Randomized, double-blind, placebo-controlled dose-ranging study of tirofiban (MK-383) platelet IIb/IIIa blockade in high risk patients undergoing coronary angioplasty

OBJECTIVES

The objectives of this double-blind, placebo-controlled, randomized dose-ranging study were 1) to examine the safety and tolerability of tirofiban (MK-383), a new nonpeptide platelet IIb/IIIa receptor antagonist, on a background of intravenous heparin and aspirin therapy; 2) to study the pharmacodynamics and pharmacokinetics of tirofiban; and 3) to evaluate the incidence of adverse cardiac outcomes (urgent repeat revascularization, myocardial infarction and death) with tirofiban versus placebo in a high risk subset of patients undergoing coronary angioplasty.

BACKGROUND

Abrupt vessel closure complicates 4% to 8% of angioplasty procedures. Recent data have suggested that agents that antagonize the platelet glycoprotein IIb/IIIa receptor may reduce the incidence of adverse ischemic outcomes after coronary angioplasty.

METHODS

Seventy-three patients received tirofiban in three sequential dose panels and 20 patients received placebo. Patients within each panel were randomized to receive either tirofiban or placebo in a 3:1 randomization design. Bolus doses of 5, 10 and 10 microg/kg and continuous infusion (16 to 24 h) doses of 0.05, 0.10 and 0.15 microg/kg per min were administered in panels I, II and III, respectively. Patients received concomitant heparin and aspirin for the angioplasty procedure. Data on patients receiving placebo (heparin and aspirin only) were pooled across panels for comparisons. The pharmacodynamic effect of tirofiban on ex vivo platelet aggregation to 5 micromol/liter adenosine diphosphate (ADP) and bleeding times were measured. Clinical outcomes were assessed in all patients, but the power to detect clinically meaningful differences (a one-third reduction in clinical events) between groups was limited (5%).

RESULTS

Tirofiban was associated with a dose-dependent inhibition of ex vivo ADP-mediated platelet aggregation that was sustained during intravenous infusion and resolved rapidly after drug cessation. Adverse bleeding events, largely related to vascular access site hemorrhage, were slightly increased at the highest dose. Adverse clinical outcomes were infrequent in all patients and were not different among the small number of patients within each group.

CONCLUSIONS

This study establishes a rational and generally well tolerated dosing regimen for administration of tirofiban as adjunctive therapy in high risk angioplasty patients. The impact of tirofiban on adverse clinical outcomes after angioplasty awaits definition by a larger clinical trial.

Adaptation mechanisms during myocardial ischemia in chronic unstable angina pectoris

Unstable angina with a clinical duration of < 2 months is characterized angiographically by a high incidence of complex lesions. Some patients have ischemic rest pain syndromes of longer duration. Thus, we retrospectively analyzed, in blinded fashion, the clinical and angiographic findings in 52 patients with unstable angina of < 2 months' duration (group A), and compared the results with those of 32 patients with unstable angina of > 6 months' duration (group B). Group B had a greater number of diseased vessels and better collateral circulation, but had fewer eccentric lesions. There were no differences in age, left ventricular function, or history of prior myocardial infarction. Thus, chronic unstable angina is associated with more extensive coronary disease than unstable angina of shorter duration. The role of different anatomic substrata and collateral circulation is discussed.

Late thrombolytic therapy preserves left ventricular function in patients with collateralized total coronary occlusion: primary end point findings of the Second Mount Sinai-New York University Reperfusion Trial

The change in left ventricular ejection fraction from preintervention to predischarge was prospectively assessed in 393 patients with acute myocardial infarction. Within 12 h of symptom onset (mean 6.3 +/- 2.7 h), patients were randomly assigned to a double-blind intracoronary infusion of streptokinase, nitroglycerin, both streptokinase and nitroglycerin or conventional therapy without acute cardiac catheterization. Treatment effects were also assessed in prospectively defined angiographic subsets. There was a significant interaction between streptokinase and nitroglycerin (p less than 0.01), resulting in an increase in ejection fraction of 3.9 percentage units in the combined treatment arm (p less than 0.001). Patients with collateral flow to a totally obstructed infarct-related artery showed a significant improvement over those without collateral flow in the streptokinase (5.4 +/- 2.5%) and streptokinase-nitroglycerin (10.6 +/- 2.7%) arms, but not in the nitroglycerin arm. Time to treatment did not influence the change in ejection fraction. In patients with initial subtotal occlusion, thrombolytic therapy was of no short-term benefit because ejection fraction increased by 6% in all three intervention arms. These findings indicate that relatively late thrombolytic therapy results in significant myocardial salvage in those patients with collateralized total coronary occlusion. This benefit is potentiated by concomitant nitroglycerin therapy.

