of acute myocardial infarction (MI) is accompanied by a rapid increase in electrical instability and often fatal ventricular arrhythmias. The aim of this study was to assess the continuous arrhythmia profile during the initial 48 hours after coronary artery ligation in the rat in relation to time course, mortality, and infarct size.

METHODS AND RESULTS

Continuous ECG recording were obtained in 26 conscious, untethered rats for 24 hours before and 48 hours after coronary ligation by use of an implantable telemetry system. All episodes of ventricular tachycardia and fibrillation were counted and their durations summed. Infarct size was measured at 48 hours after MI or after spontaneous death. After ligation, two distinctly active arrhythmogenic periods developed (A1, 0 to 0.5 hours; A2, 1.5 to 9 hours), each followed by a quiescent phase of low ectopy (Q1, 0.5 to 1.5 hours; Q2, 10 to 48 hours). The total mortality rate of 65% was found within the two active periods, with 13 of 15 deaths occurring in A2. Rats with larger infarcts (> or = 50%) and nonsurvivors tended to have increased arrhythmia frequency and duration compared with both animals with smaller MIs (< 50%) and survivors.

CONCLUSIONS

Two distinct arrhythmogenic periods occur in rats with acute MI that may be caused by different mechanisms and correspond to the bimodal arrhythmia time course seen in dogs and humans after acute MI. Telemetric monitoring of the ECG in the conscious rat after infarction will be useful in assessment of the differential effects of therapeutic interventions on these two arrhythmogenic periods and in the study of potential mechanisms for the spontaneous resolution of ventricular ectopy and risk of sudden death.

Measurement of aortic input impedance in rats

Measurement of aortic input impedance in the rat is complicated by a high basal heart rate but is possible if appropriate compensation is made for frequency-dependent errors in modulus and phase resulting from analog filters in the equipment and from nonalignment of pressure and flow sensors. Because input impedance is a complex quantity, accurate values for both phase and modulus are required before meaningful interpretation of the data can be made. We measured aortic pressure and electromagnetic ascending aortic blood flow in mature, ether-anesthetized, open-chest male Wistar rats. Pressure and flow waveforms were averaged in the time domain and converted to Fourier series. Flow moduli were corrected for the measured frequency response of the flowmeter. Phase spectra were corrected by the classic frequency-domain and two new time-domain methods. Compensation for instrumentation errors was assessed at two different flowmeter filter settings in five animals. Reproducibility, variability, and the effects of vasoconstriction were assessed in 43 animals. Three methods of estimating characteristic impedance from the impedance spectra were evaluated and found to produce comparable results at baseline and following pharmacological elevation of blood pressure with graded methoxamine infusion. Physiologically equivalent values for phase, as assessed by comparing oscillatory power calculated from the impedance spectra, were obtained with each of the phase-correction techniques. The new time-domain methods facilitate the assessment of aortic input impedance in this small animal model because they do not require measurement of the spatial separation between pressure and flow transducers and pulse wave velocity in the proximal aorta.

Regression of left ventricular hypertrophy as viewed from the periphery

Despite the advances in antihypertensive therapy, the majority of patients who develop heart failure have antecedent hypertension, left ventricular hypertrophy, and a poor prognosis. Studies in animals and humans have shown that equipotent antihypertensive agents variously effect the regression of cardiac hypertrophy, one of the reasons for which may be the differences in their effects on vascular load and structure. Recent advances in instrumentation (micromanometers, applanation tonometers, ultrasonic probes, and so forth) have permitted the noninvasive measurement of pressure contours, vessel diameters, and pulse-wave velocity. This new technology has allowed the evaluation of the effects of antihypertensive agents on arterial compliance and structure in relation to the agent's ability to regress left ventricular hypertrophy.

Progressive ventricular remodeling in response to diffuse isoproterenol-induced myocardial necrosis in rats

The purpose of the present study was to gain a better understanding of the relation between ventricular remodeling and heart failure by assessing the adaptation of the heart through time to graded myocardial injury in the presence of a patent coronary circulation. Left ventricular (LV) remodeling is a dynamic response of the heart to injury and a critical component in the development of heart failure. However, most previous studies have been in the presence of an occluded coronary vessel, which may in itself effect remodeling. Male Wistar rats received two subcutaneous injections of either 0, 85, 170, or 340 mg isoproterenol per kilogram of body weight. At 2, 6, and 16 weeks after injection, LV pressure, the pressure-volume relation, and histology were assessed. The graded myocardial necrosis produced in isoproterenol-treated rats was associated with dose-dependent increases in LV end-diastolic pressure, volume indexes, and global diastolic wall stress. In the higher dose groups, the LV continued to enlarge after 2 weeks, resulting in a further reduction in the ratio of LV mass to volume and a persistent rise in diastolic wall stress. These progressive changes in LV structure were associated with an increase in long-term mortality in rats from the intermediate- and high-isoproterenol dose groups. The present study in rats demonstrates that diffuse isoproterenol-induced myocardial necrosis results in a progressive enlargement of the LV cavity that is out of proportion to mass, a finding similar to that observed in discrete myocardial infarction.

