Strength-duration curves for left bundle branch area pacing.

BACKGROUND: Despite growing clinical use of left bundle branch pacing (LBBP), data regarding the fundamentals of this pacing modality, including chronaxie and rheobase, are scarce. OBJECTIVE: The purpose of this study was to calculate strength-duration curves with chronaxie and rheobase values for LBBP and left ventricular septal pacing (LVSP), and to analyze battery current drain and presence of selective LBBP at very short pulse duration (PD). METHODS: A group of 141 patients with permanent LBBP were studied. LBBP and LVSP capture thresholds were assessed at 6 different PDs to calculate the strength-duration curves. Battery current drain at these PDs and presence of selective LBBP were determined. For comparison of strength-duration curves between His-bundle pacing (HBP) and LBBP, source data from our previous work based on 127 patients with HBP were obtained. RESULTS: The chronaxies for LBBP and LVSP were very similar (0.38 vs 0.39 ms), and the rheobases were identical (0.27 V). The chronaxie for LBBP was lower than for HBP (0.38 vs 0.53 ms; P <.001), whereas rheobases were similar (0.27 vs 0.26 V). A narrow zone of selective capture was present in 19% and 41% of patients at PD of 0.06 and 0.03 ms, respectively. When pacing with the safety margin of +1 V, the lowest battery current drain was achieved with PD of 0.2 ms. CONCLUSION: The obtained strength-duration curves for LBBP and LVSP provide insights to optimal programming of left bundle branch area pacing devices with regard to PD, voltage amplitude, battery longevity, and selective capture.

Left bundle branch area pacing improves right ventricular function and synchrony.

BACKGROUND: The impact of left bundle branch area pacing (LBBAP) on right ventricular (RV) function and tricuspid regurgitation (TR) remains unclear. OBJECTIVE: We aimed to assess the long-term effects of LBBAP on RV performance and on TR. METHODS: RV function was evaluated using RV free wall strain, tricuspid annular plane systolic excursion, fractional area changing, and systolic velocity of the lateral tricuspid annulus. The presence of reverse septal flash (RSF) and basal bulge (BB) was used to assess RV motion pattern. The distance between the lead entry site on the interventricular septum and the septal leaflet of the tricuspid annulus (lead-TV distance) was measured. RESULTS: The analysis included 122 subjects [62 men (50.8%); mean age 76.5 ± 11.4 years] with a median follow-up of 21 months (18-24.5 months). During follow-up, RV free wall strain improved significantly (15.2 ± 5.8 vs 16.4 ± 5.5; P < .001) while tricuspid annular plane systolic excursion, systolic, and fractional area changing remained unchanged. Left ventricular ejection fraction was an independent predictor of improved RV function (B = 3.51; 95% confidence interval 1.39-8.9; P = .01). With LBBAP, RSF disappeared in 22 of 23 patients (96%) and BB in 15 of 22 patients (68%) in whom RSF and BB were present at baseline, respectively. RV function improvement was significantly higher when RSF was present at baseline (14 patients vs 11 patients; P = .02). At follow-up, no significant deterioration in TR occurred for the overall group. However, a lead-TV distance of <24.5 mm was associated with TR progression. CONCLUSION: LBBAP has a favorable impact on RV function. A basal LBBAP position is associated with worsening TR.

The sodium-chloride difference: A marker of prognosis in patients with acute myocardial infarction.

BACKGROUND: The difference between serum sodium and chloride ion concentrations (SCD) may be considered as a surrogate of a strong ion difference and may help to identify patients with a worse prognosis. We aimed to assess SCD as an early prognostic marker among patients with myocardial infarction. METHODS: Data of 594 consecutive patients with acute myocardial infarction treated with PCI (44.9% STEMI patients; 70.7% males) was analysed for SCD in relation to their 30-day mortality. A restricted cubic spline regression model was used to study the relationship between mortality and SCD. Cox regression models were used to assess the association between SCD and the mortality risk. RESULTS: Patients with Killip class ≥3 had lower SCD values in comparison to patients with Killip class ≤2: (32.0 [30.0-34.0] vs. 33.0 [31.0-36.0], p = .006). The overall 30-day mortality was 7.7% (n = 46). There was a significant difference in SCD values between survivors and non-survivors groups of patients (median (IQR): (33.0 [31.0-36.0] vs. 31.5 [28.0-34.0] (mmol/L), p = .002). The restricted cubic splines model confirmed a non-linear association between SCD and mortality. Patients with SCD <30 mmol/L (in comparison to SCD ≥30 mmol/L) had an increased mortality risk (unadjusted HR 2.92, 95% CI 1.59-5.36, p = .001; and an adjusted HR 2.30, 95% CI 1.02-5.19, p = .04). CONCLUSIONS: Low SCD on admission is associated with an increased risk of 30-day mortality in patients with acute myocardial infarction treated with PCI and may serve as a useful prognostic marker for these patients.

Angiotensin-converting enzyme inhibitors and angiotensin-II-receptor antagonists modulate sodium handling based on endogenous lithium clearance.

BACKGROUND: Numerous studies based on assessment of lithium clearance demonstrated higher sodium reabsorption in renal proximal tubules in individuals with hypertension, overweight, obesity, metabolic syndrome, or diabetes. AIMS: We aimed to assess the influence of angiotensin-converting enzyme inhibitors (ACE-I) or angiotensin-II-receptor antagonists (ARB) treatment on sodium handling. METHODS: In a sample of 351Caucasian subjects without diuretic treatment with prevailing sodium consumption, we studied associations between renal sodium reabsorption in proximal (FPRNa) and distal (FDRNa) tubules assessed by endogenous lithium clearance and daily sodium intake measured by 24-hour excretion of sodium (UNaV), in the context of obesity and long-term treatment with ACE-I or ARB. RESULTS: In the entire study population, we found a strong negative association between FPRNa and ACE-I/ARB treatment (b = -19.5; SE = 4.9; P <0.001). Subjects with FPRNa above the median value showed a significant adverse association between FPRNa and age (b = -0.06; SE = 0.02; P = 0.003), with no association with ACE-I/ARB treatment (P = 0.68). In contrast, in subjects with FPRNa below the median value, we found a strongly significant adverse relationship between FPRNa and ACE-I/ARB treatment (b = -30.4; SE = 8.60; P <0.001), with no association with age (P = 0.32). CONCLUSIONS: ACE-I/ARB long-term treatment modulates FPRNa in the group with lower reabsorption, but not in that with higher than median value for the entire study population.