Modifying fluoroscopic views reduces operator radiation exposure during coronary angioplasty.

OBJECTIVES: This three-part study examined the feasibility of reducing operator radiation exposure during coronary angioplasty. BACKGROUND: As case loads and complexity increase, some cardiologists are receiving increasing radiation scatter doses. Techniques to reduce this are therefore becoming more important. METHODS: First, the determinants of the operator dose were assessed by measuring the differences in scatter dose with different camera views. The relative contribution of fluoroscopy as opposed to cine was then quantified. Finally, operators were provided with these data, and subsequent changes in technique were evaluated. RESULTS: Left anterior oblique views resulted in 2.6 to 6.1 times the operator dose of equivalently angled right anterior oblique views. Increasing steepness of the left anterior oblique view also resulted in a progressive increase in operator dose, with left anterior oblique 90 degrees causing eight times the dose of left anterior oblique 30 degrees and three times that of left anterior oblique 60 degrees. In the 45 coronary angioplasty cases prospectively analyzed, fluoroscopy was found to be a greater source of total radiation than cine by a 6.3:1 ratio (range 1.1 to 15.8). Once operators were made aware of the importance of left anterior oblique fluoroscopy, there was a marked reduction in its use. When this was not feasible, there was a reduction in the steepness of the angulation. Left anterior oblique fluoroscopy during angioplasty of the left anterior descending and circumflex coronary arteries was reduced from 40% of total screening time to approximately 5%, and left anterior oblique angulation for fluoroscopy during angioplasty of the right coronary artery decreased from 43.6 degrees (+/- 9.1 degrees) to 29.4 degrees (+/- 2.2 degrees). Success rates (90% vs. 89%) and screening times (19.5 vs. 20.7 min) remained unchanged in 200 coronary angioplasties performed after the study. Average operator radiation dose (measured by radiation badges worn under lead at waist level) was reduced from 32.6 to 14.3 microSv/operator per week despite a slight increase in case load. CONCLUSIONS: Fluoroscopy is the major source of total radiation exposure during coronary angioplasty, with left anterior oblique views providing the highest dose. Modification of views is feasible and will result in significant reduction of operator radiation dose.

Reactive hyperaemia in the dog heart: inter-relations between adenosine, ATP, and aminophylline and the effect of indomethacin.

Intracoronary adenosine, ATP, and the release of an 8 second occlusion increased coronary blood flow (CBF) to a similar extent. Aminophylline decreased the CBF response to adenosine by 80% and that to an 8 s occlusion by 20% but did not change the CBF response to ATP. Indomethacin had no effect on CBF. The results suggest that the increase in CBF after brief occlusions is not mediated in a major way by adenosine or prostaglandins.

Reactive hyperaemia in the dog heart: evidence for a myogenic contribution.

Temporary restriction of arterial inflow after release of eight second coronary artery occlusions greatly reduced reactive hyperaemia but prolonged its duration. Early repayment of the flow debt before restriction did not alter these changes. Despite reduced hyperaemia, there was evidence of subendocardial ischaemia during restriction. Yet occlusions of only one and two cardiac cycles produced marked hyperaemia without evidence of post-release subendocardial ischaemia. All these changes were associated with alterations in peripheral coronary artery pressure consistent with myogenic responses contributing to reactive hyperaemia.

Effects of catecholamines on the coronary circulation in the Langendorff-type transplanted dog heart.

Intracoronary administration of isoprenaline, adrenaline, and the noradrenaline in the Langendorff-type transplanted dog heart transiently decreased coronary blood flow measured from the inflow vessel; flow then increased. The reduction in coronary flow coincided with increased myocardial contractility and was prevented by keeping the left ventricle empty. Propranolol prevented changes in flow and contractility. It is concluded that positive inotropic changes result in the ejection of accumulated Thesbesian flow from the ventricle and affect coronary flow measurements and that the interpretation of flow changes requires a steady state.

Left ventricular systolic performance during upright bicycle exercise in patients with essential hypertension.

