Thursday, February 28, 2013

Stress Early In Life Can Affect Heart Function Early

Life stress early on such as that experienced by babies who are sick, appears to have an early impact on heart function, affecting the heart's ability to refill with oxygen-rich blood and relax.
A group of researchers from Georgia Regents University conducted a study using rat pups, separating them from their mothers for a couple hours everyday. Then, an extra stress was added to raise blood pressure.

The researchers saw a noteworthy fall in basic heart function. The rates of relaxation and re-filling stayed low in the separation model, however, reductions remained steady by ages two and six months, as the rats progressed to middle age.

The model as well as the controls had reductions in those functions that generally come naturally with age.

Surprisingly, the power with which the heart released blood stayed consistent with the added stressor, angiotensin II - a strong constrictor of blood vessels. Echocardiography was used to measure heart function.

Dr. Catalina Bazacliu, neonatologist at the Medical College of Georgia and Children's Hospital of Georgia at Georgia Regents University, said:

"We expected the heart's ability to relax and refill to lag behind in our model. We believe these babies may be at increased risk for cardiovascular disease and we are working to understand exactly what puts them at risk."

The authors are presenting their findings today at the Southern Regional Meetings in New Orleans.

The findings also show that the blood pressure of rats that are separated from their mothers rises more frequently in response to angiotensin II, their heart rates also increased.

Generally, a compensatory mechanism pushes the heart rate down a bit when blood pressure increases.

Previous studies have indicated persistent blood vessel changes in the early stress model, such as elevated contraction and decreased relaxation when similarly stressed.

Other longitudinal studies in humans have revealed long-term cardiovascular consequences, like babies born during the Dutch famine of World War II, maturing with elevated risks of:
  • cardiovascular disease
  • diabetes
  • obesity
  • other health related issues
In another related study by Bazacliu, she used a similar animal model showing that babies whose growth was limited in-utero by health issues such as preeclampsia - high blood pressure in mothers during pregnancy - were at an elevated risk for cardiovascular disease as adults.

These observations were seen whether the babies were born at full term or prematurely. Higher pressure during development decreases blood flow from mother to baby; decreased oxygen and nutrition to the baby is an example of environmental stress.

Bazacliu points out that although neonatal intensive care units are designed to save and treat premature babies, they can actually cause more stress. The NICU at the Children's Hospital of Georgia works to reduce the negative effects, such as enacting visiting hours, minimizing noise, and other family targeted techniques.

Bazacliu conclues, "All the procedures we must do, the separation from the mother, the environment, even though the babies need the help, it represents a stress."

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