Limb vasoconstriction after successful angioplasty of the left anterior descending coronary artery

BACKGROUND

Coronary vasoconstriction has been described after uncomplicated percutaneous transluminal coronary angioplasty (PTCA). However, it is still unknown whether this phenomenon is limited to coronary circulation. The present study was planned to assess the effects of a successful PTCA on forearm blood flow (FBF) and resistance. The role of alpha-adrenoceptors and calcium antagonist agents on PTCA-induced limb blood flow changes was also investigated.

METHODS AND RESULTS

We prospectively studied 37 patients scheduled for elective single PTCA of the left anterior descending coronary artery. All patients had evidence of exercise-induced myocardial ischemia. All vasoactive drugs were withdrawn for at least 48 hours before the study. FBF was measured by calibrated venous occlusion plethysmography. A significant reduction of FBF was observed at 1, 5, and 15 minutes after PTCA (from 3.7 +/- 1.2 to 2.7 +/- 1.5, 3.0 +/- 1.6, and 2.9 +/- 1.9 mL/100 mL tissue per minute, respectively; all P < .05 versus baseline). Vascular forearm resistance also increased at 1, 5, and 15 minutes after PTCA (from 27 +/- 8 to 42 +/- 16, 37 +/- 10, and 43 +/- 19 U, respectively; all P < .05 versus baseline). Phentolamine (12 microgram.kg-1.min-1, n = 7) or verapamil (3.5 micrograms.kg-1.min-1, n = 7) also was infused intra-arterially. PTCA-induced forearm vasoconstriction was completely abolished by pretreatment with regional infusion of phentolamine or verapamil.

CONCLUSIONS

After an uncomplicated PTCA of the left anterior descending coronary artery, a reduction in FBF and an increase in forearm vascular resistance were observed. This peripheral vasoconstrictive response was probably due to alpha-adrenergic stimulation and was abolished by intra-arterial infusion of calcium antagonist agents.

Smooth muscle cell proliferation is proportional to the degree of balloon injury in a rat model of angioplasty

BACKGROUND

A variable degree of smooth muscle cell (SMC) proliferation after balloon injury has been reported in previous rat studies. It is unknown whether balloon injury induces c-fos expression and whether it is related to the degree of vascular injury in vivo. Therefore, we tested the hypothesis that proportional increases in neointimal formation and c-fos expression might be present after different degrees of balloon dilation.

METHODS AND RESULTS

Angioplasty of the carotid artery was performed with a balloon catheter. Vascular injury was evaluated at 0, 0.5, 1.0, 1.5, and 2 atm (n = 6 for all). In 40 additional rats, total RNA dot blots were performed to assess the effect of various degrees of balloon injury on c-fos expression. SMC proliferation proportional to the increases of inflation pressure was found between 0 and 2 atm with neointimal areas of 0.002 +/- 0.002, 0.069 +/- 0.014, 0.128 +/- 0.043, 0.190 +/- 0.010, and 0.255 +/- 0.041 mm2, respectively. When the degree of SMC proliferation (neointima and neointima/media ratio) was plotted against balloon inflation pressure, a linear relation was observed (r = .733, P < .001 and r = .755, P < .001, respectively). An increase in c-fos expression proportional to the degree of injury was found 30 minutes after injury.

CONCLUSIONS

Neointimal proliferation produced by balloon injury is related to balloon inflation pressure, supporting the concept of an SMC proliferative response proportional to the degree of injury. The increase in SMC proliferation is associated with a proportional increase in the early expression of the c-fos nuclear proto-oncogene.

Incidence and complexity of ventricular ectopy during Holter monitoring in patients with exercise-induced myocardial ischemia and normal or mildly reduced left ventricular function

We aimed to assess the relationship between frequent and complex ventricular ectopy by continuous electrocardigraphic 24-hours Holter monitoring in patients with coronary artery disease and inducible ischemia during exercise procedures. We investigated 609 consecutive patients. They were referred for chest pain (28% with a previous myocardial infarction, older than 6 months). In all population patients radionuclide ventriculography showed a global normal or mildly reduced left ventricular function (ejection fraction > 45%). All patients showed exercise-induced myocardial ischemia (ST depression) and exercise thallium-201 reversible defects. During Holter monitoring, in study population, divided according to incidence of premature ventricular complexes (PVC), we found a higher prevalence of complex ventricular arrhythmias (CVA) (bigeminy, couplets, ventricular tachycardia, multiformity) in patients with high incidence of PVC. The relationship between frequent and complex ventricular ectopy has been observed also during ischemic ST shifts occuring during 24-hours monitoring. In contrast, the R on T phenomenon was not related to incidence of PVC. Therefore, in patients with exercise-induced myocardial ischemia and global normal or mildly reduced left ventricular function there is a relationship between frequent and complex ventricular ectopy, as previously suggested in CAD patients with depressed left ventricular function.

