Prognosis in patients achieving ≥10 METS on exercise stress testing: Was SPECT imaging useful?

Abstract

Background The benefit of myocardial perfusion imaging (MPI) over exercise ECG stress testing alone is unclear in individuals attaining a workload of ≥10 METS. The purpose of this prospective study is to determine mortality and nonfatal cardiac events in patients at either intermediate pretest risk for CAD or patients with known CAD, achieving ≥10 METS regardless of peak exercise heart rate. The authors previously reported a low prevalence of significant ischemia in this patient cohort. Methods Baseline characteristics, ECG stress test findings, and perfusion and function results from quantitative gated 99mTc-SPECT MPI were compared by achievement of a maximum age-predicted heart rate ≥85% in 509 consecutive patients who reached ≥10 METS. Events including all-cause and cardiac mortality, non-fatal myocardial infarction (MI), and late revascularization (>4 weeks after MPI) were prospectively collected. Results Of the 509 patients achieving ≥10 METS, follow-up for mortality was obtained in 463 (91%). Those lost to follow-up were older and had higher rates of tobacco use. The prevalences of CAD risk factors, prior known CAD, and MPI abnormalities were higher for the 68 patients failing to reach 85% of their target heart rate. The rate of ≥10% left-ventricular (LV) ischemia by MPI remained very low irrespective of attained heart rate (0.6% (3/463)). Six (1.2%) had an LVEF < 40%. Death occurred in 12 (2.6%) patients, one of which was classified as cardiac (0.1%/year). The other 11 deaths were related to cancer. Additionally, there were three nonfatal MIs (0.7 %) and one late revascularization (0.2%). Only one of these patients had any ischemia on MPI. No cardiac event patient had exercise ST depression or ≥5% LV ischemia. Conclusions Thus, patients at intermediate risk for CAD or known CAD achieving ≥10 METS have a very low prevalence of ≥10% LV ischemia and very low rates of cardiac mortality, nonfatal MI, and late revascularization, irrespective of heart rate achieved. Cardiac events did not correlate with abnormalities on the index MPI study. These results suggest that patients who attain ≥10 METS during exercise stress have an excellent prognosis over an intermediate term of follow-up, regardless of peak exercise heart rate achieved. The added value of MPI to standard exercise ECG testing in this population is questionable.

Seguimiento clínico en pacientes con buena capacidad metabólica en la prueba de esfuerzo con SPECT miocárdico

“…De ellos, casi la mitad eran sintomáticos al momento del estudio; 5 de los 7 pacientes con eventos tuvieron isquemia en SPECT, significativa sólo en 2. La ausencia de mortalidad de origen cardiovascular y la baja tasa de IM agudo (2%) dentro del año posterior a la realización del SPECT en pacientes con alto rendimiento aeróbico fue concordante con la literatura 12,16,17,27 . Otro estudio reciente le asigna valor predictivo en la PE a la tasa del doble producto 28 Eventos coronarios en pacientes con 10 METs en SPECT con ejercicio -J. González et al valor pronóstico a esta variable, explicable por la selección de la muestra.…”

“…En trabajos que dividen la población según METs alcanzados y frecuencia cardiaca máxima teórica (FCMT), el porcentaje de eventos a corto o largo plazo en pacientes con alta capacidad metabólica sería mínimo y no afectaría la sobrevida 16,17 . Con la implementación de los criterios apropiados para imágenes cardiacas se intenta acotar costos, aumentar seguridad y disminuir radiación, seleccionando mejor la población con mayor riesgo de EC [18][19][20] .…”

The mystery poor prognosticator! Pharmacologic stress MPI prevalence and predictors: Insights from the Middle East

“…They indicated that simple ETT in this group of patients is comparable to MPI in terms of diagnostic accuracy and prognostic power. 5 There is no doubt that the pattern of patient referral to pharmacologic or physical stress varies from one center to another and is related to multiple factors. From our point of view, the cost (economic factor) and the availability of pharmacologic stressors, along with a patient's cultural background and comorbidities are the main driving factors to the type of stress that is chosen.…”

Getting it right the first time: Stress-only MPI in the ER

“…Bourque et al have demonstrated that low-to-intermediate risk patient achieving at least 10 METS with no ischemic ST segment depression have an annual mortality of 0.1% and myocardial infarction rate of 0.4%. 11 Unfortunately, not all patients presenting to emergency room can exercise. Additionally, data from the Duke Treadmill Score database suggest that 64% of patients do not fall into the low-risk category necessitating further testing.…”