Extreme coronary radiation doses from intravascular brachytherapy.

PURPOSE: To evaluate coronary artery integrity after very high radiation doses from intravascular brachytherapy (IVBT) in the setting of source asymmetry. METHODS: Ten patients treated for right coronary artery (RCA) in-stent restenosis (ISR) between 2017 and 2021 and for whom follow-up angiograms were available were identified from departmental records. Procedural angiograms, taken to document source position, were used to estimate vascular wall doses. The 2.5 mm proximal source marker was used to estimate the distance from source center to the media and adventitia. Distances were converted to dose (Gy) using the manufacturers' dose fall-off table, measured in water. Follow-up films were scrutinized for any sign of late vascular damage. RESULTS: The average minimal distance from catheter center to the adjacent media and the adventitia was 0.9 mm (±0.2) mm and 1.4 mm (±0.2), respectively. The average maximum media and adventitial doses adjacent to the source were 75 Gy (±26) and 39 Gy (±14), respectively. Follow-up angiograms were available from 0.6 years to 3.9 years following IVBT (median: 1.6 years). No IVBT-treated vascular segment showed signs of degeneration, dissection or aneurysm. CONCLUSION: IVBT vascular wall doses are frequently far higher than prescribed. The lack of complications in this unselected group of patients gives a modicum of reassurance that raising the prescription dose is unlikely to lead to a sudden appearance of complications.

Failure patterns after intravascular brachytherapy for in-stent coronary restenosis.

INTRODUCTION: One strategy to improve the effectiveness of intravascular brachytherapy (IVBT) is to study its failures. Previous investigations described mostly discrete, focal recurrences, typically at the proximal or distal edges of the irradiated segment after plain angioplasty or bare metal stents. We reviewed failure patterns of 30 unselected drug-eluting stent (DES) patients who had follow-up angiograms for recurrence within their IVBT-treated vessel. METHODS: Records of 53 unselected IVBT patients treated between 2016 and 2021 were reviewed. Thirty of the 53 patients had at least one subsequent percutaneous intervention (PCI) for in-stent restenosis (ISR) after IVBT. Angiographic findings of those 30 patients with ISR within their previously irradiated vessel are reported here. RESULTS: Of the 30 patients, 21 (70%) developed recurrent ISR within the irradiated segment. Six of the 21 patients who failed within the irradiated segment also experienced ISR proximal or distal to the irradiated segment. Only 15 patients (50%) failed exclusively within the irradiated segment. In nine patients (30%), restenosis occurred proximally and/or distally to the irradiated segment, but not inside of the irradiated segment itself. CONCLUSIONS: We have shown here that 50% of failures after coronary IVBT for DES ISR occur exclusively within the irradiated segment. An additional 20% of patients had failure within and outside of the irradiated segment. These percentages suggest that a higher radiation dose might improve the long-term patency rates, a conclusion that should be tempered by the lack of universal follow-up.

Intravascular coronary brachytherapy combined with a drug-coated balloon.

BACKGROUND: Coronary artery disease leads to stenosis of the major cardiac vessels, resulting in ischemia and infarction. Percutaneous intervention (PCI) with balloon angioplasty can re-open stenosed vessels. Drug eluting stents (DES) and intravascular brachytherapy (IVBT) and drug-coated balloons (DCBs) are proven to decrease the likelihood of another restenosis after PCI, but neither is completely effective. Due to the limited long-term effectiveness of IVBT or DCB used separately for salvage PCI, we combined the two in some poor prognosis patients. METHODS: Combined IVBT+DCB was intended for a total of 36 patients from 2015-2020. PCI with some combination of ballooning, laser and directional/rotational atherectomy was used to maximally open the stenotic region prior to IVBT+DCB. Beta-radiation brachytherapy for all patients was done with a Novoste Beta-Cath. Lutonix 4.0 x 40 mm paclitaxel-coated balloons (Bard, Murray Hill, NJ) were employed. RESULTS: Overall survival at two years was 88%. Nine patients had follow-up angiograms, all for cardiac symptoms. Time from IVBT+DCB to follow-up angiography ranged from 4 to 33 months. The average months PCI-free interval before brachy therapy was 11.1 mos (95% CI 1.03-23.25) versus 23.3 mos after VBT (23.3 95% CI 12.3-32.3). The mean difference was 11.2 mos (95% CI 1.06-21.4, p < 0.031). None of the follow-up angiographic procedures displayed evidence of what could be interpreted as radiation damage. CONCLUSIONS: In this uncontrolled series, IVBT plus DCB appeared to lengthen the ISR-free interval relative to what had been achieved prior to the combined intervention. We view these results as mildly encouraging, worthy of further study.