Review: What Predicts a Functional Response to Percutaneous Coronary Intervention?

By: Pasquale Jacobs

HYPOTHESIS: stress-rest Tc-99m tetrofosmin myocardial perfusion imaging can provide useful information in regards to who will benefit from coronary revascularization using percutaneous coronary intervention (PCI).
BACKGROUND: The Courage Trial found that there was no survival benefit to percutaneous coronary intervention over optimum medical therapy alone. However, in some patient subgroups, PCI was shown to have important quality of life benefits. Thus, there continues to remain uncertainty over who should undergo PCI. It is important to note that PCI is not without risks. PCI in the past has been shown to have a risk of morbidity of about 0.25% and risk of mortality of about 0.20%.
OBJECTIVE: Can myocardial perfusion scintigraphy (MPS) be of benefit in the prediction of an increased in exercise capacity after PCI? Can it help predict who will have decreased symptoms after PCI? And finally, in the United Kingdom what is the prevalence of inducible ischemia on MPS in patients undergoing PCI?
PATIENTS: Patients were mostly male (86%) and most (63%) but not all (37%) had stable angina. Patients were recruited prospectively from the a group of patients that had a positive diagnostic angiogram and were already scheduled to undergo an elective PCI procedure.
METHODS: Within a month prior to undergoing PCI, the research subjects underwent a same day, single isotope stress-rest MPS using Tc-99m tetrofosmin. Patients underwent treadmill exercise stress testing rather than pharmacologic stress testing whenever possible. Patients were assess clinically for their New York Heart Association functional status, and symptoms assessed using the Seattle Angina Questionnaire. The doctors doing the PCI procedure were blinded as to the results of the myocardial perfusion scan. All PCI procedures went ahead as originally planned.
Then, at about 6 months after the PCI procedure, the patients returned for a follow-up evaluation. Functional status and clinical symptoms were determined. Those that had undergone treadmill stress testing at baseline underwent a repeat treadmill stress test using the same protocol, which was done at the same time of day. The clinical staff performing the treadmill ECG test were blinded as to the results of the patient's baseline treadmill test.
Myocardial perfusion results were evaluated quantitatively using standard cardiac software programs. Visual analysis was performed by two readers, who looked at each scan and assigned a semiquantitative summed stress and summed rest score. A 17 segment 5-point scale was used for summed scoring.
RESULTS: There were 123 patients included in the study population. The treadmill exercise stress test was positive for evidence of inducible myocardial ischemia in 72%. The myocardial perfusion scan showed inducible hypoperfusion affecting greater than 10% of the myocardium in 20% of patients. The perfusion scan showed inducible hypoperfusion of 1% to 10% of the myocardium in 54% of the patients. The remaining 26% of patients had no reversible defects on perfusion scintigraphy.
Six months later at the follow-up evaluation, improvement was seen in the Seattle Angina Questionnaire and in exercise capacity. Looking at the entire patient population, the Seattle Angina Questionnaire physical limitation score improved from 66 to 75, which was highly statistically significant. Exercise capacity also showed a highly significant improvement, with the average exercise tolerance increasing from 7 to 9 METS. The New York Heart Association functional class, however, was unchanged in 62%, improved in 33%, and worse in 5%.
The multivariate independent predictors of improvement were male gender, limiting chest pain on baseline treadmill stress testing, and the summed defect score.
CONCLUSION: Of all patients undergoing elective PCI in this study, only a small minority had a reversible myocardial perfusion defect affecting 10% or more of the myocardium. Independent predictors of improvement after revascularization were male sex, limiting chest pain on exercise stress testing, and inducible hypoperfusion on myocardial perfusion scintigraphy.
SOURCE ARTICLE: J Nucl Cardiol. 2009 Jul 9. [Epub ahead of print]. Does myocardial perfusion scintigraphy predict improvement in symptoms and exercise capacity following successful elective percutaneous coronary intervention? Al-Housni MB, Hutchings F, Dalby M, Dubowitz M, Grocott-Mason R, Ilsley CD, Mason M, Mitchell AG, Kelion AD. Department of Cardiology, Royal Brompton and Harefield NHS Foundation Trust, Harefield Hospital, Harefield, Middlesex, United Kingdom. Medline Abstract.

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