Thoracoscopic transmyocardial laser revascularization

Thoracoscopic transmyocardial laser revascularization: is prior coronary artery bypass grafting a contraindication?

OBJECTIVE

: Recently, thoracoscopic techniques have been used to perform transmyocardial laser revascularization (TMR) in patients who are not suitable candidates for coronary artery bypass graft (CABG) surgery or percutaneous coronary interventions. Whether or not prior CABG contraindicates a port access-only approach to TMR is unclear. This study compares patients with and without prior CABG who have undergone thoracoscopic TMR.

METHODS

: Between May 2003 and October 2005, 23 consecutive patients (6 without prior CABG, group A; and 17 with prior CABG, group B) underwent thoracoscopic TMR, using a holmium:yttrium-aluminum-garnet (Ho:YAG) laser system. Either 3 or 4 port incisions (each ≤2 cm in length) were used, depending on the patient's anatomy. Procedural success was defined as the ability to create all intended channels without conversion to thoracotomy.

RESULTS

: Patient demographics were not significantly different between group A and group B (mean age, 65.8 ± 4.3 years versus 67.4 ± 2.4 years, Canadian Cardiovascular Society angina class 3.7 ± 0.2 versus 3.9 ± 0.1, and Parsonnet score 12.0 ± 3.2 versus 20.5 ± 2.4). Fourteen (82.4%) group B patients had a prior left internal mammary artery to left anterior descending artery graft, of which 12 (85.7%) were patent. One patient in group A had an airway injury at intubation that led to an extended hospital stay of 30 days. One patient in group A (16.7%) and one patient in group B (5.9%) required a blood transfusion (P = NS). Adhesion lysis time in group B ranged from 0 to 68 minutes (mean, 27 ± 5.6 minutes). Neither group had a conversion to thoracotomy or any deaths through a mean combined follow-up of 12 months.

CONCLUSIONS

: A port access approach is safe and reproducible for patients who are candidates for sole therapy TMR. Prior CABG, including patent grafts, is not a contraindication to thoracoscopic TMR.

Mid-Term Results After Thoracoscopic Transmyocardial Laser Revascularization

BACKGROUND

Transmyocardial revascularization is a surgical therapy for the relief of severe angina in patients who are not suitable candidates for coronary artery bypass graft surgery or percutaneous coronary interventions. Historically, surgical techniques employed a left thoracotomy with or without thoracoscopic assist for visualization. This study evaluated the feasibility and midterm outcomes after transmyocardial laser revascularization performed using a completely thoracoscopic, closed chest approach.

METHODS

Patients (9 men [90%] and 1 woman [10%]) at a mean age of 66 +/- 10 years who were ineligible for coronary artery bypass graft surgery or percutaneous coronary intervention underwent sole therapy transmyocardial laser revascularization using a completely thoracoscopic surgical approach using a holmium:yttrium-aluminum-garnet laser system. Preoperatively, patients had a mean ejection fraction of 0.51 +/- 0.09 and a mean angina class of 3.7 +/- 0.5.

RESULTS

A mean of 30 +/- 2.4 channels were created during mean laser and operative procedure times of 14 +/- 2.9 and 133 +/- 32 minutes, respectively. Patients were extubated at a mean of 7.6 +/- 12 hours and were discharged from the hospital at a mean of 5.4 +/- 3.4 days. There were no hospital deaths or major complications. At a mean of 8.4 +/- 5.5 months postoperatively, all patients survived and significant clinical improvement with a mean angina class of 1.3 +/- 0.5 (p < 0.001).

CONCLUSIONS

A completely thoracoscopic surgical approach is feasible for sole therapy transmyocardial revascularization that affords improved visualization over a limited thoracotomy approach. Limited complications and significant clinical improvement after the procedure were observed. With minimal port manipulation, there is an opportunity for decreased postoperative pain; however, larger studies are warranted to verify this hypothesis.