Different protocols generate variations in systolic blood pressure response after exercise in patients with coronary artery disease

Some patients with coronary artery disease (CAD) and exercise-induced myocardial ischemia demonstrate no change or a paradoxical increase in systolic blood pressure (SBP) during recovery following exercise. Previous studies have investigated the significance and clinical usefulness of analysis of recovery SBP response in detecting CAD, but conflicting data have been reported. Different protocols were used for the time of SBP recording and either bicycle or treadmill testing. We studied the exercise response in 64 male patients investigated for CAD who underwent symptom-limited treadmill stress testing during electrocardiographic monitoring and serial recording of blood pressure. Forty-three patients showed on or more stenoses of at least 70% at angiography (CAD). Twenty-one patients with normal coronary tree or slight lesions served as controls. The sensitivity (true positive/all CAD patients), specificity (true negative/all CAD-free patients), and the correct classification rate (correct diagnoses/all subjects) were assessed by standard ST segment analysis and two recovery SBP ratios calculated by dividing the first minute recovery SBP by the immediate postexercise value (RR/R) or by the true peak exercise value (RR/P). ST segment analysis achieved 53% sensitivity, 57% specificity, and 54% correct classification, the RR/R ratio achieved 73%,23%, and 60%, and the RR/P ratio 53%, 71%, and 59%, respectively. There were significant differences in results using these ratios. Time of SBP recording generated discrepancies in recovery SBP ratios. Therefore, differences in the timing of SBP measurement may generate conflicting clinical indications.

Effects of intravenous digoxin on pulmonary venous and transmitral flows in patients with chronic heart failure of different degrees

Acute effects of digoxin on diastole were evaluated noninvasively by combining data simultaneously obtained by Doppler echocardiograms (echo-Doppler) of transmitral and pulmonary venous flow curves in 38 patients with dilated and failing hearts, who had been stable for at least 7 days before the study. According to the resting ejection fraction (EF), patients were subdivided into Group 1 (EF < 30%: n = 20, mean EF values 23 +/- 8%) and Group 2 (EF > or = 30%: n = 18, mean EF values 40 +/- 3%). Significant differences were observed at rest between the two groups in both transmitral (shorter deceleration time and isovolumic relaxation time and increased peak E and E/A ratio in Group 1 vs. Group 2) and transpulmonary (reduced systolic forward component and systolic fraction of the flow curves in Group 1 compared with Group 2 and control subjects) parameters. Digoxin (1 mg subdivided into two doses, each infused over a 15-min period with 2 h between the doses) significantly modified the diastolic profile in Group 1 patients in the absence of statistically relevant changes in EF: a significant decrease of transmitral peak E (from 76 +/- 17 to 60 +/- 15 cm/s, p < 0.05) and E/A ratio (from 2.5 +/- 1 to 1.6 +/- 0.6; p < 0.05) and a significant lengthening of deceleration time (from 115 +/- 20 to 160 +/- 18 ms; p < 0.05) were detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Haemostatic balance in patients with acute focal cerebral vasculopathy

The authors investigated the behaviour of some markers of the haemostatic balance in a group of patients with acute focal cerebral vasculopathy. The series consists of 70 female patients (mean age: 61 +/- 5), 25 of whom suffering from TIA and 45 from thrombotic stroke; 40 normal controls (mean age 43 +/- 5) were also considered. For each patient after an overnight fasting a withdrawal of venous blood was done within 24-36 hours after the admission. For each sample the determination of seven prothrombotic markers [(fibrinogen (F), factor VII (F VII), antithrombin III (AT III), protein C (PC), protein S (PS) (coagulometric method IL), tissue plasminogen activator (t-PA), plasminogen activator inhibitor (PAI-1) (ELISA method Boehringer)] and of three prethrombotic markers [(fibrinopeptide A (FPA), beta-thromboglobulin (BTG) and D-dimer (D-D) (ELISA method, Boehringer)] was performed. The results obtained in the group of the cerebrovasculopathic patients compared to the controls showed a significant increase of F (p < 0.001), F VII (p < 0.005), BTG (p < 0.05) and D-D (p < 0.01), whereas significant differences regarding AT III, PC, PS, t-PA, PAI and FPA were not observed. The authors hypothesized that the increased levels of fibrinogen and factor VII in the cerebrovascular subjects, globally considered, may depend on a marked prothrombotic state, linked in a pathogenetic sense to the vascular disease; the existence of a prethrombotic state is also documented by the increase of betathromboglobulin and D-dimer.(ABSTRACT TRUNCATED AT 250 WORDS)

[Cardiovascular risk in arterial hypertension: role of family history]

This is a short and non-comprehensive review of clinical, epidemiological and experimental observations that support the importance of the genetic background in the susceptibility to vascular injury and acute cardiovascular accidents in hypertension. In particular, previous observations suggesting the predictive role of positive family history are discussed. In addition, we introduce data obtained in our laboratory through an experiment based on rat strain crossing. This novel approach may provide a well characterized phenotype that allows gene dissection in hypertension with specific regard to cosegregation with vascular accidents.

[Gene therapy for the treatment of restenosis after coronary angioplasty]

Accumulation and proliferation of vascular smooth muscle cells are associated with atherosclerosis and hypertension. Proliferation of smooth muscle cells constitutes a major pathological event responsible for long-term failure of coronary and peripheral arterial bypass graft as well as the development of restenosis after percutaneous transluminal coronary angioplasty (PTCA). The incidence of restenosis after PTCA has been reported to be as high as 40-45% within 3-6 months. Major advantages in recombinant deoxyribonucleic acid (DNA) technology and eukaryotic gene regulation allow to hypothesize gene therapy as a potential treatment for inherited and acquired diseases. Gene therapy is the introduction of genes into somatic cells to correct an inherited or acquired disorder through the synthesis of missing or defective protein. Although no disease has yet been treated by gene therapy, several gene transfer protocols have recently been undertaken. We have studied the expression of foreign DNA that has been introduced into smooth muscle cells after balloon carotid injury in a rat model of angioplasty. The effects of different degree of balloon injury on neointima formation and c-fos expression was also assessed. Our data demonstrate that site-specific gene expression can be achieved by direct gene transfer in vivo and could be applied to the treatment of restenosis after PTCA.

