Diastolic And Systolic Right Ventricular Dysfunction Precedes Left Ventricular Dysfunction In Patients Paced From Right Ventricular Apex

BACKGROUND Cardiac dysfunction after right ventricular (RV) apical pacing is well known but its extent, time frame of appearance and individual effect on left ventricular (LV), RV systolic and diastolic parameters has not evaluated in a systematic fashion. METHODS Patients with symptomatic bradycardia and ACC-AHA Class I indication for permanent pacemaker implantation (PPI) were implanted a single chamber (VVI) pacemaker. They were followed prospectively by echocardiographic examination which was done at baseline, 1 week, 1 month and 6 months after implantation. Parameters observed were chamber dimensions (M-line), chamber volumes, cardiac output (modified Simpson's method), systolic functions (ejection fraction, pre-ejection period, ejection time and ratio) and diastolic functions( isovolumic relaxation time & deceleration time) of left and right heart. RESULTS Forty eight consecutive patients (mean age 65.6+/-11.8 yrs, 66.7% males, mean EF 61.82+/-10.36%) implanted a VVI pacemaker were enrolled in this study. The first significant change to appear in cardiac function after VVI pacing was in diastolic properties of RV as shown by increase in RV isovolumic relaxation time (IVRT) from 65.89+/-15.93 to 76.58+/-17.00 ms,(p<0.001) at 1week and RV deceleration time (DT) from 133.84+/-38.13 to 153.09+/-31.41 ms, (p=0.02) at 1 month. Increase in RV internal dimension (RVID) from 1.26+/-0.41 to 1.44+/-0.44, (p<0.05) was also noticed at 1 week. The LV diastolic parameters were significantly altered after 1 month with increase in LV-IVRT from 92.36+/-21.47 to 117.24+/-27.21ms, (p<0.001) and increase in LV DT from 147.56+/-31.84 to 189.27+/-28.49ms,(p<0.01). This was followed by LV systolic abnormality which appeared at 6 months with an increase in LVPEP from 100.33+/-14.43 to 118.41+/-21.34ms, (p<0.001) and increase in LVPEP/LVET ratio from 0.34+/-0.46 to 0.44+/-0.10, (p<0.001)]. The reduction in LV EF was manifested at 6 months falling from 61.82+/-10.36% to52.52+/-12.11%, (p<0.05) without any significant change in the resting cardiac output. CONCLUSION The present study shows that dysfunction of right ventricle is the first abnormality that occurs in VVI paced patients, which manifests by 1 week followed by LV dysfunction which starts appearing by 1 month and the diastolic dysfunctions precede the systolic dysfunction in both ventricles.