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Ann Thorac Surg 2005;80:2082-2085
© 2005 The Society of Thoracic Surgeons
a National Heart, Lung, Blood Institute, National Institutes of Health, Bethesda, Maryland
b Louisiana State University Health Sciences Center, New Orleans, Louisiana
c Emory University School of Medicine, Division of Cardiothoracic Surgery, Atlanta, Georgia
d University of Florida, Shands Jacksonville, Division of Cardiothoracic Surgery, Jacksonville, Florida
Accepted for publication June 7, 2005.
* Address correspondence to Dr Horvath, NHLBI, Bldg 10CRC, Room 6-5140, MSC 1454, National Institutes of Health, 10 Center Dr, Bethesda, MD20892 (Email: khorvath{at}nih.gov).
| ADULT CARDIAC SURGERY: To participate in The Annals of Thoracic Surgery CME Program, please visit http://cme.ctsnetjournals.org.
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Abstract |
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 Top Abstract IntroductionPatients and MethodsResultsCommentReferences |
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METHODS: Using The Society of Thoracic Surgeons National Cardiac Database from 1998 to 2003, 5,618 patients underwent TMR plus CABG. These patients were compared with 932,715 patients who underwent CABG only operations.
RESULTS: The TMR plus CABG patients had a significantly higher incidence of diabetes (50% versus 34%), renal failure (7% versus 5%), peripheral vascular disease (20% versus 16%), reoperative surgery (26% versus 9%), three-vessel coronary artery disease (80% versus 71%), hyperlipidemia (73% versus 62%; p < 0.001 for all comparisons). The incidence of preoperative unstable angina was similar (46% versus 47%). The unadjusted perioperative mortality was 3.8% for TMR plus CABG patients. When unstable angina patients were removed, the observed mortality for TMR plus CABG was decreased to 2.7%.
CONCLUSIONS: It is likely that patients who undergo TMR plus CABG have a higher prevalence of diffuse coronary disease based on their preoperative demographics. Despite the increased risk associated with such anatomy, the mortality rate was not significantly increased when TMR was added to CABG in an effort to provide a more complete revascularization. As was noted from the outcomes of sole therapy TMR, in unstable angina patients, TMR plus CABG carries a higher risk, but this risk is not significantly different from that of such patients treated with CABG alone.
Based largely on the results of five randomized controlled trials comparing sole therapy transmyocardial laser revascularization (TMR) to maximal medical therapy in 937 patients with diffuse coronary disease, TMR was approved for use by the Food and Drug Administration in 1998 [1–5]. All of these trials documented significant angina relief for patients treated with TMR versus those who were treated with medication alone. In addition to the symptomatic improvement, and concomitant improvement in quality of life, objective evidence of improved function and perfusion was also documented for TMR patients [1–6]. Observational data on more than 1,700 TMR patients have been reported and corroborate the randomized controlled trial results.
As the technique of operative TMR is straightforward, the key to the success of the procedure is appropriate patient selection. One of the important lessons learned from both the randomized and nonrandomized studies was the impact that unstable angina had on outcomes in patients undergoing sole therapy TMR. Patients who were experiencing angina and who could not be weaned from intravenous nitroglycerin and heparin had a significantly higher operative mortality rate (16% to 27% versus 1% to 3%) [1, 7]. Based on these findings, clinical practice has been to avoid taking such patients to the operating room for sole therapy TMR if at all possible. As a result of this experience the Society of Thoracic Surgeons practice guidelines state that sole therapy TMR for unstable angina is a class IIB indication [8].
