A new method of myocardial revascularization by laser

Review of Laser Therapy in Cardiovascular Diseases

Introduction: In recent years, there has been a rise in laser therapy for the treatment of cardiovascular diseases. Methods: This paper attempted to represent recent advances in laser therapy in cardiovascular tissue repairs. Three standard techniques have been explicitly described here in cardiovascular tissue repairs by laser. Results: One of the advantages of using laser therapy in cardiovascular diseases is its non-invasiveness. It also reduces the treatment process pain and prevents massive surgical incisions and bleeding throughout the operation. Laser therapy can ensure an alternative method to treat the ischemic region of the heart and creating anastomosis of vessels. Conclusion: With professional technologies and endoscopic surgery method development, the role of using lasers has become much more precise and more transparent in cardiovascular diseases.

Outcomes of middle cardiac vein arterialization via internal mammary/thoracic artery anastomosis

OBJECTIVE

Cardiac vein arterialization is seldom applied for treating right coronary artery disease. This study aimed to improve outcomes of cardiac vein arterialization in a porcine model using intramammary artery anastomosis.

METHODS

A chronic, stenotic coronary artery model was established in 12 of 14 Chinese experimental miniature pigs of either sex, which were randomly divided into equal control (n =6) and experimental (n = 6) groups. In experimental animals, blood flow was reconstructed in the right coronary artery using intramammary artery. Arterialization involved dissection of right internal mammary artery from bifurcation to apex of thorax followed by end-to-side anastomosis of internal mammary artery and middle cardiac vein plus posterior descending branch of right coronary artery. Intraoperative heart rate was maintained at 110 beats/min. Graft flow assessment and echocardiography were performed when blood pressure and heart rate normalized.

RESULTS

The experimental group had significantly higher mean endocardial and epicardial blood flow postoperatively than control group (mean endocardial blood flow: 0.37 vs. 0.14 ml/(g*min), p<0.001; mean epicardial blood flow: 0.29 vs. 0.22, p = 0.014). Transmural blood flow was also higher in experimental group than in control group (0.33 vs. 0.19, p<0.001); ejection fraction increased from 0.46% at baseline to 0.51% (p = 0.0038) at 6 hours postoperatively, and mean blood flow of internal mammary artery was 44.50, perfusion index 0.73 at postoperative 6 months, 43.33 and 0.80 at 3 months.

CONCLUSION

Successful cardiac vein arterialization via intramammary artery in a porcine model suggests that this may be a viable method for reconstructing blood flow in chronic, severe coronary artery disease.

Clinical application of laser treatment for cardiovascular surgery

BACKGROUND

Recently, several kinds of lasers have been widely employed in the field of medicine and surgery. However, laser applications are very rare in the field of cardiovascular surgery throughout the world. So, we have experimentally tried to use lasers in the field of cardiovascular surgery. There were three categories: 1) Transmyocardial laser revascularization (TMLR), 2) Laser vascular anastomosis, and 3) Laser angioplasty in the peripheral arterial diseases. By the way, surgery for ischemic heart disease has been widely performed in Japan. Especially coronary artery bypass grafting (CABG) for these patients has been done as a popular surgical method. Among these patients there are a few cases for whom CABG and percutaneous coronary intervention (PCI) could not be carried out, because of diffuse stenosis and small caliber of coronary arteries. Materials and methods of TMLR: A new method of tranasmyocardial revascularization by CO2 laser (output 100 W, irradiation time 0.2 sec) was experimentally performed to save severely ill patients. In this study, a feasibility of transmyocardial laser revascularization from left ventricular cavity through artificially created channels by laser was precisely evaluated.

