[Evaluation after 20 years of a case of Takayasu's disease that presented with aortic regurgitation]. / Evolution après 20 ans d'une maladie de Takayasu Révélée par une insuffisance aortique.

Takayasu's disease is a segmental multifocal affection of medium and large arteries. The diagnosis is based on the association of stenotic and aneurismal lesions of the aorta and its branches secondary to an inflammatory infiltration of the media and adventitia. Cases of aortic regurgitation associated with aneurismal dilatation of the ascending aorta as the presenting features of Takayasu's disease, as in this case, are rare. Histological examination of the aortic wall may help establish the diagnosis by showing signs of aortitis. The other usual arterial lesions are sometimes missing at the initial phase of the disease. A late histological diagnosis may be difficult as the inflammatory lesions tend to be progressively replaced by fibrotic lesions or a banal atheroma.

[Conduction defects as the presenting feature of sarcoidosis or observed during the course of the disease: regression with corticoid steroid therapy]. / Troubles conductifs révélant une sarcoïdose ou apparaissant au cours de son évolution: régression sous corticoïdes.

Cardiac sarcoidosis is often unrecognised because of the absence of specific clinical and electrical signs. The consequences are serious, the main risk being sudden death due to conduction defects (24 to 31% of cases) or ventricular arrhythmias. Any conduction defect without an obvious cause in a young patient should suggest a possible diagnosis of sarcoidosis. The confirmation is histological when giant cell non-caseuting epithelioid granuloma is demonstrated but myocardial biopsies are only positive in 20% of cases. Therefore, biopsy of accessible organs such as salivary glands is recommended. Diagnostic strategy consists in searching for signs of systemic sarcoidosis, and, when the diagnosis has been established, perform a complete work-up with echocardiography, dipyridamole myocardial scintigraphy, cardiac MRI and 24 hour ambulatory ECG recordings (Holter). The only proven treatment is steroid therapy with occasional spectacular observations of reversibility of arrhythmias or conduction defects.

Optimal 3-dimensional method for right and left ventricular fourier phase analysis in electrocardiography-gated blood-pool SPECT.

BACKGROUND: To overcome some of the limitations imposed by planar imaging, we aimed to optimize the use of first harmonic Fourier phase analysis (FPA) in electrocardiography-gated blood-pool single photon emission computed tomography (GBPS) by comparing different quantitative, 3-dimensional methods. METHODS AND RESULTS: Three groups of patients who underwent GBPS were evaluated: group 1, 8 patients with no heart disease; group 2, 10 patients with left ventricular disease; and group 3, 6 patients with right ventricular disease. Six different methods for FPA were compared: surface, cylindrical, spherical, and hybrid methods with fixed thresholding and spherical and hybrid methods with multiple thresholding. The hybrid method with multiple thresholding for the left ventricle and the spherical method for the right ventricle provided the highest discrimination score (phase) between normal and abnormal ventricles. Among methods with similar discrimination score for these 2 methods, the cylindrical and hybrid methods for the left ventricle and the spherical method for the right ventricle provided the best homogeneity of phase distribution histogram in normal ventricles. These were considered the optimal methods for FPA. CONCLUSIONS: The hybrid or cylindrical method for the left ventricle and the spherical method for the right ventricle with fixed thresholding are the optimal methods for FPA in GBPS.

Fourier phase analysis of SPECT equilibrium radionuclide angiography in symptomatic patients with mitral valve prolapse without significant mitral regurgitation: assessment of biventricular functional abnormalities suggesting a cardiomyopathy.