Totally endoscopic robot-assisted transmyocardial revascularization

OBJECTIVE

Laser transmyocardial revascularization is an emerging therapy for intractable angina stemming from diffuse, small-vessel coronary disease not amenable to percutaneous coronary intervention or coronary bypass grafting. Presently, this therapy is delivered through a median sternotomy or left thoracotomy. In this pilot study, we sought to combine the advantages of a dexterous robotic surgical platform with a flexible fiberoptic laser to develop a minimally invasive approach toward transmyocardial revascularization.

METHODS

A flexible fiberoptic holmium:yttrium-aluminum-garnet laser probe (CardioGenesis Corporation, Foothill Ranch, Calif), deployed with the da Vinci surgical robotic system (Intuitive Surgical, Sunnyvale, Calif), was used to create transmyocardial channels through all left ventricular wall regions in 5 canine subjects. The channels were localized, quantified, and histologically analyzed to assess distribution, dimensions, and transmurality.

RESULTS

Transmyocardial channels were successfully created in all 6 defined left ventricular wall segments by using this minimally invasive approach without port repositioning, instrument exchange, or probe modifications. Gross pathologic and histologic analyses confirmed the uniform distribution of 1.0-mm transmural channels in all left ventricular regions. No direct pressure, topical hemostatic agents, or suture repairs were required for hemostasis. No significant hemodynamic instability or sustained arrhythmias were encountered at any time during the procedures.

CONCLUSIONS

We report the first use of a prototype flexible fiberoptic laser probe deployed by the da Vinci surgical robotic system to successfully perform totally endoscopic off-pump transmyocardial revascularization in a canine model, demonstrating the feasibility, precision, and safety of this approach. Refinement of this minimally invasive technique may reduce the morbidity of open-chest transmyocardial revascularization and facilitate its use as sole therapy or as an adjunct to percutaneous coronary interventions.

Robotic-Assisted Off-Pump Sole Transmyocardial Revascularization: Case Report

Thoracoscopic transmyocardial revascularization (TMR) has been recently demonstrated. We report 2 patients who underwent robotic-assisted thoracoscopic off-pump sole TMR. A 2-inch minimally invasive left anterolateral thoracotomy was made. Pericardial dissection and TMR were performed in an open manner facilitated by improved visualization using voice-activated robotic-assisted thoracoscopy (AESOP, Computer Motion, Santa Barbara, CA, USA). Patient 1 was a 73-year-old man with class IV angina who underwent coronary artery bypass grafting (CABG) x4 20 years earlier. Cardiac catheterization revealed occluded grafts, no native vessels that were amenable to percutaneous coronary intervention (PCI) or CABG, and an ejection fraction (EF) of 55%. Forty-five Holmium-Yag (CardioGenesis, Foothill Ranch, CA, USA) laser channels were created in the left ventricular wall. Total operating room (OR) time was 93 minutes. He was extubated in the OR and was discharged from the intensive care unit (ICU) in 18 hours and from the hospital on the second postoperative day angina free. Patient 2 was a 48-year-old woman with class IV angina who had undergone CABG x6 3 years earlier but who had persistent chest pain following the revascularization. After 12 cardiac readmissions in 1 year, including multiple PCIs, a recent catheterization showed patent grafts except for the circumflex branches and an EF of 45%. Forty-six channels were created in the left ventricle in a similar fashion. OR time was 62 minutes, ICU time was 20 hours, and postoperative length of stay was 2 days. The patient also was angina free at discharge. This report suggests that robotic-assisted thoracoscopy provides enhanced visualization and efficient delivery during off-pump sole TMR, and this technique may be associated with reduced operative times and improved recovery time.