Development and prevention of congestive heart failure following myocardial infarction

Ischemic heart disease is the major etiology for the development of congestive heart failure. Patients with acute myocardial infarction have a greatly increased risk for mortality and for manifesting symptomatic heart failure. This risk is not a uniform one but is greatly augmented in patients with a more extensive infarction and, consequently, a more depressed global ventricular function. An important concept that was derived from studies in rats with myocardial infarction and has been confirmed in patients is that ventricular enlargement, which has been shown to be a marker for an adverse outcome, can be a progressive process that leads to further deterioration of ventricular performance. Both experimental and early clinical studies have indicated that chronic therapy with an angiotensin converting enzyme inhibitor may attenuate this progressive ventricular enlargement. More definitive clinical trials are currently under way to determine whether this form of therapy, which may diminish the extent of ventricular enlargement over time, will result in an improvement in survival and in the prevention of the development of congestive heart failure. The addition of this pharmacological therapy to that of the primary prevention of atherosclerosis and that of the limitation of infarct size should make a substantial impact on the reduction of the incidence of congestive heart failure.

Progressive ventricular dilation in experimental myocardial infarction and its attenuation by angiotensin-converting enzyme inhibition

The extent to which the impaired left ventricle dilates may have important prognostic implications for survival. To determine the influence of infarct size and duration on ventricular dilation, the passive pressure-volume relation of the left ventricle in the rat after coronary artery ligation was obtained. In the early (0.25 to 2 days) phase, the pressure-volume relation was relatively unchanged in all infarct-size groups, except for a rightward shift in the low pressure range for moderate and large infarcts and a leftward shift in the high pressure range for small infarcts. From 2 to 7 days, ventricular dilatation occurred in all groups in relation to infarct size. Thereafter (to 106 days), in rats with moderate and large infarcts, the left ventricle continued to dilate. Associated with this late dilation was a decrease in left ventricular chamber stiffness and an increase in the volume to mass ratio. To determine whether the potentially deleterious progression of ventricular dilation could be attenuated, the angiotensin-converting enzyme inhibitor captopril was given 2 or 21 days after infarction and continued for 3 months. There was a significant overall effect of this treatment in attenuating left ventricular dilation, which was most pronounced in moderate infarcts. Captopril not only attenuated the rightward shift of the pressure-volume relation, but also markedly lowered left ventricular filling pressures so that operating volumes in treated rats were considerably reduced compared with those in untreated rats, even in large infarcts. Therapy with captopril also had an overall effect in prolonging survival, the most benefit being observed in moderate infarcts with lesser dilated left ventricles.

Progressive ventricular remodeling in rat with myocardial infarction

Ventricular dilatation may have important prognostic implications for the survival of patients with left ventricular (LV) dysfunction. To determine the manner and extent to which the left ventricle of the rat remodels and dilates after myocardial infarction, we obtained the passive pressure-volume relationships, chamber stiffness constants, and mass during both the early and late phases. In moderate and large infarcts as inflammation and edema developed, LV weight increased then progressively decreased as a thin scar formed, returning to normal values as a result of compensatory hypertrophy of the residual myocardium. LV dilatation occurred in all rats with infarcts but to different extents depending on infarct size and duration. In the early postinfarction phase, pressure-volume relationship was relatively unchanged in all infarct-size groups, except for significant rightward shift in low pressure range for rats with moderate and large infarcts and significant leftward shift in high pressure range for rats with small infarcts. During resolution of the inflammatory response, LV dilatation occurred in all infarct groups in relation to infarct size. As scar formation became complete, LV enlargement did not progress in rats with small infarcts but did so in rats with moderate and large infarcts. LV chamber stiffness remained within the range of normal values during the early phase in all rats with infarcts but decreased significantly during the late phase in rats with moderate and large infarcts in association with the extent of ventricular enlargement. Alterations in the volume-to-mass ratio (V/Vwt) were most marked in the late postinfarction phase, wherein both volume (increased) and mass (decreased, then increased) changed dramatically and V/Vwt progressively increased in rats with large infarcts.

Systemic hemodynamic effects of endothelin in rats

Endothelin type 1 (ET-1) is an endothelial cell-derived 21-amino acid peptide with potent contractile effects on isolated vascular smooth muscle. The systemic hemodynamic effects of bolus intravenous injections of ET-1 and angiotensin II (ANG II, 300 pmol) were examined in anesthetized male Munich-Wistar rats by measurements of mean arterial (AP) and right atrial (RAP) blood pressures and cardiac index (CI, electromagnetic flowmetry) over a 60-min period. ET-1 induced a biphasic pressure response: transient hypotension occurred in the early phase with all doses, followed by a more prolonged dose-dependent elevation of blood pressure in the late phase. Because CI was unchanged during the early phase, the hypotension resulted from systemic vasodilation. On the other hand, the marked rise in AP produced by 300 pmol of ET-1 in the late phase was associated with a significant fall in CI, and thus total peripheral resistance index (TPRI) increased profoundly. A fall in right atrial pressure and significant hemoconcentration were associated with this pronounced vasoconstrictor effect, suggesting that a contraction of plasma volume contributed to the reduction of CI. Additionally, stroke and minute work indexes and peak flow velocity became significantly reduced in the late phase for the 300-pmol dose of ET-1. When compared with an equimolar dose of ET-1, 300 pmol of ANG II produced a prompt, more marked, but shorter-lived rise in AP with minimal changes in CI, TPRI, RAP, and hematocrit. These results raise the intriguing possibility that endothelin may play a role in both the control of normal vascular smooth muscle tone and in the pathogenesis of vasospastic disorders.

