Research Review: What are the Predictors of a Good Response to Percutaneous Coronary Intervention?
CLINICAL QUESTION: what is the role of nuclear myocardial perfusion imaging in predicting an increase in exercise capacity after 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 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%.
RESEARCH OBJECTIVE: Stress-rest myocardial perfusion scintigraphy has important prognostic ability to predict mortality, but can it also help predict just who will show the greatest benefit from PCI? Does MPS help forecast who will show an improved exercise capacity after PCI? In the UK, what is the prevalence of inducible ischemia in those patients who undergo a PCI procedure?
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 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.
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.
The patients then returned at 6 months for a follow-up evaluation. At this time, on average the patients showed an increase in exercise capacity and a decrease in physical limitations. The exercise capacity on average increased from 7 to 9 METS, which was statistically highly significant. However, the New York Heart Association functional class did not change in 62% of the patients, whereas it improved in 33%, and worsened in 5%.
Univariate and multivariate predictors of improvement were then assessed. The independent predictors of improvement identified were male gender, limiting chest pain on baseline exercise testing, and the degree of inducible hypoperfusion on nuclear myocardial perfusion imaging. These were all statistically significant on both univariate and multivariate analyses.
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.
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 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%.
RESEARCH OBJECTIVE: Stress-rest myocardial perfusion scintigraphy has important prognostic ability to predict mortality, but can it also help predict just who will show the greatest benefit from PCI? Does MPS help forecast who will show an improved exercise capacity after PCI? In the UK, what is the prevalence of inducible ischemia in those patients who undergo a PCI procedure?
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 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.
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.
The patients then returned at 6 months for a follow-up evaluation. At this time, on average the patients showed an increase in exercise capacity and a decrease in physical limitations. The exercise capacity on average increased from 7 to 9 METS, which was statistically highly significant. However, the New York Heart Association functional class did not change in 62% of the patients, whereas it improved in 33%, and worsened in 5%.
Univariate and multivariate predictors of improvement were then assessed. The independent predictors of improvement identified were male gender, limiting chest pain on baseline exercise testing, and the degree of inducible hypoperfusion on nuclear myocardial perfusion imaging. These were all statistically significant on both univariate and multivariate analyses.
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.