Risk Stratification of Patients With Chest Pain of Unknown Origin
Risk Stratification of Patients With Chest Pain of Unknown Origin
In patients with chest pain and suspected CAD, functional dual imaging-derived parameters such as inducible ischemia or reduced CFR on LAD and significant CAD at CTCA as well as vessel calcification provide strong and comparable prognostic information.
CTCA is a recognized modality for the non-invasive assessment of CAD, with a reported mean sensitivity and specificity >90%.
Calcium score adds prognostic value to that of traditional risk factors. Of note, it allows to reclassify intermediate risk asymptomatic subjects in more accurate risk categories. In this study we found a direct relationship between high calcium score and the presence of stress-induced ischemia or impaired CFR on LAD. Moreover, high calcium score was an independent predictor of future cardiac events.
Previous experiences on symptomatic unselected patient populations showed CTCA to be more accurate than calcium score to predict all-cause mortality. However, both obstructive and non-obstructive CAD at CTCA was associated with increased mortality in the Confirm study. In addition, in stable patients with suspected or known CAD, non-invasive fractional flow reserve computed from CT was associated with improved diagnostic accuracy and discrimination compared to CTCA alone for diagnosis of hemodynamically significant CAD.
In recent years, dipyridamole stress echocardiography with combined assessment of CFR in the LAD has entered the echocardiography lab as a highly feasible technique, providing additional diagnostic value over conventional wall motion analysis. In fact, dipyridamole stress echocardiography with combined assessment of CFR has also been extensively validated in its prognostic correlates and has allowed effective risk assessment in diabetics with negative stress echocardiographic results by wall motion criteria,, in subjects with intermediate LAD stenosis, and in those with normal or near-normal coronary arteries. Interestingly enough, the prognostic capability of CFR was not affected by ongoing anti-ischemic therapy.
CFR on LAD or inducible wall motion abnormalities would certainly improve the cost-benefit practice compared with indiscriminate "carpet bombing" with dilatation for all stenosis independent of the underlying clinical picture and physiologic substrate. The American Heart Association/American College of Cardiology/Society for Cardiovascular Angiography and Interventions on percutaneous coronary interventions guidelines and the American Heart Association scientific statement from the committee on diagnostic and interventional cardiac catheterization have indicated that in the presence of an intermediate lesions, when fractional flow reserve is < 0.75 or CFR is < 2.0, the stenosis is considered hemodynamically significant and percutaneous coronary intervention can be supported.
Accordingly, in this study we showed that CFR on LAD or stress-induced ischemia were independent predictors of events, and higher coronary calcification score was associated with lower values of CFR.
The clinical use of stress echo and CTCA should consider the cost, safety, effectiveness and feasibility issues that may vary in the various centers since - for instance - the radiation dose of CTCA may range from 1 to 30 mSv depending upon type of technology, operator skills, and clinical questions (calcium score vs coronary angiography). Stress echocardiography has several advantages, including the possibility of obtaining information on regional function and CFR in the same sitting, low cost, and radiation-free nature of the ultrasound technique. Yet, it is dependent upon the skill and experience of the reader and therefore not all centers have adequate expertise to guarantee high diagnostic standards.
For uniformity of the study population, we enrolled all patients with symptoms (patients with chest pain syndrome of unknown origin) without history of previous myocardial infarction or previous myocardial revascularization. This represents a group with intermediate pre-test likelihood of disease, where the indication for noninvasive testing is more appropriate.
In all patients, medical therapy was kept unchanged. This may have caused suboptimal echo studies with false negative results for wall motion analysis. However, the prognostic capability of CFR on LAD is not affected by ongoing therapy.
Discussion
In patients with chest pain and suspected CAD, functional dual imaging-derived parameters such as inducible ischemia or reduced CFR on LAD and significant CAD at CTCA as well as vessel calcification provide strong and comparable prognostic information.
Anatomic Evaluation of Coronary Stenosis: CTCA
CTCA is a recognized modality for the non-invasive assessment of CAD, with a reported mean sensitivity and specificity >90%.
Calcium score adds prognostic value to that of traditional risk factors. Of note, it allows to reclassify intermediate risk asymptomatic subjects in more accurate risk categories. In this study we found a direct relationship between high calcium score and the presence of stress-induced ischemia or impaired CFR on LAD. Moreover, high calcium score was an independent predictor of future cardiac events.
Previous experiences on symptomatic unselected patient populations showed CTCA to be more accurate than calcium score to predict all-cause mortality. However, both obstructive and non-obstructive CAD at CTCA was associated with increased mortality in the Confirm study. In addition, in stable patients with suspected or known CAD, non-invasive fractional flow reserve computed from CT was associated with improved diagnostic accuracy and discrimination compared to CTCA alone for diagnosis of hemodynamically significant CAD.
Functional Evaluation of Coronary Stenosis: Stress Echocardiography
In recent years, dipyridamole stress echocardiography with combined assessment of CFR in the LAD has entered the echocardiography lab as a highly feasible technique, providing additional diagnostic value over conventional wall motion analysis. In fact, dipyridamole stress echocardiography with combined assessment of CFR has also been extensively validated in its prognostic correlates and has allowed effective risk assessment in diabetics with negative stress echocardiographic results by wall motion criteria,, in subjects with intermediate LAD stenosis, and in those with normal or near-normal coronary arteries. Interestingly enough, the prognostic capability of CFR was not affected by ongoing anti-ischemic therapy.
CFR on LAD or inducible wall motion abnormalities would certainly improve the cost-benefit practice compared with indiscriminate "carpet bombing" with dilatation for all stenosis independent of the underlying clinical picture and physiologic substrate. The American Heart Association/American College of Cardiology/Society for Cardiovascular Angiography and Interventions on percutaneous coronary interventions guidelines and the American Heart Association scientific statement from the committee on diagnostic and interventional cardiac catheterization have indicated that in the presence of an intermediate lesions, when fractional flow reserve is < 0.75 or CFR is < 2.0, the stenosis is considered hemodynamically significant and percutaneous coronary intervention can be supported.
Accordingly, in this study we showed that CFR on LAD or stress-induced ischemia were independent predictors of events, and higher coronary calcification score was associated with lower values of CFR.
Clinical use of the Techniques
The clinical use of stress echo and CTCA should consider the cost, safety, effectiveness and feasibility issues that may vary in the various centers since - for instance - the radiation dose of CTCA may range from 1 to 30 mSv depending upon type of technology, operator skills, and clinical questions (calcium score vs coronary angiography). Stress echocardiography has several advantages, including the possibility of obtaining information on regional function and CFR in the same sitting, low cost, and radiation-free nature of the ultrasound technique. Yet, it is dependent upon the skill and experience of the reader and therefore not all centers have adequate expertise to guarantee high diagnostic standards.
Study Limitations
For uniformity of the study population, we enrolled all patients with symptoms (patients with chest pain syndrome of unknown origin) without history of previous myocardial infarction or previous myocardial revascularization. This represents a group with intermediate pre-test likelihood of disease, where the indication for noninvasive testing is more appropriate.
In all patients, medical therapy was kept unchanged. This may have caused suboptimal echo studies with false negative results for wall motion analysis. However, the prognostic capability of CFR on LAD is not affected by ongoing therapy.