Ventricular interdependence in critically ill patients: from physiology to bedside

Abstract

The review focuses on the mechanism of ventricular interdependence, a frequently encountered phenomena, especially in critically ill patients. It is explained by the anatomy of the heart, with two ventricles sharing a common wall, the septum, and nested in an acutely inextensible envelope, the pericardium. In pathological situation, it results in abnormal movements of the interventricular septum driven by respiration, leading to abnormal filling of one or the other ventricle. Ventricular interdependence has several clinical applications and explains some situations of hemodynamic impairment, especially in situations of cardiac tamponade, severe acute asthma, right ventricular (RV) overload, or more simply, in case of positive pressure ventilation with underlying acute pulmonary hypertension. Ventricular interdependence can be monitored with pulmonary arterial catheter or echocardiography. Knowledge of this phenomena has very concrete clinical applications in the management of filling or in the prevention or treatment of RV overload.

54-year-old Woman with Chest Pain

“…This leads to increased interventricular dependence, the state in which all four chambers must share a fixed intrapericardial volume. 8 During inspiration, decreased intrathoracic pressure and subsequent decreased pulmonary vascular resistance leads to increased filling of right-sided chambers with consequent decreased filling of left chambers in this fixed volume. The opposite occurs during expiration in which left-sided chambers are filled more so than the right-sided chambers due to increased resistance encountered by the right-sided chambers.…”

“…This phenomenon leads to respiratory variation in cardiac output, known as pulsus paradoxus (defined by a decline by 10 mm Hg or greater in systolic blood pressure during inspiration). 8 , 9 …”

Lack of “ventricular interdependence” in constrictive pericarditis and atrial septal defect

“…Ventricular interdependence is seen in cardiac tamponade, CP, acute asthma, right ventricular volume overload, and positive pressure ventilation in the setting of pulmonary artery hypertension. [ 9 ] It is a hallmark of the hemodynamic diagnosis of CP and its differentiation from restrictive cardiomyopathy. [ 3 ] Ventricular interdependence might be absent in patients with ASD and CP is intuitively obvious, but if the clinical diagnosis is not suspected, such an absence might lead to misdiagnosis.…”

Hemodynamic effects of positive end-expiratory pressure

“…Cardiac cavities (in the absence of pericardial effusion) and some great vessels such as superior vena cava or pulmonary arteries are directly submitted to pleural pressure (Ppl) while pulmonary capillaries are submitted to transpulmonary pressure (TPP), which is the distending pressure of the lungs. The pericardium is an acutely inextensible envelope around the heart, which means that every change in one ventricular volume will affect the other through the interventricular septum, a phenomenon called ventricular interdependence [14].…”