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Objective:Use the Doppler and strain rate imaging to evaluate the systolic and diastolic function of the whole and regional ventricular myocardial in congestive heart failure dog models induced by rapid ventricular pacing, and in order to provide more mature and sound methods and parameters to assess the clinical tachyarrhythmia left heart function.Methods:The study group consisted of 13 healthy mongrel dogs with weighting 30-40 kg. Intra-abdominal anesthesia and conventional mechanical ventilation under the guidance of a large X-ray machine, endocardial pacing electrode was inserted through the external jugular into the vein right ventricular and connected to the pacemaker with electrodes implated in the neck subcutaeous. The all of dogs received rapid right ventricular pacing 4 weeks at the rate of 230 beats per minute. A color Doppler ultrasonic system (GE vivid 7.0) was used with an Echopac workstation available for TVI and SRI quantitation analysis. Echocardiographic study (conventional two-dimensional and color Doppler ultrasound) was performed before operation and 4 weeks after cessation of rapid pacing, and the imaging and datas were stored in the on-board hardware system. The systolic and diastolic diameters of the left ventricle (LVDs, LVDd), stroke volume (SV), ejection fraction (EF), diastolic flow velocity E and A wave, E/A, and E wave deceleration time (EDT) were measured. The peak systolic velocities were measured by Doppler quantitative tissue velocity image at 4 mitral ring sites (LV septum, LV lateral wall, LV inferior wall, LV anterior wall). At SRI condition, analysis was performed in basal and mid of septal and lateral walls in the apical 4-chamber view, in basal and mid of inferior and anterior walls in the apical 2-chamber view. All the walls SRI and SR curves were obtained, and the peak strain rate in every cardiac cycle, such as peak systolic strain(PSS), and peak systolic strain rate(SRs),peak diastolic strain(PDS) were recorded.Result:1. Clinical manifestation After fast pacing of 2 weeks, all dogs appeared decreased activity, loss of appetite, exertional breathlessness; after 3 weeks, all experimental animals were shortness of breath at rest, became intensified after activities, while they appeared obvious abdominal distention, decreased urine output; after 4 weeks, these dogs have been extremely weak.2. General indicators After 4 weeks, Compared with prior pacing, the following parameters increased significantly (p<0.01):the LVDd 41.2±2.8mm vs 32.5±2.4mm, LVEDV 73.5±18.1ml vs 46.7±9.9ml, LVESV 46.8±18.7ml vs 21.6±4.0ml, Tei index 1.02±0.23 vs 0.56±0.19. While LVEF of CHF dogs decreased significantly (36.0±9.1%vs 56.4±5.3%, p<0.01).3. After 4 weeks, Compared with prior pacing, the peak systolic velocities at 4 mitral ring sites decreased significantly (p<0.01, or p<0.05): LV septum (5.8±1.5 cm/s vs 9.6±2.4 cm/s), LV lateral wall (7.9±1.9 cm/s vs 12.7±2.1 cm/s), LV inferior wall (6.5±1.2 cm/s vs 8.9±2.1 cm/s), LV anterior wall (7.1±2.2 cm/s vs 13.5±3.7 cm/s).4. After 4 weeks, Compared with prior pacing, the PSS in basal and mid of LV walls (LV septum, LV lateral wall, LV inferior wall, LV anterior wall) decreased significantly (p<0.01). While, the SRs in the same sites all decreased significantly (p<0.01).For example, the PSS in basal of LV walls decreased significantly (p<0.01):LV septum (5.7±5.2% vs 15.3±2.4%), LV lateral wall (7.3±1.2% vs 15.8±1.6%), LV inferior wall (4.9±3.8% vs 13.7±1.6%), LV anterior wall (6.6±0.6% vs 15.5±1.9%).While the gradient of the PSS among the basal and mid of LV walls all disappeared (p>0.05):LV septum (5.7±5.2% vs 7.6±1.3%), LV lateral wall (7.3±1.1% vs 7.1±1.8%), LV inferior wall (4.9±3.8% vs 7.2±1.4%), LV anterior wall (6.6±0.6% vs 6.7±1.1%). The gradient of the SRs among the basal and mid of LV walls disappeared(p>0.05):LV septum (1.0±0.4S-1 vs 1.2±0.5S-1), LV lateral wall (1.3±0.5S-1 vs 1.0±0.5S-1), LV inferior wall (1.0±0.3S-1 vs 0.8±0.2S-1), LV anterior wall (1.4±0.4S-1 vs 1.1±0.4S-1).5. Compared with prior pacing, peak velocities of E and A waves, E/A and EDT showed no difference (p>0.05). However, the PDS in basal and mid of LV walls (LV septum, LV lateral wall, LV inferior wall, LV anterior wall) decreased significantly (p<0.01).For example, the PDS in basal of LV walls decreased significantly (p<0.01):LV septum (7.1±1.2% vs 15.6±2.7%), LV lateral wall (7.5±1.1% vs 14.9±1.7%), LV inferior wall (6.6±1.5% vs 13.6±1.8%), LV anterior wall (6.5±1.0% vs 15.5±2.3%).While the gradient of the PDS among the basal and mid of LV walls all disappeared(p>0.05):LV septum (7.1±1.2% vs 7.0±1.5%), LV lateral wall (7.5±1.1% vs 6.9±1.8%), LV inferior wall (6.6±1.5% vs 6.4±0.8%), LV anterior wall (6.5±1.0% vs 6.6±1.0%).Conclusion:After rapid ventricular pacing, congestive heart failure occurred in these experimental dogs, not only did the whole and regional myocardial systolic function decreased significantly, but also did to some extent the ventricle diastolic function changed. This study provided for reference experimental datas, which can assess the impact of tachyarr-hythmias on the the ventricular function.
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