Isosorbide dinitrate in experimental portal hypertension: a study of factors that modulate the hemodynamic response

Isosorbide dinitrate, a long-acting vasodilator, has been tested in human portal hypertension with conflicting results. In order to determine some of the factors that could affect the individual response to this drug, we infused isosorbide dinitrate at a low dose (10 to 25 micrograms per kg per min) and a high dose (100 micrograms per kg per min) to rats with portal vein stenosis. Under pentobarbital anesthesia, portal pressure was measured with an ileocolic vein catheter while cardiac output and regional blood flows were measured with the microsphere technique. At a dose that decreased arterial pressure by approximately 10%, cardiac output remained unchanged while portal vein inflow decreased significantly; portal pressure was not reduced (10.7 +/- 0.2 vs. 10.0 +/- 0.3 mm Hg), indicating a rise in portal vascular resistance. At a high dose of isosorbide dinitrate, arterial pressure and cardiac output fell markedly; portal pressure decreased only modestly (11.3 +/- 0.3 vs. 9.8 +/- 0.6 mm Hg, p less than 0.05), but portal flow was unchanged, indicating a reduction in portal vascular resistance. In addition, portal hypertensive rats received a constant i.v. infusion of N-acetyl-cysteine; the combination of the latter and isosorbide dinitrate markedly potentiated the effects on arterial pressure. Thus, the dose of the drug and the presence of cysteine-containing compounds appear to modulate the hemodynamic response to isosorbide dinitrate. Clinical testing with this drug should be undertaken with consideration of these factors.     

Effect of sublingual isosorbide dinitrate in portal hypertension

Nitrates decrease portal pressure by decreasing portal venous inflow and resistance. We studied over 20 minutes the effect of 10 mg isosorbide dinitrate sublingual on intrasplenic pulp pressure, mean arterial pressure and heart rate, in 13 patients with cirrhotic or non-cirrhotic portal hypertension. The pulp pressure fell progressively over 20 minutes, from mean 43.6 +/- 2.4 (SEM) to 35.6 +/- 1.8 cm H2O (p less than 0.001). This was accompanied initially by a significant fall in mean arterial pressure (85.8 +/- 1.9 to 80.4 +/- 2.7 mmHg at 4 minutes; p less than 0.01) and rise in heart rate (92.5 +/- 5.0 to 102.6 +/- 5.9 per minute at 6 minutes; p less than 0.02), following which these parameters remained stable. One patient developed giddiness due to hypotension at 15 minutes. We conclude that sublingual isosorbide dinitrate decreases pulp pressure in cirrhotic and non-cirrhotic portal hypertensives, but this is initially accompanied by significant hemodynamic changes.     

Central and regional hemodynamic effects of intravenous isosorbide dinitrate, nitroglycerin and nitroprusside in patients with congestive heart failure

A triple crossover random design was used to compare the central and regional hemodynamic effects of intravenous isosorbide dinitrate, nitroglycerin and nitroprusside in 10 patients with low output congestive heart failure. Isosorbide dinitrate and nitroglycerin were infused in dose increments of 0.8 μg/kg body weight per min up to 4.0 μg/kg per min and nitroprusside in increments of 0.4 μg/kg per min up to 2.0 μg/kg per min. The central and regional hemodynamic responses of isosorbide dinitrate and nitroglycerin were similar;both effected a 10 to 35 percent reduction in pulmonary capillary wedge pressure, systemic blood pressure and vascular resistance and pulmonary arterial pressure and resistance with a 7 to 22 percent increase in stroke volume and cardiac output. Nitroprusside elicited a similar decrease in pulmonary capillary wedge pressure with a greater reduction (15 to 45 percent) in systemic blood pressure and resistance and pulmonary arterial pressure and resistance and greater augmentation of stroke volume and cardiac output (20 to 40 percent). Arterial oxygen saturation remained unchanged with isosorbide dinitrate and nitroglycerin and decreased slightly with nitroprusside. None of the drugs altered total body oxygen consumption. All three drugs decreased limb vascular resistance and elevated limb blood flow proportional to the degree of change in systemic vascular resistance and cardiac output. Isosorbide dinitrate and nitroglycerin did not alter renal vascular resistance, so that a mild reduction in renal blood flow was noted as systemic blood pressure decreased. Nitroprusside decreased renal vascular resistance; however, the concomitant decrease in arterial pressure resulted in no net change in renal blood flow. None of the three drugs altered hepatic blood flow or vascular resistance.

