Doppler velocimetry in fetal rats exposed to enoxaparin and unfractionated heparin (UFH) during pregnancy

Abstract Purpose: To evaluate the effects of enoxaparin and unfractionated heparin (UFH) administered in prophylactic and therapeutic doses on fetal vessels in healthy pregnant Wistar rats, according to Doppler velocimetry measurements. Methods: Fifty animals were assigned to one of five groups: controls (saline), prophylactic and therapeutic enoxaparin (1 and 2 mg/kg/day, respectively), and prophylactic and therapeutic UFH (72 and 400 UI/kg/day, respectively). Uterine horns were examined by ultrasound for identification of live fetuses. A sample of these fetuses underwent Doppler velocimetry. Spectral curves, peak systolic velocity (PSV), pulsatility index (PI), and resistance index (RI) of the middle cerebral artery, ductus venosus, and umbilical artery were investigated. Differences were considered statistically significant when p<0.05. Results: No significant differences in PSV, PI, or RI values were observed among the groups. Conclusion: Doppler velocimetry measurements revealed no significant effects of enoxaparin or unfractionated heparin on fetal vessels in pregnant Wistar rats.

Effects of prostaglandin analogs on blood flow velocity and resistance in the ophthalmic artery of rabbits / Efeitos dos análogos da prostaglandina na velocidade do fluxo sanguíneo e resistência na artéria oftálmica de coelhos

ABSTRACT Purpose: The aim of this study was to investigate the effects of prostaglandin analogs on blood flow in the ophthalmic artery of clinically healthy rabbits. Methods: Fifty-five clinically healthy New Zealand white rabbits were divided into six groups, and the left eyes were treated for four weeks with the preservative benzalkonium chloride (BAK) only or a topical formulation of different prostaglandin analogs (bimatoprost BAK, tafluprost BAK-free, travoprost BAK, travoprost POLYQUAD, and latanoprost BAK). Color Doppler imaging was performed before and after the treatments. The mean values of the peak systolic velocity (PSV) and end diastolic velocity and the resistive index (RI) were calculated. Statistical analysis was performed to compare the differences pre- and post-treatment for each drug and post-treatment among the drugs. Results: The prostaglandin analogs did not affect PSV. Bimatoprost BAK, travoprost POLYQUAD, and latanoprost BAK did not change RI. Tafluprost BAK-free and travoprost BAK therapy resulted in similar reductions in RI. No significant differences pre- and post-treatment were found when BAK was administered alone. Conclusion: The prostaglandin analogs tafluprost BAK-free and travoprost BAK improved blood flow in the ophthalmic artery in healthy New Zealand white rabbits, which suggests that these drugs enhance the prevention of the progression the progression of glaucoma.

RESUMO Objetivo: O objetivo deste estudo foi investigar os efeitos dos análogos da prostaglandina (PGAs) no fluxo sanguíneo da artéria oftálmica em coelhos. Métodos: Cinquenta e cinco coelhos da raça Nova Zelândia clinicamente saudáveis foram divididos em seis grupos para tratamento com formulação tópica de diferentes APGs (bimatoprosta BAK, tafluprosta BAK-free, travoprosta BAK, travoprosta POLYQUAD e latanoprosta BAK) e formulações contendo apenas o conservante cloreto de benzalcônio (BAK). Foi realizada ultrassonografia com Doppler antes e após os tratamentos. Os valores do pico da velocidade sistólica (PSV) e da velocidade diastólica final foram obtidos e o índice de resistência (RI) foi então calculado. A análise estatística foi realizada para comparar as diferenças entre cada droga no pré e pós-tratamento, além das diferenças no pós-tratamento entre as drogas. Resultados: Estes colírios PGAs não afetaram o PSV. A bimatoprosta com o conservante BAK, travoprosta com o conservante POLYQUAD e latanoprosta com o conservante BAK não alteraram o RI. Já o tratamento com tafluprosta sem conservante (BAK-free) e travoprosta com o conservante BAK promoveram redução similar dos valores do RI. Não houve diferença significativa na comparação entre valores pré e pós-tratamento quando BAK foi administrado isoladamente. Conclusão: Os PGAs tafluprosta BAK-free e travoprosta BAK melhoraram o fluxo sanguíneo na artéria oftálmica em coelhos da raça Nova Zelândia sugerindo que estes medicamentos possam contribuir na prevenção da progressão do glaucoma.