Ventricular arrhythmias following thermal damage of epicardial tissue: possible causes and clinical implications

Epicardial heating may be used for ventricular tachycardia (VT) ablation and transmyocardial revascularization. However, the potential risks of thermal epicardial injury, including arrhythmia, have not been fully explored. This study relates the pathologic and arrhythmic sequellae of epicardial heating when applied with a diode laser at varying doses. Acute pathology and dosimetry were determined in a group of normal dogs using 2-3 W over 30-90 seconds. Another group received a similar dose range before undergoing 24-hour monitoring, and electrophysiological testing was done at 4 weeks. In this group, four dogs each received 12 lesions (90-180 J) according to a randomized block design. Another dog received nine lower dose lesions (30-120 J). Acute lesions measured 2.5-8.0-mm wide by 4-8.5-mm deep. Charring and vaporization were common when 3 W were applied over 45 seconds. Within 24 hours, VT with features of abnormal automaticity occurred in all dogs receiving this dose. The dog in whom lower doses induced coagulation only had no VT. Four weeks later, electrophysiological study induced no VT. At this time fibrosis and granulation tissue were organizing the contraction band necrosis seen acutely, and some lesion borders were becoming calcified. No major vessels had been damaged. Abnormal automaticity and VT may occur if thermal damage of the epicardium exceeds coagulation. This could be related to tissue injury caused by sudden water vaporization, and may have clinical relevance given the growing indications for myocardial heating.

Early postoperative changes in regional systolic and diastolic left ventricular function after transmyocardial laser revascularization: a comparison of holmium:YAG and CO2 lasers

OBJECTIVES

The purpose of this study was to determine the short-term effects of transmyocardial laser revascularization (TMR) on regional left ventricular systolic and diastolic function, myocardial blood flow (MBF) and myocardial water content (MWC).

BACKGROUND

Clinical studies of TMR have noted a significant incidence of cardiac complications in the early postoperative period. However, the early post-treatment effects of laser therapy on the myocardium and their potential contribution to postoperative cardiac morbidity are unknown.

METHODS

Swine underwent holmium:yttrium-aluminum-garnet (holmium:YAG) (n = 12) or carbon dioxide (CO2) (n = 12) laser TMR. Regional systolic function for the lased and nonlased regions was quantitated using preload recruitable work area (PRWA) and regional diastolic function with the ventricular stiffness constant alpha.

RESULTS

Preload recruitable work area was significantly decreased in the lased regions both 1 (59.8+/-13.0% of baseline, p = 0.02) and 6 h (64.2+/-9.4% of baseline, p = 0.02) after holmium:YAG TMR. This decreased PRWA was associated with a significant reduction in MBF to the lased regions (13.2% reduction at 1 h, p = 0.02; 18.4% decrease at 6 h post-TMR, p = 0.01). These changes were not seen after CO2 laser TMR. A significant increase in MWC (1.4+/-0.3% increase with holmium:YAG, p = 0.004; 1+/-0.2% increase with CO2, p = 0.002) and alpha (217.4+/-44.2% of baseline 6 h post-holmium:YAG TMR, p = 0.05; 206+/-36.7% of baseline 6 h post-CO2 TMR, p = 0.03) was seen after TMR with both lasers.

CONCLUSIONS

In the early postoperative setting, impaired regional systolic function in association with regional ischemia is seen after TMR with a holmium:YAG laser. Both holmium:YAG and CO2 lasers are associated with increased MWC and impaired diastolic relaxation in the lased regions. These changes may explain the significant incidence of early postoperative cardiac morbidity. The impact of these findings on anginal relief and long-term outcome are not known.

Myocardial laser revascularization: the controversy and the data

The clinical and experimental data relevant to the theoretical mechanisms and clinical results of laser myocardial revascularization are reviewed. Both transmyocardial and percutaneous approaches are considered. Both types result in a reduction in anginal symptoms in patients refractory to conventional therapy and are likely to act through common pathways. The proximate mechanisms for the transmyocardial revascularization effect most likely relate to myocardial inflammation, secondary stimulation of growth factors, and denervation of the myocardium.

Transmyocardial revascularization: the fate of myocardial channels

Attempted cardiac revascularization through laser-made channels has gained considerable recent notoriety. Although the treatment reduces angina, its ability to enhance perfusion is unclear, and the mechanism of action unknown. The fate of the channels appears an obvious place to look for insight. Therefore, this review focuses on temporal and spatial changes in channel morphology. An appreciation of the natural history of the channels not only has potential to elucidate mechanisms, but also to provide the basis for optimization of channel-making.