In low output congestive heart failure, these three drugs effect similar responses in preload, nitroprusside causing a greater change in afterload. Preferential vasodilation of regional vascular beds was noted with limb flow greater than hepatic and renal flow with isosorbide dinitrate and nitroglycerin and limb flow much greater than renal and greater than hepatic flow with nitroprusside.     

Reduction of Portal Pressure by Chronic Administration of Isosorbide Dinitrate in Patients with Cirrhosis: Effects on Systemic and Splanchnic Hemodynamics and Liver Function

We investigated the chronic effects of isosorbide dinitrate on systemic and splanchnic hemodynamics and liver function in 13 patients with liver cirrhosis and portal hypertension. Placebo administration for 4 wk (n = 4) had no significant effects on these parameters. In contrast, oral administration of 40 mg/day of isosorbide dinitrate for 4 wk (n = 9) caused a significant fall in portal pressure (-18%, p less than 0.02), as evaluated by measurements of the hepatic venous pressure gradient with no modification in hepatic blood flow (from 0.72 +/- 0.29 to 0.71 +/- 0.34 L/min, NS), suggesting decreased intrahepatic or collateral vascular resistance. On the other hand, there was no significant correlation between the changes in mean arterial pressure and hepatic venous pressure gradient (r = 0.42). Thus, it seems unlikely that a reduction in portal blood inflow by baroreceptor-mediated reflex splanchnic vasoconstriction contributed to the fall in portal pressure. In addition, this drug had no adverse effects on liver function, as evaluated by measurements of the intrinsic clearance. These results suggest that chronic administration of isosorbide dinitrate could be a potentially useful and associated with cirrhosis.     

Hemodynamic effects of combined treatment with somatostatin analogue (SMS 201-995) and low-dose isosorbide dinitrate on portal hypertension in conscious cirrhotic rats

The authors investigated whether combined treatment with the somatostatin analogue, SMS 201-995, and low-dose isosorbide dinitrate enhanced the hemodynamic effects of the individual agents on rats with thioacetamide-induced cirrhosis. Four groups of cirrhotic rats received SMS 201-995 (0.1 μg·min^?1·kg^?1), isosorbide dinitrate (10 μ·min^?1·kg^?1), both agents, or placebo, respectively. Hemodynamics were measured serially in conscious rats, using a radioactive microsphere method. SMS 201-995 reduced portal venous inflow 21±4% and portal pressure 17±3%. Isosorbide dinitrate decreased portal venous inflow 20±4%, by inducing splanchnic vasoconstriction mediated by low pressure baroreflexes, and this agent also decreased portal pressure, by 14±2%. Portal venous resistance rose 7.6±3% with isosorbide dinitrate alone, but decreased 18±4% with combination therapy. This effect may have been induced by the pronounced vasodilatory effect of isosorbide dinitrate on the venous vasculature, since the reflex splanchnic vasoconstriction that occurs with low-dose isosorbide dinitrate disappears when this agent is combined with SMS 201-995. The decrease in portal pressure was more marked (22±4%) and changes in systemic hemodynamics were milder with the combined treatment. It was concluded that combination therapy with SMS 201-995 and low-dose isosorbide dinitrate may be beneficial for portal hypertension in liver cirrhosis.     

Hemodynamic effects of high-dose sustained-action oral isosorbide dinitrate in stable angina

Hemodynamic effects of sustained-action oral isosorbide dinitrate (40 or 80 mg) were studied in 10 patients with stable angina for a period of 16 hours. Control hemodynamic parameters monitored for eight hours prior to the administration of isosorbide dinitrate showed no significant change. However significant reduction in mean arterial pressure, cardiac index, pulmonary artery wedge pressure, mean pulmonary artery pressure, double product (systolic pressure multiplied by heart rate), stroke volume index, and stroke work index occurred in the first two hours and persisted for 12 hours following the administration of isosorbide dinitrate. Heart rate did not change significantly for 12 hours. It can be concluded that the hemodynamic effects of sustained-action oral isosorbide dinitrate occur in the first two hours and last up to 12 hours. The predominant hemodynamic effect appears to be on the myocardial preload. The antianginal effect of the drug could be attributed to the reduction of myocardial oxygen demand reflected by a decrease in the double product and stroke work. The duration of the hemodynamic changes observed in this study indicates that high-dose oral isosorbide dinitrate could be administered conveniently two or three times daily.     

