Active or passive bio-coating: does it matters in extracorporeal circulation?

BACKGROUND: Two types of surface coating for cardiopulmonary bypass (CPB) are used: bioactive (heparin, nitric oxide) and biopassive (albumin, polyethyleneoxide (PEO), phosphorylcholine). When haemocompatible coatings are combined with the separation of pleuro-pericardial aspiration, attenuation of both the coagulation and complement cascades, as well as better platelet preservation, has been demonstrated. This study wants to investigate if the combination of a bioactive with a biopassive coating (unfractionated heparin embedded in a phosphorylcholine matrix) combines the beneficial effects of both approaches. MATERIALS AND METHODS: Thirty patients undergoing elective CABG were prospectively randomized into two groups of 15 patients. The sole exclusion criterion was an ejection fraction of less than 40%. In the control group (PC), the whole CPB circuit was coated with phosphorylcholine (PC). In the study group (XPC), unfractionated heparin was embedded in the PC matrix of the oxygenator and arterial line filter. RESULTS: No differences were found for haemolytic index, thrombin-anti-thrombin complex (TAT), IL-6, IL-10 and blood loss. PF4 plasma concentration increased from 27.6±22.0 IU/mL to 165.7±43.9 IU/mL (p<0.001) at 15 minutes of CPB in the PC and from 16.0±9.7 IU/mL to 150.9 ± 61.3 IU/mL (p<0.001) in the XPC group. Terminal complement complex (TCC) increased over time in both groups until the end of CPB (Figure 2A). Within each group, TCC generation was statistically significantly higher after the release of the aortic cross-clamp (p<0.001) and at the end of CPB (p<0.001). Total TCC generation was statistically significantly higher in the XPC group compared to the PC group (p=0.026). The difference was statistically significant after the release of the aortic cross-clamp (p=0.005) and at the end of CPB (p=0.001). CONCLUSIONS: Based on our results, there is no additional benefit in combining phosphorylcholine with unfractionated heparin in elective patients undergoing coronary artery bypass grafting (CABG). Massive haemodilution leads to enhanced complement activation.

Percutaneous transcatheter closure of an aorto-cardiac fistula in a six-year-old Warmblood mare with atrial fibrillation.

This report describes a rare case of an aorto-cardiac fistula in a six-year-old French Warmblood mare presented with atrial fibrillation, decreased performance, ventral oedema, bounding arterial pulsation and pathological jugular venous pulse. A 2.7-cm-diameter fistula connected the right aortic sinus of Valsalva to the right atrium. Atrial fibrillation was likely due to volume overload of the right heart due to left-to-right shunting. The horse was treated by percutaneous transcatheter closure of the fistula delivered under general anaesthesia using a transarterial approach. The operation was initially successful, and clinical signs of congestive heart failure improved immediately. However, the device dislodged six days after procedure, and the general condition of the horse deteriorated quickly. A second closure attempt to deliver the occluder using a transvenous approach in the standing horse failed, and the horse was eventually euthanized. Procedural aspects and several possible risk factors for device dislodgement are discussed.

Clinical and angiographic factors associated with progression of coronary artery disease.

To characterize the clinical and angiographic factors associated with progression of coronary atherosclerosis, 313 consecutive medically treated patients who had had two coronary arteriograms 3 to 119 months (mean 39 +/- 25) apart were studied. One hundred eighty-one patients underwent recatheterization for stable angina, 52 for unstable angina and 80 for various other reasons. In addition to the conventional angiographic features present at the first angiographic study (number of diseased vessels 1.5 +/- 0.8, ejection fraction 59 +/- 11%), an extent score was defined based on the number of coronary segments with 5 to 75% narrowings from a 15 segment coding system. Multivariate logistic regression identified four independent predictors of progression of coronary artery disease: the interval between studies (p less than 0.0001), unstable angina (p less than 0.0001), a high extent score (p = 0.0001) and young age (p = 0.0026). In a subset of 74 patients aged 50 years or younger with, at the time of the first evaluation, an extent score of 4 or more, the probability of progression between 2 and 4 years and after 4 years was, respectively, 80 and 90% compared with 50% for the other patients. Risk stratification for progression of coronary artery disease can thus be obtained.

