The Echocardiographic Research Of Left Ventricular Volume And Pressure In Different Cardiac Electro-Mechanical Patterns: A Canine Model

Objective: Ventricular activation sequence is an important factor related to cardiac systolic function. Abnormal left ventricular activation sequence often induces abnormal ventricular wall movement, and reduces left ventricular global and regional function. The cardiac pacing patterns that are frequently used in clinical service induce a consequence of disordered atrial activation, asynchrony between atrium and ventricle, and abnormal ventricular activation. To further study the trend of global and regional function and pressure of left ventricle and relationships between them in different cardiac electro-mechanical patterns, the research is proposed to study global and 17 segmental ejection fraction (EF), left ventricular pressure and systolic dyssynchrony index (SDI) and the relationships among them in different LV electro-mechanical patterns using full volume three-dimensional echocardiography for the establishing datebase to optimize cardiac pacing pattern and cardiac function.Method: Nineteen healthy beagle dogs were employed for this study, seventeen of them were female, two of them were male. Body weight 10 to 12 kg. Pressure catheter was inserted under the ultrasound-guidance into left ventricular outflow tract through left common carotid artery. Bi-polar pacing electrode was deployed at right atrial appendage through right internal jugular vein. The chest was opened via left thoracotomy in the fourth or fifth intercostal space. The pericardium was opened and sewn to the chest wall to form a cradle for the cardiac ultrasonic scanning. Bi-polar pacing electrodes were deployed at right ventricular apex (RVA), left ventricular lateral (LVL) wall and left ventricular apex (LVA) respectively. The full volume imaging of left ventricular and pressure curve were acquired at baseline (BASE) and RAA, RVA, LVL and LVA pacing respectively. Left ventricular global and 17 segmental volume at end diastole end systole were analyzed by a delicated 4D Cardio-view TM CAP 1.5 work station of TomTec, left ventricular global and 17 segmental EF and the dispersion of the time to minimal volume of 17 segments (SDI) were calculated. The end-systolic pressure(ESP) and end-diastolic pressure (EDP) were measured through pressure-time curve ,and the average ascending rate of left ventricular pressure (+â–³P/â–³T) during systolic and average descending rate of left ventricular pressure were calculated. All the parameters were compared. The linear co-relationships between them were analyzed.Results: (1) Global EF and EDP during RAA pacing were lower than those at BASE (P<0.05); SDI of left ventricle and ESP during RAA pacing were higher than those at BASE, There were no significant difference of ESV, EDP, +â–³P/â–³T and -â–³P/â–³T between BASE and RAA pacing. (2) Global EF, end-diastolic volume (EDV), ESP, +â–³P/â–³T and -â–³P/â–³T were lower during RVA pacing and LVA pacing than those at BASE; SDI of left ventricle was higher than that at BASE(P<0.05); There was no significant difference of end systolic volume (ESV) and EDP between BASE and RVA and LVA pacing(P>0.05); Global EF, +â–³P/â–³T and -â–³P/â–³T were lower during LVL pacing than those at BASE; SDI of left ventricle was higher than that at BASE(P<0.05); There were no significant differences of ESV, EDV, ESP and ESP between BASE and LVL pacing(P>0.05); (3) Global EF, ESP and +â–³P/â–³T and -â–³P/â–³T during RVA pacing were lower than those during RAA pacing(P<0.05); SDI during RVA pacing was higher than that during RAA pacing(P<0.05); ESP, +â–³P/â–³T and -â–³P/â–³T during LVL and LVA pacing were lower than those during RAA pacing (P<0.05); SDI during LVL and LVA pacing was higher than that during RAA pacing; There were no significant difference of global EF between RAA , LVL and LVA pacing respectively; (4) Global EF during LVL and LVA pacing was higher than that during RVA pacing (P<0.05), SDI of left ventricle during LVL pacing was lower than that during RVA pacing (P<0.05); There was no significant difference of SDI between RVA and LVA pacing; (5) There was no significant difference of global EF, SDI, ESP, +â–³P/â–³T and -â–³P/â–³T between LVA and LVL pacing; (6) Left ventricular segmental systolic function: Segmental EF of anterior and post septum and all apical segments (except lateral wall) during RVA pacing were lower than that during RAA pacing (P<0.05); Segmental EF of lateral and anterior wall during LVL pacing were lower than that during RAA pacing (P<0.05); Segmental EF of anterior wall and anterior septum during LVA pacing were lower than that during RAA pacing (P<0.05). (6) No linear co-relationship was established between the volumetric and left ventricular pressure parameters.Conclusion:(1) The global and minority segmental systolic function of left ventricular during RAA pacing are depressed compared with that of normal sinus rhythm. (2) All the ventricular pacing patterns worsen left ventricular systolic and diastolic function compared with that of RAA pacing. Left ventricular systolic function during LVL pacing is superior to that of RVA pacing. (3) During ventricular pacing, the systolic function at nearby segments of the pacing site is negatively affected. (4) No linear co-relationship is established among the volumetric and left ventricular pressure parameters.