Extent of myocardial tissue damage during transmyocardial laser revascularization with the CO2 Heart Laser

Does laser type impact myocardial function following transmyocardial laser revascularization?

BACKGROUND

Transmyocardial laser revascularization (TMR) is currently clinically performed with either a CO(2) or Ho:YAG laser for the treatment of severe angina. While both lasers provide symptomatic relief, there are significant differences in the laser-tissue interactions specific to each device that may impact their ability to enhance the perfusion of myocardium and thereby improve contractile function of the ischemic heart.

METHODS

A porcine model of chronic myocardial ischemia was employed. After collecting baseline functional data with cine magnetic resonance imaging (MRI) and dobutamine stress echo (DSE), 14 animals underwent TMR with either a CO(2) or Ho:YAG laser. Transmural channels were created with each laser in a distribution of 1/cm(2) in the ischemic zone. Six weeks post-treatment repeat MRI as well as DSE were obtained after which the animals were sacrificed. Histology was preformed to characterize the laser-tissue interaction.

RESULTS

CO(2) TMR led to improvement in wall thickening in the ischemic area as seen with cine MRI (40.3% vs. baseline, P < 0.05) and DSE (20.2% increase vs. baseline, P < 0.05). Ho:YAG treated animals had no improvement in wall thickening by MRI (-11.6% vs. baseline, P = .67) and DSE (-16.7% vs. baseline, P = 0.08). Correlative semi-quantitative histology revealed a significantly higher fibrosis index in Ho:YAG treated myocardium versus CO(2) (1.81 vs. 0.083, P < 0.05).

CONCLUSIONS

In a side-by-side comparison CO(2) TMR resulted in improved function of ischemic myocardium as assessed by MRI and echocardiography. Ho:YAG TMR led to no improvement in regional function likely due to concomitant increase in fibrosis in the lasered area.

Release of cardiac biochemical markers after percutaneous myocardial laser or sham procedures

BACKGROUND

Percutaneous myocardial laser (PML) reduces symptoms in patients with intractable angina. PML leads to a certain loss of viable myocardium, we therefore assessed if troponin or cardiac markers release may explain the clinical effect, and furthermore assessed the markers release during percutaneous sham procedures.

METHODS

Eighty-two patients with chronic refractory angina were randomized to either percutaneous myocardial laser or a true sham procedure. Cardiac markers were assessed before the procedure, and (1/2), 2, 4, 6, and 10-12 h postprocedure.

RESULTS

Troponin I increased to median peak levels (range) of 4 (0.6-43) microg/L in the laser group vs. 1.5 (0.1-5.9) microg/L, p=0.001, and creatine kinase MB to 14 (6-357) microg/L vs. 11 (3-40) microg/L, p<0.05, within and between-group comparison, the rise of CK-MB occurred significantly earlier in the sham group, 3.8 vs. 2.5 h. A time-dependent between-group difference was only detected for troponin. 88% of sham and 100% of laser patients had marker levels above reference limits. There was no correlation between the number of laser/sham created channels, biomarker levels postprocedure, and changes in left ventricular ejection fraction or angina improvement during 12 months of follow-up.

CONCLUSIONS

The release of cardiac markers is not related to relief of angina after myocardial laser. The use of intracardiac catheters induces a considerable marker release, which is not caused by acute ischemia.

The Society of Thoracic Surgeons practice guideline series: transmyocardial laser revascularization

BACKGROUND

Patients with chronic severe angina refractory to medical therapy who cannot be completely revascularized with either percutaneous catheter intervention or coronary artery bypass graft surgery present clinical challenges. Transmyocardial laser revascularization, either as sole therapy or as an adjunct to coronary artery bypass graft surgery, may be appropriate for some of these patients. Although transmyocardial revascularization has consistently been demonstrated as an efficacious means of relieving angina, the mechanism of its effects are still debated, and criteria for the selection of patients for this novel therapy have not been adequately defined.

METHODS

We reviewed the available evidence to allow us to make recommendations for the appropriate therapeutic applications of transmyocardial revascularization following the format of the American Heart Association and the American College of Cardiology guidelines for diagnostic and therapeutic procedures. Our recommendations were classified as class I, IIA, IIB, or III. For each recommendation we defined the level of supporting evidence as A, B, or C.

RESULTS

We identified class I indications for transmyocardial revascularization as sole therapy and class IIA indications for transmyocardial revascularization as an adjunct to coronary artery bypass graft surgery with levels of evidence A and B, respectively.

CONCLUSIONS

Transmyocardial laser revascularization may be an acceptable form of therapy for selected patients: as sole therapy for a subset of patients with refractory angina and as an adjunct to coronary artery bypass graft surgery for a subset of patients with angina who cannot be completely revascularized surgically.