Exploratory Evaluation of Quantitative Rubidium-82 PET Myocardial Perfusion Parameters: Absolute Blood Flow, Flow Reserve, and Left Ventricular Function in an Arabian Gulf Cohort

Ahmad Alenezi; Masoud Garashi; Satish Panchadar; Gautam Biswas

doi:10.20944/preprints202608.0957.v1

Submitted:

13 August 2026

Posted:

14 August 2026

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Abstract

Background: Rubidium-82 (⁸²Rb) PET myocardial perfusion imaging (MPI) yields, in a single study, quantitative absolute myocardial blood flow (MBF, mL/min/g), myocardial flow reserve (MFR), and gated left ventricular (LV) function (LVEF, EDV, ESV, SV). These quantitative values depend on the tracer, scanner, kinetic model, software, and on the underlying population, and have been characterised almost exclusively in North American and European cohorts. The Arabian Gulf, where Kuwait has among the highest age-standardised diabetes prevalence worldwide (25.6%), is essentially unstudied, so the distribution and behaviour of these parameters in such a real-world cardiometabolic population are unknown. Objectives: To evaluate the distribution of the quantitative ⁸²Rb PET parameter set in a real-world Arabian Gulf cohort and, within a small strictly-defined normal subgroup, to describe sex- and age-related patterns in absolute MBF, MFR, and LV function. Given the limited size of the normal subgroup, these values are presented as exploratory, hypothesis-generating observations rather than definitive population reference norms. Methods: Retrospective single-centre study of 330 consecutive patients (mean age 63.5 ± 12.0 years) who underwent adenosine-stress ⁸²Rb PET/CT MPI. The truly-normal reference stratum, normal perfusion (C1), normal global MFR (≥ 2.0), normal resting LVEF, and no documented cardiac history, comprised 44 patients (25 female, 19 male). Reference values are reported as sex- and age-stratified centiles (5th, 25th, median, 95th percentiles), with the 5th percentile as the lower reference limit. Sex differences used Mann-Whitney U with rank-biserial r and Cohen's d (95% CI); age was examined across broad bands. All analyses followed APA 7 standards with Bonferroni correction. Results: In the truly-normal stratum, median global stress MBF was 2.94 mL/min/g (5th percentile 2.03) and median global MFR was 2.72 (5th percentile 2.06); every value satisfied the C1 definition (MFR ≥ 2.0). Consistent with published ⁸²Rb PET registries, women had higher global stress MBF (median 3.00 vs 2.91 mL/min/g) and lower MFR than men, and LV volumes were smaller in women with higher LVEF. The 5th-percentile lower reference limit for stress LVEF was 54% (women) and 53% (men). These absolute-flow reference values are lower than those reported for Western low-risk cohorts (stress MBF ~3.25 mL/min/g; MFR ~3.18), consistent with the higher cardiometabolic burden of this population. Conclusions: In this exploratory single-centre evaluation, quantitative ⁸²Rb PET flow values in a small strictly-normal Arabian Gulf subgroup were lower than Caucasian-derived values, while the expected sex and age patterns were preserved. Because the normal subgroup is small, these findings are hypothesis-generating and require confirmation in larger, prospectively screened cohorts before use as population reference values; they nonetheless indicate that population- and pipeline-specific calibration is needed when quantitative 82Rb thresholds derived elsewhere are applied locally.

Keywords:

Rubidium-82

;

PET

;

myocardial blood flow

;

myocardial flow reserve

;

exploratory analysis

;

left ventricular function

;

Arabian Gulf

;

Kuwait

Subject:

Medicine and Pharmacology - Cardiac and Cardiovascular Systems

1. Introduction

Quantitative positron emission tomography (PET) measures absolute myocardial blood flow (MBF) and myocardial flow reserve (MFR) in physiological units (mL/min/g), adding information on coronary physiology beyond relative perfusion [1]. These estimates have been validated against nitrogen-13 ammonia [2] and oxygen-15 water [3], and professional-society guidance now recommends incorporating MBF and MFR into standard stress PET reporting [4,5], with recent guidance extending quantitative flow to newer tracers [6]. Rubidium-82 (⁸²Rb), a generator-produced tracer requiring no on-site cyclotron [7], is the most widely used PET perfusion agent, and its absolute quantification depends on a robust kinetic-modelling pipeline [8,9].