BACKGROUND: Ventricular premature beats are common in patients with mitral valve prolapse (MVP). The purpose of this study was to determine whether symptomatic patients with MVP had certain functional characteristics and if ventricular arrhythmia (VA) could be explained by functional extravalvular abnormalities. Single photon emission computed tomography equilibrium radionuclide angiography with Fourier phase analysis was preferred to the planar radionuclide method. Only patients without significant mitral regurgitation were studied. METHODS AND RESULTS: A total of 23 symptomatic patients with MVP (13 men, 10 women, mean age, 47+/-14 years) without mitral regurgitation underwent single photon emission computed tomography equilibrium radionuclide angiography. Symptoms were present in 20 patients, and VA was present in 14 patients. Ejection fraction, regional wall motion, and Fourier phase analysis were examined in both ventricles and compared with results for normal subjects. Ventricular abnormalities were observed in 20 (87%) patients: decreased left ventricular and right ventricular ejection fractions, increased standard deviations of the mean phase and focal wall motion, and/or delayed phase abnormalities. Abnormalities were less frequent but more marked in the right ventricular free wall, the infundibulum, or the septum compared with left ventricular delayed abnormalities, which were more frequent but limited. In 12 of 14 patients with VA, phase-delayed areas were observed in the ventricle where the origin of ventricular premature beats was suspected on the basis of their electrocardiographic morphologic features. A relation was found between late potentials and delayed-phase areas (right ventricle or septum) and left bundle branch block morphologic features of VA. CONCLUSIONS: Symptomatic patients with MVP frequently have ventricular dysfunction in 1 or both ventricles, sometimes limited but more marked in the presence of severe VA even without significant mitral regurgitation, suggesting structural modification. The use of a sensitive, accurate, and 3-dimensional method such as single photon emission computed tomography equilibrium radionuclide angiography may be of interest for a noninvasive investigation, especially in young symptomatic patients with MVP and VA.

[Pericardial effusion revealing cardiac amyloidosis in the course of rheumatoid arthritis]. / Epanchement péricardique révélateur d'une amylose cardiaque au cours de l'évolution d'une polyarthrite rhumatoïde.

Pericardial effusion is common in patients with rheumatoid arthritis. It is essentially a sign of pericardial involvement of the rheumatoid disease, but viral, bacterial and especially tuberculous pericarditis must not be excluded. Pericardial amyloidosis of the AA type is much less common and difficult to diagnose before cardiac biopsy even in cases of myocardial amyloidosis, as in the reported case, in which the classical association of microvoltage on the ECG and myocardial hypertrophy on echocardiography was absent. The absence of myocardial uptake of technetium-labelled pyrophosphates at myocardial scintigraphy and the absence of a restrictive profile on cardiac gamma-angiography were not suggestive of the diagnosis of amyloidosis. Pericardial and endomyocardial biopsy, justified by the negativity of the preceding investigations, provided an accurate histological diagnosis, a prognostic evaluation and was also useful for guiding management.

[Cardiac abnormalities in a prospective series of 40 patients with type 2 diabetes]. / Anomalies cardiaques d'une série prospective de 40 patients diabétiques de type 2.

Cardiovascular mortality, the principal cause of early death in diabetics, is multifactorial. A prospective study was undertaken to analyse the different factors of excess cardiac complications in 40 patients with type 2 diabetes, whatever the symptomatology, by making an inventory of the cardiac abnormalities (systolic and diastolic left ventricular function, left ventricular hypertrophy, abnormalities of myocardial perfusion, heart rate variability and arrhythmias). Patients underwent 24 hour Holter monitoring, high amplification signal averaged electrocardiography, echocardiography, Thallium scintigraphy with a dipyridamole test followed by coronary angiography when positive. Patients were aged 60 +/- 8 years, diabetics for 11.8 +/- 6.8 years, and had associated cardiovascular risk factors: 85% were obese, 75% were hypertensive, 62.5% had hypercholesterolaemia and 60% were smokers. The HbA1C was 9.2 +/- 19%. An increased left ventricular mass was observed in 34.2% of patients. The left ventricular ejection fraction was normal (59.1 +/- 6.8%); 69.7% of patients had left ventricular diastolic dysfunction. Reduced heart rate variability was observed in 51.8% of cases. Late ventricular potentials were recorded on high amplification signal averaging in 39.5% of patients; 25.6% had significant ventricular extrasystoles and 52.2% had atrial extrasystoles. Twelve patients (45%) underwent Thallium myocardial scintigraphy with a positive dipyridamole test, 8 of whom had coronary lesions on angiography. The excess cardiac complications of diabetes is mainly due to ischaemic heart disease aggravated by autonomic neuropathy, left ventricular diastolic dysfunction, arrhythmias and left ventricular hypertrophy. In future, larger series are required to demonstrate that this detection can guide therapeutic intervention and reduce cardiac morbidity and mortality of diabetics.

[Diagnostic value of stress echocardiography under dobutamine and myocardial scintigraphy for restenosis at 6 months after angioplasty of the left anterior descending artery]. / Valeur diagnostique de l'échocardiographie de stress sous dobutamine et de la scintigraphie myocardique d'effort dans le dépistage de la resténose à 6 mois d'une angioplastie de l'interventriculaire antérieure.

