Use of the thermal laser effect of laser irradiation for cardiovascular applications exemplified by the Nd:YAG laser

Techniques of percutaneous transluminal application of laser energy for vessel recanalization have been used clinically since 1983. The commonly used Nd:YAG and argon lasers achieve ablation of atherosclerotic plaques by thermal action (vaporization). In order to reduce undesirable thermal damage in the neighborhood of the target tissue and to avoid vessel perforation, optimal irradiation parameters, modified (atraumatic) fiber tips (hot tips, sapphires), and steerable catheter systems needed to be implemented. Favorable results from peripheral application have encouraged use in the coronary circulation. More recently, coagulative tissue effects of circumferential irradiation of the vessel wall during balloon dilatation have been used for stabilization of acute and late results after mechanical balloon angioplasty. Enhancement of the differential light absorption of atherosclerotic plaque by use of biological dyes may further improve selective intravascular laser application. Intraoperative ECG-guided laser coagulation of arrhythmogenic areas of myocardium is a method for treatment of malignant arrhythmias. Transluminal non-operative application of myocardial laser photocoagulation has now been tested experimentally and shown to be safe and effective. There was no arrhythmogenicity or thermal damage of coronary arteries associated with this method. Innovative techniques such as nanosecond pulsed excimer lasers (athermal action) and development of "intelligent" lasers--which are equipped with spectroscopy-guided feedback systems for plaque recognition--have opened new perspectives and will further improve safety and efficacy of clinical laser application. However, according to current experience, the thermally acting Nd:YAG laser is an effective and versatile mode of laser therapy for selected cardiovascular indications.     

Quantitation of colonic injury from argon laser, neodymium: YAG laser and monopolar electrocautery applied to flat mucosa and small sessile polyps of the canine colon

This study determined the optimum laser energy for ablation of colonic mucosal lesions and small sessile polyps in the canine colon. Neodymium (Nd):YAG laser, argon laser, and monopolar electrocautery were applied to exposed canine colonic mucosa for various application times at various power settings. At the minimum energy level necessary to ablate mucosa, the Nd:YAG laser caused greater muscularis injury than the argon laser and monopolar electrocautery. At higher energy levels, monopolar electrocautery and Nd:YAG laser caused greater muscularis injury than argon laser. Small surgically created polyps in the canine colon were ablated endoscopically with the three energy sources. Single-session complete polyp ablation occurred most frequently with Nd:YAG laser and least frequently with argon laser. The depth of tissue injury beneath polyp ablation sites was least with argon laser and greatest with Nd:YAG laser. This study suggests that the argon laser is safer than the Nd:YAG laser or monopolar electrocautery for coagulation of flat colonic mucosal lesions. Although the argon laser is safer for the coagulation of small sessile colonic polyps, it may be less effective than monopolar electrocautery or the Nd:YAG laser for the single-session fulguration of polyps greater than 5 mm in diameter.     

A Novel Catheter Design for Laser Photocoagulation of the Myocardium to Ablate Ventricular Tachycardia

Nd:YAG laser energy has been proposed as an alternative to radiofrequency energy for ablation of ventricular tachycardia (VT) associated with coronary artery disease (CAD) in an effort to increase lesion size and success rates. However, issues of catheter design to maintain flexibility and ensure adequate tissue contact have hindered development of laser catheters.We developed and tested a prototype 8 Fr. steerable catheter with a flexible and extendible tip (designed to ensure tissue contact and efficient ventricular mapping), which projects the laser beam through a side port containing a lens-tipped optical fiber that rests against the endocardial surface. The catheter has a channel for simultaneous saline irrigation to displace the interceding blood and discharge a laser beam between two electrodes for bipolar mapping and a thermocouple for temperature monitoring. The catheter was tested on bench top using the epicardial surface of freshly slaughtered bovine hearts and in vivo using six anaesthetized closed-chest sheep. In vitro experiments demonstrated that lesion size increased linearly with applied power up to 40 watts. When compared to radio frequency, laser energy penetrated more deeply into the myocardium. In the in vivo studies, using increasing powers of up to 40 watts for application times of 60 to 120 seconds created circular or elliptical lesions with surface dimensions up to 12 mm × 12 mm and depth of 9 mm (full LV wall thickness with a mean lesion diameter of 9.9 ± 5.2 mm and depth 5.8 ± 3.2 mm). Most lesions, 16 total in both right and left ventricular walls were transmural or near transmural in thickness. Lesions demonstrated coagulation necrosis with smooth well-demarcated borders. No animal suffered cardiac perforation, hypotension, hemopericardium, damage to cardiac valves, or cavitation effect from any of the ablations. Runs of VT were seen during energy application at the highest laser outputs in two animals.In conclusion, this catheter design provides effective endocardial delivery of laser energy and is capable of creating transmural or nearly transmural lesions in vivo and in vitro, thereby potentially increasing the efficiency of VT ablation in CAD patients.     