Comparison between isosorbide dinitrate in aerosol and in tablet form for the treatment of hypertensive emergencies in the elderly

BACKGROUND: Isosorbide dinitrate in spray form is an effective and safe option for the treatment of hypertensive emergencies. The aim of this study was to evaluate whether isosorbide dinitrate spray is as effective and safe as treatment in tablet form for the management of hypertensive emergencies in the elderly. METHODS: Forty patients with hypertensive emergencies were randomly divided into two groups of 20 patients each. Group A received 1.25 mg isosorbide dinitrate aerosol upon arrival and a second dose 15 min later when mean systemic arterial pressure (MAP) reduction was <15% . Group B patients received a single 5 mg tablet of sublingual isosorbide dinitrate. RESULTS: Blood pressure in Group A patients decreased from 193 +/- 13/123 +/- 6.6 mmHg to 154 +/- 15/92.5 +/- 7.6 mmHg (p < 0.005), the reduction beginning 10 min after drug administration; no adverse effects were found. Two patients in Group B did not respond but for the other patients in this group blood pressure decreased from 197 +/- 10/121 +/- 7 to 154 +/- 11/90 +/- 4 mmHg, (p < 0.005), the reduction beginning 45 min after receiving the medication; 8 patients suffered headache. CONCLUSION: Our results indicate that isosorbide dinitrate aerosol is more effective than tablets for the treatment of elderly patients with hypertensive emergencies.     

Effects of isosorbide dinitrate on portal hypertension in alcoholic cirrhosis

It has recently been reported that vasodilators lower portal pressure in patients with cirrhosis. This effect, however, is not definitively proven. The effect of isosorbide dinitrate (5 mg sublingually) on splanchnic and systemic hemodynamics was investigated in 13 patients with alcoholic cirrhosis and portal hypertension. The administration of isosorbide dinitrate reduced hepatic venous pressure gradient by 34% (P less than 0.001), mean arterial pressure by 30% (P less than 0.001), cardiac index by 17% (P less than 0.001) and systemic vascular resistance by 11% (P = 0.05). Hepatic blood flow was not affected by the treatment. Significant correlations were found between the decrease in hepatic venous pressure gradient and that of cardiac index (P less than 0.05) and mean arterial pressure (P less than 0.05). These data indicate that isosorbide dinitrate lowers portal pressure in patients with cirrhosis. Decrease in cardiac output, rise in splanchnic arterial vascular resistance and decrease in porto-hepatic resistance seem to participate in determining the effect.     

Orally administered isosorbide dinitrate in patients with and without left ventricular failure due to acute myocardial infarction.

The oral effectiveness of 10 mg followed by 20 mg of isosorbide dinitrate in 21 patients with acute mycardial infarction was studied over a period of 13 hours. The patients were grouped according to initial left ventricular filling pressure: group I, pressure less than 20 mm Hg, and group II, pressure more than 20 mm Hg. Patients in group II had left ventricular failure. In both groups isosorbide dinitrate resulted in a significant decrease in pulmonary arterial pressure. The left ventricular filling pressure decreased in group I from 13.6 +/- 4.0 to 7.1 +/- 2.6 mm Hg (mean +/- 1 standard deviation) and in group II from 26.9 +/- 4.6 to 19.0 +/- 3.6 mm Hg (P less than 0.001). Cardiac output decreased in group I from 5.1 +/- 1.0 to 4.5 +/- 0.9 liters/min, whereas in group II it increased significantly from 3.5 +/- 0.8 to 4.1 to 0.9 liters/min (P less than 0.001). In both groups, peripheral arterial blood pressure decreased (P less than 0.60). Heart rate remained constant. Whether cardiac output increased or decreased was found to be dependent on the initial left ventricular filling pressure. In patients with an initially high value (above 20 mm Hg), the increase in cardiac output is probably due to the reduction of afterload. An additional factor may be the decrease in left ventricular filling pressure, which leads to an improved blood supply in the affected mural segments as a result of the decrease in the extravascular component of the coronary resistance. Significant changes in cardiac output and left ventricular filling pressure were achieved 3 to 5 hours after oral administration of isosorbide dinitrate. Clinical signs of failure were less pronounced. Isosorbide dinitrate is, therefore, a therapeutic agent in the treatment of left ventricular failure due to acute myocardial infarction.     

