Distal flow determinants in canine myocardium perfused through internal thoracic artery bypass grafts

Intraoperative flow measurements in gastroepiploic grafts using pulsed Doppler

OBJECTIVE

The patency of a pedicled right gastroepiploic artery (RGEA) graft can be compromised by intraoperative twists, kinks or spasms. Therefore, a systematic flow assessment was made in RGEA grafts and was compared with similar measurements made in other types of bypass conduits.

METHODS

Intraoperative pulsed Doppler flowmeter measurements obtained in a series of 556 consecutive patients undergoing at least one coronary bypass grafting onto the right coronary system were studied. Eighty-five RGEA grafts were compared with 1427 bypass grafts implanted in the same group of patients and consisted of the following conduits: 442 left internal mammary (LIMA), 149 right internal mammary (RIMA), 831 greater saphenous vein (GSV) and five inferior epigastric (EPIG) grafts. Sequential grafts were excluded from the analysis.

RESULTS

Flow measurements and Doppler waveforms were abnormal and required graft repositioning, and the addition of a distal graft or intragraft papaverine injection (only in GSVs) in 29 cases (2.0% of all grafts). These graft corrections were necessary in 5.9% RGEAs, 3.4% LIMAs, 2.0% RIMAs, and 0.7% GSVs (P < 0.001). The relative risk for graft correction was eight times higher for RGEAs than for GSVs (P = 0.002). Flow increased from 8 +/- 2 to 54 +/- 5 ml/min (P < 0.0001). Flow data were significantly influenced by the type of run-off bed (P < 0.001), the measurements obtained in grafts implanted onto the right coronary artery and the left anterior descending artery being superior. Flows in RGEAs, however, were comparable with values obtained in other grafts implanted onto the same recipient coronary artery.

CONCLUSIONS

A significantly higher incidence of graft malpositioning caused inadequate flows in RGEAs. However, normal flow values could be restored simply by assigning a better graft orientation under pulsed Doppler flowmeter control. Overall flow capacity of the RGEA did not differ from values obtained in other arterial and venous grafts implanted onto the same recipient arteries.

High-dose isosorbide dinitrate for myocardial revascularization with composite arterial grafts

BACKGROUND

Composite arterial grafting for myocardial revascularization is a surgical technique in which free arterial conduits are proximally attached to an in situ internal mammary artery.

METHODS

Composite arterial grafting was performed in 78 patients with internal mammary artery (n = 24), inferior epigastric artery (n = 21), or radial artery (n = 33) connected to the internal mammary artery. Overall, 254 distal anastomoses were performed (average number, 3.3 per patient), 225 of which were arterial. All patients were treated postoperatively with high-dose isosorbide dinitrate (4 to 20 mg/h for 24 hours).

RESULTS

The in-hospital mortality rate was 2.6% (2 patients). Early recatheterization studies performed 3 weeks (range, 1 to 20 weeks) after operation in 30 patients demonstrated patency rates of 100%, 93%, and 100% for the composite internal mammary artery, inferior epigastric artery, and radial artery groups, respectively. In addition, two inferior epigastric artery conduits had major intraluminal constriction. At a mean follow-up of 20 months (range, 1 to 42 months) all patients are alive, and all but 2 in the inferior epigastric group (97%) are angina free.

CONCLUSIONS

This surgical technique can be safely used. On the basis of our experience, the right internal mammary artery and the radial artery are the most suitable conduits for this procedure. High-dose nitrates given perioperatively prevent spasm and ensure early patency rates.

Fluid therapy with Ringer's solution versus Haemaccel following coronary artery bypass surgery

BACKGROUND

Crystalloid and colloid infusion can be used in volume therapy following heart surgery. In this prospective, randomised study we compared Ringer's solution (group R) to Haemaccel (group H) following coronary artery bypass grafting.

METHODS

A stringent protocol for adjusting the infusion rate was used. Haemodynamic parameters and pulmonary function were evaluated as well as chest tube drainage. The double-indicator dilution method was used to measure total blood volume index (TBVI), intrathoracic blood volume index (ITB-VI) and extravascular lung water index (EVLWI).

RESULTS

Haemodynamic stability was achieved in both groups throughout the study period, as judged from mean arterial pressure, central venous pressure, pulmonary capillary wedge pressure, and cardiac index. However, the total volume infused was significantly higher in group R. TBVI and ITBV were higher in group H, although only significant at 8 h for TBVI. Pulmonary function was similar in both groups. There was no significant difference in EVLWI, pulmonary shunt fraction, and time on mechanical ventilation. Likewise, chest tube drainage was not significantly different in both groups.

CONCLUSION

We conclude that volume therapy with Haemaccel following heart surgery requires less volume and achieves better filling of the circulation compared to Ringer's solution.