RESULTS

In trials on dogs laser holes 0.2mm in diameter have been shown microscopically to be patent even 3 years after their creation, thus this procedure could be used as a new method of transmyocardial laser revascularization. Clinical application of TMLR: Subsequently, transmyocardial laser revascularization was employed in a 55-year-old male patient with severe angina pectoris who had undergone pericardiectomy 7 years before. He was completely recovered from severe chest pain. Conclusions of TMLR: This patient was the first successful case in the world with TMLR alone. This method might be done for the patients who percutaneous coronary intervention and coronary artery bypass grafting could be carried out. Laser vascular anastomosis: At present time, in vascular surgery there are some problems to keep long-term patency after anastomosis of the conventional suture method, especially for small-caliber vessels. Materials and methods of Laser vascular anastomosis: From these standpoints, a low energy CO2 laser was employed experimentally in vascular anastomosis for small-caliber vessels. Resullts of Laser vascular anastomosis: From preliminary experiments it could be concluded that the optimal laser output was 20-40 mW and irradiation time was 6-12 sec/mm for vascular anastomosis of small-caliber vessels in the extremities. And then, histologic findings and intensity of the laser anastomotic sites were investigated thereafter. Subseqently, good enough intensity and good healing of laser anastomotic sites as well as the conventional suture method could be observed. There were no statistic differences between laser and suture methods. A feasibility of laser anastomosis could be considered and clinical application could be recognized. Clinical applications of Laser vascular anastomosis: On February 21, 1985, arterio-venous laser anastomosis for the patient with renal failure was smoothly done and she could accept hemodialysis. Conclusions of Laser vascular anastomosis: This patient was the first clinical successful case in the world. Thereafter, Laser vascular anastomosis were in 111 patients with intermittent claudication, refractory crural ulcer, and coronary disorders. Thereafter, they are going well. Laser angioplasty: Laser angioplasty for peripheral arterial diseases. There are many methods to treat peripheral arterial diseases such as balloon method, atherectomy, laser technique and stenting graft in the field of endovascular treatment. Recent years, minimal invasive treatment should be employed even in the surgical treatment. However, there are different images between these methods. Materials and methods of Laser angioplasty: We have chosen to use laser for endovascular treatment for peripheral arterial diseases. We have tried to check between laser energy and vessel wall. Results of Laser angioplasty: Subsequently, it could be concluded that optimal conditions for laser angioplasty were 6 W in output and irradiation time was 5 sec. And with another method of feedback control system, temperature of metal tip probe was 200°C and irradiation time was 5 sec for each shot. And histological study and feasibility of angioscopic guidance could be done and clinical application was started. Until now, 115 patients were successfully treated with their life longevity. Conclusions of Laser angioplasty: Thus, laser applications were useful methods to treat a lot of patients with some ischemic problems.

Clinical results of sole therapy TMR treatment

The safety and efficacy of transmyocardial laser revascularization (TMR) is best demonstrated by the data collected from several multi-institutional randomized controlled trials. These trials are an important link between the preclinical data and the most common use of TMR (TMR + Coronary Artery Bypass Grafting). In addition to significant symptomatic relief both short- and long-term objective data were also garnered in these studies. A review of the history, study design, and outcomes is provided.

Transmyocardial laser revascularization

Transmyocardial laser revascularization (TMR) has been performed on over 12,000 patients worldwide. Since 1990, the treatment has provided significant angina relief for symptomatic end-stage coronary disease that is refractory to medical therapy. Seventy-five percent of patients treated with TMR have demonstrated a decrease of two or more angina classes postoperatively. As a result, TMR has provided a significant improvement in quality of life for patients, resulting in fewer hospital admissions and decreased dependency on medications. Two different wavelengths of light, carbon dioxide (CO(2)) and holmium yttrium-aluminum-garnet (Ho:YAG), have been employed. Results obtained using these lasers differ. The CO(2) laser has demonstrated a perfusion benefit as well as long-term improvement in quality of life and angina relief. The Ho:YAG laser has not demonstrated these results. These differences may, in part, explain the failure of percutaneous myocardial laser revascularization. This catheter-based approach was not as successful as TMR due to its partial thickness treatment of the myocardium as well as its use of the Ho:YAG laser. In addition to the patients with end-stage coronary disease who undergo TMR as sole therapy, there are an increasing number of patients who have been treated with a combination of coronary artery bypass grafting and TMR. This provides a more complete revascularization than leaving territories ungrafted. Further enhancement of the angiogenic response seen after TMR may be seen by the addition of gene therapy to TMR treatment.

