Markedly reduced insulin-like growth factor-1 in the acute phase of myocardial infarction.

OBJECTIVES: We investigated whether insulin-like growth factor-1 (IGF-1) is reduced in the early phase of acute myocardial infarction (AMI) and whether such a decrease might influence prognosis. BACKGROUND: Insulin-like growth factor-1 protects against insulin resistance and apoptosis. Although insulin resistance has been reported in AMI, IGF-1 levels have not been investigated. METHODS: We measured serum IGF-1 in 23 patients with AMI within 24 h of symptom onset and in 11 matched controls. In the first 12 patients and controls, we also measured fasting insulin, diurnal growth hormone (GH) and insulin sensitivity (assessed as glucose disappearance or T/2 after an insulin bolus), and repeated IGF-1, insulin and GH after one year. In all patients, 90-day cardiovascular death, recurrent ischemia, reinfarction, revascularization and late malignant arrhythmias were assessed. RESULTS: The AMI patients versus controls showed markedly reduced IGF-1 (115 +/- 112 vs. 615 +/- 300 ng/ml, p < 0.0001) and slower T/2 (-0.98 +/- 1.5 vs. -2.57 +/- 1.0 mg/dl/min, p = 0.01). Low IGF-1 often preceded the rise of myocardial necrosis markers. Patients with 90-day events (n = 12) versus those without had lower IGF-1 (47 +/- 54 vs. 189 +/- 110 ng/ml, p < 0.0001). Acute phase GH and insulin concentrations did not differ significantly from controls. After one year, the patients' IGF-1 values had risen to 460 +/- 242 ng/ml (p = 0.1 vs. controls, p < 0.0005 vs. acute phase), whereas GH levels were lower (0.2 +/- 0.2 vs. 2.5 +/- 2.3 ng/ml, p = 0.01) and insulin levels higher (12.5 +/- 0.2 vs. 3.9 +/- 2.6 microU/ml, p < 0.0001) compared with controls. CONCLUSIONS: In the early phase of AMI, serum IGF-1 levels are markedly reduced and may contribute to adverse outcomes. Reduced IGF-1 preceding the rise of myocardial necrosis markers suggests a possible pathogenetic role. A compensatory increase in IGF-1 appears to occur by one year.

Preinfarction angina and improved reperfusion of the infarct-related artery.

Preinfarction angina and early reperfusion of the infarct-related artery are major determinants of reduced infarct-size in patients with acute myocardial infarction. The beneficial effects of preinfarction angina on infarct size have been attributed to the development of collateral vessels and/or to post-ischemic myocardial protection. However, recently, a relation has been found between prodromal angina, faster coronary recanalization, and smaller infarcts in patients treated with rt-PA: those with preinfarction angina showed earlier reperfusion (p = 0.006) and a 50% reduction of CKMB-estimated infarct-size (p = 0.009) compared to patients without preinfarction angina. This intriguing observation is consistent with a subsequent observation of higher coronary recanalization rates following thrombolysis in patients with prodromal preinfarction angina compared to patients without antecedent angina. Recent findings in dogs show an enhanced spontaneous lysis of platelet-rich coronary thrombi with ischemic preconditioning, which is prevented by adenosine blockade, suggesting an antithrombotic effect of ischemic metabolites. Understanding the mechanisms responsible for earlier and enhanced coronary recanalization in patients with preinfarction angina may open the way to new reperfusion strategies.

Low-grade exercise enhances platelet aggregability in patients with obstructive coronary disease independently of myocardial ischemia.

Moderate and strenuous exercise is known to enhance platelet aggregability in patients with obstructive coronary artery disease (CAD), but the effect of low-grade exercise is not known. We assessed shear-induced platelet aggregability before and after mild exercise (less than or equal to stage III of the modified Bruce protocol) in 27 patients with documented CAD who were receiving aspirin and in 12 subjects without CAD (controls). Ex vivo platelet aggregability was assessed in flowing whole blood as the time to occlude a collagen and adenosine diphosphate-coated ring; shorter times indicated greater aggregability. Aggregability, plasma von Willebrand factor (vWF) antigen, platelet and white cell counts, and hematocrit were measured at baseline, immediately after exercise (peak), and at 30 and 180 minutes after exercise. Exercise of similar workloads induced myocardial ischemia in 14 patients (group 1), but not in the other 13 (group 2) nor in controls. Both patient groups showed a reduction in aggregation time at peak exercise compared with baseline (group 1: 84+/-17 seconds at peak vs 96+/-22 seconds at baseline; group 2: 84+/-20 seconds at peak vs 99+/-20 seconds at baseline; p <0.03 for both comparisons), with a return to baseline values within 180 minutes. No significant variation occurred in controls (89+/-18 seconds at peak vs 85+/-21 second at baseline). Changes in vWF antigen did not differ significantly among groups. Aggregation times did not correlate with hematocrit or platelet and white cell counts. Thus, even low-grade exercise transiently enhances whole blood platelet aggregability in patients with obstructive CAD, but not in controls. The effect is independent of myocardial ischemia, occurs despite aspirin, and is likely dependent on hemodynamic factors interacting with coronary obstructions or dysfunctional endothelium.

