Correspondence

Collateral Blood Flow and Myocardial Viability

N Engl J Med 1993; 328:1570May 27, 1993

Article

To the Editor:

Sabia et al. (Dec. 24 issue)1 used myocardial contrast echocardiography to assess collateral flow, on the basis of experimental validation studies. The accuracy of this method in determining collateral flow in humans with chronic coronary occlusion has, to my knowledge, never been demonstrated. Nevertheless, total occlusion of a coronary artery is a “stable” coronary condition that would have allowed a comparison of the distribution of the microbubbles in collateral-dependent areas with the results of other techniques for the assessment of myocardial flow, such as perfusion scintigraphy.

The choice of angiographic grading of collateral vessels is unclear and not in accordance with the classification described by Rentrop et al.,2 which is used by many other investigators. Thus, comparison with other recent studies is difficult. More important, several reports have clearly demonstrated marked differences in the angiographic appearance of collateral vessels within 10 to 14 days after persistent coronary occlusion in acute myocardial infarction3-5.

Sabia et al. performed coronary angiography a mean (±SEM) of 12 ±2 days after myocardial infarction. Therefore, it seems likely that most of the collateral vessels developed within the time between myocardial infarction and cardiac catheterization. The most relevant information regarding the functional role of collateral vessels will be provided by studies that are performed during the acute phase of myocardial infarction.

Did the observed improvement in wall motion after angioplasty relate to the size of the myocardial infarct (assessed enzymatically), expressed as a percentage of the size of the myocardial perfusion bed determined by myocardial contrast echocardiography? A reduction in the size of the infarct in this category of patients is most likely related to increased collateral flow during the acute event. This would support the presumed association between collateral blood flow and myocardial viability.

Jan J. Piek, M.D.
Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, the Netherlands

5 References

1. 1

   Sabia PJ, Powers ER, Ragosta M, Sarembock IJ, Burwell LR, Kaul S. An association between collateral blood flow and myocardial viability in patients with recent myocardial infarction. N Engl J Med 1992;327:1825-1831
   Full Text | Web of Science | Medline

2. 2

   Rentrop KP, Cohen M, Blanke H, Phillips RA. Changes in collateral channel filling immediately after controlled coronary artery occlusion by an angioplasty balloon in human subjects. J Am Coll Cardiol 1985;5:587-592
   CrossRef | Web of Science | Medline

3. 3

   Schwartz H, Leiboff RH, Bren GB, et al. Temporal evolution of the human coronary collateral circulation after myocardial infarction. J Am Coll Cardiol 1984;4:1088-1093
   CrossRef | Web of Science | Medline

4. 4

   Nitzberg WD, Nath HP, Rogers WJ, et al. Collateral flow in patients with acute myocardial infarction. Am J Cardiol 1985;56:729-736
   CrossRef | Web of Science | Medline

5. 5

   Rentrop KP, Feit F, Sherman W, Thornton JC. Serial angiographic assessment of coronary artery obstruction and collateral flow in acute myocardial infarction: report from the Second Mount Sinai-New York University Reperfusion Trial. Circulation 1989;80:1166-1175
   CrossRef | Web of Science | Medline

Author/Editor Response

The authors reply:

To the Editor: Some of the concerns raised by Dr. Piek were addressed in an earlier study,1 in which we showed that patients with greater collateral flow on myocardial contrast echocardiography had smaller infarcts (as estimated from creatine kinase levels) although they had the same size perfusion bed. These patients were also studied approximately two weeks after their infarction and had totally occluded infarct-related arteries. Therefore, although collateral development can also occur after infarction, it is more likely that most of it had already occurred in our patients before coronary occlusion.

When we also studied these patients with quantitative planar thallium-201 imaging, the findings about myocardial viability were similar,2 although the prediction of improvement in function was made more definitely with myocardial contrast echocardiography than with thallium-201 imaging. This is probably related to the better spatial resolution of the former technique. Thus, validation of our method in humans by means of other techniques, such as scintigraphy, has been performed though not formally presented.

With regard to the method of angiographic collateral grading, the results were unchanged when other grading systems were used. Myocardial contrast echocardiography may be superior to angiography for defining collaterals since it can show microvascular perfusion, whereas angiography identifies only larger vessels. We also found a poor correlation between thallium-201 uptake and angiographic collateral grade in patients with occluded vessels and a recent infarction1.

Peter J. Sabia, M.D.
Eric R. Powers, M.D.
Sanjiv Kaul, M.D.
University of Virginia School of Medicine, Charlottesville, VA 22908

2 References

1. 1

   Sabia PJ, Powers ER, Jayaweera AR, Ragosta M, Kaul S. Functional significance of collateral blood flow in patients with recent acute myocardial infarction: a study using myocardial contrast echocardiography. Circulation 1992;85:2080-2089
   Web of Science | Medline

2. 2

   Sabia PJ, Powers ER, Ragosta M, Watson DD, Smith WH, Kaul S. Role of quantitative planar thallium-201 imaging for predicting viability in patients with acute myocardial infarction and a totally occluded infarct-related artery. J Nucl Med (in press).
   

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