Left ventricular performance was evaluated at rest and during maximal upright bicycle exercise in 51 patients with chronic essential hypertension. Twenty-eight of these patients had no clinical or electrocardiographic evidence of coronary artery disease and comprise the primary study population. The remaining 23 patients had coronary artery disease and represent a comparison group. First-pass radionuclide angiocardiograms were obtained at rest and during maximal upright bicycle exercise, allowing evaluation of global left ventricular ejection fraction and regional wall motion. At the time of the radionuclide studies, all patients were hypertensive, defined as a diastolic blood pressure 90 mm Hg or greater and/or a systolic blood pressure 140 mm Hg or greater with the patient at rest and sitting. In the primary study group, the left ventricular functional response to upright bicycle exercise was normal in 26 of 28 patients. Left ventricular ejection fraction averaged (+/- standard error) 65 +/- 2 percent at rest and increased significantly to 76 +/- 2 percent with exercise (p less than 0.001). Regional wall motion was normal both at rest and during exercise in all patients. Seventeen patients had electrocardiographic evidence of left ventricular hypertrophy, and 14 were receiving propranolol therapy. The left ventricular functional response also was normal in these subgroups. In contrast to the nearly uniform normal left ventricular responses noted in the patients with hypertension alone, the group with concomitant coronary artery disease had a markedly higher incidence of abnormal left ventricular reserve (19 of 23 versus two of 28, p less than 0.001) during exercise. Thus, in most patients with essential hypertension but without concomitant coronary artery disease, left ventricular reserve during exercise was normal. Hypertension, even with left ventricular hypertrophy, should not be viewed as the cause for an abnormal left ventricular response to exercise in a patient undergoing diagnostic exercise radionuclide angiocardiography.

Late cardiac, thyroid, and pulmonary sequelae of mantle radiotherapy for Hodgkin's disease.

Cardiac, thyroid and pulmonary function were evaluated in 25 patients aged 35 years or under, treated for Hodgkin's disease by mantle radiotherapy 5-16 years previously. No patient had symptoms of heart disease. Although thallium myocardial perfusion scintigraphy was normal in all patients, abnormalities of myocardial function were detected in 6 (24%) patients using gated equilibrium rest and exercise radionuclide ventriculography. Resting left ventricular ejection fraction (LVEF) was abnormal in 1 patient, and in 3 patients there was an abnormal LVEF response to exercise. All 6 patients had right ventricular dilatation. Apical hypokinesia was present in 4 of these patients. A small asymptomatic pericardial effusion was detected by M-Mode echocardiography in only 2 (8%) patients. Twenty-three (92%) patients had evidence of abnormal thyroid function. Two (8%) patients had become clinically hypothyroid. Serum TSH was elevated in 13 (52%) patients and TRH stimulation test was abnormal in a further 10 (40%) patients in whom TSH was normal. Pulmonary function studies showed a moderate decrease in diffusing capacity (72% of predicted) and a minor reduction in lung volume. Although a high incidence of cardiac, thyroid and pulmonary abnormalities was detected, only the 2 patients who had become hypothyroid were symptomatic. Modification of the irradiation technique may reduce the incidence of cardiac abnormalities, but is unlikely to alter significantly the thyroid or pulmonary sequelae.

Early and long-term results of coronary artery bypass grafting with severely depressed left ventricular performance.