Usefulness of intracoronary isosorbide dinitrate in alleviating myocardial ischaemia during coronary balloon angioplasty.

The effect of intracoronary isosorbide dinitrate on provoked myocardial ischaemia during percutaneous transluminal coronary angioplasty (PTCA) was studied in 60 patients who had at least 1 mm electrocardiographic (ECG) ST segment deviation during a 70 s control balloon inflation period. Isosorbide dinitrate (dose 1 mg, 2 mg or 3 mg) or placebo (saline) was administered by slow intracoronary injection, and the ST segment changes recorded again during an identical dilatation period 2-4 min later. Following injection of isosorbide dinitrate, the severity of ST segment deviation decreased (1 mg -31 +/- 30%, P = 0.03; 2 mg -51 +/- 35%, P = 0.0001; 3 mg -36 +/- 32%, P = 0.002) during coronary balloon inflation, and the time until onset of 1 mm ST deviation was prolonged (1 mg +79 +/- 137%, P = 0.06; 2 mg +85 +/- 87%, P = 0.02; 3 mg +78 +/- 109%, P = 0.02). With the 3 mg dose, the time to maximum ECG change increased (+37 +/- 87%, P = 0.02). In the placebo group, there was a small decrease in the severity of ST segment deviation in patients receiving placebo (-23 +/- 32%, P = 0.03), but no change in the time to its onset or in the time to maximum ST deviation. Isosorbide dinitrate did not alter heart rate, systolic arterial pressure or the rate-pressure product at maximum ST segment change, implying that when isosorbide was administered by direct intracoronary injection, a direct cardiac effect was responsible for the major anti-ischaemic effect of the drug.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects on the systemic and coronary circulation of 2 nitrate derivatives, intravenous trinitrin and sublingual isosorbide dinitrate, administered during atrial pacing]

The changes in the systemic and coronary circulations produced by intravenous trinitrin 0.38 +/- 0.125 mg/hour and sublingual isosorbide dinitrate 5 mg were studied in 24 patients with coronary artery disease. When given during rapid atrial pacing both drugs decreased pulmonary capillary pressures (p less than 0.001), cardiac and coronary output (p less than 0.001 and p less than 0.01) and myocardial oxygen consumption (p less than 0.01). At these dosages, intravenous trinitrin has no significant effect on average systemic blood pressure or left ventricular work index; the coronary arterial resistances increased (p less than 0.005). Isosorbide dinitrate significantly decreased average systemic blood pressure and the left ventricular work index (p less than 0.001); there was no significant difference in the coronary arterial resistances; the decrease in coronary blood flow observed after sublingual isosorbide dinitrate seems partly due to a decreased perfusion pressure. The beneficial effect of these nitrite derivatives seems to be mainly related to a reduced preload.     

Reduction of portal pressure by isosorbide-5-mononitrate in patients with cirrhosis. Effects on splanchnic and systemic hemodynamics and liver function

The results of a study to characterize the effects of the oral administration of isosorbide-5-mononitrate (Is-5-Mn), the active metabolite of isosorbide dinitrate, on portal hypertension in 23 patients with cirrhosis are reported. Patients received 20 mg of Is-5-Mn (n = 10), 40 mg (n = 9), or a placebo (n = 4). No significant changes were observed after the administration of the placebo. However, both doses of Is-5-Mn significantly reduced portal pressure, as evaluated by measurements of the hepatic venous pressure gradient. The fall in portal pressure averaged 10% after the 20-mg dose and 18% after 40 mg and was maintained for the 2 h of observation. Reduction of portal pressure was due to a decrease in the wedged hepatic vein pressure, with no changes in the free hepatic venous pressure. After the 20-mg dose, the decrease in portal pressure was associated with an increase in hepatic blood flow (16%), suggesting a fall in hepatic vascular resistance. However, after the 40-mg dose, a reflex splanchnic vasoconstriction elicited by the fall in arterial pressure (-19%) appeared to contribute to the greater reduction in portal pressure, as suggested by a significant decrease in azygos blood flow (-15%). These beneficial effects on portal pressure were not associated with adverse effects on liver function, as evaluated by measurements of the hepatic clearance of indocyanine green and the hepatic intrinsic clearance. Neither dose of Is-5-Mn caused significant changes in these quantitative parameters of liver function. These findings suggest that Is-5-Mn could be a potentially useful and safe agent in the treatment of portal hypertension.     