Preinfarction angina protects against out-of-hospital ventricular fibrillation in patients with acute occlusion of the left coronary artery.

OBJECTIVES: The goal of this study was to evaluate the effect of preconditioning on out-of-hospital ventricular fibrillation (VF) in patients with acute myocardial infarction (AMI). BACKGROUND: More than half of the deaths associated with AMI occur out of the hospital and within 1 h of symptom onset. In humans, preinfarction angina (PA), which can serve as a surrogate marker for preconditioning, reduces infarct size, but the protective effect against out-of-hospital VF has not been investigated. METHODS: Preinfarction angina status and acute coronary angiographic findings of 72 consecutive patients with AMI complicated by out-of-hospital VF were compared with 144 matched controls without this complication. RESULTS: Preinfarction angina is associated with a lower risk for VF (odds ratio [OR]: 0.40, 95% confidence interval [CI]: 0.18 to 0.88). In patients with acute occlusion of the left coronary artery (LCA) (n = 136), the risk reduction is pronounced (OR: 0.25, 95% CI: 0.10 to 0.66), whereas, in patients with acute occlusion of the right coronary artery (RCA) (n = 67), the protective effect of PA on VF was not observed (OR: 2.25, 95% CI: 0.45 to 11.22). Subgroup and multivariate analyses show that the protective effect is independent of cardiovascular risk factors, preinfarction treatment with beta-adrenergic blocking agents or aspirin, the presence of collaterals or residual antegrade flow or the extent of coronary artery disease. CONCLUSIONS: Preinfarction angina protects against out-of-hospital VF in patients with acute occlusion of the LCA. This protection is independent of risk factors or coronary anatomy. A larger study is needed to examine the apparently different effect in patients with acute occlusion of the RCA.

A randomized study comparing propranolol and diltiazem in the treatment of unstable angina.

One hundred consecutive patients hospitalized in the coronary care unit for unstable angina, excluding patients with Prinzmetal's variant angina, were randomized within 24 hours of admission to treatment with diltiazem (50 patients) or propranolol (50 patients). Also excluded were patients with previous coronary artery bypass surgery and those receiving a beta-receptor blocking agent at the time of hospital admission. Left ventricular function and the extent of coronary artery disease were similar in the two groups. During the hospital stay, the number of chest pain episodes decreased from a mean (+/- SD) of 0.75 +/- 0.1 per patient per day to 0.26 +/- 0.07 (p less than 0.05) with diltiazem and 0.29 +/- 0.1 (p less than 0.05) with propranolol therapy. The circadian distribution of chest pain episodes was affected similarly. After 1 month, 14 of the patients treated with diltiazem were symptom-free compared with 13 treated with propranolol. At a mean follow-up time of 5.1 months (range 1 to 15), death had occurred in two patients in each group and myocardial infarction in five diltiazem- and four propranolol-treated patients (difference not significant). Coronary artery bypass surgery had been performed in 21 diltiazem- and 19 propranolol-treated patients (difference not significant). Only 15 patients were symptom-free, 9 treated with diltiazem and 6 with propranolol. This similar result observed with the two forms of treatment suggests that coronary artery spasm may not be the main factor involved in unstable angina when Prinzmetal's variant angina is excluded. It also suggests that diltiazem can be used as an alternative to the usual treatment with beta-receptor blocking drugs.

Out-of-hospital ventricular fibrillation in patients with acute myocardial infarction: coronary angiographic determinants.

