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Background: Progressive right ventricular (RV) dysfunction in pulmonary arterial hypertension (PAH) which is contributed by RV ischemia leads to adverse clinical outcomes. Oxygen-sensitive (OS) cardiovascular magnetic resonance (CMR) has been used to determine the in vivo myocardial oxygenation of the left ventricle (LV). The aims of the present study were therefore to determine the feasibility of RV targeted rest/ stress OS-CMR imaging in PAH patients and healthy volunteers. Methods:We prospectively recruited 20 patients with right heart catheter proven PAH and 9 healthy age matched controls (NC). The CMR examination involved standard functional imaging and OS-CMR imaging. An OS-CMR signal intensity (SI) index (stress/rest SI) was acquired at RV anterior, RV free-wall and RV inferior segments. In the LV, the OS-CMR SI index was acquired globally.Results: Reliable OS SI changes were only obtained from the RV inferior segment. As RV dysfunction in PAH is a global process, hence this segment was used in both patients and NC for further comparison. RV OS-CMR SI change between rest and stress in the NC was 17%±5% (mean ± SD). Nine of 20 (45%) of the PAH patients had a mean OS SI change of less than 9% (or ≥2 SD different from the mean values in NC).Overall, RV OS SI index between the PAH patients and NC was 11%±9% vs. 17%±5% (P=0.045) in the RV inferior segment. In the LV, the global OS-CMR SI index between the PAH patients and NC was 11%±7% vs. 21%±9% (P=0.019). There was a strong correlation between RV Inf OS-CMR SI and LV OS-CMR SI (r=0.86, P<0.001). Conclusions:In this small pilot study, pharmacological induced OS-CMR is a feasible and safe technique to identify and study myocardial oxygenation in the RV of PAH patients.

Background In pulmonary arterial hypertension (PAH), progressive right ventricular (RV) dysfunction is believed to be largely secondary to RV ischaemia. A recent pilot study has demonstrated the feasibility of Oxygen-sensitive (OS) cardiovascular magnetic resonance (CMR) to detect in-vivo RV myocardial oxygenation. The aims of the present study therefore, were to assess the prevalence of RV myocardial ischaemia and relationship with RV myocardial interstitial changes in PAH patients with non-obstructive coronaries, and corelate with functional and haemodynamic parameters. Methods We prospectively recruited 42 patients with right heart catheter (RHC) proven PAH and 11 healthy age matched controls. The CMR examination involved standard functional imaging, OS-CMR imaging and native T1 mapping. An ΔOS-CMR signal intensity (SI) index (stress/rest signal intensity) was acquired at RV anterior, RV free-wall and RV inferior segments. T1 maps were acquired using Shortened Modified Look-Locker Inversion recovery (ShMOLLI) at the inferior RV segment. Results The inferior RV ΔOS-CMR SI index was significantly lower in PAH patients compared with healthy controls (9.5 (– 7.4–42.8) vs 12.5 (9–24.6)%, p = 0.02). The inferior RV ΔOS-CMR SI had a significant correlation to RV inferior wall thickness (r = – 0.7, p < 0.001) and RHC mean pulmonary artery pressure (mPAP) (r = – 0.4, p = 0.02). Compared to healthy controls, patients with PAH had higher native T1 in the inferior RV wall: 1303 (1107–1612) vs 1232 (1159–1288)ms, p = 0.049. In addition, there was a significant difference in the inferior RV T1 values between the idiopathic PAH and systemic sclerosis associated PAH patients: 1242 (1107–1612) vs 1386 (1219–1552)ms, p = 0.007. Conclusion Blunted OS-CMR SI suggests the presence of in-vivo microvascular RV dysfunction in PAH patients. The native T1 in the inferior RV segments is significantly increased in the PAH patients, particularly among the systemic sclerosis associated PAH group.

SHORT REPORTS Assessment of severity of paraquat poisoning Gramoxone (20%/ paraquat) causes death in 700' of patients who take it by mouth. In contrast, Weedol (3%/' paraquat) causes death in