Resistance to isosorbide dinitrate in patients with severe chronic heart failure: incidence and attempt at hemodynamic prediction

Oral isosorbide dinitrate has been widely used to lower elevated left ventricular filling pressure in patients with chronic heart failure. Although the recommended dose of this drug is 40 mg every 6 h, failure to respond to this dose has been observed in many patients with heart failure. In the present study the incidence of resistance to isosorbide dinitrate was evaluated and an attempt was made to identify baseline hemodynamic predictors for this phenomenon in 50 patients with severe chronic heart failure due to left ventricular systolic dysfunction (mean left ventricular ejection fraction 0.23 +/- 0.08). Twenty-seven (54%) of the 50 patients responded to 40 mg of isosorbide dinitrate (greater than 20% decrease in mean pulmonary artery wedge pressure sustained greater than or equal to 1 h) and 23 patients (46%) failed to respond. Nonresponders to 40 mg of isosorbide dinitrate had a significantly higher baseline right atrial pressure than did responders (14 +/- 5 versus 10 +/- 6 mm Hg, p less than 0.02). In addition, all 7 patients with a baseline right atrial pressure of less than 7 mm Hg and 12 of 14 patients with a baseline right atrial pressure less than 10 mm Hg responded to 40 mg. No significant differences were noted between responders and nonresponders in any other baseline hemodynamic or clinical variables, or in peak isosorbide dinitrate serum levels (32 +/- 19 ng/ml in nonresponders versus 44 +/- 36 ng/ml in responders). Of the 23 nonresponders to 40 mg, 22 received a higher dose (80 to 120 mg).(ABSTRACT TRUNCATED AT 250 WORDS)     

Portal venous flow in response to acute beta-blocker and vasodilatatory treatment in patients with liver cirrhosis

The drugs currently under investigation in the prevention of recurrent gastrointestinal bleeding in cirrhosis are likely to decrease the portal pressure by means of a primary reduction of portal blood flow. The hemodynamic effects of beta-blocking agents and vasodilatory drugs were noninvasively measured in eight patients with cirrhosis by means of pulsed echo-doppler equipment. Portal caliber, blood velocity and flow were recorded hourly after a single dose of propranolol (40 mg p.o.) or atenolol (100 mg p.o.), and every 5 min after treatment with isosorbide dinitrate (5 mg sublingually). The drugs were administered at random with an interval of 2 days or more. The portal caliber decreased after atenolol, but did not change after propranolol and isosorbide. The blood velocity decreased by 29 +/- 2% 3 hr after propranolol, by 26 +/- 2% 3 hr after atenolol and by 31 +/- 3% 15 min after isosorbide. The portal blood flow decreased by 0.29 +/- 0.03 liters per min after propranolol, by 0.34 +/- 0.06 after atenolol and by 0.26 +/- 0.03 after isosorbide, without any difference among the various treatments. beta-blockers and vasodilatory drugs have comparable effects on portal blood flow. beta 1-selective and nonselective beta-blockers are similarly effective in keeping with the hypothesis that changes in portal blood flow are mainly due to the block of beta 1-receptors.     

Vascular hyporeactivity persists despite increased contractility after long-term administration of isosorbide dinitrate in portal hypertensive rats

Background/Aims: Portal hypertension is associated with decreased vascular responsiveness to vasoconstrictors, which may contribute to the hyperdynamics. Isosorbide dinitrate is an effective portal hypotensive drug. The present study aimed to investigate whether chronic administration of isosorbide dinitrate could affect vascular responsiveness in portal hypertensive rats.Methods: Portal hypertension was induced by partial portal vein ligation. Sham-operated (Sham) rats served as controls. There were four animal groups for this study: portal vein ligation-isosorbide dinitrate groups, portal vein ligation-vehicle (Veh) group, Sham-isosorbide dinitrate group and Sham-Veh group. Isosorbide dinitrate (5 mg · kg⁻¹ · 12 h⁻¹ was given by gavage for 8 days starting 1 day before ligation and continuing thereafter. Mesenteric arteries were removed for contractile study after hemodynamic measurement.Results: Contractile responses to KCl (15–90 mM) and phenylephrine (10⁻⁹−10⁻⁴ M) were recorded. Both vascular reactivity and sensitivity were significantly reduced in portal vein ligation rats as compared to Sham rats. Chronic isosorbide dinitrate treatment reduced portal venous pressure in portal vein ligation rats. Moreover, the maximal contractile responses to KCl and phenylephrine were significantly enhanced in both portal vein ligation and Sham rats after isosorbide dinitrate treatment, but relative hyporeactivity persisted in portal vein ligation rats. In contrast, a single dose of isosorbide dinitrate did not alter the contractile sensitivity or reactivity to KCl or phenylephrine in either portal vein ligation or Sham rats.Conclusion: Our results show that long-term administration of isosorbide dinitrate enhanced vascular contractility in both portal vein ligation and Sham rats, but relative hyporeactivity persisted in portal vein ligation rats.     