This study compared prospectively the diagnostic value of dobutamine echocardiography and exercise myocardial scintigraphy for restenosis at 6 months after angioplasty of the left anterior descending artery. Forty-one patients aged 58 +/- 10 years, admitted to hospital for myocardium infarction (N = 22) or unstable angina (N = 19), with single vessel disease, were treated by angioplasty of one lesion of the left anterior descending artery after initial evaluation of the left ventricular ejection fraction by echocardiography. At 6 months, left ventricular function was reassessed by echocardiography, dobutamine echocardiography and exercise myocardial scintigraphy (Thallium 201) performed without treatment. Coronary angiography was performed at the same time and showed 8 restenosis (19.5%). Overall, in this series, dobutamine echo and scintigraphy had respectively a sensitivity of 37.5% and 75%, and a specificity of 97% and 70% (p < 0.02). Nine patients had left ventricular dysfunction unchanged compared with the initial measurement without viability in the territory of the left anterior descending artery with low dose dobutamine (group 1); thirty-two patients had improved or normal left ventricular ejection fraction with myocardial viability (group 2). In group 1, no cases of restenosis were detected by dobutamine echocardiography but_of them had myocardial scintigraphic evidence of ischaemia. In group 2, the sensitivity of the two techniques was comparable but dobutamine echo was more specific than scintigraphy (96 versus 75%, p = 0.03). In conclusion, dobutamine echocardiography may be indicated in the diagnosis of restenosis of the left anterior descending artery and in cases of viability in its territory. In its absence, myocardial scintigraphy seems to be preferable.

Comparison of long-term outcome of alcoholic and idiopathic dilated cardiomyopathy.

AIMS: The outcome of alcoholic cardiomyopathy is thought to be better than idiopathic dilated cardiomyopathy if patients abstain from alcohol. The aim of this study was to compare the long-term clinical outcome of alcoholic and idiopathic dilated cardiomyopathy. METHODS AND RESULTS: Of 134 patients with dilated cardiomyopathy and normal coronary angiography, 50 had alcoholic cardiomyopathy; they were compared serially to 84 patients with idiopathic dilated cardiomyopathy. Left ventricular end-diastolic diameter, left ventricular ejection fraction and cardiac index, severity of ventricular arrhythmias, measurement of heart rate variability and results of signal-averaged ECG were similar in both groups. Although alcohol withdrawal was strongly recommended but observed in only 70% of patients with alcoholic cardiomyopathy, both groups had similar outcome in terms of cardiac death after follow-up treatment of 47+/-40 months. Multivariate analysis in the entire cohort demonstrated that increased pulmonary capillary wedge pressure (P=0. 003), alcoholism and lack of abstinence during follow-up (P=0.006) and decreased standard deviation of all normal-to-normal RR intervals (P=0.02) were independent predictors of cardiac death. CONCLUSION: In contrast with previous studies, patients with alcoholic cardiomyopathy did not have a better outcome than patients with idiopathic dilated cardiomyopathy. Alcoholism without abstinence was a strong predictor of cardiac death. This suggests that a more aggressive approach to alcohol cessation is needed in these patients.

[Comparative study of post-infarction myocardial viability after fibrinolysis by stress tomoscintigraphy and echography: can viability be detected without ischemia?]. / Etude comparée de la viabilité du myocarde en post-infarctus après fibrinolyse par tomoscintigraphie et échographie de stress: peut-on détecter la viabilité sans l'ischémie?

The objectives of this prospective study was to define the comparative ability of stress myocardial scintigraphy and dobutamine stress echocardiography to demonstrate post-MI myocardial viability, assessed on the functional recovery in terms of improvement of global and segmental kinetics by cardiac gamma-angiography after revascularization. 18 patients (11 anterior MI, 7 lateral or inferior MI) and 162 segments were analysed semiquantitatively. All patients with persistent significant stenosis underwent secondary revascularization of the artery responsible for myocardial infarction. The prevalence of viability was high, as only 34% of segments initially presented a segmental kinetic abnormality and contraction was improved at 6 months in 54% of cases. Stress scintigraphy and dobutamine echocardiography detected viability with a sensitivity of 96% and 70%, a specificity of 88% and 82%, a positive predictive value of 89% and 77% and a negative predictive value of 95% and 76%, respectively. Only the wall score index with low-dose dobutamine was correlated with the ejection fraction at 6 months. Stress echocardiography is a more reliable predictor of the degree of functional recovery after revascularization. Scintigraphy visualizes much more extensive abnormalities than echocardiography. This often corresponds to ischaemic territories with normal contraction under baseline conditions and low doses of dobutamine. It therefore seems preferable both examinations for optimal assessment of thrombolized patients following myocardial infarction.