Balloon valvuloplasty in adult aortic stenosis: determinants of clinical outcome

STUDY OBJECTIVE

To determine the clinical variables affecting outcome after balloon aortic valvuloplasty.

DESIGN

Longitudinal follow-up of consecutive case series.

PATIENTS

Consecutive sample of 36 patients with severe calcific aortic stenosis, and without active infection or left ventricular mural thrombus.

INTERVENTIONS

Percutaneous transluminal dilatation of the aortic valve until the peak gradient was reduced by 50% or a maximal balloon size was used. Hemodynamic measurements taken before and after dilatation.

MEASUREMENTS AND MAIN RESULTS

Thirty-three patients had a successful dilatation. Eighty-nine percent (95% confidence interval [CI]. 74% to 97%) improved symptomatically at 2 weeks, but by 26 weeks only 56% (CI, 35% to 76%) remained improved (P = 0.0078). Mortality rates were high at 8 (9%) and 26 (28%) weeks. Predictors of adverse events included left ventricular ejection fraction (P = 0.04, r = 0.46), pulmonary artery systolic pressure (P = 0.048, r = 0.65), pulmonary vascular resistance (P = 0.008, r = 0.69), and right ventricular end-diastolic pressure (P = 0.009, r = 0.43) at 8 weeks and all these factors except left ventricular ejection fraction at 26 weeks. These clinical outcomes were unrelated to other cardiac or pulmonary diseases.

CONCLUSIONS

Symptomatic improvement is only temporary in many patients undergoing balloon aortic valvuloplasty, and the mortality rate in the mid-term follow-up period is high. Valve surgery remains the treatment of choice for aortic stenosis in the adult.

Restrictive-type hemodynamics following valve surgery for rheumatic heart disease

Over a six-year period three patients with rheumatic valvular disease presented with congestive heart failure due to abnormalities in myocardial diastolic function. Each patient previously had been operated for mitral stenosis; one patient had additional aortic valve replacement for aortic insufficiency. The mean time for the development of symptoms following surgery was 4.7 years. In all patients, left ventricular systolic function was normal (radionuclide or angiographic ejection fraction greater than 0.50). Abnormalities in diastolic function involved the left ventricle in all patients. Biopsy material from right (one patient) and left (one patient) ventricles was nonspecific in its histologic appearance. Other disease processes, such as constrictive pericarditis and diabetic cardiomyopathy were considered to be clinically unimportant in these patients. Restrictive-type hemodynamics in patients with postoperative rheumatic heart disease may comprise a newly recognized entity.

Acute coronary hemodynamic response to cigarette smoking in patients with coronary artery disease

The acute changes in coronary blood flow and coronary resistance that occur in response to cigarette smoking have not been accurately determined. To define the factors that affect this response, coronary sinus blood flow was measured in 16 patients (group I) with coronary artery disease and in 6 patients (group II) without angiographically detectable coronary disease. Seven patients (group IA) had severe (greater than or equal to 75%) proximal left coronary lesions and nine patients (group IB) had significant distal lesions with 50% or less proximal stenoses. Group I had a smaller overall increase (increases 1.6 +/- 5.3%) in coronary sinus blood flow than did group II (increases 7.7 +/- 6.1%) (p less than 0.05). Coronary resistance increased overall (increases 2.7 +/- 5.3%) in group I but decreased (decreases 2.4 +/- 3.4%) in group II (p less than 0.05). Patients in group IA had a highly significant increase in coronary resistance as compared with group IB (increases 7.0 +/- 4.2% versus decreases 0.9 +/- 2.6%) (p less than 0.001). Coronary sinus flow tended to decrease (decreases 1.2 +/- 4.6%) in group IA but to increase (increases 3.8 +/- 5.1%) in group IB (p = 0.06). It is concluded that smoking increases coronary resistance in patients with coronary artery disease. A greater impact is observed in patients with a severe proximal stenosis than in those with a distal stenosis. It is proposed that smoking increases coronary artery tone at the site of the stenosis, limiting the coronary flow response proportionally to the size of the affected vascular bed.

