Direct comparison of adenosine and adenosine 5'-triphosphate as pharmacologic stress agents in conjunction with Tl-201 SPECT: Hemodynamic response, myocardial tracer uptake, and size of perfusion defects in the same subjects

Adenosine Triphosphate Stress Myocardial Strain in Ischemic Heart Disease: An Animal Study with Histological Validation

RATIONALE AND OBJECTIVES

It is still challenging for cardiac magnetic resonance (CMR) to detect ischemic heart disease (IHD) without the use of gadolinium contrast. We aimed to evaluate the potential value of adenosine triphosphate (ATP) stress myocardial strain derived from feature tracking (FT) as a novel method for detecting IHD in a swine model.

MATERIALS AND METHODS

CMR cines, myocardial perfusion imaging at rest and during ATP stress, and late gadolinium enhancement were obtained in both control and IHD swine. Normal, remote, ischemic, and infarcted myocardium were analyzed. The diagnostic accuracy of myocardial strain for infarction and ischemia was assessed using coronary angiography and pathology as reference.

RESULTS

Eleven IHD swine and five healthy control swine were enrolled in this study. Strain parameters, even at rest, were associated with myocardial ischemia and infarction(all p < 0.05). The area under receiver operating characteristic curve (AUC) values of all strain parameters for detecting infarcted myocardium exceeded 0.900 (all p < 0.05). The AUC values for detecting ischemic myocardium were as follows: 0.906 and 0.847 for stress and rest radial strain, 0.763 and 0.716 for stress and rest circumferential strain, 0.758 and 0.663 for stress and rest longitudinal strain (all p < 0.001). Heat maps demonstrated that all strain parameters showed mild to moderate correlations with the stress myocardial blood flow and myocardial perfusion reserve (all p < 0.05).

CONCLUSION

CMR-FT-derived ATP stress myocardial strain shows promise as a noninvasive method for detecting myocardial ischemia and infarction in an IHD swine model, with rest strain parameters offering potential as a needle-free diagnostic option.

Histologic validation of stress cardiac magnetic resonance T1-mapping techniques for detection of coronary microvascular dysfunction in rabbits

BACKGROUND

To investigate the diagnostic performance of stress cardiac magnetic resonance (CMR) T1-mapping for the detection of coronary microvascular dysfunction (CMD) by correlating microvascular density (MVD) and collagen volume fraction (CVF) with T1 response to adenosine triphosphate (ATP) stress (stress ΔT1) in rabbits.

METHODS

Twenty-four New Zealand white rabbits were randomly divided into the CMD group induced by microembolization spheres (n = 10), sham-operated group (n = 5), and control group (n = 9). All rabbits underwent 3.0 T CMR, both rest and ATP stress T1-maps were obtained, and first-pass perfusion imaging was performed. Stress ΔT1 and myocardial perfusion reserve index (MPRI) were calculated. For the histologic study, each rabbit was sacrificed after CMR scanning. Left ventricular myocardial tissue was stained with Hematoxylin-eosin (H&E), Masson, and CD31, from which MVD and CVF were extracted. Pearson correlation analyses were performed to determine the strength of the association between the stress ΔT1 and both MVD and CVF.

RESULTS

The stress ΔT1 values (CMD, 2.53 ± 0.37% vs. control, 6.00 ± 0.64% vs. Sham, 6.07 ± 0.97%, p < 0.001) and MPRI (CMD, 1.45 ± 0.13 vs. control, 1.94 ± 0.23, vs. sham, 1.89 ± 0.15, p < 0.001) were both lower in CMD rabbits compared with sham-operated and control rabbits. Further, the stress ΔT1 showed a high correlation with CVF (r = -0.806, p < 0.001) and MVD (r = 0.920, p < 0.001).

CONCLUSIONS

Stress T1 response strongly correlates with pathological MVD and CVF, indicating that stress CMR T1 mapping can accurately detect microvascular dysfunction.

KSNM60 in Cardiology: Regrowth After a Long Pause

The Korean Society of Nuclear Medicine (KSNM) is celebrating its 60th anniversary in honor of the nuclear medicine professionals who have dedicated their efforts towards research, academics, and the more comprehensive clinical applications and uses of nuclear imaging modalities. Nuclear cardiology in Korea was at its prime time in the 1990s, but its growth was interrupted by a long pause. Despite the academic and practical challenges, nuclear cardiology in Korea now meets the second leap, attributed to the growth in molecular imaging tailored for many non-coronary diseases and the genuine values of nuclear myocardial perfusion imaging. In this review, we describe the trends, achievements, challenges, and perspectives of nuclear cardiology throughout the 60-year history of the KSNM.