OBJECTIVES: The study intended to compare the acute coronary anatomy of patients with acute myocardial infarction (AMI) complicated by out-of-hospital ventricular fibrillation (VF) versus patients with AMI without this complication. BACKGROUND: More than half of the deaths associated with AMI occur out of the hospital and within 1 h of symptom onset. The angiographic determinants of out-of-hospital VF in patients with AMI have not been investigated in detail. METHODS: Acute coronary angiographic findings of 72 consecutive patients with AMI complicated by out-of-hospital VF were compared with findings from 144 matched patients with AMI without this complication. RESULTS: Patients with an acute occlusion of the left anterior descending coronary artery (LAD) or left circumflex coronary artery (LCx) had a higher risk for out-of-hospital VF compared with patients with an acute occlusion of the right coronary artery (RCA) (odds ratio and 95% confidence interval, respectively, 4.82 [2.35 to 9.92] and 4.92 [2.34 to 10.39]). With regard to extent of coronary artery disease (CAD), the location of the culprit lesion in the coronary arteries (proximal vs. mid or distal), the flow in the infarct related artery (IRA), the presence or absence of collaterals to the IRA and chronic occlusions, there were no differences between the two groups. CONCLUSIONS: Acute myocardial infarction due to occlusion in the left coronary artery (LCA) is associated with greater risk for out-of-hospital VF compared to the RCA. The location of occlusion within LCA (LAD, LCx, proximal or distal), amount of myocardium at risk for necrosis and extent of CAD are not related to out-of-hospital VF.

Fibrinogen and C-reactive protein on admission as markers of final infarct size after primary angioplasty for acute myocardial infarction.

BACKGROUND: In acute myocardial infarction (AMI) treated conservatively or with thrombolysis, marked increases of C-reactive protein (CRP) and fibrinogen have been observed. No data are however available concerning a possible relation between CRP and fibrinogen levels on admission and markers of infarct size after obtaining thrombolysis in myocardial infarction (TIMI) flow III by primary angioplasty. METHODS: We studied 34 patients with a first AMI (29 men, mean age 54+/-11 years) who were treated with primary angioplasty (TIMI flow III in all patients, no concomitant treatment with glycoprotein IIb-IIIa antagonists) within 6 h of onset of pain. CRP and fibrinogen levels on admission were determined and related to the following markers of infarct size: peak creatine kinase MB (CKMB) levels, radionuclide left ventricular ejection fraction (LVEF) at discharge and thallium-201 single-photon emission computed tomography (SPECT) infarct size at 1 month. RESULTS: Median CRP levels were 0.4 mg/dl (range 0.09-3 mg/dl), median fibrinogen levels 412 mg/dl (range 198-679 mg/dl), mean CKMB was 178+/-151 U/l, mean LVEF 52+/-8% and mean thallium-201 infarct size 7+/-6%. Although CRP levels were related to fibrinogen levels on admission (r=0.56, P=0.002), only fibrinogen levels were related to markers of infarct size (r=0.58, P=0.001 for CKMB, r=-0.44, P=0.01 for LVEF and r=0.64, P=0.001 for thallium-201 infarct size). No relation was found between CRP or fibrinogen levels on admission and the extent of coronary artery disease or the myocardial area at risk. In multiple regression analysis, the relation between fibrinogen and markers of infarct size was independent of CRP levels and the duration of pain on admission. CONCLUSIONS: These findings indicate a relation between fibrinogen levels on admission and myocardial infarct size in patients treated with primary angioplasty for AMI. This relation seems to be independent of CRP levels and the duration of pain on admission. If confirmed in larger patient populations, fibrinogen levels on admission could have an important value for risk stratification and more aggressive reduction of infarct size in patients who are treated with primary angioplasty.

Low-dose dobutamine stress echocardiography in children and young adults.

Dobutamine stress echocardiography has become widely accepted in the evaluation of adult patients with coronary heart disease. We wanted to assess the feasibility and the physiologic responses of stress echocardiography at low doses of dobutamine in a population of normal children and adults. Once achieved, we submitted a group of post-anthracycline patients to the test to assess the sensitivity of low-dose dobutamine stress echocardiography in the detection of cardiac dysfunction. Thirty-two healthy children and young adults (19 male and 13 female subjects, median age 15 years [range 6 to 26]) were studied. After the initial study of normal subjects, we submitted a cohort of 39 patients (18 female and 21 male, aged 6 to 25 years), who completed anthracycline chemotherapy, to the same protocol. Dobutamine was infused at rates of 0.5 to 2.5 and 5 microg/kg/min and echocardiographic measurements were obtained at rest and at the end of each stage. The test could be completed in 100% of the subjects without major complications. Statistically significant differences between resting echocardiographic values of systolic and diastolic function and values at 2.5 and 5 microg/kg/min of dobutamine were found. Moreover, dobutamine revealed or enhanced differences between normal subjects and the post-anthracycline patients. Thus, low-dose dobutamine stress echocardiography is feasible and safe in older children. The test is very sensitive for the detection of subclinical cardiac dysfunction in post-anthracycline patients and could possibly assess functional myocardial reserve.

