**5. Transmyocardial laser revascularization**

Transmyocardial laser revascularization (TMR) is one of the first described surgical procedures intended to treat severe diffuse CAD not amenable to CABG or PTCA in patients who have had previous percutaneous coronary interventions and/or CABG procedures. This severe coronary artery disease can lead to incomplete revascularization following CABG and is powerful independent perioperative adverse events. Indications for TMR include NYHA class III/IV symptoms refractory to medical treatment with coronary disease that is not amenable to revascularization. [38, 39, 40]TMR is generally contraindicated in patients who are candidates for revascularization or those who are not candidates but have an ejection fraction below 20%.

By inducing angiogenesis with a laser (carbon dioxide, holminumyttrium– aluminumgarnett), TMR has been shown to decrease the severity of angina symptoms compared to medical therapy. [41, 42] As such, the primary indication for TMR is persistent and disabling angina refractory to medical therapy. Owing to its success as sole therapy, TMR is used in conjunction with CABG. The safety and efficacy of TMR in this subset of patients has been well described; operative mortality and morbidity may be significantly less than CABG alone. [43]

Since Food and Drug Administration (FDA) approval in 1998, over 20,000 TMR procedures have been performed in the United States. [44]

### **5.1. Operation**

**•** Deep Hypothermia Deep hypothermia (18-20°C) should be attained on CPB. Following

**•** Distal Anastomosis During the cooling phase of CPB, the distal anastomoses are performed in the following order: LAD, RCA/posterior descending artery, and marginal branches. Of note, when the heart is lifted during construction of distal anastomoses, bypass flow should be reduced to allow for decompression, thereby optimizing exposure and minimizing damage to the heart. Frequently, at least 1 proximal anastomosis is performed under a brief

**•** Endarterectomy When calcification is localized, endarterectomy can be performed under circulatory arrest to created portion of aorta which is decalcified to place a crossclamp.

**•** Ascending Aorta Replacement In extreme case, the ascending aorta should be replaced under deep hypothermic circulatory arrest. Proximal anastomosis is performed directly to

**No touch Technique** No touch technique described by Suma et al can be used [34]. In this instance, CPB is established between right atrium and aortic arch or femoral artery. Left ventricular vent is placed. Aortic cross clamping and cardioplegia delivery was avoided. Ventricular fibrillation was induced while target was occluded using elastic stitches. Pedicled artery graft is used for anastomosis. In case the saphenous vein is used, it is anastomosed to the artery graft or to the ascending aorta where calcification is spared.

**Off-pump bypass** Off-pump bypass can be used in case arch and femoral artery is calcified as well. In this case, all arterial revascularization is performed using in situ internal thoracic and

Aortic endarterectomy and aortic graft replacement provides opportunity to revascular‐ ize the coronary artery and eliminate danger of systemic emboli. It is reported to be performed safely, [35, 36] but these procedures do add complexity and risk due to the

No touch technique and off pump technique provides theoretical benefit to the proce‐ dure, but has not been able to provide definite superiority. Off pump technique offers inferior possibility of complete revascularization especially to the lateral branches of circumflex artery. On the other hand, no touch technique still requires insertion of the arterial cannula which can predispose to systemic and cerebral emboli. Gaudino et al compared these two techniques in 211 unclampable aorta cases and reported no touch technique had greater incidence of neurological complications, renal insufficiency, and stay in the intensive care unit and hospital. However, at midterm follow-up, more patients of the off pump group had ischemia recurrence. [37] Stroke rate was 2.3% and in-

radial artery. Y grafts are created to internal thoracic artery if radial artery is used.

fibrillation of the heart, a left ventricular vent is placed.

period of circulatory arrest.

the graft.

180 Artery Bypass

**4.3. Outcome**

circulatory arrest.

hospital mortality was 2.8% in this study.

**Left thoracotomy and Heart Exposure** A left anterolateral thoracotomy is the incision of choice in patients undergoing TMR as the sole surgical procedure. The heart is exposed, allowing for the access to the anterior, apical, and posterolateral planes of the left ventricle. Careful attention must be paid to not injure the previous bypass grafts. LAD is identified and used as a landmark for the location of the septum. TMR is provided through a hand piece that delivers energy through hollow tubes to the epicardium.

**Choose type of laser** Type of Laser Only CO2 and Holmium-chromium: YAG lasers (Ho:YAG) are clinically approved for TMR. The result of any laser-tissue interaction is dependent on both laser and tissue variables. CO2 laser has wavelength of 10,600nm, whereas Ho:YAG laser has wavelength of 2,120nm. The laser is synchronized to occur on the R-wave of the electrocar‐ diogram to avoid induction of arrhythmias.

**Application of laser** Pulse energy of 20-30 J over 4 pulses per second creates 1-mm channels in the myocardium that can be visualized with a transesophageal echocardiogram. Using the CO2 laser, channels are first created at the base of the heart and are separated from each other by 1 cm to the apex of the heart starting inferiorly and working superiorly to the anterior surface of the heart. As there is some bleeding from the channels, gravity will keep the field clean by starting inferiorly.

