Assessment of Left Ventricular Asynchrony after Permanent Cardiac Pacing by Using Speckle Tracking Echocardiography

Abstract
Background: Echocardiography is important in assessing Left Ventricular (LV) Mechanical Dysynchrony (LVMD) and left ventricular function after permanent pacemaker. At present, Real-Time Three Dimensional Echocardiography (RT3DE) and tissue Doppler imaging (TDI) are the most sensitive and commonly used techniques for the quantification of LVMD. Global longitudinal strain (GLS) and LV dyssynchrony as-sessment enables us to detect early signs of LV dysfunction after cardiac pacing.
Aim of Study: To evaluate LV mechanical dyssynchrony and LV function in different pacing modes after permanent cardiac pacing by using TDI and speckle tracking echocardi-ography and to correlate these changes with other clinical, electrocardiographic and echocardiographic data.
Patients and Methods: Seventy patients were enrolled in this prospective cross sectional observational study, (mean age 60.99±13.77 years, 42 females), in Mansoura Specialized Medical Hospital over a period of 1 year from April 2018 to April 2019. All patients were assessed by thorough history taking, clinical examination, 12 lead surface ECG, echocar-diography, 2D speckle tracking echocardiography STE to assess GLS and tissue Doppler imaging TDI.
Results: Regarding diastolic function by pulsed wave Doppler PWD: There was significant decrease in E/e¢  ratio (p<0.001 *), significant increase in myocardial performance index Tei index (p<0.001 *). Regarding internal dimensions and systolic function: There was significant increase in the following: Left Atrial Dimension (LAD) (p=0.001*), Left Ventricular End Systolic Dimension LVESD (p<0.001*) and Left Ventricular End Diastolic Dimension LVEDD (p<0.001 *) while there was significant decrease in ejection fraction EF (p<0.001 *) and fractional shortening FS (p<0.001 *). Regarding parameters of LV dysynchrony: There was significant increase in the following: Aortic preejection delay APED (p<0.001*), interventricular mechanical delay (p<0.001 *) and septal posterior wall motion delay SPWMD by M mode (p<0.001 *). Regarding parameters assessed by tissue synchronization imaging TSI: There was significant increase in the following: SD-Ts (p=0.001 *) and all segments Max delay (p=0.027*).
Regarding parameters assessed by STE: There was significant decrease in global longitudinal strain GLS (p=0.034*) while there was significant increase in TP-SD by STE (p<0.001*).
Also, there was significant decrease in global longitudinal strain GLS (p<0.001*) and significant increase in TP-SD by STE (p=0.001*) in DDD group. While there was significant decrease in global longitudinal strain GLS (p<0.001 *) and significant increase in TP-SD by STE (p<0.001*) in VVI group.
Conclusion: GLS and 2D STE can help in the detection of subclinical left ventricular dysfunction after permanent pacemaker implantation before appearance of symptoms. Also, cardiac pacing leads to LVMD whatever the pacing mode is which may needs later on upgrading to cardiac resynchronization therapy CRT.