A defining feature of these quantitative values is that they are not universal. Absolute flow varies with tracer, scanner, stress agent, kinetic model, and software, as shown in the multi-software RUBY-10 comparison [10], and reference behaviour also varies with age and sex [15,16] and with the metabolic profile of the population studied. Existing quantitative ⁸²Rb characterisations derive almost entirely from North American and European cohorts; because diabetes and obesity impair microvascular function and lower baseline flow [13,14], values from those cohorts may not transfer to populations with a markedly different cardiometabolic burden.

The Arabian Gulf carries among the highest age-standardised burdens of diabetes and obesity worldwide (Kuwait 25.6% in 2024 [19]), yet the distribution and behaviour of quantitative ⁸²Rb PET parameters in this setting have not been described. We therefore undertook an exploratory evaluation of the full quantitative ⁸²Rb PET parameter set,MBF and MFR by territory, LVEF, and volumes, in a real-world Kuwaiti cohort using a single Corridor4DM quantification pipeline. Within a small, strictly-defined normal subgroup we additionally describe sex- and age-related patterns; because that subgroup is limited in size, these are presented as exploratory, hypothesis-generating observations rather than definitive population reference norms.

2. Materials and Methods

2.1. Study Design and Patient Selection

This retrospective single-centre study was approved by the institutional ethics committee with a waiver of informed consent for the use of anonymised data (approval no. 2465). The cohort comprised 330 consecutive patients who underwent one-day gated rest-stress ⁸²Rb-chloride PET/CT myocardial perfusion imaging (with low-dose CT for attenuation correction) at Kuwait Chest Disease Hospital between January 2018 and December 2023 (Table 1). Rubidium-82 chloride was produced using a CardioGen-82® strontium-82/rubidium-82 generator (Bracco Diagnostics Inc., Princeton, NJ, USA) and delivered intravenously with its dedicated infusion system; pharmacologic stress was induced with adenosine. Patients were classified using the PET reporting C-category scheme. The truly-normal reference stratum, normal perfusion (C1), normal global MFR (≥ 2.0), normal resting LVEF, and no documented cardiac history, comprised 44 patients (25 female, 19 male). Patients in category C3 (normal perfusion with reduced MFR) were excluded from the normal reference because MFR is abnormal by definition in that group.

2.2. Image Acquisition

PET/CT: Rest and stress ⁸²Rb PET/CT myocardial perfusion imaging was performed on a dedicated PET/CT scanner. A CT scout was acquired (kV 120, mA 10) followed by a helical CTAC scan (kV 120, mA 145, slice thickness 3.75 mm, pitch 0.531:1, rotation time 0.8 s, CTDIvol 19.85 mGy, DLP 340.75 mGy·cm). Pharmacologic stress was induced with adenosine (0.14 mg/kg/min over 6 minutes; caffeine and theophylline withheld ≥48 hours). ⁸²Rb chloride was administered from a CardioGen-82® generator (target approximately 1,110 MBq). Dynamic list-mode data were acquired for 7-8 minutes with ECG gating during the static phase (8 or 16 frames/cycle) over a single bed position (S100.0 to I50.4), with a 2-minute pre-scan delay followed by a 4-minute static emission acquisition. Reconstruction used OSEM (3 iterations, 18 subsets) with time-of-flight and point-spread-function modelling (Q.AC wide-view, VPFX-S; DFOV 70 cm, matrix 128×128, voxel size 2.0 mm).

2.3. Reference (Strictly-Normal) Subgroup Definition

The truly-normal reference stratum comprised patients with visually normal stress and rest perfusion, normal global MFR (≥ 2.0), normal resting LVEF, and no documented history of coronary artery disease, prior myocardial infarction, revascularisation, cardiomyopathy, or congenital heart disease; adults ≥ 18 years were analysed.

2.4. Image Analysis

All myocardial perfusion datasets were processed with Corridor4DM (INVIA, Ann Arbor, MI, USA), providing a unified quantification framework across all studies. For ⁸²Rb PET, dynamic list-mode data were reframed into the standard acquisition sequence and absolute myocardial blood flow (MBF, mL·min⁻¹·g⁻¹) was computed using a one-tissue-compartment kinetic model with dual spillover correction applied to the left-ventricular blood-pool and right-ventricular input functions. Myocardial flow reserve (MFR) was derived as the ratio of stress to rest MBF, globally and for the LAD, LCx, and RCA territories defined on the standardised 17-segment model. For gated studies 4DM automatically delineated left-ventricular endocardial and epicardial surfaces and computed LVEF, EDV, ESV, and stroke volume at rest and stress. All automatically generated contours were visually inspected by an experienced operator and manually corrected where necessary. Because absolute flow and functional values depend on the kinetic model and software platform, a single quantification pipeline was used throughout; derived reference values are therefore specific to this Corridor4DM® implementation.