Prognostic value of perfusion cardiovascular magnetic resonance with adenosine triphosphate stress in stable coronary artery disease

BACKGROUND

Adenosine triphosphate (ATP) has been predominantly used in the Asia-Pacific region for stress perfusion cardiovascular magnetic resonance (CMR). We evaluated the prognosis of patients stressed using ATP, for which there are no current data.

METHODS

We performed a retrospective longitudinal study from January 2016 to December 2020 and included 208 subjects with suspected obstructive coronary artery disease (CAD) who underwent ATP stress perfusion CMR. An inducible stress perfusion defect was defined as a subendocardial dark rim involving ≥ 1.5 segments that persisted for ≥ 6 beats during stress but not at rest. The primary outcome measure was a composite of major adverse cardiovascular events (MACE) including (1) cardiac death, (2) nonfatal myocardial infarction, (3) cardiac hospitalization, (4) late coronary revascularization. We compared outcomes in patients with and without perfusion defect using Kaplan-Meier and log rank tests. Significant predictors of MACE were identified using multivariable Cox regression analysis.

RESULTS

Median follow-up was 3.3 years. Patients with no stress perfusion defect had a lower incidence of MACE (p < 0.001), including lower cardiac hospitalization (p = 0.004), late coronary revascularization (p = 0.001) and cardiac death (p = 0.003). Significant independent predictors for MACE were stress induced perfusion defect (p < 0.001, hazard ratio [HR] = 3.63), lower left ventricular ejection fractino (LVEF) (p < 0.001, HR = 0.96) and infarct detected by late gadolinium enhancement (LGE) (p = 0.001, HR = 2.92).

CONCLUSION

Perfusion defects on ATP stress are predictive of MACE which is driven primarily by cardiac hospitalization, late coronary revascularization and cardiac death. Significant independent predictors of MACE were stress induced perfusion defect, lower LVEF and infarct detected by LGE.

Clinical Outcomes of Dynamic Computed Tomography Myocardial Perfusion Imaging Combined With Coronary Computed Tomography Angiography Versus Coronary Computed Tomography Angiography–Guided Strategy

Background:

Dynamic computed tomography (CT) myocardial perfusion imaging (MPI) provides quantitative myocardial blood flow for the precise assessment of myocardial ischemia. However, compared with coronary CT angiography (CCTA), whether this functional imaging modality can reduce invasive coronary angiography without revascularization remains unknown. We aimed to determine the clinical outcomes of a dynamic CT-MPI+CCTA-guided versus CCTA-guided strategy in patients with suspected coronary artery disease.

Methods:

Consecutive patients with intermediate pretest probability of coronary artery disease were prospectively enrolled and randomized to dynamic CT-MPI+CCTA-guided or CCTA-guided workup. The primary end point was the rate of invasive coronary angiography without revascularization within 3 months. The secondary end point was a composite of major adverse cardiac event at the 3-month, 6-month, and 1-year follow-up.

Results:

A total of 240 patients (mean age, 69.01±11.2 years; 173 men) were included. The total radiation dose and contrast media usage within 90 days were higher in the CT-MPI+CCTA group than in the CCTA group (10.3 versus 7.1 mSv, P =0.031; 134.5±40.6 versus 108.1±48.2 mL, P <0.0001). Compared with the CCTA-guided group, the CT-MPI+CCTA-guided group had significantly lower rates of invasive coronary angiography within 90 days (48.3% [58/120] versus 30.8% [37/120], P =0.006) and invasive coronary angiography without revascularization (50.0% [29/58] versus 10.8% [4/37], P <0.0001). There were no significant differences regarding the frequency of major adverse cardiac event between the 2 groups at the 3-month, 6-month, and 1-year follow-up.

Conclusions:

In patients with intermediate pretest probability of coronary artery disease, CT-MPI+CCTA-guided patient management may be preferred over the CCTA-guided strategy as an approach to reduce unnecessary invasive procedures.

Incidence of atrioventricular block with vasodilator stress SPECT: A meta-analysis

BACKGROUND

Adenosine or regadenoson are often used with pharmacologic stress testing. Adenosine may trigger atrioventricular block (AVB). Despite its higher selectivity, regadenoson has also been associated with AVB. We studied the incidence of de novo AVB with these agents.

METHODS

A comprehensive search of SCOPUS was performed from inception to March 2016. Studies of at least 10 patients, using adenosine and/or regadenoson with SPECT-MPI, reporting rates of AVB were selected for further review.