Factors associated with progression of coronary artery disease in patients with normal or minimally narrowed coronary arteries.

This study was performed to identify the subset of patients with normal or with minimal (49% or less) stenosis of the coronary vessels who may be prone to progressive coronary artery disease (CAD). Data were collected from 51 patients (19 men, 32 women, mean age 48 years) with normal coronary arteries (20 patients) or with minimal narrowing (31 patients) on a first angiogram, who underwent repeat catheterization 4 to 120 months later (mean 52) because of persistent chest pain. Three classic lifestyle-related risk factors (systemic hypertension, cigarette smoking status and hypercholesterolemia) were noted; the number of diseased segments on the first angiogram was counted according to a 15-segment coding system. Progression of CAD required the consensus of 3 observers on a 30% or greater decrease in luminal diameter. Progression was recorded in 16 of 31 patients with minimal CAD and in 3 of 20 patients with normal coronary arteries (p less than 0.01). By multivariate logistic regression, progression was predicted by (1) number of diseased segments (p = 0.001), (2) age (p less than 0.01), (3) smoking status (p less than 0.05) and (4) initial cholesterol level (p less than 0.05). Using the probability computed by the logistic model, we could separate the 51 patients in groups with low (0 of 18), medium (9 of 23) and high (10 of 10) risk of progression. Thus, patients with normal or minimally narrowed coronary arteries at angiography form a heterogeneous population including both normal or borderline subjects and patients with CAD at its early stage. The latter condition was associated with presence of risk factors and to the angiographic extent of the disease.

Clinical and angiographic predictors of new total coronary occlusion in coronary artery disease: analysis of 313 nonoperated patients.

A new coronary artery occlusion was found in 98 of 313 consecutive patients (31%) with coronary artery disease treated medically who underwent catheterization twice, 39 +/- 25 months apart. Multivariate logistic regression displayed 8 independent predictors of new occlusion. Four were available at the time of the second angiogram: the interval between the 2 studies (p = 0.005), a decrease in ejection fraction (p less than 0.01), the appearance of bundle branch block (p less than 0.01), and an interim myocardial infarction (p less than 0.05). Four other predictors were found at the time of the first angiogram: 2 angiographic characteristics, 1 related to the severity (presence of an 80% or greater luminal diameter narrowing of an artery supplying a non-akinetic left ventricular segment [p less than 0.005]) and 1 to the extent (count of the lesions narrowed 75% or less in luminal diameter in a 15-segment coding system [p less than 0.05]) of coronary artery disease, and 2 risk factors: smoking status (p less than 0.05) and male sex (p less than 0.05). The 140 male smokers with at least 80% diameter stenosis or at least 4 segments with moderate (75% or less) stenosis were at a higher risk of occlusion than the 173 other patients after intervals of less than 2 years (13 of 53 vs 7 of 74, p less than 0.01), 2 to 4 years (23 of 40 vs 10 of 47, p less than 0.005) and more than 4 years (27 of 47 vs 18 of 54, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The Selvester 32-point QRS score for evaluation of myocardial infarct size after primary coronary angioplasty.

In patients treated successfully with primary angioplasty for a first myocardial infarction, the Selvester 32-point score correlates well with infarct size measured with quantitative thallium-201 perfusion imaging. Therefore, it is a useful parameter for infarct sizing, particularly in patients with anterior infarction or reduced ejection fraction at discharge.

Prognostic significance of progression of coronary artery disease.

