Clinical experience with the holmium:YAG laser for transmyocardial laser revascularization and myocardial denervation as a mechanism

Laser technology in proctological diseases: is it really the wave of the future?

Different types of lasers have been applied for various proctological conditions. We discuss about published articles regarding the application of lasers, with concern about evidence-based use of these techniques and technologies. We performed a literature search about laser treatments for proctological conditions. 55 studies were included for the final revision. Meta-analysis of data was not performed because of heterogeneity of study designs and outcome measures. A scoping review was performed. Laser treatments for hemorrhoids require a shorter operative time and show less postoperative pain and bleeding compared to conventional hemorrhoidectomy, but are more expensive. Studies are heterogeneous in design, endpoints, postoperative assessment, length of follow-up and outcome measures. Only 3 RCTs are available and only three studies evaluate long-term outcomes. FiLaC (fistula laser closure) was initially described in 2011 for the treatment of anal fistula. In the published studies the reported healing rates vary between 20 and 82%, and the ideal indication is yet to be defined. Studies with long-term follow-up are lacking. SiLaT (sinus laser treatment) applied the technology used for FiLaC to the treatment of pilonidal sinus disease. This technique had less perioperative pain and shorter hospital stay, but a lower primary healing rate when compared to traditional techniques. Available data is very limited, and no randomized trials are published to date. Laser assisted techniques are a viable, minimally invasive, but expensive option for the treatment of several proctological conditions. Further researches are needed to assess if patients could benefit of their use, and for what indication.

Treatment of refractory angina pectoris

Refractory angina pectoris is defined as Canadian Cardiovascular Society class III or IV angina, where there is marked limitation of ordinary physical activity or inability to perform ordinary physical activity without discomfort, with an objective evidence of myocardial ischemia and persistence of symptoms despite optimal medical therapy, life style modification treatments, and revascularization therapies. The patients with refractory angina pectoris may have diffuse coronary artery disease, multiple distal coronary stenoses, and or small coronary arteries. In addition, a substantial portion of these patients cannot achieve complete revascularization and continue to experience residual anginal symptoms that may impair quality of their life and increase morbidity. This represents an end-stage coronary artery disease characterized by a severe myocardial insufficiency usually with impaired left ventricular function. As the life expectancy is increasing, patients with angina pectoris refractory to conventional antianginal therapeutics are a challenging problem. We review the nonconventional therapies to treat the refractory angina pectoris, including pharmacotherapy, therapeutic angiogenesis, transcutaneus electrical nerve and spinal cord stimulation, enhanced external counterpulsation, surgical transmyocardial laser revascularization, percutaneous transmyocardial laser revascularization, percutaneous in situ coronary venous arterializations, and percutaneous in situ coronary artery bypass. These therapies are not supported by a large body of data and have only a complementary role; therefore, the aggressive traditional and proven treatment of angina pectoris should be continued along with these therapies, used on an individual basis.

Transmyocardial coil implants: a novel approach to transmyocardial revascularization

BACKGROUND

Transmyocardial laser revascularization (TMLR) has potential benefit for patients with end-stage coronary artery disease and intractable angina not amenable to conventional revascularization techniques. Neovascularization has been proposed to occur around the laser channels. Our aim was to determine the feasibility of a novel nonlaser myocardial revascularization technique and its effect on angiogenesis in a nonischemic porcine model.

METHODS

In the first phase, six transmyocardial stainless steel coil implants (TMI) were deployed to the lateral wall of the left ventricle in each of 6 pigs. The animals were sacrificed at 8 and 12 weeks, with a single animal dying prematurely at 4 weeks, and the myocardium was assessed for new vessel growth. In the second phase, 8 implants were deployed in each of 12 pigs with regular fluoroscopic follow-up until sacrifice at 2 weeks to assess implant stability.

RESULTS

The deployment procedure was safe and feasible with no complications evident. A significant increase in new vessels at implant sites with 5.43 +/- 3.67, 4.97 +/- 2.44, and 3.57 +/- 2.29 seen per high power field at 12, 8, and 4 weeks, respectively, compared to 1.00 +/- 1.06 (p < 0.0001) in control myocardium. There was no evidence of implant migration in Phase 2.

CONCLUSIONS

TMIs can feasibly be deployed in the nonischemic pig model with a high success rate. The presence of angiogenesis at the implant site and the maintenance of this reaction for 3 months implies that TMI may offer an alternative to TMLR while providing a platform for delivery of angiogenic factors.