One-year outcome after combined coronary artery bypass grafting and transmyocardial laser revascularization for refractory angina pectoris

Long-term outcomes after coronary artery bypass graft surgery (CABG) plus transmyocardial revascularization (TMR) are largely unknown. We report the results of 30-day and 3-, 6-, and 12-month clinical follow-up after CABG plus TMR in a consecutive series of patients with refractory angina pectoris and > or = 1 myocardial ischemic area not amenable to CABG. All patients who underwent CABG plus TMR (n = 169) (mean age 63 +/- 10 years, 70% men, 51% with previous CABG, 82% were deemed inoperable at other heart surgery centers due to small vessels or diffuse disease) between March 1996 and February 2000 were clinically followed and end points of interest (survival, stroke, acute myocardial infarction, and revascularization) and angina class were recorded at 30 days and 3, 6, and 12 months after CABG. At 1 year, actuarial survival and event-free survival were 85% and 81%, respectively. At the end of the first year after the procedure, 7 patients (4%) had angina class III/IV versus 152 patients (90%) at baseline (p <0.001). Predictors of major adverse cardiac events were advanced age (odds ratio [OR] 3.4, 95% confidence intervals [CI] 1.2 to 9.4, p = 0.01), prolonged intensive care unit stay (OR 3.3, CI 1.1 to 9.7, p <0.001), new-onset atrial fibrillation (OR 2.8, CI 1.1 to 7.0, p = 0.02), and in-hospital myocardial infarction (OR 1.5, CI 1.3 to 1.7, p <0.001). Thus, procedural success at 30 days and overall event-free and actuarial survival in a high-risk population setting shows that CABG plus TMR is a safe revascularization option for patients with intractable angina pectoris.

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.

Transmyocardial revascularization aggravates myocardial ischemia around the channels in the immediate phase

We examined whether transmyocardial revascularization (TMR) relieves myocardial ischemia by increasing regional perfusion via the transmural channels in acute canine experiments. Regional blood flow during transient coronary ligation (2 min) was compared before and 30 min after TMR, and at the third transient ischemia the mid-left ventricle (LV) was cut and immediately frozen along the short axis for the analysis of NADH fluorescence in the regions around the TMR channels. In low-resolution analysis (2-4 g tissue or 2-3 cm(2) area), regional perfusion was not significantly altered after TMR, and NADH fluorescence was observed throughout the ischemic region without significant spatial variation. High-resolution analysis (2.8 mg, 1 mm x 1 mm) revealed that the flow after TMR was lower, and NADH fluorescence was higher in the regions close to the channels (1-2 mm) than in the regions 3-4 mm away from them. Creating TMR channels did not improve the regional perfusion and rather aggravated the local ischemia in the vicinity of the channels in the immediate phase.

Evaluation of the indirect revascularization method after 3 months chronic myocardial ischemia

OBJECTIVE

The long-term effectiveness of transmyocardial laser revascularization (TMLR) was evaluated in the setting of a severe left anterior descending artery (LAD) stenosis.

METHODS

To employ the chronic ischemic model, pigs underwent three operative procedures over a 13-week period. In the first operation, an operative stenosis of the LAD was created. One week later, the animals were studied at baseline by analyzing different parameters of perfusion (microspheres), function and ECG changes. Afterwards, pigs were randomized into one of three different experimental groups: animals in laser group 1 received one laser channel (n=9) and laser group 2 two channels per cm(2) (n=6) in the LAD territory (using a CO(2)-laser). Animals of the ischemic group (n=12) underwent the same procedures without TMLR-treatment. Twelve weeks later, the animals were re-studied (third operation) and killed. Additional analysis of myocardial water content and histochemistry was performed.

RESULTS

Chronic myocardial ischemia and regional myocardial blood flow (RMBF) in laser group 2 revealed relatively higher RMBF values compared with the ischemic group (P=0.015), after 3 months, but no absolute improvement of perfusion at rest compared with baseline was observed in all experimental groups. Left ventricular stroke work index (LVSWI) at rest and under stress did not show any improvement compared with initial values in all study groups (P not significant). However, laser group 1 demonstrated relatively higher LVSWI(max) values in comparison with the ischemic group (P=0.013) as did laser group 2 (P=0.017). Regional contractility of the laser groups recovered after 3 months (which was deteriorated shortly after TMLR, P<0.001) and increased under stress compared with baseline (laser 1: P=0.015, laser 2: P=0.017). In contrast, the ischemic group did not show any difference from initial values (P not significant). The lased pigs of group 2 were less prone to intractable ventricular fibrillation (P=0.036 vs. ischemic group), and showed a significant smaller area of necrosis in the area at risk (P=0.012 vs. ischemic group).

CONCLUSIONS

This model of chronic regional ischemia demonstrates that CO(2)-laser revascularization significantly ameliorates microperfusion and regional contractility, and diminishes the incidence of ventricular fibrillation and necrosis in the area at risk. However, it does not change the overall perfusion and global LV function.

