THE METHOD OF DISTANCE MEASUREMENT AND TORSO LENGTH INFLUENCES THE RELATIONSHIP OF PULSE WAVE VELOCITY TO CARDIOVASCULAR MORTALITY: PP.31.235

Abstract

Objective: The method of estimating the distance traveled by the pulse wave, used in the calculation of pulse wave velocity (PWV), is not standardized. Our objective was to assess whether different methods of distance measurement influenced the association of PWV to cardiovascular mortality in hemodialysis patients. Design and Methods: 98 chronic hemodialysis patients had their PWV measured using three methods for distance estimation; PWV1: sternal notch–femoral site minus sternal notch–carotid site, PWV2: carotid–femoral site, PWV3: carotid–femoral site minus sternal notch–carotid site. Carotid–femoral distance was used to approximate torso length. Patients were followed for a median of 30 (range 1–51) months and the association of PWV and cardiovascular mortality was assessed using survival analysis before and after stratification for torso length. Results: The three methods resulted in significantly different PWV values (11.2 (3.3), 14.8 (4.2), 12.6 (3.7) m/s, respectively). During follow up 50 patients died (mortality rate 20.3/100 patient years), 32 of cardiovascular causes. In log-rank tests only PWV1 tertiles but not those of PWV2 or PWV3 were significantly related to outcome (p-values 0.017, 0.257, 0.138, respectively). In adjusted Cox proportional hazards regression only PWV1 was related to cardiovascular mortality (HR for 1m/s higher PWV 1.18[1.03–1.35], 1.10[0.99–1.21], 1,13[1.00–1.27], for the three PWVs respectively). In stratified analysis, however, among patients with below median torso length all three PWV values were related to outcome, while in patients with above median torso length neither PWV methods resulted in significant relationship to outcome. Conclusion: PWV calculated using the sternal notch–femoral distance minus sternal notch–carotid distance provides the strongest relationship to cardiovascular mortality. Longer torso weakens the predictive value of PWV, possibly due to more tortuosity of the aorta hence more error introduced when using surface tape measurements.