Diagnosis of Pulmonary Hypertension Using Cardiac Magnetic Resonance Images
Condition: Pulmonary Hypertension
MeSH terms: Hypertension, Pulmonary; Hypertension
Study type: Observational

Summary: 
      In this study, study team aim to i) evaluate the accuracy of 3D IVS curvedness for prediction
      of RV systolic pressure (RVSP), mean pulmonary artery pressure (mPAP) and pulmonary vascular
      resistance (PVR) with RHC; ii) evaluate the usefulness of 3D IVS curvedness for predicting
      the response to vasodilator challenge with RHC, in patients clinically suspected or known to
      have primary PH.
    

Detailed description: 
      1) Pulmonary hypertension Pulmonary hypertension (PH) is manifested as an increase in mean
      pulmonary artery pressure (i.e., mPAP ≥ 25 mmHg) at rest on right heart catheterization (RHC)
      (Badesch 2009). It is a complex and multidisciplinary disorder causing restricted flow
      through the pulmonary arterial circulation due to increased pulmonary vascular resistance
      (PVR). It can be classified into five groups (Simonneau et al 2004): Group I - Idiopathic
      PAH, Familial PAH, and PAH associated with collagen vascular disease et al; Group II - PH
      with left heart disease; Group III - PH associated with lung diseases and/or hypoxemia; Group
      IV - PH due to chronic thrombotic and/or embolic disease; and Group V - miscellaneous causes
      of PH. The prognosis of PH is poor. The National Institutes of Health (NIH) Registry followed
      194 patients with IPAH enrolled at 32 clinical centers from 1981 to 1985 (D'Alonzo et al
      1991). The reported median survival rates of 68%, 48% and 34%. Similar results have been
      reported in Japan, India and Mexico.

      Right heart catheterization (RHC) is the current reference standard for diagnosing PH (Galie
      et al 2009; McLaughlin et al 2009), according to ACCF/AHA expert consensus (McLaughlin et al
      2009) and ESC/ERS guidelines (Galie et al 2009). Three hemodynamic measurements are essential
      from RHC: right ventricular systolic pressure (RVSP), mean pulmonary artery pressure (mPAP)
      and pulmonary vascular resistance (PVR). Further, patients with PH undergo RHC to assess
      clinical response to vasodilator challenge in order to guide therapy. It helps identify
      patients with better prognosis and patients who could potentially benefit from treatment with
      calcium channel blockers. A positive acute response is defined as a reduction of pulmonary
      artery pressure ≥10mmHg and ≤40mmHg. Although RHC plays a pivotal role in PH diagnosis, it is
      invasive and not without its own inherent risks (Hoeper et al 2006). For these reasons,
      development of a noninvasive alternative to RHC for diagnosis of PH is paramount.

      Noninvasive diagnosis of PH and prediction of response to vasodilator challenge is clinically
      needed.

      Several noninvasive methods for diagnosis of PH have been propounded, the most common being
      Doppler echocardiography. While routinely used to estimate pulmonary arterial pressure,
      Doppler measurement of tricuspid regurgitation jet peak velocity has inherent limitations:
      (i) the reliance on the visualization of the tricuspid regurgitant jet which is not always
      detectable, (ii) the fact that peak velocity of the jet may be difficult to measure in the
      presence of severe tricuspid regurgitation, and (iii) the need for adequate acoustic windows
      (Hinderliter et al 2003; Hachulla et al 2005). Furthermore, as recently emphasized in the
      ERS/ESC guideline (Galie et al 2009), estimation of mPAP or PVR must be an integral part of a
      complete cardiac echocardiographic examination.

      It has long been recognized that systolic flattening and abnormal motion of the
      inter-ventricular septum (IVS), from either echocardiography (King et al 1983; Reisner et al
      1994; Ricciardi et al 1999) or cine CMR images (Roeleveld et al 2005; Dellegrottaglie et al
      2007; Alunni et al 2010), are signs of increased pulmonary arterial pressures. However, these
      studies are either qualitative or limited to 2D assessment, relying for analysis on
      subjective selection of the imaging plane and cardiac cycle phase. In the last 10 years,
      despite advances in biomedical engineering and computational approaches, no rigorous studies
      have been undertaken to study the relationship between quantitative 3D IVS shape and PH.

      It is well documented that RV dysfunction and the 6-min walk test (6MWT) are associated with
      increased risk of mortality in PH (van Wolfersen 2007). Study team has recently developed a
      new method for assessment of RV function in terms of area strain, integrating radial,
      circumferential and longitudinal deformation (Zhong et al 2012). Therefore, we will also
      investigate the relationship between RV area strain and exercise capacity in PH.
    

Intervention name(s): 6MWT; Cardiovascular Magnetic Resonance Imaging (CMRI)
Intervention type(s): Other; Other
Intervention description(s): Each patient will also receive 6MWT at cardiovascular rehabilitation and preventive cardiology laboratory. Besides the distance covered in meters or converted measure (such as feet) over 6 minutes, a portable metabolic system is used to measure oxygen uptake during exercise (VO2 testing) for each patient.; MRI uses interaction of the magnetic properties of body tissues with strong magnetic fields to create images; for about 1 hour. Several sets of images are needed. No injection of drug or dye will be used for this procedure.
Observational model: Case-Control
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        30 diagnosed pulmonary hypertension patient will be recruited from primary care clinic and
        outpatient clinics from the National Heart Centre Singapore.

        30 Healthy volunteer control.
      
Keywords: Pulmonary Hypertension; MRI