Background: Real-time three-dimensional echocardiography (RT3DE) has emerged as a more accurate and effective tool for assessing left ventricular (LV) function, compared to traditional two-dimensional (2D) methods. In this study, we used this new tool to revise the controversial relationship between LV function and intra-dialytic hypotension.
Methods: This study enrolled 29 intra-dialytic hypotensive patients (the IDH group) and 34 controls (the CON group) on regular maintenance haemodialysis. The RT3DE- and 2D-derived ejection fraction (EF), stroke volume index (SVI) and ratio of early transmitral inflow velocity to diastolic early tissue velocity were assessed at pre-dialysis and mid-dialysis. The intravascular volume was assessed by the inferior vena cava collapsibility index.
Results: Pre-dialysis evaluation showed no difference in RT3DE- and 2D-derived parameters between the two groups. At mid-dialysis, the IDH group had a lower 2D EF (54 +/- 9.1 versus 62 +/- 6.8% in the CON group, P < 0.001), RT3DE EF (53 +/- 6 versus 60 +/- 7% in the CON group, P < 0.001) and SVI (24.3 +/- 8 versus 30.6 +/- 12.2 mL in the CON group, P = 0.02). From pre-dialysis to mid-dialysis, the IDH group had greater decrease in the change in 2D EF (-4.8% +/- 12.6% versus 5% +/- 13.7% in the CON group, P = 0.004), RT3DE EF (-11.8 +/- 10.3 versus -3.4 +/- 11.5% in the CON group, P = 0.003) and SVI (-17.3 +/- 18.5 versus -9.2 +/- 19.8% in the CON group, P = 0.004). The calculated cardiac index change also showed a greater decrease in the IDH group (-17.8 +/- 20.2 versus -5.7 +/- 18.5% in the CON group, P = 0.02). No significant difference in the ratio of early transmitral inflow velocity to diastolic early tissue velocity, heart rate, systemic vascular resistance index or inferior vena cava collapsibility index was found between the two groups at the baseline or mid-dialysis. A lack of an increase in heart rate and the systemic vascular resistance index in the IDH group during the hypotensive episodes implies that these patients have autonomic dysfunction. Multivariate analysis showed that the RT3DE EF change of < -9.5% (odds ratio = 6, P = 0.003) and the presence of diabetes (odds ratio = 4.4, P = 0.013) had significant and independent associations with intra-dialytic hypotension.
Conclusions: By adopting RT3DE to assess LV performance, our data demonstrated that an inadequate compensation in the LV systolic function is the main mechanism mediating the occurrence of intra-dialytic hypotension in patients with autonomic dysfunction.