Laser photocoagulation for gastrointestinal bleeding.

Endoscopic laser photocoagulation is one of the exciting developments in the field of gastrointestinal endoscopic therapy. However, much work needs to be done before these techniques should be allowed to proliferate into widespread use. There are few controlled randomized clinical studies evaluating any endoscopic treatment of bleeding, including argon laser and Nd:YAG laser photocoagulation. Despite this, uncontrolled clinical trials of both argon and Nd:YAG laser photocoagulation have begun. Laser photocoagulation of bleeding upper gastrointestinal lesions should be considered a procedure in an experimental stage of development, to be performed only under protocol studies at endoscopic research centres. Only after this or any other haemostatic technique has been proven effective and safe in thorough animal trials and then in controlled clinical trial should it be considered ready for general clinical use.     

Argon vs. neodymium YAG laser photocoagulation of experimental canine gastric ulcers

A neodymium YAG (Nd:YAG) laser was evaluated in a dog ulcer model used in the same manner as is recommended for bleeding patients (power 55 W, divergence angle 4 degrees, with CO2 gas-jet assistance). The experiments were performed during sterile laparotomy in heparinized dogs. Bleeding gastric ulcers were photocoagulated until bleeding stopped and then examined histologically 7 days later when depth of tissue injury was maximal. In the first series of experiments, the Nd:YAG laser was compared with the 7-W argon laser in the same dogs. Both lasers stopped bleeding from all experimental ulcers. The 55-W Nd:YAG laser caused full-thickness injury to the gastric wall beneath 11 of the 14 treated ulcers, whereas the 7-W argon laser caused no full-thickness injury beneath 14 treated ulcers. In a second series of experiments, we tried to determine whether varying exposure times with the 55-W Nd:YAG laser would make it less injurious; it did not. In a third series of experiments, the 55-W Nd:YAG laser was tested with and without CO2 gas-jet assistance in order to determine if this would affect the depth of injury; it did not. In the final series of experiments, the wattage of the Nd:YAG laser was varied to see if this would reduce depth of injury; lower wattage did not stop bleeding, and intermediate and higher wattages did stop bleeding but did not reduce depth of injury. We conclude that the 55-W Nd:YAG laser as it is currently used clinically produces deeper tissue damage than the argon laser in our animal model. This damage is not reduced by changes in power, duration of exposure, or the presence of gas-jet assistance.     

The tissue effect of second generation argon plasma coagulation (VIO APC) in comparison to standard APC and Nd:YAG laser in vitro

BACKGROUND: The aim of this study was to evaluate the effect of 2nd generation argon plasma coagulation (VIO APC) with respect to the tissue destruction capacity, and to compare it with standard APC and Nd:YAG laser. METHODS: 2nd generation APC (VIO APC2, Erbe, Germany), standard APC (APC 300/Erbotom ICC 200, Erbe) and Nd:YAG laser (KTP/YAG XP 800; Laserscope, San Jose, California) were applied in 35 porcine livers. Using APC, power settings (30-120 W), application time (2 and 5 sec) and gas flow (1 and 2 l/min) were varied. Using Nd:YAG laser, 30-60 W were applied (flow 21/min). Diameter and depth of tissue coagulation were evaluated. RESULTS: Using VIO APC, maximum coagulation depth was 6 mm (maximum diameter 15 mm). In comparison to standard APC, the coagulation effect was significantly higher (p < 0.001). There was no significant difference in the mean depth achieved by VIO APC and Nd:YAG laser using 30- 60 W and an application time of 2 sec (p < 0.05). Using maximum energy available for the 2 systems, maximum depth achieved by VIO APC (6 mm) was higher than the one caused by Nd:YAG laser (4 mm). CONCLUSIONS : VIO APC was more effective than standard APC. Using medium power and a limited application time, it was as effective as Nd:YAG laser. The high effectiveness of VIO APC should be a topic of clinical education.     

