Coronary Collaterals Provide Significant Perfusion in CAD

Abdullah Hashmi, MD

January 17, 2022

The study covered in this summary was published in medRxiv.org as a preprint and has not yet been peer-reviewed.

Key Takeaway

  • In the first study to describe the magnitude of coronary microvascular collateral perfusion, researchers found 60% of perfusion to jeopardized myocardium is provided by collaterals, despite coronary occlusion and an absence of angiographically visible collateral vessels.

Why This Matters

  • The presence of collaterals was shown to be associated with improved outcomes in patients with CAD. However, the magnitude of myocardial perfusion provided by collateral circulation during experimental balloon occlusion is described for the first time. 

Study Design

  • In a retrospective substudy of a larger cohort, patients without a history of prior myocardial infarction, bypass surgery, or angiographically visible collaterals underwent elective percutaneous transluminal coronary angioplasty (PTCA) to a single coronary vessel between September 1995 and April 1996.

  • 1100 MBq of  99mTc-sestamibi was injected after 3 minutes of full intracoronary balloon inflation, and SPECT imaging of vessels occurred within 3 hours of injection (occlusion study). A second SPECT imaging study the day after PTCA with 1100 MBq of  99mTc-sestamibi was done (control study). 

  • The ratio of occlusion and extent of perfusion between the occlusion and control studies were calculated. Statistical analysis was done using software R, and between-group differences were tested using the Wilcoxon test. A P value < .05 was considered statistically significant.

Key Results

  • PTCA was performed in 21 patients with a mean balloon occlusion time of 5 minutes.

  • The size of perfusion defect was 16% of the left ventricle, and the collateral perfusion within the perfusion defect was 64% of normal perfusion within that region for the entire cohort.

  • Collateral perfusion was negatively correlated with perfusion defect size (R2 = 0.85; P < .001). Smaller perfusion defects had greater collateral perfusion than larger perfusion defects but did not differ by age or sex.

  • On average, despite coronary occlusion and an absence of angiographically visible collateral vessels, collaterals provide 60% of the perfusion that reaches the jeopardized myocardium.

Limitations

  • The study only included 21 patients but was considered adequate for a point estimate and provided enough variability for myocardium subtended by an occluded coronary artery.

  • Uptake of 99mTc-sestamibi following balloon deflation could potentially falsely increase estimates of collateral perfusion. Given that mean balloon injection time was 5 minutes, and 8% of 99mTc-sestamibi remains in the bloodstream after 5 minutes, measured perfusion results could have been overestimated by 8%. 

  • Contralateral vessel angiography was not performed during balloon angioplasty inflation in this study. It is not known if collateral vessels could be angiographically visualized during balloon occlusion.

  • Analysis was done on images that were not attenuation corrected, which could overestimate the perfusion defect by 3%. 

Disclosures

  • The authors declared no competing interests.

  • No external funding was received.

This is a summary of a preprint research study, "Coronary collaterals not visible by invasive angiography can provide more than half of normal resting perfusion in patients with coronary artery disease," written by Brandon Harris, Ravinay Bhindi, MBBS, PhD, Martin Ugander, MD, PhD, and Usaid Allahwala, MBBS, PhD, of the Kolling Institute at Royal North Shore Hospital and University of Sydney, Australia. Stafford Warren, MD, of the Anne Arundel Medical Center in Annapolis, MD, also contributed. Eva Persson, MD, PhD, from the Department of Clinical Physiology and Skane University Hospital in Lund, Sweden also contributed. Michael Ringborn, MD, PhD, of the Thoracic Center of Blekinge Country Hospital in Karlskrona, Sweden also contributed. This study from medRxiv is provided to you by Medscape.

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