Angiographically documented coronary artery disease (CAD) can progress. Although progression itself is frequently recognized in patients who have undergone repeat cardiac catheterization, its prognostic significance remains unclear. To evaluate the influence of progression on survival, 313 patients with CAD who underwent catheterization twice (39 +/- 25 months apart) were followed for 3 to 129 months (mean 41 +/- 30) after the second angiogram. At the time of the second angiogram, 21, 91, 113 and 88 patients had 0-, 1-, 2- and 3-vessel CAD, respectively. The mean ejection fraction (EF) of the group was 55 +/- 13%. Progression was noted in 139 patients (44%). Of the 313 patients, 33 died and 39 had acute myocardial infarction (AMI) during follow-up. Four-year survival was estimated at 94% and 83% in the nonprogression and progression groups, respectively. Progression was predictive of survival by (univariate) long-rank test (p less than 0.01), but only EF (p less than 0.001), number of diseased vessels (p less than 0.01) and percent stenosis in the left main coronary artery (p less than 0.05) were independently significant by (multivariate) Cox regression analysis. Four-year survival without AMI was 89% and 73% in the nonprogression and progression groups, respectively. Progression was related to survival without AMI (p less than 0.001) by log-rank test. Cox regression analysis provided 3 independent predictors of survival without AMI: number of diseased vessels (p less than 0.01), progression (p less than 0.01), relative risk = 2.28) and EF (p less than 0.01). Results were similar when analyzing only the 39 AMIs.(ABSTRACT TRUNCATED AT 250 WORDS)

Recanalization of total coronary occlusions using a laser guidewire (the European TOTAL Surveillance Study).

The success rates of coronary angioplasty for the treatment of chronic total occlusions are less favorable than for coronary stenosis. Therefore, a new laser guidewire (LW) was designed to facilitate the crossing of chronic total occlusions. We report on the results of a European multicenter surveillance study, evaluating the laser guidewire performance. Between May 1994 and July 1996, 345 patients (age 59 +/- 10 years, 291 men) with chronic total occlusions were enrolled in 28 European centers. The median age of occlusion was 29 weeks (range 2 to 884), the occlusion length 19 +/- 10 mm. LW recanalization was successful in 205 patients (59%/). LW perforation occurred in 73 patients (21%), with hemodynamic consequences in 4 (1%). There were no deaths, emergency coronary artery bypass graft surgery, or Q-wave myocardial infarctions. In a multivariate regression analysis an occlusion age of <40 weeks (p = 0.001, RR = 1.34) and an occlusion length <30 mm (p = 0.01, RR = 1.59) were independent predictors of success. Results indicate that the LW is an effective and safe tool in the treatment of chronic total occlusion refractory to conventional guidewires.

Assessment of left ventricular function in a randomised study of intravenous anisoylated plasminogen streptokinase activator complex versus heparin in acute myocardial infarction. Preliminary results of the European Multicentre Study (Belgian Centres).

Patients admitted within 4 hours of the onset of chest pain suggestive of acute myocardial infarction were randomised to either intravenous anisoylated plasminogen streptokinase activator complex (APSAC) 30U or heparin 5000U (44 vs 38 patients). Angiograms were obtained between days 10 and 15 after admission. Late coronary patency was recorded in a significantly higher proportion of patients in the APSAC group (79% vs 42%, p less than 0.001). The global ejection fraction showed only a favourable trend: 55.3 +/- 12% for the APSAC group vs 54.1 +/- 13.1% for the heparin group; this trend was only observed in the inferior infarction group. Regional wall motion analysis did not show any significant difference between treatment groups.

Calcium antagonists. Clinical use in the treatment of angina.