Angiotensin converting enzyme inhibition and ventricular remodeling in heart failure

The prevention or attenuation of the development of heart failure by the angiotensin converting enzyme inhibitor captopril was examined in two animal models, spontaneously hypertensive rats and rats with myocardial infarction produced by coronary artery ligation. In 24-month-old female spontaneously hypertensive rats with marked left ventricular hypertrophy, cardiac output was reduced despite an increase in ventricular volume, resulting in a greatly reduced ejection fraction. Treatment with captopril from 14 to 24 months of age maintained forward output and prevented ventricular dilatation so that ejection fraction remained normal; left ventricular hypertrophy regressed to levels observed in six-month-old spontaneously hypertensive rats. In rats with moderate and large infarcts three months after ligation, left ventricular filling pressures were elevated, forward output was reduced, and ventricular volumes were greatly increased. Long-term therapy with captopril maintained filling pressures within normal limits and maintained forward output from a lesser dilated left ventricle to yield an ejection fraction that was elevated compared with that in untreated rats. Thus, the potentially deleterious remodeling of the left ventricle in heart failure, an extensive increase in mass and chamber volume, can be favorably altered by long-term angiotensin converting enzyme inhibition (captopril) with salutary effects on hemodynamics.

Atrial natriuretic factor gene expression in ventricles of rats with spontaneous biventricular hypertrophy

A subset of Wistar-Kyoto (WKY) rats that spontaneously develops biventricular hypertrophy (BVH) in response to increased cardiac output was evaluated for ventricular expression of the atrial natriuretic factor (ANF) gene. Normal WKY rats had low levels of left ventricular ANF mRNA and minimally detectable ANF transcripts in the right ventricle. In contrast, BVH rats showed a sixfold greater ANF mRNA concentration in the left ventricle than age-matched WKY controls. BVH right ventricular ANF mRNA levels equaled those found in BVH left ventricles and were dramatically greater than WKY right ventricular controls. Unlike experimental models of hypertrophy, both left and right ventricles significantly increase ANF gene transcripts in the natural development of BVH. The left and right ventricles can concordantly respond to hypertrophy and increase ANF gene transcription.

Papillary muscle structure-function relations in the aging spontaneously hypertensive rat

Isolated left ventricle papillary muscle mechanics and structure were studied in male spontaneously hypertensive (SHR) rats and two control groups of animals, the normotensive Wistar (NR) and the Wistar-Kyoto rat (WKY). Active tension and its first derivative (dT/dtmax) normalized for muscle cross-sectional area were increased in preparations from the SHR at all ages studied relative to control groups (P less than 0.01). However, when these parameters were normalized for myofibrillar cross-sectional area determined from electronmicroscopic point counting data, differences between groups were no longer significant. Force-velocity relations provided no evidence for a depression of shortening velocity at any load in the SHR at any age relative to the two control groups. The duration of mechanical activity, as determined by time-to-peak isometric tension and analysis of muscle force-velocity-time relations, was prolonged only in the 18 month old SHR (P less than 0.01). Thus, while changes in isolated muscle performance occur at a time when hemodynamic impairment is reported in the intact animal (male 18 month SHR), no evidence for depression of isolated muscle function is seen in the SHR at 6, 12 or 18 months of age.

Atrial natriuretic peptide transcription, storage, and release in rats with myocardial infarction

To study the role of atrial natriuretic peptide (ANP) in chronic heart failure, ANP synthesis, storage, and release were examined by measuring atrial ANP messenger ribonucleic acid (mRNA) levels and atrial and plasma ANP concentrations in rats with myocardial infarction produced by coronary artery ligation. Three groups were defined as the following: 1) controls, sham-operated, or operated, but noninfarcted; 2) moderate infarcts, involving 5-30% of the left ventricular circumference; and 3) large infarcts (greater than or equal to 30%). In addition, to determine a possible modulation by dietary Na intake on ANP levels in heart failure, plasma immunoreactive ANP (iANP) levels were measured in rats with and without infarcts given low, regular, or high Na intake for 2 wk, by which time all groups were in neutral balance. Plasma iANP levels varied directly with increasing infarct and atrial sizes, irrespective of Na intake. In contrast, atrial ANP concentration varied inversely with increasing infarct size. The ANP mRNA content index, a measure of total atrial ANP mRNA, was significantly increased in rats with large infarcts compared with control rats. These results indicate that in rats with myocardial infarction, the severity of left ventricular dysfunction, as inferred from infarct size, but not chronic Na intake, is the primary determinant of the extent of activation of the ANP system. Elevated circulating ANP levels are maintained through enhanced atrial synthesis and release. ANP may thus play an important role in the hemodynamic and renal adaptations to chronic heart failure.