Significance of contrast enhancement in cranial computerized tomography after subarachnoid hemorrhage

Eighty patients with subarachnoid hemorrhage underwent computerized tomography (CT) scanning before and after administration of Conray contrast medium. Abnormal enhancement was seen in visual evaluation of the CT scans in 26 cases, in the regions bordering the subarachnoid spaces. Abnormal enhancement was associated with a poor clinical condition, angiographic spasm, and a poor outcome. Measurements of absorption values in the thalamus revealed significant increases in density after contrast enhancement in those patients whose scans showed abnormal enhancement in the regions bordering the subarachnoid spaces on visual evaluation. The authors suggest that the abnormal enhancement is parenchymal, in the gyri, and is not "subarachnoid." They suggest that it is due to gyral hyperemia or extravasation of contrast material into the cortex resulting from breakdown of the blood-brain barrier, or a combination of both factors.

Coronary thrombosis in the absence of angiographically-evident obstructive coronary disease

A 31-year-old man with an acute myocardial infarction underwent intracoronary thrombolysis with streptokinase. Post-thrombolytic angiography revealed no underlying obstructive coronary disease. This particular syndrome of a documented thrombus in a normal vessel causing infarction has not previously been described. Such a sequence may explain the occurrence of myocardial infarction in some patients with normal coronary arteries. The mechanism by which thrombus occurs in an angiographically-normal coronary artery is at present undefined.

Angina pectoris before and after myocardial infarction. Angiographic correlations

Clinical, hemodynamic, and angiographic data were examined in 97 consecutive patients who underwent catheterization within two years of documented acute transmural myocardial infarction. The patients were divided according to the absence or presence of angina pectoris prior to myocardial infarction (groups 1 and 2). Group 1 had more females, was younger, and had a greater prevalence of one-vessel coronary artery disease. Of the patients surviving the myocardial infarction until hospital discharge, group 1 had fewer cases of postinfarction angina pectoris. The following were not statistically different for the two groups: mean time from infarction to catheterization, location of infarction, heart failure, coronary risk factors, mean left ventricular end-diastolic pressure, and mean ejection fraction. The angiographic significance of angina following infarction was analyzed in the 94 survivors. Patients with angina after infarction had a greater prevalence of two- and three-vessel coronary artery disease compared with patients without angina following infarction. Group 1 patients who had developed angina after infarction also had a greater prevalence of two- and three-vessel disease than patients who had no postinfarction angina. One-vessel disease was found in 82 percent of patients who had no angina before and after infarction. Infarction as the first manifestation of coronary artery disease (group 1) is often associated with one-vessel disease, especially if angina does not appear after infraction. Angina before or after infarction suggests two- and three-vessel disease.

Coronary flow studies in patients with left ventricular hypertrophy of the hypertensive type. Evidence for an impaired coronary vascular reserve

Increased myocardial blood flow occurs in ventricular hypertrophy, but flow per 100 grams of myocardium remains normal. The increase in flow may be obtained at the expense of the existing coronary vascular reserve or by an increase in the vascular bed. The coronary vascular reserve was studied by analyzing the hyperemic reaction to selective injection of contrast agent into the coronary arteries in 25 patients: a control group (9 patients) with chest pain syndrome, normal coronary arteries and a normal left ventricle (Group I) and 16 patients with aortic stenosis, left ventricular hypertrophy and normal coronary arteries (Group II). The hyperemic response in Groups I and II was 73.3 +/- 2.2 and 65.8 +/- 9.1 percent, respectively (difference not significant). Group II was subdivided into two groups: Group IIA had five patients with a left ventricular mass of less than 200 g (mean 158.8 +/- 25.9); this group had a hyperemic response of 102.3 +/- 9.9 percent. Group IIB had 11 patients with a left ventricular mass of more than 200 g (mean 308.9 +/- 22.5) and a hyperemic response of 49.27 +/- 10.42 percent. The hyperemic response was correlated with the diastolic left ventricular-aortic gradient (r = +0.64, p less than 0.001), left ventricular mass (r = -0.51, p less than 0.01) and aortic diastolic pressure (r = +0.636, p less than 0.001). Group I had a left ventricular mass similar to that of Group IIA (124.9 +/- 9 and 158.8 +/- 26 g, respectively) but a lower hyperemic response (73.3 +/- 2 and 102.3 +/- 10 percent, respectively). These data suggest that severe left ventricular hypertrophy is associated with a reduction in coronary vascular reserve; it is speculated that this decrease in the vascular reserve capacity may be related to the ischemic component of hypertrophic heart disease.