Coronary artery vasoconstriction after successful single angioplasty of the left anterior descending artery

Percutaneous transluminal coronary angioplasty is associated with spontaneous transient vasoconstriction. The mechanisms by which coronary vasoconstriction occurs distally to a successful dilated stenosis after coronary artery angioplasty are still unknown. The present study was planned to investigate the effect of successful coronary artery angioplasty on coronary vasomotion distal to a dilated stenosis and in the control vessel and the role of alpha-adrenergic receptors on coronary vasomotion after successful coronary artery angioplasty. We prospectively studied 32 consecutive patients scheduled for elective single coronary artery angioplasty of the left anterior descending coronary artery. Only aspirin, 325 mg, or nitroglycerin was allowed in the week before the study; no premedication with diazepam or other drugs was given. In group 1 (control patients, n = 20), quantitative coronary angiography was performed in the control state; 5 and 15 minutes after coronary artery angioplasty; and after intracoronary nitroglycerin infusion, 300 micrograms. In group 2 (n = 12), intracoronary phentolamine, 2 mg, was infused regionally through the balloon catheter before the coronary artery angioplasty, and coronary angiography was performed at baseline, 15 minutes after balloon deflation, and after nitroglycerin infusion. In group 1, constriction of the coronary segment distal to a dilated stenosis (2.4 +/- 0.8 to 2.1 +/- 0.6 mm, -14.6% vs baseline; p < 0.05) and of the circumflex coronary artery segment (2.8 +/- 0.7 to 2.5 +/- 0.6 mm, -10.7% vs baseline, p < 0.05) occurred 15 minutes after coronary artery angioplasty. The degree of vasoconstriction was not correlated with the lesion severity before coronary artery angioplasty.(ABSTRACT TRUNCATED AT 250 WORDS)

Forearm vascular responsiveness to alpha 1- and alpha 2-adrenoceptor stimulation in patients with congestive heart failure

BACKGROUND

The alpha-adrenergic component of the sympathetic nervous system plays a major role in the pathophysiology, clinical manifestations, and natural history of human congestive heart failure (CHF). However, the functional integrity of vascular alpha 1- and alpha 2-adrenoceptors in CHF remains to be elucidated. The present study was designed to assess the vascular responsiveness of alpha 1- and alpha 2-adrenoceptors in patients with CHF.

METHODS AND RESULTS

To evaluate alpha 1- and alpha 2-adrenoceptor responsiveness, we studied the effects of the regional infusion into the brachial artery of increasing doses of phenylephrine (a selective alpha 1-adrenoceptor agonist) and BHT 933 (a selective alpha 2-adrenoceptor agonist) on vascular responses in 12 healthy subjects and in 24 patients with CHF secondary to primary dilated cardiomyopathy or ischemic heart disease. Left ventricular ejection fraction was measured by radionuclide angiography, and forearm blood flow was determined by venous occlusion plethysmography. Phenylephrine reduced forearm blood flow in normal subjects from 5.2 +/- 0.9 to 2.5 +/- 0.6 mL per 100 mL of tissue/min (P < .05) at the highest dose (-50.8 +/- 4.8% versus baseline). A similar vasoconstriction was obtained in patients with CHF (from 3.5 +/- 0.5 to 1.5 +/- 0.2 mL per 100 mL of tissue/min (P < .05) (-58.7 +/- 5.0% versus baseline). The dose-response curves produced by phenylephrine in the two groups were comparable. The highest dose of BHT 933 reduced forearm blood flow in normal subjects from 5.3 +/- 0.9 to 2.3 +/- 0.6 mL per 100 mL of tissue/min (P < .05) (-59.0 +/- 4.9% versus baseline). In patients with CHF, a similar vasoconstriction was obtained (from 4.2 +/- 0.8 to 1.5 +/- 0.3 mL per 100 mL of tissue/min, P < .05, -62.1 +/- 6.5% versus baseline). The dose-response curves produced by BHT 933 also were comparable in the two groups. In patients with CHF, plasma concentrations of norepinephrine were significantly higher than in normal subjects.

CONCLUSIONS

The results of the present study demonstrate that alpha 1- and alpha 2-adrenoceptor stimulations produced an equivalent vasoconstriction in patients with CHF and in normal subjects. This indicates that the vascular responsiveness to alpha-adrenoceptor agonists may be preserved in the limb vessels of patients with CHF.

Effects of converting enzyme inhibition on heart period variability in patients with acute myocardial infarction

BACKGROUND

Heart period variability provides useful prognostic information on autonomic cardiac control, and a strong association has been demonstrated after myocardial infarction (MI) between cardiac mortality, sudden death, and reduced total power, ultralow-frequency (ULF) power, and very-low-frequency (VLF) power. Converting enzyme inhibitors are widely used in MI patients, but their influence on heart period variability remains to be defined.