Diagnosis of arrhythmogenic right ventricular cardiomyopathy by fourier analysis of gated blood pool single-photon emission tomography.

To evaluate the diagnostic performance of Fourier phase analysis of gated blood pool single-photon emission computed tomography (GBP SPECT) in arrhythmogenic right ventricular (RV) cardiomyopathy, 18 patients with confirmed arrhythmogenic RV cardiomyopathy underwent GBP SPECT and x-ray cineangiography. Results were compared with data obtained with GBP SPECT in 10 control subjects. This 3-dimensional method demonstrated good correlation with cineangiography for measurements of RV enlargement and extent of the disease; RV and left ventricular segments were analyzed with the same accuracy. Tomographic abnormalities were significant decreased RV ejection fraction, RV dilatation, nonsynchronized contraction of the ventricles, increased RV contraction dispersion, presence of segmental RV wall motion disorders and/or phase delays, and occasionally regional left ventricular abnormalities. RV-delayed phase areas were always present in our population. A scoring system with RV criteria was proposed to diagnose RV disease. Because Fourier analysis of GBP SPECT provides ventricular morphologic information for the right ventricle with the same accuracy as for the left ventricle, it may replace planar radionuclide studies. Therefore, this method is helpful in patients with a strong clinical suspicion of arrhythmogenic RV cardiomyopathy, and should be used as a screening method before right ventriculography.

[Comparative efficacy and risks of low molecular weight heparins and thrombolysis in massive pulmonary embolism without cardiogenic shock]. / Efficacité et risques comparés des héparines de bas poids moléculaire et de la thrombolyse dans l'embolie pulmonaire massive sans état de choc. A propos de 62 patients.

The aim of this retrospective study was to assess pulmonary reperfusion by scintigraphy, the risks of recurrent embolism and of bleeding complications at the 7th day and 3rd month in 2 groups of patients admitted to hospital for massive pulmonary embolism without cardiogenic shock treated by intravenous thrombolysis (Group I) and by subcutaneous low molecular weight heparin (Group II) paired by Miller's index. The basal characteristics of the two groups, each comprising 31 patients, were comparable with respect to the severity of the pulmonary embolism with an average global scintigraphic defect of 40.6 +/- 13.5% in Group I and 39 +/- 13.7% in Group II. The scintigraphic changes at the 7th day were comparable with a relative improvement of 55 and 51% respectively and at 3 months of 74% in both groups. There was no significant difference in terms of recurrence of embolism (3 versus 0% at the 7th day and 3% in each group at 3 months) or of bleeding complications (13 and 10% at the 7th day and 10 and 6% at 3 months respectively). Low molecular weight heparin seems to be as effective as intravenous thrombolysis for the treatment of massive pulmonary embolism without shock. This result requires confirmation by a large scale prospective randomised trial.

[Value of tomoscintigraphy with Fourier analysis in the diagnosis of arrhythmogenic right ventricular cardiomyopathy]. / Intérêt de la tomoscintigraphie cavitaire avec analyse de Fourier dans le diagnostic de cardiomyopathie arythmogène du ventricule droit.

ECG gated blood pool tomography has been performed in sixteen patients with right ventricular arrhythmias in whom the diagnosis of arrhythmogenic right ventricular cardiomyopathy was made based on the finding of abnormalities on contrast angiography. They were compared both to control subjects and to patients with primary dilated cardiomyopathy. Thick slices of ventricles were obtained throughout the cardiac cycle in three orthogonal planes: horizontal long axis and short axis thick slices for analysis of right and left ventricular regional wall motion abnormalities and analysis of the spread of the contraction by means of Fourier phase imaging, vertical long axis slices (one for each ventricle) for ejection fractions, because of easy and reproducible determination of valvular planes and analysis of all right ventricular segments, especially the pulmonary infundibulum. Five typical right ventricular abnormalities were seen: decreased ejection fraction (32 +/- 15% vs 55 +/- 3% in control; p < 0.001), increased diameter (ratio of right to left diameters = 1.2 +/- 0.3 vs 0.9 +/- 0.1; p < 0.01), global delayed contraction versus that of the left ventricle (22 +/- 20 degrees vs -2 +/- 6%; p < 0.01), increased dispersion of contraction (32 +/- 16 degrees vs 13 +/- 4 degrees; p < 0.01) and presence of segments with decreased and/or delayed contraction. Right ventricular disease was observed in all the patients: localized form (56%), diffused form (44%). This method provides accurate functional data for diagnosis and follow-up of patients. In future, this wall motion evaluation method may replace planar nuclear angiography as myocardial SPECT have replaced myocardial planar scintigraphy.

