ISSN:0896-4327    

DOI:10.1111/j.1540-8183.1990.tb00980.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

During the initial application of percutaneous transluminal coronary angioplasty (PTCA), experience was concentrated in the hands of relatively few operators at a small number of centers. With relatively crude equipment by today's standards, these operators established the current levels of excellence of PTCA by careful patient selection and procedural skill. These operators taught that the “learning curve” of PTCA consisted of two parts, an initial steep upward slope composed of careful patient selection and procedural skill, and a flatter plateau phase which centered on assimilating gradual technical development. As PTCA technology advanced, there has been a suggestion that similar success rates of PTCA could be achieved by lower frequency operators. This concept implies that technical improvements have diminished the importance of operator skill and experience prerequisite to perform “routine” cases. The purpose of this article is to review the initial two “steps” of the learning curve of PTCA and to discuss additional levels of development required to become an interventional cardiologist. To facilitate understanding, I have chosen the staircase as a model. Each step will b

ISSN:0896-4327    

DOI:10.1111/j.1540-8183.1990.tb00981.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Heparin therapy for patients who have undergone thrombolytic therapy of acute myocardial infarction is logical, and several trials suggest a benefit. However, in the light of the clear adjuvant benefit of aspirin, and the failure of large clinical trials to demonstrate clinically important benefits of heparin, it is not possible to make sound recommendations as to the clinical value of adjuvant heparin therapy. The possible inadequacies in previous study designs, and the persisting suggestions of beneficial effects from heparin, indicate that further trials are required and will be done to resolve this therapeutic uncertainty.

ISSN:0896-4327    

DOI:10.1111/j.1540-8183.1990.tb00982.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

During a balloon angioplasty procedure, cardiac interventionalists frequently have difficulty passing standard guide wires into coronary arteries with chronic total occlusion. In the past year, we encountered eight patients with occluded coronary arteries where standard guide wires were tried (average duration 15.5 minutes) but were unsuccessful. Application of a 0.025–0.035‐inch hydrophilic guide wire was then attempted and was successful in recanalizing seven of the eight coronary occlusions (average duration 3.9 minutes). The channel created by the hydrophilic guide wire remained patent after its removal and permitted subsequent balloon angioplasty to be performed. Thus, in some patients with coronary occlusion where difficulty in guide wire passage is encountered, the application of a hydrophilic guide wire for crossing the occlusion and facilitating PTCA should be considered. However, a larger clinical series will be needed to determine the safety and efficacy of this techni

ISSN:0896-4327    

DOI:10.1111/j.1540-8183.1990.tb00983.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Some physical concepts of laser‐tissue interactions that occur in 308‐nm excimer laser angioplasty are addressed. Monte Carlo numerical computations were used to analyze the light fluence rate distributions resulting from finite diameter laser beams incident on tissue, as applied by fiber‐optic light delivery catheters. The fluence rate at the inside part of the tissue surface from a 0.2‐mm diameter fiber emitting 308‐nm light, is increased more than twice relative to the incident power density. The light fluence rate distribution inside the tissue spreads very little outside the incident beam diameter. Therefore, the distributions from different fibers in multifiber catheters will not overlap unless the fibers are very close together. The maximum fluence rate decreases with decreasing beam diameters. Ablation of tissue by a 308‐nm excimer laser delivery system in contact with the tissue resulted in a damage zone adjacent to the crater wall, due to expansion of the gaseous debris trapped under the tip of delivery system. In case of contact irradiation, the ablation was more efficient than in case of noncontact irradiation. Direct temperature measurements during excimer laser ablation by an infared (IR) camera showed that temperature accumulation will occur when a sequence of pulses is applied at frequencies of at least 5 Hz. The temperature rise above ambient under circumstances simulating clinical conditions is measured to