[Coronary artery bypass grafting in cases with poor left ventricular function]

From January 1987 through June 1992, 18 patients with poor left ventricular function (left ventricular ejection fraction [LVEF] less than 0.3) underwent elective isolated primary coronary artery bypass surgery. The mean age was 56.4 years (range, 46 to 72 years), and 15 were males and 3 were females. Mean pre-operative LVEF measured by ventriculography was 0.26 +/- 0.03 (range, 0.19 to 0.30). Sixteen patients (88.9%) had a prior myocardial infarction and 9 (50%) had a history of congestive heart failure. Complete revascularization was the goal for all patients, and the mean number of bypass grafts was 3.0 +/- 0.8 per patient. The left anterior descending coronary artery (LAD) was revascularized in all patients. There were no operative deaths. Post-operative LVEF improved significantly from 0.26 +/- 0.03 to 0.42 +/- 0.11 (p = 0.0002), and the regional left ventricular wall motion improved in the diaphragmatic and posterobasal regions (p < 0.01). The patency of the grafts was 93.9% in all, and 100% for LAD. The mean follow-up period was 77 months, and the overall actuarial survival rate was 88.9% at 10 years. During follow-up periods, two patients died of congestive heart failure (CHF), and two required three rehospitalizations because of CHF. The overall cardiac event free rate was 75.8% at 10 years. In patients with poor left ventricular function, surgical revascularization can be performed safely, but congestive heart failure sometimes occurs during follow-up periods and may be the cause of death. Therefore alternate forms of therapy such as cardiac transplantation and/or TMLR should be considered in selected patients.

Experimental and clinical studies on transmyocardial laser revascularization (TMLR)

The number of patients with coronary artery disease has been increasing and several kinds of treatments have been performed to alleviate their conditions. In patients with small branches or diffuse stenotic lesions of the coronary arteries, on whom coronary artery bypass grafting and intracoronary intervention cannot be carried out, it has been shown possible to supply arterial blood from the left ventricular cavity to the ischemic myocardium through laser channels. Arterial blood can be supplied hemodynamically from the left ventricular cavity to the ischemic myocardium. In trials on dogs laser channels 0.2 mm in diameter have been found to be histologically patent even 3 years after transmyocardial laser revascularization (TMLR). Thus, this procedure could be used as an alternative method of transmyocardial revascularization. We used TMLR on a 55-year-old male patient with severe angina pectoris who had undergone pericardiectomy 7 years ago. He is still alive more than 12 years after TMLR. This patient was among the first successful clinical cases in the world treated by TMLR alone. Therefore, this procedure should be recommended for the patients with end-stage coronary artery disease.

Transmyocardial laser-revascularization: experimental studies on prolonged acute regional ischemia

OBJECTIVE

This experimental study in pigs was undertaken to answer the question whether TMLR after acute myocardial infarction may improve regional myocardial perfusion, left ventricular function and diminish myocardial necrosis in the area at risk.

METHODS

Thirty open-chest anesthetized pigs were observed for 6 h, six pigs served as controls. In 24 pigs, occlusion of the left anterior descending artery (LAD) beyond the first diagonal branch was performed: seven pigs had LAD occlusion only (ischemia group), and 17 pigs were treated by TMLR (using a CO2-laser, energy: 40 J) prior to coronary occlusion; nine pigs received one laser channel (1 mm diameter) per cm2 (laser group 1) and eight pigs two channels per cm2 in the LAD territory (laser group 2). Regional myocardial blood flow by microspheres, function (franc starling curves), histochemical assessment (triphenyl tetrazolium chloride, TTC and histology), were performed.

RESULTS

The lased pigs were less prone to ventricular fibrillation (laser group 2, 38%; laser group 1, 56%; ischemic group, 100%; P < 0.05), and showed a significant smaller area of necrosis (TTC) in the area at risk (laser group 1, 23%; laser group 2, 14%; vs. ischemia group, 31%; P < 0.01). There was no significant difference between laser-treated and ischemia hearts regarding the amount of blood flow into the infarcted LAD region and the maximal left ventricular stroke work index after 6 h (P = n.s). Regional myocardial blood flow: ischemia group, 4 +/- 5 ml/100 g/min; laser group 1, 3 +/- 10 ml/100 g/min, and laser group 2, 2 +/- 10 ml/100 g/min; maximal left ventricular stroke work index: ischemia group, 1.8 mJ/g; laser group 1, 2.1 mJ/g and laser group 2, 2.1 mJ/g.