Função endotelial vascular em pacientes com fluxo coronário lento e os efeitos do nebivolol / Vascular endothelial function in patients with coronary slow flow and the effects of nebivolol

FUNDAMENTO: A função endotelial braquial tem sido associada ao fluxo lento coronário (FLC). O aumento do fluxo sanguíneo para a artéria braquial faz com que o endotélio libere óxido nítrico (ON), com subsequente vasodilatação. Além de sua atividade com betabloqueador, o nebivolol provoca vasodilatação, aumentando a liberação endotelial de ON. OBJETIVO: Avaliar os efeitos do nebivolol na função endotelial vascular em pacientes com FLC. MÉTODOS: 46 pacientes com FLC e 23 indivíduos com artérias coronárias epicárdicas normais foram examinados com ecocardiografia transtorácica e ultrassonografia da artéria braquial. Os pacientes foram reavaliados dois meses após o tratamento com aspirina ou aspirina e nebivolol. RESULTADOS: Os pacientes com FLC apresentaram maior índice de massa corporal (26,5 ± 3,3 vs. 23,8 ± 2,8, p < 0,001), tempo de relaxamento isovolumétrico (TRIV) de influxo mitral (114,9 ± 18,0 vs. 95,0 ± 22,0 mseg, p < 0,001), menor fração de ejeção do ventrículo esquerdo (FEVE) (63,5 ± 3,1 por cento vs. 65,4 ± 2,2, p = 0,009), colesterol HDL (39,4 ± 8,5 vs. 45,8 ± 7,7 mg/dL, p = 0,003) e dilatação fluxo-mediada da artéria braquial (DFM) (6,1 ± 3,9 por cento vs. 17,6 ± 4,5 por cento, p <0,001). Houve correlações significativas entre a DFM e a presença de FLC (r = 0,800, p < 0,001) e o colesterol HDL (r = 0,349, p = 0,003). Dos pacientes com FLC, apesar de os valores médios de DFM em pré-tratamento terem sido semelhantes (6,1 ± 4,3 por cento vs. 6,0 ± ,6 por cento, p = 0,917), em comparação com a DFM do grupo em pós-tratamento apenas com aspirina, a DFM apresentou valores significativamente maiores do que os pacientes tratados com aspirina e nebivolol (6,0 ± 3,5 por cento vs. 8,0 ± 2,9 por cento, p = 0,047). Constatou-se que o tratamento com nebivolol está associado a um significativo aumento na DFM (6,0 ± 3,6 a 8,0 ± 2,9 por cento, p = 0,030), ao passo que o tratamento apenas com aspirina não apresentou a mesma associação. CONCLUSÃO: A função endotelial pode ser comprometida nas artérias coronárias e braquiais em pacientes com FLC, e o nebivolol pode ser eficaz na melhora da função endotelial em pacientes com FLC.