Laser ablation of human atherosclerotic plaque without adjacent tissue injury

Seventy samples of human cadaver atherosclerotic aorta were irradiated in vitro using a 308 nm xenon chloride excimer laser. Energy per pulse, pulse duration and frequency were varied. For comparison, 60 segments were also irradiated with an argon ion and an Nd:YAG (neodymium:yttrium aluminum garnet) laser operated in the continuous mode. Tissue was fixed in formalin, sectioned and examined microscopically. The Nd:YAG and argon ion-irradiated tissue exhibited a central crater with irregular edges and concentric zones of thermal and blast injury. In contrast, the excimer laser-irradiated tissue had narrow deep incisions with minimal or no thermal injury. These preliminary experiments indicate that the excimer laser vaporizes tissue in a manner different from that of the continuous wave Nd:YAG or argon ion laser. The sharp incision margins and minimal damage to adjacent normal tissue suggest that the excimer laser is more desirable for general surgical and intravascular uses than are the conventionally used medical lasers.     

Site of Accessory Pathway Block After Radiofrequency Catheter Ablation in Patients with the Wolff-Parkinson-White Syndrome

Site of Accessory Pathway Block. Introduction: Recent studies have demonstrated that the most common site of accessory pathway conduction block following the introduction of a premature atrial stimulus during atrial pacing is between the accessory pathway potential and the ventricular electrogram. consistent with block at the ventricular insertion of the accessory pathway. However, no prior study has evaluated the site of conduction block during radiofrequency catheter ablation procedures. Therefore, the objective of this study was to determine the site of conduction block after catheter ablation of accessory pathways by analyzing and comparing the local electrograms recorded before and after radiofrequency energy delivery at successful ablation sites. Methods and Results: The electrograms evaluated in this study were obtained from 85 consecutive patients who underwent successful radiofrequency catheter ablation of a manifest accessory pathway. The 50 left free-wall accessory pathways were ablated using a ventricular approach and the 35 right free-wall or posteroseptal accessory pathways were ablated using an atrial approach. The characteristics of local electrograms recorded immediately before and immediately after successful ablation of the accessory pathway were determined in each patient. The site of accessory pathway block was determined by comparing the amplitude, timing, and morphology of the local eleclrograms at successful sites of radiofrequency catheter ablation before and after delivery of radiofrequency energy. A putative accessory pathway potential was present at the successful target site in 74 of the 85 patients (87%). Conduction block occurred between the atrial electrogram and the accessory pathway potential in 66 patients (78%) and between the accessory pathway potential and the ventricular electrogram in eight patients (9%). The site of block could not be determined in 11 patients (13%) in whom an accessory pathway potential was absent. Conduction block occurred most frequently between the atrial electrogram and the accessory pathway potential regardless of accessory pathway location. No electrogram parameter or accessory pathway characteristic was predictive of the site of conduction block. Conclusion: The results of this study demonstrate that conduction block occurs most frequently between the local atrial electrogram and the accessory pathway potential during radiofrequency catheter ablation of accessory pathways. This is true regardless of whether the accessory pathway is ablated from the atrial or ventricular aspect of the mitral or tricuspid annulus.     

