Incremental prognostic value of gated Rb-82 positron emission tomography myocardial perfusion imaging over clinical variables and rest LVEF

Abstract

Objectives: This investigation sought to study the incremental value of gated rubidium (Rb)-82 positron emission tomography (PET) myocardial perfusion imaging (MPI) over clinical variables for predicting survival and future cardiac events.

Background: The prognostic value of Rb-82 PET-MPI and left ventricular ejection fraction (LVEF) reserve (stress minus rest LVEF) is not well defined.

Methods: 1,432 consecutive patients undergoing gated rest/vasodilator stress rubidium-82 PET were followed up for at least 1 year. Of these, rest and peak stress LVEF and LVEF reserve were available in 985 patients. Cardiac events (CE) including cardiac death or nonfatal myocardial infarction and all-cause death were assessed.

Results: Over a mean follow-up of 1.7 +/- 0.7 years, 83 (5.8%) CE and 140 (9.7%) all-cause death were observed. There was an increase in risk for both end points with an increasing percentage of abnormal and ischemic myocardium. With normal, mild, moderate, or severely ischemic scans, the observed annualized rates of CE were 0.7%, 5.5%, 5%, and 11% and of all-cause death were 3.3%, 7.2%, 6.9%, and 12.5%, respectively. In 985 patients with peak stress gated data, the observed annualized rates of CE (2.1% vs. 5.3%, p < 0.001) and all-cause death (4.3% vs. 9.2%, p < 0.001) were higher in patients with an LVEF reserve <0% compared with those with an LVEF reserve >or=0%. On Cox proportional hazards analysis, after consideration of clinical, historical, and rest LVEF information, stress PET results and LVEF reserve yielded incremental prognostic value with respect to both CE and all-cause death.

Conclusions: Vasodilator stress Rb-82 PET-MPI provides incremental prognostic value to historical/clinical variables and rest LVEF to predict survival free of CE and all-cause death. An increasing percentage of ischemia on PET-MPI is associated with an increase in the risk of CE and all-cause death. Left ventricular ejection fraction reserve provides significant independent and incremental value to Rb-82 MPI for predicting the risk of future adverse events.

Figure 1. Event-Free Survival as a Function of Percent Myocardium Abnormal

Kaplan-Meier survival curves showing unadjusted cumulative survival free of cardiac events (CE) as a function of percent myocardium abnormal. Overall survival free of CE was best in the group with 0% abnormal myocardium. Event-free survival worsened with increasing percent abnormal myocardium.

Figure 2. Event Rates in Patients With Normal and Abnormal LVEF Reserve

Annualized rates of cardiac events (CE) (cardiac death and nonfatal myocardial infarction) and all-cause death were lower in patients with left ventricular ejection fraction (LVEF) reserve ≥0% compared to those with LVEF reserve <0%. †p < 0.001 for CE and all-cause death.

Figure 3. Predicted Event-Free Survival as a Function of Ischemic Burden

The predicted event-free survival as a function of percent myocardium ischemic. The predicted survival (risk-adjusted) free of cardiac events was best in a patient with 0% myocardium ischemic. Survival worsened progressively with 10%, 20%, or 30% myocardium ischemic.

Figure 4. Predicted Event-Free Survival as a Function of Rest LVEF and Ischemic Burden

The risk adjusted predicted survival free of cardiac events in a patient with varying degrees of left ventricular systolic dysfunction and no ischemia (A) or severe ischemia (B). The predicted survival free of cardiac events was best in a patient with an LVEF of 50%. Survival free of cardiac events was worse in a patient with an LVEF of 20% or 35%. For a given LVEF, survival free of cardiac events was worse in a patient with severe ischemia (20% ischemic myocardium, B) compared to a patient with no ischemia (0% myocardium ischemic, A).

Figure 5. Event-Free Survival as a Function of LVEF Reserve

The risk-adjusted survival free of cardiac events in patients with normal and abnormal left ventricular ejection fraction (LVEF) reserve. Risk-adjusted survival free of cardiac events was significantly better in patients with an LVEF reserve of ≥0% compared to those with an LVEF reserve of <0%.