Angina pectoris results from an imbalance between the oxygen supply and the oxygen needs of the myocardium. While the classic form of angina is usually caused by demands exceeding supply, a primary and transient decrease in coronary blood flow is more and more often recognised as an aetiological factor of myocardial ischaemia. Calcium antagonists, although new in cardiovascular therapeutics, are already recognised as the treatment of choice for some forms of angina and as useful therapeutic adjuncts in others. Few contraindications to their use exist. They are potent vasodilators and they can prevent the occurrence of coronary artery spasm responsible for the Prinzmetal's variant form of angina. They can also reduce coronary artery tone, which if high, can compromise flow through a narrowed coronary artery. Nifedipine, diltiazem and verapamil can also influence the various determinants of myocardial oxygen consumption to reduce myocardial oxygen needs. Their effects on heart rate, blood pressure and on the inotropic state of the left ventricle is, in vivo, the balance between their direct effects on the vascular wall and myocardial muscular cells and their indirect effects represented by the reflex physiological responses. Significant variations in these effects exist between the 3 calcium antagonists such that treatment can be individualised to a particular patient's needs. Precautions with their use as well as most of their side effects can be understood from a knowledge of their direct and indirect properties. Other pharmacological effects of these drugs include a regional redistribution of coronary blood flow, cardioprotection, delay in cell death and possibly in the progression of atherosclerosis. The clinical significance of these properties remains to be investigated.

Tissue factor as the main activator of the coagulation system during cardiopulmonary bypass.

OBJECTIVE: This study investigates the influence of foreign material and blood aspirated from nonvascular structures on activation of coagulation, hemolysis, and blood loss. METHODS: The series comprises 3 randomized groups (groups C, S, and S+P) of 10 patients undergoing routine coronary artery bypass grafting with cardiopulmonary bypass. In group C, the control group, all aspirated blood was returned into the circulation. In group S suction blood was discarded, whereas group S+P was identical to group S, with surfaces coated with phosphorylcholine. Plasma concentrations of beta-thromboglobulin, thrombin generation, haptoglobin, and free hemoglobin, as well as blood loss, were measured. RESULTS: A steady increase in free plasma hemoglobin, as well as an increased generation of thrombin, was noticed in group C. Moreover, a close correlation (r = 0.916) between the generation of thrombin and its inhibition (thrombin-antithrombin complexes) was observed. Platelets were clearly activated in group C and, to a lesser extent, in group S. In contrast, platelet activation in group S+P was negligible, resulting in a 30% decrease in blood loss (P =.05). CONCLUSIONS: Aspirated blood contaminated by tissue contact is the most important activator of the coagulation system and the principal cause of hemolysis during cardiopulmonary bypass. Contact with a foreign surface is not a main variable in the procoagulant effect of bypass. Mimicking the outer cell membrane structure resulted in decreased platelet activation and decreased blood loss.

Tricuspid valve replacement: postoperative and long-term results.

A series of 146 consecutive patients who underwent tricuspid valve replacement at the University Brugmann Hospital between 1967 and 1987 was reviewed. Mean age at operation was 51.4 years (+/- 12.1 years). Different types of prostheses were implanted including porcine and bovine pericardial bioprostheses and older and bileaflet mechanical valves. Most patients were severely disabled by their cardiac disease before operation, with 30.1% in New York Heart Association functional class III and 69.9% in class IV. Operative mortality and hospital mortality rates (30 days) were high (16.4%). Incremental risk factors for hospital death included icterus (p < 0.005), preoperative hepatomegaly (p = 0.012), and New York Heart Association functional class IV (p = 0.013). Multivariate analysis only selected preoperative icterus (p < 0.01) as being independently significantly related to hospital mortality. The hospital survivors were followed up for a median of 94 months. A complete follow-up was available for all patients except two for 30 months or more. At 30 months the only two significant parameters were the type of myocardial protection (p = 0.024) and the year of operation (before 1977 or after [precardioplegia era or after], p = 0.011). There were 70 late deaths during the entire follow-up period. The univariate (log-rank statistics) incremental risk factor for late death was the type of tricuspid prosthesis (Smeloff-Cutter and Kay-Shiley versus St. Jude Medical versus bioprosthesis) (p = 0.04). A trend was observed for the type of operative myocardial protection (normothermia and coronary perfusion) (p = 0.06) and preoperative New York Heart Association functional class IV (p = 0.055). Actuarial survival was 74% at 60 months and 23.4% at 180 months. Cumulative follow-up added up to 1015 patient-years. In a more detailed analysis of the effect on survival of the type of tricuspid prosthesis, a significant difference was observed between the bioprostheses and some older mechanical prostheses (Smeloff-Cutter and Kay-Shiley) (p = 0.04) but not between the bioprostheses and the bileaflet valves (p = 0.15). When the follow-up period was stratified according to less than 7 years and more than 7 years of follow-up, no difference was observed for the first period, but for the late follow-up the new mechanical prostheses did better than the bioprostheses (p = 0.05), suggesting a degradation of the bioprostheses after 7 years and favoring mechanical prostheses for those patients with a good long-term prognosis.