Catheter Ablation with Radiofrequency Energy: Biophysical Aspects and Clinical Applications

Radiofrequency Catheter Ablation. Radiofrequency catheter ablation techniques are becoming increasingly accepted as the therapy of choice for selected patients with symptomatic arrhythmias. The ability to titrate the power output using radiofrequency current has allowed these ablative techniques to be applied safely in a variety of arrhythmias. In many institutions, radiofrequency catheter ablation has now become standard therapy for controlling medically refractory atrial arrhythmias using atrioventricular (AV) junction ablation and for curing AV nodal reentrant tachycardia and supra ventricular tachycardia due to accessory AV connections. This technology is also being used to treat some forms of ventricular tachycardia such as bundle branch reentry ventricular tachycardia, ventricular tachycardia in structurally normal hearts, and with limited success in patients with ventricular tachycardia and coronary artery disease. Advancements in catheter design and energy delivery systems may further expand the use of this form of therapy. (J Cardiovasc Electrophysiol, Vol. 3, pp. 173–186, April 1992)     

Effects of Nd:YAG laser irradiation on ventricular myocardium in dogs using an artificial sapphire tip contact laser catheter]

To apply Nd:YAG laser irradiation through a new sapphire tip contact laser method to catheter ablation in treatment of tachy-arrhythmias, effects of laser irradiation on ventricular myocardium were investigated in 10 mongrel dogs. Nd:YAG lase (1064nm) discharges were delivered to different sites on the endomyocardium at power of 5, 10, 15, 20 or 25w with duration of 3, 5, or 10 seconds (sec.) respectively in closed beating hearts. Histopathologically, the lesion irradiated was clearly demarcated from the normal myocardium by the construction band necrosis zone. The depth of injured myocardium was less than 2mm with 3 sec. irradiations, with 5 sec. from 1 mm to 4 mm in proportion to power increase, with 10 sec. from 3mm to 8 mm in proportion to the power from 5w to 15w and could not be measured in cases of more than 20w irradiations. Although with every irradiation duration, the depth of injury increased in proportion to the power increase. With the same total energy, a longer time of irradiation produced deeper injury than a shorter time. This method makes it easier to keep the laser positioned to target than bare laser, and is suitable for use in catheter ablation.     

Current and future modalities of catheter ablation for the treatment of cardiac arrhythmias

Catheter ablation has proven to be a safe and effective treatment for a wide variety of cardiac arrhythmias. By destroying the critical zone of conductive tissue responsible for impulse generation or propagation, the arrhythmias may be cured. A variety of modalities of catheter ablation have been tested in the past decade. Initially, high energy direct current shocks delivered through a conventional electrode catheter were used. Now, use of radiofrequency energy as a power supply has resulted in higher efficacy and much improved safety of this technique. New approaches including low energy direct current shock ablation, microwave hyperthermic ablation, and laser photocoagulation are being tested, and may result in further refinement of nonsurgical curative therapy of arrhythmias.     

Argon laser ablation of malignant ventricular tachycardia associated with coronary artery disease

The long-term clinical efficacy and safety of intraoperative mapping-guided argon laser ablation alone or in conjunction with standard surgical methods were assessed in 20 consecutive patients with refractory sustained ventricular tachycardia (VT) or ventricular fibrillation. A 15-W argon ion gas laser was used and pulsed laser energy was delivered through a fiberoptic catheter delivery system. Pre- and intraoperative mapping was used to localize the arrhythmogenic tissue. Postoperative clinical, ambulatory electrocardiographic and electrophysiologic evaluations were performed before discharge and at 1 year of follow-up. Thirty-eight VT morphologies were mapped and ablated with laser energy alone (82%), combined laser ablation and mechanical resection (13%) or mechanical resection alone (5%). Concomitant coronary artery bypass surgery was performed in 15 patients and in 1 patient it was performed with mitral value replacement. Postoperative 30-day mortality was 5%. One patient (5%) required postoperative antiarrhythmic drug therapy, and all survivors had suppression of inducible sustained VT at discharge. Mean left ventricular ejection fraction increased from 34 +/- 12% preoperatively to 41 +/- 13% postoperatively (p = 0.001). Efficacy rates for ablation of VT sites associated with anterior myocardial infarction and inferior or posterior myocardial infarction were comparable (100 vs 96%, respectively, p greater than 0.2). At 1-year follow-up no sudden deaths had occurred and total survival rate was 90%. Intraoperative pulsed argon laser ablation alone or in conjunction with standard surgical techniques improves the efficacy of surgical ablation procedures for VT or ventricular fibrillation and reduces the need for additional postoperative antiarrhythmic drug or device therapy.     

