Review: What are the Predictors of a Positive Benefit From Coronary Revascularization?
By Pasquale Jacobs | July 28, 2009
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CLINICAL QUESTION: what is the role of nuclear myocardial perfusion imaging in predicting an increase in exercise capacity after percutaneous coronary intervention (PCI)?
BACKGROUND: There frequently is doubt over which patients should undergo percutaneous coronary intervention. In patients with stable angina, PCI hasn’t been shown to confer a prognostic benefit as compared to modern medical therapy. PCI is associated with a risk of morbidity of around 0.25%. The risk of mortality after PCI has been shown in the past to be 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: The patient population studied was selected from consecutive patients that were previously scheduled for an elective PCI after having a positive diagnostic angiogram. On average, the patients were 65 years-old, with the majority being male (86%) with stable angina (63%). About 25% of the patients also had diabetes mellitus.
METHODS: Within one month before having their PCI procedure, patients in the study underwent stress-rest myocardial perfusion scintigraphy using a same day, single-isotope protocol using Tc-99m tetrofosmin. Treadmill exercise was utilized for the stress test as much as possible. The patient’s New York Heart Association functional status was assessed, and all patients answered the Seattle Angina Questionnaire. The cardiologists that performed the PCI procedures were blinded as to the outcome of the stress-rest perfusion scan. None of the PCI procedures were canceled due to the results of the perfusion scan.
At the 6 month follow-up visit after their PCI procedure, patients were once again evaluated for symptoms and functional status. A repeat treadmill test using the same protocol was performed in those patients that underwent treadmill stress ECG testing at baseline. Clinicians who performed this follow-up stress test were unaware of the results of the baseline 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 predictors of clinical and functional improvement were also evaluated. A multivariate analysis found that independent, statistically significant predictors of improvement were male gender, limiting chest pain on stress testing, and inducible hypoperfusion on myocardial perfusion imaging.
CONCLUSION: Only 20% of patients undergoing percutaneous coronary intervention had inducible myocardial ischemia of 10% or greater. The combination of limiting chest pain with treadmill stress testing and significant reversible perfusion defects on perfusion scintigraphy help predict a large gain in improvement after revascularization.
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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