Abstract
BackgroundTo evaluate, with different pacing modes, acute changes in left ventricular systolic function, obtained by continuous cardiac output thermodilution in various subsets of patients undergoing cardiopulmonary bypass surgery. Increments of mean arterial pressure and cardiac output were considered the end point.MethodsFifty cases electively submitted to cardiac surgery were analyzed. Isolated valve surgery 62%, coronary revascularization 30% and 8% mixed disease. Left ventricular ejection fraction was preserved in 50%,36% had moderate depression,(EF 36%-50%) whereas 14% had severe depression (EF < 35%). Left bundle branch block occurred in 18%. Preoperatively 84% were in sinus rhythm and 16% in atrial fibrillation. The different subgroups were analyzed for comparisons. Right atrial-right ventricular and right atrial-left ventricular pacing were employed in sinus rhytm. Biventricular pacing was also used in atrial fibrillation.ResultsRight atrium-right ventricular pacing, decreased significantly mean arterial pressure and cardiac output (2.3%) in the overall population and in the subgroups studied. Right atrium-left ventricle, increased mean arterial pressure and cardiac output in 79% of patients and yielded cardiac output increments of 7.5% (0.40 l/m) in the low ejection fraction subgroup and 7.3% (0.43 l/m) in the left bundle branch block subset. In atrial fibrillation patients, left ventricular and biventricular pacing produced a significant increase in cardiac output 8.5% (0.39 l/min) and 11.6% (0.53 l/min) respectively. The dP/dt max increased significantly with both modes (p = 0.021,p = 0.028).ConclusionRight atrial-right ventricular pacing generated adverse hemodynamic effects. Right atrium-left ventricular pacing produced significant CO improvement particularly in cases with depressed ventricular function and left bundle branch block. The greatest increments were observed with left ventricular or biventricular pacing in atrial fibrillation with depressed ejection fraction.
Highlights
To evaluate, with different pacing modes, acute changes in left ventricular systolic function, obtained by continuous cardiac output thermodilution in various subsets of patients undergoing cardiopulmonary bypass surgery
The analysis of the overall population comparing RALVP and right atrial appendage (RA)-RVP modes with basal values showed a significant increase in cardiac output (CO) and MAP in favour of RA-LVP, close to 80% of patients, whereas RA-right ventricular (RV), significantly decreased both parameters (Table 2)
In the subgroup with preserved Left ventricular ejection fraction (LVEF), RA-LVP pacing produced a significant increase of CO, not of MAP
Summary
With different pacing modes, acute changes in left ventricular systolic function, obtained by continuous cardiac output thermodilution in various subsets of patients undergoing cardiopulmonary bypass surgery. The acute ventricular asynchrony and systolic dysfunction generated during this period, far exceed those seen in the setting of chronic heart failure (CHF) treated by CRT. Placement of RV temporary epicardial electrodes, is a routine procedure during cardiac surgery to treat bradicardia with low cardiac output (CO) or atrio-ventricular block. This pacing site, usually generates an undesirable cardiac effect, due to the PSM created by the initial RV activation [7]. Cannesson et al [8] have shown, that acute RA- RVP after CPB, in the absence of right bundle branch block (RBBB), worsens CO
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