[A study of 36 cases of mitral valve prolapse by isotopic ventricular tomography]. / Etude par tomographie cavitaire isotopique de 36 cas de prolapsus valvulaire mitral.

Left and right ventricular wall motion was studied in mitral valve prolapse with or without ventricular arrhythmias. Regional and global ventricular wall motion was evaluated by isotopic methods, based in ejection fraction and Fourier phase analysis representing the progression of wall contraction. The synchronisation of the ventricles was characterized by the difference of the mean phase of each ventricle. The heterogeneity of contraction of each ventricle was defined by the dispersion around the mean (standard deviations of the phases). Fifteen of the 36 patients had complex ventricular arrhythmias (Lown grade > or = III). 12 had LVP and 16 had mitral regurgitation. In mitral valve prolapse, the RV EF was decreased compared with normal controls (30 +/- 9% vs 40 +/- 10% ; p < 0.001), especially in patients with mitral regurgitation (26 +/- 7% vs 30 +/- 10%; p = NS) and complex ventricular arrhythmias (26 +/- 7% vs 32 +/- 10%; p < 0.01). The SDP of the LV was greater than those of controls (18 +/- 11 degrees vs 11 +/- 5 degrees ; p = NS) whereas the SDP of the RV was greater (27 +/- 17 degrees vs 12 +/- 5 degrees ; p < 0.05) especially in those with complex ventricular arrhythmias (36 +/- 21 degrees vs 21 +/- 10 degrees : p < 0.01). The SDP of LV and RV were greater in patients with mitral regurgitation: 20 +/- 11 degrees versus 17 +/- 10 degrees (NS) and 35 +/- 21 degrees versus 20 +/- 8 degrees (p < 0.01). Heterogenous ventricular contraction, more marked in the right ventricle in mitral valve prolapse suggests severe myocardial disruption in this valvular disease, reflected by the high incidence of LVP and complex ventricular arrhythmias.

[Idiopathic monomorphic ventricular tachycardia]. / Tachycardies ventriculaires idiopathiques monomorphes.

Idiopathic monomorphic ventricular tachycardia (IVT) represents 10% of all cases of VT and is usually observed in young subjects. The origin of the VT may be right ventricular, especially in the infundibulum, giving rise to runs of VT with inter-critical ventricular extrasystoles of the same morphology, or to paroxysmal sustained exercise-induced VT; they usually show left bundle branch block with right axis deviation: the triggering mechanism is probably a parasystole incompletely protected from the sinus rhythm (for the runs of VT) whereas the mechanism of maintenance is probably that of triggered repetitive activity (for the runs and paroxysmal forms of VT). When the origin is in the left ventricle, the VT shows right bundle branch block and left axis deviation and is typically paroxysmal and sustained, triggered by coupled atrial stimulation and followed by a post-tachycardial syndrome; these forms are probably due to reentry into or near to the left posterior hemibranch. These forms of IVT are unique by: 1) their triggering by acceleration of the heart rate, especially during the day, on effort or during an emotion; 2) the usual absence of late ventricular potentials on surface recordings; 3) their capricious outcome, usually good with 92% survival at 10 years; 4) their response to drugs (verapamil, betablockers and/or adenosine) which are relatively ineffective against other forms of VT; 5) their tendency to recur often leading to radiofrequency ablation procedures (80% success rate). The exclusion of underlying inapparent cardiac disease (especially arrhythmogenic right ventricular dysplasia) is an essential part of diagnosis.

[Isotopic study of myocardial perfusion and innervation in 28 patients with primary hypertrophic cardiomyopathy: relation to ventricular arrhythmia]. / Etude isotopique de la perfusion et de l'innervation myocardique chez 28 patients atteints de cardiomyopathie hypertrophique primitive: relation avec les troubles du rythme ventriculaire.

