Left bundle branch pacing with and without anodal capture: impact on ventricular activation pattern and acute haemodynamics.

AIMS: Left bundle branch pacing (LBBP) can deliver physiological left ventricular activation, but typically at the cost of delayed right ventricular (RV) activation. Right ventricular activation can be advanced through anodal capture, but there is uncertainty regarding the mechanism by which this is achieved, and it is not known whether this produces haemodynamic benefit. METHODS AND RESULTS: We recruited patients with LBBP leads in whom anodal capture eliminated the terminal R-wave in lead V1. Ventricular activation pattern, timing, and high-precision acute haemodynamic response were studied during LBBP with and without anodal capture. We recruited 21 patients with a mean age of 67 years, of whom 14 were males. We measured electrocardiogram timings and haemodynamics in all patients, and in 16, we also performed non-invasive mapping. Ventricular epicardial propagation maps demonstrated that RV septal myocardial capture, rather than right bundle capture, was the mechanism for earlier RV activation. With anodal capture, QRS duration and total ventricular activation times were shorter (116 ± 12 vs. 129 ± 14 ms, P < 0.01 and 83 ± 18 vs. 90 ± 15 ms, P = 0.01). This required higher outputs (3.6 ± 1.9 vs. 0.6 ± 0.2 V, P < 0.01) but without additional haemodynamic benefit (mean difference -0.2 ± 3.8 mmHg compared with pacing without anodal capture, P = 0.2). CONCLUSION: Left bundle branch pacing with anodal capture advances RV activation by stimulating the RV septal myocardium. However, this requires higher outputs and does not improve acute haemodynamics. Aiming for anodal capture may therefore not be necessary.

Does a change in end-tidal carbon dioxide level predict high altitude mountain sickness?

Background: It is postulated that lack of hypoxic ventilatory response is a predictor for AMS. End-tidal carbon dioxide (ETCO2) is an accurate, noninvasive surrogate measure of ventilation. Objectives: We sought to determine if changes in baseline ETCO2 predicts the development of AMS. Methods: This prospective cohort study took place in three separate high-altitude hiking treks. Subjects included a convenience sample of hikers. Predictor variable was change in ETCO2 levels and outcome variable was AMS. Measurements of ETCO2 levels were obtained at the base and repeated daily at various elevations and the summit of each hike. Concurrently, hikers were scored for AMS by a trained investigator. We utilized correlation coefficients and developed a linear regression model for analysis. Results: 21 subjects in 3 separate hikes participated: 10 ascended to 19,341 ft over 7 days, 6 ascended to 8900 ft in 1 day, and 4 ascended to 11,006 ft in 1 day. Mean age was 40 years, 67% were males, mean daily elevation gain was 2150 ft, and 5 hikers developed AMS. The correlation coefficients for ETCO2 and development of AMS were -0.46 (95%CI -0.33 to -0.57), and -0.77 (95%CI -0.71 to -0.83) for ETCO2 and altitude. ETCO2 predicted the development of symptoms better than the elevation with AUCs of 0.90 (95%CI 0.81-0.99) versus 0.64 (95%CI 0.45-0.83). An ETCO2 measurement of ≤22 mmHg was 100% sensitive and 60% specific for predicting AMS. Conclusions: ETCO2 was strongly correlated with altitude and moderately correlated with AMS and it was a better predictor than altitude.

Comparison of methods for delivering cardiac resynchronization therapy: an acute electrical and haemodynamic within-patient comparison of left bundle branch area, His bundle, and biventricular pacing.

AIMS: Left bundle branch area pacing (LBBAP) is a promising method for delivering cardiac resynchronization therapy (CRT), but its relative physiological effectiveness compared with His bundle pacing (HBP) is unknown. We conducted a within-patient comparison of HBP, LBBAP, and biventricular pacing (BVP). METHODS AND RESULTS: Patients referred for CRT were recruited. We assessed electrical response using non-invasive mapping, and acute haemodynamic response using a high-precision haemodynamic protocol. Nineteen patients were recruited: 14 male, mean LVEF of 30%. Twelve had time for BVP measurements. All three modalities reduced total ventricular activation time (TVAT), (ΔTVATHBP -43 ± 14 ms and ΔTVATLBBAP -35 ± 20 ms vs. ΔTVATBVP -19 ± 30 ms, P = 0.03 and P = 0.1, respectively). HBP produced a significantly greater reduction in TVAT compared with LBBAP in all 19 patients (-46 ± 15 ms, -36 ± 17 ms, P = 0.03). His bundle pacing and LBBAP reduced left ventricular activation time (LVAT) more than BVP (ΔLVATHBP -43 ± 16 ms, P < 0.01 vs. BVP, ΔLVATLBBAP -45 ± 17 ms, P < 0.01 vs. BVP, ΔLVATBVP -13 ± 36 ms), with no difference between HBP and LBBAP (P = 0.65). Acute systolic blood pressure was increased by all three modalities. In the 12 with BVP, greater improvement was seen with HBP and LBBAP (6.4 ± 3.8 mmHg BVP, 8.1 ± 3.8 mmHg HBP, P = 0.02 vs. BVP and 8.4 ± 8.2 mmHg for LBBAP, P = 0.3 vs. BVP), with no difference between HBP and LBBAP (P = 0.8). CONCLUSION: HBP delivered better ventricular resynchronization than LBBAP because right ventricular activation was slower during LBBAP. But LBBAP was not inferior to HBP with respect to LV electrical resynchronization and acute haemodynamic response.

Thromboelastography Use in the Acute Young Trauma Patient: Early Experience of Two Level One Trauma Centers.

BACKGROUND: Thromboelastography (TEG) point-of-care systems allow for analysis of the sum of platelet function, coagulation proteases and inhibitors, and the fibrinolytic system within 30 minutes. This allows a clinician to guide transfusion more precisely with an appropriate type of blood product. Literature has supported that TEG-guided resuscitation had lower mortality compared to standardized 1:1:1 (red blood cells (RBC), fresh-frozen plasma (FFP), and platelets) massive transfusion protocol (MTP) in penetrating trauma patients, but data has been sparse in examining the young trauma patient. METHODS: This was a cross-sectional chart review study performed with patients up to 30 years old seen in two level one trauma centers serving children with active bleeding resulting from trauma from January 1, 2010 to June 26, 2018. TEG use was evaluated in these patients. RESULTS: 258 patients were included in the analysis. 112 (43%) had penetrating trauma and 225 (87%) had polytrauma. MTP was instituted in 176 (69%) patients and 88 (34%) patients who had TEG measured. There were significant correlations between PTT and alpha (r=-0.46; p<0.001), PTT and Kinetics (r=0.53; p<0.001), PTT and maximum amplitude (r=0.449; p<0.001). There were also significant correlations between PT and alpha (r=-0.29; p=0.008), and PT and maximum amplitude (r= -0.27; p=0.013). There was no significant correlation between TEG measures and INR. There were significant associations with requiring surgery within 24 hours 45% vs 61% (p=0.018), receiving TXA 20% vs 59% (p<0.001), and with receiving MTP 62% vs 83% (p=0.001), respectively. CONCLUSIONS: Measurement of TEG was associated with patients receiving TXA, MTP and larger amounts of blood products. Components of TEG correlated with PT and PTT levels. Although there was no association with survival to hospital discharge, patients having TEG measured were more likely to undergo surgery within the first 24 hours of hospital arrival.