CONCLUSIONS

This model of acute regional ischemia demonstrates that CO2-laser revascularization diminish significantly the incidence of ventricular fibrillation and necrosis in the area at risk, and does not change regional myocardial perfusion and global left ventricular function. This experiment indicates that TMLR may be an alternative in treating advanced ischemic heart disease.

Myocardial angiogenesis as a possible mechanism for TMLR efficacy

Despite advances in the treatment of ischemic heart disease, there still exists a significant number of individuals for whom bypass surgery or angioplasty are not options. Transmyocardial laser revascularization (TMLR) is a promising technology that has already been shown to reduce symptoms in patients with chronic ischemic heart disease that is not amenable to conventional therapies. Although it appears that TMLR can provide symptomatic relief of angina in selected patients, the mechanism by which TMLR is thought to work is unclear. Recently it has been postulated that TMLR induces an angiogenic response and, perhaps, improves local perfusion to ischemic myocardial territories. A brief overview of the biology of myocardial angiogenesis is presented.

Percutaneous transmyocardial revascularization

Transmyocardial revascularization (TMR) is a potential therapy for patients with severe angina pectoris and coronary anatomy deemed unsuitable for traditional revascularization techniques. Investigations of TMR are reviewed with emphasis on studies relevant to the development of a percutaneous, catheter-based transmyocardial revascularization procedure (PMR). The results of the preliminary animal studies and description of the PMR procedure are discussed. The recently initiated human PMR protocol is summarized and possible future investigative directions are outlined.

Transmyocardial laser revascularization: results of a multicenter trial with transmyocardial laser revascularization used as sole therapy for end-stage coronary artery disease

BACKGROUND

Transmyocardial laser revascularization was used as the sole therapy for patients with ischemic heart disease not amenable to percutaneous transluminal coronary angioplasty or coronary artery bypass grafting. This technique uses a carbon dioxide laser to create transmyocardial channels for direct perfusion of the ischemic heart.

METHODS

Since 1992, 200 patients, at eight hospitals in the United States, have undergone transmyocardial laser revascularization. The patients have a combined 1560 months of follow-up for an average of 10 +/- 3 months per patient. Their age was 63 +/- 10 years and their ejection fraction was 47% +/- 12%. Eighty-two percent had at least one previous bypass graft operation and 38% had a prior angioplasty. Preoperatively, the patients underwent nuclear single photon emission computed tomography perfusion scans to identify the extent and severity of their ischemia. These scans were repeated at 3, 6, and 12 months. Angina class, admissions for angina, and medications were recorded.

RESULTS

The perioperative mortality was 9%. Angina class decreased significantly from before treatment to 3, 6, and 12 months (p < 0.001). Likewise, there was a significant decrease in the number of perfusion defects in the treated left ventricular free wall. Concomitantly, there was a significant decrease in the number of admissions for angina in the year after the procedure when compared with the year before treatment (2.5 vs 0.5 admissions per patient-year).

CONCLUSION

These combined results indicate that transmyocardial laser revascularization provides angina relief, decreases hospital admissions, and improves perfusion in patients with severe coronary artery disease.

Laser-tissue interaction during transmyocardial laser revascularization

BACKGROUND

The clinical procedure known as transmyocardial revascularization has recently seen its renaissance. Despite the promising preliminary clinical results, the associated mechanisms are subject to much discussion. This study is an attempt to unravel the basics of the interaction between 800-W CO2 laser radiation and biological tissue.

METHODS

Time-resolved flash photography was used to visualize the laser-induced channel formation in water and in vitro porcine myocardium. In addition, laser-induced pressures were measured. Light microscopy and birefringence microscopy were used to assess the histologic characteristics of laser-induced thermal damage.

RESULTS

The channel depth increased logarithmically with time (ie, with pulse duration) in water and porcine myocardium. Pressure measurements showed the occurrence of numerous small transients during the laser pulse, which corresponded with channel formation, as well as local and partial channel collapse during the laser pulse. Twenty millimeters of myocardium was perforated in 25 ms. Increasing the pulse duration had a small effect on the maximum transversable thickness, but histologic analysis showed that thermal damage around the crater increased with increasing pulse duration.