It should be noted that TMR does not provide any added benefit to areas of myocardium that are scarred and have no viability. TMR on the transmural scar will not only be non-beneficial, it will cause bleeding which may be problematic. Detection of transmural penetration is primarily by tactile and auditory feedback.

technique or off-pump CABG. TMR may be indicated for patients who have exhausted non surgical options. The outcomes in this complex coronary artery surgery are improving and the results have validated the safety, effectiveness and health outcomes. However, it is crucial to make good patient selection as well as intraoperative decision. Cardiac surgeons must familiarize themselves to these procedures as coronary artery disease patients will be more

Complex Coronary Artery Disease http://dx.doi.org/10.5772/55251 183

[1] ElBardissi AW, Aranki SF, Sheng S, O'Brien SM, Greenberg CC, Gammie JS. Trends in isolated coronary artery bypass grafting: an analysis of the Society of Thoracic Sur‐ geons adult cardiac surgery database. J ThoracCardiovascSurg Feb;143(2):273-81.

[2] Spiliotopoulos K, Maganti M, Brister S, RaoVivek. Changing Pattern of Reoperative Coronary Artery Bypass Grafting: A 20-Year Study. Ann ThoracSurg 2011;92:40-7.

[4] Lytle BW, Loop FD, Taylor PC, et al: Vein graft disease: The clinical impact of stenos‐ es in saphenous vein bypass grafts to coronary arteries. J ThoracCardiovascSurg

[5] Lytle BW, Loop FD, Taylor PC, et al: The effect of coronary reoperation on the sur‐ vival of patients with stenoses in saphenous vein bypass grafts to coronary arteries. J

[6] Lytle BW, McElroy D, McCarthy P, et al: Influence of arterial coronary bypass grafts on the mortality in coronary reoperations. J ThoracCardiovascSurg 107:675-682, 1994

[7] Jones EL, Lattouf OM, Weintraub WS: Catastrophic consequences of internal mam‐

[8] Von Kiedrowski H, Wiemer M, Franzke K, et al: Non-invasive coronary angiogra‐ phy: The clinical value of multi-slice computed tomography in the assessment of pa‐ tients with prior coronary bypass surgery. Evaluating grafts and native vessels. Int J

mary artery hypoperfusion. J ThoracCardiovascSurg 98:902-907, 1989

ThoracCardiovascSurg 105:605-612, 1993, discussion, 612-614

[3] Cohn L: Cardiac Surgery in the adult, vol. 4. New York, NY, McGraw-Hill, 2011

complex in the future.

**Author details**

**References**

Tsuyoshi Kaneko and Sary Aranki\*

103:831-840, 1992

Cardiovasc Imaging 25:161-170, 2009

Brigham and Women's Hospital, Harvard Medical School, USA

#### **5.2. Outcome**

Mortality following TMR ranges from 1% to 5%; however, this low rate of mortality is primarily generalized to patients who are electively taken to the operating room and are hemodynami‐ cally stable. When these patients are taken to the operating room emergently, mortality is reported to be 10-20%. One-year survival following TMR ranges from 79% to 96% and is not significantly different from patients who undergo medical therapy. The primary advantage of TMR over medical therapy and the principal indication for intervention is the reduction in symptomatology; studies have found that 25%-76% of patients will achieve a decrease of 2 or more angina classes following intervention, which is not the case of patients undergoing medical intervention. Review of the randomized controlled study suggests improvement in perfusion for CO2 TMR treated patients. [45 46] Long term results suggest improved angina symptoms and decreased hospitalization in five years. [47]

However, the benefit of TMR is controversial. Cochrane review published it data after reviewing seven studies (1137 participants of which 559 randomized to TMR). Overall, 43.8 % of patients in the treatment group decreased two angina classes as compared with 14.8 % in the control group. Mortality at both 30 days (4.0 % in the TMR group and 3.5 % in the control group) and 1 year (12.2 % in the TMR group and 11.9 % in the control group) was similar in both groups. The 30-days mortality as treated was 6.8% in TMLR group and 0.8% in the control group, showing a statistically significant difference. Their conclusion was there is insufficient evidence to conclude that the clinical benefits of TMLR outweigh the potential risks and the procedure is associated with a significant early mortality. [48]

TMR is used in conjunction with CABG as well. One randomized controlled study have found that TMR combined with CABG may confer excellent perioperative and survival rates, including decreased opeartive mortality, inotropic support, and intensive care unit stay, while prolonging 1-year survival compared to those patients undergoing CABG alone. [49] Further‐ more, patients who undergo both procedures appear to be less symptomatic at follow-up.

In conclusion application of TMR in selected group for the treatment with severe angina due to diffuse disease can be used achieves a more complete revascularization.