The effects of coronary artery bypass grafting (CABG) on ventricular performance and long-term clinical status were studied in 18 consecutive patients with disabling angina pectoris and severely depressed left ventricular (LV) performance (ejection fraction [EF] 27 +/- 9%). All patients survived CABG, although 1 patient had a perioperative myocardial infarction. There was no change in LVEF at rest, 29 +/- 12%, in the other 17 patients. However, LVEF during peak exercise increased from 22 +/- 7% to 27 +/- 14% (p less than 0.05). The 17 patients were separated into 2 groups: those who increased their peak exercise LVEF by at least 10% (group A, 8 patients) and those who increased it by less than 10% (group B, 9 patients). Preoperatively, patients in group A had a higher LVEF at rest (p less than 0.001) and smaller end-systolic and end-diastolic volumes at rest (p less than 0.001) and during exercise (p less than 0.005). Preoperatively, the LVEF in group A decreased with exercise, from 36 +/- 4% to 27 +/- 5% (p less than 0.01), but was unchanged in group B (19 +/- 3% vs 17 +/- 4%, difference not significant). After CABG, patients in group A had a smaller increase in end-systolic volume with exercise than those in group B (13 +/- 7 vs 34 +/- 22 ml/m2, p less than 0.05), but the changes in end-diastolic volume with exercise were not significantly different. At 27 +/- 5 months after CABG, 5 of 8 patients in group A were asymptomatic.(ABSTRACT TRUNCATED AT 250 WORDS)

Impact of an aggressive coronary stenting strategy on the incidence of target lesion revascularization.

Coronary stenting has been shown to reduce the incidence of target lesion revascularization (TLR) compared with balloon angioplasty in highly selected patients. However, the impact of an aggressive coronary stenting strategy in unselected patients on the overall incidence of TLR is unclear. We assessed the effect of increased stenting by comparing long-term results in consecutive patients who underwent successful percutaneous revascularization (with or without stents) during June to December 1995 (n=347) with those in June to December 1996 (n=401). Stents were used in 22.5% of patients in 1995 versus 66.1% in 1996 (p <0.0001). Mean age of the patients was 62+/-11 years (71% men) in 1995 versus 63+/-10 in 1996 (76% men) (p=NS). The 2 groups were well matched with the exception that the 1996 cohort included more patients with unstable coronary syndromes (25% in 1995 vs 34% in 1996 (p=0.003). There was no significant difference in the incidence of in-hospital adverse events. After 12 months of follow-up (complete in 95% of patients in each group), the incidence of TLR was significantly lower in the 1996 cohort than in the 1995 cohort (8.5% vs 14.7%, p=0.0075). This was mainly due to reduced requirement for repeat angioplasty in 1996 patients compared with 1995 (6.5% vs 11.8%, p=0.011). It is concluded that in an unselected patient population, an aggressive coronary stenting strategy was associated with a marked overall reduction in requirement for TLR over a 12-month period.

Continuous monitoring of left ventricular performance with the computerized nuclear probe during laryngoscopy and intubation before coronary artery bypass surgery.

Left ventricular performance was monitored serially in 25 patients during laryngoscopy and intubation in the anesthetic induction period before elective coronary artery bypass surgery using the labeled equilibrium blood pool and the computerized nuclear probe. Left ventricular ejection fraction was obtained preoperatively, after induction of anesthesia but before endotracheal intubation, immediately after intubation, and at 1 minute intervals thereafter for 10 minutes. In all patients, there was an immediate decrease (mean 16%) in left ventricular ejection fraction accompanying the reflex hypertension and tachycardia occurring during laryngoscopy and endotracheal intubation; it was significantly depressed for 3 minutes with the concomitant hemodynamic changes. Seven patients did not demonstrate a recovery of left ventricular ejection fraction to the preintubation value. In 10 healthy noncardiac patients undergoing orthopedic surgery, after an identical anesthetic induction sequence and intubation, there was a similar decrease in ejection fraction, but of shorter duration. In these patients the recovery of left ventricular performance preceded the recovery of blood pressure and heart rate. This study demonstrates that profound decreases in left ventricular performance accompany the reflex hypertension and tachycardia occurring during endotracheal intubation and that there is persisting depression of left ventricular function in some patients with coronary artery disease. These findings indicate the potential utility of the computerized nuclear probe for monitoring ventricular performance during this critical period.

Gold- 195m, a new generator-produced short-lived radionuclide for sequential assessment of ventricular performance by first pass radionuclide angiocardiography.

