The Effects Of Metoprolol Tartrate On Permanent Heart Pacing Threshold And Endocardial Electrical Signal Amplitude

Objective: To observe the effects of metoprolol tartrate on permanent heart pacing threshold and endocardial electrical signal amplitude. Methods: 57 patients who had been implanted pacemaker one to three days were observed, among them, 43 patients received implanting new pacemaker and 14 patients received replacing pacemaker. Metoprolol tartrate 10mg (weight<60kg) or 15mg(weight≥60kg) was administered intravenously, 5mg was given first, repeated again after 5 minutes. Results: The pacing threshold and the amplitude of P, R wave of cardiograph before injecting and 10,30,90,180 minutes after injecting were measured separately using a pacemaker system analyzer at a constant pulse width (0.45～0.48ms). The atrial pacing threshold of the newly implanted group is 0.63±0.19,0.63±0.18,0.64±0.13,0.62±0.10,0.64±0.12V; the atrial pacing threshold of the replaced group is 0.94±0.23,1.01±0.20,0.99±0.23,0.96±0.21,0.97±0.25V; the ventricle pacing threshold of the newly implanted group is 0.49±0.11,0.49±0.13,0.50±0.09,0.48±0.16,0.48±0.19V; the ventricle pacing threshold of the replaced group is 0.76±0.11,0.78±0.12,0.79±0.12,0.77±0.15,0.79±0.13V; the atrial P wave amplitude of the newly implanted group is 7.34±1.73,7.31±1.80,7.20±1.91,7.46±2.01,7.66±1.86mv; the atrial P wave amplitude of the replaced group is 6.56±1.15,6.10±1.93,6.55±1.38,6.62±1.38,6.94±1.24mv; the ventricle R wave amplitude of the newly implanted group is 10.5Q±3.50,10.05±3.76,10.44±3.12,10.37±3.45,10.51±3.03mv; the ventricle R wave amplitude of the replaced group is 9.13±1.99,8.80±2.02,9.43±2.13,9.28±1.94,9.18±2.03mv. Both the newly implanted group and the replaced group the atrial pacing threshold is greater than the ventrical pacing threshold (p<0.05); and the R wave amplitude is greater than the P wave amplitude (p<0.05). Conclusion: Metoprolol tartrate doesn't affect the atrial, ventricle pacing threshold and P,R wave amplitude of the newly implanted patients (p>0.05). It also doesn't affect any pacing threshold parameter of the patients who had been replaced pacemaker significantly (p>0.05).