Pulmonary circulation evaluation before cavopulmonary connections: the cavopulmonary bypass

Patency of cavopulmonary connection studied by single phase electron beam computed tomography

PURPOSE

The shunt patency and anatomic alteration of central PA after cavopulmonary connection was assessed by one phase electron-beam computed tomography (EBCT) METHODS: Thirteen patients that received a bi-directional cavo-pulmonary shunt (BCPS, n = 7) or total cavo-pulmonary connection (TCPC, n = 6) were included. The patency of the shunt and the anatomy of intra-pericardial PA were evaluated by EBCT, and compared by angiography and echocardiography.

RESULTS

EBCT accurately evaluated shunt patency and the anatomy of the intra-pericardial PA, except for the incorrect diagnosis of SVC-PA shunt patency and peripheral pulmonary stenosis in two TCPC patients. Both of these patients had bilateral SVC and received either bilateral BCPS or ligation of the left SVC respectively. The baffle between the IVC and PA was partly opacified through a fenestration of the baffle, but was not opacified in two patients without fenestration.

CONCLUSION

EBCT accurately evaluated shunt patency and the anatomy of central PA, however, the accuracy was limited in two cases with bilateral SVC. The opacification of the intra-atrial baffle was insufficient in TCPC cases. Multi-phase CT angiography may overcome this limitation in this patient subset.

Ventricular energetics after the Fontan operation: contractility-afterload mismatch

OBJECTIVE

Fontan-type operations offer the opportunity to create pulmonary and systemic circulation in series with a single pumping chamber. The effectiveness of such a circulatory pattern determines resting and exercise hemodynamics in these patients. The present study investigated cardiac performance after the Fontan operation by using ventricular-vascular coupling framework analysis.

METHODS

In 12 anesthetized open-chest dogs, Fontan circulation was established by using a cavopulmonary anastomosis. Left ventricular hemodynamic variables were measured by using a combined pressure-volume-conductance catheter. Additionally, aortic flow and pressure were recorded continuously. Ventricular contractility was quantified by using the load-independent slope of the end-systolic pressure-volume relationship. Arterial system properties were quantified by using the end-systolic pressure/stroke volume ratio. The coupling between the left ventricle and arterial system was expressed by using the ratio of end-systolic pressure/stroke volume to slope of the end-systolic pressure-volume relationship. Additionally, external stroke work, total mechanical energy and mechanical efficiency (Mechanical efficiency = Stroke work/Total mechanical energy) were calculated. Impedance spectra were determined by means of Fourier analysis.

RESULTS

During Fontan circulation, the slope of the end-systolic pressure-volume relationship (5.3 +/- 0.6 vs 7.5 +/- 0.6 mm Hg/mL, P <.05) decreased, and the end-systolic pressure-stroke volume relationship (4.2 +/- 0.7 vs 3.3 +/- 0.5 mm Hg/mL, P =.23) increased with parallel increased characteristic impedance. Furthermore, the end-systolic pressure-stroke volume/slope of the end-systolic pressure-volume relationship ratio increased significantly (0.76 +/- 0.04 vs 0.42 +/- 0.03, P <.005). Simultaneously, stroke work (1846 +/- 146 vs 1389 +/- 60 mm Hg/mL, P <.05) and mechanical efficiency (0.82 +/- 0.09 vs 0.56 +/- 0.05, P <.05) were significantly reduced.

CONCLUSIONS

Fontan circulation leads to contractility-afterload mismatch by means of increased impedance caused by additional connection of the pulmonary vascular bed to the systemic vasculature and by means of deterioration of myocardial contractility. The increased ventriculoarterial coupling ratio and reduced mechanical efficiency predict limited cardiac functional reserve after the Fontan operation.

Factors influencing arterial oxygenation early after bidirectional cavopulmonary shunt without additional sources of pulmonary blood flow

OBJECTIVES

Although the arterial oxygen saturation after bidirectional cavopulmonary shunting should theoretically be homogeneous if additional pulmonary flow is obliterated, the arterial oxygen saturation has been found to vary in clinical practice. Knowledge of the preoperative and operative determinants of arterial oxygen saturation early after bidirectional cavopulmonary shunting may lead to a better understanding of this unique physiology.

METHODS

Thirty-five patients who underwent bidirectional cavopulmonary shunting with obliteration of additional pulmonary flow were included in this study. The arterial oxygen saturation was determined at the 5 time points over a 48-hour period. Multivariable regression analysis was used to identify the independent predictors of the arterial oxygen saturation.

RESULTS

No significant interval changes occurred in the arterial oxygen saturation during the 48 hours after bidirectional cavopulmonary shunting, which ranged from 61.6% to 95.6%. There was a significant inverse correlation between the postoperative superior vena cava pressure and the arterial oxygen saturation (P =.003). A low arterial oxygen saturation early after bidirectional cavopulmonary shunting was a predictor of mortality or exclusion from univentricular repair within 24 months (P =.012, odds ratio = 1.14). Of 11 factors identified by univariable analysis, multiple regression analysis indicated that age less than 8 months at the time of shunting (P <.0001) and ventricular volume overload (P =. 002) predicted a lower arterial oxygen saturation after bidirectional cavopulmonary shunting.

CONCLUSIONS

Even without additional sources of pulmonary blood flow, several preoperative factors, including younger age and severe ventricular volume overload, predicted a decrease in the arterial oxygen saturation early after bidirectional cavopulmonary shunting. This, in turn, predicted poor outcome during 2 years of follow-up.