Heart patients and sleeping position

TAIPEI, TAIWAN. Sleeping on right side reduces the risk of heart attack in patients with coronary artery disease.Research has shown that patients with coronary artery disease (CAD) have depressed vagal modulation and that this in turn increases their risk of acute myocardial infarction (heart attack). Other research has shown that stimulating the vagus nerve has an antiarrhythmic effect and can actually stop ventricular tachycardias. Now researchers at the Veterans General Hospital in Taipei report that heart disease patients who sleep on their right side (right lateral decubitus position) enhance their vagal activity and thereby lessens their risk of having a heart attack during their sleep. The study involved 27 patients with severe CAD who were scheduled for bypass surgery (23 of them had three-vessel disease) and 17 controls with normal coronary arteries as determined by detailed angiograms. The patients and controls were instructed to rest for 20 minutes in three different postions: lying on their back (supine position), lying on their left side (left lateral decubitus position), and finally lying on their right side (right lateral decubitus position). The positions were assumed in random order. The researchers evaluated vagal modulation by measuring heart rate variability (HRV) during the last 15 minutes of the rest period. HRV (total power, high-frequency power, and low-frequency power) was found to be significantly depressed in the CAD patients when compared to the controls. The HRV measurements also showed that resting on the right side significantly increased HRV and lowered sympathetic activity in both patients and controls. In addition, when patients changed from other positions to the right lateral decubitus position their relative increase in vagal modulation was significantly higher than the changes observed in the controls. The researchers recommend that CAD patients be advised to sleep on their right side.
Kuo, Cheng-Deng and Chen, Gau-Yang. Comparison of three recumbent positions on vagal and sympathetic modulation using spectral heart rate variability in patients with coronary artery disease. American Journal of Cardiology, Vol. 81, February 15, 1998, pp. 392-96