Radiation safety in the cardiac catheterization laboratory.

Over the years, permissible radiation exposure of operators working with x-ray equipment has become progressively reduced. The number of cardiac catheterizations and related interventional procedures has increased and the procedures have become more prolonged. The patient receives relatively infrequent primary radiation while the operator receives frequent but mainly secondary radiation. The operator uses protective barriers, correct positioning of the patient and careful techniques to reduce radiation exposure. The effects of radiation are cumulative and permanent. They may be stochastic or nonstochastic, and somatic and/or genetic, and onset may be delayed for many years. To minimize exposure of patient and operator, cardiologists need a better understanding of radiation physics and of cardiac x-ray equipment. Technical breakthroughs such as digital imaging, pulse fluoroscopy, reduction of frame rates from 60 or 30 frames/s to 15 frames/s, and progression to the filmless laboratory will substantially reduce radiation. This review discusses current cardiac x-ray equipment, possible future developments, radiation, and techniques for reducing radiation and improving safety in the cardiac catheterization laboratory.

Angioplasty of isolated acute marginal coronary artery disease.

This report describes a patient who presented with a non Q wave myocardial infarction and post-infarction angina. Angiography revealed that his only significant disease was a severe lesion in an acute marginal branch of the right coronary artery. Balloon angioplasty was performed successfully with subsequent stabilization and no recurrence of angina in a 9-month follow-up. This case raises the possibility that acute marginal disease may contribute to ischemic syndromes and warrants consideration for revascularization.

Percutaneous coronary laser balloon angioplasty: initial results of a multicenter experience.

A multicenter clinical trial was initiated to test the potential safety and short-term efficacy of a percutaneous coronary application of laser balloon angioplasty, which has been shown experimentally to alleviate the common causes (dissection, recoil, thrombus) of suboptimal luminal results of conventional balloon angioplasty. Fifty-five patients, the majority (62%) of whom had relatively high risk lesions, were treated in 10 centers with a laser balloon that was identical in size (3 x 20 mm) to a balloon used for conventional balloon angioplasty performed on the same lesion immediately before laser balloon angioplasty. One or more neodymium:yttrium aluminum garnet (Nd:YAG) (1,060 nm) laser doses of 250 to 450 J were each delivered over a 20 s duration per exposure. Immediately and 1 day after laser balloon angioplasty no significant adverse effects on the arterial lumen were noted in any patient. By computerized image analysis of cineangiograms initial conventional balloon angioplasty failed to achieve a minimal luminal diameter greater than 1.5 mm in 14 patients (25%), including 3 patients with acute closure. However, after subsequent laser balloon angioplasty, minimal luminal diameter exceeded this value in all patients including this subgroup. Overall, minimal luminal diameter increased from 1.74 +/- 0.46 mm after conventional balloon angioplasty to 2.32 +/- 0.31 mm after laser balloon angioplasty (p less than 0.001) with no change found on 1 day and 1 month follow-up angiograms. Thus, laser balloon angioplasty is a safe, effective procedure for improving luminal dimensions after conventional balloon angioplasty.

Twelve-lead electrocardiogram recording during percutaneous transluminal coronary angioplasty. Analysis of reciprocal changes.

Coronary angioplasty was used as a human model of transient myocardial ischemia to evaluate the electrocardiographic characteristics and significance of "reciprocal" ST-segment depression and T wave changes. Continuous 12-lead ECGs were recorded before and during coronary angioplasty in 20 patients, 19 of whom had single vessel disease. In 12 of 14 patients, LAD occlusion produced ischemic changes (peaked T and/or ST elevation) in L1, AVL and at least two precordial leads. "Reciprocal" changes (ST depression and/or T inversion) were observed in at least two inferior wall leads. One patient had ST depression in V4-V6 with no change in the inferior leads and in the other the only ECG change was inferior ST depression with partial inversion of the T wave. In four of six patients, RCA occlusion produced ischemic changes in at least two inferior wall leads and "reciprocal" changes in L1, AVL and at least two anterior wall leads. In LAD as well as RCA occlusions "reciprocal" changes were characterized by inversion of the T wave or inversion of its ascending limb with or without ST depression. The magnitude of the ischemic changes tended to be proportional to the magnitude of the "reciprocal" changes. Our data suggest that: (1) "Reciprocal" changes are not a specific indicator of distant myocardial ischemia due to multivessel disease; (2) the magnitude of ischemic changes correlates with the magnitude of "reciprocal" changes; (3) "Reciprocal" changes may be the only manifestation of acute myocardial ischemia; and (4) "Reciprocal" changes may be represented by inversion of the T wave without displacement of the ST-segment.

Quantitative arteriographic responses to ergonovine provocation in subjects with atypical chest pain.