Plasma nonesterified fatty acids in the Dahl rat. Response to salt loading

The link between dietary salt intake and the development of hypertension in the salt-sensitive Dahl strain of rats remains elusive. There is evidence that Dahl salt-sensitive rats (DS) produce less vasodilator and natriuretic prostaglandins in response to salt loading than do control salt-resistant rats (DR), although the reason for this blunted response is unknown. We examined the effects of chronic dietary salt loading on the plasma levels of nonesterified fatty acids in DS and DR. Animals were fed the same chow containing either 0.4% or 4% NaCl (wt/wt). At 12 weeks, 75 microliters of tail capillary blood was obtained from restrained, conscious rats, and principal nonesterified fatty acids were measured by high performance liquid chromatography. Total nonesterified fatty acids rose in the 15 DR on high salt diets compared with values in 11 rats eating low salt (0.57 +/- 0.05 vs 0.35 +/- 0.01 mM; p less than 0.001). The greatest changes occurred in levels of arachidonic acid (+287%) and in the arachidonic precursors, linoleic (+89%) and linolenic (+107%) acids. In marked contrast, there was no change in levels of plasma nonesterified fatty acids in DS fed 4% NaCl compared with DS fed 0.4% NaCl. These observations suggest that defective production of natriuretic and vasodilator prostaglandins by DS may be due in part to an inability to produce or release eicosanoid precursors from phospholipid stores in response to dietary salt.

Ventricular enlargement and reduced survival after myocardial infarction

Increased ventricular volume is one of the most powerful predictors of reduced survival in patients with heart disease. Despite its well-documented prognostic significance, the magnitude of the progression of ventricular dilatation from the acute to the chronic phase of myocardial infarction has only recently been appreciated. In an experimental preparation of myocardial infarction in rats, left ventricular cavitary volume increased progressively even after histologic resolution of the infarct region. We hypothesized that this remodeling of the infarcted left ventricle was a response to an increase in both systolic and diastolic wall stresses and that captopril, by reducing wall stress, would attenuate the process. For comparably sized infarcts, the captopril-treated rats had smaller ventricular volumes at common distending pressures, yet they had maintained or improved cardiac output. Most importantly, long-term captopril therapy also prolonged the survival of these rats with experimental myocardial infarction. The implication of these animal studies is that the potential exists for the attenuation of progressive ventricular enlargement and improvement of survival of patients recovering from a myocardial infarction. At the present time, no information is available in patients as to the therapeutic potential of interrupting this insidious process of ventricular dilatation in order to improve survival. Clinical trials are required to determine whether salutary benefits similar to those observed in animals can be provided to patients recovering from a myocardial infarction.

Hemodynamic benefits and prolonged survival with long-term captopril therapy in rats with myocardial infarction and heart failure

To determine whether the hemodynamic profile of chronic heart failure secondary to myocardial infarction could be altered, captopril was administered to female Wistar rats 3 weeks after coronary artery ligation and continued for 3 months. Captopril reduced left ventricular mass, prevented the increase in right ventricular mass observed with increasing infarct size, lessened the increase in left ventricular end-diastolic pressure, and reduced mean arterial pressure and total peripheral resistance, whereas cardiac output and heart rate were maintained. The end-diastolic volume of treated rats with moderate infarcts was significantly less than that of untreated rats, and therefore the ejection fraction index was significantly increased. In rats given captopril until death or for a period of up to 1 year, survival was significantly prolonged, particularly in those rats with moderate-sized infarcts.

The behavioural approach in medical practice

This paper gives a description of the behavioural approach, behaviour therapy, and behavioural medicine in a medical and general hospital setting and describes the intimate link between behaviour and illness, showing how knowledge of the way learning takes place and influences behaviour can lead to a better understanding of the aetiology of illness and thus to appropriate treatment. A behavioural approach can be applied to the understanding and treatment of medical problems associated with sphincteric disturbances, such as childhood encopresis and urinary retention, as well as to the improvement of patient compliance and to the better management of pain. In the field of preventive medicine this approach is of importance in modifying behaviour associated with cardiovascular disorders, obesity, and smoking.

Renal and systemic hemodynamic effects of synthetic atrial natriuretic peptide in the anesthetized rat

To characterize the hemodynamic events responsible for alterations in renal function during administration of atrial natriuretic peptide, we studied the systemic, renal, and glomerular circulatory effects of intravenous rANP[126-149], administered as a 4 micrograms/kg prime and 0.5 microgram/kg per minute continuous infusion in anesthetized, euvolemic rats. With this protocol, a small decline in mean systemic arterial blood pressure occurred in the context of markedly enhanced urinary sodium excretion, hemoconcentration, and reduced left ventricular end-diastolic pressure and +dP/dt. However, despite a significant decrement in renal vascular resistance, total peripheral resistance remained constant, thereby denoting a preferential renal vasodilatory effect of this peptide in vivo. Whole kidney and single nephron GFR increased by approximately 20%, while effective renal and glomerular plasma flow rates remained stable, resulting in a substantial rise in filtration fraction. Of all the parameters potentially capable of augmenting single nephron GFR, only glomerular capillary hydraulic pressure increased significantly and therefore accounted entirely for the hyperfiltration observed during ANP infusion. This rise in glomerular capillary pressure, in turn, resulted from afferent arteriolar vasodilatation and concurrent efferent arteriolar vasoconstriction, findings that proved independent of both endogenous angiotensin II activity and ANP-induced reductions in renal perfusion pressure. These renal hemodynamic effects are unique when compared with actions of previously studied renal vasodilatory agents.