METHODS AND RESULTS

Time- and frequency-domain measures of heart period variability were calculated from 24-hour Holter monitoring in 40 patients with a first uncomplicated MI. After baseline examination between 48 and 72 hours after symptom onset, patients were randomly assigned to placebo or captopril administration, and on the third day, 24-hour Holter monitoring was repeated. No changes in time and frequency domain were detectable after placebo. After captopril, the SD of all normal RR (NN) intervals (SDNN) increased from 90 +/- 29 to 105 +/- 30 milliseconds (P < .01); the SD of the average NN intervals for all 5-minute segments (SDANN index) and the mean of the SDs of all NN intervals for all 5-minute segments (SDNN index) also increased from 74 +/- 24 to 90 +/- 26 milliseconds (P < .01) and from 45 +/- 17 to 49 +/- 15 milliseconds (P < .05), respectively. The root mean square successive difference (r-MSSD) and the percent of differences between adjacent NN intervals > 50 milliseconds (pNN50) remained unchanged. In regard to frequency-domain measures, after captopril, total power (ln unit) increased from 8.28 +/- 0.42 to 8.47 +/- 0.30 (P < .01); considering the frequency bands, a significant increase was observed in ULF (P < .01), VLF (P < .05), and low-frequency (LF) power (P < .05), whereas high-frequency (HF) power remained unchanged.

CONCLUSIONS

This study supports the hypothesis that the renin-angiotensin system modulates the amplitude of ULF and VLF power. Furthermore, it demonstrates that in MI patients, converting enzyme inhibition favorably modifies measures of heart period variability strongly associated with a poor prognosis.

Oxygen radicals inhibit human plasma acetylhydrolase, the enzyme that catabolizes platelet-activating factor

Platelet-activating factor (PAF) can exert profound inflammatory effects at very low concentrations. In plasma, PAF is hydrolyzed to lyso-PAF by acetylhydrolase, an enzyme that circulates bound to LDL. Previous studies suggest that oxygen radicals may act synergistically with PAF to potentiate tissue injury. However, mechanisms underlying this interaction have not been elucidated. In this study we investigated whether oxygen radicals may inactivate PAF acetylhydrolase. PAF acetylhydrolase activity was measured in human plasma and purified LDL before and after exposure to radicals (10-20 nmol/min per ml) generated by xanthine/xanthine oxidase. Oxygen radicals induced > 50% loss of PAF acetylhydrolase activity within 60 s and almost complete inactivation by 10 min. This phenomenon was irreversible and independent of oxidative modification of LDL. Inactivation occurred without changes in the affinity constant of the enzyme (Km was 17.9 microM under control conditions and 15.1 microM after exposure to oxygen radicals). Inactivation was prevented by the scavengers superoxide dismutase or dimethylthiourea or by the iron chelator deferoxamine. Thus, superoxide-mediated, iron-catalyzed formation of hydroxyl radicals can rapidly and irreversibly inactivate PAF acetylhydrolase. Since concomitant production of PAF and oxygen radicals can occur in various forms of tissue injury, inactivation of acetylhydrolase might represent one mechanism by which oxygen radicals may potentiate and prolong the proinflammatory effects of PAF.

Local effect of serotonin released during coronary angioplasty

BACKGROUND

Serotonin is released after the aggregation of platelets, a phenomenon that may occur after coronary angioplasty. We sought to determine whether serotonin is released into the coronary circulation during coronary angioplasty and to assess whether serotonin can affect coronary-artery tone during angioplasty.

METHODS

Blood samples were drawn from the ascending aorta and the coronary sinus of eight patients scheduled to undergo angioplasty of the left anterior descending or circumflex coronary artery. Samples were obtained before angioplasty and after each balloon dilation. The dimensions of arterial segments distal to the site of dilation were measured angiographically before angioplasty and 5 and 15 minutes after the last dilation in these eight patients and in seven similar patients; the latter group was treated with ketanserin, a serotonin2-receptor antagonist, before angioplasty.

RESULTS

Before the eight patients underwent angioplasty, their mean (+/- SE) plasma serotonin level in the aorta was 2.5 +/- 0.7 ng per milliliter and that in the coronary sinus was 2.3 +/- 0.6 ng per milliliter (P = 0.34). The serotonin level in plasma from the coronary sinus rose significantly, to 31.5 +/- 13.5, 17.6 +/- 5.3, and 29.1 +/- 8.1 ng per milliliter after the first, second, and third dilations, respectively (P = 0.014 for the comparison with preoperative levels). In contrast, the serotonin level in plasma from the ascending aorta did not change. The cross-sectional area of the coronary artery was significantly reduced 5 and 15 minutes after the last dilation (from a preoperative value of 3.7 +/- 0.5 mm2 to 2.7 +/- 0.4 mm2 15 minutes after the last dilation; P = 0.011). This vasoconstriction was significantly blunted in the seven patients who received ketanserin (from 3.7 +/- 0.5 mm2 before angioplasty to 3.9 +/- 0.4 mm2 after 15 minutes) (P = 0.017 for comparison with the eight patients who did not receive ketanserin).

CONCLUSIONS

Serotonin is released into the coronary circulation during angioplasty, and this vasoactive substance may contribute to the occurrence of vasoconstriction distal to the dilated site. The vasoconstriction is attenuated by ketanserin, a serotonin2-receptor antagonist.