2.5. Statistical Analysis

Analyses were performed in R (v4.3.x) following APA 7 standards with exact p-values to three decimal places and 95% confidence intervals for effect sizes. Reference values are reported as centiles (5th, 25th, median, 95th percentiles), with the 5th percentile taken as the lower reference limit, overall and stratified by sex and by broad age band. Sex differences used Mann-Whitney U with rank-biserial r and Cohen's d; age effects were examined by Kruskal-Wallis H. Bonferroni correction was applied across parameter comparisons.

3. Results

3.1. Cohort Characteristics and Normality

Cohort characteristics for the full PET cohort and the truly-normal reference stratum are summarised in Table 1. Consistent with the retrospective clinical sampling, distributions of the quantitative parameters departed from normality (Shapiro–Wilk), supporting the use of non-parametric, centile-based reference statistics throughout.

3.2. MBF and MFR Reference Values (PET)

Median global stress MBF in the truly-normal stratum was 2.94 mL/min/g (5th percentile 2.03, 95th percentile 3.69) and median global MFR was 2.72 (5th percentile 2.06, 95th percentile 4.00). By definition every patient satisfied MFR ≥ 2.0, and the lower reference limits sit at or above the conventional 2.0 threshold, confirming internal consistency of the reference stratum.

Table 2. Stress/Rest MBF and MFR Reference Values by Territory: PET C1 Patients (n = 44).

Parameter	N	Mean	SD	5th %ile (LRL)1	25th %ile	Median	95th %ile
Stress MBF (mL/min/g)
LAD	44	2.674	0.564	1.983	2.240	2.650	3.674
LCX	44	2.878	0.623	2.000	2.395	2.935	3.856
RCA	44	3.261	0.863	1.924	2.645	3.255	4.702
Global	44	2.840	0.571	2.025	2.345	2.940	3.686
Rest MBF (mL/min/g)
LAD	44	0.993	0.251	0.681	0.818	0.930	1.407
LCX	44	1.070	0.297	0.703	0.900	1.040	1.728
RCA	44	1.077	0.297	0.706	0.877	1.035	1.652
Global	44	1.038	0.267	0.691	0.860	1.000	1.469
MFR (stress/rest)
LAD	44	2.728	0.606	2.046	2.245	2.565	3.694
LCX	44	2.770	0.691	1.964	2.198	2.580	3.825
RCA	44	3.101	0.798	2.030	2.515	3.005	4.585
Global	44	2.811	0.624	2.060	2.275	2.720	3.996

1LRL = lower reference limit (5th percentile). ASNC/SNMMI thresholds: MFR < 2.0 = abnormal, < 2.5 = borderline [4,5].

Territorial stress MBF showed the expected regional pattern, with the RCA territory demonstrating the highest median value (3.26 mL/min/g) and the LAD the lowest (2.65 mL/min/g); this distribution was consistent across age groups.

3.3. Sex-Stratified MBF and MFR Reference Values

Table 3 presents sex-stratified MBF and MFR reference values. Women had higher global stress MBF (median 3.00 vs 2.91 mL/min/g) and higher rest MBF than men, but lower global MFR (median 2.57 vs 2.98), the higher resting flow in women accounting for the lower reserve, the sex pattern consistently reported in published ⁸²Rb PET reference series.

3.4. Age-Stratified MBF and MFR Reference Values

Global MFR declined across the older age strata (median 2.87 in the <60 group to 2.59 in the ≥60 group), concordant with the negative age correlation for MFR documented by Sperry et al. [16]. Table 4 presents age-stratified MBF and MFR values.

3.5. LV Functional Parameters: Sex Differences

In the truly-normal stratum, LV volumes differed by sex: women had smaller stress EDV (median 61 vs 82 mL; Cohen's d = 0.77), ESV, and SV than men (Table 5). Stress and rest LVEF did not differ significantly by sex within this stratum (stress median 67% vs 67%; p = .81), consistent with the small, well-characterised sex-related differences in LV geometry on gated imaging [20,21]. The larger sex differences in volume than in ejection fraction reflect proportional scaling of end-diastolic and end-systolic volumes.

