الفهرس 
INDICATIONS, MODES AND PHYSIOLOGICAL ASPECTS OF PERMANENT PACINGOnly 14 pages are availabe for public view
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Abstract
One of the main objectives of modern cardiac pacing is to optimize, or at least to stabilize, cardiac performance which is dependant on three main parameters: chronotropic function and quality of AV synchrony.
Multiple studies have demonstrated the hemodynamic superiority of AV sequential pacing over ventricular pacing. A property timed atrial systole improves stroke volume through the Frank-Starling mechanism, by providing greater left ventricular end-diastolic fiber stretch, and, consequently, enhanced end-systolic fiber shortening, all of this without an increase in average pulmonary venous pressure.
Pulsed Doppler tissue imaging can be considered as a unique technique of measuring systolic and diastolic velocities of both mitral and tricuspid annulae. While the velocity of motion of the mitral annulus has been repeatedly shown to accurately and reproducibly represent the global left ventricular systolic and diastolic functions.
The aim of this work to study the effects of permanent cardiac pacing; (ventricular demand pacing and dual chamber pacing) on both right and left ventricular functions.
This study included 20 patients who were in need for permanent cardiac pacing for variable indications admitted in the coronary care unit of El Galaa Military Hospital.
All patients were subjected to the following:
1- Medical history analysis and thorough clinical evaluation.
2- Twelve lead surface ECG at time of admission to define the indication for the permanent cardiac pacing.
3- Conventional echodoppler and Tissue Doppler imaging assessment before permanent pacemaker implantation.
4- Implantation of permanent pacemaker (either single chamber or dual chamber according to case indication and the available model of the pacemaker.
5- Follow up studies by echocardiography and tissue Doppler at 3, 6 and 9 months.
Doppler parameters of left and right ventricular diastolic functions: Mitral valve early diastolic velocity (MV Evel), mitral valve early deceleration time (MV EDT), tricuspid valve early diastolic velocity (TV Tvel.), tricuspid valve early deceleration time (TV EDT).
By tissue Doppler imaging velocities and time intervals of the mitral and tricuspid annula TD signals were measured.
The studied patients were divided into two groups were Ten patients (group I) who received VVI pacing and the other ten patients (group II) who received DDD pacing. There were eleven males (55%) and nine females (54%). The mean age of the whole population was 62.9±11.5 years and patients of group I were significantly older than group II 70.00±6.11 versus 55.9±11.52 respectively and the p value 0.003. There was no significant difference between both groups regarding percentage of diabetics or hypertensives in both groups. There was no significant difference between VVI and DDD group regarding RVEDD, RVESD or RVFS. Also by comparing base line measurements of both groups to that at 3, 6, 9 months of follow up in both groups there was no significant differences between all readings in both groups. Despite larger left atrial diameter in VVI group at all measurements but that was not statistically significant. The left atrial diameter has been enlarged after the 6th month of follow up significantly in both groups compared to baseline. LVEDD and LVESD were not significantly different comparing baseline measurements of both groups but changed to be significantly higher starting from the 3rd month of follow up in group I than group II. There was insignificant difference between the two groups in the frequency of MR or TR between the two groups all over the follow up period. There was insignificant difference between both groups in relation to each other or across each group during follow up in comparison to values at baseline regarding MV, TV E velocities or MV EDT. Measures of systolic and early diastolic velocities at lateral site of the mitral annulus during the follow up of permanent pacing patients; there was a significant reduction in the mean value of mitral annular systolic velocity (M Sa Vel.) in patients of both groups during follow up compared to the mean value at the beginning of the study. Also there were statistically lower T Sa vel. In group I than group II during follow up despite insignificant difference at baseline recordings
• VVI pacind worsen LV functions and causes more dilatation in LA diameter than DDD pacing as measured by echocardiography.
• VVI and DDD pacing had effects on incidence of MR and TR during 9 months of follow-up, both increase MR and TR severity but statistically insignificant.
• TDI: the mitral systolic velocity was decreased in both groups but earlier in VVI group at the 3rd month and DDD group at 6 month and the difference between the two groups was observed at 9th month. That means that permanent pacing affects mitral systolic velocities gradually but earlier in VVI group.
• TDI: Tricuspid systolic velocity is affected in both VVI and DDD but earlier in VVI group.
• DDD mode is preferred than VVI mode because of less deterioration of cardiac functions.
• TDI is an emerging cardiac function assessment technique that could predict minimal deterioration of mitral and tricuspid velocities and guide for VVI upgrade to DDD.