特发性左室流出道室性心律失常的心电图特点

探讨特发性左室流出道室性心律失常患者的心电图特点。对 7例特发性左室流出道室性早搏 (简称室早 )、室性心动过速 (简称室速 )患者进行心电图分析 ,并行心内电生理检查及射频消融治疗 ,同时对 10例预激综合征患者成功消融房室旁道后行主动脉瓣上及瓣下起搏 ,记录同步 12导联起搏心电图。对比分析两组病例体表心电图QRS波图形特点。结果 :7例左室流出道室早、室速患者经心内电生理检查证实 6例起源于冠状动脉窦内 ,1例起源于左室流出道主动脉瓣右瓣下方 ,所有患者经射频消融成功治疗室性心律失常。对照组 10例在主动脉瓣下起搏(其中 6例同时在主动脉瓣上起搏 )获得同步 12导联起搏心电图。两组病例体表心电图共同特点为 :QRS波额面电轴向下 ,Ⅱ、Ⅲ、aVF导联主波向上 ,QRS波在V2 或V3 前移行为Rs或R型。结论 :左室流出道为特发性室早、室速发生部位之一 ,体表心电图有其独特性 ,导管射频消融治疗安全有效。     

Palliative laser therapy for tumours of the gastrointestinal tract.

The argon ion and Nd: YAG lasers were used initially in the mid 1970s to produce haemostasis in acutely bleeding peptic ulcers. With the evolution of treatment techniques, the main area of use of the Nd: YAG laser has now become the palliation of upper and lower GI malignancies. Thermal ablation of tumours may be achieved endoscopically by non-contact laser application at high power, or in the contact mode using artificial sapphire probes at much lower energy levels. Still lower powers can be employed therapeutically using interstitial hyperthermia, and this is best applied endoscopically to exophytic tumour nodules in the gut lumen or to tumours localized ultrasonically in solid organs, such as the liver or pancreas. PDT involves destruction of previously photosensitized tumours by the cytotoxic action of singlet oxygen released on exposure of the neoplastic tissue to light of an appropriate wavelength. Although the theory is attractive, the available experimental and clinical information suggests that treatment should, for the present, be confined to small or early malignancies whose depth of invasion can be verified by endoscopic ultrasound or other imaging techniques. PDT carries the biological advantage of healing by regeneration with preservation of connective tissue stroma, while the Nd: YAG laser causes destruction by thermal coagulation or vaporization and subsequent healing by fibrosis. Laser therapy of GI tumours expands the range of therapeutic endoscopic procedures in a relatively safe and readily repeatable manner which achieves high patient tolerance. By reducing morbidity, mortality and time spent in hospital, it offers significant advantages in the palliative treatment of conditions previously managed by conventional surgery, and also offers opportunities for treatment of previously inoperable disorders. Developments in laser technology and diagnostic imaging techniques are likely to promote laser therapy in the future as a primary treatment modality.     

Histological and angiographic effects of a pulsed holmium:YAG laser in normal and atherosclerotic human coronary arteries and aorta.

