New Information Revealed about Changes in the Cardiac Structure of Children with Obstructive Sleep Apnea
Obstructive sleep apnea (OSA) has long been known as an independent risk factor for cardiovascular disease in adults. Among the documented heart-related problems in adult OSA patients are cardiac dysfunction, nocturnal hypertension, and myocardial and cerebral ischemia.
In pediatric patients, severe OSA can lead to congestive heart failure, but the early pathophysiological changes that link OSA to cardiovascular disease have been poorly understood. A new study yields breakthrough information about the changes in cardiac structure that occur in children with OSA. The study was led by Cincinnati Children's researchers Raouf Amin, MD, of the Division of Pulmonary Medicine, and Steven Daniels, MD, PhD, of the Division of Cardiology.
The authors hypothesized that the increase in systemic and pulmonary resistance that occurs with OSA leads to elevated systemic and pulmonary pressure, causing remodeling and hypertrophy of the ventricles. They recruited children aged 2 to 18 who were referred to the Sleep Disorders Clinic at Cincinnati Children's for evaluation of obstructive breathing during sleep. These patients underwent polysomnography to subdivide them into individuals with OSA and primary snoring (PS), and echocardiography to determine left ventricular (LV) mass, wall thickness and geometry.
The authors found that children with OSA had an increased LV mass index and increased LV relative thickness compared to children with PS, and that these indicators correlated with the severity of the disorder. It was found that 39 percent of patients with OSA had abnormal LV geometry, compared to only 15 percent of children with PS. The LV mass index also correlated negatively with age, suggesting a differential effect of OSA on LV mass in younger patients.
Breakthrough Findings
This study represents a landmark discovery. Whereas previous studies of cardiac changes in patients with OSA focused solely on the structure of the right ventricle, this study confirms that OSA in children can lead to significant structural changes in both sides of the heart. Considering that changes in the left side can lead to more long-term health consequences, the information about LV geometry gleaned from this study will be useful to pediatricians and family physicians as an indicator for cardiac dysfunction related to OSA.
"In the past, everyone has focused on the right ventricle," says Dr. Amin. "No one has looked at the whole heart. Now we know that apnea has an effect on both sides of the heart and we have a documented effect on the structure of the left ventricle."
Clinical Implications
These findings are clinically relevant because previous studies have demonstrated that LV hypertrophy is a risk factor for cardiovascular disease in the context of systemic hypertension in adults. This fact could have serious implications on the future health of children with OSA.
"LV hypertrophy is not a benign condition," says Dr. Daniels. "In adults, LV hypertrophy is associated with an increased risk for cardiovascular disease independently of other factors. So the thought that you have children and adolescents with LV hypertrophy already is a concern."
Dr. Amin adds that LV hypertrophy will be clinically useful as an indicator of cardiovascular risk in pediatric patients with OSA.
"If we have a patient who does have structural changes to the heart associated with sleep apnea, we can say that we need to be more aggressive in treatment because if we wait, the effect on the heart will continue. Now we have an indicator."
The findings from the study clearly accentuate the importance of physicians having young patients in whom they have a clinical suspicion of OSA tested and followed at a proven pediatric sleep disorder center.
A Look Ahead
Drs. Daniels and Amin are continuing to study the connection between sleep apnea and changes in cardiovascular structure. Current research is focusing on baroreceptors, structures that help regulate blood pressure, and what role they may play in LV hypertrophy related to OSA.
"We now know that during an acute apnea event, there are some substantial changes in the cardiovascular system," says Dr. Daniels. "Why should having those changes lead to a chronic problem? That's the question that we're focusing on next."
This study was published in the American Journal of Respiratory and Critical Care Medicine (165[10]: 1395-1399, 2002 May 15) and is supported by the Cincinnati Children's Research Foundation.