3.6. Age Effects on LV Functional Parameters

Across broad age bands, absolute stress MBF and MFR declined modestly with age, while LVEF was comparatively age-stable, consistent with the expected age dependence of flow reserve and the relative age-independence of ejection fraction. Given the size of the truly-normal stratum, age-stratified centiles are reported for two broad bands and should be regarded as indicative.

Table 6. Age effects on LV functional parameters (Kruskal-Wallis, truly-normal stratum, < 60 vs ≥ 60 years).

Parameter	Modality	H (df=1)	p	eta2	eta2 95% CI1	Sig.
Stress LVEF (%)	PET	0.08	0.777	0.000	[0.000, 1.000]	ns
Stress EDV (mL)	PET	2.28	0.131	0.030	[0.005, 1.000]	ns
Stress SV (mL)	PET	2.10	0.147	0.026	[0.036, 1.000]	ns

* p < .05, ** p < .01, *** p < .001. eta2 = rank eta-squared. Wide CI upper bounds reflect small reference stratum n. 1η² CI upper bounds of 1.000 are an artifact of the rank-based interval at small n and should not be interpreted as the plausible effect ceiling.

3.7. LV Functional Reference Values (by Sex)

Table 7 presents sex-stratified reference values for LV functional parameters in the truly-normal stratum. The 5th-percentile lower reference limits for stress LVEF were 54% (women) and 53% (men), physiologically appropriate lower bounds for a normal reference, in contrast to the implausibly low values obtained before the stratum was restricted to truly-normal patients.

3.8. Age-Stratified LV Functional Reference Values

Table 8 presents age-stratified reference values for key LV functional parameters. As expected from the Kruskal-Wallis analysis, stress LVEF was stable across age groups (medians 55-68%), while stress SV declined in the older groups.

4. Discussion

4.1. Summary and Contributions

To our knowledge, provide exploratory sex- and age-stratified reference dataset for the complete ⁸²Rb PET parameter set reported in an Arabian Gulf population. No prior reference ⁸²Rb PET series appears to have been derived from an Arabian Gulf or Middle Eastern cohort, as existing databases originate predominantly from North American and European populations [15]; this represents a population and geographic gap rather than a claim of absolute primacy, since a fully exhaustive search of regional and non-indexed literature was beyond the scope of this work.

The dataset's value lies in several further features. It reports absolute MBF, MFR, and LV functional parameters from a single integrated cohort and quantification pipeline, in a population under-represented in existing ⁸²Rb reference data, using categories re-derived from source data to ensure internal consistency with the C1 definition.

4.2. MBF and MFR: Clinical Context

The ASNC/SNMMI abnormal MFR threshold of 2.0 derives largely from predominantly Caucasian cohorts [4]. Within our truly-normal stratum the global MFR 5th-percentile lower reference limit was 2.06, closely bracketing the conventional 2.0 threshold, indicating that the widely used cut-off is broadly applicable in this Gulf population even though the central tendency of flow is lower.

The broader clinical implication is methodological: lower reference limits are sensitive to kinetic model, software platform, and cohort selection, so locally derived limits are preferable to transplanting limits from cohorts processed with different pipelines [10,14]. The territorial MFR pattern, with the highest reserve in the RCA territory, is consistent with regional variation reported in prior ⁸²Rb PET reference data and supports territory-specific assessment alongside global MFR, as regional deficits may be obscured by global averaging.

4.3. Lower Absolute Flow and Its Metabolic Basis

Absolute stress MBF and MFR in this Gulf cohort were lower than values reported in Western low-risk PET series, a shift consistent with the population's high burden of diabetes and obesity, which impair endothelial and microvascular function and depress hyperaemic flow. This matters clinically: quantitative thresholds and lower reference limits derived from predominantly Caucasian, metabolically healthier cohorts may not transfer directly, and applying them unmodified risks misclassifying flow as abnormal, or masking true impairment, in Gulf patients. Diabetic patients in particular show markedly reduced coronary flow reserve that carries prognostic weight even without epicardial disease [25], underscoring the need for population- and pipeline-specific calibration rather than a single universal cut-off.