BACKGROUND: Brachial endothelial function has been associated with coronary slow flow (CSF). Increasing blood flow to brachial artery provokes endothelium to release nitric oxide (NO) with subsequent vasodilatation. Besides its β1-blocker activity, nebivolol causes vasodilatation by increasing endothelial NO release. OBJECTIVE: To assess the effects of nebivolol on vascular endothelial function in patients with CSF. METHODS: Forty-six patients with CSF and 23 individuals with normal epicardial coronary arteries were examined with transthoracic echocardiography and brachial artery ultrasonography. The patients were reevaluated two months after treatment with aspirin or aspirin plus nebivolol. RESULTS: Patients with CSF had higher body mass index (26.5 ± 3.3 vs. 23.8 ± 2.8, p < 0.001), mitral inflow isovolumetric relaxation time (IVRT) (114.9 ± 18.0 vs. 95.0 ± 22.0 msec, p < 0.001) and lower left ventricular ejection fraction (LVEF) (63.5 ± 3.1 percent vs. 65.4 ± 2.2, p = 0.009), HDL-cholesterol (39.4 ± 8.5 vs. 45.8 ± 7.7 mg/dL, p = 0.003) and brachial flow-mediated dilatation (FMD) (6.1 ± 3.9 percent vs. 17.6 ± 4.5 percent, p < 0.001). There were significant correlations between FMD and the presence of CSF (r = 0.800, p < 0.001) and HDL-cholesterol (r = 0.349, p = 0.003). Among Patients with CSF, although pretreatment mean FMD values were similar (6.1 ± 4.3 percent vs. 6.0 ± ,6 percent, p = 0.917) compared to aspirin alone group, posttreatment FMD was significantly higher in patients treated with aspirin plus nebivolol (6.0 ± 3.5 percent vs. 8.0 ± 2.9 percent, p = 0.047). Treatment with nebivolol was associated with a significant increase in FMD (6.0 ± 3.6 to 8.0 ± 2.9 percent, p = 0.030) whereas treatment with aspirin alone was not. CONCLUSION: Endothelial function may be impaired in both coronary and brachial arteries in patients with CSF and nebivolol may be effective in the improvement of endothelial function in patients with CSF.

Drag reduction by polyethylene glycol in the tail arterial bed of normotensive and hypertensive rats

This study was designed to evaluate the effect of drag reducer polymers (DRP) on arteries from normotensive (Wistar) and spontaneously hypertensive rats (SHR). Polyethylene glycol (PEG 4000 at 5000 ppm) was perfused in the tail arterial bed with (E+) and without endothelium (E-) from male, adult Wistar (N = 14) and SHR (N = 13) animals under basal conditions (constant flow at 2.5 mL/min). In these preparations, flow-pressure curves (1.5 to 10 mL/min) were constructed before and 1 h after PEG 4000 perfusion. Afterwards, the tail arterial bed was fixed and the internal diameters of the arteries were then measured by microscopy and drag reduction was assessed based on the values of wall shear stress (WSS) by computational simulation. In Wistar and SHR groups, perfusion of PEG 4000 significantly reduced pulsatile pressure (Wistar/E+: 17.5 ± 2.8; SHR/E+: 16.3 ± 2.7 percent), WSS (Wistar/E+: 36; SHR/E+: 40 percent) and the flow-pressure response. The E- reduced the effects of PEG 4000 on arteries from both groups, suggesting that endothelial damage decreased the effect of PEG 4000 as a DRP. Moreover, the effects of PEG 4000 were more pronounced in the tail arterial bed from SHR compared to Wistar rats. In conclusion, these data demonstrated for the first time that PEG 4000 was more effective in reducing the pressure-flow response as well as WSS in the tail arterial bed of hypertensive than of normotensive rats and these effects were amplified by, but not dependent on, endothelial integrity. Thus, these results show an additional mechanism of action of this polymer besides its mechanical effect through the release and/or bioavailability of endothelial factors.

Atorvastatin improves arterial stiffness in normotensive normolipidaemic persons with type 2 diabetes.