IPO-V2: a prospective, multicenter, randomized, comparative clinical investigation of the effects of sulodexide in preventing cardiovascular accidents in the first year after acute myocardial infarction

OBJECTIVES

This study was conducted to assess the efficacy of sulodexide, a glycosaminoglycan compound with antithrombotic properties, in preventing death and thromboembolic events after acute myocardial infarction.

BACKGROUND

Antithrombotic therapy has been found to play an important role in the prevention of cardiovascular events and death after acute myocardial infarction. Glycosaminoglycan-containing compounds, including sulodexide, show profibrinolytic and antithrombotic properties that render them suitable for use in patients after infarction.

METHODS

A total of 3,986 patients who had recovered from acute myocardial infarction were randomized to receive either the standard therapy routinely administered at each study center, excluding antiplatelet and anticoagulant drugs (control group, 1,970 patients), or the standard therapy plus sulodexide (treated group, 2,016 patients). Between 7 and 10 days after the episode of acute myocardial infarction, sulodexide was administered as a single daily 600-lipoprotein-lipase-releasing unit (LRU) intramuscular injection for the 1st month, followed by oral capsules of 500 LRU twice daily. Patients were evaluated for > or = 12 months.

RESULTS

At the end of the study, 140 deaths (7.1%) were recorded in the control group and 97 (4.8%) in the sulodexide group (32% risk reduction, p = 0.0022, chi-square test). A total of 90 patients (4.6%) in the control group had a further infarction, compared with 66 (3.3%) in the sulodexide group (28% risk reduction, p = 0.035). Furthermore, a reduction in left ventricular thrombus formation (evaluated by echocardiography) was observed in the sulodexide group (n = 12; 0.6%), compared with values in the control group (n = 25; 1.3%) (53% risk reduction, p = 0.027). Sulodexide was well tolerated and devoid of significant adverse events. All significant results were confirmed by "actual treatment" analyses.

CONCLUSIONS

The study provides evidence that long-term therapy with sulodexide started early after an episode of acute myocardial infarction is associated with reductions in total mortality, rate of reinfarction and mural thrombus formation.

Evidence that mitochondrial respiration is a source of potentially toxic oxygen free radicals in intact rabbit hearts subjected to ischemia and reflow

Previous in vitro studies have shown that isolated mitochondria can generate oxygen radicals. However, whether a similar phenomenon can also occur in intact organs is unknown. In the present study, we tested the hypothesis that resumption of mitochondrial respiration upon reperfusion might be a mechanism of oxygen radical formation in postischemic hearts, and that treatment with inhibitors of mitochondrial respiration might prevent this phenomenon. Three groups of Langendorff-perfused rabbit hearts were subjected to 30 min of global ischemia at 37 degrees C, followed by reflow. Throughout ischemia and early reperfusion the hearts received, respectively: (a) 5 mM KCl (controls), (b) 5 mM sodium amobarbital (Amytal, which blocks mitochondrial respiration at Site I, at the level of NADH dehydrogenase), and (c) 5 mM potassium cyanide (to block mitochondrial respiration distally, at the level of cytochrome c oxidase). The hearts were then processed to directly evaluate oxygen radical generation by electron paramagnetic resonance spectroscopy, or to measure oxygen radical-induced membrane lipid peroxidation by malonyl dialdehyde (MDA) content of subcellular fractions. Severity of ischemia, as assessed by 31P-nuclear magnetic resonance measurements of cardiac ATP, phosphocreatine, and pH, was similar in all groups. Oxygen-centered free radical concentration averaged 3.84 +/- 0.54 microM in reperfused control hearts, and it was significantly reduced by Amytal treatment (1.98 +/- 0.26; p < 0.05), but not by KCN (2.58 +/- 0.96 microM; p = not significant (NS)), consistent with oxygen radicals being formed in the mitochondrial respiratory chain at Site I. Membrane lipid peroxidation of reperfused hearts was also reduced by treatment with Amytal, but not with KCN. MDA content of the mitochondrial fraction averaged 0.75 +/- 0.06 nM/mg protein in controls, 0.72 +/- 0.06 in KCN-treated hearts, and 0.54 +/- 0.05 in Amytal-treated hearts (p < 0.05 versus both groups). Similarly, MDA content of lysosomal membrane fraction was 0.64 +/- 0.09 nM/mg protein in controls, 0.79 +/- 0.15 in KCN-treated hearts, and 0.43 +/- 0.06 in Amytal-treated hearts (p < 0.05 versus both groups). Since the effects of Amytal are known to be reversible, in a second series of experiments we investigated whether transient mitochondrial inhibition during the initial 10 min of reperfusion was also associated with beneficial effects on subsequent recovery of cardiac function after wash-out of the drug. At the end of the experiment, recovery of left ventricular end-diastolic and of developed pressure was significantly greater in those hearts that had been treated with Amytal during ischemia and early reflow, as compared to untreated hearts.(ABSTRACT TRUNCATED AT 400 WORDS)

Short-term and long-term role of platelet activating factor as a mediator of in vivo platelet aggregation

BACKGROUND

Platelet activating factor (PAF) is a phospholipid released upon stimulation by a variety of cells and has been implicated in several pathophysiological events such as asthma and inflammatory diseases. However, although the ability to aggregate platelets in vitro was the first biological activity ascribed to PAF, its role in contributing to the in vivo formation of arterial thrombi has not been thoroughly clarified.

