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 a lack of survival benefit to percutaneous coronary intervention as compared to optimum medical therapy alone. However, in some patient subgroups, PCI was shown to have important quality of life benefits. Thus, there remains ambiguity 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%.
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: The study group consisted of consecutive patients that were scheduled for an elective PCI after originally undergoing diagnostic coronary angiography. On average, patients were male (86%), age 65 years-old, and with stable angina (63%). Twenty-six percent of the patients had diabetes.
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.
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.
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: A total of 123 patients were included in the study. Exercise ECG tests were positive for inducible ischemia in 7 out of 10 patients. A reversible perfusion defect affecting greater than 10% of the myocardium was present in only 1 out of 5 patients. About half of the patients had reversible perfusion defects that affected less than 10% of the myocardium, and a quarter of the patients did not have any reversible perfusion defects.
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 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: The authors conclude that most of the patients undergoing elective PCI in a UK medical center had inducible ischemia on myocardial perfusion scintigraphy MPS of less than 10%. The patients that got the greatest benefit from revascularization were men with limiting chest pain with exertion and inducible ischemia on perfusion scintigraphy.
CITATION: Al-Housni MB, Hutchings F, Dalby M, Dubowitz M, Grocott-Mason R, Ilsley CD, Mason M, Mitchell AG, Kelion AD. Does myocardial perfusion scintigraphy predict improvement in symptoms and exercise capacity following successful elective percutaneous coronary intervention? J Nucl Cardiol. 2009 Jul 9. [Epub ahead of print]. Department of Cardiology, Royal Brompton and Harefield NHS Foundation Trust, Harefield Hospital, Harefield, Middlesex, United Kingdom. Pubmed Citation and Abstract.
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