Prognostic importance of myocardial ischemia and infarction on perfusion CMR and myocardial perfusion SPECT

Background: The presence of ischemia or infarction can be evaluated with myocardial perfusion CMR (pCMR) or SPECT (MPS). Both modalities are known to have prognostic value; however, direct comparisons based on large clinical databases are scarce. The objective was to compare the long-term risk of major adverse cardiovascular events (MACE) associated with ischemia and infarction as detected by pCMR or MPS.

Methods: This was a single-centre registry study of patients referred for pCMR or MPS between 2016 and 2022. Patients were included if they were more than18 years old and had a complete examination available. Presence of ischemia and infarction was determined from the clinical reports for both modalities. All pCMR examinations were performed at 1.5T using a single-bolus, dual sequence for quantitative perfusion mapping. Patients were followed for up to five years, with outcome data obtained from national registries. MACE was defined as cardiovascular death, myocardial infarction, unstable angina, or coronary intervention.

Results: The study cohort comprised 4454 patients with a mean age of 64 years; 54 % were male and 24% had prior ischemic heart disease (IHD). In the pCMR group (n=2159), 20% (n=425) had ischemia and 20% (n=432) had infarction. In the MPS group (n=2295) 14% (n=321) had ischemia and 18% (n=418) had infarction. During follow-up, MACE occurred in 196 CMR patients and in 185 MPS patients (Table 1). Figures 1 and 2 show the risk associated with ischemia and infarction for both modalities. In Cox-models adjusting for risk factors and ejection fraction, the hazard ratio (HR) for ischemia was 4.1 (3.0-5.6, p< 0.001) for pCMR and 2.4 (1.7-3.3, p< 0.001) for MPS. For infarction the HR was 1.6 (1.1-2.3, p< 0.01) for pCMR and 1.1 (0.7-1.5, p= 0.76) for MPS. The regression models yielded an area under the curve (AUC) of 0.83 (pCMR) and 0.78 (MPS) for predicting MACE during follow-up.

Conclusion: The presence of ischemia is of major prognostic importance for both pCMR and MPS, whereas infarction is only an independent risk factor when found on pCMR. The risk of MACE is substantially higher among patients with abnormal CMR findings as illustrated by the higher hazard ratio and AUC.

Table 1. Baseline Characteristics by modality

Variable	Overall  n = 4454	CMR  n = 2159	MPS  n = 2295	p-value1
Age (years)	63.7 ± 12.5	65.3 ± 12.3	62.2 ± 12.5	< 0.001
Male	2420 (54%)	1212 (56%)	1208 (53%)	0.021
Prior IHD	1058 (24%)	503 (23%)	555 (24%)	0.51
Hypertension	1440 (32%)	688 (32%)	752 (33%)	0.54
Diabetes	600 (13%)	257 (12%)	343 (15%)	0.003
LVEF (%)	55.4 ± 10.2	55.7 ± 11.7	55.2 ± 8.6	0.085
Ischemia	746 (17%)	425 (20%)	321 (14%)	< 0.001
Infarction	850 (19%)	432 (20%)	418 (18%)	0.13
MACE	381 (8.6%)	196 (9.1%)	185 (8.1%)	0.23
Follow-up time	3.1 ± 1.4	2.5 ± 1.0	3.6 ± 1.5	< 0.001
Data expressed as mean ± SD or n (%). IHD = Ischemic Heart disease, LVEF = Left Ventricular Ejection Fraction, MACE = Major Adverse Cardiovascular Events
1Welch Two Sample t-test; Pearson's Chi-squared test

Table 2. Cox regression models by modality

	pCMR			MPS
Characteristic	HR	95% CI	p-value	HR	95% CI	p-value
Age (years)	1.02	1.01, 1.04	0.005	1.03	1.02, 1.05	< 0.001
Female	0.85	0.62, 1.17	0.32	0.70	0.50, 0.98	0.037
Prior IHD	1.68	1.20, 2.37	0.003	1.54	1.08, 2.18	0.016
Hypertension	1.13	0.82, 1.54	0.45	1.74	1.24, 2.44	0.001
Diabetes	1.30	0.92, 1.83	0.13	1.16	0.82, 1.65	0.40
LVEF (%)	0.98	0.97, 0.99	< 0.001	0.98	0.97, 1.00	0.012
Ischemia	4.05	2.96, 5.55	< 0.001	2.38	1.70, 3.33	< 0.001
Infarction	1.63	1.13, 2.34	0.008	1.06	0.74, 1.51	0.76
Abbreviations: CI = Confidence Interval, HR = Hazard Ratio, IHD = Ischemic Heart Disease, LVEF = Left Ventricular Ejection Fraction

Figure 1: Kaplan-Meier curves with 95% confidence intervals for the composite endpoint stratified by modality and the presence of ischemia.
Figure 2: Kaplan-Meier curves with 95% confidence intervals for the composite endpoint stratified by modality and the presence of infarction.