Altered sensitivity to increases in vascular resistance in rats with hypertension and myocardial infarction

Left ventricular dysfunction reduces the ability of the heart to maintain forward output when subjected to the additional stress of an increased vascular resistance. To determine the extent to which hearts from rats with both hypertension and myocardial infarction are sensitive to increases in vascular resistance, spontaneously hypertensive rats (SHR) and normotensive Wistar rats (NWR) with and without myocardial infarction (coronary artery ligation) were infused with methoxamine (0.08 to 1.6 mg/kg/min). Mean arterial pressure during methoxamine infusion was significantly lower in infarcted rats than in noninfarcted rats in each strain, due largely to a lower cardiac output in infarcted rats. When compared at equal pressures, the infarcted groups of each strain generated a lower cardiac output than did the respective noninfarcted groups, as a result of both a lower stroke volume and heart rate. During the methoxamine infusion, absolute pressure levels in SHR with large infarcts were similar to those in NWR. Thus, infarcted hearts from both hypertensive and normotensive rats, when subjected to the stress of an increase in vascular resistance, demonstrated an impairment of pumping ability that was related to the extent of left ventricular damage. Impaired pressure-generating capacity was most pronounced in SHR with large infarcts, which were unable to generate hypertensive levels of blood pressure.

Survival after an experimental myocardial infarction: beneficial effects of long-term therapy with captopril

Although vasodilator therapy has been shown to improve functional capacity in patients with congestive heart failure, there is no evidence that such therapy can prolong survival. Coronary artery ligation in the rat was used to produce a wide range of myocardial infarct sizes and a resultant spectrum of left ventricular dysfunction. To determine the relationship between size of myocardial infarction and long-term survival and to test the hypothesis that long-term therapy with captopril could improve survival after myocardial infarction, 302 rats were randomly assigned to either placebo or captopril therapy 14 days after coronary artery ligation. The animals were kept in a laminar flow unit and followed daily for a 1 year period or until spontaneous death. Size of myocardial infarction was determined by planimetry of serial histologic sections of the left ventricle. One year survival in placebo-treated rats decreased markedly in direct relation to increasing size of infarction (from 71% in noninfarcted rats to only 8% in rats with large infarcts). Long-term captopril therapy prolonged the survival of rats with infarcts (p less than .02). The most marked improvement in survival was noted in the animals with infarcts of moderate size, in which 1 year survival was 21% in the placebo-treated rats and 48% in the captopril-treated rats. Thus, in this experimental preparation of myocardial infarction and left ventricular dysfunction, survival was inversely related to size of infarction. Long-term therapy with captopril, which we had previously shown to improve left ventricular function and lessen dilatation in the chronic phase of infarction, also had a pronounced effect on prolonging survival in this preparation of chronic infarction.

Influence of chronic captopril therapy on the infarcted left ventricle of the rat

To determine whether the relationship between infarct size and ventricular performance, volume, and compliance could be altered favorably, captopril was administered to rats for 3 months following coronary artery ligation. Baseline left and right ventricular and systemic arterial pressures and aortic blood flow, and maximal stroke volume and cardiac indices attained during a volume loading, were measured. Passive pressure-volume relations of the left ventricle were determined, and the slopes of segments of this relation were analyzed to characterize ventricular chamber stiffness. In untreated rats, left ventricular end-diastolic pressure progressively rose (from 5-28 mm Hg) as a function of infarct size, whereas, in captopril-treated rats, filling pressure remained within normal limits (5 +/- 1 mm Hg) in all but those with extensive infarcts. Chronic captopril therapy reduced baseline mean arterial pressure and total peripheral resistance, yet maintained cardiac and stroke outputs in rats both with and without infarcts. In untreated rats, maximal pumping ability progressively declined with increasing infarct size, whereas, in captopril-treated rats, peak stroke volume index remained within normal limits in all but those with extensive infarcts. The in vitro left ventricular volumes of captopril-treated rats were significantly less than those of untreated rats. The maintenance of forward output from a lesser dilated left ventricle yielded an index of ejection fraction for treated rats with moderate and large infarcts that was significantly elevated compared with that of untreated rats with infarcts of comparable size. Left ventricular chamber stiffness, which fell as infarct size increased in untreated rats, was normalized by chronic captopril therapy. Thus, captopril attenuated the left ventricular remodeling (dilation) and deterioration in performance that were observed in rats with chronic myocardial infarction.

Role of angiotensin II in the altered renal function of congestive heart failure

Glomerular and tubule functions were assessed by micropuncture in rats with extensive myocardial infarction produced by ligation of the left coronary artery 4 weeks prior to study. When compared to sham-operated control rats, rats with myocardial infarction involving 40 +/- 4% of the left ventricular circumference had lower mean arterial pressure (96 +/- 5 vs. 122 +/- 4 mm Hg, P less than 0.005), and higher left ventricular end-diastolic pressure (24 +/- 3 vs. 5 +/- 0 mm Hg, P less than 0.001). Renal cortical microcirculatory dynamics of rats with myocardial infarction were characterized by reduced glomerular plasma flow rate (75 +/- 8 vs. 165 +/- 17 nl/min, P less than 0.005), but a proportionately lesser decline in single nephron glomerular filtration rate (28.0 +/- 2.8 vs. 41.7 +/- 3.1 nl/min, P less than 0.025), accounting for the observed rise in single nephron filtration fraction (0.38 +/- 0.02 vs. 0.25 +/- 0.02, P less than 0.005). These renal hemodynamic alterations in myocardial-infarcted rats were accompanied by a striking elevation in efferent arteriolar resistance (3.03 +/- 0.31 vs. 0.95 +/- 0.16 X 10(10) dyn X sec X cm-5, P less than 0.001). In addition, fractional proximal fluid reabsorption, assessed by end-proximal tubule fluid-to-plasma inulin concentration ratio, was elevated (2.21 +/- 0.12 vs. 1.64 +/- 0.09, P less than 0.025). The intravenous infusion of teprotide, an angiotensin I-converting enzyme inhibitor, led to the return of glomerular plasma flow rate, single nephron filtration fraction, single nephron glomerular filtration rate, efferent arteriolar resistance, and fractional proximal fluid reabsorption in myocardial-infarcted rats to, or toward, the levels found in control rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Ventricular performance in rats with myocardial infarction and failure

