Geeshath Jayasekera

Non-invasive imaging of global and regional cardiac function in pulmonary hypertension:

Pulmonary hypertension (PH) is a progressive illness characterized by elevated pulmonary artery pressure; however, the main cause of mortality in PH patients is right ventricular (RV) failure. Historically, improving the hemodynamics of pulmonary circulation was the focus of treatment; however, it is now evident that cardiac response to a given level of pulmonary hemodynamic overload is variable but plays an important role in the subsequent prognosis. Non-invasive tests of RV function to determine prognosis and response to treatment in patients with PH is essential. Although the right ventricle is the focus of attention, it is clear that cardiac interaction can cause left ventricular dysfunction, thus biventricular assessment is paramount. There is also focus on the atrial chambers in their contribution to cardiac function in PH. Furthermore, there is evidence of regional dysfunction of the two ventricles in PH, so it would be useful to understand both global and regional components of dysfunction. In order to understand global and regional cardiac function in PH, the most obvious non-invasive imaging techniques are echocardiography and cardiac magnetic resonance imaging (CMRI). Both techniques have their advantages and disadvantages. Echocardiography is widely available, relatively inexpensive, provides information regarding RV function, and can be used to estimate RV pressures. CMRI, although expensive and less accessible, is the gold standard of biventricular functional measurements. The advent of 3D echocardiography and techniques including strain analysis and stress echocardiography have improved the usefulness of echocardiography while new CMRI technology allows the measurement of strain and measuring cardiac function during stress including exercise. In this review, we have analyzed the advantages and disadvantages of the two techniques and discuss pre-existing and novel forms of analysis where echocardiography and CMRI can be used to examine atrial, ventricular, and interventricular function in patients with PH at rest and under stress.

Near infrared spectroscopy for the assessment of peripheral tissue oxygenation in pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is characterised by increased pulmonary vascular resistance and results in increased morbidity and mortality due to right heart failure and a progressive decline in cardiac output [1, 2]. The latter disturbs oxygen delivery to the periphery and may lead to pathological changes in tissue oxygenation. The balance between global oxygen supply and demand is reflected in mixed venous oxygen saturation (SvO2), an index that is generally reduced in patients with PAH [3]. SvO2 at baseline is one of the strongest predictors of survival in PAH [4–6]; this is also true for changes in SvO2 during follow-up [5]. Cut-off values of 60% [7] and 65% [5] have been used to distinguish between prognostic groups suggesting that these may be suitable treatment goals. SvO2 is measured invasively in the pulmonary artery, where venous blood mixes after circulating through the superior and inferior vena cava, coronary sinuses and the right-heart chambers. Near infrared spectroscopy offers a qualitative, noninvasive indication of mixed venous oxygen saturation in PAH http://ow.ly/TSSx30231YO

Dynamic near-infrared spectroscopy assessment as an important tool to explore pulmonary arterial hypertension pathophysiology

We thank S. Dimopoulos and co-workers for their particular interest in our study [1] and their contributions to this issue. The peripheral muscle hypothesis in pulmonary arterial hypertension (PAH) [2] is certainly of great and growing interest due to the potential of muscle function as a target for meaningful intervention. Accordingly, our study explored the value of quadriceps muscle oxygenation profiles in patients with PAH by means of near-infrared spectroscopy (NIRS) [1]. The satisfactory correlation between vastus lateralis muscle tissue oxygenation index (StO2) and mixed venous oxygen saturation (SvO2) both at rest and during exercise support the use of NIRS in the noninvasive investigation of patients with PAH. Importantly, they suggest that skeletal muscle oxygenation profiles reflect the pathophysiology of PAH. Near-infrared spectroscopy offers a qualitative, noninvasive indication of mixed venous oxygen saturation in PAH http://ow.ly/MctV306eEYC

Short-Term Hemodynamic Effects of Apelin in Patients With Pulmonary Arterial Hypertension

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Social deprivation and prognosis in Scottish patients with pulmonary arterial hypertension

Several demographic and clinical factors have prognostic significance in idiopathic pulmonary arterial hypertension (IPAH). Studies in China and the USA have suggested an association between low socioeconomic status and reduced survival. The impact of social deprivation on IPAH survival in the UK is not known. 280 patients with IPAH and hereditary PAH (HPAH) attending the Scottish Pulmonary Vascular Unit (Glasgow, UK) were assigned to social deprivation quintiles using the Scottish Index of Multiple Deprivation database. The association between survival and social deprivation quintile was assessed using Cox proportional hazards regression analysis. The distribution of IPAH/HPAH patients was more socially deprived than would be expected based on Scottish citizenry as a whole (Chi-squared 16.16, p=0.003), suggesting referral and access to care is not impeded by socioeconomic status. Univariate analysis demonstrated no significant association between social deprivation and survival (p=0.81), and this association failed to reach significance with inclusion of time, sex and age as covariates in the model (p=0.23). There were no statistically significant correlations between social deprivation and baseline clinical variables of prognostic importance except for age, sex and quality of life. Social deprivation is not a significant referral barrier or prognostic factor for IPAH and HPAH in Scotland. Social deprivation is not a significant referral barrier or prognostic factor for IPAH and HPAH in Scotland http://ow.ly/N7aL30gE4ui