ISSN:0896-4327    

DOI:10.1111/j.1540-8183.1990.tb00984.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Laser angioplasty with modified fiber tips has become a common procedure for the recanalization of totally occluded peripheral arteries. We evaluated the contribution of optical, thermal, and mechanical effects to the mechanism of recanalization of various probes, theoretically and experimentally. Temperature behavior and tissue penetration were measured in relation to axial force exerted by metal laser probes, and optical contact probes coupled to continuous‐wave and pulsed Nd:YAG lasers. Modified fiber tips only penetrated tissue when the contact surface of the probe exceeded a temperature threshold of about 225°C in the fatty tissue model used. Metal laser probes had to be insulated from a liquid environment to attain this temperature. Optical probes needed to have an absorbing layer of carbonized tissue particles to attain this temperature. Tissue penetration by modified fiber tips was force dependent, especially with optical probes. Since the diameter of the probe was larger than the ablative laser beam, the atraumatic probe had to distend soft tissues mechanically. Because the metal laser probes delivered their energy in all directions, undesired heating in the radial direction has to be reduced by motion. The recanalization mechanism of modified fiber tips will depend on the properties of the obstruction. Sometimes the probes will recanalize the obstruction without the use of laser energy (Dotter effect). Moderate heating of the tissue by either direct absorption of light, or by heat conduction from the heated surface of the probe, may help to remodel the obstruction. Tissue temperatures around 100°C will vaporize the water compound, and temperatures higher than 225°C will ablate the solid compounds of the tissue creating a channel. The present unsteerable probes will not penetrate heavily calcified obstructions. Calcific deposits may deflect the probe into the wall with the risk of perfora

ISSN:0896-4327    

DOI:10.1111/j.1540-8183.1990.tb00985.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

We present the results of 12 XeCl laser coronary artery endarterectomies performed in ten patients during CABG surgery. The results are very encouraging and led us to the development of a new and more efficient laser catheter delivery system, which is described in the latter part of this article.

ISSN:0896-4327    

DOI:10.1111/j.1540-8183.1990.tb00986.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The laser‐tissue interaction of the pulsed dye laser was assessed. The histological appearance of the craters showed precise margins with no evidence of collateral thermal tissue damage. The ablation of soft yellow atheroma was consistently about two‐ to threefold that of normal wall, but fibrous white atheroma was resistant to laser energy, and was ablated less than normal wall. The maximum probe tip temperature in air was 197°C, but there was relatively little heating of the coronary artery wall during lasing, and this was minimized by saline perfusion at low flow rates. Lasing produces up to 1012irregularly shaped debris particles per liter. Debris from thrombus and normal aorta caused significant platelet aggregation in vitro, but atheromatous debris did not. In conclusion, the characteristics of the pulsed dye laser are suitable for intravascular lasing, but selective ablation of atheroma was not achi

ISSN:0896-4327    

DOI:10.1111/j.1540-8183.1990.tb00987.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Four men with remote myocardial infarction, left ventricular dysfunction, aborted episodes of sudden death, and recurrent ventricular tachycardia (VT) slowed but not controlled by drugs (mean five trials) were treated with an automatic antitachycardia pacemaker (ATP) (Orthocor II) and an implantable cardioverter‐defibrillator (ICD). Cardiac electrophysiological evaluation had disclosed that the VT could be reliably terminated with decremental extrastimuli. Two defibrillation patches and two epimyocardial sensing electrodes were used. The ATP was implanted separately using a bipolar endocardial electrode. During follow‐up three patients died. One from hepatitis B at two months, and two from sudden cardiac death at 10 and 13 months. One of these deaths was related to ICD battery depletion, the other to a high defibrillation threshold. One patient is alive after 41 months. During the first year postimplant, 359 episodes of VT occurred and there were 105 ICD discharges. The rate and duration of VT episodes terminated by the ICD were 208 ± 7 bpm and 22 ± 9 seconds; and of VT episodes terminated by the ATP were 158 ± 15 bpm and 6 ± 1.8 seconds, respectively. Deleterious device‐to‐device interactions could be avoided. All patients required full antiarrhythmic drug therapy. Conclusions: (1) In highly selected patients, drug‐resistant VT can be terminated by antitachycardia pacing unperceived by the patient; (2) An ICD must provide reliable back‐up defibrillation capability for rapid or accelerated VT or ventricular fibrillation; (3) this initial experience demonstrates the feasibility of utilizing the Orthocor II ATP in combination with an ICD as therapy for refractory clinical

ISSN:0896-4327    

DOI:10.1111/j.1540-8183.1990.tb00988.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY