The Relationship Between β-Receptor Sensitivity and Nocturnal Blood Pressure and Heart Rate Recovery in Normotensive People

Abstract

This study examined the relationship between nocturnal blood pressure (BP) dipping and chronotropic dose25 (CD25) as an indicator of β-adrenergic receptor functioning in normotensive people. In addition, the authors evaluated the influence of β-receptor functioning on heart rate recovery after exercise. The sample consisted of 41 participants (18 men, 23 women). Ambulatory BP monitoring took place in each patient's home. On a separate occasion, β-adrenergic receptor sensitivity was determined by response to isoproterenol infusion. Heart rate (HR) recovery was defined as the change from peak HR to that measured after 1 and 2 minutes of recovery. Relationships between dipping and CD25 were found such that participants with higher CD25 values had less nocturnal decline in systolic BP, diastolic BP, and mean arterial pressure ( r =–0.445, –0.533, –0.510, respectively; p<0.004, 0.001, 0.001, respectively). Heart rate recovery at 1 and 2 minutes after exercise was 28.8 ±5 and 49.9 ±6 beats/minute, respectively. Participants with higher CD25 values had more heart rate decline during the first 2 minutes of recovery ( r =0.407, p<0.008). In addition, heart rate recovery was inversely related to systolic, diastolic, and mean nocturnal blood pressure dipping ( r =–0.348, –0.432, –0.408, respectively, p<0.028, 0.005, 0.009, respectively). Normotensive people with an abnormal circadian pattern of blood pressure may have desensitized β-adrenergic receptors. This desensitization may contribute to blunted nocturnal blood pressure and increased heart rate recovery as measured at 2 minutes following exercise testing.