Ventricular arrhythmias are frequent, sometimes complex and severe, in primary hypertrophic cardiomyopathy. They carry a poor prognosis. Some workers have reported that these arrhythmias are more common in patients with abnormal myocardial perfusion. Other groups have underlined the important role of the sympathetic nervous system in the development of ventricular hypertrophy and the genesis of ventricular arrhythmias. Therefore, a population of 28 patients with primary hypertrophic cardiomyopathy (PHCM) were studied by thallium 201 myocardial scintigraphy and sympathetic innervation was assessed using a structural analogue of noradrenaline, meta-iodobenzyl-guanidine (MIBG). Then, perfusion and innervation were correlated with ventricular arrhythmias observed on 24 hours holter monitoring electrocardiogram. Perfusion abnormalities were observed in 60% of patients: stable in mild left ventricular hypertrophy, labile in severe left ventricular hypertrophy. They were not related to the presence of muscular bridges and systolic compression of septal arteries demonstrated by coronary angiography. These perfusion abnormalities were closely correlated to ventricular extrasystoles observed on Holter monitoring. In this series, and compared to controls, the fixation of MIBG as determined by the Heart/Mediastinum (H/M) ratio was significantly decreased (2.27 +/- 0.31 versus 2.57 +/- 0.33 in controls). Uniform myocardial uptake of MIBG with no defect or significant global hypofixation was observed in 32% of PHCM. Regional and occasionally global hypofixation was observed in 68% of patients. In moderate hypertrophy, reduced uptake was not uniform, the lateral wall and apex being the most abnormal. Uptake of MIBG was significantly correlated to septal wall thickness and to left ventricular mass index. These defects were related to abnormal neuronal uptake of MIBG.(ABSTRACT TRUNCATED AT 250 WORDS)

[Significance of isotopes in the study of pre-excitation and ventricular tachycardia]. / Intérêt des isotopes dans l'étude des préexcitations et des tachycardies ventriculaires.

In normal patients, Mac Carthy has demonstrated that there was a very close correlation between the ventricular contractile activity, evaluated by Fourier's isotopic phase analysis, and electrical depolarization, evaluated by endocardial mapping. It has therefore been possible to study asynchronisms or asymmetries of the ventricular contraction-depolarization and particularly the syndromes of ventricular pre-excitation and ventricular tachycardias. In Wolff-Parkinson-White syndromes (WPW), the mapping obtained by heart cavity tomography in addition to dual-plane gamma-angiography, provides most useful informations, due to additional section planes permitting tridimensional location of the earliest site of ventricular activation. It is quite useful to locate the bundle of Kent always difficult on surface electrocardiogram, or when the endocardial exploration does not permit to precisely locate the site of the excentric atrial activation in case of multiple bundles of Kent or without retrograde conduction. When the left bundle of Kent is barely identified, the isotopic image may be improved by oesophageal stimulation. Additional parameters (use of several harmonics, factorial analysis) will permit to improve the localization of accessory pathways, to be destroyed by fulguration or surgery. In case of ventricular tachycardias with limited functional tolerance, only gamma-angiography, lasting only 3 to 5 minutes, may be used. Combined with endocardial tomography or even gamma-angiography performed in sinus rhythm, not only the site of origin of the ventricular ectopy may be localized, but it also can be correlated with ventricular kinetics abnormalities and the cardiopathy in question may be identified. Most authors consider that there is a close relationship between isotopic site, electrocardiographic appearance and the site found by endocardial mapping or "pace-mapping". In patients with ventricular tachycardias of different morphologies, isotopic mapping permits to differentiate those originating from a same lesion (which may be treated by surgery of fulguration) from those originating in remote areas. Therefore, this technique is a non aggressive and rapid method providing accurate informations on severe rhythm disorders currently treated by eradication of their anatomical substratum.

Naloxone effects on blood pressure, analgesia and diuresis in spontaneous hypertensive and normotensive rats.

Studies were performed in unanesthetized normotensive and spontaneously hypertensive rats (SHR) to compare the effects of naloxone. In normotensive Wistar rats, naloxone did not change blood pressure (BP) and nociceptive threshold, but it induced a dose-related diuretic response. Whereas in SHR naloxone decreased nociceptive threshold and lowered BP when given intracerebroventricularly, it failed to significantly modify diuresis. These differences between hypertensive and normotensive rats in their responses to naloxone may be explained by the fact that vasopressin (VP) levels and opioid activity are different in SHR.