RESULTS

Thirty four studies were pooled including 22,957 patients. Adenosine was used in 21 studies and regadenoson in 15. Both were administered in two studies. The estimated incidence of overall and high-grade AVB was 3.81% (95% CI 1.99%-6.19%) and 1.93% (95% CI 0.77%-3.59%), respectively. The incidence of AVB (8.58%; 95% CI 5.55%-12.21% vs 0.30%; 95% CI 0.04%-0.82%, respectively, P < .001) and high-grade AVB (5.21%; 95% CI 2.81%-8.30% vs 0.05%; 95% CI < .001%-0.19% respectively, P < .001) were higher with adenosine compared to regadenoson.

CONCLUSION

AVB is seen in about 4% of patients undergoing vasodilator stress test. Both overall and high-grade AVB are more frequent with adenosine compared to regadenoson.

Vasodilatory effect of adenosine triphosphate does not change cerebral blood flow: a PET study with (15)O-water

OBJECTIVE

Adenosine triphosphate (ATP) is the parent compound of adenosine and well known as a powerful vasodilator. To investigate the effect of ATP on cerebral blood flow (CBF) and cerebral vessels, (15)O-water positron emission tomography (PET) studies were performed to evaluate changes in CBF and blood volume before and after ATP administration.

METHODS

Ten healthy young volunteers underwent (15)O-water PET scans under the conditions of baseline, 3 and 1 min after ATP continuous infusion. CBF values in cortical regions of the bilateral middle cerebral arteries and basal ganglia were obtained for each subject. Statistical parametric mapping (SPM) was applied for analysis of regional changes. Physiologic parameters, such as blood gas and blood pressure were also measured.

RESULTS

Cortical CBF showed no significant change after continuous infusion of ATP compared with the baseline. Dilatation of major vessels induced by ATP was visualized on SPM analysis. Heart rates increased and mean blood pressure decreased during ATP administration while blood gas data showed no changes between the different conditions.

CONCLUSIONS

Intravenous ATP administration caused dilatation of major cerebral vessels but no significant change in CBF under normoventilation and decrease in systemic blood pressure, indicating that this no change in CBF under vasodilatory effect of ATP may be caused by cerebral microvascular autoregulation.

[Study of efficacy and safety of pharmacological stress tests in nuclear cardiology]

BACKGROUND/AIM

Treadmill test combined with myocardial perfusion scintigraphy (MPS) is a commonly used technique in the assessment of coronary artery disease. Many patients who cannot adequately perform exercise stress testing may nevertheless undergo pharmacological tests, most commonly with the vasodilator agents (adenosine and dipyridamole), as well as the positive inotropic agent dobutamine. Patients undergoing vasodilators stress testing with either dipyridamole or adenosine also perform simultaneous low-intensity exercise. The aim of this study was to compare various pharmacological stress tests alone or in combination with low intensity exercise as preparation for MPS in regard to incidence of adverse effects, quality of diagnostic image and the acquisition initial time.

METHODS

A total of 2 205 patients underwent pharmacological stress tests. Pharmacological stress test with adenosine was applied in 493 patients. In 405 of them we performed concomitant low level exercise (50 W) by bicycle ergometar (AdenoEX). In 88 of them we performed adenosine abbreviated protocol (AdenoSCAN). In 1 526 patients we performed pharmacological stress test with dipyridamole. In 871 of them we performed concomitant low level exercise (50 W) by bicycle ergometar (DipyEX), and in 775 we used only dipyridamole protocol (DipySCAN). In 186 patients we used pharmacological stress test with dobutamine. We followed side effects of adenosine, dipyiridamole and dobutamine, compared results between protocols with concomitant low level exercise and vasodilatators only. We also compared image quality, and suggested time of acquisition after stress test.

RESULTS

We found numerous side effects especially with adenosine, but these effects were short-lived and not required active interventions. Benefit with concomitant exercise in booth AdenoEX and DipyEX included decreased side effects (AdenoEX vs AdenoSCAN 620% vs 87%, respectively, and DipyEX vs DipySCAN 37% vs 59%, respectively) improved safety and patients tolerance, improved target-to-background ratios because of less subdiaphragmal activity, and earlier acquisition time. Because of producing a lot of arrhythmias (in 49% of patients) dobutamin was considered a last choice for pharmacological stress testing.

CONCLUSION

Safety and efficacy of vasodilatators (adenosine, dipyridamole) pharmacological stress tests are good, but with concomitant exercise even better. The safety and efficacy of adenosin are better than those of dipyridamole. AdenoEX protocol provides good safety and patients tolerancy. In light of these benefits we recommend AdenoEX whenever possible. Dobutamine is the last pharmacological toll for MPS.