CONCLUSIONS

Several basic aspects of the interaction of high-power CO2 laser radiation with myocardial tissue and tissue phantoms were studied in vitro. Although the goal of this study was not to unravel the mechanisms responsible for the beneficial effects of transmyocardial revascularization, it provided important information on the process of channel formation and collapse and tissue damage.

Percutaneous method of laser transmyocardial revascularization

Laser transmyocardial revascularization (TMR) creates conduits from the left ventricular cavity into the myocardium and has been forwarded as a potential method of perfusing ischemic myocardium. The procedure typically employs a CO2 laser to produce transmyocardial channels from the epicardial to the endocardial surface via an open thoracotomy. Preliminary studies in animals and human subjects have yielded promising results, and clinical trials evaluating the long-term efficacy of the procedure are in progress. We now report the use of a percutaneous method of TMR using a laser delivered through a novel catheter system. To assess the feasibility of performing percutaneous TMR, studies were performed on 15 adult canine subjects utilizing a holmium:YAG laser. Via a femoral artery approach, novel laser catheters were introduced into the left ventricular cavity under fluoroscopic guidance. Biplane coronary angiography, ventriculography, and transesophageal echocardiography were employed to direct catheters to specific regions and assess the efficacy of creating transmyocardial channels. Multiple channels could be created in the anterior, lateral, inferoposterior, and septal regions as demonstrated by contrast ventriculography with confirmation by subsequent gross and histologic examination. The procedure was tolerated well without any ventricular dysfunction or sustained ventricular arrhythmias. We have demonstrated that laser transmyocardial revascularization via a percutaneous approach is feasible with creation of channels from the endocardial surface of the left ventricle into the myocardium. On gross and histological examination, these channels are similar in appearance to those created by the currently employed open chest, epicardial method of TMR.

Patient care and expectations for recovery after transmyocardial laser revascularization

Transmyocardial laser revascularization is an investigational cardiovascular surgical procedure that has been trialed in the United States since 1991. The procedure involves the use of a high-energy carbon dioxide (CO2) laser to penetrate ischemic myocardium of the left ventricle. The successful formation of patent laser channels results in the formation of a new circulation within the myocardium. This angiogenesis has shown to improve perfusion to the previously oxygen-deprived tissue. To date, more than 500 patients have undergone this procedure in the United States, and approximately 1,500 cases have been performed in Europe, Asia, and the Middle East. The perioperative nursing care for these patients is multifaceted, including, but not limited to, the need for noninvasive assessment skills, effective pain management, and thorough discharge teaching. Unlike other cardiovascular procedures, this surgery does not immediately repair the ischemic areas; recovery is an insidious process. A realistic understanding of this surgery is needed to assist the patient throughout his or her hospitalization and to properly prepare the individual for expectations of recovery after discharge.

Transmyocardial laser revascularization: operative techniques and clinical results at two years

OBJECTIVES

A new technique, transmyocardial laser revascularization, provides direct perfusion of ischemic myocardium via laser-created transmural channels. From 1993 to 1995, we have treated 20 patients (mean age 61 years, four women and 16 men) with transmyocardial laser revascularization. Preoperatively, the average angina class was 3.7. The patients were screened before the operation by a technetium sestamibi perfusion scan to identify the location and extent of their reversible ischemia.

METHODS

Operative exposure is gained via a left anterior thoracotomy. With the use of a 850-watt carbon dioxide laser, an average of 21 +/- 4 channels were created in 22 minutes with a total operative time of less than 2 hours.

RESULTS

The in-hospital mortality was two of 20 patients. Three additional patients died after discharge. After an accumulated 172 patient-months (mean follow-up 11 +/- 8 months, range 1 to 26 months), the mean angina class is I (p = 0.01). Postoperative sestamibi scans were obtained at 3, 6, and 12 months. Using the septum as a control and comparing the postoperative results with the preoperative baseline, we noted a significant improvement in perfusion particularly in the areas of reversible ischemia.

CONCLUSION

These early results indicate that transmyocardial laser revascularization is a simple operative technique that may improve myocardial perfusion and provide angina relief for patients in whom standard methods of revascularization is contraindicated.

Does blood flow through holmium:YAG transmyocardial laser channels?

BACKGROUND

Early reports indicate that transmyocardial laser revascularization improves symptoms in patients with refractory angina. However, there is little experimental evidence of whether blood flow through channels is the mechanism of action.

