Transmyocardial Laser Revascularization — Rethinking Therapy for Complicated Patients

 

Although it provided significant relief of the symptoms of angina in the majority of patients, it fell out of favor due to concerns about inconsistent data on perfusion improvement.

 

Due to the growing rates of obesity, type 2 diabetes and other conditions associated with metabolic disorder that can weaken veins, the subset of patients with severe coronary artery disease and angina who are not amenable to balloon dilation or coronary artery bypass grafting is becoming substantial. The growing need for alternative therapies and a more thorough investigation of TMR brings this therapy back into play. Careful culling of the data surrounding TMR shows that modality is very important, and correct technique improves results and decreases risks. Thus I have found that TMR performed with a carbon dioxide (CO2) laser to be very effective in this subset of difficult-to-treat patients.

 

 

Comparisons of the two laser modalities show that Ho:YAG lasers create a zone of structural and thermal damage that is 3.5 times greater than the carbon dioxide laser, resulting in 5.7 times more volumetric tissue damage.[5] This additional tissue damage significantly impairs the left ventricular function as well as myocardial blood flow in the immediate postoperative period.[5] Neither of these impairments are observed with the carbon dioxide laser.[5] See Charts 1 and 2

 

The long-term efficacy of TMR with the carbon dioxide laser is also confirmed. In a study of 78 patients with severe angina not amenable to conventional revascularization, the average angina class was significantly improved from 3.7 + 0.4 at baseline to 1.5 + 1 at one year post-TMR with the carbon dioxide laser, which persisted for five years or more.[2] 

 

With growing positive evidence for TMR with a carbon dioxide laser, the discussion has evolved to the mechanics of how it works. While this is an ongoing process, evidence supports the idea that a carbon dioxide laser promotes the enhancement and release of vascular endothelial growth factors in the cells, leading to angiogenesis.[3] In addition, the carbon dioxide laser increases vascularity, and high-resolution magnetic resonance (MRI) and ultrasound imaging show that this improvement persists over time.[4] This improvement in vascularity post-carbon dioxide TMR has been demonstrated to provide improved perfusion and cardiac function clinically[4], whereas the Ho:YAG laser has not been shown to improve perfusion or cardiac function.[4] This disparity led to studies which demonstrated denervation of cardiac tissue may play a role in angina relief post-Ho:YAG TMR.[3, 4]

 

 

Patients eligible for combination therapy have angina pectoris +1-5, at least one section amenable to coronary bypass surgery and demonstrable ischemia on a stress test.[6]  

 

At my hospital, we have performed TMR with the carbon dioxide laser on more than 50 patients in the past two years and have compiled all data from these patients into a common databank. As the referring cardiologist considers TMR as sole therapy as a last-resort modality, it was employed for only a small percentage of patients. The majority of these patients received TMR in combination with coronary artery bypass surgery. The outcomes have been very good, and this coincides with other international studies that did focus solely on TMR with the carbon dioxide laser. Continuing to collect this data and sharing it with colleagues is the only means of educating cardiologists and other professionals on the merits of TMR as sole therapy. 

 

 

Difficult cardiac patients with multiple complications are on the rise, and modalities are needed to treat them. Recurring symptoms, repeat hospitalizations and rising pharmacologic prices are combining to raise the cost of treating these patients. TMR is a good alternative that provides immediate and sustained relief for these patients, and may have even greater potential when combined with regenerative therapies.