The feasibility of performing rapid sequential first pass radionuclide angiocardiography using a new short-lived radiotracer, gold-195m (195mAu) half-life 30.5 seconds) was evaluated. This radionuclide emits a 262 keV gamma ray and is the daughter of mercury-195 (195mHg) (half-life 41.6 hours). The prototype tabletop 195mHg/195mAu generator produced 20 to 25 mCi of 195mAu in 2 ml of eluate (yield of 40 percent). The breakthrough of 195mHg in the eluate was 0.02 percent of the amount of 195mHg in the generator. The eluate contained 20 microCi of 195mHg per study, resulting in an estimated human radiation dose of 0.007 rad/study to the whole body and 0.34 rad/study to the kidney. Four dogs each had 15 to 20 sequential first pass studies performed with 195mHg at 3 to 10 minute intervals using a computerized multicrystal gamma camera. During the left ventricular phase, 160,000 to 190,000 counts/s were acquired. The end-diastolic left ventricular region of interest contained 3,000 to 6,000 counts (background- and decay-corrected). Multiple reproducible values for left ventricular ejection fraction were obtained during stable conditions. The mean (+/- standard deviation) interstudy variability was 4 +/- 2 percent. During infusion of isoproterenol, rapid increase of left ventricular ejection fraction was demonstrated. Excellent agreement was observed between studies performed with technetium-99m diethylenetriaminepentaacetic acid (99mTc-DTPA) and 195mAu. The mean interstudy difference was 4 +/- 3 percent. Thus, sufficiently high yield and dose are obtained from the 195mHg/195mAu generator for reliable high count rate first pass determination of left ventricular ejection fraction. This new short-lived radiotracer makes possible rapid sequential assessments of ventricular function at greatly reduced patient exposure to radiation.

Regional left ventricular wall motion assessment: comparison of two-dimensional echocardiography and radionuclide angiography with contrast angiography in healed myocardial infarction.

The diagnostic ability of radionuclide angiography (RNA) and 2-dimensional echocardiography (2-D echo) to assess regional left ventricular (LV) wall motion was compared with contrast angiography in 52 patients with healed myocardial infarction. After 5 patients were excluded for inadequate 2-D echocardiographic studies, the LV images of 47 patients obtained by all 3 techniques were divided into 7 segments for analysis. Both 2-D echo and RNA showed close agreement with contrast angiography in assessing normal vs abnormal wall motion in the anterobasal (91%, 91%), anterolateral (87%, 79%) and posterolateral segments (77%, 79%). The sensitivity in detecting wall motion abnormalities was highest for 2-D echo and RNA in the anterolateral (83%, 77%) and apical (95%, 84%) segments and lowest for the inferior segment (48%, 48%). Specificity of 2-D echo and RNA was high, ranging from 94% in the anterolateral segment to 71% in the septal segment for 2-D echo, and from 91% in the inferior segment to 81% in the posterobasal and septal segments for RNA. Major discrepancies with contrast angiography occurred more often in the posterobasal, posterolateral, inferior and septal LV segments. Thus, in comparison with contrast angiography, 2-D echo and RNA are reliable for detecting anterior and apical wall motion abnormalities, but relatively less sensitive for detecting wall motion abnormalities involving the inferior, posterobasal and posterolateral LV segments.

Histamine receptors in the coronary circulation of the dog. Effects of mepyramine and metiamide on responses to histamine infusions.

The effect of histamine on coronary blood flow (CBF) was studied in anaesthetized grayhounds. CBF and systemic blood pressure were measured using electromagnetic flow transducers and catheters in the aorta during infusions of drugs into the left circumflex coronary artery. Histamine infusions (5, 10, and 20 microng/min) produced dose-related increases in CBF without changing heart rate or blood pressure. Metiamide (100 microng/min) given simultaneously produced a parallel displacement of the histamine dose-response curve to the right (P less than 0.05) with a dose ratio of 2. Mepyramine (100 microng/min) produced a larger parallel displacement of the dose-response curve (dose ratio = 4). Together, metiamide and mepyramine greatly reduced the histamine response (dose ratio = 16), showing that the metiamide blockade is augmented in the presence of mepyramine. Similarly, mepyramine blockade is augmented in the presence of metiamide. The increase in CBF produced by histamine infusion (20 microng/min) was similar to the peak flow response of reactive hyperemia following 8-second occlusions. However, mepyramine and metiamide together had no effect on the peak flow response, duration, or total repayment of flow debt in reactive hyperemia. These results show that histamine-induced coronary vasodilation is mediated by both H1 and H2 receptors. However, the vasodilation of reactive hyperemia after brief coronary artery occlusions does not appear to involve histamine.

