Changes in cardiac adrenergic nervous system after transmyocardial laser revascularisation assessed by I-123-MIBG SPECT. A preliminary report

Background: Metaiodobenzylguanidine (MIBG), a noradrenaline analogue which may be labelled with I-123, has been used in the assessment of pre-synaptic activity of the cardiac adrenergic nervous system (Systadren) in several diseases. The effects of transmyocardial laser revascularisation (TMLR) on Systadren have not yet been established.Aim: To examine whether TMLR-induced changes in Systadren may be one of the mechanisms responsible for clinical improvement in patients undergoing this method of revascularisation.Methods: The study group consisted of 19 patients (mean age 63±9 years) who underwent TMLR, by using high-power CO2 laser; as a single method of cardiac revascularisation. Systadren was assessed before TMLR (STUDY-0), soon after the procedure (mean 13±5 days, STUDY-I), and in 12 patients six months after TMLR (STUDY-II). In total, 50 studies using I-123-MIBG SPECT were performed. The regional distribution of tracer was assessed qualitatively, using a 17-segment model of the left ventricle.Results: In 16% of examinations the assessment of the I-123-MIBG uptake was not possible due to the poor quality of images. Thus, 41 SPECT studies (16 - STUDY-0, 16 - STUDY-I, and 9 - STUDY-II) were analysed and compared. In STUDY-0, an impaired uptake of I-123-MIBG was found in 193 of 272 analysed segments. In STUDY-I, the I-123-MIBG uptake increased in 5% of defects (CI0,95=3-9%) and deteriorated in 55% (CI0,95=48-62%). When STUDY-II was compared with baseline, the uptake was increased in 25% of defects (CI0,95=17-34%) and decreased in further 25% of defects. When STUDY-II was compared with STUDY-I, the uptake increased in 67% (CI0,95=58-75%) of defects and did not deteriorate in any. The global MIBG uptake in STUDY-I decreased in 15 patients (94%, CI0,95=70-100%) when compared with baseline, and increased in all 9 patients with long-term follow-up data available, when STUDY-II to STUDY-I was compared.Conclusions: TMLR significantly deteriorates Systadren activity which, however, improves 6 months after the procedure to the values similar to those assessed pre-operatively. TMLR-induced impairment of Systadren may contribute to the clinical improvement observed shortly