Simultaneous assessment of coronary flow reserve and left ventricular function during vasodilator stress evaluated by 13N-ammonia hybrid PET/MRI

AIM

To explore changes in left ventricular (LV) function and the relationship of these changes with myocardial blood flow (MBF) evaluated by ¹³N-ammonia hybrid positron-emission tomography (PET)/magnetic resonance imaging (MRI) during vasodilator stress in patients with suspected coronary artery disease (CAD).

MATERIALS AND METHODS

Fifty-two consecutive patients with suspected CAD, who underwent ¹³N-ammonia PET/MRI, were enrolled. Vasodilator stress was induced by intravenous injection of adenosine. MBF and coronary flow reserve (CFR) were calculated from dynamic acquisition of ¹³N-ammonia PET. LV function was evaluated by MRI both at rest and during vasodilator stress. An abnormal perfusion on myocardial images was defined as a summed difference score of ≥4.

RESULTS

MRI showed that the LV end-diastolic volume, LV end-systolic volume, and LV ejection fraction (LVEF) remained unchanged during vasodilator stress in all patients (n=52) as well as in the patients with CFR of <2 (n=27), stress MBF of <1.3 ml/g/min (n=28), abnormal myocardial perfusion (n=30), and more than one diseased vessel (n=46). In only four patients, the LVEF measured by MRI decreased by >5% during vasodilator stress. In these four patients, CFR was lower (1.57 ± 0.12 versus 2.18 ± 0.86, p<0.01) and the number of diseased vessels was higher (2.75 ± 0.50 versus 1.48 ± 0.92, p<0.01) than in patients without post-stress LV dysfunction.

CONCLUSION

The LV volume and systolic function evaluated by cardiac MRI remained unchanged during vasodilator stress; however, LV dysfunction during vasodilator stress may occur in patients with severe CAD.

Impact of chronic total occlusion in non-culprit vessels on long-term survival of patients with acute myocardial infarction

Background

Around 10% of patients with acute myocardial infarction (AMI) have chronic total occlusion (CTO) in non-infarct-related vessels, and they are known to be associated with higher mortality in acute phase. However, its impact on long-term prognosis after discharge remains unclear.

Purpose

The purpose of this study was to investigate the influence of presenting CTO lesion on long-term prognosis in patients with AMI.

Method

Consecutive 552 patients with AMI (male 78.3%, age 68±13 years), who had been discharged alive from our hospital, were analyzed. We divided the patients into two groups based on whether they had CTO lesion in a non-infarct-related artery or not: CTO + (n=49) and CTO - (n=503).

Results

Kaplan-Meier analysis (mean follow-up 1,424 days) revealed that all-cause mortality was significantly higher in CTO + group than in CTO - group (Figure, P&lt;0.001). Cox hazard ratio was 2.740, indicating a higher risk of all-cause death in the CTO + group (95% CI 1.606–4.651, P&lt;0.001).

Conclusion

Concurrent coronary CTO lesions in non-culprit arteries were associated with increased long-term mortality in patients with AMI.

Figure 1

Funding Acknowledgement

Type of funding source: None

Relationship between effects of riociguat and levels of methemoglobin in patients with chronic thromboembolic pulmonary hypertension

Background

Soluble guanyl cyclase (sGC) is a receptor for nitric oxide (NO) and plays an important role in vascular tonus. sGC stimulant is a therapeutic agent for pulmonary hypertension and an advantage of sGC stimulant over phosphodiesterase (PDE)-5 inhibitors is that sGC stimulant exerts its effect even when NO production is reduced. NO derived from vascular endothelial cells is immediately absorbed by hemoglobin (Hb), which leads to the production of methemoglobin (Met-Hb) when oxidized. Previous report has shown that the therapeutic effect of PDE-5 inhibitors was associated with levels of Met-Hb.

Purpose

In this study, we examined the relationship between the effect of riociguat and levels of Met-Hb in patients with chronic thromboembolic pulmonary hypertension (CTEPH).

Methods

The study population comprised 18 patients with CTEPH. Mean pulmonary artery pressure (mPAP) and pulmonary vascular resistance (PVR) were assessed before and after administration of riociguat, and changes in mPAP and PVR were defined as ΔmPAP and ΔPVR, respectively. Since the level of Met-Hb was obtained as the percentage of Hb (FMet-Hb), the amount of Met-Hb was calculated by following formula:

Met-Hb (mg/dL) = Hb (g/dL) × FMet-Hb (%) × 10.

Results

The amount of Met-Hb value before administration of riociguat was significantly correlated with the degree of improvement in mPAP and PVR after administration of riocigat (R=−0.502, P&lt;0.05 mPAP; R=−0.481, P&lt;0.05 PVR, respectively) as shown in figures.

Conclusion

Our findings suggest that the level of Met-Hb before treatment may predict the therapeutic effect of sGC stimulants in patients with CTEPH.

Funding Acknowledgement

Type of funding source: None