Heart rate/blood pressure ratio as predictor of neuromediated syncope.

Background: Predicting the occurrence of syncope in advance during tilt test could be useful to prepare the medical staff in preventing complications connected with this procedure, particularly in patients with no pre-syncopal symptoms. Our objective was to develop a simple algorithm able to predict the onset of neuromediated syncope during the tilt test.

Methods: We analysed the trend in RR interval, blood pressures, the ratio of these two variables and their derivative, as possible predictors of neuromediated syncope during tilt test. We studied 145 patients: 72 tilt test positive (age 7-82 years, 23 male, 49 female) and 73 tilt test negative (age 8-82 years, 36 male, 37 female), coming at our attention for suspected syncope. We evaluated time of prediction, sensitivity, specificity and receiver-operating curves (ROC) of the trends in RR interval, blood pressure, their ratio and the derivative of their ratio, in predicting syncope.

Results: The derivative of the ratio between RR interval and systolic blood pressure (dRR/SBP) was able to predict syncope 44.1 ± 6.6s in advance with a sensitivity of 86.2% and a specificity of 89.1%. Area under the curve of ROC was 0.877 (p<0.001). The method was able to predict syncope in all three forms of neuromediated syncope: cardioinhibitory, mixed and vasodepressor. Similar results were found using the pulse pressure (dRR/PP).

Conclusions: Using dRR/SBP or dRR/PP it is possible to predict the occurrence of syncope in advance during tilt test.