Acute cardiovascular effects of the Wenchuan earthquake: ambulatory blood pressure monitoring of hypertensive patients

An increased incidence of cardiovascular events and sudden death occurs after an earthquake. However, the mechanism underlying this is not clear. Previous studies attributed this phenomenon to earthquake-induced elevation of sympathetic activity. This study investigated the acute cardiovascular effects of the Wenchuan earthquake on hypertensive or suspected hypertensive patients. We studied the role of earthquake-induced changes in blood pressure and heart rate in the occurrence of post-earthquake cardiovascular events. This study included 11 patients who were undergoing ambulatory blood pressure monitoring when the Wenchuan earthquake occurred. Trends in blood pressure and heart rate were analyzed, and blood pressure variability (BPV) data were obtained. The mean post-earthquake blood pressure rose rapidly from 125.8±17.3/72.1±11.9 to 150.5±20.3/98±10.6 mm Hg (average time of first measurement was 13.8±6.3 min after the first tremor), and blood pressure remained high until 6 h after the earthquake. Nighttime blood pressure declined to the mean pre-earthquake daytime levels. The mean daytime blood pressure after the earthquake was greater than the pre-earthquake daytime mean (systolic blood pressure: 138.9±14.6 vs. 129.5±13.6 mm Hg, P=0.009; diastolic blood pressure (DBP): 81.8±13.1 vs. 76.9±11.9 mm Hg, P=0.011). Pre- and post-earthquake BPV differed among individuals, but circadian variation was absent in all cases and nightly decreases were less than 10%. These data strongly suggest that significant post-earthquake elevation of blood pressure and abnormal circadian variation of blood pressure are related to the occurrence of post-earthquake cardiovascular events.