Having demonstrated the symptomatic benefit of TMR in isolation as sole therapy, the use of TMR in combination with coronary artery bypass graft surgery (CABG) has been performed and reported [9–13]. Randomized controlled trials of TMR plus CABG demonstrate the safety and efficacy of this procedure [10, 13]. The use of TMR plus CABG has provided surgeons the means to perform a more complete revascularization for patients with severe coronary artery disease who have ungraftable territories of their myocardium. As a result of this diffuse disease (and similar to the sole therapy TMR patients), some TMR plus CABG patients are experiencing unstable angina immediately before their operation. Whether unstable angina is an independent predictor of morbidity and mortality for TMR plus CABG patients is unknown. It has been suggested that the addition of TMR to CABG increases the risk for any patient. The purpose of this study was to determine the impact of unstable angina on the outcomes of patients treated with TMR in combination with CABG. To accomplish this, The Society of Thoracic Surgeons (STS) National Cardiac Database was queried.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Patient Population
Between January 1998 and December 2003, all patients enrolled in the STS database were identified. Of these patients, 5,618 underwent TMR in combination with CABG. These patients were compared with 932,715 patients who underwent isolated CABG procedures during the same interval.
Statistical Analysis
Categorical variables are presented as percentages whereas continuous variables as median in interquartile ranges unless otherwise stated. The 
2 and Kruskall-Wallis tests were used to compare characteristic across groups of patients for categorical and continuous variables, respectively.
Logistic regression was used to identify univariate and multivariate preoperative risk factors from affecting perioperative morbidity and mortality outcomes after TMR plus CABG. Comparison of TMR plus CABG versus isolated CABG patients was performed. A comparison TMR plus CABG versus CABG alone in underrevascularized patients (as defined as having three-vessel coronary artery disease but receiving only one or two bypass grafts) was also performed. Comparison of the crude and risk-adjusted outcomes for TMR plus CABG versus isolated CABG were adjusted for 28 preoperative risk factors associated with morbidity and mortality.
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Results |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Comparison of Patient Characteristics
Table 1
provides a comparison of baseline patient demographics between patients who underwent isolated CABG versus patients who underwent TMR plus CABG. Table 1 demonstrates that patients undergoing TMR plus CABG had a significantly higher prevalence of risk factors than did isolated CABG patients. Transmyocardial laser revascularization plus CABG patients had a higher incidence of all types of diabetes in general and insulin-dependent diabetes specifically. Additionally, there were higher rates of renal failure, dialysis, stroke, chronic lung disease, peripheral vascular disease, cerebrovascular disease, hypertension, and hypercholesterolemia. Other significant cardiac risk factors known to impact morbidity and mortality included a higher incidence of prior myocardial infarction, previous cardiac surgery, and three-vessel coronary artery disease. The incidence of unstable angina was similar at 47% for CABG patients and 46% for TMR plus CABG patients (p = 0.23). The definition of unstable angina used in the STS database was angina, which necessitates the initiation, continuation, or increase of angina control therapies that may include nitroglycerin drip, heparin drip, or intra-aortic balloon pump placement. This definition was slightly less restrictive than that used in the sole trials of TMR in which the designation of unstable angina required that an attempt at weaning of intravenous theapy had been unsuccessful during the 2 days before operation.
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In an attempt to determine the impact of adding TMR to an isolated CABG operation, patients who had three-vessel coronary artery disease but received only one or two bypass grafts were compared with the same type of patient who received one or two grafts plus TMR for the treatment of their three-vessel disease. The baseline demographics for these patients are listed in Table 2. In these patients who were "underrevascularized," the use of TMR plus CABG was 1.8% of the national CABG volume. At TMR sites, the use of TMR in combination with CABG for these patients was 3.0% of the sites' revascularization volume. Table 2 also reiterates that the TMR plus CABG patients have higher incidences of many preoperative risk factors, especially those associated with diffuse atherosclerosis. There was no difference in the incidence of preoperative unstable angina between these "underrevascularized" groups. The unadjusted operative mortality was 4.3% for isolated CABG compared with 5.2% for TMR plus CABG. This difference was not statistically significant (p = 0.13). The expected mortality rate for these patients undergoing TMR plus CABG is 4.81%, and the ensuing O/E ratio is 1.08.