Pregnancy-induced changes in rabbit medial collateral ligament vasoregulation.

The ligaments of weight-bearing joints are known to become mechanically inferior during pregnancy, and it has been postulated that this may be due to changes in tissue perfusion. Calcitonin gene-related peptide (CGRP) and epinephrine exert a tonic influence on the vasculature of the medial collateral ligament (MCL), and the present study examined whether these vasoactive influences were altered by pregnancy. Ligament perfusion experiments were performed on primigravid New Zealand White rabbits with the use of laser Doppler perfusion imaging. In pregnant animals (day 29), MCL basal perfusion fell significantly compared with control; however, values returned to normal 5 days postpartum. In normal joints, topical application of CGRP resulted in a dose-dependent increase in MCL perfusion, whereas epinephrine administration caused a dose-dependent fall in blood flow. During pregnancy, the vasodilator effect of CGRP was completely abolished, whereas adrenergic vasoconstriction was greater than normal. Both responses returned postpartum. Pregnancy in the rabbit produces hypoemia in the MCL, and this phenomenon may be effected by a tempering of CGRP dilator responses and an augmentation of alpha-adrenoceptor-mediated vasoconstriction.

Left ventricular volumes in moderate alcohol users: a study from the workplace.

We measured resting and exercise left ventricular volumes by a count-based, nongeometric radionuclide method in 23 healthy volunteers grouped according to reported average daily alcohol consumption: 0-20 g (Gp A), 21-50 g (Gp B) and greater than 50 g (Gp C). No patient had measurable alcohol in his blood at the time of study. Mean resting LV Ejection Fraction (EF) was 65 +/- 2% in Group A, 64 +/- 2% in Group B, and 65 +/- 3% in Group C. Exercise EF was 76 +/- 1,75 +/- 3 and 74 +/- 4%, respectively. Resting Endsystolic Volume Indices in the three groups were 19.2 +/- 3, 18.9 +/- 2 and 21.8 +/- 3 ml/m2; exercise values were 15.9 +/- 2, 12.8 +/- 2 and 13.3 +/- 2 ml/m2, respectively. This cohort was selected for absence of markers of alcohol-related illness, and all subjects were employed. We found no evidence for impaired left ventricular systolic function with moderate alcohol usage using a sensitive radionuclide technique.

Sustained normalization of cardiac function by chelation therapy in thalassaemia major.

The effect of iron chelation using subcutaneous desferrioxamine on the iron-overloaded heart was studied prospectively over 4 years in 23 asymptomatic patients (mean age 13.2 +/- 5.3 years) with thalassaemia major and transfusion-dependent anaemia. The haemoglobin was maintained greater than 10 g/dl by transfusion and chelation therapy to achieve a negative iron balance. Chelation was closely supervised to ensure compliance. Despite an increase in calculated iron load due to transfusion from 34 +/- 27 g to 63 +/- 28 g, there was a sequential fall in serum ferritin levels from 3148 +/- 1956 ng/ml to 2228 +/- 1825 ng/ml (P less than 0.05). Abnormalities of left ventricular (LV) function, assessed by radionuclide angiography, were present at rest or during exercise in 18 of 23 patients (78%) prior to therapy. Normal LV function was restored in 11 of these 18 patients, five continuing to have abnormal function and two dying. There was a significant increase in resting LVEF from 50 +/- 8% to 57 +/- 6% (P less than 0.01). Peak exercise LVEF rose from 51 +/- 11% to 65 +/- 7% (P less than 0.001). We conclude that the common subclinical abnormalities of LV function induced by iron overload in unchelated patients with thalassaemia major can be reversed with long-term subcutaneous infusions of desferrioxamine.

