Retrograde coronary perfusion: effects on iatrogenic edema and diastolic properties.

BACKGROUND: The relative merits of antegrade infusion and retrograde infusion of cardioplegic solution in terms of heart weight, myocardial water content, and ventricular diastolic properties are undefined. Accordingly, we compared antegrade and retrograde flow of hemodiluted blood in isolated, hypothermic porcine hearts. METHODS: After cardiectomy, 1 L of cold heparinized blood diluted with lactated Ringer's solution to concentrations ranging from 100% lactated Ringer's to 50% lactated Ringer's and 50% blood was perfused in an antegrade (n = 6) or retrograde (n = 6) fashion at mean pressures of 62 +/- 2 mm Hg (+/- standard error of the mean) and 49 +/- 2 mm Hg, respectively. Heart weight, myocardial water content, and left ventricular pressure-volume relationships were obtained before and after perfusion. RESULTS: In the comparison of measurements before and after perfusion, changes in heart weight (36 +/- 4 g versus 5 +/- 2 g; p < 0.05), myocardial water content (6.9% +/- 1.0% versus 2.5% +/- 0.4%; p < 0.01), and ventricular filling measured by normalized left ventricular volume at 10, 15, and 20 mm Hg were greater in the antegrade group. CONCLUSIONS: In the isolated porcine heart, retrograde flow is distinguished from antegrade flow by less change in heart weight and myocardial water content and no diastolic dysfunction.

Iatrogenic myocardial edema: increased diastolic compliance and time course of resolution in vivo.

BACKGROUND: Perfusion-induced edema reduces diastolic compliance in isolated hearts, but this effect and the time for edema to resolve after blood reperfusion have not been defined in large animals. METHODS: Edema was induced by coronary perfusion with Plegisol (750 mL, 289 mOsm/L) during a 1-minute aortic occlusion in 6 pigs. This was followed by whole blood reperfusion, inotropic support, and circulatory assistance until sinus rhythm and contractile function were restored. A control group (n = 6) was treated similarly, with 1 minute of electrically induced ventricular fibrillation and no coronary perfusion. Recorded data included electrocardiogram, left ventricular pressure and conductance, aortic flow, and two-dimensional echocardiography. Preload reduction by vena caval occlusion was used to define systolic and diastolic properties. Data were recorded at baseline and at 15-minute intervals for 90 minutes after reperfusion. RESULTS: In the edema group, average left ventricular mass (132 +/- 7 [standard error of the mean] versus 106 +/- 4 g) and ventricular stiffness constant (0.15 +/- 0.02 versus 0.05 +/- 0.01) increased after Plegisol versus baseline (p < 0.05), returning to normal after 45 minutes of reperfusion. In controls, mass (118 +/- 6 versus 116 +/- 4 g) and ventricular stiffness (0.06 +/- 0.01 versus 0.05 +/- 0.01) did not change significantly. There was no significant change in systolic function. Myocardial water content at the end of the study was not different for the two groups. CONCLUSIONS: Crystalloid-induced edema and diastolic stiffness resolve after 45 minutes in pigs. This suggests that edema caused solely by cardioplegia during cardiac operations should not cause significant perioperative ventricular dysfunction.

Validation study of a new transit time ultrasonic flow probe for continuous great vessel measurements.

Continuous measurement of cardiac output is important during experimental and clinical cardiac surgery as an indicator of ventricular function. Previous flow probes underestimated flow secondary to position and flow (S-series probes; Transonic Systems, Inc., Ithaca, NY), required frequent calibrations (electromagnetic), and were cumbersome to use. The new A-series probe (ASP) by Transonic Systems, Inc., uses a new X method of ultrasonic illumination insensitive to perturbations in flow. The ASPs were found to be accurate during in vitro studies, but have not been validated in vivo. Six anesthetized pigs were instrumented for right atrium to left atrium bypass, and ASPs were placed on the ascending aorta and pulmonary artery. Baseline measurements included aortic (Ao) and pulmonic flow (P), and thermodilution (Td) cardiac output. Animals then were placed on right heart bypass, and flow was randomly varied from 1 to 6 L/min, and Ao flow was recorded. In addition, ASPs were rotated and their direction reversed. After data collection, the occlusive roller pump (RP) was calibrated using a timed collection method. Calibrated RP flows were plotted versus ASP flows, and regression was applied. There was no difference between mean Ao, P, and Td cardiac outputs at baseline. In addition, changes in position and direction of the probe did not affect measurement of flow. The ASPs showed a highly linear correlation with RP ([r = 0.98, p < 0.01] ASP[L/min] = 0.98 RP-0.032). During laminar flow states, ASPs are accurate and insensitive to position on the great vessels.