Portal hemodynamics during nitroglycerin administration in cirrhotic patients

Nitroglycerin is a potent venous dilator and a mild arterial vasodilator that has been shown to improve the hemodynamic response to vasopressin in portal hypertensive patients and to decrease portal pressure in experimental animals. In order to determine the effect of nitroglycerin on portal venous hemodynamics, we studied 11 patients with alcoholic cirrhosis before and during the administration of sublingual nitroglycerin (0.4 and 0.6 mg). The hepatic venous pressure gradient (which was obtained by subtracting the free hepatic venous pressure from the wedged hepatic venous pressure) decreased from 17.9 +/- 6.5 mm Hg (mean +/- S.D.) to 15.1 +/- 5.1 mm Hg (p less than 0.02) at the peak of the effect, which occurred from 2 to 12 min after nitroglycerin administration. The mean arterial pressure was reduced from 96 +/- 10 mm Hg to a peak decrease of 76 +/- 18 mmHg (p less than 0.001). The peak change in the hepatic venous pressure gradient induced by nitroglycerin correlated directly with the peak change in mean arterial pressure (r = 0.79, p less than 0.01). There was a moderate increase in heart rate in response to the decrease in blood pressure (73 +/- 15 to 83 +/- 15 beats per min, p less than 0.001). Two of the 11 patients did not reduce their hepatic venous pressure gradient after 0.6 mg nitroglycerin. Reductions in portal pressure were observed with both increases and moderate decreases in azygos blood flow, suggesting that, as observed in experimental animals, the portal-pressure-reducing effect of nitroglycerin could be due to two different and independent mechanisms, a reduction in portal blood flow or portal-collateral vasodilatation.     

Hemodynamic assessment of oral peripheral vasodilator therapy in chronic congestive heart failure: prolonged effectiveness of isosorbide dinitrate.

To evaluate the effectiveness of oral vasodilator therapy in chronic congestive heart failure, 20 mg of isosorbide dinitrate or placebo was administered orally in double-blind fashion to 25 patients with congestive heart failure. In 15 patients receiving isosorbide dinitrate, pulmonary arterial wedge pressure decreased 5 minutes to 5 hours after drug administration; the peak reduction was observed at 1 hour (from 23 to 14 mm Hg; P less than 0.001). Wedge pressure decreased to normal (12 mm Hg or less) in 8 of the 15 patients (Group I) but remained greater than 12 mm Hg in 7 (Group II). Reductions in mean systemic arterial pressure, systemic vascular resistance and pressure-time per minute also occurred. Indexes of pump output were unchanged in the 15 who received isosorbide dinitrate but tended to decrease slightly in Group I. Stroke index (from 23 to 26 cc/m2) and stroke work index (from 21.4 to 24.1 g-m/m2) increased slightly but significantly (P less than 0.05) in Group II. Thus the prinicpal hemodynamic action of isorbide dinitrate is marked and sustained reduction in left ventricular filling pressure without pronounced effect on cardiac output. This agent should be used in congestive heart failure primarily for relief of congestive symptoms.     

The diameter of arterial and venous abdominal vessels during acute and chronic administration of nitrates. A sonographic study