Background In our earlier study on the functional limits of the aneurysmal aortic root we determined the pig root is susceptible to failure at high aortic pressures levels. We established a pig rupture model using cardiopulmonary bypass to determine the most susceptible region of the aortic root under the highest pressures achievable using continuous flow, and what changes occur in these regions on a macroscopic and histological level. This information may help guide clinical management of aortic root and ascending aorta pathology. Methods Five pigs underwent 4D flow MRI imaging pre surgery to determine vasopressor induced wall sheer stress and flow parameters. All pigs were then placed on cardiopulmonary bypass (CPB) via median sternotomy, and maximal aortic root and ascending aorta flows were initiated until rupture or failure, to determine the most susceptible region of the aorta. The heart was explanted and analysed histologically to determine if histological changes mirror the macroscopic observations. Results The magnetic resonance imaging (MRI) aortic flow and wall sheer stress (WSS) increased significantly in all regions of the aorta, and the median maximal pressures obtained during cardiopulmonary bypass was 497mmHg and median maximal flows was 3.96L/m. The area of failure in all experiments was the non-coronary cusp of the aortic valve. Collagen and elastin composition (%) was greatest in the proximal regions of the aorta. Collagen I and III showed greatest content in the inner aortic root and ascending aorta regions. Conclusions This unique porcine model shows that the aortic root is most susceptible to failure at high continuous aortic pressures, supported histologically by different changes in collagen content and subtypes in the aortic root. With further analysis, this information could guide management of the aortic root in disease.

Background: Prognosis in pulmonary arterial hypertension (PAH) is largely dependent on right ventricular (RV) function. However, recent studies have suggested the presence of left ventricular (LV) dysfunction in PAH patients. The potential role of LV ischemia, as a contributor to progressive LV dysfunction, has not been systematically studied in PAH. We aim to assess the presence and extent of LV myocardial ischemia in patients with known PH and without obstructive coronary artery disease (CAD), using oxygen-sensitive (OS) cardiovascular magnetic resonance (CMR) and stress/rest CMR T1 mapping.Methods: We prospectively recruited 28 patients with right heart catheter-proven PH and no significant CAD, 8 patients with known CAD and 11 normal age-matched controls (NC). OS-CMR images were acquired using a T2* sequence and T1 maps were acquired using Shortened Modified Look-Locker Inversion recovery (ShMOLLI) at rest and adenosine-induced stress vasodilatation; ΔOS-CMR signal intensity (SI) index (stress/rest SI) and ΔT1 reactivity (stress-rest/rest T1 mapping) were calculated.Results: Global LV ΔOS SI index was significantly lower in PH patients compared with controls (11.1%±6.7% vs. 20.5%±10.5%, P=0.016), as was ΔT1 reactivity (5.2%±4.5% vs. 8.0%±2.9%, P=0.047). The ischemic segments of CAD patients had comparable ΔOS SI (10.3%±6.4% vs. 11.1%±6.7%, P=0.773) to PH patients, but lower ΔT1 reactivity (1.1%±4.2% vs. 5.2%±4.5%, P=0.036).Conclusions: Decreased OS-CMR SI and T1 reactivity signify the presence of impaired myocardial oxygenation and vasodilatory response in PH patients. Given their unobstructed epicardial coronary arteries, this is likely secondary to coronary microvascular dysfunction (CMD).

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Background Progressive right ventricular (RV) dysfunction is a natural progression of pulmonary arterial hypertension (PAH) which is associated with adverse clinical outcomes. The main contributor to progressive RV dysfunction is RV ischemia. Oxygen-sensitive (OS) cardiovascular magnetic resonance (CMR) has been used to determine the in-vivo myocardial oxygenation of the left ventricle (LV). Purpose The aim of the present study was to (1) Determine the feasibility of RV targeted rest/stress OS-CMR imaging in PAH patients and normal volunteers; (2) To define the presence and extent of RV myocardial ischaemia in patients with known PAH. Methods We prospectively recruited 20 patients with right heart catheter proven PAH and 9 normal (NC), age matched controls with no heart disease. The CMR examination involved standard functional imaging and OS-CMR imaging. OS-CMR images were acquired using a T2* sequence at rest and adenosine-induced stress vasodilatation. The RV was divided into 3 segments - RV anterior, RV free-wall and RV inferior. An OS-CMR signal intensity (SI) index (stress/rest signal intensity) was acquired at RV anterior, RV free-wall and RV inferior segments. Results All the PAH patients tolerated and completed the adenosine induced stress OS-CMR without any complications or adverse effects. In NC, reliable OS signal intensity changes was only obtained from the RV inferior segment. As RV dysfunction in PAH is a global process, hence this segment was used in both patients and NC for further comparison. RV OS-CMR signal intensity change between rest and stress in the normal volunteers was 17±4% (mean ± SD). 9 out of twenty (45%) of the PAH patients had a mean BOLD signal intensity change of less than 9% (or 2SD different from the mean values in normal volunteers). Overall, RV OS SI index between the PAH patients and controls was 11±9% vs 17±5% (p-value = 0.045) in RV inferior segment. Conclusion Pharmacological induced OS-CMR is a feasible and safe technique to identify and study myocardial oxygenation in the RV of PAH patients.