Ventricular performance was assessed in rats three weeks following coronary artery ligation and the subsequent production of a wide range of infarct sizes. The entire spectrum of ventricular dysfunction was observed, from minimal impairment to overt congestive heart failure. Rats with small infarcts ejected normal baseline and volume-stressed forward outputs from a modestly dilated ventricular chamber. Rats with moderate infarcts exhibited normal baseline hemodynamics but had a reduced reserve flow capacity when challenged with a volume load despite considerable ventricular dilatation. Rats with large infarcts demonstrated frank congestive heart failure with elevations in both left and right ventricular filling pressures and consequent right ventricular hypertrophy; marked reductions in both baseline and volume-stressed forward outputs; and ventricular volumes that were twice those of rats without infarcts. Thus, a progressive impairment in ventricular performance and an increase in chamber volume occurred in relation to infarct size in rats with healed myocardial infarction.

Renal and systemic hemodynamic responses to intravenous infusion of leukotriene C4 in the rat

We studied the systemic and renal hemodynamic effects of leukotriene C4 (2 micrograms/kg per min for 5 minutes, iv) in the rat. During the period of its infusion, leukotriene C4 produced a significant elevation of mean arterial pressure and reductions in cardiac output and renal blood flow, as measured by electromagnetic flow probes. These effects were abolished by FPL55712 , a putative antagonist of sulfidopeptide leukotrienes, but not by saralasin or indomethacin. Leukotriene C4 also resulted in an average loss of 20% in plasma volume which, during the postinfusion period, perpetuated the low cardiac output state and thus provoked the release of angiotensin II. This vasoactive peptide sustained the elevation in systemic vascular resistance and the reduction in renal blood flow over a 70-minute postinfusion observation period. Consequently, glomerular filtration rate fell by approximately 50%. These angiotensin II-mediated effects were abolished by saralasin. Indomethacin prevented the leukotriene C4-induced loss of plasma volume and, thus, allowed for the significant recovery of cardiac output and renal blood flow during the post-infusion period, thereby preserving glomerular filtration rate. We conclude that leukotriene C4 exerts direct systemic and renal vasoconstrictor, as well as cardiodepressant effects, during the period of its infusion. By virtue of its vasopermeability enhancing effect, leukotriene C4 also results in an immediate loss of plasma volume, an effect which requires the presence of secondarily generated cyclooxygenase products and which perpetuates the hemodynamic abnormalities observed beyond the period of leukotriene C4 infusion.

The contractile state as the major determinant in the evolution of left ventricular dysfunction in the spontaneously hypertensive rat

Female spontaneously hypertensive and normotensive rats were studied at 6, 12, 18, and 24 months of age to determine which characteristics of myocardial performance herald the onset of left ventricular dysfunction. Peak ejection fraction index was derived from measurements of peak stroke volume (in vivo volume loading) and passive pressure-volume relations. The myocardial stiffness constant (km, slope of the incremental modulus-stress relation, EINC = km sigma), chamber stiffness constant (kc, slope of the chamber stiffness-pressure relation, dP/dV = kcP), and left ventricular cavitary volume-to-wall volume ratio at 10 mm Hg) were calculated from the pressure-volume data and the contractile state was assessed from the ejection fraction index-afterload relations. In the normotensive rats, the myocardial stiffness constant was not affected by age, whereas, in the spontaneously hypertensive rats, the myocardial stiffness constant remained within normal limits until 18 months, at which time a significant increase in this index of myocardial stiffness occurred. Baseline and maximal cardiac indices and ejection fraction index of spontaneously hypertensive rats were normal from 6 to 18 months, but were markedly reduced at 24 months. This reduction in cardiac performance was associated with a decrease in the left ventricular chamber stiffness constant, i.e., kc. This decreased chamber stiffness, which occurred at a time when myocardial stiffness was increased, was due to a greater increase in cavity size than in myocardial stiffness. The left ventricular cavity-to-wall volume ratio of normotensive rats was not affected by age, whereas, in the spontaneously hypertensive rats, this ratio markedly declined by 18 months. The ejection fraction index-afterload relations i.e., a measure of the contractile state, of the 6- and 12-month-old spontaneously hypertensive rats were similar to those of the normotensive rats of all ages. However, a depression in the contractile state of the spontaneously hypertensive rats occurred at 18 months and was further depressed at 24 months. This abnormality of the contractile state was evident before the deterioration of cardiac performance, as reflected in a decrease in baseline and maximal cardiac indices, and dilation of the left ventricle occurred. The contractile state (ejection fraction index-afterload relation) is thus the most sensitive indicator of left ventricular dysfunction in spontaneously hypertensive rats.

