Explore This IssueApril 2007
-Pell Ann Wardrop, MD
The absolute VPC count paralleled the amount of time spent in a particular sleep stage. A greater AHI was associated with a greater VPC count (r2 = 0.013, p < 0.001) and frequency (r2 = 0.049, p < 0.0001). During the three sleep stages of wake, S2, and REM, patients with mild apnea showed no difference in VPC frequency (n = 74, p = 0.19), whereas those with severe apnea had different VPC frequencies over the three sleep stages (n = 50, p = 0.037). In the severe apnea patients, the VPC frequency was significantly greater in REM than in wake (p = 0.011; statistical significance criterion was p < 0.017).
The researchers also found that there is a prolonged period of low oxygen in the dream or REM stage of sleep as compared with other stages. The oxygen desaturation duration per apnea event was longer in REM than in non-REM sleep. Heart rate turbulence, a recently discovered marker for sudden cardiac death, was found to correlate better with the oxygen saturation duration than with AHI values.
The longer oxygen desaturation duration during REM sleep may be the cause of higher VPC frequency during sleep in patients with severe sleep apnea, as well as the propensity for sudden cardiac death during sleep in these patients. This contrasts strikingly with sudden cardiac death in people without OSAS, who more often die in the few hours after waking up.
On the Front Line
As ENTs, we have an advantage over other specialties involved in sleep medicine, as often our findings from the head and neck exam will prompt us to ask questions about OSAS, even if the patient has not volunteered complaints, said Dr. Wardrop.
I begin an evaluation with a history and physical exam that focuses on the risk factors, symptoms, and physical findings frequently seen in patients with sleep disorders, said Dr. Wardrop. I pay particular attention to BMI [body mass index], increased neck size, retrognathia, nasal obstruction, and the collapsibility of the airway.
Since normal healthy adults can have VPCs, there is no ‘typical’ patient who presents with them, said study author Mari Watanabe, MD, PhD, Research Assistant Professor in the Division of Cardiology at Saint Louis University School of Medicine. However, people who have had myocardial infarctions, other heart disease, or hypertension often have frequent VPCs. In these patients, VPCs are associated with a mortality rate about twice that of patients with no heart disease.