Increased arterial stiffness is an independent predictor of cardiovascular disease and mortality in middle-aged and olderadults. We measured arterial stiffness by pulse wave velocity (PWV)in brachial-ankle segments by automated oscillometry in 71 normotensive and normolipidaemic subjects with type 2 diabetes (40 males and 31 females). 57 patients (whose baPWV was more than 1400 cm/second) were randomised into two groups, group A (n=29) were given 10 mg atorvastatin daily for 6 months and group B (n=28) were given placebo. After 6 months, atorvastatin group had significant improvement in brachial-ankle pulse wave velocity (baPWV) (1712.03 +/- 349.9 cm/second versus 1558.81 +/- 303.26 cm/ second, p< 0.05). Though the placebo group showed some improvement (1692.03 +/- 425.15 cm/second versus 1636.78 +/- 425.1 cm/second) it was not statistically significant. Despite correlation was noted between baPWV and systolic blood pressure (SBP), there was no significant correlation between the mean baPWV and duration of diabetes, body mass index (BMI), waist circumference, waist-hip ratio (WHR), waist to height ratio (WHtR), glycated haemoglobin (HbA1c), LDL, HDL cholesterol and spot urine albumin creatinine ratio (ACR) at the baseline. The decrement of LDL-cholesterol is correlated with the decrement of the baPWV in the atorvastatin group only (p<0.01).

Evaluation of the Effects of Sildenafil Citrate (Viagra) on Vertebral Artery Blood Flow in Patients with Vertebro-Basilar Insufficiency

OBJECTIVE: To investigate the effects of sildenafil citrate (Viagra) on the vertebral artery blood flow of patients with vertebro-basilar insufficiency (VBI) using color duplex sonography (CDS). MATERIALS AND METHODS: The study included 21 patients with VBI (aged 31-76; mean 61.0 +/- 10.5 yrs). We administered a 50 mg oral dose of sildenafil citrate to all patients. Next, we measured the peak systolic velocity (Vmax), end diastolic velocity (Vmin), resistive index (RI), pulsatility index (PI), diameter, area, and flow volume (FV) of vertebral arteries using CDS before the administration of sildenafil citrate; 45 minutes after, and 75 minutes after administration. Statistical testing was performed using SPSS for windows version 11.0. The statistical test used to determine the outcome of the analysis was the repeated measures analysis of variance (ANOVA) test. RESULTS: Compared to the baseline values, the vertebral artery diameter, area, and FV increased significantly following the administration of sildenafil citrate. The diameter, area and FV increased from 3.39 mm at 45 minutes to 3.64 mm at 75 minutes, 9.43 cm2 to 10.80 cm2 at 45 minutes and 10.81 cm2 at 75 minutes, as well as from 0.07 L/min at baseline to 0.09 L/min at 45 minutes and unchanged at 75 minutes, respectively. CONCLUSION: Sildenafil citrate elicited a significant effect on vertebral artery diameter, area and FVs.

Treatment of essential hypertension does not normalize capillary rarefaction

OBJECTIVES: To determine if capillary rarefaction persists when hypertension is treated with angiotensin converting enzyme inhibitor, thiazidic diuretic and/or beta-blocker, and to identify which microcirculatory alterations (structural and functional) persist after anti-hypertensive treatment. METHODS: We evaluated 28 well-controlled essential hypertensive patients and 19 normotensive subjects. Nailfold videocapillaroscopy examination of the fourth finger of the left hand was used to determine the functional capillary densities at baseline, during post-occlusive hyperemia, and after venous congestion. Capillary loop diameters (afferent, apical and efferent) and red blood cell velocity were also quantified. RESULTS: Compared with normotensive subjects, hypertensive patients showed lower mean functional capillary density at baseline (25.1±1.4 vs. 33.9±1.9 cap/mm², p<0.01), during post-occlusive reactive hyperemia (29.3±1.9 vs. 38.2±2.2 cap/mm², p<0.01) and during venous congestion responses (31.4±1.9 vs. 41.1±2.3 cap/mm², p<0.01). Based on the density during venous congestion, the estimated structural capillary deficit was 25.1 percent. Mean capillary diameters were not different at the three local points, but red blood cell velocity at baseline was significantly lower in the hypertensive group (0.98±0.05 vs. 1.17±0.04 mm/s, p<0.05). CONCLUSIONS: Patients treated for essential hypertension showed microvascular rarefaction, regardless of the type of therapy used. In addition, the reduced red blood cell velocity associated with capillary rarefaction might reflect the increased systemic vascular resistance, which is a hallmark of hypertension.