METHODS

Endocardial channels were made in the distribution of the left anterior descending coronary artery in canine hearts (n = 5) using a holmium:yttrium-aluminum garnet laser. Hearts were excised acutely while perfused in a retrograde fashion from a second dog so that the aortic valve always remained closed. The proximal left anterior descending coronary artery was ligated. To measure direct transmyocardial blood flow, colored microspheres were injected into the left ventricular chamber.

RESULTS

The number of spheres per gram of tissue in the channel region was significantly higher than in the control region (low load, 302.5 +/- 169.0 versus 41.8 +/- 59.4; high load, 208.4 +/- 138.3 versus 5.8 +/- 11.7; both, p < 0.05). However, the estimated regional blood flow through the channels was extremely low (<0.01 mL/g/min. In the chronic setting (n = 4) (2-week survival), no flow as detected through the channels, and the endocardial entry points were closed.

CONCLUSIONS

Transmyocardial blood flow does not appear to occur through channels made with the holmium:yttrium-aluminum garnet laser. It remains to be determined whether this is the case with other types of lasers.

Techniques to enhance extramyocardial collateral blood flow after a cardiomyoplasty

OBJECTIVE

Chronic stimulation of a cardiomyoplasty was combined with low-dose infusion of heparin into the arterial supply of the cardiomyoplasty in order to determine if latissimus-derived collateral blood flow could be further enhanced.

SUMMARY BACKGROUND DATA

Acute and chronic stimulation of a latissimus dorsi cardiomyoplasty increased extramyocardial collateral blood flow to 35 +/- 9% and 27 +/- 5%, respectively, of normal myocardial blood flow.

METHODS

A model of coronary artery disease was created with an ameroid constrictor in goats, and a cardiomyoplasty was performed. Heparin (15 to 50 U/h) was delivered into the left subclavian artery for a period of 4 weeks. Simultaneously, the latissimus dorsi was chronically stimulated at 2 Hz.

RESULTS

Chronic ischemic myocardium received a collateral flow per gram from the skeletal muscle equivalent to 11.8 +/- 5.2% of the blood flow to normal myocardium. The extramyocardial collateral flow correlated with the latissimus muscle flow (r = 0.72).

CONCLUSIONS

Enhancement of extramyocardial collateral flow was not found with heparin treatment. In view of the correlation of extra-coronary collateral flow with latissimus muscle flow, the lack of a heparin effect may have been due to low latissimus blood flow. These results suggest that extramyocardial collateral blood flow to the myocardium is highest if the blood flow to the latissimus dorsi muscle is maintained.

Laser-mediated transmural myocardial channels do not salvage acutely ischemic myocardium

OBJECTIVES

We sought to determine whether the presence of transmural laser-made channels could provide blood flow to ischemic myocardium.

BACKGROUND

Laser-made transmural channels have been used in patients to restore blood flow to ischemic myocardium. Whether such channels actually relieve ischemia is unclear. We therefore tested the concept in an animal model of acute ischemia.

METHODS

Eighteen dogs underwent 6 h of permanent coronary artery occlusion. At 30 min after occlusion, 8 dogs were randomized to the laser-treated group (30 to 40 transmural channels, 1 mm in diameter, were made in the cyanotic area using a holmium: yttrium-aluminum-garnet laser), and 10 were randomized to the control group (no treatment). Transmural blood flow was measured before and after treatment using radiolabeled microspheres. Regional segment shortening and myocardial lactate content were measured in four of the control and two of the laser-treated dogs. Infarct size was measured in all animals using triphenyltetrazolium chloride staining.

RESULTS

Laser channels failed to increase blood flow to ischemic tissue. After laser channels were made, mean transmural flow averaged 0.10 +/- 0.03 versus 0.11 +/- 0.03 ml/min per g in treated versus control dogs, respectively. Furthermore, infarct size was similar in both groups (46 +/- 6% vs. 43 +/- 7%, respectively, of the myocardium at risk, p = NS). In addition, the presence of laser channels neither improved regional myocardial function nor enhanced washout of accumulated lactate.

CONCLUSIONS

Direct laser revascularization of the heart did not provide any immediate benefit to ischemic myocardium in this canine model of coronary artery occlusion. Thus, it is doubtful that direct laser-mediated myocardial revascularization would be of immediate benefit in the treatment of patients with acute ischemia.