The time-velocity integral (TVI) measurements of pulmonary
venous and transmitral flows
As LV chamber stiffness increases, antegrade
trans-micuspid blood flow and
pulmonary venous return are affected during atrial contraction because
of the increase in chamber pressure. The original invasive study by
Rossvoll O, et al. found that pulmonary venous flow reversal beyond the
duration of the mitral A wave indicated an exaggerated increase in late
left ventricular diastolic pressure. A pulmonary venous systolic
fraction <0.4 indicated a significant increase in ventricular
filling pressures(36). Based on this, Kazunori Okada et al. (37)proposed
to indirectly reflect LV chamber stiffness by velocity-time integral
measurements of pulmonary venous and transmicuspid blood flow. The TVI
measurements of pulmonary venous and transmitral flows refer to the
measurements of the TVI of the backward pulmonary venous (PV) flow
during atrial contraction (IPVA) and the ratio of
IPVA to the PV flow TVI throughout a cardiac cycle
(FPVA) by echocardiography. In addition, the TVI of the
atrial systolic forward transmitral flow (IA) and the
ratio of the IA to the transmitral TVI during a cardiac
cycle (FA) also need to be measured (Figure 2D).
Kazunori Okada et al. reported the
FPVA/FA and IPVA/
IA are well correlated with the LV chamber stiffness (r
= 0.79 and r = 0.81) and LV end-diastolic pressure (r = 0.73 and r =
0.77) in 62 patients who underwent cardiac catheterization. The areas
under the ROC curve to discriminate LVEDP >18mmHg were 0.90
for IPVA/ IA (Optimal cut-off value
0.51, Sensitivity 83%, Specificity 80%, P <0.001)and 0.93
for FPVA/FA(Optimal cut-off value 0.47,
Sensitivity 83%, Specificity 82%, P <0.001).
Unfortunately, only one study has been conducted in the literature on
the exploration and application of TVI, and its accuracy in assessing LV
chamber stiffness remains to be confirmed. In the meanwhile, these
indicators are not applicable to patients with dyssynchrony of atrial
activity caused by synchronized atrial activity due to arrhythmias such
as atrial fibrillation, atrial flutter and complete atrioventricular
block, and left ventricular catheterization and echocardiography cannot
be performed at the same time. In addition, although there was a good
correlation between IPVA/IA and chamber
stiffness, IPVA/IA was angle dependent.
More in-depth studies in different populations with larger samples are
further needed.