Habitual rumination: a benign disorder

Nine patients who habitually ruminated after meals underwent clinical tests and psychological questioning. Barium meal radiography showed no abnormalities. In one patient oesophageal manometry detected an abnormally large gastric pressure wave 20 minutes after food. Although four patients had family psychiatric histories and three histories of overdose, anorexia nervosa, and mild reactive depression, none had any present serious psychiatric disorder. Behavioural therapy to reduce rumination was successful in one patient. Most patients responded to reassurance that the habit was harmless. Since the condition is a distinct clinical syndrome it may be recognised early with minimal investigations if doctors are aware of its existence.

Blood pressure and left ventricular dysfunction in the spontaneously hypertensive rat

The important role of the heart in the manifestation of systemic hypertension often becomes apparent with the development of left ventricular dysfunction. After a prolonged course of stable compensated left ventricular hypertrophy, spontaneously hypertensive rats (SHR) developed left ventricular dysfunction. A phase of overt left ventricular dysfunction and dilatation was present at an advanced age (24 months) in female SHR, a phase during which systemic hypertension was no longer manifest despite the maintenance of an increased vascular resistance. Similarly, when left ventricular dysfunction was induced after the experimental production of a myocardial infarction, the systemic arterial pressure levels of young SHR fell. This reduction in blood pressure was directly related to the extent of the histologic damage to the left ventricle. These studies underscore the important permissive role of the heart in the expression and maintenance of systemic hypertension.

Cardiorenal hemodynamics and sodium excretion in rats with myocardial infarction

The relation between left ventricular function and renal excretion of sodium (Na+) was studied in rats with myocardial infarction (MI) and varying degrees of left ventricular dysfunction. Three groups of rats were defined: 1) control sustained no infarct, 2) small to moderate infarcts involved 10-40% of the left ventricular circumference, and 3) large infarcts involved greater than 40%. In conscious rats, Na+ excretion was measured after administration of saline load by gavage. Four hours after the load, rats with large MI excreted less than one half the amount of Na+ excreted by control rats, whereas rats with small to moderate MI excreted an intermediate amount. In a second group of anesthetized rats, Na+ excretion, renal hemodynamics, and ventricular performance were determined before and after acute intravenous volume expansion with a balanced salt solution. Rats with small to moderate MI demonstrated minimal impairment in ventricular pumping ability but excreted less Na+ after volume expansion than did control rats. However, rats with large MI demonstrated marked impairment in left ventricular performance and exhibited the least natriuretic response to volume loading. Glomerular filtration rate and renal plasma flow failed to increase with volume expansion in both groups of rats with MI. Thus Na+ excretion in response to acute volume loading was diminished in rats with large MI and markedly impaired cardiac performance but was also reduced in rats with small to moderate MI and minimal changes in ventricular pumping capacity.

Systemic hemodynamic effects of leukotrienes C4 and D4 in the rat

Although local administration of the sulfidopeptide leukotrienes into cutaneous and coronary vascular beds indicates that these naturally occurring metabolites of arachidonic acid are vasoconstrictors, their systemic administration has produced both pressor and depressor responses. The systemic hemodynamic effects of intravenous leukotriene C4 (LTC4) and leukotriene D4 (LTD4) were assessed in ether-anesthetized rats and compared with the effects produced by equimolar doses (2 X 10(-10) to 4 X 10(-8) mol/kg) of norepinephrine and angiotensin. Mean arterial pressure, right atrial pressure, and cardiac output (electromagnetic flowmetry) were recorded during bolus administrations of these vasoactive compounds. LTC4 and LTD4 had similar hemodynamic effects that were characterized by moderate pressure elevations produced by dose-dependent increases in total peripheral resistance, since cardiac output declined. Although the peak mean arterial pressure levels produced by LTC4 and LTD4 (135 +/- 7 and 129 +/- 5 mmHg, respectively) were less than those by norepinephrine (157 +/- 3 mmHg) and angiotensin (174 +/- 5 mmHg), the peak total peripheral resistance values of LTC4 and LTD4 (2.23 +/- 0.32 and 1.86 +/- 0.17 mmHg X ml-1 X min-1, respectively) were between those of the well-known vasopressors, norepinephrine (1.50 +/- 0.09) and angiotensin (2.72 +/- 0.41). The pressor response to LTC4 and LTD4 was less marked than that to norepinephrine and to angiotensin because of the concomitant reduction in cardiac output. These results indicate that LTC4 and LTD4 are systemic vasoconstrictors with potencies similar to those of norepinephrine and angiotensin.