METHODS AND RESULTS

Intravascular platelet aggregation was initiated in two different animal models of arterial stenosis and endothelial injury. An external constrictor was positioned around rabbit carotid arteries and canine coronary arteries. After placement of the constrictor, a typical pattern of flow developed in the stenotic vessels. This pattern of flow, characterized by progressive reductions of carotid or coronary blood flow followed by spontaneous or induced restorations of flow (cyclic flow variations, CFVs), is related to recurrent platelet aggregation at the site of the stenosis followed by dislodgment of the thrombus. After observing CFVs for 30 minutes, BN52021 (up to 1.2 mg/kg), a potent and selective PAF antagonist, was given intravenously to rabbits (n = 12) and dogs (n = 10). BN52021 completely inhibited CFVs in 10 of 12 rabbits, whereas it was relatively ineffective in abolishing CFVs in dogs (only 2 of 10 animals inhibited). This different effect of BN52021 was not explained by too small a dose of the drug to achieve a complete blockade of PAF receptors in dogs, since ex vivo platelet aggregation was completely inhibited in both rabbits and dogs in response to exogenous PAF at concentrations up to 10(-5) mol/L. In a second group of 10 dogs, the hypothesis that PAF may become an important mediator of CFVs in dogs only several hours after endothelial injury was tested. After 30 minutes of baseline CFVs, these animals received a bolus of BN52021 up to 1.2 mg/kg. After this treatment, CFVs were completely abolished in 2 of 10 animals. The remaining 8 dogs were followed for an additional 8-hour period, at the end of which a second bolus of BN52021 was given. At this time, BN52021 was effective, as CFVs were abolished in 6 of 8 animals. These effects of BN52021 at 8 hours were not the consequence of a cumulative dose of the compound, since ex vivo platelet aggregation in response to PAF returned to baseline values immediately before administering the second dose. To identify possible sources of PAF other than aggregating platelets at the site of arterial stenosis, dogs in a third group were killed after 30 minutes (n = 7) and after 8 hours (n = 8) of CFVs. Histological sections of the stenotic coronary artery showed a marked leukocyte infiltration in these arterial segments after 8 hours of CFVs, whereas sections from dogs killed after 30 minutes showed only moderate or no infiltration.

CONCLUSIONS

These data demonstrate that PAF plays an important role as a mediator of platelet aggregation in vivo in rabbits and dogs. In the canine model, PAF appears to become more important after leukocyte infiltration of the arterial wall, as it may contribute to initiating enough platelet activation to lead to cyclic flow variations at sites of arterial stenosis and endothelial injury. Data from the present study suggest that PAF antagonists may be used as antiplatelet agents.

Effect of coenzyme Q10 therapy in patients with congestive heart failure: a long-term multicenter randomized study

The improved cardiac function in patients with congestive heart failure treated with coenzyme Q10 supports the hypothesis that this condition is characterized by mitochondrial dysfunction and energy starvation, so that it may be ameliorated by coenzyme Q10 supplementation. However, the main clinical problems in patients with congestive heart failure are the frequent need of hospitalization and the high incidence of life-threatening arrhythmias, pulmonary edema, and other serious complications. Thus, we studied the influence of coenzyme Q10 long-term treatment on these events in patients with chronic congestive heart failure (New York Heart Association functional class III and IV) receiving conventional treatment for heart failure. They were randomly assigned to receive either placebo (n = 322, mean age 67 years, range 30-88 years) or coenzyme Q10 (n = 319, mean age 67 years, range 26-89 years) at the dosage of 2 mg/kg per day in a 1-year double-blind trial. The number of patients who required hospitalization for worsening heart failure was smaller in the coenzyme Q10 treated group (n = 73) than in the control group (n = 118, P < 0.001). Similarly, the episodes of pulmonary edema or cardiac asthma were reduced in the control group (20 versus 51 and 97 versus 198, respectively; both P < 0.001) as compared to the placebo group. Our results demonstrate that the addition of coenzyme Q10 to conventional therapy significantly reduces hospitalization for worsening of heart failure and the incidence of serious complications in patients with chronic congestive heart failure.

[The effects of the selective intracoronary administration of nifedipine on left ventricular filling anomalies during coronary angioplasty]

Eighteen patients with isolated stenosis of left anterior descending artery, were randomly given 0.2 mg of nifedipine (Group II) or its solvent (Group I) via balloon catheter positioned across the lesion immediately prior balloon occlusion. Peak velocity of early (E peak) and late (A peak) filling, velocity flow integral at early (E area) and late (A area) filling and their ratios (by echo-Doppler) and heart rate, mean aortic and wedge (W) pressures were measured at baseline, 15 and 30 s during balloon occlusion and 10 min after balloon deflation. In Group I we observed a significant decrease in either E peak at 15 and 30 s (-24.7%, -29.3% respectively) and E area (-32.8%, -40.0% respectively) with a non significant increase in both A peak and A area. Accordingly, either E/A peak ratio and E/A area ratio decreased significantly. In Group II no significant changes were observed in the echo-Doppler parameters of left ventricular filling. Wedge pressure also significantly increased in Group I at 15 and 30 s (68.7% and 97.9% respectively), while a significant increase in Group II occurred only at 30 s (32.5%). Heart rate significantly increased only in Group I at 15 and 30 s (10.3% and 11% respectively), while aortic pressure remained unchanged in both groups. Thus, nifedipine given intracoronary in the post-stenotic area just before balloon occlusion prevents left ventricular filling dynamic alteration by preserving early filling.