The Hemodynamic Effects of Insulin Following Overdosage with Levobupivacaine or Racemic Bupivacaine in Dogs

Although levobupivacaine (LBUP) is less cardiotoxic than racemic bupivacaine (RBUP), the resuscitation from the LBUP-induced cardiovascular collapse (CVC) has not been easy as expected. Following the recent reports that proposed the resuscitative action of insulin for the RBUP-induced CVC, a controlled trial was performed to assess the feasibility of insulin for the LBUP-induced CVC. Fourteen dogs were randomly allocated into two groups: the RBUP and LBUP groups. Each group received continuous intravenous infusions of RBUP or LBUP until the mean arterial pressure (MAP) reached 40 mmHg. Then, an intravenous bolus of insulin (2 U/kg) was administered. Both groups were successfully resuscitated. At CVC, a decrease of cardiac output and an increase of systemic vascular resistance were observed but to a lesser degree in the LBUP group (p<0.05). After insulin injection, the MAP further declined to under 40 mmHg for several minutes, which was more protracted in the LBUP group (p<0.05). The CVCs induced by LBUP or RBUP in anesthetized dogs could be successfully resuscitated by insulin. Compared with RBUP, however, the less degree of vasoconstriction by LBUP and the innate vasodilatory property of insulin yielded a delayed increment of MAP during the immediate resuscitation period in the LBUP-induced CVC.

Blood flow measurements in rats using four color microspheres during blockade of different vasopressor systems

The use of colored microspheres to adequately evaluate blood flow changes under different circumstances in the same rat has been validated with a maximum of three different colors due to methodological limitations. The aim of the present study was to validate the use of four different colors measuring four repeated blood flow changes in the same rat to assess the role of vasopressor systems in controlling arterial pressure (AP). Red (150,000), white (200,000), yellow (150,000), and blue (200,000) colored microspheres were infused into the left ventricle of 6 male Wistar rats 1) at rest and 2) after vasopressin (aAVP, 10 æg/kg, iv), 3) renin-angiotensin (losartan, 10 mg/kg, iv), and 4) sympathetic system blockade (hexamethonium, 20 mg/kg, iv) to determine blood flow changes. AP was recorded and processed with a data acquisition system (1-kHz sampling frequency). Blood flow changes were quantified by spectrophotometry absorption peaks for colored microsphere components in the tissues evaluated. Administration of aAVP and losartan slightly reduced the AP (-5.7 ± 0.5 and -7.8 ± 1.2 mmHg, respectively), while hexamethonium induced a 52 ± 3 mmHg fall in AP. The aAVP injection increased blood flow in lungs (78 percent), liver (117 percent) and skeletal muscle (>150 percent), while losartan administration enhanced blood flow in heart (126 percent), lungs (100 percent), kidneys (80 percent), and gastrocnemius (75 percent) and soleus (94 percent) muscles. Hexamethonium administration reduced only kidney blood flow (50 percent). In conclusion, four types of colored microspheres can be used to perform four repeated blood flow measurements in the same rat detecting small alterations such as changes in tissues with low blood flow.

Influence of Isoflurane Anesthesia on Pulsatility Index and Peak Systolic Velocity of Basilar Artery in Dogs by Doppler Ultrasonography

This study was performed to examine the influence of isoflurane anesthesia on the pulsatility index (PI) and the peak systolic velocity (PSV) of the blood flow in the basilar artery of dogs by duplex Doppler ultrasonography. Twelve healthy dogs were used to measure the PI and the PSV under the conscious state and isoflurane anesthesia. The pulsatility index (PI) and the peak systolic velocity (PSV) in the basilar artery were measured five times with random intervals. The blood pressure was measured. The PI and PSV values in dogs under isoflurane anesthesia were 1.37 +/- 0.32 and 72 +/- 19 cm/sec, whereas those in the conscious dogs were 1.37 +/- 0.13 and 81 +/- 16 cm/sec, respectively. The indirect mean arterial systolic and diastolic pressures under isoflurane anesthesia were 107 and 51 mmHg, whereas those in the conscious dogs were 133 and 74 mmHg. Though the isoflurane is generally known to induce hypotension, there were no significant differences in the PI and PSV between the isoflurane-anesthetized and the conscious dogs. In conclusion, the isoflurane anesthesia did not influence the PI and PSV in the basilar artery of dogs.