Prevention of the development of heart failure and the regression of cardiac hypertrophy by captopril in the spontaneously hypertensive rat

The spontaneously hypertensive rat (SHR) exhibits both a compensated phase of cardiac hypertrophy in which forward output is maintained despite persistently elevated systemic arterial pressures and a decompensated phase in which cardiac performance has deteriorated in spite of further hypertrophic growth. To determine whether chronic antihypertensive therapy prevents the development of heart failure and the progression of cardiac hypertrophy in SHR with advanced hypertension, captopril (2 g/l of drinking water), a converting enzyme inhibitor, was administered to 14 month old female SHR and normotensive American Wistar rats (NWR) for 10 months. The severe left ventricular hypertrophy of the 24 month old untreated SHR (4.37 +/- 0.2 mg/g v. 2.50 +/- 0.06 mg/g, untreated NWR) was markedly reduced (P less than 0.02) by captopril (3.01 +/- 0.1 mg/g). Chronic therapy prevented the reduction of both baseline and maximal cardiac indices in SHR, but did not alter blood flow in NWR. Left ventricular dilatation was present in 24 month old SHR and, as peak stroke volume index was diminished, the ejection fraction index of the SHR was reduced. Captopril restored this index in SHR to normal. The relation of ejection fraction index and afterload (peak systolic wall stress) was depressed in untreated SHR, but was normal in treated SHR. Thus, chronic therapy with captopril prevented the development of severe cardiac dysfunction and produced a marked regression of cardiac hypertrophy in SHR with advanced hypertensive heart disease.

Effects of hypertension on cardiac performance in rats with myocardial infarction

To determine the effects of hypertension and myocardial infarction on cardiac performance, hemodynamic studies were performed on ether-anesthetized, female spontaneously hypertensive rats and on two strains of normotensive rats, Wistar-Kyoto and American Wistar, 26 days after coronary arterial ligation. Baseline measurements of ventricular and arterial pressures and cardiac output (electromagnetic flowmeter) were obtained. Peak cardiac pumping and pressure-generating capacities were determined during a volume load and aortic occlusion, respectively. Infarct size was determined by planimetry. There was a progressive reduction in mean arterial pressure in relation to infarct size in both hypertensive and normotensive rats, but this reduction was twice as great in spontaneously hypertensive rats as in the normotensive rats, such that the arterial pressure of hypertensive rats with a moderate or large infarction decreased to within the "normotensive range." However, spontaneously hypertensive rats still maintained significantly higher arterial pressures than did normotensive rats at comparable infarct sizes. There was also a progressive reduction in the peak pressure developed during an afterload stress, and this reduction was greater in hypertensive rats than in normotensive rats with a large infarct. Maximal flow-generating capacity was similarly altered in rats with infarction: Peak stroke volume index varied inversely with infarct size and the reduction in this index was significantly greater in spontaneously hypertensive rats than in normotensive rats with a large infarct. Moreover, peak stroke work index was reduced to a greater extent in spontaneously hypertensive rats than in both normotensive strains of rats at any infarct size. Thus, after myocardial infarction, greater reductions in both pressure and flow-generating capacities occurred in hypertensive rats than in normotensive rats.

Regression of left ventricular hypertrophy and prevention of left ventricular dysfunction by captopril in the spontaneously hypertensive rat

To determine whether chronic antihypertensive therapy prevents the progression of cardiac hypertrophy and the deterioration in cardiac performance observed in spontaneously hypertensive rats (SHR) with long-term hypertension, 14-month-old female SHR and normotensive American Wistar rats (NWR) were treated for 10 months with an inhibitor of angiotensin I-converting enzyme, captopril (2 g/liter of drinking water). Captopril reduced the marked left ventricular hypertrophy of 24-month-old SHR (untreated, 4.37 +/- 0.2 mg/g of body weight; treated, 3.01 +/- 0.1 mg/g; P less than 0.02) to levels observed in 6-month-old SHR. Treatment prevented the reductions in baseline and maximal aortic blood flows that occurred in SHR between ages 12 and 24 months yet had no effect on the blood flows of NWR. The diminished maximal stroke volume of untreated SHR was ejected from a significantly increased left ventricular end-diastolic volume, so that the ejection-fraction index was markedly reduced (24-month-old untreated NWR, 84 +/- 3%; untreated SHR, 56 +/- 5%; P less than 0.001). Therapy restores this index in SHR to normal (77 +/- 4%). The relationship between ejection-fraction index, and afterload was also normal in treated SHR. Thus, chronic therapy with captopril produced a marked regression of cardiac hypertrophy and prevented the deterioration of cardiac performance in SHR with long-standing hypertension.

Favorable effects of therapy on cardiac performance in spontaneously hypertensive rats

To determine whether chronic antihypertensive therapy reduces cardiac mass and improves performance in spontaneously hypertensive rats (SHR) with marked left ventricular hypertrophy and evidence of cardiac dysfunction, 12-mo-old male and female SHR and age- and sex-matched normotensive rats (NORM) were treated for 6 mo with either tap water or tap water containing hydralazine or guanethidine. Cardiac performance was assessed by the peak stroke volume and cardiac indices attained during volume loading and by the maximum left ventricular pressure developed during an aortic occlusion. Passive diastolic pressure-volume curves were obtained in the potassium-arrested heart. Treatment prevented the progression of left ventricular hypertrophy in SHR and the marked deterioration in peak pumping ability observed in untreated male SHR and the modest impairment observed in female SHR. The peak developed pressure of both the male and female treated SHR was reduced toward that of NORM and was associated with a reduction in the left ventricular mass-to-volume ratio toward that of NORM. Thus chronic therapy with either hydralazine or guanethidine reduced cardiac mass and prevented the deterioration in cardiac pumping performance observed in SHR with sustained hypertension and marked cardiac hypertrophy.