Endogenous prostaglandin endoperoxides may alter infarct size in the presence of thromboxane synthase inhibition: studies in a rabbit model of coronary artery occlusion-reperfusion

OBJECTIVES

The aim of this study was to assess whether prostaglandin endoperoxides, which continue to be formed in the setting of thromboxane A2 synthase inhibition, might influence the fate of ischemic myocardium in a model of coronary occlusion and reperfusion.

BACKGROUND

It was recently demonstrated that thromboxane A2 synthase inhibitors reduce ischemic myocardial injury through a redirection of prostaglandin (PG) endoperoxides toward the synthesis of "cardioprotective" prostaglandins, such as PGI2, PGE2 and PGD2. However, part of these prostaglandin endoperoxides may also stimulate a receptor, shared with thromboxane A2, mediating platelet aggregation and vasoconstriction.

METHODS

New Zealand White rabbits were subjected to 30 min of coronary occlusion, followed by 5.5 h of reperfusion. Fifteen minutes before reperfusion, the animals were randomized to receive 1) saline solution (control animals, n = 8); 2) SQ 29548, a potent and selective thromboxane A2/PGH2 receptor antagonist (n = 8); 3) dazoxiben, a selective thromboxane A2 synthase inhibitor (n = 8); 4) R 68070 (Ridogrel), a drug with dual thromboxane A2 synthase-inhibiting and thromboxane A2/PGH2 receptor-blocking properties (n = 8); or 5) aspirin + R 68070 (n = 8).

RESULTS

Dazoxiben and R 68070, but not SQ 29548, significantly reduced thromboxane B2 formation and increased plasma levels of 6-keto-PGF1 alpha, PGE2 and PGF2 alpha. Ex vivo platelet aggregation induced by U46619 (a thromboxane A2 mimetic) was inhibited by SQ 29548 and R 68070 but not by dazoxiben. In control animals, infarct size determined at the end of the experiment by triphenyltetrazolium chloride staining averaged 57.7 +/- 3.2% of the area at risk of infarction. The administration of SQ 29548 did not significantly reduce infarct size compared with that in control animals, whereas dazoxiben and R 68070 significantly reduced infarct size to 36.7 +/- 2.8% and 16.6 +/- 3.6% of area at risk of infarction, respectively (p < 0.001 vs. control values). In rabbits treated with R 68070, infarct size was also significantly smaller than that of dazoxiben-treated rabbits (p < 0.01). This protective effect of R 68070 was completely abolished when the drug was administered with aspirin, infarct size in this group averaging 59.7 +/- 1.6% (p = NS vs. control values). No differences in regional myocardial blood flow, systemic blood pressure, heart rate or extent of area at risk were observed among groups.

CONCLUSIONS

Thus, prostaglandin endoperoxides play an important role in modulating the cardioprotective effects of thromboxane A2 synthase inhibitors. The simultaneous inhibition of thromboxane A2 synthase and blockade of thromboxane A2/PGH2 receptors by R 68070 identify a pharmacologic interaction of potential therapeutic importance.

Endothelium-derived relaxing factor modulates platelet aggregation in an in vivo model of recurrent platelet activation

It has been shown that endothelium-derived relaxing factor (EDRF) may inhibit platelet aggregation in vitro through activation of platelet-soluble guanylate cyclase. To assess whether EDRF may also affect platelet function in vivo, intravascular platelet aggregation was initiated by placing an external constrictor around endothelially injured rabbit carotid arteries. Carotid blood flow velocity was measured continuously by a Doppler flow probe placed proximal to the constrictor. After placement of the constrictor, cyclic flow reductions (CFRs), due to recurrent platelet aggregation, developed at the site of the stenosis. After CFRs were observed for 30 minutes, a solution of authentic nitric oxide (NO, n = 10) was infused into the carotid artery via a small catheter placed proximally to the stenosis. Before infusion of NO, CFR frequency averaged 18.3 +/- 2.9 cycles per hour, and CFR severity (lowest carotid blood flow as percentage of baseline values) was 6 +/- 1%. NO completely inhibited CFRs in all animals, as shown by the normal and constant pattern of carotid blood flow (CFR frequency, 0 cycles per hour, p < 0.001; carotid blood flow, 92 +/- 5%, p = NS versus baseline). These effects were transient; CFRs were restored spontaneously within 10 minutes after cessation of NO infusion. After CFRs returned, S-nitroso-cysteine (S-NO-cys), a proposed form of EDRF, was infused into the carotid artery. S-NO-cys also abolished CFRs in all animals but at a significantly lower dose than NO (0.3 +/- 0.1 versus 12 +/- 4 nmol/min). The role of endogenously released EDRF in modulating in vivo platelet function was then tested in additional experiments. In 10 animals, endogenous release of EDRF was stimulated by infusing acetylcholine into the aortic root during CFRs. Infusion of acetylcholine was also associated with a complete inhibition of CFRs, similar to that observed during exogenous infusion of NO or S-NO-cys. These antithrombotic effects of acetylcholine were completely lost when EDRF synthesis was prevented by administration of the L-arginine analogue NG-monomethyl L-arginine (L-NMMA). Furthermore, in six additional rabbits the basal release of EDRF was blocked by L-NMMA after CFRs had been previously abolished with aspirin or the combination of aspirin and ketanserin, a serotonin S2 receptor antagonist. L-NMMA caused restoration of CFRs in all animals, indicating that even the basal release of EDRF is important in modulating platelet reactivity in vivo. Taken together, the data of the present study demonstrate that endogenous EDRF might importantly contribute to the modulation of platelet function in vivo.