Monte Carlo calculations of dose distributions around 32P and 198Au stents for intravascular brachytherapy.

3D dose distributions are calculated for a 32P impregnated stent and a 198Au stent for intravascular brachytherapy with the EGS4 Monte Carlo simulation code. The stents were modeled as a combination of eight helicoidal struts. This allowed investigation of the effect of the stent geometry and the electron absorption in the strut material on the dose distributions. Absorbed dose to water was calculated at radial distances ranging from 50 microm to 5 mm from the stent surface. The dose distributions around the stents are compared to the dose distribution around an intravascular brachy-therapy 192Ir source, also calculated with the EGS4 Monte Carlo code. The dose profiles near the struts show hot spots. At 50 microm distance a peak to valley ratio of 3 for 32P and 6 for 198Au in the dose distribution is obtained. For both the isotopes the inhomogeneities decrease with distance and at a radial depth of 350 microm the effect becomes negligible. The calculations showed the importance of the effect of the absorption in the stent material as this leads to a dose decrease to 67% for the 198Au stent and to 77% for 32P near the stent at a distance of 2 mm from the stent axis. It is concluded that from the dosimetric point of view, the 198Au stent is inferior to the 32P stent and the 192Ir source. Application of the 198Au stent in clinical practice requires further investigation of the importance of the adventitia in the restenosis process, and the tolerance dose of the intima.

Cardiac involvement in pheochromocytoma.

We report the details of a 40-year-old farmer, a cigarette smoker, who was admitted with general malaise, nausea, vomiting, upper abdominal pain, with ST-elevation on ECG suggestive of an acute anterolateral myocardial infarction. He was treated with nitrates, heparin, beta-blockade and angiotensin-converting enzyme (ACE) inhibitors. Because of the presence of some blood while vomiting no thrombolysis was given and abdominal echography was performed. This revealed a nodular mass at the right adrenal gland. Urinary catecholamines and abdominal magnetic resonance imaging confirmed the suspected diagnosis of pheochromocytoma. Before adrenectomy, a coronary angiography under alpha blocker therapy was performed, which demonstrated no significant coronary artery disease, although the patient showed ST-elevations on ECG. Pathological examination of the adrenal tumor was compatible with a diagnosis of pheochromocytoma. Postoperatively urinary catecholamines dropped dramatically, and the ECG normalised slowly over time. After 8 months the patient is still well. Blood pressure is well controlled with no antihypertensive drugs and exercise testing shows no evidence of myocardial ischaemia.

Dosimetry of 192Ir sources used for endovascular brachytherapy.

An in-phantom calibration technique for 192Ir sources used for endovascular brachytherapy is presented. Three different source lengths were investigated. The calibration was performed in a solid phantom using a Farmer-type ionization chamber at source to detector distances ranging from 1 cm to 5 cm. The dosimetry protocol for medium-energy x-rays extended with a volume-averaging correction factor was used to convert the chamber reading to dose to water. The air kerma strength of the sources was determined as well. EGS4 Monte Carlo calculations were performed to determine the depth dose distribution at distances ranging from 0.6 mm to 10 cm from the source centre. In this way we were able to convert the absolute dose rate at 1 cm distance to the reference point chosen at 2 mm distance. The Monte Carlo results were confirmed by radiochromic film measurements, performed with a double-exposure technique. The dwell times to deliver a dose of 14 Gy at the reference point were determined and compared with results given by the source supplier (CORDIS). They determined the dwell times from a Sievert integration technique based on the source activity. The results from both methods agreed to within 2% for the 12 sources that were evaluated. A Visual Basic routine that superimposes dose distributions, based on the Monte Carlo calculations and the in-phantom calibration, onto intravascular ultrasound images is presented. This routine can be used as an online treatment planning program.