Patients' profiles in end stage coronary artery disease. Indications for treatment with transmyocardial laser revascularisation.

There is a subgroup of patients with coronary artery disease who are refractory to the therapeutical methods so far applied. We report on 128 patients who fulfill this definition and have therefore undergone pure transmyocardial laser revascularisation (TMLR) or transmyocardial laser revascularisation in combination with coronary bypass surgery at our institution. The patients can be characterized by a long history of coronary artery disease with multiple revascularizing procedures, e.g. bypass surgery or percutaneous transluminal coronary angioplasty (PTCA), pronounced symptoms of coronary artery disease and chronic heart failure in the presence of markedly reduced left ventricular ejection fractions and intense antiischemic medical therapy. The patients were 62.2 +/- 9.8 (SD) years of age, in 89.9% of them at least one bypass operation and in 44.5% up to more than three percutaneous transluminal coronary angioplasties (PTCAs) had been performed prior to TMLR. There was a history of myocardial infarction in 90.7% of patients and 89.8% were in the Canadian Cardiovascular Society (CCS) classes III or IV and 94.5% of them were in the NYHA classes III or IV. The left ventricular ejection fraction was 49.5 +/- 16.4% and all of the patients were under intense antiischemic medical treatment which included nitrates or molsidomine in 96.9%, beta blockers in 53.1%, angiotensin converting enzyme inhibitors (ACE inhibitors) in 44.5%, digitalis in 22.7% and diuretics in 52.3% of patients. The preoperative data on myocardial viability, inducible ischemia and coronary morphology provided important clinical information for the decision, which revascularizing method would be the most appropriate for each vessel or myocardial region. This had to be weighed against the patient's operative risk, which is predominantly determined by the left ventricular ejection fraction, the arteriosclerotic involvement of the remaining vascular system and concomitant diseases, particularly of pulmonary origin.

[Transmyocardial laser revascularization--an innovative pathophysiologic concept]. / Transmyokardiale Laserrevaskularisation--ein innovatives pathophysiologisches Konzept.

In patients with coronary artery disease where standard revascularization procedures are not appropriate, transmyocardial laser revascularization (TMLR) represents an innovative technique which is currently validated worldwide. Initially, it has been assumed that myocardial perfusion of ischemic regions could be instantly improved by inducing TMLR channels, which, however, might not be confirmed in ongoing studies. Indeed, the gain in O2 diffusion surface obtained by 20 patent TMLR channels is only 6 cm2 which accounts for just 0.01% of the total capillary surface (47000 cm2) of the myocardium. Instead, a chronic structural remodeling of myocardial regions, adjacent to TMLR channels and mediated by TMLR-induced expression of vascular endothelial growth factor (VEGF), may occur leading to neocapillarization of ischemic myocardium irrespective of the long-term patency of TMLR channels and, thereby, would improve myocardial perfusion (Figure 1). Six weeks following TMLR in the pig, patent TMLR channels were not observed. Instead, a marked degree of reparative fibrosis was found at the site of TMLR-treated myocardial regions (Figure 2). It is, however, not known, whether ischemic conditions would affect chronic channel patency. TMLR combined with intramyocardial administration of 0.5 microgram VEGF between the laser-induced channels resulted in few patent channels (Figure 3). The apparently low efficacy of VEGF applied as protein could be attributed to degradation of VEGF by local peptidases. In addition to VEGF, other growth factors and the interaction of endothelial cells and the extracellular matrix need to be considered. Of particular relevance appears alpha v beta 3-integrin which is needed for adhesion of endothelial cells to extracellular matrix components and is, therefore, required for neocapillarization. Among various other growth factors associated with neoangiogenesis, TGF-beta 1 and PDGF-BB are involved in the formation of extracellular matrix anchoring newly formed vessels. Thus, the expression of VEGF and alpha V beta 3-integrin in myocardial regions surrounding TMLR channels appears to be of major importance for the development of neoangiogenesis within the ischemic myocardium. Whether concomitant therapeutical strategies, i. e., gene transfer leading to over-expression of VEGF, will optimize the TMLR procedure by improving neoangiogenesis remains to be elucidated in future experimental studies.

[Transmyocardial laser revascularization in stable and unstable angina pectoris]. / Transmyokardiale Laserrevaskularisation bei stabiler und instabiler Angina pectoris.

Endstage coronary artery disease still remains a therapeutic challenge. An increasing number of patients is no longer amenable for direct revascularization by PTCA or coronary bypass surgery and does also no longer respond to maximum medical therapy. This fact has directed the interest again towards surgical techniques of indirect revascularization, which had been introduced by Beck and other surgeons more than 60 years ago. Among these attempts we can also find transmyocardial needle punctures, firstly performed by Sen in Bombay. In the early eighties it was Mirhoseini, who used a laser for creating these transmural channels, primarily in combination with coronary bypass surgery at the arrested heart and later on together with Crew as a sole therapy at the beating heart. The idea behind this transmyocardial laser revascularization (TMLR) was a "reptilization" of the human heart, which meant a direct blood supply from the ventricle into the ischemic myocardium. Whereas this theory has not proven to be true, as the surface area of these channels is not sufficient for the nutrition of the surrounding myocardial tissue by diffusion or convection, different models have been developed by anatomical, experimental and clinical studies, such as the connection between the laser channels and intramyocardial vessels or capillaries, analogous to ventriculo-coronary connections in human anatomy or pathology as for example those connections described in children with pulmonary atresia and intact ventricular septum or the Thebesian veins. Moreover the laser trauma may also simply contribute to the induction of neoangiogenesis. While the function of TMLR is still not clearly defined, clinical studies in the United States and also in other countries have proven the clinical efficacy in a cohort of severely diseased patients undergoing this procedure. Accordingly more than 2/3 of all patients after TMLR showed a significant improvement of more than 2 angina classes (CCS) as well as a decrease in medication and hospitalization. Moreover there was also a reduction of ischemic areas demonstrated by szintigraphy and, in one study from Houston, also by positron emission tomography. While the overall mortality in all those studies is still considerably high, a reduction could be achieved by a stricter selection of patients excluding especially those with a severely impaired left ventricular function. As demonstrated by preliminary data from the last phase III FDA-study, TMLR may even reduce long-term mortality compared to maximum medical therapy in a randomized group of patients. Our own experiences in 134 patients also confirmed a significant reduction of angina after TMLR alone (n = 67) or in combination with bypass surgery (n = 67) with the majority of patients being in angina class 1 and 2 (CCS) 6 months after surgery. All of these patients were in angina class 3 and 4 before surgery. Nuclear scans could demonstrate an improved perfusion in more than 40%. Further studies as well as other clinical and also experimental investigations have still to be awaited, before the definitive role of TMLR within the armamentarium against coronary artery disease can be determined. However, it is already a therapeutic option for those highly symptomatic patients, who cannot be offered a different treatment modality.