Activated clotting time differential is a superior method of monitoring anticoagulation following coronary angioplasty.

The standard high-range activated clotting time (sHR ACT) is used to monitor anticoagulation postangioplasty (PTCA), but may be unreliable. We assessed the accuracy of a new method we termed the ACT differential (ACT Diff), obtained by measuring the difference between an sHR ACT and a heparinase ACT from the same sample. Heparinase removes heparin from its sample and provides a current heparin-free baseline. For phase 1 of the study, the sHR ACT, ACT Diff, and laboratory APTT were measured in 250 samples from 75 PTCA patients. In 125 samples with an APTT prolonged but within measurement range, linear regression against the APTT was performed. The correlation coefficient was 0.74 for the ACT Diff and 0.24 for the sHR ACT. An ACT Diff of 15-25 sec was found to equal an APTT of 2.5-3.5 x control. In 50 samples with a normal activated partial thromboplastin time (APT), there was good differentiation by the ACT Diff of results from those adequately heparinized, with a value of 0.9 +/- 4.4 sec. The sHR ACT was 114 +/- 15.5 sec, and could not reliably distinguish between anticoagulated and nonanticoagulated samples. In 75 samples obtained with a high APTT (above measurement range), the ACT Diff was > 30 sec in 95% of samples, and again this allowed differentiation from therapeutic samples. The equivalent sHR ACT was 148 sec, and could not reliably distinguish between anticoagulated and overanticoagulated samples as the ACT Diff could. In phase 2, to examine the clinical usefulness of the ACT Diff, 286 patients were managed post-PTCA by starting heparin when ACT Diff fell to < 50 sec, maintaining ACT Diff at 15-25 sec during heparin infusions, and following cessation of heparin, by removing sheaths when the ACT Diff was < 7 sec. These patients were compared to a control group of 250 patients. Major bleeding (5% vs. 0.5%, P < 0.005) and minor bleeding (30% vs. 13%, P < 0.001) were significantly reduced in the group managed using the ACT Diff. The reduction in bleeding was thought to be due to the rapid availability of reliable results. Abrupt closure was low in both groups (0% with ACT Diff vs. 0.8%). No other thrombotic events occurred. Following phases 1 and 2, the ACT Diff replaced the APTT in all PTCA patients at this institution. In the 18 mo from July 1993, 1,104 patients were managed this way. Incidence of major bleeding (0.2%), transfusion requirement (0.1%), false anneurysm (0.6%), and abrupt closure during heparin infusion (0.1%) remained low. In conclusion, the ACT Diff is more accurate than an sHR ACT, and its clinical use in PTCA patients is associated with a very low incidence of complications from anticoagulation. Its routine use should be considered by units unable to obtain rapid APTT results.

Early left ventricular dysfunction and chelation therapy in thalassemia major.

Exercise radionuclide angiography was used to assess the incidence of subclinical abnormalities of left ventricular function in 23 asymptomatic patients with thalassemia major. Left ventricular ejection fraction (LVEF) at rest was normal in 18 patients and abnormal in 5. A normal LVEF response during exercise was shown in only 5 of the patients with normal resting left ventricular function. A normal response during exercise occurred more often in those patients who had received a smaller transfusional iron load and had a lower serum ferritin level (p less than 0.05). Twelve of the twenty-three patients were receiving chelation therapy with subcutaneous deferoxamine. Ejection fraction at rest was normal in 11 of these patients. During exercise a normal ventricular response was shown in 4 patients. After 1 year of intensive chelation therapy in these 12 patients, left ventricular function was reassessed. A normal exercise response was seen in an additional 4 patients; 3 of these showed an increase in peak exercise LVEF, and in the remaining patient no change of peak exercise LVEF was shown. The response during exercise was unchanged in 3 patients and had deteriorated in 1 patient.