Uterine blood flow response to hormonal replacement therapy in asymptomatic postmenopausal women: a transvaginal Doppler study.

To evaluate the effect of continuous hormonal replacement therapy (HRT) on Doppler parameters of uterine blood flow in asymptomatic postmenopausal women. Thirty-eight asymptomatic postmenopausal women were recruited into the study from the outpatient menopause clinic, Department of Obstetrics and Gynaecology, Faculty of Medicine, Chulalongkorn University. The study population was divided into 20 cases without any HRT (group 1) and 18 cases using continuous conjugated equine estrogen 0.625 mg/day combined with medroxyprogesterone acetate 2.5 mg/day (group 2). The duration of HRT was 21.3 +/- 9.5 (13-56) months. A transvaginal colour flow imaging system (ALOKA SSD-2000 MultiView, Tokyo, Japan) was used to assess uterine blood flow. Quantitative data from areas of colour were evaluated by pulsed Doppler spectrum analysis. Resistance indices (RI) were measured as indicators of uterine perfusion. Both groups were statistically similar with respect to age, parity, age at menopause, height and weight. The endometrial thickness in group 1 and 2 were 3.8 +/- 0.8 and 4.1 +/- 0.6 millimetres, respectively. The left uterine artery RIs of group 1 and 2 were 0.86 +/- 0.08 and 0.84 +/- 0.07, respectively (p = 0.33). The right uterine artery RIs of group 1 and 2 were 0.87 +/- 0.07 and 0.83 +/- 0.06, respectively (p = 0.06). In conclusion, continuous HRT had a non-significant influence on uterine blood flow in the postmenopausal women.

Changes of the carotid artery Doppler flow velocity pattern after sublingual nitroglycerin in patients with hypertension

OBJECTIVE: To evaluate the applicability of carotid Doppler echography for the assessment of changes of peripheral hemodynamics in the hypertensives. SUBJECTS: 28 hypertensives (17 males, 11 females), mean age of 64 yrs and 40 normal controls (24 males, 16 females) mean age of 49 yrs. METHODS: We recorded the right common carotid arterial Doppler flow velocity (BFV) pattern and measured the peak velocities of the percussion wave (P) and late rising tidal wave (T), the ratio of the two (P/T), the time interval between the two peaks corrected by heart rate (P-Tc), systolic flow velocity integral (FVI) and carotid artery diameter (CAD) before and after 0.4 mg dose of subligual nitroglycerin (NTG). RESULTS: 1) In hypertensives, the P wave velocity showed lower and P-Tc interval shorter than those of the normal controls at baseline. 2) After NTG, the P-Tc and P/T increased, but the T and FVI decreased significantly in both groups of subjects. 3) The P/T ratio was less significantly increased after NTG in the hypertensives than in the controls. These results suggest that NTG might have been involved in concomitant reduction and delay of the wave reflection from the peripheral vessels, preferentially in the normal subjects than in hypertensives. CONCLUSIONS: The carotid Doppler echography can be useful for the evaluation of the changes of hemodynamics in the peripheral vessel such as carotid artery in hypertensive subjects.

Is driving oxygen flow rate clinically important for nebulizer therapy in patients with COPD?

Our study suggests that the administration of bronchodilator drug via nebulizer powered by flow rate 6 L/min is more suitable in COPD patients. The oxygen flow rates should not be given more than 6 L/min. In this study, we recruited COPD patients in a stable stage, in whom the risk of hyperoxic induced hypercarbia is less than in the acute exacerbation stage. Thus, in acute exacerbation stage of the COPD patients, the rise of carbondioxide should be higher. We recommend that the COPD patients should receive bronchodilator drug via the nebulizer, especially in acute exacerbation stage, with oxygen flow rate not more than 6 L/min. The medical personnel must closely observe the clinical signs of the patients to prevent the hazard of carbondioxide retention.

