[Ventricular afterload and transmitral Doppler flow profile: effects of the diving test]

The influence of loading conditions on mitral flow velocity profile was studies by pulsed wave Doppler echocardiography in 10 normal subjects during diving test (5 min face exposure to iced water). The cold stimulus increased blood pressure (p less than 0.001), peripheral resistances (p less than 0.001), peak-systolic and end-systolic left ventricular (LV) meridional wall stresses (p less than 0.005). No significant change was found in heart rate. LV end-diastolic volume was unchanged, while LV end-systolic volume increased (p less than 0.005). Consequently, LV fractional shortening decreased (p less than 0.001). Thus, in spite of enhanced LV contractility (assessed by a significant increase in LV end-systolic stress to volume ratio, p less than 0.02) LV pump performance fell, because of prevailing afterload as well as lack of acute recruitment of LV preload reserve (afterload-contractility mismatch). Such an increase in LV afterload was associated with remarkable changes in LV diastolic dynamics: isovolumic relaxation time (IRT) was prolonged (p less than 0.001) and ventricular filling was relatively displaced towards late diastole (peak early to peak atrial velocities ratio, pE/pA: 1.5 +/- 0.3 vs 1.9 +/- 0.3 p less than 0.001; peak atrial filling rate: 326 +/- 47 vs 242 +/- 38 ml/s; p less than 0.001; normalized late diastolic velocity: 0.87 +/- 0.10 vs 0.73 +/- 0.06; p less than 0.01). Also, IRT values significantly correlated with pE/pA values (r = -0.75; p less than 0.001). In conclusion, diving test produced important changes in LV hemodynamics which, in turn, influenced LV relaxation and filling pattern. Our results indicate that operative LV loading conditions should be considered when assessing diastolic function by the analysis of transmitral Doppler flow profile.