Transmyocardial and percutaneous myocardial revascularization: current and future role in the treatment of coronary artery disease

Transmyocardial revascularization (TMR) is a new treatment modality under evaluation in patients with severely symptomatic, diffuse coronary artery disease, in whom the potential for medical or interventional management has been exhausted. Preliminary clinical trials show improved ischemic symptoms within the first 3 months in about 70% of TMR-treated patients. The original proposed mechanism of surgical or catheter-based TMR (percutaneous myocardial revascularization [PMR]) was that channels mediate direct blood flow between the left ventricular cavity and ischemic myocardium. However, several alternative explanations for the clinical success of TMR have recently been suggested, including improved perfusion by angiogenesis, an anesthetic effect by nerve destruction, and a potential placebo effect. This article reviews the clinical role of TMR/PMR, its possible pathophysiologic mechanisms, and its controversies. It provides an overview of the actual scientific and clinical status of TMR and details future directions.

Thoracoscopic procedures for intrathoracic and pulmonary diseases

Since Jacobaeus performed the first thoracoscopy to explore pleural space and mechanically broke pleural adhesions to facilitate the collapse therapy for pulmonary tuberculosis in 1910, numerous thoracic surgeons have been attempting this technique as a means of accomplishing many intrathoracic procedures previously done through open thoracotomy. As the refinement of video technology has advanced, thoracoscopic surgery has played a very important role in thoracic surgery especially since the early 1990s. Because the advantages of video-assisted thoracoscopic surgery for patients include low post-thoracotomy-related morbidity, cosmetic considerations, low pain, earlier post-operative mobilization, and a shorter operation time in some indications, surgeons have been demonstrating its increasing utility in the diagnosis and treatment of the pleura, lung, mediastinum, great vessels, pericardium, and oesophagus. The most common application of the thoracoscopic approach still remains in the management of pleuropulmonary disease. The indications for the thoracoscopic technique are very broad, but its role in the management of primary lung and oesophageal cancer has yet to be confirmed. Thus, the surgeon who uses the technique in these cancerous diseases should be prudent. In conclusion, these thoracoscopic procedures will play more important roles in the practice of thoracic surgery in the future.

Combination TMR and gene therapy

Transmyocardial laser revascularization is a promising surgical technique that relieves angina and improves subendocardial perfusion in patients with chronic ischemic heart disease refractory to medical management and not amenable to conventional revascularization techniques. We detail our laboratory experience at the Brigham and Women's Hospital with transmyocardial laser revascularization and discuss the potential clinical applications of this work.

The feasibility of using focused ultrasound for transmyocardial revascularization

Transmyocardial laser revascularization (TMR) is used for improving the blood supply to damaged myocardium due to advanced heart disease. We hypothesize that focused ultrasound can be used to generate channels through the cardiac muscle by vaporizing the tissue at the focal spot. The purpose of this study was to evaluate the effects of varying the ultrasound exposure parameters (frequency, amplitude, pulse period, duty cycle, focal depth and exposure time) on the vaporized tissue size and to determine the feasibility of using ultrasound for creating cavities and/or channels in the left ventricular wall for transmyocardial revascularization. Based on in vitro experiments using bovine myocardium, the experiments indicate that a 1 mm diameter channel could be created by using, for example, a focused transducer with a diameter of 10 cm and a radius of curvature of 8 cm operating at a frequency of 2.52 MHz. The required spatial peak intensity during the 0.5-s sonications was found to be 2300 W/cm2 with a pulse repetition period of 40 ms and a 50% duty cycle. These parameters have been used to create cavities during in vivo tests using canine myocardium. The results demonstrated that ultrasound could be used to create small channels through myocardium. The most important potential for ultrasound is its ability to generate these channels completely noninvasively.

Thoracoscopic transmyocardial laser revascularization

Transmyocardial laser revascularization has been used to treat patients with end-stage coronary artery disease and severe disabling angina. Typically, the operative approach is through a left anterior thoracotomy. I report a case of transmyocardial laser revascularization performed thoracoscopically.