Review: Predictors of a Positive Response to Coronary Revascularization
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 PCI. In patients with stable chest pain, PCI hasn’t been shown to confer a prognostic advantage as compared to modern medical management. 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%.
STUDY OBJECTIVE: Is stress-rest myocardial perfusion scintigraphy (MPS) beneficial in predicting who will show an increased exercise capacity after PCI? Can MPS testing help predict which patient groups will have the greatest decrease in symptoms after 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: Research patients all underwent a stress-rest myocardial perfusion scan using a single-day, single-isotope protocol utilizing Tc-99m tetrofosmin. The nuclear scan was done within a month prior to the PCI procedure. As much as possible, treadmill stress testing rather than pharmacologic stress testing was performed. Their New York Heart Association functional status was assessed. Patients also filled out the Seattle Angina Questionnaire. All of the physicians doing the PCI procedures where unaware of the results of the stress-rest myocardial 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.
Scan images were evaluated quantitatively using the Cedars-Sinai AutoSPECT and AutoQuant programs. Semiquantitative analysis was performed using summed scoring with a 17 segment 5-point scale. There were two readers who looked at each patient study. The mean of the semiquantitative summed scores assigned by these two readers were used for statistical analysis.
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.
At the 6 month follow-up visit, overall the average Seattle Angina Questionnaire score for all patients improved from 66 to 75 (P value less than 0.0001). The mean exercise capacity across all patients also improved, going from 7 up to 9 METS on average (P value less than 0.0001). However, the New York Heart Association functional class remained unchanged in 62%, it improved in 33%, and worsened 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: 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.
ARTICLE: 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.J Nucl Cardiol. 2009 Jul 9. [Epub ahead of print]. From the Department of Cardiology, Royal Brompton and Harefield NHS Foundation Trust, Harefield Hospital, Harefield, Middlesex, United Kingdom. Pubmed.