Biomedical subjects
Publications and source records attributed to H V Anderson.
The underlying cause of acute myocardial infarction can now be effectively treated with thrombolytic agents, thereby increasing myocardial salvage and reducing mortality. Clinicians should always be aware of the risk-to-benefit ratio in treating patients with thrombolytic agents and treat each patient on an individual basis.
This study was performed to define the in-hospital and late clinical outcome at 5 years in 430 patients who had a failed elective percutaneous transluminal coronary angioplasty (PTCA) and underwent coronary artery bypass graft (CABG) surgery during their hospitalization. This group comprised 5.9% of 7,246 patients undergoing elective PTCA. CABG surgery was performed in 346 patients with ongoing myocardial ischemia (80.5%) and in 84 patients without ischemia (19.5%). Their mean age was 56 +/- 9 years, and 76.3% were male. One-vessel disease was present in 72.3%, and the mean left ventricular ejection fraction was 59 +/- 11%. Overall, 1.9 +/- 0.9 bypass grafts were placed. There was increased use of the internal thoracic artery in the nonischemic group. A new nonfatal postprocedural Q wave myocardial infarction occurred in 21.2% and occurred more frequently in the ischemic (25.4%) than in the nonischemic (3.6%) group (p less than 0.0001). There were six in-hospital deaths (1.4%), an incidence that did not differ between the two groups. Follow-up was 99.8% complete. There were 25 deaths (93.2 +/- 1.5%, 5-year survival), including 16 of cardiac cause (95.3 +/- 1.3%, 5-year cardiac survival). Q wave myocardial infarction occurred in 111 patients (91 in-hospital), and freedom from cardiac death or nonfatal myocardial infarction at 5 years was 71 +/- 3%. In the group going to CABG surgery with ongoing ischemia, the 5-year cardiac survival was 94.9 +/- 1.6%, and in the group without ischemia, the corresponding survival was 96.2 +/- 2.2%. By multivariate analysis, the presence of preoperative myocardial ischemia, pre-PTCA diameter stenosis less than 90%, and the presence of multiple-vessel disease correlated with the occurrence of cardiac death or nonfatal myocardial infarction at 5 years. At this large-volume center with extensive PTCA operator and surgical experience, the excellent survival and low event rates over 5 years support the concept that despite the failed elective PTCA procedure, there was little effect on long-term survival provided the patient underwent prompt successful surgical revascularization.
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To identify the correlates of a second restenosis after repeat percutaneous coronary angioplasty, the records of 384 patients with single vessel disease who underwent repeat angioplasty for restenosis complicating a first elective angioplasty were examined. A second restenosis occurred in 47 (31%) of 151 patients having angiographic follow-up. Univariate correlates of a second restenosis were an interval between the first and second angioplasty less than 5 months (41 versus 20% of patients had restenosis, p less than 0.01), male gender (35 versus 12%, p less than 0.05), lesions length greater than or equal to 15 mm before the second angioplasty (62 versus 28%, p less than 0.05), diameter stenosis greater than 90% before the second angioplasty (67 versus 29%, p less than 0.05), final gradient greater than 20 mm Hg after the second angioplasty (52 versus 28%, p less than 0.05) and an additional site requiring dilation at the time of the second angioplasty (50 versus 29%, p = 0.10). Multivariate predictors of a second restenosis were an interval of less than 5 months between the first and the second angioplasty (p = 0.001), male gender (p = 0.001), lesion length greater than or equal to 15 mm before the second angioplasty (p = 0.001) and the need to have an additional site dilated at the time of the second angioplasty (p = 0.002). Patients at increased risk of restenosis after the second angioplasty can be identified and may serve as a useful population for intervention studies.
