Central Blood Pressure
Condition: Hypertension
MeSH terms: Hypertension
Study type: Observational

Summary: 
      The aim of the study is to check standard screening blood pressure in the arm and central
      blood pressure, the blood pressure at the heart in pregnant women. The standard brachial
      pressure is routinely monitored throughout pregnancy, however it is not sensitive enough to
      distinguish preeclampsia from other types of hypertension or to predict preeclampsia in those
      at risk. Central aortic pressure monitoring has become a valuable clinical tool and
      preliminary studies suggest that measuring of central blood pressure may be better predictor
      of preeclampsia. It is non invasive and doesn't require undressing. It involves using a
      standard blood pressure cuff placed around the thigh, checking carotid pulse and pressure
      with an ultrasound and taking measurements of the person neck to torso. With this knowledge
      it will be a useful screening tool to identify these patients at higher risk and hopefully
      lead to closer monitoring, earlier treatment and reduced morbidity and mortality
    

Detailed description: 
      When blood pressure is measured conventionally over the brachial artery it is assumed that
      these measurements accurately reflect pressures in the central circulation. However, central
      aortic pressure is the blood pressure at the root of aorta and are determined not only by
      cardiac output and peripheral vascular resistance, but by the stiffness of conduit arteries
      and the timing and magnitude of pressure wave reflection.

      Studies have shown the importance of central aortic pressure and its implications in
      assessing the efficacy of antihypertensive treatment with respect to cardiovascular risk
      factors. In the CAFE Study the traditional method of measuring blood pressure in the arms has
      been shown to underestimate the efficacy of drugs such as amlodipine and overestimate the
      efficacy of those like atenolol (4). This clinical trial demonstrated that different
      medications for lowering blood pressure have different effects on the central aortic pressure
      and blood flow characteristics, despite producing similar brachial blood pressure readings.
      They also were able to show that central aortic pressures are a better independent predictor
      of cardiovascular and renal outcome. The Strong Heart Study went further to depict how
      central pressure are more predictive of the load imposed on the coronary and cerebral
      arteries and thereby bear a stronger relationship to vascular damage and prognosis.

      Hypertensive disorders of pregnancy, in particular, preeclampsia, are a leading cause of
      maternal and neonatal morbidity and mortality. In the United States and the United Kingdom,
      approximately 5% of pregnancies are complicated by preeclampsia, and of these patients, 1-2%
      progress to eclampsia. It is estimated that these rates are higher in developing countries.
      An estimated 50,000 women die annually from preeclampsia worldwide. The presence of
      hypertension during pregnancy is also associated with a two-fold increase in the risk of
      gestational diabetes mellitus. In addition, a history of preeclampsia increases a women's
      subsequent risk of vascular disease, including hypertension, ischemic heart disease,
      myocardial infarction and stroke. The increased risk of complications is not limited to the
      mother; babies of women with hypertensive disorders during pregnancy are more likely to
      suffer adverse outcomes than those of women without hypertension. A large cross-sectional
      study observing more than 250,000 women and their infants showed that women with gestational
      hypertension were at a 30% greater risk of death or major morbidity, and women with
      pre-eclampsia had a 400% increased risk, compared to women without hypertension. Although
      preeclampsia is not preventable, early diagnosis, careful monitoring and aggressive treatment
      is crucial in preventing mortality.

      The brachial pressure is routinely monitored throughout pregnancy, however it is not
      sensitive enough to distinguish preeclampsia from other types of hypertension or to predict
      preeclampsia in those at risk. Central aortic pressure monitoring has become a valuable
      clinical tool outside of pregnancy, particular in assessment of patient's hypertension, renal
      disease and diabetes. Preliminary studies suggest that measuring of central blood pressure
      may be predictive preeclampsia. In normal pregnancy aortic stiffness has been shown to vary
      throughout the pregnancy, reaching its lowest point in second trimester and rising again in
      the third trimester. A number of studies have investigated the change in pulse wave indices
      in the third trimester across the spectrum of hypertensive disorders. Central pressures,
      along with Augmentation pressure were found to be significantly higher in gestational
      hypertension and preeclampsia compared to normal pregnancy. In addition, Aortic augmentation
      pressure and pulse wave velocity has been shown to vary between preeclampsia, gestational
      hypertension, and normal pregnancy. The ability to accurately identify women at risk for
      preeclampsia would have significant clinical benefits. The ability to distinguish between
      hypertensive disorders and identify those women who have increased risk of preeclampsia can
      lead to better management of hypertensive disorders during pregnancy and therefore better
      outcomes for both mother and child. The aim of our study is to examine if early evaluation of
      central blood pressure and arterial stiffness (pulse wave analysis) can be a predictor of
      gestational hypertension/preeclampsia.
    

Intervention name(s): central blood pressure
Intervention type(s): Procedure
Intervention description(s): SphygmoCor XCEL will be used to measure both standard blood pressure in the arm and central pressure, the blood pressure at the heart.
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Pregnant women > or equal to 14 year old to 60 years old