Effect of preload and heart rate manipulation on Doppler transmitral flow velocity pattern: search for load--independent parameters.

Pulsed Doppler transmitral flow-velocity provides a non-invasive method for serial evaluation of diastolic function. However confounding influence of loading conditions and heart rate on transmitral flow makes many conclusions suspect. To study the effect of preload, various parameters of Doppler mitral spectrum were studied in 11 patients with stable effort angina, angiographic coronary artery disease and intact global and segmental systolic function, before and after administration of sublingual isosorbide dinitrate (group 1). Following isosorbide dinitrate administration, there was a significant increase in heart rate (p less than 0.001), decrease in left ventricular end-diastolic volume (p less than 0.01), no change in left ventricular ejection fraction and systolic blood pressure. Peak E velocity, E velocity-time integral, E/A velocity time integrals ratio, acceleration and deceleration rates and diastolic filling period were significantly reduced whereas peak A velocity, A velocity time integral, acceleration and deceleration times and atrial filling period were unchanged. In 10 age-matched patients (group 2), atrial pacing performed to achieve similar degree of increase in heart rate as in group 1 (10 +/- 1 vs 12. +/- 4, p = NS), resulted in a decrease in E velocity time integral, E/A velocity time integrals ratio and diastolic filling period (p less than 0.01) without any significant change in any other parameter. Absolute A velocity time integral, acceleration and deceleration times are the only parameters of transmitral diastolic flow-velocity profile which are relatively independent of preload and heart rate provided the change is small.

Effects of catecholamines and acetylcholine on contractile force, chronotropism and coronary flow of the isolated guinea pig heart

Efeitos de catecolaminas e acetilcolina sobre a força contrátil, cronotropismo e fluxo coronariano do coraçäo isolado de cobaia. Estudaram-se os efeitos da adrenalina (AD), noradrenalina (NOR) e acetilcolina (ACh) sobre a força contrátil, freqüência cardíaca e fluxo coronariano, registrados simultaneamente em coraçöes isolados de cobaia, perfundidos com soluçäo de Locke (método de Langendorff). As doses dos mediadores químicos foram calculadas de acordo com os pesos das bases e injetadas na faixa de 4,4 x 10-10 a 1,1 x 10-8 moles. O aumento na força contrátil e freqüência cardíaca, induzido pelas catecolaminas, era dependente da dose, sendo a AD 6,4 vezes mais potente do que a NOR para produzir aumento da força contrátil, enquanto que a NOR era mais potente do que a AD para produzir taquicardia, medida durante o pico do efeito contrátil. A latência entre as injeçöes das catecolaminas e os picos dos efeitos cronotrópicos positivos foi de 43 + ou - 2s, sendo a NOR 3,6 vezes mais potente do que a AD para induzir esse efeito. Durante o pico da taquicardia havia também um aumento na força contrátil, sendo a AD mais potente do que a NOR para induzir esse efeito. O fluxo coronariano foi reduzido durante o pico do efeito das catecolaminas sobre a força contrátil, sendo a NOR mais potente do que a AD em induzir essa reduçäo. Durante o pico da taquicardia produzida pelas catecolaminas, resgistrou-se um discreto aumento no fluxo coronariano. Os efeitos da ACh sobre o coraçäo foram divididos em 4 fases. O eletrocardiograma mostrou bloqueio A-V total durante as fases I, II e III e um retorno abrupto de um ritmo juncional para um ritmo sinusal durante a fase IV. A força contrátil ventricular era semelhante ao controle durante a fase I, diminuía durante a fase II e retornava ao normal durante a fase III. O fluxo coronariano era aumentado discretamente pela ACh durante as fases II, III e IV