Fourteen male patients with coronary heart disease were randomly assigned to treatment periods with isosorbide dinitrate (ISDN) 120 mg/day (6 X 20 mg) and placebo for 4 weeks each, according to a double-blind protocol with intraindividual cross-over. The luminal diameters of the superior mesenteric artery, the hepatic artery, the superior mesenteric vein and the portal vein were determined sonographically in the supine position on days 1, 14 and 28 of both treatment periods 90 min after drug intake. The measurements were repeated after 1.6 mg sublingual nitroglycerin. On day 1 of drug intake the vessel diameters increased significantly after ISDN as compared to placebo: superior mesenteric artery: +11%; hepatic artery: +26%; superior mesenteric vein: +17%; portal vein: +11% (p less than 0.05). No differences in luminal diameters between both drug regimens were found on days 14 and 28. Additional nitroglycerin caused a marked diameter increase during the placebo period (14-21%; p less than 0.001) and on days 14 and 28 of ISDN therapy, while the drug effects were absent after maximal ISDN-induced vasodilatation on day 1. Thus, nitroglycerin and isosorbide dinitrate administered acutely caused a comparable vasodilatation of arterial and venous vessels in the splanchnic region. During sustained therapy with isosorbide dinitrate the vasodilatory effects of the drug were lost. It is supposed that a decrease of blood pooling in the splanchnic region occurs during sustained ISDN therapy. Despite this tolerance development to the circulatory effects of isosorbide dinitrate, nitroglycerin remained effective with regard to arterial and venous vasodilatation.     

Reactivity of eccentric and concentric coronary stenoses in patients with chronic stable angina

Dynamic coronary stenoses may be the cause of a variable angina threshold and rest angina in patients with chronic stable angina. It has been suggested that eccentric but not concentric coronary artery stenoses have the potential for dynamic changes of caliber in response to vasoactive stimuli. The vasomotor response of eccentric (asymmetric narrowing) and concentric (symmetric narrowing) coronary stenoses to ergonovine (20 micrograms intracoronary or 300 micrograms intravenous) and isosorbide dinitrate (1 mg intracoronary) was studied in 51 patients with chronic stable angina. Diameter of reference segments (angiographically normal segments proximal to the stenoses) and that of eccentric (n = 30) and concentric (n = 35) coronary stenoses that ranged from 50% to 90% luminal diameter reduction were measured by computerized quantitative angiography before and after ergonovine and isosorbide dinitrate. Ergonovine reduced stenosis diameter (by greater than or equal to 10%) in 80% of eccentric stenoses and 42% of concentric stenoses (p less than 0.05). Mean (+/- SEM) diameter reduction with ergonovine was 19 +/- 3% and 9.5 +/- 2% for eccentric and concentric stenoses, respectively (p less than 0.05). Isosorbide dinitrate increased coronary diameter (by greater than or equal to 10%) in 70% of eccentric and 43% of concentric stenoses (p less than 0.05). Mean diameter of eccentric stenoses increased from 1.15 +/- 0.05 to 1.35 +/- 0.06 mm after nitrate (18.6 +/- 2.5%), whereas diameter of concentric stenoses increased from 1.05 +/- 0.05 to 1.14 +/- 0.05 mm (10 +/- 2.5%) (p less than 0.05). Average dilation of reference segments with administration of isosorbide dinitrate and constriction with ergonovine were not significantly different in patients with concentric and eccentric stenoses.(ABSTRACT TRUNCATED AT 250 WORDS)     

Role of pentobarbitone anaesthesia and sympathetic tone in the haemodynamic effects of isosorbide dinitrate in rats with cirrhosis

The haemodynamic effects of nitrovasodilators and their mechanisms of action on portal hypertension remain unclear. The splanchnic and systemic haemodynamic response to the infusion of isosorbide dinitrate (100 μg/kg per min), a nitrovasodilator, was investigated in cirrhotic rats. The role of the conscious state in the haemodynamic response to isosorbide dinitrate was examined using rats that were anaesthetized with pentobarbitone. The role of sympathetic tone in the haemodynamic response to isosorbide dinitrate was examined using rats pretreated with the ganglion blocker hexamethonium. Isosorbide dinitrate had no haemodynamic effects in conscious, unblocked normal and cirrhotic rats. Isosorbide dinitrate had no haemodynamic effects in normal and cirrhotic rats treated with hexamethonium. In normal anaesthetized rats, isosorbide dinitrate significantly decreased systemic vascular resistance (414±25 vs 290±26 dyn.s/cm⁵ per 100 g). In cirrhotic anaesthetized rats, isosorbide dinitrate significantly decreased mean arterial pressure (98±6 vs 79±7 mmHg), systemic vascular resistance (318±30 vs 207±10 dyn.s/cm⁵ per 100 g), portal pressure (14.0±1.0 vs 11.3±0.9 mmHg) and portal territory vascular resistance (1362±163 vs 1031±182 dyn.s/cm⁵ per 100 g). In conclusion, this study shows that the portal hypotensive effects of isosorbide dinitrate depend upon the alterations of vascular tone by pentobarbitone.