Bradyarrhythmias and Physiologic Pacing in the ICU.

Bradyarrhythmias represent a common pathology in the intensive care unit (ICU) with etiologies of varying severity. Treatment has often been focused on correcting underlying causes and may require pacing for urgent hemodynamic support. In recent years, there has been interest in physiologic pacing modalities which avoid the dyssynchrony from right ventricular (RV) only pacing. Cardiac resynchronization therapy (CRT) through biventricular pacing is a well-established device-based electrical therapy in patients with wide QRS and heart failure. Recently, it has been shown that biventricular pacing may also be pursued for hemodynamic rescue in the ICU setting. Efforts to re-engage the conduction system with His bundle pacing or further downstream have also emerged as alternative means to deliver resynchronization, with early applications in the ICU now being reported. The goal of the review is to examine bradyarrhythmia causes and management in the ICU as well as investigate new approaches in physiologic pacing and their potential roles in critically ill patients.

Concomitant Lower-Extremity Deep Vein Thrombosis in Patients With Pulmonary Embolism Undergoing Catheter-Directed Therapy.

BACKGROUND: Deep vein thrombosis (DVT) is often seen in patients with acute pulmonary embolism (PE). Risk stratification of PE patients is useful in predicting mortality risk and hospital course. However, rates or predictors of DVT or proximal DVT (popliteal, femoral, common femoral, or iliac thrombosis) have not been studied in the highest-risk patients who receive catheter-directed therapy (CDT) for their PE. A single-center retrospective analysis of patients referred for CDT for confirmed PE was conducted to evaluate rates and predictors of DVT or proximal DVT and the impact on short-term outcomes. In 137 consecutive patients undergoing CDT for PE with available lower-extremity ultrasound, the rates of DVT and proximal DVT in PE patients receiving CDT were 76.6% and 65.0%, respectively. Rates of DVT (P=.68) and proximal DVT (P=.72) did not differ between high-risk or non-high risk PE patients. The only significant factor associated with presence of concomitant DVT was previous DVT (P=.045). The presence of a concomitant DVT or proximal DVT was not associated with an increase in all-cause mortality or hospitalization at 30 days or 1 year compared with an absence of concomitant DVT or proximal DVT. The results of this study suggest that patients with PE clinically requiring CDT have high rates of concomitant DVT and proximal DVT, prior DVT predicts concomitant DVT, and the presence of DVT is not associated with additional risk in this already high-risk population of patients.

Impact of physiological pacing on functional mitral regurgitation in systolic dysfunction: Initial echocardiographic remodeling findings after His bundle pacing.

BACKGROUND: Although His bundle pacing (HBP) has been shown to improve left ventricular ejection fraction (LVEF), its impact on mitral regurgitation (MR) remains uncertain. OBJECTIVES: The aim of this study was to evaluate change in functional MR after HBP in patients with left ventricular (LV) systolic dysfunction. METHODS: Paired echocardiograms were retrospectively assessed in patients with reduced LVEF (<50%) undergoing HBP for pacing or resynchronization. The primary outcomes assessed were change in MR, LVEF, LV volumes, and valve geometry pre- and post-HBP. MR reduction was characterized as a decline in ≥1 MR grade post-HBP in patients with ≥grade 3 MR at baseline. RESULTS: Thirty patients were analyzed: age 68 ± 15 years, 73% male, LVEF 32% ± 10%, 38% coronary artery disease, 33% history of atrial fibrillation. Baseline QRS was 162 ± 31 ms: 33% left bundle branch block, 37% right bundle branch block, 17% paced, and 13% narrow QRS. Significant reductions in LV end-systolic volume (122 mL [73-152 mL] to 89 mL [71-122 mL], P = .006) and increase in LV ejection fraction (31% [25%-37%] to 39% [30%-49%], P < .001) were observed after HBP. Ten patients had grade 3 or 4 MR at baseline, with reduction in MR observed in 7. In patients with at least grade 3 MR at baseline, reduction in LV volumes, improved mitral valve geometry, and greater LV contractility were associated with MR reduction. Greater reduction in paced QRS width was present in MR responders compared to non-MR responders (-40% vs -25%, P = .04). CONCLUSIONS: In this initial detailed echocardiographic analysis in patients with LV systolic dysfunction, HBP reduced functional MR through favorable ventricular remodeling.