Coronary artery spasm and perioperative cardiac arrest

There has been increasing interest in coronary artery spasm as etiopathogenic mechanism for various syndromes associated with myocardial ischemia. A case with documented organic coronary artery disease is presented, in which coronary artery spasm was the probable cause of intraoperative and early postoperative cardiac arrest. We recommend that coronary spasm be considered in the differential diagnosis of perioperative cardiac arrest.

Computerized tomography scanning appearances of intracranial meningiomas. An attempt to predict the histological features

✓ The computerized tomography (CT) scans of 102 patients with meningiomas confirmed at operation and histologically were reviewed, and the features displayed by the tumors were correlated with their histology. There were 54 transitional, 17 fibroblastic, 13 mixed transitional and fibroblastic, 10 angioblastic, and eight syncytial meningiomas. It was found that each of these meningioma variants exhibited common CT features that could be helpful in predicting the probable histology. These common features were: visible calcium aggregates, degree of surrounding edema, tumor density before and after contrast medium enhancement, homogeneity, and definition of outline. Visible calcium aggregates pointed to a diagnosis of either transitional or fibroblastic meningioma. None of the angioblastic or syncytial variants exhibited this feature. Most of the tumors were surrounded by edema of varying degrees (92%) but this was not considered to be a specific feature except perhaps in the fibroblastic type where the edema was almost invariably of moderate degree. Tumor attenuation values unenhanced by contrast medium were also nonspecific but in enhanced scans a homogeneous density distribution pointed to the tumor being most probably of the transitional type. The angioblastic and syncytial variants showed a marked tendency to exhibit low-density non-enhancing “cystic” areas or poorly defined, irregular tumor margins or fringes. All of the fibroblastic, transitional, or mixed fibroblastic and transitional variants were well defined with more or less regular shapes. The presence of marked edema, absence of visible calcium aggregates, non-homogeneous contrast enhancement with non-enhancing “cystic” components and poorly defined irregular borders point to aggressive or invasive characteristics more commonly found in the angioblastic and syncytial variants.

The double contrast barium enema: improvements to lateral decubitus views including the use of a wedge filter

The prognostic importance of early detection of colonic carcinoma is emphasised and the contribution of an accurate barium enema technique is stressed. Horizontal beam lateral decubitus films are routine in double contrast barium enemas, and it is still common practice in many departments to support the cassette for these views either in the bucky tray or with sandbags. The lateral decubitus views of 100 patients using these methods of cassette support were reviewed. A large number of the films (67%) were technically so unsatisfactory due to unilateral under- or over-penetration that they did not provide acceptable visualisation of the colon. The cause of these technical faults, and the methods by which they may be overcome, are described. In addition, a wedge filter was designed to reduce the absorption by dependent soft tissues in obese patients.

A quantitative study of the EMI values obtained for normal brain cerebral infarction and certain tumours

A quantitative study has been made of the EMI numbers of normal brain, cerebral infarction and certain tumours. The scans were recorded on magnetic tape and analysed using a minicomuter linked to a graphic display unit. This system not only yielded 16 grey scales compared with the ten currently available, but was programmed to allow selected regions of the scans to be outlined. From these regions the computer calculated the area, the mean EMI number and its standard deviation. It was found that in 15 normal brain scans, the EMI values obtained for normal frontal and temporal lobes were similar, but that the values for the basal ganglia and occipital lobes were significantly different from the first two regions and from each other. Ten cases of cerebral infarction and 30 cases of cerebral tumour were analysed, and it was shown that analysing representative areas was more informative than surveying the whole lesion. Whilst only half of the scans of brain tumours had a significantly altered EMI number compared with that of normal brain, enhancement of tumour density with sodium iothalamate revealed a consistent and significant elevation of the EMI number for all tumours. In particular, the value for enhanced meningiomas was almost double and malignant tumours more than a third larger than normal brain. It was not possible to differentiate quantitatively between astrocytomas and metastases.

Computerized axial tomography: estimation of spatial and density resolution capability

The spatial and density resolution capability of the EMI-Scanner device for computerized axial tomography has been determined in vitro. For density differences greater than +/-1 per cent the spatial resolution is 6 X 6 mm. For density differences of 3 per cent and greater the resolution is 3 X 3 mm. Density resolution is at least +/-1 per cent for objects greater than 1 cm. Preliminary data on in vitro measurement of X-ray linear attenuation coefficients in tissue biopsies and standard solutions are given, together with the early results of enhancement of tissue density differences in vivo. Implications of this new technique for an in vivo neuropathology are suggested.