To evaluate the nonspecific vasoconstrictor response to intravenous ergonovine, and identify patient-related factors that systematically alter changes in coronary dimensions, 33 subjects (22 women, 11 men), mean age 54 years (range 39 to 70) were studied using a standardized ergonovine provocation test (Stanford protocol). Clinical responses, systemic hemodynamics and electrocardiographic changes were determined, with quantitative arteriography used for sequential measurement of proximal right coronary dimensions. A progressive decrease in proximal right coronary diameter was observed, with average control values and final diameters equaling 3.25 +/- 0.49 and 2.56 +/- 0.49 mm, respectively, thus representing an overall -21.2% change from baseline. No significant differences existed in control dimensions when analyzed with respect to gender (3.20 +/- 0.59 vs 3.40 +/- 0.72 mm, women vs men, difference not significant), although women demonstrated a greater decrease from baseline values (0.80 +/- 0.30 vs 0.50 +/- 0.24 mm, women vs men, p less than 0.05). The presence of minor atherosclerotic disease, as determined by the presence of minor (less than 30% diameter) luminal irregularities within the right coronary artery, failed to alter control dimensions (3.30 +/- 0.48 vs 3.20 +/- 0.51 mm, normal vs atherosclerotic persons, difference not significant), but was associated with more ergonovine-induced coronary vasospasm (0.41 +/- 0.27 vs 0.84 +/- 0.21 mm, normal vs atherosclerotic persons, p less than 0.01). Therefore, sequential intravenous ergonovine maleate infusion resulted in progressive, nonspecific reductions in proximal right coronary artery dimensions in subjects without a history compatible with vasospastic angina. This nonspecific vasoconstrictor effect was accentuated in women and subjects with intimal irregularities suggestive of minor atherosclerotic coronary disease.

Percutaneous transluminal angioplasty of stenotic saphenous vein right coronary bypass grafts utilizing a peripheral balloon dilatation catheter without a guiding catheter.

Effective angioplasty of stenosed saphenous vein coronary bypass grafts may be impossible with the standard-size coronary dilatation catheters because the large diameter of these grafts results in unacceptable balloon-to-vessel ratios. We avoided this problem by using a peripheral arterial dilatation catheter with an inflation diameter of 6 mm and obtained a satisfactory short- and long-term result in two patients in whom previous attempts with the largest coronary dilatation catheter (4 mm) had failed. This technique, which precludes the use of a guiding catheter, is suitable only for right bypass grafts.

Why animals have different muscle fibre types.

Animals have different muscle fibre types: slow fibres with a low maximum velocity of shortening (Vmax) and fast fibres with a high Vmax. An advantage conferred by the use of different fibre types during locomotion has been proposed solely on the basis of their in vitro properties. Isolated muscle experiments show that force generation, mechanical power production and efficiency are all functions of V/Vmax, where V is the velocity of muscle shortening. But it is not known whether animals actually use the different fibres at shortening velocities that are optimal for mechanical power production and efficiency. Here we compare the V of muscle fibres during locomotion with their Vmax. This comparison shows that during slow locomotion, the slow fibres shorten at a velocity that gives peak mechanical power and efficiency and the fast fibres shorten at their optimal velocity when powering maximal movements. Our results also show that maximal movements are impossible without fast fibres because the slow ones cannot shorten rapidly enough.

Aspirin and dipyridamole in the prevention of restenosis after percutaneous transluminal coronary angioplasty.

To examine the role of antiplatelet therapy in the prevention of arterial restenosis after percutaneous transluminal coronary angioplasty (PTCA), we conducted a randomized, double-blind, placebo-controlled study in 376 patients. The active treatment consisted of an oral aspirin-dipyridamole combination (330 mg-75 mg) given three times daily, beginning 24 hours before PTCA. Eight hours before PTCA, the oral dipyridamole was replaced with intravenous dipyridamole at a dosage of 10 mg per hour for 24 hours, and oral aspirin was continued. Sixteen hours after PTCA, the initial combination was reinstituted. Treatment was continued in patients with a successfully dilated vessel until follow-up angiography four to seven months after PTCA--or earlier, if symptoms dictated. Of 249 patients who underwent follow-up angiography, 37.7 percent of patients receiving the active drug had restenosis in at least one segment, as compared with 38.6 percent of patients taking placebo (P not significant). The number of stenotic segments was virtually the same in the two groups. Among the 376 randomized patients, there were 16 periprocedural Q-wave myocardial infarctions--13 in the placebo group and 3 in the active-drug group (6.9 percent vs. 1.6 percent, P = 0.0113). Although the use of this antiplatelet regimen before and after PTCA did not reduce the six-month rate of restenosis after successful coronary angioplasty, it markedly reduced the incidence of transmural myocardial infarction during or soon after PTCA. Thus, the short-term use of antiplatelet agents in relation to PTCA can be recommended.

Complications associated with the guide wire in percutaneous transluminal coronary angioplasty.

This report describes three cases of unraveling of the platinum coil of the guide wire during percutaneous transluminal coronary angioplasty. In one case the wire ruptured and required surgical removal. The exact cause of this phenomenon is not known, but wire entrapment may be a factor. This is more likely to occur with tortuous vessels. Precautions to avoid uncoiling and rupture of guide wires during coronary angioplasty are discussed.

Turning flight of bats.

The turning flight of six microchiropteran bat species is described. The bats' abilities to turn tightly were determined by their abilities to fly slowly and to generate high lateral accelerations. Rhinolophus ferrumequinum developed high lateral accelerations by flapping its banked wings while flying at very low speed. Plecotus auritus turned at relatively low speed and at low lateral acceleration. The other species were all moving fast as they turned and generated lateral accelerations either by developing high bank angles or by flapping their wings with low bank angles. There was a significant correlation between wing loading and turning curvature, indicating that low wing loadings improve manoeuvrability.

The symptomatic status of patients one year following revascularization by either coronary surgery or angioplasty.

This study consisted of a one year clinical follow-up of 81 patients who had coronary revascularization. In 32 patients, this was accomplished by bypass surgery and in 49, by percutaneous angioplasty. Prior to the procedure the two groups of patients were similar with regard to age, sex, antianginal medication and angina severity with 75% of the surgical patients and 65% of the angioplasty patients in CCS Angina Class III or IV. Although most of the surgical patients had multivessel disease and most of the angioplasty patients had single vessel disease, all had complete revascularization. At one year, 78% of the surgical patients and 84% of the angioplasty patients did not have angina and few patients in either group were taking medication. However, in the intervening year 39% of the angioplasty patients had had a second revascularization procedure, whereas, only 3% of the surgical patients required a second procedure. Extracardiac sequelae were more frequent in the surgical cohort. Therefore, at one year following complete revascularization, bypass surgery and angioplasty result in comparable symptomatic and functional improvement.

Kinematics and aerodynamics of the greater horseshoe bat, Rhinolophus ferrumequinum, in horizontal flight at various flight speeds.

The kinematics and aerodynamics of the greater horseshoe bat, Rhinolophus ferrumequinum, in horizontal flight at a range of velocities are described. As flight speed increases there is a gradual change in the bat's wingbeat kinematics, wingbeat frequency decreasing and wingbeat strokeplane angles increasing. Associated with these changes are changes in the wings' incidence angles, particularly during the upstroke. At low speeds these are large and negative, suggesting thrust generation, while at high speeds these are positive and large, indicating that weight support and negative thrust are being generated. The change from one kinematic pattern to the other occurred gradually. The possible energetic and aerodynamic reasons for these changes are discussed.

Percutaneous transluminal angioplasty of coronary saphenous vein bypass grafts.

Between December 1981 and August 1983, percutaneous transluminal angioplasty of saphenous vein grafts was performed in 14 men and 4 women, selected because of recurrent anginal symptoms and graft stenosis. The interval from bypass to angioplasty was 41 +/- 36 months. Of 24 lesions, 9 were at the proximal anastomosis, 13 in the distal segment and 2 in the middle segment of the vein graft. The primary success rate was 79%. Failure to cross the stenosis occurred in three patients and failure to dilate in one. The stenosis was reduced from a mean of 82% +/- 13% to 26% +/- 15%. No patient required emergency coronary artery bypass grafting but two underwent elective grafting after the angioplasty had failed. No patient sustained a Q-wave myocardial infarction and all who had a successful angioplasty were asymptomatic or much improved after the procedure. Angiographic follow-up was available in 12 of 14 patients (86%). Six patients had significant symptoms (Canadian Cardiovascular Society class II to III) and five of these had evidence of restenosis. Among the six patients who were asymptomatic, two had angiographic evidence of restenosis. The overall rate of restenosis was 58% (7 of 12). Repeat angioplasty was successful in three of the five patients in whom it was attempted. The authors conclude that percutaneous transluminal angioplasty of a saphenous vein graft for a localized area of stenosis is effective and safe, but there is a high rate of restenosis that possibly is due to intimal fibrous proliferation in saphenous vein grafts.

The use of dextran-40 during percutaneous transluminal coronary angioplasty: a report of three cases of anaphylactoid reactions--one near fatal.

Successful percutaneous transluminal coronary angioplasty is achieved by fracture of the atheromatous plaque and perhaps dilatation of the arterial walls to increase the luminal diameter of the artery. Because this "controlled" injury stimulates platelet adhesion on the subendothelial matrix, the use of dextran-40 in addition to heparin has been advocated. The overall incidence of Dextran-induced anaphylactoid reactions at our institution was 0.6% and of severe life-threatening reactions, 0.2%. With the recent doubts cast on the efficacy of dextran-40, the question arises regarding its routine use in PTCA.

Acute coronary artery occlusion during percutaneous transluminal coronary angioplasty treated by redilation of the occluded segment.

Acute occlusion of a coronary artery during percutaneous coronary angioplasty usually results in unremitting ischemia requiring emergency surgical intervention. Seven patients are described, in whom complete occlusion occurred during coronary angioplasty as a result of coronary artery dissection. Despite this, it was possible to reintroduce the balloon catheter immediately and redilate the vessel with abrupt reversal of clinical and electrocardiographic manifestations of ischemia. Six patients had no subsequent evidence of myocardial infarction. The seventh had a slight elevation of serum creatine kinase and transient electrocardiographic changes. All patients were discharged from the hospital without further intervention. Four patients had elective coronary artery bypass surgery (greater than 4 weeks after angioplasty) and three have remained asymptomatic or in improved condition since the coronary angioplasty. It is concluded that sudden occlusion of a coronary artery during coronary angioplasty can be safely treated by redilation in the acute stage.