Clinical effects of different protamine doses after cardiopulmonary bypass

The optimal dose of protamine needed to reverse the anticoagulant effect of heparin after cardiopulmonary bypass is still not known. In this retrospective cohort study, we investigated 3 different dose regimes in 300 patients undergoing coronary artery bypass grafting. Group A patients (n = 100) were given protamine in the ratio of 1.3 mg to 1 mg heparin, group B patients (n = 100) were given 0.75 mg protamine to 1 mg heparin, and group C patients (n = 100) were given protamine in fractionated doses of 1 mg + 0.15 mg + 0.15 mg to 1 mg heparin. The groups were comparable in all major clinical and operative variables. The heparin dose was almost identical in the groups. The rate of red cell transfusion was significantly higher in group B than in the other groups. A similar but nonsignificant trend was observed in the incidence of resternotomy for postoperative bleeding, mediastinal drainage, and postoperative hemoglobin loss. The study demonstrates that a single bolus dose of 1.3 mg protamine to 1 mg heparin is safe and efficient for neutralizing heparin after cardiopulmonary bypass.     

Evaluation of bivariate correlation ratio similarity metric for rigid registration of US/MR images of the liver

Objective  Radio frequency ablation (RFA) can be used to treat liver cancer minimally invasively by depositing energy from the RF probe placed in the center of the tumor. The procedure relies on pre-operative imaging (typically MRI or CT) for the interventional planning and ultrasound (US) for intra-operative guidance during needle insertion. Visual presentation of co-registered pre- and intra-operative images would help to improve the navigation during the needle positioning phase. Methods  In the present study, we compared six registration methods using different similarity metrics: two versions of the correlation ratio, bivariate correlation ratio, and conventional normalized mutual information and correlation coefficient. The accuracy, robustness and speed were assessed by computing rigid registrations between eight pairs of the MR and freehand 3D US datasets. Results  The correlation ratio computed on the MR-gradient-norm and US images outperformed other similarity metrics in terms of robustness (40–82%) and demonstrated average accuracy (0.32°, 0.69 mm) which is clinically acceptable for the RFA of liver cancer. Conclusions  We observed that the performance of all similarity metrics is largely dependent on the quality of the US images, sufficient field of view of the reconstructed 3D US and absence of motion artifacts.     

Left atrial dyssynchrony in veteran endurance athletes with and without paroxysmal atrial fibrillation

Background

Prolonged endurance exercise increase the risk of atrial fibrillation (AF) in men. Functional parameters may help separate physiological from pathological atrial remodeling in athletes. LA mechanical dispersion (LA MD) is associated with AF in the general population, but the associations between prolonged exercise, LA MD and AF are not known.

Purpose

To describe LA MD in veteran athletes with and without paroxysmal AF (pAF) and to investigate LA MD's ability to identify veteran athletes with pAF.

Methods

Two hundred and ninety-three men, skiers with (n = 57) and without (n = 87) pAF, and controls with (n = 61) and without pAF (n = 88) underwent an echocardiographic exam in sinus rhythm. LA reservoir strain (LASr) was measured, and LA MD defined as the standard deviation of time-to-peak strain (SD-TPS).

Results

Skiers (mean age 70.7 ± 6.7 years) reported an average of 40–50 years of endurance exercise. LA volumes were associated with pAF and athletic status (p < .001). SD-TPS was associated with pAF (p < .001) but not athletic status (p = .173). We found no significant trend between years of exercise and SD-TPS in individuals without AF (p = .893). SD-TPS did not add incremental value in identifying athletes with pAF in addition to clinical markers, QRS width, LA volume, and LASr (p = .056).

Conclusion

LA MD was associated with pAF regardless of athletic status but not related to years of endurance exercise, suggesting LA MD could be a promising marker of pathological atrial remodeling in athletes. However, we found no incremental value of LA MD identifying athletes with pAF when LASr was included in the model.