About Non-obstructive General Angioscopy (NOGA)

Is Angioscopy Dangerous? No! NOGA demonstrates New World!

Angioscopy, a type of endoscopy, is a procedure used to explore vessels. When angioscopy is used to observe the inside of blood vessels, the visual field appears as a solid red. In older times, prototype angioscopy has been used for coronary arteries in the United States. At that time, an occlusion-type angioscopy was used. It was potentially dangerous for coronary arteries because the coronary arteries were occluded during an observation by angioscopy. In Japan, non-obstructing -type angioscopy (NOA) has been developed. The primary approach in NOA involved visualizing the field by injecting low-molecular-weighed dextran into the area between the 4-Fr probing catheter and the fiber. This diluted the blood and expanded the field of view.

NOA clarified the mechanisms of coronary plaque rupture [1], distribution [2], stabilization by drugs [3], and neointimal coverage and restenosis of stents. [4] We further developed a dual infusion method to widen the visual field, utilizing infusions from probing and 6-Fr guiding catheters. [5] Using the method, angioscopy has become easy, and the application has expanded to any type of vessel, such as the aorta. [6] We named the system a non-obstructing -type general angioscopy (NOGA)

Generally, the plaques and injuries of the aorta are evaluated by computed tomography, magnetic resonance, and transesophageal echocardiography. However, the world observed through NOGA was entirely different from what had been seen with previous imaging modalities or pathology. [7] The traditional modalities show still images and have poorer spatial and temporal resolution compared to NOGA. NOGA demonstrated vivid images of spontaneously ruptured aortic plaques (SRAPs). SRAPs were also found in 80.9 % of patients with or suspected coronary artery disease.

In the debris from scattered plaques such as puff-chandelier plaques, which reflected against the light of the angioscopic fiber and scattered like puff, cholesterol crystals (CCs) were found. However, empty clefts in samples with Hematoxylin-eosin stain were treated as CCs. There are lots of kinds of crystals in our body. We successfully demonstrated CCs as real imaging by soft preparations with polarized light microscopy. [7] CCs are spotlighted in the field of innate inflammation during atherosclerosis and plaque rupture. We demonstrated CCs were recognized and engulfed by macrophages, NLRP3 inflammasome was activated, and the inflammatory cytokines were provoked. [8]

The asymptomatic embolization of aortic debris, including CCs, may be related to acute and chronic organ damage such as stroke, dementia, frail, and sarcopenia. [9] In ischemic stroke, SRAPs are distributed in the proximal aorta, such as the aortic arch [10], and SRAPs may cause stroke more than thought because CCs are detected from “thrombectomy” samples. [11]

NOGA applications have been expanded to guide stent graft implantation. Good results were reported covering the fissures detected by NOGA. [12] Moreover, NOGA is also applied to evaluate the intervention for structured heart disease. We believe aortic dissection will be overcome by the observation with NOGA! The new world will come with the upcoming new type of angioscopy!


  1. Kodama K, Asakura M, Ueda Y, Yamaguchi O, Hirayama A. The role of plaque rupture in the development of acute coronary syndrome evaluated by the coronary angioscope. Intern Med. 2000 Apr;39(4):333-5.
  2. Asakura M, Ueda Y, Yamaguchi O, Adachi T, Hirayama A, Hori M, Kodama K. Extensive development of vulnerable plaques as a pan-coronary process in patients with myocardial infarction: an angioscopic study. J Am Coll Cardiol. 2001 Apr;37(5):1284-8.
    3.Hirayama A, Saito S, Ueda Y, Takayama T, Honye J, Komatsu S, Yamaguchi O, Li Y, Yajima J, Nanto S, Takazawa K, Kodama K. Plaque-stabilizing effect of atorvastatin is stronger for plaques evaluated as more unstable by angioscopy and intravenous ultrasound. Circ J. 2011;75(6):1448-54.
  3. Ueda Y, Nanto S, Komamura K, Kodama K. Neointimal coverage of stents in human coronary arteries observed by angioscopy. J Am Coll Cardiol. 1994 Feb;23(2):341-6.
  4. Komatsu S, Ohara T, Takahashi S, Takewa M, Yutani C, Kodama K. Improving the visual field in coronary artery by with non-obstructive angioscopy: dual infusion method. Int J Cardiovasc Imaging. 2017 Jun;33(6):789-796.
  5. Komatsu S, Ohara T, Takahashi S, Takewa M, Minamiguchi H, Imai A, Kobayashi Y, Iwa N, Yutani C, Hirayama A, Kodama K. Early detection of vulnerable atherosclerotic plaque for risk reduction of acute aortic rupture and thromboemboli and atheroemboli using non-obstructive angioscopy. Circ J. 2015;79(4):742-50.
  6. Komatsu S, Yutani C, Ohara T, Takahashi S, Takewa M, Hirayama A, Kodama K. Angioscopic Evaluation of Spontaneously Ruptured Aortic Plaques. J Am Coll Cardiol. 2018 Jun 26;71(25):2893-2902.
  7. Iwa N, Yutani C, Komatsu S, Takahashi S, Takewa M, Ohara T, Kodama K. Novel Methods for Detecting Human Cholesterol Crystals from Sampled Blood. Lab Med. 2022 May 5;53(3):255-261. 
  8. Komatsu S, Yutani C, Takahashi S, Takewa M, Iwa N, Ohara T, Kodama K. Cholesterol Crystals as the Main Trigger of Interleukin-6 Production through Innate Inflammatory Response in Human Spontaneously Ruptured Aortic Plaques. J Atheroscler Thromb. 2023 Nov 1;30(11):1715-1726. 
  9. Komatsu S, Takahashi S, Yutani C, Ohara T, Takewa M, Hirayama A, Kodama K. Spontaneous ruptured aortic plaque and injuries: insights for aging and acute aortic syndrome from non-obstructive general angioscopy. J Cardiol. 2020 Apr;75(4):344-351. 
  10. Higuchi Y, Hirayama A, Komatsu S, Kodama K. Embolic Stroke Caused by Aortic Ruptured Plaque and Thrombus Visualized by Angioscopy. JACC Case Rep. 2020 Apr 8;2(5):705-706.
  11. Shiba M, Fukutome K, Higuchi Y. Involvement of cholesterol crystals in the mechanism of aortogenic cerebral infarction: an angioscopic study. Eur Heart J. 2024 May 13;45(18):1686. 
  12. Nishi H, Higuchi Y, Takahashi T, Domae K, Inoguchi K, Kawasumi R, Hamanaka Y, Komatsu S, Hirayama A, Kodama K. Aortic angioscopy assisted thoracic endovascular repair for chronic type B aortic dissection. J Cardiol. 2020 Jul;76(1):60-65. 


If you want to see videos of SRAPs by angioscopy, refer to

Video 1 of Different Characteristics and Interleukin-6 Ratios of Scattering-Type Aortic Plaques – PMC (nih.gov)

Supplementary material of Serial Observation of Aortic Puff-Chandelier Rupture for 2 Years by Non-Obstructive General Angioscopy (jst.go.jp)

Videos of aortic injuries, refer videos in

Demonstration of entry tear and disrupted intima in asymptomatic chronic thrombosed type B dissection with non-obstructive angioscopy | BMJ Case Reports

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