Energy loss in the left ventricle obtained by vector flow mapping as a new quantitative measure of severity of aortic regurgitation: a combined experimental and clinical study.

AIMS: In aortic regurgitation (AR), energy loss (EL) produced by inefficient turbulent flow may be a burden to the heart predicting decompensation. We attempted to quantify EL in AR induced in an acute dog model and in patients with chronic AR using novel echocardiographic method vector flow mapping (VFM). METHODS AND RESULTS: In 11 anaesthetized open-chest dogs, AR was induced by distorting the aortic valve with a pigtail catheter, in totally 20 cases. Regurgitant fraction was determined using pulsed Doppler echocardiography, <30% considered mild to moderate (Group 1, n = 11) and ≥30% moderate to severe (Group 2, n = 9). The clinical study consisted of 22 patients with various degrees of AR; 11 mild to moderate (Group 1) and 11 moderate to severe (Group 2), and compared with 12 normals. VFM is based on continuity equation applied to colour Doppler and speckle tracking velocities, acquired from apical long-axis image. EL was calculated frame by frame, averaged from three beats. In the dog study, diastolic EL increased significantly with severity of AR (baseline vs. Group 1 vs. Group 2: 3.8 ± 1.6 vs. 13.0 ± 5.0 vs. 22.4 ± 14.0 [J/(m s)], ANOVA P = 0.0001). Similar to dogs, diastolic EL also increased in humans by the severity of AR (control vs. Group 1 vs. Group 2: 2.8 ± 1.5 vs. 14.3 ± 11.5 vs. 18.6 ± 2.3 [J/(m s)], ANOVA P = 0.001). CONCLUSION: VFM provides a promising method to quantify diastolic EL in AR. Diastolic EL increases in AR proportional to its severity. EL may be useful to determine the severity of disease from the aspect of cardiac load.

Interatrial septum pacing decreases atrial dyssynchrony on strain rate imaging compared with right atrial appendage pacing.

BACKGROUND: Interatrial septum pacing (IAS-P) decreases atrial conduction delay compared with right atrial appendage pacing (RAA-P). We evaluate the atrial contraction with strain rate of tissue Doppler imaging (TDI) during sinus activation or with IAS-P or RAA-P. METHODS: Fifty-two patients with permanent pacemaker for sinus node disease were enrolled in the study. Twenty-three subjects were with IAS-P and 29 with RAA-P. The time from end-diastole to peak end-diastolic strain rate was measured and corrected with RR interval on electrocardiogram. It was defined as the time from end-diastole to peak end-diastolic strain rate (TSRc), and the balance between maximum and minimum TSRc at three sites (ΔTSRc) was compared during sinus activation and with pacing rhythm in each group. RESULTS: There were no significant differences observed in general characteristics and standard echocardiographic parameters except the duration of pacing P wave between the two groups. The duration was significantly shorter in the IAS-P group compared with the RAA-P group (95 ± 34 vs 138 ± 41; P = 0.001). TSRc was significantly different between sinus activation and pacing rhythm (36.3 ± 35.7 vs 61.6 ± 36.3; P = 0.003) in the RAA-P group, whereas no significant differences were observed in the IAS-P group (25.4 ± 12.1 vs 27.7 ± 14.7; NS). During the follow-up (mean 2.4 ± 0.7 years), the incidence of paroxysmal atrial fibrillation (AF) conversion to permanent AF was not significantly different between the two groups. CONCLUSIONS: IAS-P decreased the contraction delay on atrial TDI compared to RAA-P; however, it did not contribute to the reduction of AF incidence in the present study.

Regional heterogeneity of left ventricular myocardial work quantified using anatomical M-mode echocardiography.

BACKGROUND: Although assessment of left ventricular (LV) regional work per unit of myocardium (RWM) from the wall stress-area relationship has been proposed using M-mode echocardiography, the applicable region was limited. Anatomical M-mode is a new technique which permits the M-mode cursor to be angled in any direction on digital two-dimensional images. Our objective was to characterize regional heterogeneity of LV myocardial work using anatomical M-mode. METHODS: Sixteen patients were studied: 5 with idiopathic dilated cardiomyopathy (DCM), 4 hypertrophic cardiomyopathy (HCM), and 7 controls. Digital 2-dimensional echocardiographic cineloops were acquired from the mid LV short-axis view simultaneously with high-fidelity LV pressure. Using anatomical M-mode, LV internal diameters and wall thickness (H) were determined to calculate mean wall stress (sigma) at 6 equiangular directions. The volume of region, which was given by area times H, was assumed to be constant throughout one cardiac cycle from the incompressibility of myocardium. Thus, 1/H is proportional to the regional area, and then RWM was determined as an area within the sigma-ln (1/H) loop at each direction (positive values indicated a counterclockwise loop rotation). RESULTS: RWM from controls were heterogeneous with the highest in the lateral segments. The 6-segment average RWM was lower in both patients with DCM and HCM than controls (3.9 +/- 1.7 and 2.1 +/- 0.3 vs. 5.5 +/- 1.4 mJ/cm(3), both p < 0.05). RWM was particularly deteriorated at septal and inferior segments in patients with DCM (2.3 +/- 0.9 and 3.0 +/- 1.5 mJ/cm(3), both p < 0.05 vs. control) and at hypertrophied anterior and anteroseptal segments in patients with HCM (0.4 +/- 0.1 and 0.8 +/- 0.6 mJ/cm(3), both p < 0.01 vs. control). CONCLUSIONS: Anatomical M-mode enabled RWM assessment at all segments including the inferoseptum and lateral regions that had been impossible for analysis, revealing regional heterogeneity. The present method has the potential to provide additional information on myocardial mechanical condition.

Quantitative assessment of short axis wall motion using myocardial strain rate imaging.

Although left ventricular wall motion has been usually assessed with four-point scale (1 = normal; 2 = hypokinesis; 3 = akinesis; 4 = dyskinesis) based on the visual assessment, this method is only qualitative and subjective. Recently, a new echocardiographic system that enables calculation of myocardial strain rate based on tissue Doppler information has been developed. We investigated whether myocardial strain rate could quantify regional myocardial contraction in 17 patients with and without wall motion abnormalities including 6 patients undergoing dobutamine stress echocardiography. Left ventricular short-axis wall motion was assessed with standard two-dimensional echocardiography at basal, mid-ventricular, and apical levels. The same levels were imaged with tissue Doppler method to determine regional myocardial strain rate. Sixty-four segments were judged normokinesis, 53 segments hypokinesis, and 18 segments akinesis at rest; 16 segments were judged normokinesis and 6 segments hypokinesis at stress. No segments characterized dyskinesis. Strain rates of normokinetic, hypokinetic, and akinetic wall segments at rest were significantly different each other (-2.0 +/- 0.6 for normokinesis,-0.6 +/- 0.5 for hypokinesis,P < 0.0001 vs. normokinesis, and-0.008 +/- 0.3 for akinesis, P < 0.0001 vs. normokinesis and hypokinesis). Further, strain rates well reflected the change in wall motion induced by dobutamine challenge: strain rates in the 15 segments revealing augmented wall motion changed from -2.0 +/- 0.7 to -4.7 +/- 1.7 (1/sec) (P < 0.0001) and those in the 7 segments revealing deteriorated or unchanged wall motion changed from -2.1 +/- 1.0 to -1.7 +/- 0.8 (1/sec) (P < 0.05). In conclusion, strain rate agreed well with assessed wall motion. Strain rate imaging may be a new powerful tool to quantify regional wall contraction.