Prediction of Short-Term Cardiovascular Events Using Quantification of Global Myocardial Flow Reserve in Patients Referred for Clinical 82Rb PET Perfusion Imaging

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FIGURE 1.
Global MFR is determined by dividing absolute MBF during stress by MBF at rest. Shown are regression plots for MFR and rest MBF (A), MFR and rest MBF after correction for baseline cardiac work by normalization for rate–pressure product (B), and MFR and MBF during pharmacologic vasodilation using dipyridamole stress (C).
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FIGURE 2.
Prognostic value of myocardial perfusion, myocardial stress flow, and MFR for entire population. Survival curves according to Kaplan–Meier for abnormal vs. normal relative regional perfusion in all subjects (n = 225) (A), lower vs. upper half of quantitative stress myocardial flow (stress MBF) (B), and MFR as measure of microvascular function in all subjects (C).
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FIGURE 3.
Prognostic value of MFR and stress MBF for patients with normal regional perfusion, as defined by SSS below 4 (n = 178). Survival curves according to Kaplan–Meier for lower vs. upper half of quantitative stress myocardial flow (stress MBF) (A) and MFR (B). In normal-perfusion patients, MFR was still predictive for adverse outcome whereas stress MBF did not show significant predictability for events.

TABLE 1

Clinical Characteristics of Study Group

Variable	Entire study group (n = 275)	Subjects included in outcome analysis (n = 224)
Age (y)	57 ± 12	58 ± 13
Sex
Men	112 (40)	86 (38)
Women	163 (60)	138 (62)
Race
White	82 (30)	61 (27)
Black	181 (66)	159 (71)
Other	12 (4)	4 (2)
Body mass index (kg/m²)	32 ± 9	32 ± 9
Known CAD	91 (33)	87 (39)
History of prior myocardial infarction	30 (11)	26 (12)
Pretest CAD likelihood^*
Low	101 (37)	82 (37)
Intermediate	62 (22)	43 (19)
High	21 (8)	12 (5)
History of smoking	94 (34)	83 (37)
History of hypertension	175 (60)	140 (63)
History of hyperlipidemia	122 (44)	101 (45)
History of diabetes mellitus	90 (33)	78 (34)
Medication at PET
β-Blocker	50 (18)	32 (14)
Angiotensin-converting enzyme inhibitor or angiotensin receptor blocker	58 (21)	46 (21)
Statin	60 (22)	44 (20)

TABLE 2

Results of Multivariate Cox Regression Analyses Assessing Relationship Between PET Variables and Outcome, Adjusted for Age

Variable	Relative hazard	95% confidence interval	P
MFR < 2.11	2.93	1.30%–6.65%	0.009
Abnormal SSS > 4	2.51	1.24%–5.10%	0.011
Stress myocardial flow < 1.90 mL/min/g	—^*		0.09
Stress left ventricular ejection fraction < 45%	—^*		0.10

↵* Variables that were removed from final model.
All models were adjusted for age as stratification factor. Patients were divided into 3 equal groups based on age. Cutoffs for groups were 24–51, 52–62, and 63–88. P value denotes level of significance that led to exclusion of variables.