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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The limitations of this study include the fact that the STS database is a voluntary database that represents two thirds of the national cardiac surgery sites. Additionally, when considering the "underrevascularized" patients, it is unclear from the database whether these patients received grafts to only one territory, whether previous infarction obviated the need for revascularization to a territory, or whether coronary artery anatomic variations precluded the need for all territories to be grafted. The quality and size of distal vessels is also not captured by the database, but clinical surrogates such as diabetes mellitus suggests that the use of TMR plus CABG is being appropriately employed to provide a more complete revascularization for such patients. The STS database captures perioperative information but does not provide any data for long-term analysis. Long-term follow-up of the two previously reported randomized controlled trials of TMR plus CABG versus CABG alone indicate that there is a significantly lower average angina score at 5 years, 0.4% versus 0.7% (TMR plus CABG versus CABG, p < 0.05) [14]; fewer patients in angina class III or IV, 0% versus 10% (TMR plus CABG versus CABG, p < 0.05) [14]; and a lower incidence of repeat revascularization, 0% versus 24% (CABG plus TMR versus CABG, p < 0.05) [13].
The combination of TMR plus CABG has been criticized as "off label." The labeling indications specify that TMR is for patients with angina that is refractory to medical therapy and secondary to objectively demonstrated coronary artery atherosclerosis that is not suitable for direct coronary revascularization [15, 16]. The specific labeling for TMR in combination with CABG was not made because the randomized controlled trials on which the FDA approval was granted were studies of TMR as sole therapy. The demonstration of efficacy of TMR as sole therapy led to the concomitant use of TMR with CABG in regions of the myocardium not amenable to conventional revascularization. Further concern that there is inappropriate "widespread" use of TMR in combination with CABG also appears unfounded. The number of sites performing TMR has increased, and with this increase, the number of patients undergoing TMR plus CABG has increased. This is largely reflective of the type of patients who are now referred for surgical revascularization. The average number of TMR plus CABG cases per site has not increased, remaining on average at less than one case per month per site.
It is difficult to determine the precise impact of unstable angina on the outcomes of patients undergoing TMR plus CABG. That is particularly true as any report needs to identify which definition of unstable angina is being used. In patients who are unweanable from intravenous antianginal medications, the more rigorous definition used in the TMR sole therapy trials, TMR as sole therapy had a higher early mortality rate than for patients with chronic stable angina. Such unstable patients are likely to benefit more from the instantaneous revascularization that CABG provides as opposed to the delayed benefit associated with TMR. When considering the use of TMR in combination with CABG for patients with unstable angina, understanding what myocardial territory is the source of the instability and whether that area can be grafted may play a role. Nevertheless, the data on unstable angina patients from the STS database indicate that for a patient population that carries significantly higher risk, the addition of TMR does not unduly increase that risk. This is particularly true when the short-term mortality for first-time CABG or reoperative CABG in patients with unstable angina is 6% to 7% [17–19].
It is likely that patients who undergo TMR plus CABG have a higher prevalence of diffuse coronary disease based on their preoperative demographics. This prevalence and extent of diffuse coronary artery disease is not well captured by the STS database. The use of surrogates for diffuse coronary disease from the preoperative demographics are therefore important, but may underestimate the true operative mortality risk in these patients. Despite the increased risk associated with such anatomy, mortality was not significantly increased when TMR was added to CABG in an effort to provide more complete revascularization. As was noted from the outcomes of sole therapy TMR, TMR plus CABG for unstable angina patients is associated with a higher risk, but this risk is not significantly different from that of CABG alone in these patients.
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This article has been cited by other articles:
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  K. A. Horvath and Y. Zhou Transmyocardial Laser Revascularization and Extravascular Angiogenetic Techniques to Increase Myocardial Blood Flow Card. Surg. Adult, January 1, 2008; 3(2008): 733 - 752. [Full Text]
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