Comparison of Left Ventricular Myocardial Blood Flow During Atrial and Ventricular Pacing

Summary

In order to compare left ventricular myocardial blood flow (MBF) during atrial pacing (AP) and ventricular pacing (VP), this experimental study was performed. Twenty house rabbits, weighing 2.5 to 4.0 kg (3.3 ± 0.4) were used. After sinus arrest (SA) was produced, the measurements of regional MBF (hydrogen gas clearance method), cardiac output and the pressure of LV and AO were undertaken. Regional MBF was measured at the area of apex, circumflex (CX) coronary artery, left anterior descending (LAD) artery and interventricular septum, using wire-type platinum electrodes.

As a result, cardiac output was higher by 54.3% during atrial pacing as compared with VP (p < 0.001). Regional MBF at the area of LAD, septum and apex during VP was significantly reduced as compared with AP (p < 0.05) except CX area. However, there was no significant difference between the MBF of AP and SA, VP and SA. The distribution of MBF between 4 areas during SA, AP and VP was uniform, and MBF of CX area was larger than that of septum during AP and VP (p < 0.05). But, there were no significant differences among the another area.

In conclusion, the results from this present investigation indicate an important role of atrial contraction and ventricular normal depolarization in the left cardiac function. Also, it demonstrates that atrial pacing results in an increase in myocardial flow and cardiac output than ventricular pacing.