4.4. Sex and Age Patterns

Within the normal subgroup, women had higher absolute stress and rest MBF but lower MFR than men, and flow declined modestly with age while ejection fraction remained comparatively stable. The higher perfusion in women is concordant with independent cross-modality evidence that female sex is associated with greater myocardial perfusion and blood volume beyond other physiological factors [26]. That these expected sex- and age-related patterns are reproduced in an independent population and pipeline supports the validity of the measurements, and indicates that any locally-derived reference framework should remain sex- and age-stratified.

4.5. Prognostic Relevance of Reduced Flow Reserve

Although this analysis is descriptive, reduced MFR is among the most consistently validated prognostic markers in cardiac PET: noninvasive coronary flow reserve independently predicts cardiac death and adds risk information beyond perfusion and clinical variables [25], and integrated physiological assessment shows flow reserve to be a dominant correlate of cardiovascular mortality [27]. In the same cohort studied here, an MFR below 2.0 was associated with higher all-cause mortality, indicating that the flow-reserve threshold retains prognostic meaning in this population and that the descriptive reference values reported here mark a clinically relevant boundary.

4.6. Limitations

Several limitations should be acknowledged. First, the truly-normal stratum comprised clinically referred patients judged disease-free rather than prospectively screened healthy volunteers, and was modest in size (n = 44), so the tabulated centiles, particularly within age strata, are estimates that warrant confirmation in larger cohorts. Coronary calcium was documented in only a minority of reports, limiting a stricter calcium-zero definition.

5. Conclusions

This exploratory study provides sex- and age-stratified reference values for absolute ⁸²Rb PET myocardial blood flow, flow reserve, and LV function in an Arabian Gulf population. The global MFR lower reference limit (2.06) brackets the conventional 2.0 threshold, and the absolute-flow values are lower than Western low-risk references while the sex and age patterns are preserved. Population- and pipeline-specific reference ranges should be used for accurate clinical interpretation, and these descriptive values warrant prospective confirmation in larger, healthy-screened cohorts.

Author Contributions

Conceptualization, A.A.; methodology, A.A.; formal analysis, A.A.; investigation and data interpretation, M.G., S.P. and G.B.; writing—original draft preparation, A.A.; writing—review and editing, all authors. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

The study was conducted in accordance with the Declaration of Helsinki and approved by the Institutional Review Board of Kuwait Chest Disease Hospital (approval no. 2456).

Informed Consent Statement

Patient consent was waived owing to the retrospective use of anonymised data, as approved by the Institutional Review Board.

Data Availability Statement

The data supporting the findings of this study are available from the corresponding author upon reasonable request.

Conflicts of Interest

The authors declare no conflicts of interest.

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Table 1. Cohort characteristics: full PET cohort and C1 reference stratum.

Characteristic	Full PET cohort (n = 330)	C1 normative stratum (n = 44)
Female / male	145 / 185	25 / 19
Female (%)	43.9%	56.8%
Age, mean +/- SD (y)	63.5 +/- 12.0	59.9 +/- 11.3
Age range (y)	12 - 91	39 - 85

PET C1 = normal perfusion + normal global MFR (≥ 2.0). The reference stratum additionally required normal resting LVEF and no documented cardiac history (n = 44). C3 (normal perfusion + reduced MFR) was excluded from the normal reference.

Table 3. Sex-Stratified MBF and MFR Reference Values: PET C1 Patients.

Parameter	Sex	N	Mean	SD	5th %ile	Median	95th %ile
Global Stress MBF (mL/min/g)	Female	25	2.894	0.597	2.138	3.000	3.902
Global Stress MBF (mL/min/g)	Male	19	2.769	0.544	1.975	2.910	3.379
Global Rest MBF (mL/min/g)	Female	25	1.130	0.284	0.800	1.070	1.642
Global Rest MBF (mL/min/g)	Male	19	0.916	0.189	0.679	0.900	1.211
Global MFR	Female	25	2.612	0.497	2.044	2.570	3.416
Global MFR	Male	19	3.073	0.687	2.159	2.980	4.219
LAD MFR	Female	25	2.474	0.431	2.032	2.350	3.264
LAD MFR	Male	19	3.062	0.651	2.192	3.150	4.213
LCX MFR	Female	25	2.586	0.586	1.966	2.440	3.592
LCX MFR	Male	19	3.013	0.757	1.972	2.910	3.887
RCA MFR	Female	25	2.961	0.705	2.034	2.990	4.288
RCA MFR	Male	19	3.285	0.891	2.195	3.120	4.756

Table 4. Age-Stratified MBF and MFR Reference Values: PET C1 Patients.

