Transmyocardial revascularization (TMR) is a surgical treatment option for patients suffering from angina (the symptom associated with inadequate blood flow to the heart muscle because of blocked arteries) when neither percutaneous coronary intervention(PCI) or coronary bypass surgery (CABG) can satisfactorily be performed.
The theory of how TMR works to provide blood flow to the heart muscle was based on the reptilian circulation where blood to feed the heart muscle goes straight from the heart chamber to the muscle via a communicating chain of lakes. TMR is performed by using a laser ( CO2 or Holmium:Yag) to perforate the heart muscle from the outside into the major heart chamber that carries oxygenated blood and creating a communication between the heart chamber and the muscle. Multiple perforations are performed 1cm apart. While patency of these channels does not persist, patients symptoms and exercise tolerance is much improved. The improvement is believed to be secondary to the TMR laser inducing angiogenesis( growth of new blood vessels).
There are two circumstances where TMR are used:
Sole therapy for patients not candidates for PCI or CABG but are suffering from angina:
This procedure is usually performed through a small incision in the left chest and is performed on the beating heart.
There is strong evidence for TMR as sole therapy- Class 1(level of evidence A)
The Society of Thoracic Surgeons has recommended TMR as sole therapy for patients with:
a. Ejection fraction>30%
b. Canadian Cardiovascular Class III or IV angina refractory to medical therapy
c. Reversible ischemia of the left ventricular wall and coronary artery disease corresponding
to the region of myocardial ischemia
d. In all regions of the myocardium(heart muscle) not amenable to CABG or PCI either due to diffuse disease, lack of suitable targets for revascularization or lack of suitable conduits for revascularization.
TMR as an adjunct to CABG -Class IIA (level of evidence B) for patients in whom CABG is the standard of care who have viable ischemic myocardium that cannot be revascularized due to diffuse disease not suitable for grafting or lack of suitable conduits to be used for complete revascularization.
Patients who undergo TMR have long term angina relief: At 5yrs 68% of patients who underwent TMR had a > 2- angina class improvement in symptoms with CCS angina Class improved to 1.6 from a baseline of 3.7.
Patients had improved exercise tolerance, angina stability, angina frequency, treatment satisfaction and disease perception, as well as a dramatic reduction in repeat hospitalization following TMR as compared to the medical management group.
Studies have found that patients who have undergone CABG combined with TMR may confer excellent perioperative and survival rates, including decreased mortality, inotropic support and ICU stay, while prolonging 1 year survival compared to patients undergoing CABG alone. Patients who undergo both procedures appear to be less symptomatic at follow-up.