A Benign Course of Sinus Node Artery Occlusion After Stenting at Proximal Right Coronary Artery
Sinus node artery (SNA) occlusion during percutaneous coronary intervention (PCI) for proximal right coronary artery (RCA) lesions can lead to transient bradycardia and arrhythmias, though recent advancements in stent technology and antithrombotic therapies have reduced the incidence of such complications. This study investigates the incidence, predictors, and clinical outcomes of SNA occlusion (SNO) in a large cohort of patients undergoing PCI for severe proximal RCA stenosis. The findings demonstrate that SNO, while not uncommon, follows a benign clinical course with minimal need for temporary or permanent pacemaker implantation.
The SNA, which typically originates from the RCA, supplies blood to the sinus node and plays a critical role in maintaining normal cardiac rhythm. Occlusion of the SNA during PCI can result in sinus arrest, junctional escape rhythms, or other supraventricular arrhythmias. Early studies reported a 20% incidence of SNO, but improvements in stent design, such as thinner struts and reduced stent profiles, along with optimized antithrombotic regimens, have led to lower rates of side branch compromise in contemporary practice. This study provides a systematic analysis of SNO in a Chinese population, emphasizing its predictors and clinical implications.
Between January 2015 and December 2019, 460 patients with severe proximal RCA stenosis (≥90% diameter stenosis) and SNA originating from the RCA were enrolled. The cohort was divided into an occlusion group (TIMI flow grade 0–1 in the SNA post-PCI) and a control group (TIMI flow grade 2–3). Coronary angiography and quantitative measurements, including luminal diameters, stenosis percentages, and bifurcation angles, were analyzed using automated edge-detection software. Clinical variables, procedural details, and outcomes were compared between groups.
The overall incidence of SNO was 7.0% (32/460 patients). Univariable analysis revealed that patients in the occlusion group had higher rates of smoking (100% vs. 47.2%, P < 0.001) and lower left ventricular ejection fractions (57.9% ± 4.1% vs. 59.8% ± 8.9%, P = 0.04). Angiographic predictors of SNO included severe stenosis at the SNA ostium, SNA origination from a diseased segment of the RCA, and a larger RCA/SNA diameter ratio. Multivariable logistic regression confirmed these factors as independent predictors: initial percentage diameter stenosis of the SNA (OR: 1.12, 95% CI: 1.06–1.18), SNA originating at a diseased RCA (OR: 4.02, 95% CI: 1.64–9.88), and RCA/SNA diameter ratio (OR: 1.45, 95% CI: 1.14–1.84). Stent coverage over the SNA ostium and larger bifurcation angles were also associated with SNO in unadjusted analyses.
Procedurally, SNO led to new-onset bradycardia in 12.5% of cases (4/32 patients), though only one patient required temporary pacemaker implantation. In three cases, bradycardia resolved with atropine administration. The fourth patient experienced sinus bradycardia (45 beats/min) and hypotension (85/50 mmHg) refractory to initial treatment. Guidewire and balloon interventions, combined with tirofiban infusion, partially restored SNA flow (TIMI grade 2), but transient cardiac arrest (>5 seconds) necessitated temporary pacing. Sinus rhythm recovered fully within nine days, and follow-up angiography confirmed TIMI grade 3 flow in the SNA. No permanent pacemakers were implanted, and there were no differences in perioperative cardiac biomarkers or heart rates between groups.
The relatively low incidence of SNO (7.0%) compared to historical data reflects advancements in PCI techniques. Thin-strut stents minimize strut obstruction at side branch ostia, while potent antiplatelet therapies (e.g., ticagrelor, glycoprotein IIb/IIIa inhibitors) mitigate thrombotic occlusion. The study also highlights anatomical and procedural factors influencing SNO risk. Severe stenosis at the SNA ostium indicates a significant plaque burden, predisposing to occlusion from plaque shift during stent deployment. Similarly, a larger RCA/SNA diameter ratio increases the likelihood of carina displacement or stent strut obstruction. The origin of the SNA from a diseased RCA segment further exacerbates risk, as true bifurcation lesions are more susceptible to snowplow effects during stenting.
Despite these risks, the clinical course of SNO was benign in this cohort. Transient bradycardia resolved spontaneously or with minimal intervention, and no permanent pacemakers were required. This aligns with prior studies suggesting the sinus node’s resilience to ischemia, likely due to collateral circulation from atrial arterial anastomoses. Additionally, spontaneous reperfusion may occur through plaque remodeling, vasospasm resolution, or microthrombus lysis, further limiting long-term consequences.
The study’s limitations include its retrospective design, potential selection bias, and lack of follow-up angiography to confirm SNA patency. Heterogeneity in stent types precluded analysis of device-specific risks. Nevertheless, the findings underscore that SNO, though not rare, rarely necessitates aggressive management. Temporary pacing suffices in cases of prolonged bradycardia, and permanent pacemaker implantation should be deferred unless spontaneous rhythm recovery is absent over extended periods.
In conclusion, this study provides critical insights into the predictors and outcomes of SNA occlusion during PCI for proximal RCA lesions. While anatomical and procedural factors influence SNO risk, the clinical course remains overwhelmingly benign, with transient bradycardia managed conservatively. These results reinforce the safety of modern PCI strategies and advocate against premature permanent pacemaker implantation in SNO cases.
DOI: 10.1097/CM9.0000000000001440
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