Validation of isovolumic relaxation flow propagation velocity as an index of ventricular relaxation

Intraventricular Isovolumic Relaxation Flow Patterns Studied by Using Vector Flow Mapping

AIMS

The purpose of this study was to characterize isovolumic relaxation flow (IRF) in the left ventricle (LV) in patients with a wide spectrum of LV dysfunction.

METHODS

Color Doppler flow imaging was performed in 61 patients with coronary artery disease, 29 patients with dilated cardiomyopathy, and 41 healthy controls. Vector flow mapping was used to analyze the Doppler data.

RESULTS

IRF patterns were divided into three types: pattern A, an apically directed flow; pattern B, a bidirectional flow with small scattered vortices; and pattern C, a large vortex persisting throughout the entire isovolumic relaxation (IVR) period. All controls demonstrated an IRF corresponding to pattern A. Of the 90 patients, 42 demonstrated IRF as pattern A, 26 as pattern B, and 22 as pattern C. There were significant differences among the subgroups of patients with different IRF patterns and the control group in LV-ejection fraction, size, wall-motion score index, apical wall-motion score index, systolic and diastolic mitral annular velocities, ratio of the mitral inflow E velocity to early diastolic mitral annular velocity (E/e'), and left atrial diameter (all P < 0.05). In the patient group, a higher wall-motion score index independently predicted the IRF pattern. In patients with severe LV dysfunction, a higher E/e' ratio was the independent predictor of the persistence of a large vortex during the IVR period.

CONCLUSIONS

The IRF pattern is associated with LV function. A large intraventricular vortex persisting during the IVR period should be indicative of increasingly depressed LV function.

Telemetric left ventricular monitoring using wireless telemetry in the rabbit model

Background

Heart failure is a critical condition that affects many people and often results from left ventricular dysfunction. Numerous studies investigating this condition have been performed using various model systems. To do so, investigators must be able to accurately measure myocardial performance in order to determine the degree of left ventricular function. In this model development study, we employ a wireless telemetry system purchased from Data Sciences International to continuously assess left ventricular function in the rabbit model.

Findings

We surgically implanted pressure-sensitive catheters fitted to wireless radio-transmitters into the left ventricle of Dutch-belted rabbits. Following recovery of the animals, we continuously recorded indices of cardiac contractility and ventricular relaxation at baseline for a given time period. The telemetry system allowed us to continuously record baseline left ventricular parameters for the entire recording period. During this time, the animals were unrestrained and fully conscious. The values we recorded are similar to those obtained using other reported methods.

Conclusions

The wireless telemetry system can continuously measure left ventricular pressure, cardiac contractility, and cardiac relaxation in the rabbit model. These results, which were obtained just as baseline levels, substantiate the need for further validation in this model system of left ventricular assessment.

Usefulness of the ratio of transmitral E wave velocity to isovolumic relaxation flow propagation velocity for predicting left ventricular end-diastolic pressure

Transmitral E wave velocity was reported to be positively related to left ventricular (LV) filling pressure and negatively related to LV relaxation constant, and isovolumic relaxation flow propagation velocity (IRFPV) was proven recently to be negatively related to LV relaxation constant and independent of preload alterations. Therefore, the combination index, E/IRFPV, may eliminate the influence of LV relaxation and bring the LV filling pressure into focus. However, it is unknown whether E/IRFPV is a useful index in prediction of LV filling pressure. The aim of this study is to evaluate the correlation between E/IRFPV and LV end-diastolic pressure (LVEDP). Forty-three patients with suspected coronary artery disease who underwent a Doppler echocardiographic study and cardiac catheterization were included. LVEDP was determined by a micromanometer-tipped catheter. In a univariate analysis, LVEDP had a positive correlation with left atrial dimension, LV end-diastolic dimension, LV end-systolic dimension, the ratio of E to E wave propagation velocity (EPV) (r = 0.408, p = 0.007), the ratio of E to early diastolic mitral annular velocity (Ea) (r = 0.439, p = 0.003) and E/IRFPV (r = 0.686, p < 0.001). It had a negative correlation with diastolic blood pressure, E wave deceleration time, LV ejection fraction, EPV, Ea and IRFPV. After stepwise multiple linear regression analysis, only the E/IRFPV was the independent predictor of LVEDP (beta = 0.667, p < 0.001). In conclusion, E/IRFPV is a useful parameter in prediction of LVEDP.