BACKGROUND: Preoperative β-blockade has been posited to result in better outcomes for vascular surgery patients by attenuating acute hemodynamic changes associated with stress. However, the incremental effectiveness, if any, of β-blocker usage in blunting heart rate responsiveness for vascular surgery patients who avoid general anesthesia remains unknown. METHODS: We reviewed an existing database and identified 213 consecutive vascular surgery cases from 2005-2011 conducted without general anesthesia (i.e., under monitored anesthesia care or regional anesthesia) at a tertiary care Veterans Administration medical center and categorized patients based on presence or absence of preoperative β-blocker prescription. For this series of patients, with the primary outcome of maximum heart rate during the interval between operating room entry to surgical incision, we examined the association of maximal heart rate and preoperative β-blocker usage by performing crude and multivariate linear regression, adjusting for relevant patient factors. RESULTS: Of 213 eligible cases, 137 were prescribed preoperative β-blockers, and 76 were not. The two groups were comparable across baseline patient factors and intraoperative medication doses. The β-blocker group experienced lower maximal heart rates during the period of evaluation compared to the non-β-blocker group (85 ± 22 bpm vs. 98 ± 36 bpm, respectively; p = 0.002). Adjusted linear regression confirmed a statistically-significant association between lower maximal heart rate and the use of β-blockers (Beta = -11.5; 95% CI [-3.7, -19.3] p = 0.004). CONCLUSIONS: The addition of preoperative β-blockers, even when general anesthesia is avoided, may be beneficial in further attenuating stress-induced hemodynamic changes for vascular surgery patients.

BACKGROUND: Contractility in the borderzone (BZ) after anteroapical myocardial infarction (MI) is depressed. We tested the hypothesis that BZ contractility is also decreased after posterolateral MI. METHODS: Five sheep underwent posterolateral MI. Magnetic resonance imaging (MRI) was performed 2 weeks before and 16 weeks after MI, and left ventricular (LV) volume and regional strain were measured. Finite element (FE) models were constructed, and the systolic material parameter, Tmax, was calculated in the BZ and remote myocardium by minimizing the difference between experimentally measured and calculated LV strain and volume. Sheep were sacrificed 17 weeks after MI, and myocardial muscle fibers were taken from the BZ and remote myocardium. Fibers were chemically demembranated, and isometric developed force, Fmax, was measured at supramaximal [Ca(2+)]. Routine light microscopy was also performed. RESULTS: There was no difference in Tmax in the remote myocardium before and 16 weeks after MI. However, there was a large decrease (63.3%, p = 0.005) in Tmax in the BZ when compared with the remote myocardium 16 weeks after MI. In addition, there was a significant reduction of BZ Fmax for all samples (18.9%, p = 0.0067). Myocyte cross-sectional area increased by 61% (p = 0.021) in the BZ, but there was no increase in fibrosis. CONCLUSIONS: Contractility in the BZ is significantly depressed relative to the remote myocardium after posterolateral MI. The reduction in contractility is due at least in part to a decrease in contractile protein function.