Comparison of insulin response to intravenous glucose in healed myocardial infarction, in "cooled-off" unstable and stable angina pectoris, and in healthy subjects.

Fasting and postglucose hyperinsulinemia are recognized risk factors for acute coronary events. The insulin reactivity of patients with acute coronary syndromes, however, has not been carefully compared with that of patients with chronic stable angina. We used Bergman's minimal model to analyze the insulin response to intravenous glucose in 21 subjects: 8 patients with previous (>3 months) acute coronary syndrome but no effort-related angina; 6 patients with stable effort angina but no prior acute event; and 7 healthy controls. Diabetes mellitus, systemic hypertension, dyslipidemias, and obesity were excluded. All patients underwent coronary angiography. Insulin sensitivity, glucose effectiveness, and glucose tolerance were determined from insulin and glucose concentrations measured frequently up to 3 hours after a 0.33 g/kg intravenous glucose bolus. Patients with previous unstable angina or acute myocardial infarction had less extensive disease at angiography than patients with stable angina (p = 0.007). Both patient groups had higher basal and 180-minute insulinemia than controls (p <0.0007). However, patients with stable angina did not differ significantly from controls with regard to early and late insulinemic response to glucose. In contrast, patients with previous acute onset of ischemia had significantly greater 180-minute integrated insulinemia (p = 0.04) and reduced insulin sensitivity (p = 0.05) after the glucose challenge than did the stable angina group. These data suggest that patients with acute presentation of coronary artery disease, compared with patients with uncomplicated chronic stable angina, have an impaired insulin response to glucose despite less extensive coronary disease at angiography.

Platelet and Thrombin Activity Following Cardiac Catheterization Despite Treatment with Aspirin.

Thromboembolic complications are reported to occur in up to 0.5-2% of left cardiac catheterizations and angiographies. Activation of the hemostatic system may contribute to their onset. To prevent platelet and thrombin activity during catheterization, aspirin or systemic heparin are often used in addition to heparinized flush solutions. We investigated whether aspirin alone can prevent platelet and thrombin activity induced by catheterization in ten consecutive patients (nine males, mean 50 +/- 8 years) undergoing elective left cardiac catheterization after at least 5 days of oral aspirin (75-300 mg/d). Anticoagulant drugs were not given. Peripheral venous samples were drawn before, immediately after (time 0), and at 15, 60, and 180 minutes after the procedure for measurement of thrombin-antithrombin (TAT), prothrombin fragment 1.2 (F 1.2), fibrinopeptide A (FPA), and beta-thromboglobulin (beta-TG). TAT, F1.2, and FPA increased significantly at time 0 compared with both before and 180 minutes after the procedure (P < 0.04); beta-TG values were higher at time 0 compared with 180 minutes later (P = 0.01). TAT levels were related to those of FPA (r = 0.66; P = 0.0003), F1.2 (r = 0.35; P = 0.01), and beta-TG (r = 0.37; p = 0.04). Thus, routine left cardiac catheterization is associated with transient, systematically detectable, activation of coagulation and platelets, despite aspirin therapy. Newer antiplatelet agents may be more effective in preventing hemostatic activation induced by catheterization.

Transradial approach in the catheterization laboratory: pros/cons and suggestions for successful implementation.

In the last decade the radial access use in the catheterization laboratory has sensibly grown up worldwide. From an initial sporadic use as alternative but challenging vascular approach, radial artery is today utilized by default for percutaneous procedures in many centers. The tangible interest in the transradial approach is also testified by increasing presence of specific sessions in the main interventional meetings and by continuous development of dedicated catheters and ancillary devices by manufacturers. In this review we describe the anatomical characteristics and the technical aspects related to transradial procedure underlying its pros/cons in opposition to femoral access. We also point up practical instructions trying to resolve the main concerns related to an extensive use of radial approach in catheterization laboratory, such as increased operator's discomfort, higher radiation exposure, safety and feasibility for complex high-risk procedures.

A simple assay for platelet-mediated hemostasis in flowing whole blood (PFA-100): reproducibility and effects of sex and age.