Validation of impedance cardiography in pulmonary arterial hypertension

Non‐invasive methods of measuring cardiac output are highly desirable in pulmonary arterial hypertension (PAH). We therefore sought to validate impedance cardiography (ICG) against thermodilution (TD) and cardiac magnetic resonance (CMR) in the measurement of cardiac output in patients under investigation for PAH.

Dobutamine stress MRI in pulmonary hypertension: relationships between stress pulmonary artery relative area change, RV performance, and 10-year survival.

In pulmonary hypertension (PH), right ventricular (RV) performance determines survival. Pulmonary artery (PA) stiffening is an important biomechanical event in PH and also predicts survival based on the PA relative area change (RAC) measured at rest using magnetic resonance imaging (MRI). In this exploratory study, we sought to generate novel hypotheses regarding the influence of stress RAC on PH prognosis and the interaction between PA stiffening, RV performance and survival. Fifteen PH patients underwent dobutamine stress-MRI (ds-MRI) and right heart catheterization. RACREST, RACSTRESS, and ΔRAC (RAC STRESS – RAC REST) were correlated against resting invasive hemodynamics and ds-MRI data regarding RV performance and RV-PA coupling efficiency (n’vv [RV stroke volume/RV end-systolic volume]). The impact of RAC, RV data, and n’vv on ten-year survival were determined using Kaplan–Meier analysis. PH patients with a low ΔRAC (<−2.6%) had a worse long-term survival (log-rank P = 0.045, HR for death = 4.46 [95% CI = 1.08–24.5]) than those with ΔRAC ≥ −2.6%. Given the small sample, these data should be interpreted with caution; however, low ΔRAC was associated with an increase in stress diastolic PA area indicating proximal PA stiffening. Associations of borderline significance were observed between low RACSTRESS and low n’vvSTRESS, Δη’VV, and ΔRVEF. Further studies are required to validate the potential prognostic impact of ΔRAC and the biomechanics potentially connecting low ΔRAC to shorter survival. Such studies may facilitate development of novel PH therapies targeted to the proximal PA.

Advanced Imaging in Pulmonary Hypertension

Pulmonary hypertension is a pathophysiological state defined as mean pulmonary artery pressure ≥ 25 mmHg at rest determined by right heart catheterization. Various non-invasive imaging modalities have been used to not only establish a tentative diagnosis of pulmonary hypertension but to assess its severity, to identify underlying etiology, to monitor disease progression and response to treatment. Continuous wave Doppler measurements of peak velocity of the tricuspid regurgitant jet is used to determine systolic pulmonary artery pressure non invasively but has various shortcomings when describing the complex right ventricle. Chest radiography may give the first clue to the presence of pulmonary hypertension with information about the cardiac size and pulmonary vasculature. The role of ventilation-perfusion scintigraphy is in the highly sensitive detection of pulmonary embolism which may indicate chronic thromboembolic pulmonary hypertension. Various features of pulmonary hypertension in the main and peripheral pulmonary arteries as well as the lung parenchyma are well visualised by computed tomography. Measures of right ventricular function have been shown to be prognostic in pulmonary hypertension and cardiac magnetic resonance imaging provides accurate information regarding biventricular mass, volume and function. New advances in imaging techniques such as Positron Emission Tomography will give us greater insight into the basic pathobiology of pulmonary vascular remodeling and RV dysfunction.

Right Ventricular free wall myocardial tissue characterisation by systolic Cardiac Magnetic Resonance T1 mapping in pulmonary hypertension

Background Pulmonary hypertension is a rare progressive disorder characterised by elevated pulmonary artery pressure leading to right ventricular (RV) failure and death. Cardiac MR (CMR) derived right and left ventricular functional variables have shown to be prognostic in pulmonary hypertension. Native T1 mapping is a CMR technique of myocardial tissue characterisation without the need for a reference area or contrast administration. T1 mapping of the RV free wall has shown to have poor inter-observer reproducibility due to the relatively thin RV myocardium. An alternative is to acquire T1 maps in systole when the RV myocardium is thicker. We investigated whether native T1 values in systole relate to invasive pressure measurements and markers of RV dysfunction in patients with pre-capillary pulmonary hypertension (PH).