Age Group	Parameter	N	Mean	SD	5th %ile	Median	95th %ile
< 60	Global Stress MBF	24	2.938	0.566	2.069	3.105	3.542
< 60	Global MFR	24	2.920	0.671	2.043	2.865	3.995
≥ 60	Global Stress MBF	20	2.723	0.569	2.019	2.655	3.722
≥ 60	Global MFR	20	2.680	0.550	2.155	2.585	3.749

Age stratified into two broad bands owing to the size of the truly-normal stratum; centiles are indicative.

Table 5. Sex differences in LV functional parameters within the truly-normal stratum (Mann-Whitney U, Bonferroni-adjusted).

Parameter	Median Men	Median Women	U	p (Bonf.)	r	d [95% CI]	Sig.
Stress LVEF (%)	67	67	248	0.812	0.044	-0.42 [-0.63, -0.19]	ns
Stress EDV (mL)	82	61	351	0.007	0.478	0.77 [0.54, 0.99]	*
Stress ESV (mL)	23	21	300	0.145	0.261	0.56 [0.34, 0.78]	ns
Stress SV (mL)	52	41	370	0.002	0.556	0.76 [0.53, 0.98]	*
Rest LVEF (%)	60	59	250	0.767	0.055	-0.44 [-0.66, -0.22]	ns
Rest EDV (mL)	64	51	348	0.009	0.463	0.70 [0.47, 0.92]	*
Rest ESV (mL)	25	21	330	0.030	0.387	0.57 [0.35, 0.79]	*
Rest SV (mL)	38	31	354	0.006	0.488	0.69 [0.47, 0.91]	*

r = rank-biserial correlation; direction of each difference is given by the median columns. *** p (Bonf.) < .001, ns = not significant. d = Cohen's d (pooled SD) with 95% CI.

Table 7. Sex-stratified LV functional reference values: truly-normal stratum (n = 44).

Parameter	Sex	N	Mean	SD	5th %ile	Median	95th %ile
LV Functional : Stress
LVEF (%)	Female	25	66.1	8.1	54.2	67.0	78.2
LVEF (%)	Male	19	66.5	7.8	52.9	67.0	75.6
EDV (mL)	Female	25	63.3	18.2	42.2	61.0	88.8
EDV (mL)	Male	19	82.7	26.7	53.4	82.0	144.2
ESV (mL)	Female	25	22.5	11.1	11.2	21.0	37.2
ESV (mL)	Male	19	28.3	12.8	12.0	23.0	50.9
SV (mL)	Female	25	40.8	9.5	26.4	41.0	56.8
SV (mL)	Male	19	54.5	17.0	35.6	52.0	88.7
LV Functional : Rest
LVEF (%)	Female	25	60.3	7.1	52.2	59.0	68.8
LVEF (%)	Male	19	60.2	5.4	51.9	60.0	69.4
EDV (mL)	Female	25	50.7	15.1	28.6	51.0	74.0
EDV (mL)	Male	19	68.8	26.4	38.4	64.0	127.1
ESV (mL)	Female	25	19.8	6.2	13.2	21.0	26.8
ESV (mL)	Male	19	27.5	11.6	13.9	25.0	51.2
SV (mL)	Female	25	30.9	10.3	15.4	31.0	47.2
SV (mL)	Male	19	41.4	16.6	24.5	38.0	75.5

LRL = 5th percentile (lower reference limit); URL = 95th percentile. Values are for the truly-normal stratum (n = 44).

Table 8. Age-stratified LV functional reference values: truly-normal stratum (n = 44).

Age Group	Parameter	N	Mean	SD	5th %ile	Median	95th %ile
< 60	Stress LVEF (%)	24	66.7	9.0	52.1	67.5	80.7
< 60	Stress SV (mL)	24	48.7	15.6	32.6	47.0	64.2
≥ 60	Stress LVEF (%)	20	65.8	6.6	55.0	67.0	75.0
≥ 60	Stress SV (mL)	20	44.4	13.6	31.7	41.5	60.4

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