Heterogeneous Cardiovascular Responses to Acute Mean Arterial Pressure Augmentation in Septic Shock: The Role of Ventriculo-Arterial Coupling

<title>Abstract</title> <p>Background In septic shock, vasopressor-induced mean arterial pressure (MAP) augmentation is commonly used in septic shock to restore tissue perfusion, but patients may exhibit divergent cardiovascular responses despite achieving similar arterial pressure targets. We hypothesized that this heterogeneity reflects differences in ventricular adaptation to the acute increase in arterial load, as assessed by ventriculo-arterial (VA) coupling. Methods We conducted a prospective physiological observational study in mechanically ventilated adults with fluid-resuscitated septic shock undergoing transient MAP augmentation from approximately 65 to 85 mmHg. MAP was increased by norepinephrine dose escalation or by adding vasopressin, according to clinical judgment. Comprehensive transthoracic echocardiography was performed immediately before and after MAP augmentation. Patients were classified a priori according to relative changes in cardiac output (CO): flow recruitment (&gt; 15% increase), stable flow (− 15% to + 15%), or flow deterioration (&gt; 15% decrease). Changes in effective arterial elastance (Ea), end-systolic elastance (Ees), VA coupling (Ea/Ees), stroke volume, left ventricular ejection fraction (LVEF), myocardial performance index (MPI), isovolumetric contraction time (IVCT), and perfusion variables were analyzed. Results Thirty-two patients were included. Despite comparable increases in MAP, cardiovascular responses were heterogeneous: 10 patients (31%) exhibited flow recruitment, 17 (53%) maintained stable flow, and 5 (16%) developed flow deterioration. Patients with flow deterioration showed a greater increase in Ea and a smaller increase in Ees, resulting in worsening VA coupling (ΔEa/Ees + 0.22 [IQR 0.06–0.43]), whereas VA coupling remained stable or improved in patients with preserved or increased flow (p = 0.031). Flow deterioration was accompanied by reduced stroke volume, decreased LVEF, prolonged IVCT, and worsening MPI. Changes in VA coupling correlated with changes in IVCT (ρ = 0.790, p &lt; 0.0001), MPI (ρ = 0.599, p = 0.0003), LVEF (ρ=−0.431, p = 0.014), and stroke volume (ρ=−0.418, p = 0.017). Tissue perfusion markers changed less consistently across response groups. Conclusions Acute MAP augmentation elicits heterogeneous cardiovascular responses in fluid-resuscitated septic shock. Flow deterioration is characterized by impaired ventricular adaptation to increased arterial load, reflected by worsening VA coupling and systolic performance.</p>