OBJECTIVE: The aims were (1) To determine the histological and angiographic effects of holmium:YAG laser energy delivered through clinical multifibre laser catheters on fresh cadaveric coronary arteries; and (2) to relate the placement of optical fibres in the catheter to patterns of tissue ablation in cadaveric aorta. METHODS: Eight fresh cadaveric hearts and segments of aorta were used. Hearts were mounted on a new pressure perfusion device. The laser catheter was delivered over a guidewire in the lumen until it met an area of resistance. The coronary artery lumen was perfused at approximately 100 mm Hg mean pressure. These arterial areas were identified on angiography, marked, and then exposed to laser energy in the range 600-3000 mJ.mm-2. Normal and atherosclerotic areas of fresh cadaveric aortic strips were exposed to increasing laser energies using either constant or increasing fluence. Coronary arteries were pressure perfused with formalin for 18-24 h at 100 mm Hg mean pressure, and aortic strips were immersed in 5% formalin. Light and scanning electron microscopy studies were carried out. RESULTS: There were no perforations or dissections by angiography in the fresh coronary arteries. One of 15 normal coronary artery segments and 10 of 16 of the pressure perfused, fixed, atherosclerotic coronary artery segments showed thermal changes associated with atherosclerotic plaque ablation. In aortic tissue, thermal effects extended 0 to 0.6 mm lateral to the ablated crater. Acoustic effects were seen only in the aortic strips after ablation at fluences > 1000 mJ.mm-2. The "dead spaces" around the optical fibres in the catheter resulted in significant amounts of coagulated tissue fragments remaining in the crater. CONCLUSIONS: Holmium:YAG laser energy delivered through multifibre catheters ablated atherosclerotic tissue in coronary arteries with minimal damage to the normal walls. The cadaveric coronary artery perfusion apparatus is useful for assessing catheter delivery and mobility and the effects of laser energy on the coaxially orientated normal and atherosclerotic coronary arterial wall.     

Neodymium:yttrium-aluminum garnet contact laser ablation of Barrett's high grade dysplasia and early adenocarcinoma

OBJECTIVES: We describe the efficacy and safety of neodymium:yttrium-aluminum garnet (Nd:YAG) contact laser ablation of Barrett's high grade dysplasia (HGD) and/or early adenocarcinoma. METHODS: Consecutive Barrett's patients in whom HGD or adenocarcinoma was detected were eligible. Radial array echoendosonography and high frequency catheter probe ultrasonography were performed. Patients were excluded if ultrasound revealed the presence of Barrett's cancer with regional lymph nodes or celiac trunk metastases or extension of the tumor into superficial submucosa (T1sm1) or greater. Nd:YAG laser used quartz contact probes, with all Barrett's epithelium targeted at each session. Complete ablation was confirmed with Lugol's iodine chromoendoscopy followed by surveillance biopsies of the neosquamous epithelium. Adverse events were ascertained by scheduled telephone contact interviews. RESULTS: A total of 36 patients with HGD/adenocarcinoma were evaluated at our center, 17 of whom met all inclusion criteria. Of the patients, 14 have remained in the study, and all have had successful elimination of HGD and cancer. In addition, 11 patients (78.6%) achieved complete endoscopic and histological ablation of all Barrett's tissue. Two patients (14.3%) achieved 95% destruction of Barrett's with residual metaplastic columnar epithelium containing goblet cells without dysplasia. The remaining patient has obtained 75% ablation of Barrett's, with residual metaplastic columnar epithelium harboring Barrett's with low grade dysplasia. Major complications included two esophageal strictures (11.8%) and one mild upper GI bleed (5.9%). CONCLUSIONS: This preliminary experience with Nd:YAG contact laser for the treatment of Barrett's HGD and early superficial cancers seems promising. The need for additional controlled trials with larger numbers of patients with longer follow-up, as well as consideration of a head-to-head trial with Photofrin photodynamic therapy, is warranted.     