This study was performed to define the 5 year clinical status of 427 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) in 1981. Their mean age was 54 +/- 10 years (+/- 1 SD). Sixty-one percent had unstable angina, 23% had prior myocardial infarction, 86% had one-vessel disease, and 92% had normal left ventricular function. Sixty-seven percent of patients had left anterior descending artery stenosis. Angiographic success was achieved in 84% of patients. Coronary bypass surgery was required in 9.6% of patients, in 5.9% as an emergency procedure. There were no in-hospital deaths. Follow-up at 5 years was 100% complete. There were 15 late deaths (96.3 +/- 1.0% survival), including seven of cardiac cause (98.1 +/- 0.7% cardiac survival). Myocardial infarction occurred in 24 patients (94% freedom from myocardial infarction), coronary bypass surgery was required in 63 (84% freedom from bypass surgery), and 365 patients (85%) were asymptomatic at follow-up. At 5 years, 83 patients (20%) had required an additional PTCA. Unstable angina pectoris and proximal left anterior descending coronary artery stenoses were present in 162 patients. The overall survival and cardiac survival in this subset was 94.4 +/- 1.8% and 98.1 +/- 1.1%, respectively. The excellent survival and low event rates over 5 years in this population support the concept that PTCA is safe and effective for patients with symptomatic angina pectoris, single-vessel disease, and normal left ventricular function.
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Intracoronary delivery of argon laser energy was studied in eight anesthetized mongrel dogs. A No. 4.5 French single lumen catheter, with steerable guidewire and an optical fiber, was introduced through a Judkins-type femoral-coronary guiding catheter into three left anterior descending and eight left circumflex coronary arteries. A total of 65 laser energy exposures were made coaxially at 24 sites in the 11 arteries. At five sites, angiographically evident arterial perforation occurred with the first laser exposure, while at seven sites multiple laser exposures were made without angiographically evident perforation. All eight dogs remained hemodynamically stable, and were electively killed 5 +/- 1 hours following the procedure. Sections of myocardium from territories supplied by treated arteries demonstrated minimal or no pathology in 10 cases, while one territory had a small zone of early myocardial necrosis. This study suggests that standard coronary artery catheterization techniques can be used to introduce and position a steerable guidewire and an optical fiber in canine coronary arteries. Laser energy can repeatedly be delivered coaxially. Short-term deleterious effects may be reduced or eliminated, and exposure of blood elements to argon laser energy does not appear to create debris.
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Imprecision in guiding and positioning is a recurring problem with fiberoptic delivery of laser energy (E) in small arteries. Manipulation can produce mechanical perforation of the vessel, and noncoaxial alignment can result in thermal perforation at relatively low laser energy levels. A No. 4.5 French single-lumen catheter was designed to accommodate both a steerable guidewire and an optical fiber. It was passed, under fluoroscopic control, into the abdominal aorta in 18 atherosclerotic rabbits. Argon laser energy was delivered coaxially at three sites in each of 14 rabbits (total = 42 sites); four rabbits were controls. Laser power levels (1 to 6 W) and exposure times (20 to 60 seconds) were varied. Energy level in joules (J) was calculated for each exposure. Saline flush at 25 ml/min was delivered through the catheter during laser exposures. Angiographic or microscopic evidence of vessel perforation was observed at 10 sites (E = 174 +/- 108 J). Another six sites exhibited microscopic laser effect only, without evidence of vessel perforation (E = 155 +/- 91 J). The remaining 26 sites exhibited no effects of laser energy (E = 117 +/- 92 J). No angiographically visible perforation occurred with E less than 120 J. This study suggests that a fiberoptic catheter with steerable guidewire allows safer intravascular manipulation of optical fibers, improves coaxial alignment in the arterial lumen, and may permit substantial laser energy delivery into atherosclerotic arteries.
Obstruction to blood flow is accompanied by a pressure gradient across the obstructed site. In certain clinical settings, magnitude of pressure gradient has been used to judge severity of obstruction, and gradient reduction to judge success of an interventional procedure. In percutaneous transluminal coronary angioplasty (PTCA) the relationships between transstenotic pressure gradient, diameter stenosis, and lesion length are imprecisely known. We therefore examined 4263 sets of measurements in patients who underwent PTCA on single, discrete coronary arterial lesions. Multivariate regression analysis demonstrated that pressure gradient was artifactually elevated by about 12 mm Hg at low values of diameter stenosis but increased by the 4th power of stenosis as expected from fluid dynamics models. Pressure gradient was dampened and relatively constant at values of diameter stenosis of 60% or higher, probably because of total or near-total occlusion of the artery. Lesion length was not found to influence pressure gradient. Reductions in diameter stenosis (delta D) and pressure gradient (delta G) were related nonlinearly, with delta D proportional to the square root of delta G, suggesting that a reduction in gradient is directly proportional to an increase in cross-sectional area of the stenosis. The predictive value of final post-PTCA pressure gradients was found: a final gradient of 15 mm Hg or less predicted a final post-PTCA diameter stenosis of 30% or less, with 75% sensitivity and 29% specificity (p less than .01). The results of this study suggest that (1) pressure gradient as currently measured during PTCA is related to diameter stenosis but not to lesion length (2) reductions in pressure gradient and diameter stenosis are nonlinearly related.(ABSTRACT TRUNCATED AT 250 WORDS)
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Three distinct periods in catheter design have been identified since the advent of percutaneous transluminal coronary angioplasty (PTCA) in 1977. In the first period PTCA was performed using a double-lumen balloon catheter that had a fixed, flexible guidewire at the tip. In the second period, an independent, steerable guidewire and the steerable catheter system were used. In the third period, low-profile catheters were introduced. A total of 2,969 patients who had single-vessel PTCA of a native coronary artery was separated into groups according to the period during which PTCA was performed. Introduction of the steerable catheter system was accompanied by improvement in primary success rate in PTCA attempts on the right coronary artery (78% vs 88%, p less than 0.005). Introduction of the low-profile catheter was accompanied by improved primary success in PTCA attempts on the left anterior descending coronary artery (LAD) (90% vs 94%, p less than 0.005). The percentage of PTCA attempts on the LAD decreased over the 3 periods (70% to 60% to 56%), while the percentage of attempts on the left circumflex artery increased (7% to 12% to 16%). Before steerable and low-profile catheters were used, there were significant differences in ability to reach and cross stenoses among the 3 major coronary arteries. These differences no longer exist. These results indicate that technical improvements and operator experience have made stenoses in all 3 major coronary arteries equally accessible to dilatation catheters and that primary success rates and reasons for failure in these arteries are now similar.
Perfusion of the coronary artery distal to an occluding angioplasty balloon was performed in 34 patients undergoing coronary angioplasty (PTCA). A randomized crossover study was employed using two exogenous substances as perfusates: lactated Ringer's solution (LR) and a fluorocarbon emulsion (FL), Fluosol-DA 20%. Both substances are electrolyte solutions, but the FL will dissolve more oxygen than the LR. During two attempted coronary artery occlusions of 90 seconds each, we perfused through the central lumen (guidewire channel) of the PTCA catheter at 60 ml/min. With FL perfusion the mean time to onset of angina after occlusion was delayed (41 +/- 21 vs 33 +/- 16 seconds, mean +/- SD; p less than 0.05), the mean duration of angina was shortened (77 +/- 58 vs 92 +/- 70 seconds, p less than 0.05), and the rise in the ST segment of the ECG was reduced (0.15 +/- 0.24 vs 0.2 +/- 0.23 mV, p less than 0.001) when compared to LR perfusion. Balloon occlusion time was able to be extended with FL perfusion (71 +/- 22 vs 59 +/- 22 seconds p less than 0.001). These results indicate that perfusion of the distal coronary artery is possible during PTCA and can reduce ischemia during a prolonged balloon occlusion time.
We studied 986 patients who underwent follow-up angiography after successful percutaneous transluminal coronary angioplasty (PTCA) to determine the influence of uncomplicated intimal dissection on restenosis rate. Angiographic evidence of intimal dissection after PTCA was present in 248 patients or 25%. After a mean follow-up time of 7 +/- 5 months (SD) the restenosis rate in patients without intimal dissection was 30% compared with 24% in patients with intimal dissection (p = .08). Patients with available transstenotic pressure gradients were divided according to the hemodynamic result into two subgroups: those with final gradients at the conclusion of PTCA of 15 mm Hg or less (n = 638) and those with gradients greater than 15 mm Hg (n = 244). Patients with intimal dissection had a significantly lower restenosis rate than patients without intimal dissection if the final gradient was 15 mm Hg or less (19% vs 28%; p less than .05). If the final gradient was greater than 15 mm Hg, the presence or absence of intimal dissection had no significant influence on restenosis rate, which was 35% and 39%, respectively (p = NS). We conclude that an uncomplicated intimal dissection after a successful coronary angioplasty has no adverse influence on angiographic restenosis. An excellent angiographic long-term outcome can be expected if the intimal dissection is associated with a favorable hemodynamic result.
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