BACKGROUND: A simple assay for platelet-mediated hemostasis in flowing blood (PFA-100) has become available. Whole blood is aspirated through the central opening of a membrane coated with platelet agonists; the time required for a platelet thrombus to occlude the opening is defined as closure time; the shorter the closure time the greater the platelet aggregability. There are limited data on the normal range of values for this test, and the effects of sex and age are not known. The aim of this study was to determine the effects of sex and age on closure time in normal volunteers and to assess the reproducibility of the test in our laboratory. METHODS: Closure time using collagen/adenosine-5'-diphosphate was measured in 62 apparently healthy individuals 35 to 75 years of age (11 men and 17 women < 55 years and 22 men and 12 women > 55 years). RESULTS: Closure time was 96.6 +/- 24 s in men and 93.1 +/- 16 s in women (p = 0.20). In the entire group, closure time did not significantly correlate with age (r = -0.17, p = 0.18). However, men < 55 years tended to have a longer closure time than men > 55 years (109.7 +/- 23 vs 90.0 +/- 22 s, p = 0.08), whereas in women closure time was similar in those younger or older than 55 years (93.1 +/- 16 vs 93.3 +/- 18 s, respectively). In 20 samples tested in duplicate, the mean closure time was 80.9 +/- 10 s on the first determination and 81.5 +/- 12 s on the second (r = 0.89, p < 0.001). There was no significant correlation between closure time and hematocrit, platelet number, mean platelet volume, or leukocyte count. CONCLUSIONS: The platelet function analyzer PFA-100 showed a good reproducibility in apparently healthy subjects. No significant difference in closure time was found between men and women, nor between subjects younger or older than 55 years, although a tendency towards shorter values was found in older compared with younger men.

Platelet aggregability in cardiac syndrome X.

AIMS: To assess platelet aggregability at rest and in response to exercise in patients with cardiac syndrome X (anginal chest pain, ST-segment depression on exercise, angiographically normal coronary arteries). METHODS AND RESULTS: We performed a symptom/sign-limited exercise test in 31 patients with syndrome X, 25 patients with coronary artery disease and 29 healthy subjects. Platelet aggregability was measured in flowing whole blood at baseline, at peak exercise, and after 30 and 120 min, as the time to occlude a collagen/adenosine diphosphate coated ring (aggregation time). Resting aggregation time was shorter in syndrome X patients (83.2+/-12 s), compared to patients with coronary disease (94.0+/-18 s, P<0.01) and to healthy subjects (96.4+/-21 s, P<0.01). With exercise, aggregation time did not change in healthy controls, decreased in patients with coronary disease (-13.8 s at peak; 95% CI, -10.2, -17.3 s;P<0.001), but increased in syndrome X (+17.4 s 30 min after exercise; 95% CI, +10.4, +24.4 s;P<0.0001). The intravenous administration of an adenosine antagonist (theophylline) prevented the exercise-induced prolongation of aggregation time in syndrome X patients (n=11), but had no effect in healthy controls (n=11). CONCLUSION: Platelet aggregability at rest was increased in syndrome X patients, compared to patients with coronary artery disease and healthy subjects. In contrast to patients with coronary disease, however, platelet aggregability was reduced by exercise. This response was prevented by theophylline, strongly suggesting the involvement of adenosine.

Ticlopidine and aspirin fail to suppress the increased platelet aggregability that follows percutaneous coronary interventions.

Previous studies indicate that percutaneous transluminal coronary angioplasty (PTCA) is associated with platelet activation. It is not well-established whether enhanced platelet aggregability after PTCA is prevented by the association of ticlopidine with aspirin. The aim of this study was to evaluate whole blood platelet aggregability before and after elective PTCA in patients with chronic stable angina receiving ticlopidine and aspirin. We studied 16 patients referred for elective PTCA, treated for > or = 72 hours with oral aspirin and ticlopidine (group 1), and 10 patients referred for diagnostic coronary angiography, treated with oral aspirin alone (group 2). An intravenous bolus of heparin was administered at the start of PTCA. In both groups, platelet aggregability was assessed at baseline and 24 hours after the procedure, using the PFA 100(R) system. This method measures the time required for flowing whole blood to occlude a collagen and adenosine diphosphate (ADP)-coated ring, shorter times indicating greater aggregability. In both groups, platelet aggregability after the procedure was significantly increased compared with baseline: 104+/-30 seconds before versus 88+/-24 seconds at 24 hours in group 1 (p=0.03) and 84+/-16 seconds before versus 69+/-14 seconds at 24 hours in group 2 (p=0.004). Group 1 patients, compared with group 2, showed a trend toward reduced aggregability at baseline (p=0.06) and significantly lower aggregability 24 hours after the procedure (p=0.03). Ticlopidine and aspirin reduce whole-blood platelet aggregability compared with aspirin alone but fail to suppress the increased aggregability that occurs 24 hours after PTCA.