Role of alpha 2-adrenoceptors in normal and atherosclerotic human coronary circulation

BACKGROUND

Experimental studies on the effects of alpha 2-adrenoceptors on regional coronary blood flow in normal and ischemic myocardium are highly controversial. A beneficial effect on regional ischemic myocardium has been demonstrated in different animal preparations with either alpha 2-adrenoceptor blockade or stimulation. Animal studies also demonstrated that postsynaptic alpha 2-adrenoceptors mediate vasoconstriction in coronary and femoral vascular beds. The aims of the study were 1) to investigate the effects of regional alpha 2-adrenoceptor stimulation on regional coronary blood flow in subjects with angiographically normal coronary arteries, 2) to assess the effect of alpha 2-adrenoceptor blockade on coronary circulation in control subjects, and 3) to examine the influence of atherosclerosis on coronary blood flow response to alpha 2-adrenoceptor blockade.

METHODS AND RESULTS

The effect of regional administration of BHT 933 (a selective alpha 2-adrenoceptor agonist) was studied in eight subjects with angiographically normal coronary arteries. The coronary blood flow velocity was measured using a subselective intracoronary 3F Doppler catheter and coronary diameter by quantitative coronary angiography. BHT 933 induced a reduction in coronary artery diameter from 2.5 +/- 0.6 mm to 1.8 +/- 0.4 mm (p less than 0.05) as well as in coronary blood flow velocity (from 6.4 +/- 0.9 cm/sec to 4.6 +/- 1.9 cm/sec, p less than 0.01). In some subjects, ST segment abnormalities occurred. In patients with angiographically normal coronary arteries (n = 6), the regional infusion of a selective alpha 2-adrenoceptor blocking agent after beta-blockade did not change coronary diameter or coronary blood flow velocity. In contrast, in patients with significant coronary stenoses (n = 6), regional infusion of an alpha 2-adrenoceptor blocking agent reduced regional coronary artery diameter (from 2.3 +/- 0.5 mm to 2.1 +/- 0.6 mm, p less than 0.01) as well as coronary blood flow velocity (from 5.8 +/- 0.8 cm/sec to 3.7 +/- 0.6 cm/sec, p less than 0.05); in addition, alpha 2-adrenoceptor blockade significantly increased coronary sinus plasma norepinephrine levels (from 300 +/- 144 pg/ml to 429 +/- 207 pg/ml, p less than 0.01).

CONCLUSIONS

The selective in vivo stimulation of alpha 2-adrenoceptors produces a reduction in coronary blood flow and diameter in humans with angiographically normal coronary arteries. alpha 2-Adrenergic blockade does not change coronary blood flow in subjects with angiographically normal coronary arteries (suggesting no resting alpha 2-adrenergic vasoconstrictor tone), whereas in patients with coronary artery stenosis, regional coronary blood flow decreases after alpha 2-receptor blockade. Finally, our data also suggest that alpha 2-adrenoceptors participate in the modulation of sympathetic neuronal norepinephrine release in the human heart.

Effects of converting enzyme inhibition on baroreflex sensitivity in patients with myocardial infarction

BACKGROUND

Baroreflex sensitivity provides useful prognostic information in patients after acute myocardial infarction. However, no data are available about the effects of converting enzyme inhibition on this variable.

OBJECTIVES

The aim of the study was to evaluate the effects of angiotensin-converting enzyme inhibition on baroreflex sensitivity in patients after uncomplicated myocardial infarction.

METHODS

Twenty-five patients after uncomplicated myocardial infarction underwent baroreflex sensitivity evaluation 72 to 96 h after symptom onset and after 4 days of captopril therapy. Twenty additional patients with the same characteristics were evaluated at the same time intervals before and after placebo administration to identify spontaneous baroreflex sensitivity variations. Baroreflex sensitivity was assessed by calculating the regression line relating phenylephrine-induced increases in systolic blood pressure to the attendant changes in the RR interval.

RESULTS

The mean baroreflex sensitivity value increased after captopril administration from 6.5 +/- 4.2 to 11.8 +/- 6.1 ms/mm Hg (p less than 0.01) and in individual analyses increased by greater than 2 ms/mm Hg in 68% of patients. Mean plasma renin activity increased after captopril from 3.7 +/- 2.4 to 8.5 +/- 4.9 ng/ml per h (p less than 0.005). No difference was detectable in baroreflex sensitivity and plasma renin activity values according to the site of necrosis. In the control group, baroreflex sensitivity and plasma renin activity remained unchanged between the two studies.

CONCLUSIONS

This study demonstrates that in patients with uncomplicated myocardial infarction, captopril significantly improves the chronotropic response to baroreceptor stimulation.