Quantitative analysis of myocardial perfusion changes with transmyocardial laser revascularization

Transmyocardial laser revascularization (TLR) is a technique of creating left ventricular transmural channels in patients with refractory angina. We aimed to measure perfusion changes quantitatively using technetium-99m methoxyisobutyl isonitrile. Perfusion scans were performed on 94 TLRs and in 94 control patients at rest and during exercise at assessment, and 3-, 6-, and 12-month follow-up. A serial set of scans allowed direct comparison of each patient over all visits. Bull's-eyes were divided into 5 anatomic regions and a 20-region model. Severity values were calculated for rest, stress, and each cardiac region using a threshold of 1 for analysis. Higher scores indicated greater severity of ischemia and lower perfusion. At 3-month follow-up, the severity was significantly worse during TLR than in control patients both during stress (0.172 +/- 0.003 and 0.161 +/- 0.003, respectively, p = 0.007) and at rest (0.170 +/- 0.003 and 0.158 +/- 0.003, respectively, p = 0.002). At 6 months, severity during stress was 0.176 +/- 0.003 with TLR and 0.162 +/- 0.003 in controls (p = 0.001), with no significant difference at rest. At 12 months, there was no significant difference between TLR and control groups at stress and rest. Regional severity deteriorates during TLR compared with control patients anteriorly (p = 0.001, p = 0.0016, p = 0.005 at 3, 6, and 12 months), apically (p = 0.005, p = 0.0046, p = 0.032, respectively), and laterally (p <0.0001, p = 0.001, p = 0.002, respectively). An apparent improvement is observed in the inferoseptal region at 6- and 12-month follow-up-an area not lasered. Thus, TLR appears to produce deterioration in resting myocardial perfusion in lasered regions, and improvement in nonlasered regions, with no difference in exercise-induced myocardial ischemia compared with that in control patients.

Acute and chronic effects of transmyocardial laser revascularization in the nonischemic pig myocardium by using three laser systems

BACKGROUND AND OBJECTIVE

Transmyocardial laser revascularization (TMLR) improves symptoms in patients with coronary heart disease. It is based on the hypothesis of direct perfusion of ischemic myocardium by means of laser-created channels. Three different lasers were used to study alternative effects on myocardium.

STUDY DESIGN/MATERIALS AND METHODS

The present study was conducted to evaluate comprehensively and compare the short and long-term tissue effects and the basic interaction mechanisms of CO2, Ho:YAG, and Er:YAG laser radiation with myocardium. The dynamics of laser-induced impacts in gel used as tissue phantom was visualized by time-resolved flash photography. Pressure measurements performed during perforation of myocardium in vitro revealed the explosive character of the ablation process. Channels made into the left ventricle of normal pig hearts were examined immediately and 6 weeks after creation.

RESULTS

Regardless of laser source, all channels became occluded within 6 weeks by scar. Minimal acute thermal damage by Er:YAG laser corresponded to smaller scars. Pulsed Ho:YAG caused stronger tissue tearing than continuous wave CO2 irradiation. An increased volume density of intramyocardial vessels was found about the scars 6 weeks after treatment with all lasers.

CONCLUSION

The laser sources permitted to study outcome of pressure effects and thermal damage in vivo. There were only minor differences between the three laser systems used. Rapid channel occlusion suggests that rather than revascularization, subsidiary physiologic tissue effects elicited by the thermal, oxidative, or mechanical action of the laser impact may contribute to the beneficial clinical effects of TMLR.

Transmyocardial laser revascularization

Transmyocardial laser revascularization is an alternative treatment option for patients with refractory angina who are not suitable candidates for more conventional coronary intervention or surgery. The laser creates channels that provide blood flow from the left ventricular chamber to areas of ischemic myocardium. Results have been impressive with patients reporting a reduction in angina of two classes according to the Canadian Heart Association Angina Classification. Care of the patient post transmyocardial laser revascularization procedure is comparable to that of other cardiac surgery patients. Innovations in this relatively new procedure include less invasive approaches and using it as an adjunctive or delivery modality for gene therapy.

Has laser revascularization found its place yet?

Transmyocardial laser revascularization (TMR) is a relatively new therapy for atherosclerotic coronary artery disease. Unlike well established surgical and percutaneous revascularization procedures, TMR is reserved for patients with advanced and severe forms of coronary artery disease that is unsuitable for other forms of revascularization. The results of TMR so far have been controversial with a bias toward steady and incremental adoption as sole therapy or in combination with coronary artery bypass graft surgery. The controversy surrounding TMR is related to the fact that its mechanism of action is not proven beyond a reasonable doubt. It is believed that angiogensis stimulation by the laser beam may be responsible for the relief of angina. However, the marked discrepancy in the symptomatic relief of angina and the increase in myocardial perfusion is not well understood. Other mechanisms proposed include direct perfusion through the laser channels, myocardial damage, denervation of ischemic myocardium and a placebo effect. It is possible that one or more of these mechanism may be responsible at various time intervals for the relief of angina. The challenge of TMR is related to improvement in perioperative outcomes, and long-term survival without worsening of left ventricular function. The achievement of these goals makes TMR an alternative therapy to what was formerly the only therapeutic option for these patients, namely: failed maximum medical therapy.