Endoscopic therapy for upper-GI vascular ectasias

BACKGROUND: Upper-GI vascular ectasias, including angiodysplasia and gastric antral vascular ectasia may present with either acute or chronic bleeding. Endoscopic thermal modalities have been used to control acute bleeding and reduce transfusion requirements. METHODS: Endoscopic experience was reviewed for a 6-year period during which 32 patients requiring blood transfusions for upper-GI angiodysplasia or gastric antral vascular ectasia were evaluated. Patients seen during the first 5 years were treated with either Nd:YAG laser photocoagulation or multipolar electrocoagulation. During the most recent 12 months, all patients were treated by argon plasma coagulation. Response to therapy was assessed by change in mean Hb and transfusion requirements. RESULTS: Overall, 16 patients were treated by laser photoablation alone; 9, argon plasma coagulation with or without laser; and 7, multipolar electrocoagulation with or without laser. Mean follow-up for all patients was 19 months. After therapy, mean Hb concentration rose from 76 to 114 g/L for patients with gastric antral vascular ectasia and from 85 to 118 g/L for those with angiodysplasia. Endoscopic therapy abolished or reduced transfusion requirements in 93% of patients with gastric antral vascular ectasia and 76% with angiodysplasia. Patients with gastric antral vascular ectasia required a mean of 6 treatment sessions, while those with angiodysplasia required one to two sessions. CONCLUSIONS: Endoscopic thermal ablation effectively controls acute bleeding and reduces transfusion requirements in most patients with upper-GI vascular ectasias. Patients with gastric antral vascular ectasia require significantly more treatment sessions to achieve this effect.     

Experimental and clinical studies of using Nd: YAG laser via domestic metal cap and sapphire tip delivery systems

Sixteen segments of normal human cadaver aorta were irradiated by Nd: YAG laser beam delivered via domestic metal cap and sapphire tip fiber systems. Results revealed that the adherence to target tissue and tissue damage were more apparent with metal caps than those with sapphire tips. Furthermore, the latter had smoother edges of ablation crater less carbonization layers and smaller thermal necrotic zones. The delivery systems were used to perform laser angioplasty in 2 iliac and 5 coronary atherosclerotic arteries and all achieved immediate recanalization.     

Radiofrequency catheter ablation of ventricular tachycardia in patients without structural heart disease.

BACKGROUND. Radiofrequency energy has been used safely and successfully to eliminate accessory pathways in patients with the Wolff-Parkinson-White syndrome and the substrate for atrioventricular nodal reentrant tachycardia. However, this form of ablation has had only limited success in eliminating ventricular tachycardia in patients with structural heart disease. In contrast, direct-current catheter ablation has been used successfully to eliminate ventricular tachycardia in patients with and without structural heart disease. The purpose of this study was to test whether radiofrequency energy can safely and effectively ablate ventricular tachycardia in patients without structural heart disease. METHODS AND RESULTS. Sixteen patients (nine women and seven men; mean age, 38 years; range, 18-55 years) without structural heart disease who had ventricular tachycardia underwent radiofrequency catheter ablation to eliminate the ventricular tachycardia. Two patients presented with syncope, nine with presyncope, and five with palpitations only. Mean duration of symptoms was 6.7 years (range, 0.5-20 years). Radiofrequency catheter ablation successfully eliminated ventricular tachycardia in 15 of 16 patients (94%). Sites of ventricular tachycardia origin included the high right ventricular outflow tract (12 patients), the right ventricular septum near the tricuspid valve (three patients), and the left ventricular septum (one patient). The only ablation failure was in a patient whose ventricular tachycardia arose from a region near the His bundle. An accurate pace map, early local endocardial activation, and firm catheter contact with endocardium were associated with successful ablation. Radiofrequency ablation did not cause arrhythmias, produced minimal cardiac enzyme rise, and resulted in no detectable change in cardiac function by Doppler echocardiography. CONCLUSIONS. Radiofrequency catheter ablation of ventricular tachycardia in patients without structural heart disease is effective and safe and may be considered as early therapy in these patients.     

经冠状静脉窦射频导管消融房室旁路的疗效和安全性

目的 :探讨经冠状静脉窦低能量射频导管消融房室旁路的适应证、疗效和安全性。　　方法 :2 2例左侧房室旁路患者先经心内膜射频导管消融 ,不成功改由经冠状静脉窦标测途径。　　结果 :2 2例患者全部成功 ,17例 (77.3% )成功靶点与冠状静脉分支或畸形有关。 15例有效靶点记录到振幅较大的房室旁路电位 ,其振幅于 A波和 V波之比大于 1,前传 V波和逆传 A波较心内膜标测分别提前 2 6 .1± 5 .1m s和 2 2 .5±9.2 m s。　　结论 :低能量冠状静脉窦射频导管消融可以安全、有效的阻断房室旁路。