Strain Echocardiography to Predict Postoperative Atrial Fibrillation

Abstract

Postoperative atrial fibrillation (POAF) complicates 15% to 40% of cardiovascular surgeries. Its incidence progressively increases with aging, reaching 50% in octogenarians. This arrhythmia is usually transient but it increases the risk of embolic stroke, prolonged hospital stay, and cardiovascular mortality. Though many pathophysiological mechanisms are known, POAF prediction is still a hot topic of discussion. Doppler echocardiogram and, lately, strain echocardiography have shown significant capacity to predict POAF. Alterations in oxidative stress, calcium handling, mitochondrial dysfunction, inflammation, fibrosis, and tissue aging are among the mechanisms that predispose patients to the perfect "atrial storm". Manifestations of these mechanisms have been related to enlarged atria and impaired function, which can be detected prior to surgery. Specific alterations in the atrial reservoir and pump function, as well as atrial dyssynchrony determined by echocardiographic atrial strain, can predict POAF and help to shed light on which patients could benefit from preventive therapy.

Keywords: atrial fibrillation; atrial strain; cardiac surgery; echocardiography; pathophysiology.

Figure 1

“The perfect storm”. Mechanisms involved in the development of atrial structural and electrical remodeling that facilitate the incidence of POAF. APD: action potential duration. Cx: connexin. ROS: reactive oxygen species. NO: nitric oxide. MAO: monoamine oxidase. IL: interleukin. NF-kB: nuclear factor-kappa B.

Figure 2

Summary of mechanisms related to atrial electrical and structural remodeling described in POAF. Ang II: angiotensin II. APD: action potential duration. Cx: connexin. EAD (green arrowheads): early afterdepolarizations. LAD (blue arrows): late afterdepolarizations. NCX: sodium–calcium exchanger. ROS: reactive oxygen species. TNF: tumor necrosis factor. TNFR: tumor necrosis factor receptor. NADPH: nicotinamide adenine dinucleotide phosphate. TGFβ: transforming growth factor-beta. TGFβr: transforming growth factor-beta receptor.

Figure 3

Echocardiographic evaluation of the atria. Anatomical evaluation is based mainly on atrial volume and also on atrioventricular valves disease. Functional evaluation of the atria allows measuring left ventricular end-diastolic pressure (LVEDP) and total atrial conduction time, both related to POAF. Strain echocardiography enables assessment of reservoir, conduit, and longitudinal contractile strain. It also allows intra- and inter-atrial dyssynchrony evaluation. LA: left atria. MV: mitral valve. E/e: relation between early diastolic phase in pulsed Doppler and tissue Doppler. Atrial strain %: Blue line: normal longitudinal atrial strain. Yellow line: impaired atrial longitudinal strain.