This summary includes details from the study . It was published in medRxiv.org in an early preprint. It was not peer-reviewed.
Key Takeaway
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In the first study to describe the magnitude of coronary microvascular collateral perfusion researchers found that 60 percent of perfusion to damaged myocardium is due to collaterals regardless of coronary occlusion or absence of angiographically visible collateral vessels.
Why This Matters
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Patients with CAD had better outcomes when collaterals were present. The extent of myocardial perfusion during experimental balloon occlusion is not established.
Study Design
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A retrospective study of a larger study showed that patients who did not have myocardial or bypass surgery, or angiographically visible collaterals underwent elective percutaneous Transluminal Coronay Angioplasty (PTCA) to one coronary vessel , between September 1995 – April 1996.
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After 3 minutes of balloon inflation in the intracoronary area 1100 MBq of 99mTc_sestamibi were injectable. The SPECT imaging of vessels was done within 3 hours (occlusion study). A second SPECT imaging test the day following PTCA with 1100 MBq of 99m Tc-sestamibi was performed (control study).
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The ratio of occlusion as well as the extent of perfusion between the study of occlusion and control were determined. Statistical analysis was done with the aid of software R and the differences between groups were assessed using the Wilcoxon test. A value of.05 was considered statistically significant.
Key Results
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PTCA was carried out on 21 patients, with a median balloon occlusion time of 5 minutes.
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The perfusion defect was measured at 16 percent of the left ventricle. The collateral perfusion was 64% of the normal perfusion for the entire cohort.
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Collateral perfusion was negatively correlated with perfusion defect size (R 2= 0.85; P < .001). Perfusion defects with smaller size had more collateral perfusion than larger defects, but were not different by age or sex.
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In spite of coronary occlusion, and the absence of collateral vessels that can be identified angiographically, collaterals provide 60% to the perfusion that is able to reach damaged myocardium.
Limitations
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Although the study only included 21 patients, it was adequate for a point estimation. It also offered enough variability to allow for myocardium that isn’t affected by an occluded artery.
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Uptake of 99mTc-sestamibi after balloon deflation could possibly falsely increase estimates of collateral perfusion. The time for balloon injection was 5 min. With the 8% of 99mTcestamibi remaining in the bloodstream after 5 minutes, perfusion results may have been exaggerated by 8%.
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Contralateral vessel imaging was not conducted in this study during balloon inflation. It is not known whether collateral vessels can be visualized angiographically during balloon obstruction.
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Analysis was done on images that weren’t attenuation corrected, which could underestimate the perfusion defect by 3%.
Disclosures
This is a synopsis of a research study entitled “Coronary collaterals that aren’t visible in invasive angiography could provide more than half of normal rested perfusion in patients suffering from coronary artery disease.” It was written by Brandon Harris, Ravinay Bhindi and Usaid Allahwala of the Kolling Institute, Royal North Shore Hospital and the University of Sydney. Stafford Warren, MD, of the Anne Arundel Medical Center in Annapolis, MD, also contributed. Eva Persson (MD, PhD) from the Department of Clinical Physiology at Skane University Hospital, Lund, Sweden, also contributed. Michael Ringborn, MD and PhD, of the Thoracic Center at Blekinge Country Hospital, Karlskrona (Sweden) Also contributed. Medscape has this study available from the medRxiv database.
