Heart rate variability measures poorly predict atrial fibrillation after off-pump coronary artery bypass grafting.

STUDY OBJECTIVE: To investigate associations of heart rate variability (HRV) measurements with postoperative atrial fibrillation (AF) in patients undergoing off-pump coronary surgery. DESIGN: Prospective, observational, exploratory study. SETTING: Large university-affiliated community medical center. PATIENTS: 50 patients undergoing off-pump coronary artery bypass grafting (CABG). INTERVENTIONS: Preoperative recording of electrocardiograms (ECGs) with subsequent off-line HRV analysis. Monitored ECG telemetry for 5 days after operation. MEASUREMENTS: Frequency and time domain analyses, and additional non-linear HRV determinations. Multivariate regression analysis of predictors of postoperative AF. MAIN RESULTS: AF occurred in 23 (46%) patients. Only the low to high-frequency ratio was associated with AF (2.35 ± 1.8 v. 4.57 ± 5.0 for patients without AF, P < 0.05). CONCLUSIONS: The off-pump approach does not protect against AF, and nonlinear HRV analyses provide little value in predicting AF after off-pump CABG.

Prophylactic glycopyrrolate prevents bradycardia after spinal anesthesia for Cesarean section: a randomized, double-blinded, placebo-controlled prospective trial with heart rate variability correlation.

STUDY OBJECTIVE: To determine if prophylactic glycopyrrolate prevents bradycardia after spinal anesthesia. DESIGN: Prospective, randomized, double-blinded, placebo-controlled study. SETTING: Large university-affiliated community hospital. PATIENTS: 81 consecutive term parturients (not in active labor) who were scheduled for elective Cesarean section. INTERVENTIONS: Parturients received 1.0 to 1.5 L of intravenous Ringer's lactate and either glycopyrrolate 0.4 mg or an equal volume of saline, with caregivers blinded to the immediate sequelae of study drug. Each patient received intrathecal bupivacaine (12 to 14 mg) with morphine sulfate (0.1 to 0.2 mg). MEASUREMENTS: Continuous heart rate (HR) and blood pressure monitoring occurred for 20 minutes, with the minimum HR recorded for each 5-minute epoch. Heart rates < 60 beats per minute defined bradycardia. Heart rate variability (HRV) analysis occurred offline. MAIN RESULTS: None of 34 patients administered glycopyrrolate and 6 of 35 (17%) patients receiving saline experienced bradycardia (P = 0.02476). Time domain, frequency domain, and nonlinear and embedded spectrum entropy analyses all reflected the decrease in HRV accompanying administration of glycopyrrolate. CONCLUSION: Bradycardia after spinal anesthesia occurs commonly. Prophylactic glycopyrrolate may prevent the bradycardia, but not necessarily the hypotension.

Nonlinear heart rate variability analysis may predict atrial fibrillation after coronary artery bypass grafting.

BACKGROUND: Heart rate variability might predict arrhythmias after coronary artery bypass grafting. METHODS: Off-line processing of 10-min electrocardiogram recordings of consecutive patients provided R-R intervals for time domain, frequency domain, Poincaré, and point correlation analyses and subsequent association with postoperative atrial fibrillation by stepwise multivariate logistic regression. RESULTS: Of 88 patients who met entry criteria, 13 developed atrial fibrillation. Peak point correlation dimension (odds ratio 3.985/unit, P = 0.0096) and age (odds ratio 1.144/yr, P = 0.0019) were independently associated with atrial fibrillation (c-statistic = 0.839). CONCLUSIONS: Further study should confirm the ability of peak point correlation dimension to predict atrial fibrillation after coronary artery surgery with cardiopulmonary bypass.

Using heart rate variability to stratify risk of obstetric patients undergoing spinal anesthesia.

In this study, we evaluated whether point correlation dimension (PD2), a measure of heart rate variability, can predict hypotension accompanying spinal anesthesia for cesarean delivery. After the administration of spinal anesthesia with bupivacaine, hypotension was defined as systolic blood pressure